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Investigation summary

What happened

On 29 May 2025, a Cessna 310R, registered VH-NXA and operated by Marthakal Yolngu Airline, was conducting a non-scheduled passenger air transport flight from Darwin to Lake Evella, Northern Territory. On board were the pilot and 4 passengers. 

During the approach at Lake Evella Aerodrome, recorded data indicated that the aircraft touched down just prior to halfway along the runway. The pilot subsequently applied braking, but the aircraft did not decelerate as expected. This resulted in a runway excursion and the aircraft subsequently collided with a perimeter fence which substantially damaged the left wing. The pilot and 4 passengers were uninjured.

What the ATSB found

The ATSB found that the pilot conducted the approach above the standard profile and crossed the threshold above the normal approach speed. This resulted in the aircraft floating during the landing flare for a prolonged period in ground effect, and a landing beyond the planned touchdown point. After the aircraft touched down, the pilot subsequently commenced braking about halfway along the runway. The long landing reduced the available distance to decelerate on the runway.  

At the aircraft’s landing weight, the remaining runway length should have provided sufficient stopping distance, but degraded braking capacity meant the aircraft could not be stopped before the runway end and it subsequently departed the runway.

During a scheduled maintenance event prior to the occurrence, a licensed aircraft maintenance engineer believed an apprentice had replaced the main-wheel brake pads. An inspection after the occurrence found that the right brake reservoir was empty and that the right pads were worn beyond limits, which reduced braking capacity on that side.

The ATSB also identified that the operator’s procedures allowed the use of self-reported passenger weights without additional allowances, and that the electronic weight and balance system had been configured with higher maximum weights applicable to a modification not fitted to this aircraft. In combination with calculation errors on the day, this resulted in the aircraft being operated above the maximum permitted ramp and take‑off weights.

What has been done as result

Marthakal Yolngu Airline advised that all references to the use of self-reported passenger weights for the purposes of weight and balance calculations will be removed in the next amendment of the operations manual. 

The operator also advised that the electronic weight and balance system will be amended to reflect the correct maximum weights for VH-NXA prior to its return to service. 

The safety manager briefed company personnel about the proposed changes and advised existing pilots that actual weights for passengers must be used for all flights. 

The ATSB will monitor these safety actions until the proposed changes to the operations manual and weight and balance system have been formally implemented. 

D & T Aircraft Engineering advised that, following the occurrence, a debrief with maintenance personnel highlighted the importance of increased vigilance during inspections conducted after maintenance tasks, and that the organisation also identified opportunities to improve internal processes following similar occurrences.

Safety message

Factors such as additional airspeed over the threshold can result in a landing beyond the intended touchdown point, increasing the risk of a runway overrun excursion. While adherence to a pre-determined stabilised approach criteria can effectively mitigate such risks, pilots should always exercise vigilance and ensure the aircraft is flown within the assumed conditions used to calculate landing performance.     

Pilots are therefore encouraged to continue to actively monitor the flight path using cockpit instrumentation and external visual cues until a safe landing is assured. This should include identifying and nominating an appropriate touchdown point on the runway to ensure a go‑around can be executed if a touchdown beyond this point is likely to occur. 

Additionally, maintenance organisations should ensure that effective systems are in place to disseminate important information to all maintenance personnel, so that emerging defects are identified and rectified before they affect flight operations.

The occurrence

Pre-flight preparation 

On the morning of 29 May 2025, a Cessna C310R, registered VH-NXA and operated by Marthakal Yolngu Airline, was being prepared for a non-scheduled passenger air transport flight from Darwin to Lake Evella, Northern Territory.

When the pilot arrived at the airport, they observed a licensed aircraft maintenance engineer (LAME) and their apprentice performing maintenance on the aircraft braking system. During this period the pilot prepared their flight plan and when they returned to the aircraft, the LAME and the apprentice had completed the maintenance.    

The pilot, who was operating their first flight as pilot in command of a multi-engine aircraft, commenced their pre-flight checks. Due to the recent work on the braking system, they taxied to an aircraft bay to conduct a static engine run-up.[1]

With both engines at 1,700 RPM, they recalled that the aircraft moved forward slightly with the brakes applied. They physically increased their braking pressure, after which, the aircraft remained stationary. After completing the run-ups, the pilot taxied back to the terminal where the passengers were waiting. At this time, they also discussed the brakes with another C310 pilot who advised them that quite a lot of brake pressure was required during run-ups. 

The pilot reported feeling rushed, and elected to use the self-reported passenger and baggage weights prior to boarding for weight and balance calculations, which were recorded on the manifest. These weights were entered into an electronic weight and balance system, which indicated that the planned load complied with the aircraft weight and balance limitations. The passengers were then taken to the aircraft where the pilot conducted a safety briefing before they boarded. 

Occurrence flight 

At 0857 local time, VH-NXA departed from Darwin Airport with the pilot and 4 passengers on board for Lake Evella (Figure 1). When approaching the Lake Evella Aerodrome, the pilot reported becoming visual with runway 08 at about 15 NM (28 km) and tracked for a straight in approach. At 1051, the aircraft was established on final approach for runway 08.

Figure 1: VH-NXA flight planned track

Source: Google Earth, annotated by the ATSB

The pilot recalled that there was a south-easterly wind between 8–10 kt for the approach, with a right crosswind component. Another pilot, who arrived at Lake Evella about 3 minutes after VH-NXA, recalled the wind was from an easterly direction at about 10 kt. 

The pilot of VH-NXA recalled that the approach ‘seemed stable,’ (see Stabilised approach criteria) and stated that they generally used the runway threshold as their aiming point. They estimated crossing the threshold at their calculated approach speed of 90 kt or ‘just above.’ 

A navigational application (OzRunways) [2] was installed on a tablet computer and an Android phone on board the aircraft and broadcast flight data (see Recorded information). The OzRunways data taken from the Android phone, overlaid on a Google Earth image (Figure 2), showed the aircraft crossing the runway threshold at a height of 55 ft with a ground speed of 94 kt (Figure 2, A). The runway in Lake Evella was not equipped with visual slope guidance and the pilot relied on their visual assessment of ‘how the runway should look at certain height.’

Figure 2: VH-NXA ground speed at key points in landing sequence

Source: Google Earth, annotated by the ATSB

The pilot and the passenger seated directly behind them estimated that the aircraft touched down approximately 200 m past the threshold. ATSB analysis of recorded data indicated touchdown at 1051:29 (the corrected altitude of the aircraft matched the terrain elevation of runway 08), which was 402 m past the threshold (Figure 2, B). The passenger seated in the front row beside the pilot recalled passing the taxiway immediately after touchdown (Figure 2, C).

Another pilot on the ground standing at the apron who witnessed the landing reported observing VH-NXA a few feet above the ground in the ‘flaring attitude’ about a third of the distance along the runway. They also recalled that the aircraft was travelling faster than what they thought was normal and landed just beyond the taxiway (Figure 2, C). 

The pilot reported that after touchdown, they applied the brakes passing the apron area about halfway along the runway (Figure 2, C). At that point, they reported that the aircraft did not appear to be slowing as expected and the passenger in the last row recalled the aircraft passing the apron ‘very fast’. 

The pilot recalled increasing their braking pressure and when they saw the end of the runway approaching, they shut both engines down by selecting the mixture controls to idle cut-off. The pilot then elected to steer the aircraft to the left of the runway centreline to increase the runway distance for the deceleration required.

The aircraft departed the left side of the runway, 118 m from the runway end (Figure 2, D) (Figure 3, inset left), while the passenger seated beside the pilot verbally prompted the passengers to ‘brace.’ Recorded data indicated the aircraft was travelling at 45 kt at this point. The left wing subsequently collided with a fencepost (Figure 2, E)  (Figure 3, inset right) located 193 m from the point the aircraft departed the runway. 

Figure 3: VH-NXA ground roll following runway excursion 

Source: Marthakal Yolngu Airline, annotated by the ATSB

Following the collision, the aircraft came to a stop and the pilot and passengers disembarked through the right cabin door. There were no injuries to the pilot or passengers, however the aircraft sustained substantial damage (see Post-accident inspection).

Context

Pilot information

The pilot held a Commercial Pilot Licence (Aeroplane) issued in 2021 and a class 1 aviation medical certificate. They also held a multi-engine aircraft class rating, which was issued in 2022 and renewed with a flight training organisation on 24 May 2025.

The pilot had accumulated 1,066 hours of total aeronautical experience, which included 71 hours of multi-engine time accumulated under the supervision of an instructor. 

They reported they had flown about 70 hours in the last 90 days, including a total of 11.7 hours on the Cessna C310R, which was conducted during the course of their training. 

The pilot’s training was conducted by a flight training organisation (FTO) in Darwin, on behalf of Marthakal Yolngu Airline. FTO training records detailed that the pilot commenced line training for the C310R on 15 May 2025. 

This line training took place over 9.8 flight hours, after which they were assessed as proficient by a flight examiner during a combined line check and operator proficiency check for the C310R on 24 May.

The pilot had not operated the C310R to Lake Evella Aerodrome during the course of their training and had not operated there in any aircraft type prior to the occurrence. They reported sleeping about 8 hours the night before the occurrence and had been awake for about 7 hours at the time of the occurrence and feeling ‘fully alert.’

Aircraft information 

The Cessna 310R is a twin-engine, low-wing (with a wingspan of 11.3 m), 6-seat, unpressurised aircraft equipped with retractable landing gear and powered by 2 Continental IO-520 piston engines. VH-NXA was manufactured in the United States in 1978 and first registered in Australia in 1989. A maintenance organisation located in Darwin became the registration holder on 4 March 2020.

Braking system

Section 7 of the Cessna 310R Pilots operating handbook (POH) contained the following description of the braking system: 

The airplane is provided with an independent hydraulically actuated brake system for each main wheel. A hydraulic master cylinder is attached to each pilot’s rudder pedal. Hydraulic lines and hoses are routed from each master cylinder to the wheel cylinder on each brake assembly. No manual adjustment is necessary on these brakes. The brakes can be operated from either pilot’s or co-pilot’s pedals. 

Meteorological information

The graphical area forecast and the applicable grid point wind and temperature forecast for the flight indicated:

• prevailing visibility greater than 10 km
• scattered cloud[3] with bases 1,500 ft above mean sea level (AMSL)
• isolated areas of smoke reducing visibility to 5,000 m
• isolated rain showers and thunderstorms reducing visibility to 2,000 m and 1,000 m respectively, and broken cloud with bases 800 ft above AMSL
• moderate turbulence below 4,000 ft in thermals and dust/sand whirls (dust devils)
• wind 130° at 21 kt and temperature of 24°C at 1,000 ft above AMSL.

Aerodrome information

Lake Evella Aerodrome (YLEV) is situated at an elevation of 278 ft AMSL and comprised of a single sealed runway, 08/26, measuring 1,065 m in length and 18 m in width and was sloped 0.5% up toward the east. The aerodrome is uncontrolled and operated on a dedicated CTAF,[4] and is subject to animal hazards.

Maintenance information

Aircraft maintenance manual 

The Cessna 310R Aircraft maintenance manual (AMM) contained a troubleshooting guide to assist maintenance personnel to rectify defects relating to systems fitted to the aircraft. The section that covered the wheels and brakes included the following information (Table 1):

Table 1: Cessna 310R maintenance manual troubleshooting

The AMM also described the brake wear limits on the C310R, which included:

Check back plate and pressure plate linings for wear. If worn to a thickness of 0.125 to 0.100 inch, the linings should be replaced.

Scheduled maintenance 

The aircraft was flown to Darwin on 15 February 2025, where the authorising licensed aircraft maintenance engineer (LAME) planned to conduct a corrosion inspection at their maintenance facility. The LAME also performed a ‘check 1’ inspection, which they stated was the equivalent of a 100-hour inspection.

During the inspections, additional maintenance was conducted due to leaking brake callipers, which was common to the brakes on the C310 according to the LAME. This involved the removal, bleeding, resealing and refitting of both callipers and was performed by an apprentice. It was also the LAME’s expectation that the brake pads would be replaced during this maintenance task because this was routine practice, although not in the procedure. 

As part of the 100-hour inspection, the LAME performed an engine run-up and observed the aircraft did not hold under brakes at this time. Believing that they had been replaced, they believed that the new brake pads needed to be bedded or burnt in. The AMM stated ‘brake burn in is required to minimize glazing of the friction surfaces’ when new brakes are installed. They subsequently completed the engine run up on one engine at a time, which allowed the aircraft to remain stationary. 

Following the completion of the inspections and associated maintenance tasks, including the additional work carried out on the brakes, the LAME certified the aircraft maintenance logbook on 26 May 2025.  

The authorising LAME later stated that new brake pads should have been installed before the callipers were refitted to the landing gear, however they did not verify that this had occurred. They reported that the brake pads were last changed on 15 December 2023 and had 494 landings prior to the occurrence. 

Pre-departure maintenance

The aircraft underwent a post‑maintenance verification flight the day prior to the accident flight, with a flight instructor and the occurrence pilot as an observer. After the flight, the instructor advised the LAME by text message that the brakes felt ‘spongy.’

On the morning of 29 May, prior to the accident flight, the LAME checked the aircraft brakes, reporting that they were acceptable, even though the brake pedal travel felt more than usual. The decision was made to bleed the brakes to remove any air or water in the brake lines and top up the brake fluid. With assistance from an apprentice during this process, the LAME reported that hydraulic fluid spilled onto the right tyre and was subsequently wiped down. The aircraft was then released back to service. 

Post-accident inspection

Following the occurrence, the LAME inspected the aircraft at Lake Evella Aerodrome on 18 June 2025 and documented the aircraft damage. The aircraft had sustained significant damage to the left wing (Figure 4), which separated from the fuselage outboard of the left engine nacelle. The pitot tube, right tip tank, propeller and nose gear door were also damaged following the runway excursion. 

Figure 4: VH-NXA damaged left wing

Source: Aircraft maintainer, annotated by the ATSB

The LAME found that the right brake reservoir was empty, with evidence of hydraulic fluid leakage on the right tyre, however stated that the right brake disc was serviceable. 

They identified that the right brake pads were ‘heavily worn.’ Images supplied by the LAME also indicated the presence of hydraulic brake fluid, originating from the brake piston adjacent to the brake line (Figure 5). They also indicated that the hydraulic fluid on the tyre may have been from fluid spilling when the brakes were topped up on the morning of the occurrence flight. 

Figure 5: VH-NXA right hand brake components and hydraulic brake fluid

Source: Aircraft maintainer, annotated by the ATSB

No defects were identified on the left brake system and the right brake calliper was removed and tested in Darwin by the LAME. The right brake calliper was bolted onto a brake disc with sufficient pressure applied to prevent calliper movement. After 13 days, sufficient hydraulic fluid had leaked, which allowed the calliper to be moved in relation to the brake disc. The LAME subsequently disassembled the right brake calliper and identified a ‘very small’ hydraulic fluid leak, which they did not consider was the cause of the fluid loss during the occurrence. 

Operational information

Weight and balance

The operator’s standard operating procedures (SOP) stated that during the conduct of air transport operations, prior to each sector, the pilot in command must complete an aircraft load and trim sheet. 

An operator‑approved electronic load sheet was available to pilots for the purpose of completing weight and balance calculations in accordance with the POH weight and balance limitations.

The operator’s Cessna 310R Flight crew operating manual (FCOM) included the following statement regarding the possible modification of company operated aircraft:

The Company operates C310R aircraft in several possible modification states, which may affect limiting weight.

The only modification listed in the FCOM that affected the weight limitations for VH-NXA was the fitment of a vortex generator (VG)[6] kit. The FCOM also contained information relating to the fitment of the VG kit including increased weight limitations, changes to various airspeeds and stated:

If less than 84 vortex generators are in place or undamaged, the aircraft must be operated in accordance with the original AFM performance data (ie nil VGs).

Electronic weight and balance system

The electronic weight and balance system was developed by a third party to calculate the weight and balance for each flight. In the system, each aircraft was configured with a weight and moment arm[7] when empty. 

The pilot would enter the pilot and passengers’ weights, their seating positions and fuel to calculate both the weight and centre of gravity of the aircraft at take-off and landing. The system was designed to alert the user if any weight and balance limitations were exceeded. 

For VH-NXA, the electronic weight and balance system incorporated an increase in weight in accordance with a supplemental type certificate number for a C310R VG modification. However, the maintenance organisation that owned and maintained the aircraft stated that VH-NXA had not been fitted with the VG modification, and they were not aware of any modifications that increased the standard maximum permitted weights as prescribed in the POH. 

 As a result, the weight and balance system contained the following increases to the standard POH weight limitations which were not applicable to the aircraft (Table 2):

Table 2: Cessna 310R maximum weights

Passenger-declared weights 

The operator’s SOP stated that for the purposes of calculating the aircraft’s weight and balance, ‘passenger weights must be actual, or self-reported.’ Following the occurrence, a passenger reported that their body and baggage weights were requested without the use of a calibrated scale. The pilot did not indicate that any adjustments of additional amounts were applied to the passenger reported weights. 

The CASA multi-part AC 121-05, AC 133-04 and AC 135-08 – Passenger crew and baggage weights, described acceptable weight calculation methods that could be defined in operating procedures. The circular stated that:

The use of actual weights is the most accurate method of maximising payload capacity. Appropriately calibrated weighing scales should be used. Actual weighing is more commonly used by Part 133 [helicopter passenger transport] and 135 [smaller aeroplane passenger transport] operators. This is, in part, due to the smaller number of passengers being carried, which makes this option less disruptive than it is for Part 121 [larger aeroplane passenger operations] operators. 

Operators should have procedures to identify when passenger-declared weights are not appropriate, such as when operating close to limitations. Under these circumstances, the use of actual weights may be required to ensure limitations are not exceeded. 

