Ditching

History of flight

Following an earlier flight from the mainland and a brief shutdown on a floating pontoon at Norman Reef, the Bell Jetranger II 206B departed in a south-south-east direction into the prevailing wind. On board with the pilot were four passengers scheduled for a scenic flight around Norman Reef and return to the pontoon. Immediately following the takeoff, the pilot initiated a right banking turn. While in the turn, with a quartering tailwind, the helicopter began an uncommanded yaw to the right. The pilot reported that he lowered the collective and pushed the tail rotor pedals left and right in an attempt to regain control of the helicopter. Following those actions, and after two complete 360-degree rotations to the right, the yaw abated. After a momentary pause, the helicopter again began to yaw to the right. The pilot broadcast a MAYDAY on CTAF frequency, armed and inflated the emergency flotation gear, and initiated a water landing. The helicopter impacted the water and rolled to the right. The pilot and three occupants successfully exited the helicopter unassisted. One passenger occupying the right rear passenger seat was momentarily trapped in the helicopter by her seatbelt, as the seatbelt release latch had become reversed. The pilot and onlookers from a nearby pontoon eventually assisted her from the helicopter. The helicopter sustained substantial damage.

Weather

The forecast for the area was for isolated showers along the seacoast with winds from the south-east at 15 knots, with broken Stratus 1000 to 2000 feet in showers. Observations of the weather at the nearby pontoon recorded at 0700 hours Eastern Standard Time indicated wind from the south-southeast at 15 knots with no cloud and a temperature of approximately 22 degrees Celsius.

Wreckage examination

All flotation bags of the emergency flotation gear activated upon selection. The helicopter had impacted the water with approximately 10 degrees nose-down attitude, little forward airspeed, and a slight right-bank. The advancing main rotor blade contacted the water causing separation of the main rotor hub and displacement of the main transmission. The retreating blade impacted and severed the tail boom, tail rotor controls, and the tail rotor driveshaft. The transmission-to-engine driveshaft, transmission upper deck, and forward engine firewall were also damaged following transmission displacement. The damage was indicative of at least partial drive train continuity at the time of impact. No pre-existing mechanical defect was discovered that would have resulted in loss of tail rotor control. It was determined that the helicopter was capable of normal operation prior to the accident.

Helicopter information

The Bell 206B II Jetranger helicopter was manufactured in 1973 and was first entered on the Australian Civil Register on 17 April 1973. The part number 206-016-201-133 tail rotor blades had been installed in March 1999. Those blades were longer length than the standard blades, with improved performance, and therefore believed to be less susceptible to loss of tail rotor effectiveness (LTE). The helicopter was last reweighed on 4 October 1996. The empty weight of the helicopter, according to the last weight and balance calculations of 20 May 2000, was 897.6 kilograms. The maximum allowable gross weight of the helicopter was 1,451 kilograms. The estimated takeoff weight using the May 2000 calculations was 1,357 kilograms. The helicopter's flight manual was not recovered to permit confirmation of the flight manual weight and balance documentation.

Personnel information

The pilot had a total of 1,281.3 hours on rotary wing aircraft, including 751.8 hours on type. He had recorded 114.4 hours on this particular helicopter. The pilot held a valid Commercial Pilot's License (Helicopter), Bell 206 type endorsement, and Class One medical certificate. The endorsement was issued on 15 November 1997. The pilot's last flight review was completed on 20 August 1999. He had completed a 0.3 hour basic introduction check ride with the company chief pilot on 11 April 2000. Thereafter, he accompanied other company pilots operating in the local area, until he was permitted to fly as pilot in command.

The pilot had been on duty for six hours leading up to the accident and had 15 hours off duty before the work period, including 8.5 hours sleep the night prior to the accident. He had flown this particular helicopter 5.2 hours the day before the accident, with a total duty time that day of 8.5 hours. He had a rostered day off two days prior to the day of accident.

