What happened

On 28 April 2021, at 0830 Eastern Standard Time,^[1] a flight instructor and student pilot were conducting circuit training in a Guimbal Cabri G2 helicopter at Redcliffe Airport, Queensland.

The student completed one circuit before the instructor took over control of the helicopter to demonstrate another circuit. The instructor reported the controls felt slightly unusual and initially thought that may be due to the crosswind or their own control inputs at the time. The instructor turned the helicopter onto the crosswind then downwind legs of the circuit, before levelling off at 800 ft.

When the instructor attempted to level the helicopter, it did not respond to cyclic inputs and initially maintained the angle of bank (about 20° to the right), before a small increase in angle of bank and a significant nose-down pitch. The cyclic was full aft and left and the helicopter did not respond to instructor inputs.

The helicopter entered a nose-down descending right turn and the instructor broadcast a MAYDAY^[2] call. While moving the cyclic, the instructor regained control of the helicopter and conducting a shallow approach back to the airfield with no further control issues.

Post-flight inspection of the helicopter revealed the left cyclic locking collar was not secure, allowing the cyclic to disengage (Figure 1). The dual controls had been removed and reinstalled the previous day for a private flight. The position of the left cyclic locking collar was not noted prior to the flight and the right side cyclic was serviceable throughout.

Figure 1: Dual controls showing the left cyclic control locking collar

Source: Aircraft operator

Safety action

As a result of this occurrence, the aircraft operator advised the ATSB of the following proposed safety action:

• removal and installation of dual controls by engineers instead of pilots
• redesign of the dual control sign in/out register to mitigate confusion
• consider dual check sign-off for installation of dual controls
• raising a company safety alert to highlight the importance of removing distraction while engaged in safety critical tasks.

The operator assessed that the pilot installing the dual controls may have been distracted, as they were concurrently explaining the installation process to another pilot.

Safety message

This occurrence reinforces the importance of a thorough inspection of all visible flight control components and attachment points following maintenance and before flight.

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.

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1. Eastern Standard Time (EST) was Coordinated Universal Time (UTC) + 10 hours.
2. MAYDAY: an internationally recognised radio call announcing a distress condition where an aircraft or its occupants are being threatened by serious and/or imminent danger and the flight crew require immediate assistance.

What happened

On 11 April 2021, a flight examiner conducted an instrument proficiency check with a commercial pilot in a Vulcanair ^[1] P.68C aircraft, at an airport near Brisbane, Queensland. At 1000 Eastern Standard Time,^[2] as the aircraft was taxied to the apron after the flight, the pilot had difficulty controlling the aircraft’s direction and advised that the rudder seemed jammed.

A post-flight inspection revealed that the top rudder hinge had failed (Figure 1).

Figure 1: Rudder with failed hinge, inset shows failed hinge

Source: Aircraft operator 

Maintenance

The aircraft was being maintained in accordance with the Civil Aviation Safety Authority (CASA) maintenance schedule, which required that a periodic inspection be completed every 100 hours or 12 months, whichever came first. The last inspection had been conducted 26 flight hours prior to the occurrence.

The CASA maintenance schedule was detailed in Civil Aviation Advisory Publication (CAAP) 42B-1(1.1). This CAAP required that the flight control surfaces, including the hinge brackets, be inspected for ‘general condition’. It specified that inspection aids such as work stands, mirrors and torches should be used and that ‘surface cleaning of individual components may also be required’. Paragraph 6.7 specified that the procedures ‘prepared by the aeroplane manufacturer are to be used when performing an inspection required by this schedule’.

In 2015, Vulcanair released Service letter 23 revision 1[3] which has since been incorporated into the P.68C maintenance program. The service letter was an alert to all P.68C owners and operators, providing detailed instructions on how to inspect the hinges. In accordance with the manufacturer’s approved maintenance procedures, the inspection was to be completed every 200 flight hours or 1 year, whichever came first. As the Civil Aviation Safety Authority had not issued an airworthiness directive containing the information in Service letter 23, the service letter was not mandatory. The inspection detailed by Service letter 23 had not been completed on this aircraft.