Passenger-declared weights have inherent inaccuracies as passengers may not know their actual weight, especially when fully dressed. An adjustment allowance should be added to any passenger-declared weight, as a factor or a fixed additional amount.

Weight and balance calculations

Following a review of documentation provided by the operator and pilot, the ATSB identified several discrepancies contained in the operational documentation from the day of the occurrence. 

The passenger and baggage weights recorded in the manifest by the pilot indicated a combined weight of 387 kg. However, the corresponding load sheet indicated a combined passenger and baggage weight of 337 kg (excluding the pilot). 

Additionally, the fuel plan prepared by the pilot indicated a total fuel figure of 441 kg. By comparison, the fuel figure on the load sheet was recorded as 432 kg.    

Due to the identification of the combined discrepancy of 59 kg, the ATSB recalculated the aircraft’s weight and balance for the flight. This identified the following updated weights and exceedances (Table 3) prescribed in the POH for aircraft not fitted with a VG kit.

Table 3: VH-NXA calculated weights and exceedances

Landing performance calculations

The operator’s SOPs stated that company aircraft are subject to the requirements of Civil Aviation Safety Regulations Part 135 Manual of Standards (MOS) with respect to take-off and landing performance requirements. Chapter 10 of the Part 135 MOS stipulated ‘that the aeroplane crosses the runway threshold at a height of 50 ft’ unless an approved short landing operation was being conducted. Additionally for landing, the FCOM stated that the reference landing approach speed (V_ref)[8] should be achieved at 50 ft above the landing surface.

For aeroplanes, take-off and landing distance calculations to determine maximum take‑off weight or the maximum landing weight are achieved through a manual calculation using the limitations given in the POH for the specific aircraft type, taking into account: 

• environmental conditions
• runway length.

The FCOM also required pilots to apply landing distance factoring of 1.20 for all calculations. The pilot stated they had calculated their landing performance based on the aircraft’s maximum landing weight and calculated a factored landing distance of 680 m on the flight plan with a V_ref of 90 kt for their landing at Lake Evella. 

Calculations using the ATSB recalculated landing weight and the estimated ambient conditions at the time of the occurrence determined that the required landing distance (with the 1.20 factoring) with a 50 ft threshold crossing height was 659 m. This figure included a landing ground roll distance of 195 m and a corresponding V_ref of 91 kt.

Stabilised approach criteria 

The SOPs stated that, ‘unless the aircraft meets stabilised approach criteria at the specified altitude, a missed approach must be executed.’

A stabilised approach was described in the SOPs as an approach to land that met a number of criteria by 300 ft above the runway during a visual approach. These included the following:

• the aircraft is on the correct flight path

• only small changes in heading & pitch are required to maintain the correct flight path

• the aircraft speed is V_ref to V_ref +20 kt

• sink rate is not greater than 1,000 fpm or pre-briefed limits. 

Recorded information

The pilot used a flight planning application (OzRunways) on an iPad and an Android phone for en route flight planning and navigation. The flight planning software provider was an approved source of electronic aeronautical charts, however the application could not be used as a primary means of GPS-based navigation as the iPad and Android phone GPS did not meet certification for aviation use. The pilot reported that the iPad was placed on the floor for the approach while the Android phone was in their chest pocket. By examining the combination of groundspeed and derived deceleration data, in addition to the best direct line of sight to satellites, it was assessed that the Android data had the highest positional accuracy.

The recorded data had limitations due to an altitude resolution of 100 ft, while filtering and adjustments were also applied to smooth the data and are known to affect the accuracy of small sections. Additionally, the altitude data of VH-NXA was corrected to match the terrain elevation during the landing ground roll (Figure 6).

Based upon the operator’s stabilised approach criteria, the decision to continue the approach, or conduct a go-around, became applicable by the time the aircraft reached 300 ft above the runway.

The following recorded parameters were observed from below 300 ft to the threshold:

• the aircraft crossed the threshold of runway 08 at a height of 55 ft
• aircraft speed remained within V_ref to V_ref +20 kt
• sink rate (vertical speed) less than 1,000 fpm. 

The recorded data indicated (purple line in Figure 6) that at the 300 ft (578 ft corrected altitude) stabilised approach gate, the aircraft was about 42 ft above the normal 3 degree slope (orange line), and remained above it until reaching 104 ft above the aerodrome elevation. During this period, the sink rate exceeded 800 fpm for 8 consecutive seconds between 1051:06 and 1051:14 local time.

At 1051:20, the aircraft crossed the threshold with a groundspeed of 94 kt. The pilot reported the wind component during the approach was a south-easterly wind between 8‍–‍10 kt, which would have resulted in a 3‍–‍4 kt headwind component. Accordingly, the aircraft’s airspeed was likely around 97‍–‍98 kt as it crossed the runway threshold, which was 6‍–‍7 kt above the V_ref of 91 kt.

At 1051:29, the corrected altitude of the aircraft matched the terrain elevation, which indicated that the aircraft landed 402 m along the runway with a groundspeed of 81 kt. The pilot reported applying brakes as the aircraft passed the apron area, which occurred about 2 seconds after touchdown. Following a ground roll distance of about 540 m, the aircraft decelerated to a groundspeed of 45 kt when it vacated the left side of the runway at 1051:48.

Figure 6: VH-NXA approach and landing

All times are coordinated universal time (UTC). Local time was Central Standard Time (CST), which was UTC +9 hours and 30 minutes. The aerodrome elevation is 278 ft. Source: ATSB, data provided by OzRunways and Google Earth

Related occurrences 

ATSB investigation AO-2024-056

On 2 November 2024, a GippsAero GA8-TC Airvan, was being used to conduct a scenic flight from Whitsunday Airport (Shute Harbour), Queensland. During the landing the aircraft departed the upwind end of the runway before entering marshy ground and coming to a stop in a ditch. 

The ATSB investigation identified that the aircraft's approach was above profile with a high airspeed and the pilot had an incorrect understanding of the required approach speed. Subsequently, the pilot did not initiate a go-around, resulting in a landing beyond the planned touchdown point. The ATSB also identified that the operator’s weight and balance system used an incorrect empty weight moment arm to calculate the aircraft's centre of gravity, and passengers were not weighed in accordance with its procedures.

Safety analysis

On the morning of 29 May 2025, a Cessna 310R, registered VH-NXA, was being operated by Marthakal Yolngu Airline on a non-scheduled air transport flight from Darwin to Lake Evella, Northern Territory, with a pilot and 4 passengers on board. 

During a straight-in visual approach, without visual slope guidance to runway 08 at Lake Evella, the pilot assessed that the approach was stable and continued with the landing.  After the aircraft crossed the runway threshold, it floated for a prolonged period and subsequently landed before reaching a taxiway located about halfway along the runway. 

When the pilot applied braking passing the airport’s apron area, the aircraft did not decelerate as expected. The aircraft subsequently overran the runway and collided with a fence. The pilot and passengers were uninjured, however, the aircraft sustained substantial damage.

This analysis examines how the condition of the aircraft braking system, and the conduct of the approach and landing, contributed to the runway excursion. It also explores the operator’s self-reported passenger weight procedures and electronic weight and balance system, and how the latter, in combination with incorrect pre-flight weight calculations, led to the aircraft being operated above the weight limits specified in the pilot’s operating handbook.

Pre-flight maintenance 

Maintenance which was completed on the aircraft 3 days before the occurrence involved numerous concurrent tasks. These were conducted by a licensed aircraft maintenance engineer (LAME) with the assistance of an apprentice. One of the tasks involved the apprentice conducting maintenance on the braking system due to leaking brake callipers. It was the LAME’s expectation that the apprentice had replaced the main wheel brake pads during this maintenance task.

This expectation influenced their assessment that the aircraft rolled forward during post‑maintenance engine run-ups, due to the new brakes requiring ‘burning in.’ In this case, a physical verification of the brake pads was not conducted as a result. 

On the morning of the occurrence, the LAME carried out corrective maintenance in response to the flight instructor text message report of ‘spongy brakes’ the day prior. While the occurrence pilot was aware of this report, they were not aware of the LAME’s experience with the aircraft rolling forward during the engine run-up. 

When the pilot commenced the pre-flight engine run-up for the occurrence flight, the brakes failed to keep the aircraft stationary. The pilot physically increased the brake pressure and successfully kept the aircraft stationary, but did not advise maintenance personnel. The pilot’s limited experience on multi-engine aircraft led them to consider that this might be normal, which was reinforced during a brief discussion with another Cessna 310 pilot. 

Gaps in communication and incorrect assumptions allowed a latent defect to persist into operation, contributing to the runway overrun in this occurrence.

Approach

Lake Evella Aerodrome was not equipped with visual slope guidance, and as a result, the pilot relied on their assessment of visual cues of the runway itself to assess whether they were on the correct approach path while they typically used the runway threshold as their aiming point.  

Recorded data from the pilot’s Android phone indicated that the aircraft was higher than the usual 3 degree ‘correct flight path’. The rate of descent exceeded 800 fpm for a period of 8 consecutive seconds until the aircraft descended below 140 ft relative to the runway. At the time, the pilot recalled the approach ‘seemed stable,’ while the operator’s stable approach criteria permitted rates of descent up to 1,000 fpm. 

The aircraft subsequently crossed the threshold of runway 08 at a height of 55 ft with a ground speed of 94 kt. ATSB analysis concluded that the aircraft’s airspeed was likely 6‍–‍7 kt above the V_ref for the recalculated landing weight 91 kt.

When the aircraft neared the point of touchdown, it was subjected to ground effect, which meant that excess airspeed at the point of flare would result in a considerable float distance due to the reduction in drag and lack of power-off deceleration in ground effect (Federal Aviation Administration, 2023). 

Additionally, landing distances provided in the aircraft flight manual are based on the aircraft achieving V_ref (plus wind and gust additives) at 50 ft above the runway surface. As a result, any additional airspeed will result in a later touchdown and reduce the remaining landing distance available (Federal Aviation Administration, 2023). 

In this case, the additional airspeed crossing the threshold likely resulted in a prolonged float in ground effect. This resulted in the aircraft touching down 402 m beyond the runway threshold which was the pilot’s usual aiming point. Subsequently, the pilot applied braking about 2 seconds after the touchdown, at which point, there was about 585 m of remaining distance available to decelerate on the runway.

Excursion

The pilot first became aware of an issue with the braking system when they applied brake pressure during the landing roll with about 585 m of runway remaining. Witness accounts recalled the aircraft was travelling at high speed as it passed the taxiway and apron area without any significant deceleration. Additionally, recorded data showed the aircraft only slowed from 81 kt at touchdown to 45 kt when it vacated the left side of the runway following a ground roll distance of about 540 m. 

At the aircraft’s landing weight, the ATSB calculated ground roll distance required was 195 m, which was sufficient to bring the aircraft to a stop within the remaining length of the runway had the brakes been functioning correctly. However, the loss of hydraulic brake fluid and the worn brake pads on the right-hand brake reduced the available braking capacity. As a result, the braking capacity was insufficient to arrest the aircraft’s forward momentum before the end of the runway. The pilot attempted to increase the available stopping distance by steering left and departing the runway, however it was insufficient, and the aircraft subsequently collided with the perimeter fence.

Passenger weights

The operator’s exposition permitted the use of self-reported passenger weights for weight and balance calculations, without requiring the application of additional allowances or validation. This practice introduced errors into the weight and balance data used for pre-flight planning.

Research has found that people tend to underestimate the weights of themselves and others. Further, people are less accurate at estimating the weight of others than they are of themselves.[9] To cater for the variation in weight, it is recommended that operators weigh passengers or apply adjustment factors to self-reported values (Civil Aviation Safety Authority, 2025). In contrast, the operator’s reliance on unadjusted self-reported passenger and carry-on baggage weights provided no systematic mitigation for potential inaccuracies, which increased the likelihood that the aircraft would be operated overweight or at centre of gravity limits outside the manufacturer’s requirements.

Electronic weight and balance

The operator used an electronic weight and balance system to calculate aircraft loading data for each aircraft in operation. In that electronic system, VH-NXA had been configured with the higher maximum weight limits applicable to aircraft fitted with a vortex generator (VG) modification. However, the aircraft did not have the specified modification installed. Consequently, the programmed maximum zero-fuel, ramp and take-off and weights in the system exceeded those authorised in the aircraft’s POH.

This configuration error meant the electronic weight and balance system allowed VH‑NXA to be loaded in excess of the certified weight limitations, while still indicating that the loading complied with those limitations. This created an ongoing risk that the aircraft could be operated above the approved maximum weights.

Weight exceedances  

During the occurrence flight, the aircraft was operated above the certified maximum ramp and take-off weights due to cumulative errors in the pilot’s weight and balance calculations. As a result of the configuration errors in the electronic weight and balance system, no alert to the overweight condition was made. 

The pilot, who was conducting their first multi-engine command flight, reported feeling rushed during pre-flight preparation, which likely reduced the opportunity for careful verification of passenger weights, totals and data entry. Review of the weight and balance documentation from the occurrence identified multiple inaccuracies, indicating that the overweight condition arose from a breakdown in the usual cross-checking processes rather than a single isolated error.

Although the overweight condition did not result in the aircraft exceeding its maximum landing weight, operating above certified weight limits is known to increase take-off and landing distances and degrade braking performance. Additionally, excessive weight reduces the available safety margin if an in-flight emergency condition should arise (Federal Aviation Administration, 2016).

Findings

From the evidence available, the following findings are made with respect to the runway excursion involving Cessna 310, VH-NXA, at Lake Evella Aerodrome, Northern Territory, on 29 May 2025. 

Contributing factors

• The certifying licensed aircraft maintenance engineer did not verify that the brake pads had been replaced by an apprentice during scheduled maintenance, which resulted in the aircraft being returned to service with worn brake pads on the right brake system.
• The pilot conducted the approach above the standard profile and crossed the threshold above the normal approach speed. This resulted in a landing beyond the planned touchdown point, and the pilot applied braking about halfway along the runway, which reduced the available distance to decelerate on the runway.
• Due to the worn right brake pad and the lack of hydraulic fluid in the right brake system, there was insufficient braking capacity available to prevent a runway overrun following the landing and the application of brakes about halfway along the runway.

Other factors that increased risk

• Marthakal Yolngu Airline’s procedures did not require that additional allowances were applied when using self-reported passenger weights for weight and balance calculations. (Safey issue)
• Marthakal Yolngu Airline’s electronic weight and balance system used incorrect maximum weights for the aircraft, which increased the risk of flight crew operating the aircraft above the certified weight limitations. (Safey issue)
• The aircraft was operated overweight due to incorrect weight and balance calculations, as well as errors in the electronic weight and balance system.

Safety issues and actions

Self-reported passenger weights

Safety issue number: AO-2025-024-SI-01

Safety issue description: Marthakal Yolngu Airline’s procedures did not require that additional allowances were applied when using self-reported passenger weights for weight and balance calculations. 

Weight and balance system

Safety issue number: AO-2025-024-SI-02

Safety issue description: Marthakal Yolngu Airline’s electronic weight and balance system used incorrect maximum weights for the aircraft, which increased the risk of flight crew operating the aircraft above the certified weight limitations. 

Safety action not associated with an identified safety issue

Additional safety action by D & T Aircraft Engineering 

D & T Aircraft Engineering advised that, following this occurrence, a debriefing was conducted with maintenance personnel to discuss key learnings. It was acknowledged that increased vigilance would be exercised in the future to ensure that aircraft components are carefully inspected and confirmed to be in a serviceable condition following the completion of maintenance tasks. Additionally, the organisation stated that it would prioritise accessing the aircraft at the earliest opportunity in the future to assist in identifying potential causes of component failure, particularly in cases where perishable evidence plays a critical role in determining the cause.

Glossary

Sources and submissions

Sources of information

The sources of information during the investigation included:

• pilot of the accident flight
• the operator
• the flight training organisation
• maintenance organisation
• Civil Aviation Safety Authority
• Bureau of Meteorology
• accident witnesses
• OzRunways. 

References

Civil Aviation Safety Authority. (2025). Multi-Part AC 121-05, AC 133-04 and AC 135-08 - Version 1.2. Retrieved from https://www.casa.gov.au/sites/default/files/2021-08/multi-part-advisory-circular-121-05-ac-133-04-ac-135-08-passenger-crew-baggage-weights.pdf

Civil Aviation Safety Authority Australia. (2021). Safety behaviours human factors workbook for engineers. Retrieved from https://www.casa.gov.au/sites/default/files/2021-06/safety-behaviours-human-factors-engineers-workbook.pdf

Federal Aviation Administration. (2016). Aircraft Weight and Balance Handbook. Retrieved from https://www.faa.gov/sites/faa.gov/files/2023-09/Weight_Balance_Handbook.pdf

Federal Aviation Administration. (2023). Advisory Circular Subject: Aircraft Landing Performance and Runway Excursion Mitigation. Retrieved from https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_91-79B_FAA.pdf

Federal Aviation Administration. (2023, March). Pilot’s Handbook of Aeronautical Knowledge. Retrieved from https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/faa-h-8083-25c.pdf

Federal Aviation Administration. (n.d.). Spatial Disorientation Visual Illusions. rev. 2/11. Washington DC: U.S. Department of Transportation Federal Aviation Administration. Retrieved from https://www.faa.gov/sites/faa.gov/files/about/initiatives/got_weather/archives/spatiald_visillus.pdf

Ramos , E., Lopes, C., & Barros , H. (2009). Unawareness of weight and height – the effect on self-reported prevalence of overweight in a population-based study. The Journal of Nutrition, vol. 13, pp.310–314.

Reed, D., & Price , R. (1998). Estimates of the heights and weights of family members: accuracy of informant reports. International Journal of Obesity, vol. 22, pp.827–835.

Shapiro , J. R., & Anderson, D. A. (2003). The effects of restraint, gender, and body mass index on the accuracy of self-reported weight. International Journal of Eating Disorders, vol. 34, pp.177–180.