Loss of Tail Rotor Effectiveness

The phenomena of LTE, also known as unanticipated right yaw, has been identified as a contributing factor in several helicopter accidents. According to United States Army testing, OH-58 series helicopters (the Bell 206 series is the civilian variant) have proven in the past to be susceptible to LTE under certain low speed manoeuvres. LTE is not related to a maintenance malfunction and is associated with single main rotor, tail rotor configured helicopters. LTE is a result of the tail rotor losing aerodynamic efficiency due to a combination of several factors. Those factors include main rotor vortex interference and tail rotor vortex ring state (related to airflow disruption over the tail rotor), helicopter weathercock stability, and the loss of translational lift. The regimes in which LTE may be encountered include low airspeed (less than 30 knots) when translational lift is lost or reduced, high power, and in the case of the United States designed helicopters, operating in a left crosswind or tailwind or with a high yaw rate to the right.

There is greater susceptibility for LTE on United States designed helicopters in right turns and more so in right turns overwater. This is especially true during flight at low airspeeds when the pilot is looking out the right window (not viewing the instrument panel) and is unaware of the airspeed dropping to a low value. The turn is commonly done with reference to the ground where the pilot attempts to keep a constant groundspeed by referencing ground cues. Flying overwater, the pilot does not have the visual cues available as when flying overland.

In turbine powered helicopters, the frame of reference for the engine power governor is the main rotor RPM (Nr) with reference to the airframe. Once the helicopter begins spinning rapidly to the right as during the onset of LTE, the governor will sense a false increase in Nr and reduce fuel flow to the engine in order to maintain what it believes to be a constant Nr with reference to the airframe. Any reduction in Nr will result in a corresponding reduction in tail rotor RPM, with an associated reduction in the effectiveness of the tail rotor.

Recommended LTE recovery techniques

Correct and timely response to the uncommanded right yaw associated with LTE by immediately applying full left pedal and decreasing power and main rotor blade pitch requirements, will usually counter the condition. However, if the pilot's response is incorrect or slow, the yaw rate may rapidly increase to a point where recovery is not possible. The pilot expressed no knowledge of recommended recovery techniques to counteract the onset of LTE.

In response to several reports of unanticipated right yaw incidents, the Federal Aviation Administration circular AC 90-95 recommends the following recovery techniques:

a. If a sudden unanticipated right yaw occurs, the pilot should perform the following:
(1) Apply full left pedal. Simultaneously, move cyclic forward to increase speed. If altitude permits, reduce power.
(2) As recovery is effected, adjust controls for normal forward flight.
b. Collective pitch reduction will aid in arresting the yaw rate but may cause an increase in the rate of descent. Any large, rapid increase in collective to prevent ground or obstacle contact may further increase the yaw rate and decrease rotor rpm.
c. The amount of collective reduction should be based on the height above obstructions or surface, gross weight of the aircraft, and the existing atmospheric conditions.
d. If the rotation cannot be stopped and ground contact is imminent, an autorotation may be the best course of action. The pilot should maintain full left pedal until rotation stops, then adjust to maintain heading.

Furthermore, Bell Operational Safety Notice (OSN) 206-83-10 states that "An unanticipated right yaw may occur under certain conditions not related to a mechanical malfunction. These conditions may include high power demand situations while hovering, and/or when relative wind affects airspeed versus ground speed." The OSN recommends recovery techniques as follows:

1. Apply full left pedal.

2. Apply forward cyclic.

3. If altitude permits, reduce power.

Organisational Factors

The company did not have systems in place to address the organisational aspects that were identified as factors contributing to the accident. These were:

1. The company had no formal pilot induction program. Newly inducted pilots were not required to perform flight checks in areas reflective of actual operating conditions.
2. The Chief Pilot did not document and maintain individual files on each line pilot. Line pilots were not required to perform flight checks in areas reflective of actual operating conditions.
3. Flight checks were not regularly scheduled and were of short duration.
4. The company had no Flight Safety Program in place.
5. The company had no formal system of maintenance control and no assigned maintenance controller. Non-compliance with maintenance requirements and unapproved maintenance was reported on company helicopters.

These were not required by regulation.