Safety action

CASA’s Continued Operational Safety and Standards section has contacted the European Union Aviation Safety Authority (EASA) small aircraft section and advised them of the incident and two other defects of a similar nature.

The operator’s maintenance repair and overhaul company has submitted the service letter feedback to the aircraft type certificate holder.

CASA is progressing the project to reform the continuing airworthiness and maintenance regulations. This work is being managed under project SS05/01 and status updates are available on the CASA website. The proposed policies include significant improvements to the current regulations, including the rules involving the CASA maintenance schedule. Subject to priorities in CASA’s wider regulatory program, CASA anticipates making the new regulations in 2022.

The ATSB was informed that on the 21 October 2021, EASA released a Notification of a proposal to issue an airworthiness directive (PAD) 21-158: Stabilisers – Rudder hinges – inspection. This AD proposes to make an inspection of the upper rudder hinge mandatory, in accordance with Service letter 23, revision 2, dated 29 September 2021 and the associated aircraft maintenance manual.

Consultation on the PAD closed on 18 November 2021.

Safety message

The CASA maintenance schedule was intended for those aircraft listed in Civil Aviation Order 100.5 as having inadequate maintenance schedules. Although no Vulcanair aircraft were on that list, nothing precluded the aircraft being maintained in accordance with the schedule. For operators who maintain aircraft in accordance with the maintenance schedule, CASA’s Maintenance guide for owners/operators stated that:

Under [Civil Aviation Regulation] CAR 42V (1), because all maintenance is required to be carried out in accordance with the applicable approved data, you must still consult with the manufacturer’s maintenance manuals for the airframe, engine and propeller, as well as applicable literature such as service bulletins, for instructions on how to carry out inspections and corrective maintenance action.  

A manufacturer may issue service information, such as a service letter, to advise operators about a problem and introduce or clarify an inspection, procedure or new part to prevent the problem recurring.

In 2011, the ATSB investigated a similar occurrence,

Australian Civil Aviation Regulations 1988 (CAR) were being misinterpreted by some class B aircraft registration holders, to the extent that they believed that their aircraft was exempt from the manufacturer’s supplemental inspections when their aircraft was maintained using the CASA maintenance schedule. While the CASA maintenance schedule did not make any specific reference to the incorporation of the manufacturer’s supplemental inspections, it was a CAR requirement that all aircraft be maintained in accordance with approved maintenance data that, by definition, included those inspections.

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.

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1. Formerly Partenavia Costruzioni Aeronautics S.p.A. 
2. Eastern Standard Time (EST): Coordinated Universal Time (UTC) + 10 hours.
3. The original service letter was released on 1 December 2010.

What happened

On 18 April 2021, the pilot of a Cessna 172S aircraft was conducting a private flight from Jandakot Airport to White Gum aeroplane landing area (ALA), Western Australia with two passengers on board. Prior to departure, the pilot provided a safety briefing to the passengers including instructing the front seat passenger to remain clear of the aircraft flight controls.

After landing, the front seat passenger accidentally pushed the left rudder pedal causing the aircraft to veer left off the runway toward trees. The pilot attempted to steer to the right by applying right rudder, which was unsuccessful. The pilot then initiated a go-around. As power was increased, the aircraft turned further left, resulting in the left-wing colliding with a tree. The aircraft rotated through 180° before coming to rest (Figure 1). The two passengers sustained minor injuries and the aircraft was substantially damaged.

Figure 1: Accident site

Source: Aircraft operator

Safety message

This accident highlights the importance of the passenger in the front seat of a dual control aircraft remaining clear of the flight controls (Figure 2). If there is any doubt about a passenger being able to comply with briefing instructions, consideration should be given to seating them in the rear seat.

Figure 2: Cessna 172 dual controls

Source: pinterest.dk

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.

What happened

On 6 April 2021, at about 0733 Western Standard Time,^[1] an Airbus A320 aircraft began its take-off roll on runway 06 at Perth Airport, Western Australia. About 60 seconds later, the A320 was airborne and climbing out ahead, as a Fairchild Industries SA227 aircraft, with two crew and 15 passengers on board, was cleared for take-off from the same runway. The crew reported that the atmospheric conditions at the time were ‘very stable’, with clear skies and a light and variable wind.