Submissions

Under section 26 of the Transport Safety Investigation Act 2003, the ATSB may provide a draft report, on a confidential basis, to any person whom the ATSB considers appropriate. That section allows a person receiving a draft report to make submissions to the ATSB about the draft report. 

A draft of this report was provided to the following directly involved parties:

• pilot of the accident flight
• the operator
• maintenance organisation
• Civil Aviation Safety Authority
• Bureau of Meteorology.

Submissions were received from: 

• pilot of the accident flight
• the operator maintenance organisation
• Bureau of Meteorology.

The submissions were reviewed and, where considered appropriate, the text of the report was amended accordingly. 

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through:  identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. About ATSB reports ATSB investigation reports are organised with regard to international standards or instruments, as applicable, and with ATSB procedures and guidelines. Reports must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2025 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Commonwealth Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this report is licensed under a Creative Commons Attribution 4.0 International licence. The CC BY 4.0 licence enables you to distribute, remix, adapt, and build upon our material in any medium or format, so long as attribution is given to the Australian Transport Safety Bureau.  Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

Investigation summary

What happened

In the early morning of 27 March 2025, rapidly rising floodwater started surrounding the Queensland town of Adavale, flooding homes and requiring people to seek refuge on their roofs.

The planned Queensland Fire Department swift water rescue team were unable to deploy to Adavale, so Channel Country Helicopters, a local helicopter mustering company, was requested to assist with the evacuation of the town as a mercy flight. They agreed and subsequently dispatched three Robinson R22 helicopters to Adavale.

When the second helicopter arrived overhead the town, the pilot spotted a person on the roof of a demountable building with a strong flood current flowing around it. The pilot assessed the situation as critical and proceeded to land on a flat roof section to pick up the passenger. The pilot was not sure whether the roof could hold the weight of their helicopter, they kept the aircraft in a flying condition with the skids resting lightly on the roof. 

After the passenger climbed in, the pilot took off from the roof and attempted to depart upwind. As the helicopter cleared the demountable roof it was no longer in ground effect and available performance was insufficient for level or climbing flight. The lack of available power caused the rotor RPM to decay, activating the ‘low RPM’ warning horn. The pilot then immediately realised the criticality of the situation, identified a sheltered landing spot and conducted a controlled ditching into chest-high floodwater in the lee of a nearby building.

The pilot and passenger then safely exited the helicopter into the water but were unable to climb to the roof of the building. The pilot then attempted to retrieve a ladder from the take-off site but was washed away by the current. They found shelter in a tree about 900 m downstream of the ditching site and was later rescued by another helicopter. The passenger avoided the strong current by standing close to the helicopter, but sustained significant chemical burns due to the fuel seeping out of the helicopter’s tank.

The helicopter was substantially damaged by the floodwater.

Source: Photo received from operator

What the ATSB found

After the embarkation of the passenger on the roof, the helicopter was overloaded to an extent that prevented flight out of ground effect, with insufficient clear space available to accelerate to an airspeed to obtain translational lift. Once this was recognised by the pilot, they conducted a successful ditching into floodwater. The pilot’s choice of landing site in the only sheltered area available allowed for the helicopter to remain upright in the otherwise fast‑flowing water. Additionally, their rapid and correct application of the helicopter manufacturer’s low RPM recovery procedures resulted in a controlled ditching which allowed both pilot and passenger to exit the helicopter without injury.

The pilot’s decision‑making was affected by the heavy workload of conducting a rescue operation, for which they were not prepared, in a light helicopter. The pilot conducted an unfamiliar and demanding rescue operation which likely overwhelmed their decision‑making capacity while the passenger was boarding the helicopter. This heavy workload, in addition to the rotor operating at high power, prevented the pilot from verbally briefing the passenger on seatbelt use and other safety information. The passenger was subsequently unrestrained during the flight. 

Once committed to the rescue, under high workload and the perception of imminent danger of staying on the roof, the pilot continued with the plan and did not reassess the feasibility of the flight once they realised that helicopter performance was going to be marginal with the heavier than expected passenger on board.

The helicopter operator was aware that the requested flight was outside of their normal scope of operations. However, they felt a moral obligation to act due to their perception of being the only people that could help preserve life. This meant that they agreed to conduct mercy flight operations to attempt rooftop rescues for which they were not trained or equipped.

Safety message

Many aspects of emergency response in Australia rely on volunteers, both by organised groups and ad-hoc by people who happen to be in the right position to help. These ad‑hoc or bystander rescues save many lives when dedicated, trained assistance is not available. However, when responding to an emergency it is of paramount importance to stop and take a moment to assess risk to the rescuers before assisting others. This applies in any emergency context, not just aviation, and is strongly reinforced in training for surf rescue, medical first aid, fire-fighting and marine rescue operations. 

In the aviation context, mercy flights are by definition outside the scope of the normal operations of the involved pilots and operators. This places a high burden on pilot and operator to assess risks that may be out of their area of expertise. Where possible it is important for all involved to take the time to reassess the risk of (continuing) the proposed flight and consider any alternatives. This may include discontinuing a rescue and waiting for additional assistance, as continuing may expose the crew and the people being assisted to much greater risks.

Summary video

The investigation

The occurrence

On the morning of 27 March 2025, widespread rain associated with a passing surface trough was causing catastrophic flooding in Queensland’s channel country region. In particular, the small rural town of Adavale, about 89 km north of Quilpie, was most heavily affected. Telephone communication had been lost the previous day, but during the night reports reached authorities indicating that the town was rapidly flooding and that some people in lower lying areas had sought shelter on roofs.

At around 0630,[1] an aerial work operator, Channel Country Helicopters, dispatched a Robinson R22 helicopter, registered VH-KNG, from Quilpie with the pilot and a police officer on board to assess the situation in Adavale. The officer had tried to reach Adavale in the days before but had found the roads impassable. A helicopter flight was previously arranged but had not been possible due to the heavy rain until the operator noted an improvement of weather conditions.

On arrival in Adavale at 0721, the pilot and the police officer found the situation in the town critical, with fast‑flowing floodwaters throughout the town. This limited landing access, with the only dry place available at the town waste disposal site, about 1 km to the north‑east. After disembarking the police officer, the pilot returned to Quilpie and refuelled the helicopter.

Around 0915, the helicopter operator received a phone call from the local disaster management group asking ‘if they were able to conduct a mercy flight’[2] as there were people reported on the roofs of buildings in Adavale and no other rescue assets were available. The operator assessed that the weather was not suitable for VFR flight at the time, but agreed to send its helicopters when able. The operator then briefed its pilots on some of the risks involved, including the possibility of overloading roofs when landing and the need to pay special attention to powerlines and other overhead obstructions that were expected in the town.

Once the weather cleared, the operator mobilised the first 2 Robinson R22 helicopters, shortly followed by a third helicopter.

The first helicopter that arrived in Adavale touched down on a roof of a demountable building, boarded a resident who was waiting on the roof, and departed to a nearby cattle station.

At around 1115, the second helicopter, VH-KNG (flown by the pilot who had ferried the police officer to Adavale that morning), which had stopped en route to avoid flying through rain showers,[3] was back overhead Adavale where the pilot observed that the fast-flowing water was ‘pushing around a parked semi‑trailer road‑train’, reinforcing a sense of urgency to evacuate residents. The pilot then spotted a person on the same roof and elected to conduct a rooftop rescue. 

On approach to the rescue site, the pilot recalled that they assessed that the building was at immediate risk of being washed away, and that the roof strength was insufficient to carry the full weight of the helicopter. The pilot then opted to maintain lift on the main rotor while picking up the passenger to reduce the load on the roof sheeting. The helicopter touched down on the flat roof between the two demountable buildings (Figure 1). The pilot kept the helicopter flying throughout the passenger embarkation, with only part of the skids lightly touching the roof.

Figure 1: View underneath roof

Source: Video still from passenger, annotated by the ATSB

The passenger boarded the helicopter from the left side, into the left seat, wearing a rain jacket with some personal effects. During the rapid boarding and take-off, the noise of the engine running at full power did not allow verbal communication with the boarding passenger. The passenger did not attempt to secure their seat belt prior to take‑off. 

The pilot reported realising the passenger was heavy, but being confident that the helicopter would be able to fly away after building up airspeed to obtain translational lift.[4] The pilot lifted off the helicopter (in ground effect[5] over the roof) and immediately departed into wind. However, once clear of the roof with reduced ground effect, the helicopter was no longer able to sustain level flight. As rotor speed decayed below 97%, the low rotor RPM light and horn alarms activated in the cockpit.

The pilot lowered the collective[6] and applied aft cyclic[7] and quickly concluded that the helicopter would not be able to clear approaching obstacles such as trees, buildings and powerlines during the take‑off run. They then selected an area sheltered from the floodwater current, behind a building about 60 metres away, and conducted a controlled ditching.

Figure 2: Overview of flight

Source: Google Earth, annotated by the ATSB

After ditching, the helicopter became submerged in floodwater, stopping the engine. Due to the lee of the building protecting the helicopter from the main current, it remained upright, allowing both the passenger and pilot to egress into the chest deep water.

There was no access to the roof of the building, so the pilot attempted to return to the take-off site to retrieve a ladder. However, the pilot was swept away by the current before finding shelter in a tree about 900 metres downstream, where they were later rescued by a larger helicopter.

The passenger stayed in the lee of the building, in the sheltered water near the helicopter, and was later transported to a temporary shelter on a roof by the police officer, who had commandeered a small motorboat.

The pilot was unhurt, but the passenger sustained serious chemical burns due to exposure to the fuel leaking from the submerged helicopter’s tank. The passenger was treated for their injuries by the swift-water rescue team and later in hospital.

No further rooftop rescues were conducted by the operator, instead company helicopters guided motorboat and swift-water rescue teams to people in need of rescue.

Figure 3: Adavale flood in the afternoon after the accident

Source: Nathan Covey

Context

Pilot information

The pilot held a Commercial Pilot Licence (CPL) for helicopters and aeroplanes, a valid class 2[8] aviation medical certificate and a low‑level mustering endorsement for helicopters. 

The pilot reported having flown for about 25 years, first in fixed wing aircraft and then operating helicopters for the last 3 years, mostly in support of cattle mustering operations. 

At the time of the accident, the pilot had accumulated about 11,400 hours aeronautical experience, of which about 800 hours were on R22 helicopters. The pilot had flown about 30 hours in the preceding 90 days but had not flown for 5 days prior due to the poor weather conditions. 

The pilot was very familiar with the area, having flown there for most of their career, and felt well rested on the day of the accident. They reported that they started work at about 0600 for the initial flight to Adavale with the police officer, and that they were not experiencing any effects of fatigue.

Aircraft information

General information

The Robinson Helicopter Company R22 Beta II helicopter is powered by a Textron Lycoming O‑360‑J2A 4‑cylinder piston engine. The R22 has 2 seats, with the pilot flying from the right seat, with each seat fitted with a 3‑point, inertia reel shoulder strap seatbelt, similar to those used in motor vehicles.

The R22 is commonly used for helicopter flight training, private flight and livestock mustering operations. It has a payload capacity of about 215 kg and a maximum seat limit of 109 kg (including any items in the small luggage compartment under the seats).

VH-KNG

VH-KNG was manufactured in the US in 2001 and first registered in Australia in October 2011. The helicopter had undergone a periodic inspection on 21 February 2025 with a total time in service of 13,424.2 hours.

The current maintenance release was not located and was likely lost in floodwaters. There were no indications of any mechanical issues with the aircraft before the accident.

Figure 4: VH-KNG after the accident

Source: Channel Country Helicopters

Weight and balance

During the last maintenance period the aircraft was weighed, and empty weight was recorded as 405 kg. The helicopter was used in mustering operations, and had both doors removed. This reduced the empty weight by about 5 kg, increasing the total payload to about 222 kg for a maximum take‑off weight of 622 kg.

With full fuel when it departed Quilpie, the ATSB calculated, based on the flying time from departure in Quilpie, the helicopter had approximately 70 L or 50 kg of 100LL Avgas[9] on board on arrival in Adavale. The pilot reported their weight was 78 kg. As can be seen in Table 1, that left an available load of about 94 kg.

The passenger reported their weight as around 130 kg with an estimated additional 10 kg for their wet clothing and essential medical equipment also carried. This resulted in the helicopter being about 46 kg overweight.

Table 1 VH-KNG calculated take-off weight

Helicopter performance

Performance data provided by the Robinson R22 pilot’s operating handbook (POH) indicated that, at its maximum take‑off weight (MTOW) of 622 kg and the temperature at the time of the accident of 24°C (see Meteorological conditions), the helicopter should have had sufficient available performance to hover in ground effect (IGE) up to a pressure altitude of about 7,900 ft and an out of ground effect (OGE) up to a pressure altitude of about 3,400 ft (Figure 5).

This performance is based on ‘ideal conditions’, however, in this case, high humidity would likely have further decreased the available performance by as much as 3 or 4% (FAA, Federal Aviation Agency, 2021). However, this should still have allowed OGE hover at maximum take‑off weight, at the calculated pressure altitude of 811 ft at the time and location of the accident.

No performance data was available for the helicopter outside its maximum allowed take‑off weight and the manufacturer advises against exceeding limits due to possible overloading of the rotor drive components.[10]

Figure 5 shows the maximum pressure altitude for flight out of ground effect at maximum take‑off weight (orange line) and the calculated helicopter weight and actual pressure height (red line).

The pilot recalled that they thought that the helicopter performance would be ‘marginal’ on take‑off, but believed they would be able to climb out using translational lift after take‑off.  

Figure 5: OGE hover ceiling vs gross weight

Source: Robinson R22 Pilot’s operating handbook, annotated by the ATSB

Power check 

To confirm sufficient power is available for hover out of ground effect, the Robinson flight training guide (Robinson Helicopter Company, 2019) recommends conducting a power check before committing to a take‑off requiring OGE hover performance:

…Perform a takeoff to a 2 foot IGE hover and complete a hover check to confirm available power. The [OGE] maneuver should not be attempted unless the IGE hover manifold pressure is 2 inches below the maximum takeoff power (5 minute) limit…

The pilot did not conduct a power check but they stated that they were aware the helicopter was heavily loaded and that they had to take off straight away as the building was ‘highly likely to be washed away’.

Confined area take-off

The manufacturer’s recommend take-off profile, as defined in the POH (Figure 6), involves accelerating in ground effect before pitching up into a climb. This technique ensures sufficient energy and reaction time available at any stage of the take‑off to enter autorotation in case of an engine or tail‑rotor failure. For the R22, this required acceleration to 45 kt indicated airspeed in ground effect before starting to climb. 

Figure 6: Height velocity diagram Robinson R22

Source: R22 Pilot’s operating handbook, annotated by the ATSB

When operating from unprepared landing areas, physical space may not be available to follow the recommended take‑off profile. As this forces the helicopter to climb out of ground effect before obtaining translational lift, the pilot must ensure that the helicopter’s weight is below the OGE limit before attempting a confined area take‑off.

The Civil Aviation Safety Authority (CASA) has published advisory circular 91‑29 (AC 91‑29): Guidelines for helicopters – suitable places to take‑off and land (CASA, 2023). Section 11.1.1 provided the following description of a ‘confined area’:

An unprepared landing site that has obstructions that require a steeper than normal approach, where the manoeuvring space in the ground cushion is limited, or whenever obstructions force a steeper than normal climb-out angle is often defined as ‘Confined Area’.

Photos, video and satellite imagery of the take‑off site show several obstructions in the form of power lines and trees in the departure direction (Figure 2). These obstructions were high enough to limit departure using the recommended take‑off profile and to require a confined area take‑off. 

Low RPM recovery

The lift produced by a helicopter rotor is determined by a combination of rotor RPM, and the angle of attack of the rotor blades. The pilot controls the amount of lift by using the collective lever to vary the pitch angle of the blades. As the pitch increases, the governor increases the engine throttle to maintain a constant rotor RPM. When the governor has fully opened the throttle, any further increase of collective pitch will result in the rotor RPM reducing, progressively reducing lift and resulting in a loss of climb performance or a descent.

Further increasing the collective pitch will force the blades to reach their critical angle of attack (around 15°) and airflow will separate from the blades resulting in aerodynamic rotor stalling.

As per Robinson Safety Notice 24: 

The stall causes a sudden loss of lift and an increase in drag, slowing down rotor RPM further. As the helicopter begins to fall the upward moving air through the rotor increases angle of attack further making recovery virtually impossible, even with full down collective.[11]

And Robinson Safety Notice 10:

No matter what causes the low rotor RPM, the pilot must first roll on throttle and lower the collective simultaneously to recover RPM before investigating the problem. It must be a conditioned reflex. In forward flight, applying aft cyclic to bleed off airspeed will also help recover lost RPM.[12]

A low RPM light and warning horn are fitted in the R22 to warn the pilot of this condition; both activate when the rotor RPM decays below 97%. 

The R22 pilot’s operating handbook states:

LOW RPM HORN

[…] The horn activates simultaneously with the LOW RPM caution light and indicates rotor speed below 97% RPM. To restore RPM, lower collective, roll throttle on and, in forward flight, apply aft cyclic. [..] 

The R22’s light weight and low inertia rotor system means that rapid pilot intervention is required before control is lost. 

Meteorological conditions

No weather forecast was available for either Quilpie or Adavale, a grid point wind and temperature forecast for southern Queensland showed winds near Adavale at around 6 kt at 010°, which is consistent with the pilot’s reported observations of a light northerly wind and localised showers. Temperature was reported at 24°C. No humidity observations were available for Adavale, but given the inclement weather and flooding conditions, it was expected to be high. 

The nearest reported QNH,[13] at Charleville, about 175 km away, was reported as 1012 hPa. Adavale lies at an elevation of 781 ft which resulted in a pressure altitude of 811 ft and a density altitude of 2,048 ft.