CASA surveillance

This operator was also involved in a fatal accident in March 1999. CASA Flying Operations Surveillance Guidelines-Variations to Normal Surveillance includes significant safety related incidents as typical triggers justifying long-term increases in scheduled surveillance. No special audit of the organisation was completed following the fatal accident. A Flight Operations Inspection completed on 29 January 1999 identified several discrepancies. The inspector's report included a note recommending increased surveillance of the organisation. CASA regional management also requested authorisation from the CASA central office for increased surveillance of the organisation, however, the surveillance level of the organisation remained the same.

An Airworthiness Inspection (ramp check) was completed on 12 April 2000. During that inspection, three discrepancies were noted against the helicopter. Included among these was one noting "flight manuals contain expired weight control documents". Prior to the accident, there was no documentation on the CASA files to indicate acquittal of the discrepancy.

Following this accident, a CASA team completed a special audit of the organisation during 11-17 August 2000. The special audit resulted in the CASA team issuing a safety alert to ensure all required maintenance was completed on company helicopters and six requests for corrective action to resolve safety concerns. The company corrected these discrepancies and continued charter operations following the audit.

CASA surveillance documentation

CASA utilised the ASR (Aircraft Survey Report) Aviation Safety Surveillance Program (ASSP) 604 form to outline discrepancies noted during airworthiness inspections of aircraft and helicopters. According to the CASA ASSP manual, inspectors and team leaders were responsible for the monitoring of acquittals of ASRs. The forms did not require the Certificate of Registration holder to carry out rectification action within any particular timeframe.

CASA utilised a form called the Safety Trend Indicator to analyse significant factors related to the operator's risk level. That form included a question concerning the non-acquittal of Non-compliance Notice (NCN) ASSP 603 forms within the last 12 months. No response was required concerning non-acquittal of ASR ASSP 604 forms.

When the pilot began the right banked turn, he exposed the helicopter to firstly, a left crosswind, then a quartering tail wind. Flying at low airspeeds and operating out of ground effect, the helicopter was satisfying several of the operational conditions necessary to experience an uncommanded right yaw or LTE as outlined in Bell OSN 206-83-10.

The pilot indicated no awareness of operational conditions necessary to experience LTE, or knowledge of recovery techniques to counteract the onset of LTE. The failure of the helicopter to recover from the LTE condition following the pilot's reported corrective actions, was probably a result of his lateness to recognise the onset of LTE in sufficient time to permit recovery.

Organisational Factors

CASA's audit of August 2000 found that the checking of line pilots by the Chief Pilot was irregular and ineffective. Pilot flight checks were conducted in areas unreflective of actual operating conditions. In addition, those flight checks were of insufficient duration to appropriately assess the pilot's skills. Safety awareness training of personnel was considered inadequate. The operator had not established a sufficient maintenance control program. This resulted in the operation of company helicopters with overdue maintenance requirements. The lack of a formal pilot induction program, adequate checking of line pilots for currency, adequate documentation of line pilot training, a company Flight Safety Program, and a formal system of maintenance control all contributed to a less than adequate safety culture within the company.

CASA surveillance

The March 1999 fatal accident may have justified an increase in surveillance as per CASA guidelines. CASA management however, did not revise surveillance of the operator following recommendations from area managers and Flying Operations Inspectors. As a result, the safety oversight of the operator by CASA may have been less than recommended in CASA guidelines. Following this latest occurrence, CASA subsequently increased its level of surveillance of the operator.

CASA surveillance documentation

Examination of the CASA aircraft file for this helicopter and other aircraft files, has identified a trend of non-compliance by operators to resolve discrepancies noted on the ASR ASSP 604 form. Non-acquittal of ASRs could also display a trend of non-compliance to airworthiness issues.

1. The pilot did not have adequate knowledge in recognition of operational conditions that could have induced LTE.

2. The pilot did not correctly identify operational conditions that could have induced LTE.

3. The pilot did not implement adequate recovery techniques to counteract the onset of LTE.

As a result of this investigation the Australian Transport Safety Bureau has identified a safety deficiency related to pilot training. The results of the investigation of this safety deficiency will be published on the Australian Transport Safety Bureau website.

As a result of this investigation on 9 March 2001, the Australian Transport Safety Bureau issued the following recommendations to the Civil Aviation Safety Authority.