As the SA227 climbed through 1,500 ft, the crew experienced an uncommanded ‘strong roll to the left’ that reached approximately 45° angle of bank and required full opposite control input to recover from. A lull then briefly occurred followed by another uncommanded roll, this time to the right, reaching an angle of bank of 35° and again requiring full control input from the crew to recover. The crew reported that the airspeed remained constant at about 150 knots, and the rate of climb was unaffected throughout the occurrence. Following the recovery from the second uncommanded roll, the flight continued to its destination without further incident. No passengers or crew were injured in the incident, and the aircraft did not sustain any damage.

The aircraft operator assessed that the uncommanded roll experienced by the SA227 crew was the result of wake turbulence^[2] (Figure 1) generated by the A320 that had departed ahead. The very stable atmospheric conditions at the time of the incident contributed to the wingtip vortices generated by the A320 remaining in the SA227’s flight path longer than would otherwise have been anticipated

Figure 1: Wake turbulence generation

How an aircraft generates wake turbulence in flight, with associated wingtip vortices

Source: FAA (Advisory Circular: Aircraft Wake Turbulence, AC No: 90-23G)

Wake turbulence

A recent ATSB study, Analysis of wake turbulence occurrences at Sydney Airport 2021-2016, a Bayesian analysis, explains that

To minimise the risk to safety associated with wake turbulence, air traffic control separates aircraft arriving or departing from an airport using wake turbulence separation standards. These are time and/or distance-based measures that limit the separation of leading and following aircraft and are designed to reduce the likelihood and severity of wake turbulence occurrences.

This separation is based on an aircraft’s maximum certified take-off weight, which is used to place it into a Light, Medium, Heavy, or Super wake turbulence category (Figure 2).

Figure 2: Division of aircraft categories based on maximum take-off weight

Source: Airservices Australia (Aeronautical Information Publications)

ATC applies the required distance and time separation requirements between aircraft based on which wake turbulence category each aircraft belongs to (Figure 3).

Figure 3: Table of required wake turbulence separation between categories

Source: ATSB (Analysis of Wake Turbulence Occurrences at Sydney Airport 2012-2016)

The SA227’s maximum take-off weight was 7,484 kg and the A320’s was 77,000 kg. Due to the broad range of weights included, both the SA227 and the A320 fall into the Medium wake turbulence category, and as a result ATC is not required to apply wake turbulence separation between them. Despite this, there is a significant difference in size and weight between these two aircraft types, and as such there exists the possibility of a wake turbulence encounter such as that experienced by the SA227 crew.

The stable atmospheric conditions on the day also contributed to this occurrence. Wingtip vortices generated by an aircraft are subject to local winds which can displace them from the position in which they are generated (Figure 4). The stable atmospheric conditions reported by the SA227 crew allowed the wingtip vortices to remain stationary behind the A320, and in the SA227’s projected flightpath, longer than would otherwise have been expected.

Figure 4: Effect of wind of wingtip vortices

Source: FAA (Advisory Circular: Aircraft Wake Turbulence, AC No: 90-23G)

Safety action

The operator has advised the ATSB that a reminder of the hazards of wake turbulence will be included in a monthly safety newsletter and distributed to all flight crew.

Safety message

This incident serves as a reminder to flight crew of the hazards associated with wake turbulence, and the limitations of existing wake turbulence separation standards under some circumstances.

ATSB research has found that ‘wake turbulence separation standards will not completely eliminate the hazards associated with wake turbulence vortices’.^[3] Therefore, pilots are reminded that existing wake turbulence separation standards may not provide adequate protection against wake turbulence encounters in circumstances of a large size differential between two aircraft within the same wake turbulence category.

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.