Operator information

The helicopter was operated by Channel Country Helicopters (CCH), which was based at Quilpie Airport and held a Civil Aviation Safety Regulation 1998 (CASR) Part 138 aerial work certificate. It operated 3 Robinson R22 helicopters used primarily for mustering and agricultural aerial work.

While a CASR Part 138 aerial work certificate does not allow the operator to carry passengers as part of air transport operations, it did permit carriage of ‘aerial work passengers’ on operations which are aerial work operations. 

These included aerial work passengers such as:

• persons rescued as part of search and rescue operations
• emergency service operation personnel carried as part of an aerial work operation that is also an emergency service operation.

Disaster response management

Managing disaster response in Australia is primarily a matter for the individual states and territories. To provide for disaster response and recovery at an appropriate level, Queensland has plans in place at local, district and state levels.

The disaster response for the flooding in south‑west Queensland was managed at a district level by the district disaster coordinator (DDC) in Charleville, guided by the district disaster management plan (DDMP), and locally in Quilpie council led by the local disaster coordinator (LDC), following the local disaster management plan (LDMP). 

Flooding in the area had severely affected the roads around the region in the days before the accident, this was followed by a loss of phone coverage in both Quilpie and Adavale the day before the accident, which meant that only limited satellite communication was available.

However, the LDC had maintained some contact with Adavale residents and identified that overnight reports indicated that flooding was becoming more widespread and that the town of Adavale was at risk of severe flooding with residents beginning evacuation to the roofs of their dwellings.

Queensland Fire Department

As flooding had been anticipated in the wider region due to the expected heavy rains, a swift-water rescue team (SRT)[14] had been pre-positioned in Charleville in anticipation of the floods. This consisted of specially trained Queensland Fire Department personnel with an inflatable rescue craft (Figure 7) being transported by a chartered heavy‑lift helicopter to the site of the rescue. This helicopter was not equipped or crewed for instrument or night flying conditions and so could only be used during daylight and in visual meteorological conditions (VMC).[15]

As the only dedicated rescue asset available in the area, the SRT was planned to be used for life threatening situations only, under direction of the DDC. 

The LDC in Quilpie contacted the DDC in Charleville for urgent assistance in the early hours of the morning of the accident. However, due to a combination of inclement weather conditions and a technical fault on the heavy‑lift helicopter, the SRT was not immediately available to deploy.

Figure 7: QFD swift-water rescue team and volunteer boats at Adavale

Source: Queensland Fire Department

Queensland Police Service

The Queensland Police (QPS) operational procedures manual (OPM) chapter 2.21.2 addresses helicopter use in search and rescue as well as disaster management situations. These procedures required approval from the DDC before tasking helicopters. The OPM specified that privately owned helicopters could be used if no other options were available, but did not include directions on the identification of hazards or the management of risk when using privately owned helicopters.

Disaster management plans

Neither the DDMP, LDMP nor the local evacuation sub‑-plan contained references to evacuation by helicopter. Adavale residents were anticipated to use their own means of transport to get to the evacuation centre.

The residents trapped on their roofs were unable to make their own way to higher ground due to the fast‑flowing floodwaters. As the SRT was unable to immediately deploy, and no other rescue assets were available at short notice, the DDC requested that the LDC check if local helicopters were available to conduct rescues.

Mercy flight

Although the term ‘mercy flight’ is no longer defined in aviation regulations, the Civil Aviation Safety Authority (CASA) recognises that there may be times when it is necessary for pilots to not follow aviation safety rules in order to respond to a sudden or extraordinary emergency.[16] The legal basis for this is the provision in section 10.3 of the Commonwealth Criminal Code Act 1995 which states that:

a person is not criminally responsible for an offence [in response to a] sudden or extraordinary emergency . . . if committing the offence is the only reasonable way to deal with the emergency.

CASA makes it clear that these provisions are a last resort option. For example, a pilot can get people to emergency medical treatment or out of a life‑threatening situation if there is no other (legal) way to do so. Before declaring a mercy flight, CASA states that pilots and operators should consider if the flight itself gives rise to equally serious or greater risks to safety and to manage those risks accordingly (CASA, 2025).

Tasking of local helicopters 

The deputy LDC contacted the CCH chief executive officer (CEO) at Quilpie Airport at about 0915 on the morning of the accident and requested ‘mercy flight’ operations with their helicopters to rescue people from roofs in the Adavale township. Although outside the scope of their normal operations, the CEO recognised the urgency of the request and the need to provide immediate help to the people trapped in the floodwater and informed the deputy LDC that they would send out helicopters as soon as the weather cleared enough to conduct safe operations. 

Operator processes

Pilot briefing

The CEO of Channel Country Helicopters (CCH) contacted the chief pilot, who was unable to get to Quilpie due to the floods. They discussed the mercy flight request and the need to conduct operations that were outside the scope of their normal operations in an effort to save lives. They agreed to assist in the rescue operation and identified a number of hazards to be mitigated. 

The CEO then informed the pilots of the need to conduct rooftop rescues and provided a briefing which included:

• risks of placing too much helicopter weight on temporary roof structures, which would require pilots to continue to fly the helicopter while boarding passengers
• risks associated with power lines in close proximity to the township, which would restrict landing and take-off areas.

Task familiarity

In the course of their normal employment, the operator’s pilots mostly conducted low level flight and aerial stock mustering. The pilots were not familiar with rescue operations, particularly those requiring special landing techniques, passenger onboarding during flight and in‑flight risk assessment of rescue operations at low level during emergencies. 

The accident pilot stated that they had never conducted rescue operations and had never landed on a structure before.

Pilot expectations

The pilot was well aware of the extent of the flooding due to the previous operations that morning and understood that there was little other external help available. They recalled that this set an expectation that they were the only available assistance at the time to evacuees in Adavale.

They reported that when asked to conduct a rescue flight, they felt compelled to assist due to the urgency of the natural disaster and the imminent risk to life. 

STEP landing

The technique used for landing on rooftops is defined as ‘Single-Skid, Toe-in and Hover Exit/Entry Procedure’ or STEP landing. STEP landings are commonly used in military, search and rescue, helicopter skiing, or any operation where a helicopter is unable to fully set its full weight down on its landing gear due to uneven or soft terrain.[17] 

The conduct of a STEP landing requires the pilot to keep most of their focus on controlling the helicopter throughout the boarding process. This was particularly important as any inadvertent interference with the controls by a boarding passenger into a small helicopter cabin could lead to uncontrolled helicopter movement.

While this manoeuvre is conducted routinely in certain types of operations, it is not commonly required during cattle mustering operations, and the pilot was not familiar with it.

Safety analysis

Introduction

On 27 March 2024, a Robinson Helicopter Company R22 Beta, registered VH-KNG, was being used to conduct rooftop rescue of residents of the township of Adavale, Queensland, during large scale flooding. After picking up a passenger from a rooftop, the pilot assessed during take-off that they did not have the required performance to continue flight and conducted a controlled ditching into floodwaters.

This analysis will explore the operational considerations pertaining to helicopter loading, take‑off performance, the pilot’s decision‑making and factors affecting the controlled ditching and survivability of the occupants.

Decision‑making processes

Pilot workload

Once committed to the rooftop landing, the pilot faced an increased workload due to a combination of factors which likely negatively affected their decision‑making processes.

While the pilot had significant aeronautical experience, including considerable recent experience flying the Robinson R22, they had never landed on top of a structure or conducted, or ever trained for, any type of rescue operations. The accident flight was their first attempt at a rescue operation and as such, it is likely that the pilot was under significant workload.

The high degree of concentration required likely limited the pilot’s cognitive capacity to assess the weight or brief the passenger prior to take‑off. Similarly, the lack of full consideration for the aircraft’s performance limitations were likely due to the narrowed attentional focus on the immediate control demands required in the confined area.

Plan continuation

Plan continuation is described as when pilots decide to continue with the original plan of action despite the presence of cues or information that suggests changing the course of action would be the safer (Orasanu, Fischer, & Davison, 2002)

Furthermore, as workload increases, the stimuli or conditions will appear obvious to people external to the situation; however, it can be very difficult for a pilot caught up in the plan to recognise the saliency of the cues and the need to alter the plan (Skybrary); (TSBC).

Plan continuation bias is often associated with situations involving dynamically changing risk and pilots underestimating the risk (Wiegmann, Goh, & O'Hare, 2002) as well as in high‑pressure environments where altruistic or time critical factors are present (Nadri and others 2024; Orasanu & Martin 1998) 

The need to identify and control rapidly changing risks in emergency flights is emphasised in the procedures used by dedicated SAR operations and firefighting aircraft. For example, the AMSA ‘rotorcraft rescue standards and procedures manual’ chapter 1.6 (AMSA, 2025) contains procedures for dynamic risk assessment process that involves the whole crew of the aircraft and is repeated at critical points in the mission.

As the only crew member on an ad hoc search and rescue mission, the pilot did not have training in these specialised procedures nor the support of additional crew members to alert them to the emerging indications of increased risk. Additionally, their understanding at this point that the passenger was in grave danger, made it likely that the pilot did not consider disembarking the passenger as a possibility.

Consequently, although the pilot was aware that the helicopter weight (and consequently performance) was ‘marginal’, their perception of imminent danger of roof collapse meant they did not change their plan and continued the take‑off without considering an alternative course of action.

Helicopter performance

On conducting the rooftop landing and passenger loading, the pilot was unable to calculate the gross weight of the helicopter before conducting the take‑off. Their estimation of the passenger weight was likely hampered by the bulky raincoat the passenger was wearing and the focus of the pilot on controlling the aircraft during an operation that they were not specifically trained or experienced in.

Weight data supplied to the ATSB by the accident pilot and passenger and a calculation of the remaining fuel load indicated that the helicopter was likely at least 46 kg over its maximum allowable take‑off weight (MTOW). 

Being significantly overweight, when the helicopter became airborne in ground effect over the building, there was no assurance that it could achieve the required performance that was needed to clear nearby obstacles during take‑off.

This could have been ascertained if the helicopter pilot had performed a power check while still above the building, however because the position of the helicopter on the roof was precarious with the passenger onboarding and the pilot held concerns that the structure would not support the helicopter weight or last much longer in the floodwater, this was not conducted. 

Moral obligation to conduct rescue operations

After receiving a phone call from the deputy local disaster coordinator informing them of the emergency in Adavale and requesting urgent assistance, the CEO of Channel Country Helicopters likely felt a moral obligation to assist in the rescue of evacuees facing extreme danger in the flood zone.

The request for mercy flight operations reinforced the urgency of the request and the need to assist even though it was outside the scope of their normal operations. This moral obligation was likely also passed to the pilots conducting the operations and would have been a strong influence in their acceptance of additional risk to their normal operations.

Controlled ditching

While embarking the passenger, the pilot initially felt confident that the helicopter performance was adequate to obtain translational lift. However, once it cleared the roof and lost ground effect, the helicopter was no longer able to sustain level flight or climb.

The pilot applied the correct recovery technique for low rotor RPM, selected the only sheltered location available, next to a building about 60 m from the take‑off site and conducted a controlled ditching of the helicopter with very little lateral speed.

It is common for helicopters to roll over in emergency landings, especially when ditching. In this case, the identification of a sheltered landing site, and the correct emergency technique, allowed the helicopter to remain upright after landing. This made it possible for both the pilot and passenger to safely exit the helicopter.

Survivability

The pilot’s workload during the boarding of the passenger likely limited the pilot’s cognitive capacity to brief the passenger. Furthermore, the high noise levels in the cockpit would have made a normal passenger safety briefing very difficult. Consequently, the passenger was not made aware of the use of the seatbelt, the weight limit of the seat, exit procedures and the possibility of inadvertent interference with the aircraft controls.

The incorrect (or lack of) use of seatbelts has been identified by the ATSB as a factor affecting survivability in several light aircraft incidents.[18] Inadvertent interference with helicopter flight controls by passengers has been identified as an issue in several incidents and is the subject of a Robinson Helicopters safety notice.[19]

If the pilot had continued the flight while building up airspeed in ground effect, there would have been a high risk of a forward impact with an obstacle or the floodwater. In that case the lack of seatbelt would have likely resulted in severe injuries to the unrestrained passenger.

In this accident the correctly applied forced landing technique by the pilot meant that the passenger was not exposed to forces large enough to require a seatbelt and their lack of restraint may have made their exit from the small helicopter cabin easier.

Exposure to fuel

After exiting the helicopter, the passenger witnessed the pilot being washed away in the floodwater. Recognising the danger of entering the floodwater current, they stayed in the sheltered area near the submerged helicopter. This exposed the passenger to AVGAS floating on the water, causing significant chemical burns that were subsequently treated in hospital.

Findings

From the evidence available, the following findings are made with respect to the ditching in floodwater involving Robinson R22 Beta, VH‑KNG, at Adavale, Queensland, on 27 March 2025.

Contributing factors

• The pilot conducted an unfamiliar and demanding rescue operation which likely overwhelmed their decision‑making capacity. Under time pressure due to the perceived imminent risk of a roof collapse, the pilot did not assess available performance after boarding a heavier than expected passenger and committed to the rescue with an immediate take‑off.
• The pilot departed with the helicopter significantly overweight. As a result, it did not have available performance to conduct a confined area take‑off.
• The CEO and pilot felt a moral obligation to conduct a rescue operation for which they were neither trained nor equipped. 

Other factors that increased risk

• The passenger was not briefed before the flight, consequently they did not wear the fitted 3‑point seatbelt, which increased their risk of injury.

Other findings

• After take-off, the pilot immediately realised the helicopter could not maintain altitude and, following the correct procedure for low rotor RPM, made a controlled landing in the only sheltered area available, allowing the pilot and passenger to exit safely.
• Flood currents around the ditching site prevented the passenger from seeking shelter away from the helicopter while waiting to be rescued. This caused an extended exposure to fuel floating on the water, resulting in serious chemical burns.

Sources and submissions

Sources of information

The sources of information during the investigation included the:

• pilot of the accident flight
• passenger the accident flight
• CEO of Channel Country Helicopters
• Queensland Police Service
• Queensland Fire Department
• maintenance organisation for VH-KNG
• Bureau of Meteorology
• photographs and videos taken on the day of the accident
• district disaster management plan for Charleville region
• local disaster management plan for Quilpie.

References

AMSA, Australian Maritime Safety Authority. (2025). Rotary Wing Search and Rescue standards and procedures manual (Version 8 ed.). Canberra.

CASA, Civil Aviation Safety Authority. (2023, December). AC-91-29. Retrieved from CASA.gov.au: https://www.casa.gov.au/sites/default/files/2022-07/advisory-circular-9…

CASA, Civil Aviation Safety Authority. (2025). Mercy flights and operation in an emergency. Retrieved from CASA.gov.au: https://www.casa.gov.au/operations-safety-and-travel/safety-advice/merc…

FAA, Federal Aviation Agency. (2021). Helicopter Flying Handbook. United States of America: Simon and Schuster.

Nadri, C., Regalado, J., Ferris, T., & Zahabi, M. (2024). Cognitive Biases in Commercial Aviation: Empirical Review of Accident Reports. Proceedings of the Human Factors and Ergonomics Society Annual Meeting. 68, pp. 56-60. Los Angeles: SAGE publications.

Orasanu, J. &. (1998). Errors in aviation decision making: A factor in accidents and incidents. Proceedings of the workshop on human error, safety, and systems development, (pp. 100-107).

Orasanu, J., Fischer, U., & Davison, J. (2002). Risk perception: A critical element of aviation safety. 15th IFAC World Congress (pp. 50-51). Barcelona: Elsevier.

QPS, Queensland Police Service. (2025). Operational Procedures Manual 106.1. Retrieved from https://www.police.qld.gov.au/qps-corporate-documents/operational-polic…

Robinson Helicopter Company. (2019). Robinson Helicopter Company Flight Training Guide. Torrance.

Skybrary. (n.d.). Retrieved from https://skybrary.aero/articles/continuation-bias

TSBC, T. S. (n.d.). Retrieved from https://www.tsb.gc.ca/eng/rapports-reports/aviation/2018/a18p0031/a18p0…

Wiegmann, D. A., Goh, J., & O'Hare, D. (2002, 6). The role of situation assessment and flight experience in pilots' decisions to continue visual flight rules flight into adverse weather. Human Factors, 189-197.

Submissions

Under section 26 of the Transport Safety Investigation Act 2003, the ATSB may provide a draft report, on a confidential basis, to any person whom the ATSB considers appropriate. That section allows a person receiving a draft report to make submissions to the ATSB about the draft report. 

A draft of this report was provided to the following directly involved parties:

• the pilot of the accident aircraft
• the operator of the accident aircraft
• Charleville district disaster coordinator
• Quilpie local disaster coordinator
• Civil Aviation Safety Authority
• Robinson Helicopter Company

A submission was received from the Civil Aviation Safety Authority.

The submission was reviewed and, where considered appropriate, the text of the report was amended accordingly.

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through:  identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. About ATSB reports ATSB investigation reports are organised with regard to international standards or instruments, as applicable, and with ATSB procedures and guidelines. Reports must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2025 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Commonwealth Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this report is licensed under a Creative Commons Attribution 4.0 International licence. The CC BY 4.0 licence enables you to distribute, remix, adapt, and build upon our material in any medium or format, so long as attribution is given to the Australian Transport Safety Bureau.  Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

Investigation summary

What happened

On 20 October 2023 the pilot of a Cessna 208 aircraft, registered VH‑UMV and operated by Experience Co, was conducting parachute operations at Barwon Heads Airport, Victoria with 16 parachutists on board. Passing about 500 ft on climb, the pilot detected a partial power loss consistent with a previously‑encountered transient power reduction.

Expecting the power to return immediately, the pilot did not lower the aircraft’s nose to maintain airspeed. The airspeed continued to reduce until the stall warning horn sounded and, due to the low height, low engine power and low airspeed, the pilot attempted to conduct a forced landing. However, the aircraft collided with water before continuing onto the riverbank and ground for approximately 50 m before coming to rest.