R20010015

The Australian Transport Safety Bureau recommends the Civil Aviation Safety Authority consider revising Civil Aviation Safety Authority Safety Aircraft Survey Report 604 form to require a response date for acquittal of discrepancies.

CASA response to recommendation R20010015 dated 10 April 2001.

The ASR (Aircraft Survey Report) can be assigned either Code A, B or C.

Code A identifies a defect or damage to the aircraft, and requires that maintenance to rectify the defect or damage must be carried out before further flight. This acquittal requirement is very specific in relation to the aircraft operational requirements. However, if the Certificate of Registration (CoR) holder removes the aircraft from service, an actual acquittal date has no relevance. The requirement to perform the maintenance before further flight remains.

Code B is a direction under CAR 38(1) to have defects or damaged assessed and rectified as necessary. The Code B direction is used to bring a defect or damage to the attention of the CoR holder, the pilot or operator where:

- A defect or damage to the attention of the CoR holder, the pilot or operator where:

- The inspector considers the defect or damage to be minor, or; The inspection carried out on the aircraft does not enable proper determination if the defect or damage is major. In which case the C of R holder, the pilot or operator is responsible to have an assessment carried out to determine the true nature of the defect or damage, and have appropriate rectification carried out. While the assessment needs to be done prior to further flight, the rectification might not be accomplished for some time in the future, where, for instance, the defect is minor and falls within the provision of Permissible Unserviceabilities.

Code C is used to give the C of R holder formal notification of a non-compliance with a requirement or condition imposed under the regulations and is judged, on the basis of the inspection, not to have an immediate adverse effect on safety. However, the matter is required to be assessed and rectified at the earliest opportunity.

As can be seen from the above discussion, it is often the case that an acquittal date cannot practically be imposed at the time of issue of the ASR. However, CASA is currently reviewing the ASR process to see how that process might be more closely monitored.

ATSB actions concerning CASA response to R20010015

The ATSB classifies this recommendation OPEN- MONITOR, pending CASA review of the ASR process.

As a result of this investigation on 9 March 2001, the Australian Transport Safety Bureau issued the following recommendations to the Civil Aviation Safety Authority.

R20010016

The Australian Transport Safety Bureau recommends the Civil Aviation Safety Authority consider revising Civil Aviation Safety Authority Safety Trend Indicator form to indicate organisational non-acquittal of Aircraft Survey Report ASSP 604 forms within the last 12 months.

CASA Response to Recommendation R20010016 dated 10 April 2001.

Non-acquittal of an ASR within a particular time period does not necessary reflect poorly on an operator. Consequently, for ASR acquittal information to be meaningful, in regards to Safety Trending, would need complex and prescriptive criteria to be developed and followed by CASA inspectors in the field.

Depending on the outcome of the review mentioned in Para 2 above, CASA would also explore what useful application that information might have in regard to the Safety Trend Indicator.

ATSB actions concerning CASA response to R20010016

The ATSB classifies this recommendation OPEN- MONITOR, pending CASA review of the ASR process.

At the time of the accident, the Cessna 210 was for sale. The pilot had conducted a pre-purchase inspection, including an engine run, the day before the accident. On the day of the accident, the pilot and two passengers boarded the aircraft for an evaluation flight to a nearby aerodrome. Following an uneventful engine run-up, the aircraft was observed to take off from runway 31R and flew for approximately 2.5 km at low level. The pilot subsequently carried out a successful ditching into a water-filled quarry. The pilot and both passengers successfully exited the aircraft but one passenger, who was unable to swim, drowned before reaching land.

The aircraft was manufactured in 1965 and had accumulated 8,013 airframe hours. All required maintenance had been performed and the aircraft had a current maintenance release, which listed no outstanding unserviceabilities.

During most of the previous year, the aircraft was in short-term storage at Mt Gambier SA. Approximately four months before the accident, a rough running engine was noted in the aircraft logbooks. The problem was later diagnosed as a cracked number 4 cylinder. The cylinder was subsequently replaced and the aircraft's 100 hourly inspection was carried out on 26 November 1999. On 24 December 1999, the aircraft was refuelled at Mt Gambier and flown to Moorabbin, Vic. by a ferry pilot who reported that the engine and aircraft performed normally. Except for one short flight five weeks before the accident, the aircraft remained on the ground until the accident flight. The engine was started and ground run four days before the accident flight. During the ground run, the pilot, who was not the accident pilot, noticed that the fuel selector valve was stiff but did not record the problem on the maintenance release.