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1. Western Standard Time (WST): Coordinated Universal Time (UTC) + 8 hours.
2. Wake turbulence: Turbulence due to wakes behind large aircraft with a powerful downward motion.
3. Analysis of Wake Turbulence Occurrences at Sydney Airport 2012-2016

What happened

On 21 March 2021, at about 2200 Eastern Daylight-saving Time,^[1] a Piper PA-31-350 aircraft was operating a scheduled freight flight from Moorabbin, Victoria to Devonport, Tasmania. On board was a pilot in command supervising a second company pilot.

During approach, when about 5 NM from Devonport Airport, the low boost pump and low fuel flow warning lights illuminated. The right engine stopped shortly after. The pilot in command confirmed the fuel selector was in the correct position and observed that the fuel gauges indicated three-quarters full, which was as expected. The pilot then attempted to cross-feed fuel from the left engine, which was unsuccessful. By this time, the aircraft was on mid-final and, once assured of making the runway, the pilot stopped troubleshooting and concentrated on landing the aircraft.

After landing, the pilot inspected the fuel cap, which appeared to be secured correctly. However, blue stains were evident on top of the wing consistent with fuel venting out of the fuel cap. The fuel system was subsequently inspected by maintenance personnel with nil defects found with the fuel cap and no blockages in the fuel tank vents.

The pilot later advised that the rubber bladder containing the fuel within the tank was sucked up against the top of the wing as the tank emptied, providing a false indication of the fuel remaining in the tank.

Safety action

As a result of this occurrence, the aircraft operator has advised the ATSB that brighter torches would be carried in the aircraft to ensure flight crew could see the fuel tank caps during night operations. The aircraft operator already had a policy for pilots to check fuel caps for venting after take-off.

Safety message

Fuel starvation happens when the fuel supply to the engine(s) is interrupted although there is adequate fuel on board.

This incident reinforces the need to:

• conduct a thorough pre-flight inspection ensuring all fuel tank caps are secured correctly
• determine the expected rate of fuel consumption prior to flight
• monitor fuel consumption during flight
• be fully familiar with the fuel system’s operation.

More information on fuel management can be found in the ATSB research report, Starved and Exhausted: Fuel management aviation accidents (AR-2011-112).

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.

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1. A Eastern Daylight-saving Time (EDT): Coordinated Universal Time (UTC) + 11 hours.

What happened

On 14 January 2021, the pilot of a Piper PA-30 aircraft planned to conduct circuits for the purpose of running the engines after a prolonged storage period. The pilot’s usual procedure had been to fill the aircraft tanks (to full) prior to flight. On this occasion, instead of filling the tanks, the pilot visually checked the quantity of fuel in the wing tanks and assessed it was sufficient for the planned flight.

A graphic engine monitor unit was installed in the aircraft but was reported to have reverted to factory settings following a flat battery. The pilot therefore deemed this an unreliable source of fuel quantity information.

Shortly after take-off on the fourth circuit, the left engine stopped due to fuel exhaustion. The pilot initiated a turn back to the runway. Once confident of making the runway, the pilot configured the aircraft for landing.

With limited manoeuvrability due to one engine inoperative, and the possibility of the right engine stopping at any moment, the pilot elected to land with a tailwind. This resulted in a higher ground speed on touchdown. The ground speed, combined with the wet grass surface, meant that the braking performance was insufficient to stop the aircraft on the runway remaining. The aircraft overran the runway into a wire fence resulting in minor damage to the nose and wings.

Safety action

As a result of this occurrence, the owner has advised the ATSB that they have made a calibrated dipstick to accurately measure the quantity of fuel in the wing tanks.

Safety message

This incident is a reminder to pilots to ensure sufficient fuel is carried for the proposed flight. The Civil Aviation Safety Authority advisory publication,

Case studies for pilots to learn about fuel management related accidents are documented in the ATSB publication Avoidable Accidents No. 5 – Starved and exhausted: Fuel management aviation accidents.

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.

What happened

On 29 January 2021, at 0655 Coordinated Universal Time, a multi-purpose vessel encountered heavy seas in the Southern Ocean. The 6-metre swell and confused sea state ^[1] caused the vessel to roll heavily, listing more than 30 degrees. As a result of this movement, several bundled wire restraints on battery racks failed and numerous batteries fell to the floor of the top deck battery room (Figure 1).  