The aircraft was substantially damaged, 6 of the parachutists received serious injuries, 8 sustained minor injuries, and 2 were uninjured. The pilot also sustained minor injuries.

What the ATSB found

The ATSB found that passing about 500 ft on climb, the power reduced likely due to abnormal activation of an engine torque and temperature limiting system. Expecting the power to return quickly and surge, and in preparation for turning off the system, the pilot moved the power lever aft to reduce the power setting and delayed lowering the aircraft’s nose to maintain airspeed, resulting in a stall warning and subsequent collision with water.

The ATSB also found that Experience Co’s engine power loss checklist instructed pilots to significantly reduce power in preparation for deactivating the engine limiting system, but did not specify a minimum safe height at which to do so. This increased the risk of a loss of control and/or ground collision. 

Further, the ATSB found that the operator's weight and balance calculation for the accident flight did not include the bench seating weight or moment, and the loadmaster did not load parachutists in positions used for the calculation of the centre of gravity, therefore, although it did not contribute to the accident, the weight and balance was inaccurate for the intended flight. Additionally, the software used to calculate aircraft weight and balance did not provide a warning if individual aircraft zones were overloaded.

Finally, the ATSB found that Experience Co did not ensure sport parachutists received essential safety information about emergency exits, restraints and brace position, prior to take-off. 

What has been done as a result

At the time of writing, Experience Co was re‑developing its sport skydivers safety video to include emergency procedures. Additionally, the following proactive safety actions have been taken:

• A safety communique was developed and circulated at each drop zone reminding parachutists to be seated in accordance with their manifested location.
• Chief instructors, drop zone safety officers and loadmasters were reminded of the loadmasters’ responsibilities to ensure parachutists were seated in accordance with the weight and balance calculation.
• Skydive Operations Manual was amended to clarify the loadmasters’ responsibilities.
• Additional training was provided for manifest staff.
• A fleet-wide audit was undertaken to ensure all aircraft had accurate basic empty weight figures.
• A prompt was added to the internal reporting software to confirm an entry has been made to the aircraft’s maintenance release when submitting a maintenance‑related internal safety report.
• Briefings that cover essential safety information about emergency exits, restraints, and brace position, are now required annually by sport skydivers.
• Additional pilot training relating to the single red line/torque and temperature limiter malfunctions has been developed and was scheduled to be delivered to all pilots.
• Emergency exit signs in all aircraft were being assessed for compliance and effectiveness, and updated if necessary.
• Engineering personnel have undertaken specialised TPE331 Powerplant and Systems training.
• Information circulars were provided to company pilots about the proper defect reporting requirements using the aircraft maintenance release.
• Experience Co was updating advice as to the altitude at which seatbelts must be worn.
• Experience Co has developed Cessna 208 and Cessna 208B aircraft flight manual supplements, which outline the carriage of 17 parachutists and 21 parachutists respectively.
• An additional support bracket has been designed to be fitted to the end of the bench seats in aircraft and will be installed once formally approved.
• A new engine power loss checklist was developed in cooperation with the supplemental type certificate (STC) holder to be followed at or above 1,000 ft above ground level.

The Australian Parachute Federation (APF) has taken the following safety action:

• The APF will ensure skydivers and pilots review their aircraft emergency procedures on a regular basis. Recommended topics are likely to include:
  • general safety around aircraft
  • hot loading
  • door activation
  • achieving correct restraint fitment
  • emergency landings
  • brace position
  • emergency exit altitudes and which parachute to use
  • communication during an emergency
  • for coastal operations, life jacket use in a ditching.
• Each parachuting aircraft operator will conduct a thorough assessment of its aircraft to ensure single point restraints are properly installed, to prevent parachutists from moving outside their designated seating positions and to maintain the aircraft’s weight and balance.
• The APF will review global data on the use of dual-point restraints to gather insights from other national parachuting organisations regarding their experiences with this system.
• The APF examined aircraft flight manual wording of all aircraft currently conducting parachute operations in Australia to identify which aircraft would require a short-term CASA exemption to permit operations with the number of passengers onboard in excess of those able to occupy the normal seats under the type design. They identified 22 aircraft requiring an exemption, spanning 5 operators.
• The APF added the following statement to the participant waiver form: ’parachuting aircraft are not operated to the same safety standards as a normal commercial passenger flight’.

Finally, the Civil Aviation Safety Authority advised that it is developing the following:

• An exemption, for pilots or operators of parachuting aircraft who may be unable to comply with elements of the aircraft flight manual, is expected to be completed by mid‑2025.
  • CASA stated that it was satisfied that reasonable steps had been taken by the APF to ensure that a level of safety, commensurate with the risks involved in the parachuting activities in which participants engage, was provided to those participants in the interim while the exemption was being developed.
• An amendment to the Civil Aviation Safety Regulations Part 21 Manual of Standards to specify the standards required for the modifications made to parachuting aircraft. This proposed action is expected to be finalised by the end of 2025.
• Additional guidance to support aircraft owners and operators seeking to make an approved modification.

Safety message

The ATSB research report Avoidable Accidents No. 3 – Managing partial power loss after take-off in single-engine aircraft provides information to assist pilots to maintain aircraft control in the event of an emergency or abnormal situation after take-off. The report prescribed initial actions to be considered including:

• Lower the nose to maintain the glide speed of the aircraft. If turning is conducted, keep in mind an increased bank angle will increase the stall speed of the aircraft.
• Maintain glide speed and assess whether the aircraft is maintaining, gaining or losing height to gauge current aircraft performance.
• Fly the aircraft to make a landing, given the aircraft’s height and performance, and the pre-planned routes for the scenario.

If time permits, moving the power lever through the full range may result in increased power available to climb and/or create the time to diagnose the issue.

The ATSB SafetyWatch highlights the broad safety concerns that come out of our investigation findings and from the occurrence data reported to us by industry.

One of the safety concerns is reducing the severity of injuries in accidents involving small aircraft. This incident highlights the importance of passengers being appropriately briefed on the brace position and use of emergency exits. It also illustrates the higher injury risk associated with the carriage of parachutists, due to the increased number of occupants and inferior restraints compared to being secured in a certified seat.

The occurrence

Early on the morning of 20 October 2023, the pilot of a Cessna 208 aircraft, operated by Experience Co and registered VH-UMV, refuelled and inspected the aircraft in preparation for parachuting operations from Barwon Heads Airport, Victoria. No defects, including any fuel debris or contaminants, were identified.

The pilot’s first flight of the day was to carry 16 sport parachutists for a parachute jump from 15,000 ft. At about 0750 local time, the parachutists boarded the aircraft. The pilot recalled that the conditions were CAVOK,[1] with a light wind from the north. They taxied the aircraft to runway 36 for a northern departure. 

A review of OzRunways[2] flight data, recorded at 5-second intervals, showed the aircraft commenced the take-off roll at 0757. The pilot reported moving the power lever forward until the engine reached 100% torque, and then reducing the power slightly during the take-off roll. Camera footage showed that the aircraft became airborne at 0757:22.

The pilot reported that, as the aircraft climbed and the airspeed increased, they retracted one stage of flap passing through 85 kt and another at about 95 kt. At 0757:47, climbing through about 400 ft, the aircraft reached its maximum recorded ground speed of 95 kt. The pilot reported that as the aircraft approached 500 ft above ground level and they reached for the flap lever to retract the last stage of flap, they heard a reduction in engine noise, and felt a deceleration. 

The pilot initially associated the loss of power with activation of the torque and temperature limiter (TTL) (see the section titled Torque and temperature limiter), which they had previously experienced in that aircraft. Consistent with the previous TTL activation, the pilot expected the power to quickly return, and reported reducing power slightly to prevent the engine surging[3] as power was restored.  

The reduction in engine power, combined with the climb pitch attitude, resulted in the airspeed reducing and activation of the stall warning horn. On hearing the stall warning, the pilot lowered the aircraft’s nose to reduce the angle of attack[4] and increase the airspeed. 

At 0757:57 the aircraft reached the highest recorded altitude of about 700 ft at 88 kt ground speed and, 5 seconds later, had descended to 600 ft and the ground speed reduced to 71 kt, then to 69 kt 5 seconds later. This flight path was consistent with video camera footage of the aircraft’s flight path (Figure 1). At 0758:08 the ADS-B[5] data recorded a descent rate of 3,520 ft/m passing an altitude of approximately 400 ft.

Figure 1: VH-UMV flight path captured by the airport camera

The ATSB combined multiple images together to show the flight path of the aircraft as captured by a local video camera. Source: Airport operator, annotated by the ATSB

The pilot reported that, as the aircraft descended, they observed the engine torque indication reducing through approximately 30% and attempted to switch off the TTL in accordance with the operator’s Engine Power Loss checklist. Due to the aircraft’s low height above the ground, and the pilot’s assessment that there was an engine issue, the pilot then selected a field in which to conduct a forced landing.

The pilot turned to the loadmaster[6] seated beside them and called out ‘gear-up’, to alert parachutists to be ready to exit the aircraft. In response, the loadmaster began directing parachutists to open the roller door, secure their harnesses, and brace for landing. The roller door was opened, but not secured in that position.

The pilot selected a forced landing location in a clearing beyond a river. However, less than 1 minute after becoming airborne and unable to maintain altitude, the aircraft impacted the water short of the clearing, resulting in water entering the cabin and forcing the unsecured roller door closed. The aircraft continued onto the riverbank where the main landing gear detached, then travelled along the ground for about 50 m before coming to rest (Figure 2).

The pilot sustained minor injuries, 6 parachutists sustained serious injuries, 8 sustained minor injuries and 2 were uninjured. The aircraft was substantially damaged. 

Figure 2: VH-UMV flight path

Source: ADS-B exchange flight data overlaid on Google Earth and image of accident site provided by operator, annotated by the ATSB

Context

Pilot information

The pilot held a commercial pilot licence (aeroplane) and a current class 2 aviation medical certificate. On 19 April 2023, the pilot completed their gas turbine engine design feature endorsement and single engine aircraft flight review in a Cessna 208 aircraft.

At the time of the accident, the pilot had accrued approximately 220 hours of total flight experience, which included 38 hours on the Cessna 208 aircraft type. Of those hours on type, 36 had been accrued in the previous 90 days.

The pilot reported that they were familiar with VH-UMV, having conducted multiple flights in it prior to the accident flight. The pilot was also aware of operator-specific engine operating limitations for VH-UMV, and reported having previously experienced an engine surge at 5,000 ft (see the section titled Engine surging).

Aircraft information

Certification details

The Cessna Aircraft Company 208 (C208) is an all-metal, high-wing aeroplane with tricycle landing gear and designed for general utility usage. The aircraft type certificate data sheet (TCDS) A37CE described the C208 as an ‘11-place closed land monoplane’, and under the heading ‘No. of seats’, provided a centre of gravity range for seating for one or 2 pilot seat locations and referenced the current Pilot’s Operating Handbook (POH) and United States (US) Federal Aviation Administration (FAA) Airplane Flight Manual (AFM) for passenger seat arrangements for seats 3 to 11.

The C208 POH Section 2 – Limitations – Maximum passenger seating limits stated that up to 11 seats, including the pilot’s seat/s, may be installed.

VH-UMV, serial number 20800077, was manufactured in 1986 and first registered in Australia in 2005. At that time, the aircraft was issued 2 certificates of airworthiness, one for normal category[7] operations and one for restricted category[8] operations for the purpose of carrying people for parachute jumping.

Operating in the restricted category required several conditions, including removal of the cabin seats, compliance with a specific engineering order and readily visible restricted category placards, none of which were in place on the accident flight. Additionally, under Civil Aviation Safety Regulations (CASR) current at the time of the accident (CASR 91.845, 91.025, 135.030), aircraft operating in the restricted category were not permitted to conduct air transport operations (carriage of passengers or cargo for hire or reward). 

In 2017, the aircraft’s Pratt & Whitney PT6A-114 gas turbine engine was replaced with a Honeywell International Incorporated TPE331-12JR-704TT gas turbine engine that drove a 4‑bladed, constant‑speed, full‑feathering,[9] reversible[10] Hartzell HC-E4N-5KL propeller with hydraulically‑operated variable‑pitch control. The engine modification was completed under the Texas Turbine Conversions supplemental type certificate (STC) SA10841SC, with an associated AFM Supplement. Under the heading ‘Maximum passenger seating limits’, the AFM supplement stated ‘No changes’ (from the C208 AFM). 

The aircraft was also modified in accordance with STC SA01180SE, which increased the original maximum take-off weight from 3,628 kg to 3,792 kg. Both STCs were approved by the US FAA and therefore accepted in Australia and taken as having been issued by CASA in accordance with CASR Part 21 regulation 21.114.

Three modifications made to VH-UMV and other aircraft in the operator’s fleet were completed under engineering orders in accordance with the CASR Part 21 regulation 21.437 Grant of modification/repair design approvals—grant by authorised person or approved design organisation:

• ESE-C208-25-001—Rework of interior for parachute operations
• ESE-C208-25-007—Installation of parachute bench seating
• ESE-C208-95-003—Installation of Go-Pro cameras.

Torque and temperature limiter

VH‑UMV was fitted with a switch‑activated torque and temperature limiter (TTL) system designed to prevent these parameters exceeding specified limits. Where an exceedance of the allowable torque or exhaust gas temperature (EGT) was detected, the TTL computer restricted fuel flow to the engine. The maximum allowable fuel reduction of a normally-functioning bypass was about 68 L/hour (125 lbs/hour), resulting in a reduction of the torque output from 100% to about 62% (due to the approximate 25% reduction in fuel flow). 

Texas Turbine Conversions advised that, when functioning normally, the system would maintain the lower of the allowable torque or EGT limits and if the TTL bypassed the maximum allowable fuel, it would be felt immediately. In that case, the appropriate pilot response was to switch off the TTL.

The aircraft’s engine monitoring system included a single red line (SRL) controller, associated with the EGT limit. Like the TTL, the SRL was switch‑activated and deselection of the SRL also deactivated the TTL.

The allowable EGT limit was dependent on the phase of flight. Specifically, the operating margin from the EGT limit in the climb phase was reduced in the cruise phase. The phase was dependent on the position of the speed lever. Therefore, if the speed lever was moved aft during take-off or climb, the EGT limit also reduced and could result in activation of the TTL. The operator reported that the speed lever was fully forward throughout the short flight, and therefore the climb EGT limit applied. 

Operating limits

The AFM supplement for the Honeywell engine specified operating limits. With the SRL and TTL on, those limits included a maximum EGT of 650 °C, maximum 100% torque and maximum of about 101% RPM during take-off and climb. The supplement also provided an EGT table with limits for operating with the SRL off or inoperative, or ‘manual mode’. The limits were provided for operating at 100% RPM or 96% RPM based on the outside air temperature in 5 °C increments from −60 to +60 °C. 

The AFM defined take-off power as the lower of 100% torque or 650 ºC EGT (SRL ON), whichever is reached first at 100% engine RPM.

Engine surging

On 17 October 2023, the pilot submitted an internal safety report relating to an uncommanded engine surge, which they experienced at an altitude of approximately 5,000 ft. The pilot report stated:

Torque roll back for a split second, noticeable reduction in power and deceleration.

The pilot reported reducing the power then slowly increasing it while monitoring engine parameters in response to the event.

Although not recorded on the aircraft’s maintenance release (MR),[11] reportedly due to their transient nature, pilots submitted 7 other internal safety reports between July and October 2023 of engine surging in VH‑UMV, assessed as being due to the TTL. 

A review of maintenance recorded in VH-UMV’s engine logbook for the previous 12 months showed that the TTL controller was replaced ‘for fault isolation’ following the first reported surging occurrence on 3 April 2023. A further logbook entry on 18 September 2023 recorded that the EGT harness was replaced in response to reported engine surging at take-off power. 

The engine surging safety reports indicated troubleshooting test flights were also conducted. A series of test flights on 7 September 2023 was able to replicate the previously‑reported surging.  In addition, a test flight following the EGT harness replacement noted that the surging was still present. One of the experienced surges resulted in a torque value of 62% and fuel flow reduced by approximately 72 L/hour (128 lbs/hour). The MR current at the time of the accident identified that the aircraft operated over 90 flights prior to the next reported surge event on 17 October 2023. On that day, the aircraft operated 6 flights, and one surge occurrence was reported. According to the MR, 12 flights were conducted over the next 2 days (18–19 October), with no reports of engine surging submitted. However, the ATSB was also advised of an engine surge on 18 October, which was not recorded. 

The MR current at the time of the accident recorded 257 flights over 3 months, during which there were 6 reported surging events. That frequency illustrated the intermittent nature of the anomaly, which likely hindered troubleshooting.

As a result of the internal reports, on 21 July 2023, pilots were advised to operate VH-UMV under a set of unique operating conditions to avoid the TTL scheduling a significant bypass of fuel and subsequent notable drop in available power. These were limitations of 95% torque and 640 °C EGT. 

A review of the operator’s safety reports also identified that surging events were reported on 3 other company aircraft. For those aircraft, maintenance actions rectified the cause of each event and there were no subsequent surging events reported.

Minimum equipment list

Experience Co’s minimum equipment list (MEL) specified permissible unserviceable items with which the aircraft was permitted to operate temporarily under the stated procedures, conditions and limitations. The MEL included that both the SRL computer system and TTL ‘may be inoperative provided inoperative SRL system procedures and limits are observed’. In that case, it was also required that an MEL placard be fitted adjacent to the TTL or SRL switch for the inoperative system/s. There was no MEL placard for the TTL nor was it listed as inoperative at the time of the accident.  