Examination of the aircraft after it had been recovered from the quarry found that the flaps were at approximately the 10 degree position and the landing gear was retracted. Visible damage to the exterior of the airframe was limited to distortion of the main landing gear doors. The line to the manifold air pressure gauge was broken at the engine firewall. The throttle was in the idle position, the propeller control was in the full fine position and the mixture control was in the fully rich position. However, as the recovery of the aircraft from the quarry probably distorted the engine mounts, the positions of engine controls were not considered reliable. The magneto switch was in the BOTH position and both fuel pump switches were OFF. All engine instruments displayed readings that were consistent with a non-operating engine.

Engine and propeller

After recovery, the Teledyne Continental IO520 engine was dismantled for examination and all appropriate fuel and ignition system components were removed and tested. The propeller was examined and its governor bench tested. No fault that could have produced a significant loss of power was found with either the engine or the propeller. No blockages or loose baffles were found in the exhaust system.

Fuel system

The fuel selector valve handle was found in the left tank position but the selector valve, which is connected to the handle by two linkages, was found in the position of partly open to the left tank. The movement of the valve was stiff and the linkages were worn, allowing the movement of the valve to lag behind the handle, thereby giving a false indication of the valve's true position. The inside of the valve was corroded and the detent in the left tank position could not be felt when the valve was tested.

Fuel system testing

The position of the fuel selector valve had been index marked on the valve before its removal from the aircraft. The valve was rotated to the indexed position four times during testing and the flow rate measured. The measured flow rates at the indexed position varied between a minimum of 90 pounds per hour (PPH) and a maximum of 280 PPH. The engine manufacturer's specifications for the fuel system stated that the required fuel flow at full power was between 136 and 146 PPH. The engine manufacturer advised that with the fuel flow restricted to 90 PPH, this engine would develop approximately 75% of maximum power. The owner's manual stated that normal cruise power setting should be between 65% and 75% of maximum power.

When all the fuel system components, except the fuel selector valve, were connected to a test rig, they were confirmed to be capable of delivering to the engine a fuel flow that was slightly in excess of the engine manufacturer's specifications.

Fuel

Approximately 60 litres of fuel was drained from each wing tank after the aircraft was recovered from the quarry. When tested, that fuel was the correct type for the aircraft. A small amount of free water was present in the fuel. Ethylene Diamine (EDA) was the contaminant involved in the aviation gasoline contamination problem that occurred in southern Australia over the December 1999/January 2000 period. There was no EDA detected in the fuel samples taken from the aircraft, nor were any of the deposits, that are typically produced by EDA, found in any fuel system components.

Pilot experience

The pilot had held a Commercial Pilot Licence since 1962 and an Air Transport Pilot Licence since 1982. He had flown more than 13,000 hours on a range of aircraft including multi-engined turboprop aircraft. Since 1997, he had flown approximately 1,200 hours on Maule floatplanes and in the three months to the accident, almost all his flying had been on this type. He last flew an aircraft from the Cessna 200 series approximately three months before the accident, however, he had not flown the accident aircraft since 1966. He was correctly licensed and endorsed for the flight.

Witnesses

Six people located around the aerodrome witnessed the aircraft take-off. Their evidence was consistent on the following points:

• the aircraft engine ran normally during start, taxi and run-up,
• the engine note during the latter stages of the takeoff and the initial climb was unusual for the aircraft type,
• the aircraft became airborne at a point between 2/3 and 3/4 along the runway,
• the landing gear began retracting as soon as the aircraft left the ground, and
• the aircraft's angle of climb after takeoff was lower than normal.

Of the five witnesses who heard the aircraft takeoff, four reported that the engine sounded as though it was running smoothly at less than full power. The fifth witness reported that the engine sounded uneven, as though it was "running on only four of its six cylinders".