Wires to the batteries were cut and at least two of the batteries short circuited internally between the cells. This resulted in a fire, which triggered an alarm on the bridge. The captain initiated the emergency response procedures and the fire was extinguished.

Figure 1: Battery room after the fire was extinguished

Source: Vessel operator

Battery racks

The battery room contained multiple shelved racks with large batteries secured to them. These racks used an L-shaped frame to prevent fore and aft movement, and metal brackets or bundled wires to prevent any lateral movement in the rack. The batteries that fell from the racks, including the two that had confirmed fire damage, were secured by bundled wire straps. These had been 

installed 5 months prior to the occurrence. The other batteries were secured to the racks by heavy metal brackets that bolted into the rack frame. Figure 2 depicts a battery secured with both types. The large brackets were the normal method of restraint and it could not be determined why they were not used to secure the more recently delivered batteries or why some batteries were secured by both types of restraints. The bundled wire straps proved to be inadequate in the heavy swell of the Southern Ocean.

Figure 2: Battery rack with both types of restraints  

Safe Work guidance

While there are no mandated standards for battery racks on ships, securing loose items prior to departure is a key principle of good seamanship. The Seacare Authority Code of Practice Approval 2018 - Health and Safety in Shipboard Work, including Offshore Support Vessels (paragraph 12.5) stated 'Batteries should be kept battened into position to prevent shifting in rough weather’. In this occurrence, the batteries were secured, although inadequately so for the prevailing conditions. The departure checklist used by the operator included securing loose items above deck in preparation for heavy weather and was completed by the crew.

Safety action

The operator of the vessel advised the ATSB they have taken the following safety actions:

• all battery rooms were checked for suitable sea fastening
• the bundled wire securing bands were immediately replaced with the original metal securing brackets or another equally robust arrangement
• damaged batteries were replaced as required
• a meeting with involved parties was held to discuss the lessons learned and corrective action.

Safety message

Although believed to be sufficient at the time of installation, the methods used to secure the batteries were inadequate for the conditions experienced in the Southern Ocean. At sea, particularly in heavy weather, unsecured items risk being damaged and may also pose a danger to the crew, or, as in this case, the safety of the ship. The risk to life associated with an emergency such as a major shipboard fire, is significantly increased when it occurs in heavy weather, far out to sea, where any possibility of assistance from ashore or from another ship is significantly reduced.

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.

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1. Confused sea state: A highly disturbed water surface without a single, well-defined direction of wave travel.

What happened

On 29 January 2021, the pilot of a Britten-Norman BN-2A-21 Islander prepared to conduct a charter flight from Horn Island to Saibai Island, Queensland, with three passengers. The pilot obtained a weather forecast for the planned route, which included the probability of isolated embedded thunderstorms, and weather reports from two pilots operating in the area. The pilot assessed that the conditions were suitable for the flight to be conducted and planned to operate under instrument flight rules.^[1]

About 20 minutes after departing Horn Island, while maintaining 7,000 ft and in instrument meteorological conditions,^[2] the aircraft entered an embedded thunderstorm cell and encountered moderate turbulence. The pilot slowed the aircraft to turbulence penetration speed and executed a 180° turn to exit the cell.

Once clear of turbulence, the pilot checked on the passengers’ welfare as they were visibly affected by the experience. There were no injuries. The pilot descended the aircraft until clear of cloud. The pilot then commenced a diversion to Yam Island, before electing to return the aircraft to Horn Island (Figure 1).

Figure 1: Aircraft flight path  

Source: FlightAware, annotated by the ATSB

Safety message

The primary protection against thunderstorm-related turbulence is avoidance. In the wet season in the tropics, thunderstorm cells should be avoided by large margins. The ATSB (2005) report, General Aviation Pilot Behaviours in the Face of Adverse Weather, identified that ‘weather-related general aviation accidents remain one of the most significant causes for concern in aviation safety’. Addressing this requires pilots to continuously evolve their decision making.

Thorough pre-flight planning, in-flight weather reports, local knowledge and reports from other pilots operating in the area can assist to build a picture of what is happening in the environment. Even with good preparation, as in this incident, an embedded thunderstorm cell may be difficult to see and avoid without on-board weather radar.