Engine power loss checklist

The Texas Turbine Conversions AFM supplement provided checklists for engine failures, but not for partial engine power loss. The operator’s ‘Engine Power Loss’ checklist for the C208 with the Honeywell engine (Figure 3), required pilots to first control the aircraft by moving the elevator control forward to lower the aircraft’s nose if climbing. After completing initial checks, if the RPM was above 60% or the engine was surging, the pilot was to move the power lever to ½ inch (12.7 mm) forward of the flight idle position, in preparation for turning off the TTL, so as not to produce a transient exceedance of the EGT. 

Figure 3: Engine power loss checklist

Source: Aircraft operator 

Weight and balance

Aircraft moment arms

To enable calculation of the aircraft’s weight and balance, the C208 POH included a 2-place seating option, which divided the cabin into 7 zones (zones 0–6) (Figure 4). The flight manual supplement for the Texas Turbine Conversions STC did not include changes to the zones or seating configuration, therefore the POH applied. 

Figure 4: Cessna 208 Pilot’s Operating Handbook seating configuration

Source: Cessna 208 Pilot’s Operating Handbook, annotated by the ATSB

Accident flight weight and balance 

Prior to departure, a member of the parachuting operations team calculated the weight and balance for the proposed flight using the IBIS Technology flight planning module software (Table 1).[12] The moment arms from the POH were used for the calculations. Zone 6 was not used.

Table 1: Planned weight and balance for accident flight

The calculated weight and balance resulted in a take-off weight of approximately 3,719 kg and the aircraft’s centre of gravity located at 4,653 mm aft of the datum. To remain inside the operating limitations, the maximum allowable weight was 3,792 kg. Additionally, the aircraft needed to remain within the centre of gravity envelope, which had an aft limit of 4,680 mm and the forward limit varied with the operating weight. Each zone had a maximum allowable weight limit, and the maximum for zone 0 was 159 kg. However, the calculation software did not provide a warning to notify the user a zonal limit had been exceeded.

Information provided by the parachutists included the position they were seated at the time of the accident. Those positions did not match the original seating positions on the planned weight and balance sheet provided to the pilot prior to departure. The operator calculated a revised weight and balance based on the probable parachutist seating positions, which moved the aircraft’s centre of gravity 5 mm aft, although still within the allowable envelope (Table 2). It also showed that zone 0 was under the allowable weight limit.

Table 2: Revised weight and balance for accident flight

Aircraft basic empty weight

A weigh of VH‑UMV on 17 October 2017 identified that the aircraft’s basic empty weight was 1,889 kg in the single pilot seat configuration (Figure 5).

Figure 5: VH-UMV configuration on date of reweigh

The image meta-data showed the image was taken on 17 October 2017 – the reweigh date. Source: AeroWeigh.

The aircraft seating configuration at the time of the accident is shown in Figure 6.

Figure 6: VH-UMV cabin seating arrangement 

Source: Aircraft operator, annotated by the ATSB

The basic empty weight of the aircraft did not include the flooring, or the 36 kg bench seating installed under engineering order ESE-C208-25-007. The engineering order provided the moment arms and weights shown in Table 3.

Table 3: ESE-C208-25-007 Parachute bench seating options – bench seat weight and arm

Using the operator’s revised weight and balance calculation that reflected the likely positions of the parachutists, and the additional weight of the bench seating, the ATSB determined the probable take-off weight was 3,754 kg and the centre of gravity was 8 mm aft of the originally calculated centre of gravity (4,661 mm).

The operator subsequently weighed the aircraft’s jump mat, single point restraints, rubber matting, and portable oxygen tank. The total of these items was 30.2 kg, increasing the probable take-off weight to 3,784 kg.

Weight and balance implications 

Regarding the importance of accurate weight and balance, the FAA Pilot’s handbook of aeronautical knowledge stated:

An overloaded aircraft may not be able to leave the ground, or if it does become airborne, it may exhibit unexpected and unusually poor flight characteristics.

Changes of fixed equipment have a major effect upon the weight of an aircraft. The installation of extra radios or instruments, as well as repairs or modifications, may also affect the weight of an aircraft.

Loading in a nose-heavy condition causes problems in controlling and raising the nose, especially during take-off and landing. Loading in a tail-heavy condition has a serious effect upon longitudinal stability and reduces the capability to recover from stalls and spins. Tail heavy loading also produces very light control forces, another undesirable characteristic. This makes it easy for the pilot to inadvertently overstress an aircraft.

Recorded data

The ATSB obtained OzRunways and third-party ADS-B recorded data for the accident flight. That data was compared with flight data for the flight conducted by the same pilot in the same aircraft on 17 October 2023, which was the day the pilot reported engine surging at about 5,000 ft. The comparison did not show significant performance difference from take-off to about 500 ft between the 2 flights.

Although the aircraft had an engineering order to fit GoPro cameras, they were not in place for the accident flight. The operator reported that these were only used during the creation of promotional footage and not during day-to-day operations. There was also no video footage from inside the aircraft, but the airport operator provided video footage from cameras located at the airport. One of those cameras recorded the accident flight footage (Figure 1) and provided audio for analysis.

The recorded audio included the aircraft noise and the nearby road and wind noise. The camera was stationary, therefore as the aircraft departed its sound signature reduced. Analysis of the audio conducted by Honeywell found that the engine RPM was approximately 99% throughout the take-off and initial climb. However, the engine noise was not discernible from the background sounds recorded at the time of the reported engine surge.

Site and aircraft examination

Site assessment

The ATSB did not attend the accident site, but the aircraft operator and Victoria Police attended shortly after the accident and provided the ATSB with photos of the aircraft and cockpit. A review of the images showed that the: 

• flaps were fully retracted
• power lever was in the max reverse position
• speed lever was in the minimum position
• condition lever was in shutoff/feather position.

Those positions were consistent with the pilot’s reported actions to secure the engine after the impact. Additionally, one image appeared to show the TTL switch ON and the SRL switch OFF, indicating that the pilot may have inadvertently selected the SRL OFF instead of the TTL.

Engine and accessories assessment

The aircraft’s engine was recovered by the operator and sent to the Honeywell Investigation Laboratory in the US. On behalf of the ATSB, the US National Transportation Safety Board (NTSB) arranged independent oversight of the engine examination that was conducted between 3–5 January 2024.

Honeywell and the NTSB subsequently oversighted inspection and testing of removed components at various technical facilities. The Honeywell investigation report, provided to the ATSB and aircraft operator, detailed the observations and findings from the engine and associated component examinations, as follows.

The SRL and TTL were tested on 27 February 2024. Although some test points were not within the specified test tolerances, both units were found to be functional. However, further examination of the fuel bypass valve conducted by Woodward Inc. on 5 November 2024, resulted in a maximum bypass flow of 110 L/hour (194.5 lbs/hour), which exceeded the maximum flow test range of 68–74 L/hour (120–130 lbs/hour). At take-off power, a normal fuel flow was approximately 312 L/hour (550 lbs/hour). Therefore, if a bypass of 110 L/hour occurred during the accident flight with take‑off power set, the fuel flow would have reduced by about 35%. 

Initial inspection of the fuel bypass valve’s outer casing revealed impact markings (Figure 7). When the protective cover plate was removed, the pole associated with the impact side was found in contact with the armature. When a 4.5 kg (10 lb) force was applied to each of the poles, there was no visible movement. The armature was cut away from the spade to determine if the armature screws were loose. The armature screws were found to be suitably tightened, and the armature was not bent.

The findings of the inspection showed the out‑of‑limit test results were due to impact damage resulting from the accident. As such, the higher fuel bypass identified in the test was not considered to be contributory.

Figure 7: Fuel bypass valve

Source: Woodward Inc, annotated by the ATSB

The fuel control unit (FCU) was examined and tested between 26–27 March 2024. The FCU tested values were either within specified ranges or marginally outside of tolerance limits for new or overhauled components. The test results may have been affected by procedures for adjusting an in-service FCU defined in the engine maintenance manual. 

On 11 January 2024, a computed tomography scan of the propeller governor was conducted by Honeywell. Between 26–27 March 2024, the propeller governor was subject to functional testing by the manufacturer. While there were abnormalities identified with the magnetic pickup voltage and RPM maximum/minimum speeds, no contributing anomalies were noted. It was then disassembled, inspected and reassembled, followed by an additional functional test. The results from both functional tests were consistent with expected parameters of various operational modes.

The fuel pump was functionally tested on 2 May 2024, and found to be operating within specifications.

The Honeywell investigation found that the damage was indicative of an engine that was rotating and operating at the time of impact. It found no pre-existing condition that would have prevented normal operation. 

Photos of the propeller were provided to Hartzell for analysis. As the propeller was of composite material, on impact it fractured into parts rather than deforming the propeller shape. From the limited fragments that were retrieved, Hartzell concluded the blades were likely rotating under low power at the time of the accident.

The ATSB considered whether the pilot had moved the power lever to beta range, reversing the propeller, but Hartzell found it likely that the propeller was forced to a low pitch angle during the initial impact. 

Carriage of parachutists

Cabin configuration

The aircraft was configured for skydiving such that:

• the cargo door was replaced with a vertical sliding door (made of nylon, polycarbonate and aluminium)
• the passenger seats and lap belts were removed
• bench seating and 17 single point restraints were installed.

The restraints attached to the parachute harness and parachutists could be seated either on the bench seating or floor, facing toward the aft of the aircraft. 

The associated flight manual supplements for the parachute configuration were: 

• cargo doors removed kit
• in-flight openable cargo door
• in-flight opening of doors
• oxygen system
• skydiving jump light
• external mounted GoPro cameras.

Aircraft modifications

Classification of design changes 

CASA stipulated regulations for modification of an aircraft from the original manufacturer specifications. CASA Advisory Circular (AC) 21-12 Classification of design changes provided different processes for modifying aircraft, depending on the type of change being made. These changes were classified as either major or minor.

A minor modification was anything that was not considered to be a major modification and could be completed by a CASA-authorised person under CASR Part 21.M. Any modification with a significant effect on airworthiness – structural, weight and balance, systems, operational or other characteristics, were classified as major. Additionally, any alteration to the type certificate datasheet was classified as a major change. 

A major modification was further classified into a substantial change or a significant change. A significant change required a supplemental type certificate application to be completed with CASA’s involvement. A substantial change required a new type certificate application, which also involved CASA. The AC provided the following example of a significant change to a small aircraft:

Changes in types and number of emergency exits or an increase in maximum certificated passenger capacity.

The notes associated with that example were: 

Emergency egress certification specifications exceed those previously substantiated. Invalidates assumptions of certification. 

CASA advised that the modifications would be considered a major change if the number of persons was increased above that permitted by the aircraft type certificate data sheet. This was consistent with the US FAA Advisory Circular 105-2E – Sport Parachuting, which included: 

The approved number of skydivers that each aircraft can carry for parachute operations will most commonly be found on FAA Form 337, Major Repair and Alteration (Airframe, Powerplant, Propeller, or Appliance), used for field approvals, or an aircraft Supplemental Type Certificate (STC).

In its submission to the draft report, CASA advised that it considered that the legal basis for conducting parachuting flights with a greater number of passengers than the TCDS specified may be met if the aircraft was modified appropriately by a suitably authorised person and there was an associated aircraft flight manual supplement.

In determining whether the parachuting configuration modification was major or minor, the CASA‑authorised design engineer assessed that it was minor as it had no significant effect on:

• structure
• cabin safety
• flight
• performance or function of:
  • systems
  • propellers
  • engines or powerplant installation
  • environment.

The engineer also assessed that the design did not:

• alter airworthiness or operating limitations
• require an adjustment of the type-certification basis

Technical assessment of modifications 

Aircraft modifications must meet the airworthiness requirements of the aircraft’s certification basis. According to the type certificate data sheet, VH-UMV was certified under FAR 23 amendments 23-1 through 23-28. Modifications were required to comply with standards from that or subsequent amendments. Technical assessments of the modifications detailed in the engineering orders nominated FAR 23 amendment 62 as the certification basis for the parachuting configuration modifications, including the roller door, bench seating and oxygen system. 

The technical assessments included a design compliance matrix, with the following key comments by the design engineer of relevance.

Weight and balance

The engineering order was to include that:

It is the operator’s responsibility to accurately update the aircraft’s load data sheet to reflect the quantity and positioning of oxygen bottles as this may vary dependant on the number of parachutists on a given high altitude drop.

Structure

Standard aircraft hardware is used to secure items of mass installed as part of the parachute fit out modifications. This modification does not alter or effect the strength of the aircraft structure to support all normal aircraft loads. All materials & fasteners used as part of this design package have been selected to have adequate structural properties for their intended use.

Flight loads

The document package includes instructions to ensure the Cessna standard Flight Manual Supplement for operations with the cargo door open/removed is in the Flight Manual.

Oxygen

The engineer assessed the oxygen requirements for conducting flights above 14,000 ft in an unpressurised aircraft, stating:

…The operators (max) occupant capacity for the 208 & 208B model aircraft is x16 & x20 occupants respectively. As such these aircraft must be fitted with a minimum of 2x oxygen dispensing face masks if more than x15 occupants are carried…

Emergency landing conditions

Engineers assessed that the oxygen cylinder restraints were adequate in all load cases. They also rated the seats to at least 170 lb (77 kg) as required by FAR 23.785.

Regarding the installation of the oxygen bottle the engineers provided the following: 

…the seat base and surrounding structure is adequate to support the small increase in weight due to the installation…there is no risk of the installation coming loose and inflicting serious injury on the cabin occupants. 

Control systems

The design package included instructions for the removal of the copilot control wheel and column in accordance with the aircraft maintenance manual, to configure the aircraft for parachuting operations. There was no change to the design or functionality of the pilot's primary flight controls.

Doors

The number and arrangement of doors was not altered by the modifications. Regarding ‘vibration and buffeting’, the parachute door had a proven service history, with no reported issues since the design was originally implemented in June 2012. Further, the roller-style parachute door was commonly installed on parachuting aircraft and Cessna had an approved roll-up door as part of the production standard design. 

Operation of the roller door was ‘simple and obvious’, easily operable from inside and outside the aircraft. The door was held in place by gravity and friction and could not be accidentally opened. Decals specific to the operation of the parachute roller door were installed. 

Seats and restraints

The single point restraints for the parachutists were previously approved for use by ‘Air Safety Solutions’. 

The aircraft certification did not require dynamic testing of the seats and, although the bench seating was not tested, the design engineer referenced FAA AC 105-2E Sport parachuting, which stated: 

1. Straddle benches can offer more occupant crash protection than floor seating since they can be designed to provide significant vertical energy absorption.

Emergency exits

For reference, FAR 23.807 required:

In addition to the passenger-entry door, for an airplane with a total passenger seating capacity of 16 through 19, three emergency exits, as defined in paragraph (b) of this section, are required with one on the same side as the passenger entry door and two on the side opposite the door.

(b) Emergency exits must be movable windows, panels, canopies, or external doors, openable from both inside and outside the airplane, that provide a clear and unobstructed opening large enough to admit a 19-by-26-inch ellipse. Auxiliary locking devices used to secure the airplane must be designed to be overridden by the normal internal opening means. The inside handles of emergency exits that open onward must be adequately protected against inadvertent operation. In addition each emergency exit must:

• be readily accessible, requiring no exceptional agility to be used in emergencies;

• have a method of opening that is simple and obvious;

• be arranged and marked for easy location and operation, even in darkness;

• have reasonable provision against jamming by fuselage deformation; …

(c) The proper functioning of each emergency exit must be shown by tests

The design engineer commented that there was no change to the number of emergency exits and that the ‘steps, handles, bench seats etc. installed for this modification met the requirements for egress in an emergency as specified by this regulation’. Additionally, as there was no change to the door functionality or positioning, no additional emergency testing was required.

The unmodified rear right passenger door met the requirements of the regulation in that a 19" x 26" (48 x 66 cm) ellipse may be passed through the door un-obstructed. However, the rear right bench seat extended across the door at a height of 10” (25.4 cm). The design engineer commented that access to the door handles/operation and decals was not obstructed, and no exceptional agility was required to exit through that door in an emergency.

The roller door was also required to meet the emergency exit criteria, including ‘reasonable provisions against jamming by fuselage deformation’, and that ‘proper functioning of each emergency exit must be shown by tests’. However, this was not documented. 

The parachuting configuration detailed in the engineering orders enabled seating and single-point restraints for 17 parachutists, in addition to the fitted pilot seat and 5-point restraint. The design engineer had not intended to explicitly increase the seating capacity above the 11 specified in the TCDS, as the number of parachutists that could be carried was an operational consideration. The design engineer provided comment on a technical assessment provided to CASA in 2017 regarding maximum passenger seating configuration, that the aircraft operator’s understanding was: 

it is the pilots [sic] responsibility to ensure the aircraft is loaded within the weight and balance and centre of gravity limitations of the aircraft at all times. From these calculations the maximum safe number of parachutists to carry on the Cessna 208 Caravan is 17...

Regulatory requirements 

Part 105 of the CASR came into effect in December 2021 and set out the operational requirements for aircraft used to facilitate parachute descents. Civil Aviation Order (CAO) 20.16.3 paragraph 15 Carriage of parachutists was in force at the time of the accident, and the following regulations were relevant to the aircraft parachuting configuration:

• CASR 91.200 Persons not to be carried in certain parts of aircraft permitted a person to be carried in ‘a part of the aircraft that is not designed to carry crew members or passengers’, if the aircraft was being operated for a parachute descent and met the Part 105 MOS.
• CAO 20.16.3 required parachutists to wear a seatbelt, shoulder harness or approved single point restraint (except when about to jump). Similarly, CASR Part 105 section 105.105 required parachutists who were not flight crew to be provided with a seatbelt, shoulder harness or approved single-point or dual-point restraint.

The Part 105 Manual of Standards (MOS) came into effect on 2 December 2023, 44 days after the accident, and specified requirements in greater technical detail. CASA advised that the Part 91 Manual of Standards will be amended to remove ambiguity about approved passenger restraints being permitted in lieu of seatbelts.