Pilot's recollection

The pilot reported that on the day before the accident and the day of the accident, the aircraft's engine had started and run without difficulty. Both fuel tanks were dipped and found to be slightly less than one quarter full. For the accident flight, the fuel selector valve remained in the left tank position from the engine start until the aircraft ditched. The engine run-up, that did not include a full power check, had not shown any unserviceabilities with the engine. The takeoff was normal until the landing gear was selected up. The pilot recalled that at that point the aircraft experienced a gradual loss of performance and was unable gain any further altitude. He recalled that after takeoff the manifold air pressure gauge read 22 inches which is approximately 5 inches less than would be expected. The pilot reported that when he realised that the aircraft would not make it back to the aerodrome, he decided to land in the first clear area that he saw. When the water-filled quarry came into view, he decided that a ditching was the best option available to him.

Performance of accident aircraft

The evidence of the ground witnesses and the pilot was consistent on the following points.

• No sudden loss of performance occurred.
• The aircraft displayed lower performance than expected after takeoff; however, it was still able to climb to a height of between 50 ft and 100 ft.
• The aircraft was unable to maintain height during the later stages of the flight.

Data provided by the aircraft manufacturer indicated that a Cessna 210E aircraft with 10 degrees of flap extended, would become airborne after a takeoff run of 104 metres, under the same conditions as the accident aircraft experienced. Eyewitness statements indicated that the aircraft did not leave the ground until it was at least two thirds of the distance along the runway, a distance of 748 m. That represented a takeoff run 719% longer than expected.

The aircraft manufacturer advised that the operation of the hydraulic pump during the landing gear retraction cycle in a normally operating Cessna 210E aircraft consumed approximately 7 horsepower, which was 3.8 % of the engine output at the maximum power setting. That would result in a small reduction in climb performance during gear retraction. In addition, the drag of the landing gear doors, which open during the retraction cycle, would also reduce the aircraft's performance by a significant margin. If the engine was producing less than maximum power, the percentage loss of performance during the landing gear retraction cycle would be proportionally greater.

The distance required to stop the aircraft, if the takeoff had been rejected from the lift off point, would be approximately equal to the landing ground roll distance under the same conditions. From the lift off point, the aircraft had 750 m to run before the aerodrome perimeter fence. Half of this distance was sealed runway; the other half was level grass. The manufacturer's data showed that at maximum weight, 233 metres would have been required to stop on a grass runway.

Performance of pilot's most recent aircraft type

The Maule floatplane, the aircraft that the pilot had flown most often in the previous three months, at maximum weight had a take-off run of approximately 500 m from smooth water and longer from rough water. Compared to a fully serviceable Cessna 210E aircraft, the Maule floatplane normally required a longer take-off run and had a much lower rate of acceleration.

Related accidents

In 1984, a US registered Cessna 210 sustained total power loss in-flight and the pilot force landed the aircraft. A factor in the accident was the use of the auxiliary fuel pump in the high position (NTSB CHI84FA282). In 1976, an Australian registered Cessna 210 was damaged in a force landing after the engine lost all power as a result of incorrect use of fuel pump in the high position (BASI 197606853). The owner's manual stated that the electric fuel pump should not be switched to the high position during normal operation because richer mixture than normal will result.

In 1972, a Cessna 210 was damaged in a force landing after the engine lost all power. A factor contributing to that accident was the prolonged sideslipping of the aircraft with low level of fuel in the tanks. (BASI 197204960). The owner's manual advised that with fuel tanks one quarter full or less, prolonged uncoordinated flight can uncover the fuel tank outlets, causing fuel starvation and engine stoppage. It further advised that "prolonged" means more than one minute.

ATSB records contain reports of four accidents (BASI 197304110, 198101450, 198201391, 198802338) involving Cessna 210 aircraft in which vapour lock in the engine fuel system resulted in complete power loss.

History of the flight

A Shrike Commander departed Horn Island on a charter flight to Saibai and Boigu Islands in accordance with the visual flight rules (VFR). The flight to Saibai took 32 minutes, and a further 13 minutes to Boigu Island. The aircraft then departed Boigu to return to Horn Island with an expected flight time of 35 minutes.