ATSB investigations AO-2017-102 and AO-2019-069 provide examples where flight into or near thunderstorms have resulted in damage to aircraft and the loss of life.

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.

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1. Instrument flight rules (IFR): a set of regulations that permit the pilot to operate an aircraft to operate in instrument meteorological conditions (IMC), which have much lower weather minimums than visual flight rules (VFR). Procedures and training are significantly more complex as a pilot must demonstrate competency in IMC conditions while controlling the aircraft solely by reference to instruments. IFR-capable aircraft have greater equipment and maintenance requirements.
2. Instrument meteorological conditions (IMC): weather conditions that require pilots to fly primarily by reference to instruments, and therefore under Instrument Flight Rules (IFR), rather than by outside visual reference. Typically, this means flying in cloud or limited visibility. 

What happened

On 28 January 2021, a student pilot was conducting a solo local training flight in a Cessna 152. The aircraft departed Bacchus Marsh, Victoria, with 35 L of fuel on board. As the aircraft was going into maintenance the next day, the student was advised by their instructor to return from the flight with minimum fuel remaining. The flight school’s policy stated that the required minimum remaining fuel was 19 L as a fixed reserve, and an additional 5 L fuel was to be allocated for taxiing. For the useable fuel on board, the policy and fuel planning figures would have allowed for 26 minutes of flight. The total recorded engine-run time for the taxi and flight was 1.2 hours.

The aircraft landed at Bacchus Marsh with 15 L of fuel remaining, which was confirmed when maintainers drained the tank the next day. 

Safety action

The flight school’s fuel policy is under review and a plan to further educate staff and students is being developed.

Safety message

This incident highlights the importance of clear communication between instructors and students. Instead of giving the student a timeframe, the instructor gave a fuel-remaining measurement, which is harder to gauge accurately, and led to the student using fixed reserve fuel. Additionally, other options should be explored to bring the aircraft to minimum fuel for maintenance instead of using a student on a solo training flight.

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.

What happened

On 15 December 2020, at about 1900 Eastern Daylight-saving Time,[1] the crew of a Leonardo AW139 helicopter were conducting the winch retrieval of three people stranded on a cliff near Childers Cove, Victoria. The crew comprised the pilot, aircrew officer and a paramedic.

The paramedic was winched to the ground and recovered the first stranded person. The aircrew officer then manoeuvred the paramedic and the first person into the aircraft cabin. To allow them to move into the aircraft seats, the aircrew officer winched out some cable to provide slack in the cable. During this winch-out procedure, the slack cable was dispensed onto the aircraft floor and out the cabin door. The aircrew officer was aware that the cable was outside the cabin, but not the length of cable that was outside the cabin, and the looped section was not visible. When the aircrew officer commenced the winch-in of the hook assembly, the cable failed (Figure 1).

The aircrew officer secured the loose end of the winch cable and the pilot landed the helicopter in a nearby carpark to assess the situation. It was found that the cable had looped around the right undercarriage shock absorber trunnion resulting in the failure of the winch cable and damage to several undercarriage components.

Figure 1: Reconstruction of cable fouling and severed winch cable hook assembly

Source: Operator

The helicopter was inspected on site shortly before last light by one of the operator’s engineers and was cleared to return to base. However, it was later determined that the damage to the undercarriage rendered the helicopter unserviceable.

Safety action

As a result of this occurrence, the operator has advised the ATSB that they have taken the following safety actions:

• A Safety Alert has been promulgated throughout the company to reinforce the importance of cable control during all phases of winching operations.
• All personnel have been reminded of the general safety philosophy of the company, which demands that safety related activities, including aircraft inspections and checks, are not rushed nor influenced by time pressures. Any activity should be stopped immediately if any person has any doubt about the safety in relation to a particular operation they are involved in.
• A learning package is being developed to facilitate sharing of the incident details and findings within the company and other helicopter emergency medical service operators.

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.

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[1]     Eastern Daylight-savings Time (ESuT): Coordinated Universal Time (UTC) + 11 hours.