Maximum passenger seating configuration

In drafting CASR Part 105, the number of parachutists that could be carried was a significant point of discussion between CASA and the parachuting industry. 

In 2006, CASA proposed Civil Aviation Safety Regulation 105.140 paragraph 3.5.20 which stated:

Proposed CASR Part 105 seeks to provide clarity to the parachuting industry that operating a parachuting aircraft with more parachutists than the normal published aircraft seating capacity in passenger-carrying operations is acceptable, provided weight and balance and other manufacturer’s limitations for the aircraft are observed.

A subsequent notice of proposed rulemaking indicated that the following may be included in the proposed CASR Part 105.140 – Number of parachutists in aircraft: 

(1) A parachuting aircraft may carry more occupants than the maximum number that is specified in the aircraft’s flight manual only if the aircraft is loaded in accordance with the following requirements and limitations set out in the flight manual or the certification data for the aircraft: 

(a) the weight and balance requirements; and…

When the above proposed rule was not incorporated into draft CASR Part 105 or MOS, as detailed in meeting minutes of the technical working group that reviewed the 30 August 2022 draft Part 105 MOS, they proposed to meet with CASA’s Airworthiness and Engineering Branch to discuss:

possible options for parachuting aircraft to operate with seats removed, to carry more passengers than currently permitted by the aircraft’s type certificate or flight manual and regulatory support mechanisms for modifications (doors, handles etc.) that support safe parachuting operations. 

The ATSB was unable to determine whether this discussion took place, however no related changes were incorporated into the regulations or MOS, noting that the MOS had not come into effect at the time of the accident. 

In response to the ATSB’s request for clarification of CASA’s expectation for the number of parachutists that could be carried, CASA advised that:

• The legal basis for conducting parachuting flights with a greater number of passengers than the TCDS is met where the aircraft has been modified appropriately by a suitably authorised person and the aircraft’s flight manual has been modified accordingly.
• CASA has been aware for multiple decades that parachuting aircraft were carrying a maximum number of passengers greater than the TCDS maximum number of dedicated passengers.
• CASA understood that the increase in passenger capacity for parachuting aircraft was achieved by operators through legitimate aircraft modification processes that removed the normal passenger seats and modified the aircraft for parachute‑specific operations.
• CASA did not identify any immediate safety of flight issues.

In its submission to the draft report, CASA advised that it was ‘considering the issue of a legislative instrument to remove any doubt that an approved aircraft modification which replaces normal seating with appropriate alternative seating and restraint arrangements is explicitly permitted’.

Supplemental type certificate application

In April 2017, the design engineer applied to CASA on behalf of the aircraft operator for a supplemental type certificate based on the engineering order for the addition of bench seating. The STC application submitted to CASA included details and images of aircraft that already had modifications completed under an engineering order and did not include an increase in the seating capacity.

After several communications and iterations of the documents provided, in August 2017, CASA highlighted 2 areas directly related to safety of parachutists: the rear exit crashworthiness and the increase of maximum passenger capacity to 17.

In July 2020, the STC application was withdrawn by the applicant.

Other parachuting configuration supplemental type certificates

Cessna 182 models E to R­

In 1996, CASA issued STC-214 to the APF. The STC background explained the application was the result of a CASA ramp check, which identified that there were 6 persons on board without single point restraints while conducting parachute operations, where the TCDS stated it was a 4‑seat aircraft.

The STC assessed the floor loading capacity of the aircraft to carry 6 persons (including the pilot) for the purpose of parachute operations. It concluded:

The floor was analysed and substantiated for parachutist loads. The hard points for the approved single point restraints were determined, analysed and substantiated for parachute loads... The aircraft loading is such that no special loading system needs to be devised as the aircraft will always be within the approved centre of gravity range.

The original C182 TCDS 3A13 showed ‘No. of seats 4’.

The amended TCDS for the STC showed ‘No. of seats 1, Parachutist 5’.

Cessna 208, 208B

In 2018, the US FAA issued supplemental type certificate SA04352CH, which incorporated many similar modifications made to model 208 and 208B aircraft certified under A37CE. The modifications included the installation of:

• wind deflector
• benches
• external assist handle
• internal assist handle
• jump exit control light
• external step
• wind block (sliding parachute door).

The STC limitations and conditions included:

(3) This modification does not install Title 14 [US Code of Federal Regulations] CFR part 23 compliant seating and is therefore zero occupancy.

(4) The left and right hand benches are compliant as monuments and are not certified to carry any items of mass. Testing performed during certification would be sufficient for gust loading or seven evenly distributed masses of 215 pounds (97.5 kg) each…

Australian Parachute Federation

The APF is the peak body for the administration and representation of Australian Sport Parachuting. With the approval of the Civil Aviation Safety Authority, the APF:

• applies the standards of operation
• conducts competitions
• issues parachuting licences, certifications and instructor ratings
• conducts exams
• distributes publications to keep its members informed of events and safety standards.

The APF organisation had over 55 group members also known as member organisations, 3,000 licenced members, and engaged with the operators of nearly 100 aircraft conducting parachute operations. As detailed above, the APF held an STC for parachuting operations in Cessna 182 models E through R for parachuting 6‑person operations. The associated supplemental type certificate data sheet amended the aircraft configuration to 1 seat and 5 parachutists from the 4‑seat configuration stated on the type certificate data sheet.

Aircraft operators that conducted parachuting operations as a member of the APF did so in accordance with the APF regulations. This included adhering to the APF Jump Pilot Manual. The Jump Pilot Manual Version 01-2023, in force at the time of the accident, stated:

5.3.3 Loading – Balance/C of G

A parachuting aircraft may carry more occupants than the maximum number that is specified in the aircraft’s flight manual only if the aircraft is loaded in accordance with the following requirements and limitations set out in the flight manual or the certification data for the aircraft:

  (a) the weight and balance requirements; and

  (b) any other limitations related to the provision of: 

       (i) adequate structural support for restraint of occupants; or

       (ii) supplemental oxygen for the flight.

For paragraph 5.3.3 (b), the limitations do not include those that are solely related to the number of seats or seating positions that are, or are normally, fitted in the aircraft.

If an aircraft does not have a flight manual, then any information supplied by the manufacturer that relates to the matters mentioned above or is included in the aircraft’s airworthiness certificate, is taken to be the flight manual.

Balance must be a consideration for all aircraft involved in parachuting operations and can be especially critical during climb-out and exit, when changes occur. Know the operational limitations of your aircraft!

Under the Loadmaster’s supervision, the parachutists will normally load the aircraft in the reverse order of the exit.

The Jump Pilot Manual was accepted by CASA and CASA personnel reported having reviewed the manual. Regarding the wording that a parachuting aircraft could carry more occupants than the maximum specified in the AFM, CASA reported that they understood that only applied to Cessna 182 models E through R, for which the APF held a supplemental type certificate that permitted the carriage of 6 persons. CASA personnel also reported that the manual wording was ‘never intended to serve as a quasi-engineering approval’.

At the time of writing, CASA and the APF were engaged in ongoing discussions, including the carriage of occupants in excess of the number detailed in the TCDS without the necessary modification approvals.

Survivability

Passenger briefing requirements 

The CASA Multi-Part Advisory Circular – Passenger safety information, stated:

2.1.1 In addition to certification standards for the crashworthiness of the aircraft and cabin crew evacuation procedures, well-informed and knowledgeable passengers contribute to survivability in an aircraft accident or incident. There are multiple factors that affect survivability. Physical factors include adopting the correct brace position for impact, the correct use of seatbelts, as well as the location and operation of all emergency exits.

2.1.2 Accident investigations have shown that survival rates are improved when passengers are provided with accurate and effective information about the correct use of equipment such as seatbelts, and the actions they should take in a life-threatening situation such as how to adopt the brace position.

A pilot in command was in contravention of regulation 91.565 if an aircraft commenced a flight and the passengers had not been given a safety briefing and instructions as prescribed by the Part 91 MOS, unless:

(a)  the passenger has been previously carried on the aircraft; and

(b)  the passenger has previously been given a safety briefing and instructions in accordance with this regulation; and

(c)  in the circumstances it is not reasonably necessary to give the same safety briefing and instructions.

The CASR Part 91 MOS provided a list of items that must be covered in a passenger safety briefing and instructions before an aircraft takes off for a flight. Relevant to this occurrence, the list included:

(c) when seatbelts must be worn during the flight, and how to use them;

(f) how and when to adopt the brace position;

(g) where the emergency exits are, and how to use them;

(s) for a flight of a jump aircraft — the physical location(s) within, or on, the aircraft that the passenger must occupy during the flight in order to ensure the aircraft is operated within the aircraft’s weight and balance limits during the flight.

Operator’s safety briefing

The aircraft operator had 2 videos, one of which was shown to parachutists depending on whether they were conducting a tandem jump or a sport jump. The sport jump video was specific to the Barwon Heads operation and included:

• aircraft climb performance
• 17 single point restraints, which were to be worn up to 2,000 ft
• sport jumpers were to listen to the pilot in command in the event of an emergency
• location of the door securing clip (but not instructions for use). 

The video shown to tandem jump parachutists provided specific aircraft safety information including:

• how to approach the aircraft
• the use of single point restraints
• the location of fire extinguishers
• how to brace
• how to egress
• the requirement not to smoke
• the use of life jackets where required.

For the accident flight, the pilot reported that they did not provide a safety briefing, and multiple parachutists reported not having received a safety briefing prior to flight. There was no procedure in the operations manual that waived the pilot’s responsibility to provide parachutists with a safety briefing. The pilot reported that they understood that the drop zone safety officer ensured everyone was briefed on emergency situations before jumping and a video briefing was provided to tandem parachutists.         

The operations manual provided the following guidance for providing a safety briefing during an emergency landing with parachutists on board:

It will be the Load Masters responsibility to assist the pilot in ensuring;

1. Parachutists are briefed on and instructed to assume the BRACE position prior to touchdown.

2. Emergency Exits are opened and secured (where possible) prior to touch down.

3. Single point restraints are utilised by all occupants.

The aircraft also had a sign on the rear wall of the internal cabin, detailing the in-flight emergency plan (Figure 8). The sign stated that single point restraints were required as directed by the pilot and at all times below 1,500 ft, differing from the 2,000 ft stipulated in the sport jump video. 

The APF Jump Pilot Manual required that restraints were utilised by all occupants below 1,000 ft, or as directed by the pilot.

Figure 8: In-flight emergency plan

Source: Victoria Police and the aircraft operator

Parachutist preparedness

After the accident, in response to an ATSB survey, parachutists reported a lack of awareness of how to brace and the location of emergency exits that were available if the main roller door became damaged and unavailable for use in an evacuation. On this occasion the clip that secured the roller door in the open position was not used, which resulted in it closing on impact. Fortunately, the parachutists were still able to successfully evacuate the aircraft via that door. As detailed further below, several of the parachutists also reported that their restraints were not taut prior to the ground collision.

Some parachutists recalled receiving aircraft-specific emergency information during their initial parachuting training. However, in some cases, several years had passed without receiving a refresher. Furthermore, some had conducted their initial training on different aircraft types.

Injuries and seating positions

The pilot wore a 5-point restraint, and the 16 parachutists each had a single-point restraint attached to their parachute. The probable seating arrangement at the time of the accident was determined based on the recollections of parachutists who responded to ATSB’s request for information (Figure 9). There were 4 parachutists seated on the floor, 4 on the left bench seat and 8 on the right bench seat. The parachutists were facing aft and those on the bench seats were seated between each other’s legs. 

Injury information was obtained for the pilot and 14 of the 16 parachutists, with the other 2 assumed to have no injuries (Table 4). The injury mechanisms included deceleration, flail and impact with the aircraft or other occupants.

Figure 9: Seating positions

The seating positions in the image are referenced in Table 4: Injuries sustained. Source: Texas Turbines Cessna 208 pilot operating handbook, annotated by the ATSB

Table 4: Injuries sustained

The single point restraints could not be adjusted, but an occupant could potentially position themselves such that the restraint was taut. Nine parachutists provided information about the tightness of their restraint; 7 reported their restraints were loose and 2 reported tight restraints. Of those with loose restraints, 3 sustained minor injuries and 4 sustained serious injuries. Of the 2 parachutists who reported having tight restraints, one sustained minor injuries and the other sustained serious injuries.

Of the 4 parachutists seated on the floor, 2 sustained serious injuries, one sustained minor injuries, and another was reported to have been uninjured. The other serious injuries were sustained by 2 parachutists on the left bench seat and one on the right bench seat. 

The parachutist who sustained the most injuries of the highest severity was at the front of the left bench seat. As that bench seat did not have a seatback, the parachutist came off the forward end of the bench between the bench and pilot seat and contacted the back of the pilot’s seat and/or ladder adjacent to the seat. The injuries were likely also increased by the mass of the 3 other parachutists on that bench moving forward during the impact sequence. 

The ATSB compared the injuries sustained by the pilot and parachutists of VH-UMV with those involved in 2 survivable accidents involving C208 aircraft, assessed as likely to have been subjected to similar impact forces (AO-2016-007 and AO-2024-001). In the 2 comparative accidents, some of the occupants sustained minor injuries while others were uninjured. The pilot and front seat passengers had 5-point restraints, and in the 2016 accident the other passengers wore lap belts. In the more recent accident, the other passengers wore 3-point restraints.   

ATSB investigation AO-2014-053 found that single point restraints were less effective than dual restraints in mitigating injury for parachutists. This was consistent with the US FAA’s technical report – Evaluation of Improved Restraint Systems for Sport Parachutists, which found that dual straps attached to the parachute harness provided better restraint and produced less flailing and bending of the body than single point restraints (FAA 1988). The following loading of aft‑facing passengers was found to increase restraint effectiveness:

• the person most forward in the cabin should be leaning against a bulkhead or other substantial support to limit flailing and head impact.

• each parachutist’s restraint should be anchored to the floor aft of his/her pelvis (relative the aircraft’s orientation) at a point on the floor near the middle of the thigh. The restraint should be taut to reduce forward motion, and the loads transmitted to the person behind.

• the proper brace for impact position would be to lean toward the front of the aircraft onto the person or bulkhead behind them.

The US FAA AC 105-2E Sport parachuting also stated that single point restraints were ‘not very effective’, and that dual point restraints offered ‘superior restraint’. 

The ATSB assessed that the increase in number and severity of injuries of the parachutists compared to passengers seated and restrained in seats, was probably a result of single-point restraints being less effective and less cushioning due to being seated on the floor or bench.  

Related occurrences

National Transportation Safety Board Special investigation report

The US National Transportation Safety Board (NTSB), Special investigation report on the safety of parachute jump operations (2008), found that between 1980 and 2008 in the US, 32 accidents involving parachute aircraft resulted in fatal injuries of 172 people, most of whom were parachutists. Acknowledging risks associated with parachuting, the report stated:

Although parachutists, in general, may accept risks associated with their sport, these risks should not include exposure to the types of highly preventable hazards that were identified in these accidents and that the parachutists can do little or nothing to control. Passengers on parachute operations aircraft should be able to expect a reasonable level of safety that includes, at a minimum, an airworthy airplane, an adequately trained pilot, and adequate Federal oversight and surveillance to ensure the safety of the operation.

Of the 32 accidents, 8 involved exceedances of the aircraft’s weight and balance, and 21 resulted from inadequate airspeed or stall situations, and in 6 accidents, both were factors. There was one accident involving a Cessna 208, which resulted in 17 fatalities.

The report also acknowledged that parachuting is typically a revenue operation where a participant pays for a jump and receives the flight as part of that service, it stated:

Most parachute operations flights are operated under the provisions of 14 Code of Federal Regulations (CFR) Part 91 and are typically revenue operations; parachute jump operators provide the flights as part of their services to parachutists who pay to go skydiving, or parachutists pay dues for membership in parachuting clubs. The risks of parachuting are generally perceived to involve the acts of jumping from the aircraft, deploying the parachute, and landing; parachutists are aware of and manage these risks. However, a review of accident reports reveals that traveling on parachute operations flights can also present risks.

The report highlighted the potential for paying participants to be unaware of the risks they were accepting when they boarded a parachute aircraft.

The report identified the following recurring safety issues:

• inadequate aircraft inspection and maintenance;

• pilot performance deficiencies in basic airmanship tasks, such as preflight inspections, weight and balance calculations, and emergency and recovery procedures; and 

• inadequate FAA oversight and direct surveillance of parachute operations.

Recent accidents

The following 3 more recent accidents involved aircraft conducting parachuting operations and resulted in injuries to the occupants.

• Loss of engine power after take-off involving Cessna 208B, PH-FST, West of International Airport Teuge, Netherlands, on 25 June 2021 (2021062)

On 25 June 2021 at 0932 local time, a Cessna 208B with a pilot and 17 parachutists on board departed from International Airport Teuge. During the initial climb, the aircraft suddenly lost engine power after which the pilot made an emergency landing in a field close to a motorway. The aircraft was substantially damaged, and one parachutist sustained minor injuries.

• Accident involving GA8-TC-320 Airvan, SE-MES, Storsandskär, Västerbotten, Sweden, on 14 July 2019 (RL 2020:08e).

The purpose of the flight was to drop 8 parachutists from an altitude of 13,000 ft. On the drop run, the pilot lost control of the aircraft. The parachutists were unable to evacuate the aircraft resulting in fatalities of the 9 persons on board.

The investigation found that control of the aeroplane was probably lost due to low airspeed. Other contributing factors were that the aeroplane was unstable as a result of a tail-heavy loading, weather conditions, and a high workload in relation to the pilot’s knowledge and experience.

• Loss of control involving Cessna U206G, VH-FRT, Caboolture Airfield, Queensland, on 22 March 2014 (AO-2014-053)

On 22 March 2014, a Cessna U206G aircraft was being used for tandem parachuting operations at Caboolture Airfield, Queensland. At about 1124 local time, the aircraft took off from runway 06 with the pilot, 2 parachuting instructors and 2 tandem parachutists on board. Shortly after take-off, witnesses at the airfield observed the aircraft climb to about 200 ft above ground level before it commenced a roll to the left. The left roll steepened, and the aircraft then adopted a nose‑down attitude until impacting the ground in an almost vertical, left-wing low attitude. All the occupants on board were fatally injured. A post-impact, fuel-fed fire destroyed the aircraft.