The pilot reported that he had maintained 5,500 ft until commencing descent at 35 NM from Horn Island. He tracked to join final approach to runway 14 by 5 NM, reducing power at 1,500 ft. At 5 NM from the runway, the pilot extended the landing gear and approach flap and commenced a long final approach.

When the aircraft was approximately 3 NM from the runway both engines commenced to surge, with the aircraft initially yawing to the right. The pilot commenced engine failure procedures and retracted the flaps. He tried a number of times to determine which engine was losing power by retarding the throttle for each engine, before deciding that the right engine was failing. The pilot shut down that engine and feathered the propeller. A short time later, when the aircraft was approximately 200 ft above the water, the left engine also lost power. The pilot established the aircraft in a glide, advised the passengers to prepare for a ditching, and transmitted a MAYDAY report on the flight service frequency before the aircraft contacted the sea. The aircraft quickly filled with water and settled on the seabed. All five occupants were able to escape and make their way ashore.

Wreckage and impact information

The aircraft ditched approximately 400 m short of the threshold of runway 14, and settled in 2.5 m of water. It was subsequently recovered for examination. Although the aircraft had been damaged during the ditching, it remained essentially intact. The fuselage was distorted in front of and behind the cabin area as a result of impact forces. The underside of the fuselage had also been pushed upwards, and both windscreens were broken. The fuel tanks were intact, and the fuel tank vents were not obstructed.

Personnel information

The pilot in command had gained a commercial pilot licence in 1994, and worked as a flight instructor until April 1998. He had been based at Horn Island since April and was subsequently appointed as the company chief pilot on 11 September 1998. Two days prior to his appointment he had been endorsed on the Aero Commander. At the time of the occurrence, the pilot had accumulated a total flying experience of 2,045 hours, including 566 hours on multi-engine aircraft, and 79 hours on Shrike Commander aircraft.

Aircraft information

The aircraft had undergone scheduled maintenance in Cairns on 28 August 1998, and had since flown 100.8 hours. The next scheduled maintenance was due in 19.2 hours. The horizontal situation indicator was unserviceable and had been placarded as such, with the defect being recorded in the maintenance release; however, that did not preclude the conduct of VFR flight.

No defects that could have contributed to the accident were found in the airframe or flight control systems. An examination of the engines and their associated systems did not reveal any defects that could have led to the loss of power. The right engine fuel control unit was found to be serviceable but worn. Bench tests indicated that it provided a fuel flow 10% greater than normal (approximately 6 L/h).

The right propeller had been feathered before the ditching; however, the propeller blades had not moved to the fully feathered position. Examination of the propeller dome revealed that oil sludge had prevented the propeller piston from driving the blades to the fully feathered position.

It was determined that the aircraft had been operated within its normal weight-and-balance range throughout the accident flight

The fuel system of the Shrike Commander consisted of five interconnected tanks, with one fuel quantity indicator receiving an electrical signal from a float-type sensor mounted in the fuselage tank. The flight manual specified that a fuel quantity indicator was a mandatory instrument for operation of the aircraft.

A single fuel filler point was situated on the upper surface of the right wing, inboard of the engine, and connected to the right forward wing tank. It was not possible to assess the fuel quantity by "dipping" the fuel tank through the fuel filler point. After the aircraft had been recovered from the sea the fuel system was drained and found to contain approximately 0.75 L of aviation fuel and approximately 100 L of seawater. The fuel quantity indication system was examined. A wire that connected to the wiper arm in the fuel transmitter unit was found to be broken under its insulation, causing an intermittent open circuit, which resulted in a fluctuating fuel quantity indication. When the wire was repaired the fuel indication system operated normally. The wire to the wiper arm in the fuel quantity transmitter had been repaired on 7 August 1998 by resoldering the wire onto the wiper arm. The maintenance manual for the Shrike Commander provided instructions for removal and replacement of the transmitter unit; however, there were no instructions for disassembly and repair of any components within the unit. No other defect was found in the fuel quantity indication system.