The ATSB identified that the aircraft aerodynamically stalled at a height from which it was too low to recover control prior to collision with terrain. The reason for the aerodynamic stall was unable to be determined. Extensive fire damage prevented examination and testing of most of the aircraft components. Consequently, a mechanical defect could not be ruled out as a contributor to the accident.

A number of safety issues were also identified by the ATSB. These included findings associated with occupant restraint, modification of parachuting aircraft and the regulatory classification of parachuting operations.

Safety analysis

Introduction 

On the morning of 20 October 2023, the pilot of a Cessna 208, registered VH-UMV, commenced take-off for a planned climb to 15,000 ft to drop 16 parachutists. Passing about 500 ft on climb, the pilot detected a partial power loss, consistent with an abnormal activation of the torque and temperature limiter (TTL). The pilot reduced the power to prevent the engine surging, but the combination of low power and airspeed resulted in the aircraft colliding with water before continuing into a field.

Six of the parachutists sustained serious injuries and the pilot and 8 parachutists sustained minor injuries. The aircraft was substantially damaged.   

This analysis will discuss the TTL activation and response actions. The aircraft’s seating configuration, weight and balance and occupant safety will also be examined. Additionally, the analysis will consider the number of parachutists on board, and operational guidance from the Australian Parachute Federation manual approved by the Civil Aviation Safety Authority (CASA).

Operator’s prescribed actions  

Normal operation of the TTL permitted reduction in the fuel flow to the engine to maintain the lower of 100% torque or 650 °C nominal exhaust gas temperature (EGT). However, the TTL manufacturer advised that the limiter was capable of restricting fuel flow sufficiently to reduce the maximum power to about 62% torque. A noticeable power reduction, followed quickly by a power increase, had been reported by the operator’s pilots as engine surging events associated with the TTL. However, maintenance actions had been unable to identify or resolve the cause of 6 reported engine surging events in VH-UMV over a 5‑month period.  

Unable to resolve the intermittent excessive TTL response, the aircraft operator had advised pilots to limit torque to 95% and EGT to 640°C to prevent TTL activation. Although well intentioned, that was contrary to the aircraft flight manual supplement, which defined take-off power as 100% RPM and 100% torque or 650°C EGT, whichever was reached first. The operator had not assessed the TTL and single red line (SRL) systems as inoperable, which would have required pilots to manually ensure torque and temperature limits were not exceeded. Power reductions resulting from TTL activations were reported to be momentary and power returned to the previous level after the torque or EGT limit reduced below the limit.

Additionally, in the absence of an aircraft manufacturer’s checklist for partial power loss, the operator had created an engine power loss checklist. The first item was to immediately move the elevator control forward if climbing to prevent airspeed decay. After other initial actions, the checklist then instructed pilots to significantly reduce power if the engine RPM was above 60% or surging, in preparation for switching off the TTL. While that was intended to ensure engine limits would not be exceeded when the pilot subsequently reintroduced power, the operator did not specify a minimum height at which it was appropriate for a power reduction to be made.

Such a significant power reduction close to the ground increased the risk of a loss of control and/or ground collision.  

Pilot actions

At the commencement of the take-off roll, in accordance with normal and the manufacturer’s procedures, the pilot reported applying full power – initially reaching 100% torque for take-off, before reducing power slightly in an attempt to remain under the operator‑specific torque limit of 95%. Whether the torque or temperature limit were reached during the initial climb could not be determined as these parameters were not recorded. However, the pilot detected a power reduction consistent with an abnormal TTL activation. 

 As shown by previous safety reports, in the event of TTL activation, the maximum power available may have been approximately 62%. Such a significant power reduction would have required the pilot to lower the aircraft’s nose attitude to prevent an aerodynamic stall, consistent with the operator’s engine power loss checklist.

However, the pilot did not initially lower the aircraft’s nose, instead they moved the power lever aft, reducing the power setting. This was in accordance with the operator’s procedure in preparation for switching off the TTL. Although the as‑found switch positions indicated that the pilot may have inadvertently selected the SRL switch instead of the TTL, in either event the TTL would have been deactivated. However, as the pilot had not lowered the aircraft’s nose, the aircraft approached an aerodynamic stall, and the stall warning horn sounded.

In response, the pilot lowered the aircraft’s nose and, due to the low height above terrain, low airspeed and low power, searched for a suitable field for landing. Although the pilot only reported reducing the power slightly, as the post-accident inspections found the engine was capable of producing normal power, and there were no pre-existing conditions that would have prevented normal operation, the low power was likely a result of the pilot reducing power to a level insufficient to maintain height in the climb attitude, and not restoring it.  

At the low height above the ground at which the power loss occurred, the above factors led to the collision with water. 

Weight and balance

The aircraft had all the aircraft’s certified seating removed other than the pilot’s seat, following which the aircraft was weighed, and a basic empty weight established. However, that weight did not include the bench seating, parachute restraints, floor matting or oxygen bottles which were fitted to the aircraft at the time of the accident. Although the weight and moment arm of the bench seating had been provided with the engineering order, it was not accounted for in the IBIS Technologies weight and balance calculation software used by the operator.

As a result, the bench seating and other aircraft fixtures were not accounted for in the accident flight weight and balance calculation. Additionally, parachutists did not sit in the positions used for the weight and balance calculations for the accident flight. Therefore, the calculated weight and balance was inaccurate.

Although the operator’s post-accident calculations found that the aircraft was almost certainly operating within the weight and balance limitations throughout the flight, an accurate weight and balance assessment prior to take-off to ensure the flight will operate below the maximum take-off weight is essential for the structural integrity of the aircraft. Operating outside the centre of gravity limits increases the risk of a loss of control. Exceeding weight and balance limitations has previously resulted in fatal accidents involving aircraft conducting parachute operations.

IBIS Technologies flight planning module

When conducting post-accident weight and balance calculations using the operator’s IBIS Technologies flight planning module, the ATSB identified that, while warnings were provided when the aircraft was outside the overall weight or centre of gravity limit, there was no warning when the weight for a zone within the cabin exceeded the limit. This increased the likelihood of an aircraft being loaded contrary to zone limitations. 

The lack of an alert did not contribute to this accident and, as noted above, the aircraft was not loaded in accordance with the planned overall or zonal distributions. However, the software used to calculate the aircraft weight and balance was used by many operators and overloading a zone limit could result in damage to the aircraft.

Safety briefings

To maximise survivability in the event of an emergency, pilots are required to ensure aircraft occupants receive a safety briefing and instructions including in the correct use of restraints, emergency exits and adopting the brace position. However, a pilot is not required to brief passengers on every flight, if they have previously been on the aircraft and are likely to be familiar with safety information. 

The pilot understood that this responsibility had been delegated to the drop zone officer and that the parachutists had received the required safety briefing and information. However, there was no record of which parachutists had been briefed or when. Additionally, as none of the parachutists on board were tandem jump parachutists, they were unlikely to have viewed the operator’s video that included use of single point restraints, how to brace or exit the aircraft in the event of an emergency.

Although some of the parachutists on board had previously received a safety briefing, it had not necessarily been in the accident aircraft type or recently. Additionally, an ‘in-flight emergency plan’ printed on the rear of the cabin advised parachutists to remain seated with single point restraints attached and brace for an emergency landing when below 500 ft, but did not specify how to brace or exit the aircraft. As a result, some of the occupants were unaware of essential safety information regarding brace position and emergency exits. 

Although the aircraft’s roller door closed on impact and water entered the cabin, all 17 occupants evacuated with no difficulties reported. The ATSB was unable to determine whether the absence of a safety briefing increased the severity of the injuries sustained by parachutists. However, adopting the correct brace position for impact, the correct use of restraints, and knowledge of the location and operation of all emergency exits, are factors demonstrated to increase survivability.

Seating configuration

The operator routinely conducted parachuting operations in Cessna 208 aircraft with the pilot and up to 17 parachutists on board. This was based on the CASA-accepted Australian Parachute Federation Jump Pilot Manual, which stated that the aircraft could carry as many parachutists as there were restraints and provided the aircraft was operated within the weight and balance limitations.  

The aircraft’s cabin was configured with a roller door, oxygen system, bench seating and single‑point restraints for parachuting operations under an engineering order by a CASA‑authorised person. Although the configuration nominally provided restraints and seating (including on the floor) for up to 17 parachutists, this was not formally documented in the aircraft flight manual or a supplement. The engineer also assessed and modified the aircraft to supply oxygen for 16 occupants to meet the operator’s requirements of their intended operation.

CASA assessed that increasing the number of persons carried above that stated on the type certificate data sheet (TCDS) required a supplemental type certificate (STC) as it was a major modification. In this case the TCDS stated that the aircraft had a maximum seating capacity of 11, but the aircraft was modified to supply oxygen for an intended 16 occupants. As such, the CASA‑authorised engineer incorrectly assessed that the modifications they were approving were minor and conducted them under engineering orders. The ATSB considered whether conducting the modifications in that manner increased safety risk.

As part of the assessment of an STC application for the same modifications submitted by the design engineer in 2017, CASA questioned the modified rear exit crashworthiness and increased number of occupants. Specifically, it was noted that the effect of increased occupancy on speed and ease of emergency egress had not been established, nor had it been demonstrated that the roller door would be unlikely to jam in the event of fuselage deformation.

As that STC application was never finalised, the safety of egress via the modified exit was not verified. However, in this accident, all the occupants evacuated the aircraft through the roller door after impact. As such, while the STC process was not followed when modifying the aircraft, there was no evidence that it increased the safety risk on this occasion. Additionally, CASA advised that the legislative requirements would likely be met if a modification conducted by an authorised person (under an engineering order) included an associated aircraft flight manual supplement.

The expectation for parachuting operations was that the parachutists would jump from a planned height, or be able to exit the aircraft in the event of an emergency when above a safe height. However, they would be inside the aircraft during take-off, at low level, and if unable to exit in the event of an emergency. In those phases of flight or conditions, increasing the number of occupants increased the number of people exposed to the risk of harm in the event of an accident. In this accident, as the aircraft was too low for parachutists to exit airborne, 15 of the 17 occupants sustained injuries, some of which probably occurred due to impact with each other.

Although the parachuting configuration was assessed as compliant with the required airworthiness standards, parachutists were exposed to greater risk of harm than if they were passengers in certified seats with adequate restraints. Those seated on the floor did not have the benefit of a seat to absorb impact forces and the bench seating had not been shown to optimally absorb impact forces. Additionally, the lack of a seatback on the left bench seat likely increased the injuries sustained by the forward-most parachutist seated on that side. The parachutists were also using single-point restraints, demonstrated to be less effective than dual restraints. 

Findings

From the evidence available, the following findings are made with respect to the partial power loss and collision with terrain involving Cessna 208, VH-UMV near Barwon Heads Airport, Victoria on 20 October 2023.

Contributing factors

• Experience Co’s engine power loss checklist instructed pilots to significantly reduce power in preparation for deactivating the TTL, but did not specify a minimum safe height at which to do so. This increased the risk of loss of control and/or ground collision.
• Passing about 500 ft on climb, the power reduced likely due to abnormal activation of the torque and temperature limiter (TTL). Expecting the power to return quickly, and in preparation for deactivating the TTL, the pilot further reduced the power and delayed lowering the aircraft’s nose to maintain airspeed. This resulted in a stall warning and subsequent collision with water.

Other factors that increased risk

• The operator's weight and balance calculation for the accident flight was inaccurate as it did not include the bench seating weight or moment, and the loadmaster did not load parachutists in positions used for the calculation of the centre of gravity.
• The IBIS technologies software used to calculate aircraft weight and balance did not provide a warning if individual zones were overloaded.
• Experience Co did not ensure sport parachutists received essential safety information about emergency exits, restraints and brace position, prior to take-off. (Safety issue)

Safety issues and actions

Safety issue information 

Safety issue number: AO-2023-049-SI-01

Safety issue description: Experience Co did not ensure sport parachutists received essential safety information about emergency exits, restraints and brace position, prior to take-off.

Safety action not associated with an identified safety issue

Proactive safety action taken by Experience Co

Experience Co has taken the following proactive safety actions:

• A safety communique was developed and circulated at each drop zone reminding parachutists to be seated in accordance with their manifested location.
• Chief instructors, drop zone safety officers and loadmasters were reminded of the loadmasters’ responsibilities to ensure parachutists were seated in accordance with the weight and balance calculation.
• Skydive Operations Manual was amended to clarify the loadmasters’ responsibilities.
• Additional training was provided for manifest staff.
• A fleet‑wide audit was undertaken to ensure all aircraft had accurate basic empty weight figures.
• A prompt was added to the internal reporting software to confirm an entry has been made to the aircraft’s maintenance release when submitting a maintenance‑related internal safety report.
• Briefings that cover essential safety information about emergency exits, restraints, and brace position, are now required annually by sport skydivers.
• Additional pilot training relating to the SRL/TTL malfunctions has been developed and was scheduled to be delivered to all pilots.
• Emergency exit signs in all aircraft were being assessed for compliance and effectiveness, and updated if necessary.
• Engineering personnel have undertaken specialised TPE331 Powerplant and Systems training.
• Information circulars were provided to company pilots about the proper defect reporting requirements using the aircraft maintenance release.
• Experience Co was updating advice as to the altitude at which seatbelts must be worn.
• Experience Co has developed C208 and C208B aircraft flight manual supplements, which outline the carriage of 17 parachutists and 21 parachutists respectively.
• An additional support bracket has been designed to be fitted to the end of the bench seats in aircraft and will be installed once formally approved.
• A new engine power loss checklist was developed in cooperation with the STC holder to be followed at or above 1,000 ft above ground level.

Proactive safety action taken by IBIS Technologies

IBIS Technologies amended its software to include an alert that will be flagged to the staff member in charge of manifesting the flight load if a zone exceeds zonal weight limits.

Proactive safety action taken by the Australian Parachute Federation 

The Australian Parachute Federation (APF) has taken the following safety action:

• The APF will ensure skydivers and pilots review their aircraft emergency procedures on a regular basis. Recommended topics are likely to include:
  • general safety around aircraft
  • hot loading
  • door activation
  • achieving correct restraint fitment
  • emergency landings
  • brace position
  • emergency exit altitudes and which parachute to use
  • communication during an emergency
  • for coastal operations, life jacket use in a ditching.
• Each parachuting aircraft operator will conduct a thorough assessment of their aircraft to ensure single point restraints are properly installed, to prevent parachutists from moving outside their designated seating positions and to maintain the aircraft’s weight and balance.
• The APF will review global data on the use of dual-point restraints to gather insights from other national parachuting organisations regarding their experiences with this system.
• The APF examined aircraft flight manual wording of all aircraft currently conducting parachute operations in Australia to identify which aircraft would require a short-term CASA exemption to permit operations with the number of passengers onboard in excess of those able to occupy the normal seats under the type design. They identified 22 aircraft requiring an exemption, spanning 5 operators.
• The APF added the following statement to the participant waiver form: ’parachuting aircraft are not operated to the same safety standards as a normal commercial passenger flight’.

Proposed safety action by the Civil Aviation Safety Authority 

The Civil Aviation Safety Authority advised that it is developing the following:

• An exemption, for pilots or operators of parachuting aircraft who may be unable to comply with elements of the aircraft flight manual, is expected to be completed by mid‑2025.
  • CASA stated that it was satisfied that reasonable steps had been taken by the APF to ensure that a level of safety, commensurate with the risks involved in the parachuting activities in which participants engage, was provided to those participants in the interim while the exemption was being developed.
• An amendment to the Civil Aviation Safety Regulations Part 21 Manual of Standards to specify the standards required for the modifications made to parachuting aircraft. This proposed action is expected to be finalised by the end of 2025.
• Additional guidance to support aircraft owners and operators seeking to make an approved modification.

Glossary

Sources and submissions

Sources of information

The sources of information during the investigation included:

• the pilot and sports jump parachutists
• Experience Co
• Civil Aviation Safety Authority
• Australian Parachute Federation
• Victoria Police
• Textron Aviation
• Honeywell International Inc
• OzRunways
• Barwon Heads Airport
• Texas Turbine Conversions

References

Federal Aviation Administration (2023). Pilot’s handbook of aeronautical knowledge. FAA-H-8083-25C.

Civil Aviation Safety Authority (2022). Classification of design changes (advisory circular AC 21-12 v1.1), https://www.casa.gov.au/classification-design-changes, CASA, accessed 23 September 2024.

Federal Aviation Administration (1998). Evaluation of improved restraint systems for sport parachutists, https://libraryonline.erau.edu/online-full-text/faa-aviation-medicine-reports/AM98-11.pdf.

National Transport Safety Board (2008). Special investigation report on the safety of parachute operations, https://www.ntsb.gov/safety/safety-studies/Documents/SIR0801.pdf, NTSB/SIR-08/01.

Submissions

Under section 26 of the Transport Safety Investigation Act 2003, the ATSB may provide a draft report, on a confidential basis, to any person whom the ATSB considers appropriate. That section allows a person receiving a draft report to make submissions to the ATSB about the draft report. 

A draft of this report was provided to the following directly involved parties:

• the pilot and aircraft operator
• Australian Parachute Federation
• Civil Aviation Safety Authority
• Textron Aviation
• Honeywell International Inc
• Texas Turbine Conversions
• Bowden Engineering solutions.

Submissions were received from:

• the pilot and aircraft operator
• Australian Parachute Federation
• Civil Aviation Safety Authority
• Honeywell International Inc.

The submissions were reviewed and, where considered appropriate, the text of the report was amended accordingly.

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