A piece of adhesive paper was found covering the fuel quantity indicator. The pilot reported that he had covered the indicator before the flight because he noticed that its indications had been intermittent on a flight the previous day, and believed that the fluctuating indications might have alarmed the passengers.

Fuel planning and consumption

Company operations in the Torres Strait involved transporting passengers and freight on flights between the islands. Pilots would frequently undertake two or three flights each day, with up to five sectors per flight. The Shrike Commander was normally flown with less than full fuel tanks in order to permit greater payloads.

An examination of the aircraft fuel records since the fuel tanks were last filled on 13 October 1998 revealed that the average fuel consumption rate was 143 L/h, with an average sector time of 22 minutes. The company operations manual specified the procedure to be used for fuel planning. That procedure stipulated that the fuel consumption rate for the Aero Commander was to be calculated at a rate of 110 L/h, with an additional allowance of 20 L for each takeoff. The fuel log found in the aircraft revealed that, in practice, pilots had used a consumption rate of 120 L/h without any additional allowance for takeoff's.

A fuel log was maintained for each flight; however, during the investigation significant inconsistencies in the recording of fuel quantities were repeatedly found between consecutive fuel log records. The fuel log indicated that before the aircraft was partially refuelled prior to the accident flight, the fuel tanks appeared to have 170 L of fuel remaining. Investigation revealed that the actual quantity was substantially less.

Survival aspects

During the impact sequence, the passenger in the rear left seat was thrown over the centre seats into the front right seat, which was unoccupied at the time. The passenger in the centre right seat received a back injury. Both windscreens were shattered by the impact. The pilot pushed out the remaining pieces of perspex on the left windshield with his hands, cutting his finger in the process, and the passenger who had been thrown into the front right seat was able to kick out the remaining perspex pieces of the right windshield. The pilot and the three passengers in the front of the cabin exited the aircraft through the open windshields. The passenger in the rear right seat escaped through the emergency exit window. The cabin rapidly filled with water. All the occupants then swam ashore, assisting the injured passenger.

All the aircraft seating and seat-belt assemblies were found to be securely attached to the airframe. Surface corrosion was present on seat-belt end fittings, which was consistent with salt-water immersion, and all except one operated normally. The left rear passenger lap-belt end fittings were stiff to operate, and difficult to close properly. The end fittings could be easily placed together incorrectly, allowing improper locking of the assembly.

The aircraft was not equipped with life jackets, nor was that a requirement for the intended operation.

Organisational and management information

The company had expanded rapidly over a short period. At the time of the accident, it was operating 13 aircraft of various types. The company structure consisted of a managing director who was based in Melbourne, an operations manager who controlled sales and the allocation of tasks to aircraft, a chief pilot who managed the aircrew and assigned their duties, and a total of seven pilots. The chief pilot had worked for the company for six weeks, and was his first appointment as a chief pilot. During the course of the investigation, it became apparent that he had had minimal experience or guidance in the management of operational personnel. There was evidence that the new chief pilot had experienced difficulty in establishing practices that ensured compliance with safety requirements.

The pilot had been approved as a chief pilot in accordance with the procedures contained in the Civil Aviation Safety Authority (CASA) Air Operator Certification Manual. The guidelines in appendix 16 stated that it was preferable to have a chief pilot who could "manage the system" rather than one with the best manipulative skill. A candidate for the position of chief pilot was required to demonstrate to a CASA Flying Operations Inspector (FOI) an ability to operate within the regulatory framework. The checklist for the approval process contained a list of regulatory knowledge required of a chief pilot, however, no guidance was provided to an FOI in assessing the overall capability of an applicant to manage the objectives of the operator, within the boundaries imposed by aviation safety legislation.

No formal system of responsibility for maintenance control existed within the organisation. Unscheduled maintenance was recorded on a whiteboard in the operations room, but responsibility to ensure that the whiteboard was kept up to date was not a delegated duty of any of the company personnel.

Pilots verbally reported defects to the chief pilot, who would then approach the relevant maintenance organisation to arrange for rectification. The company used four different suppliers of third-party maintenance, depending on the aircraft. The remoteness of the location meant delays would frequently occur while spare parts were sourced.