FACTUAL INFORMATION

During the evening of the day prior to the accident the aircraft was refuelled with 350 litres of aviation gasoline (AVGAS) which apparently filled the main tanks, and half-filled the tip tanks. Fuel samples taken the next morning, during the preflight inspection, were free from contamination.

The pilot was appropriately licenced and qualified to conduct the flight, and the company had the necessary approvals to conduct low level survey operations.

The aircraft was equipped with a life raft and life jackets, all of which were approved types and correctly maintained in accordance with the Civil Aviation Orders.

The aircraft departed at about 0815 CST and proceeded to a designated test range area near Iron Knob to carry out equipment calibration. The crew comprised the pilot and a data technician. After about 45 minutes the aircraft returned to Whyalla and commenced a further low-level calibration flight over Spencer Gulf.  The first run was in a southerly direction for 83 km to abeam Wallaroo then north to Whyalla where it turned south and repeated the run back to Wallaroo.  These runs were carried out at heights between 150 and 500 ft for specified periods of time. Abeam Wallaroo the aircraft, which was maintaining 500 ft, was again turned north.  It had been on this run for about 3 minutes at 110 kts when the engine suddenly lost power.

The data technician stated that following the loss of engine power the pilot changed fuel tanks from left to right then switched the boost pump on, but the engine failed to respond. The pilot transmitted a mayday call on the very high frequency radio stating the aircraft's approximate position south of Whyalla. The pilot and the data technician were not wearing shoulder harnesses and during the descent the pilot advised the data technician to remove his seat belt. However, the data technician kept his seat belt fastened and braced himself for the impact. He was not sure if the pilot had removed his seat belt. The estimated time from the mayday call to the ditching at 1050 CST was about 20 seconds.

The pilot sustained facial injuries. He and the data technician were wearing life jackets and they evacuated the aircraft through the right window and climbed onto the wing. Several unsuccessful attempts were made to retrieve the life raft that was stowed behind the pilot's seat, but within minutes of the ditching the aircraft sank.  Both crew members then commenced swimming towards the shore.  On several occasions they saw helicopters flying within 600 m of them but despite waving to attract attention they remained unseen.

After many hours the data technician lost contact with the pilot, who had been having difficulties swimming and keeping his head above water.  Just after dusk the data technician was found by a fisherman and a short time later the body of the drowned pilot was found by a search vessel.

The aircraft was snagged by a fishing trawler's net but subsequent searching with the aim of retrieving the wreckage failed to find it and further search attempts were abandoned.

ANALYSIS

The pilot was not wearing a shoulder harness and may have removed his lap belt prior to the ditching. As he was not wearing a shoulder harness to provide upper body restraint it is likely that the pilot sustained the facial injuries during the ditching. These injuries may have subsequently affected his ability to swim and keep his head above water.

The duration of the flight was 2 hours 30 minutes, and the data technician believed that the aircraft had been operating from the left fuel tanks when the engine failed. The left tanks had a total fuel quantity of 175 litres (169 litres usable) at departure, which should give an endurance of 2 hours 36 minutes at the calculated consumption rate of 63 litres per hour.

The duration of the flight was about the same as the endurance calculated for the quantity of fuel in the left tank. If the left tank had been used exclusively during the flight the engine may have suffered fuel starvation. At a height of 500 ft there may have been insufficient time for the engine to regain power after changing tanks.

The reason(s) for the loss of engine power could not be determined.

The helicopter was being crewed by the pilot and the property owner.  They were assisting stockmen to herd cattle 

from one paddock to another.  The fence line contained a number of gates through which the cattle were being moved. Normally the cattle were taken through a gate well to the south of the accident site, but on this occasion the other gates were being used as well.  One of these gates was under a high-tension powerline (with steel towers) and the other was at the corner of the paddock at its junction with a fence running along a road.

Witnesses reported that the helicopter had been working at the head of the mob for a short time to recover some strays before making a left turn to move around to the rear of the mob.  The helicopter was moving towards the road when it struck the wire.  Witnesses reported that some cracks were heard, and the pilot seemed to have the aircraft under control again before it broke apart about 6 ft above the ground.  It caught fire and burned.  The stockmen were able to get the pilot away from the fire but were unable to save the other occupant.

The powerline struck was a single wire earth return line about 7 m high and running parallel to the road fence about 6 m inside the paddock.  Investigation at the scene determined that the powerline was struck by the front brace on the left skid.  This caused the tail to be raised into the rotor disc, whereupon it was severed by at least two blades, producing the cracks reported by the witnesses. The anticlockwise yawing tendency produced by the wire on the left skid was countered by the clockwise yawing tendency of the rotor torque, and the helicopter ran along the wire for about 23 m before freeing itself.  As it came free the wire progressed toward the leading edge of the skid, eventually breaking off the forward end of the skid.

Initial impact marks on the ground were produced by the forward end of the right skid which broke off. The subsequent marks were produced by the remainder of the right skid.  The marks indicated that the helicopter was probably yawing rapidly anticlockwise at the time.  The main rotor mast and fuel tanks then broke away from the main body of the helicopter. Evidence indicated that a fire erupted after the helicopter collided with the ground. There was no sign of fire prior to ground contact.

No evidence of any pre-existing defects was found.

Although the pilot was unable to remember the accident after the collision with the wire, he could recall noticing the wire just prior to colliding with it.  He was aware of the wire's presence, having worked in the area on a number of previous occasions.  On this pass through the area, he forgot about it.

In regard to aerial stock mustering operations, Civil Aviation Order 29.10 para 5.2 states, in part: 'During aerial stock mustering operations a pilot shall not carry more than one other person, and that person must be essential to the successful conduct of the operation'.  An examination of the injuries to people involved in mustering accidents in the ten years to the time of this accident was conducted.  Seven pilots and three passengers had received fatal injuries, while 13 pilots and two passengers had received serious injuries.  A further eight pilots and eight passengers had received minor injuries.  Of the 132 people involved in mustering accidents, 87 were pilots and 45 were passengers.  The most effective way to minimise the injury rate to passengers is considered to be an educational campaign intended to make graziers more aware of the dangers involved in aerial stock mustering operations.

Significant Factors

1. The pilot forgot about the presence of a power line.
2. The tail boom of the helicopter was severed after collision with the powerline.
3. The pilot was unable to maintain directional control of the helicopter.

Safety Action

The Bureau of Air Safety Investigation is preparing an article concerning the potential hazards of carrying passengers during aerial stock mustering operations. This will be featured in a forthcoming issue of the BASI magazine 'Asia Pacific Air Safety'. The Bureau also proposes to distribute the article to aviation and rural industry publishers for wider dissemination.

The pilot had planned to fly direct from his property, Ocean View Farm, which is 92 km south-east of Esperance, to Jandakot. He obtained the area and aerodrome forecasts for the flight through AVFAX and submitted a SARTIME flight plan.  The pilot's pre-flight planning, obtained from his copy of the flight plan, indicated that he would have 280 minutes of fuel available for the 182-minute flight.

The forecasts indicated that anticipated low cloud and fog would clear from 0900 onwards in the area south of Narrogin and from 1000 onwards north of Narrogin. Conditions at Jandakot were forecast to be suitable for visual flight after 1000.

The aircraft departed Ocean View Farm at 0850. At 1009 the pilot called Perth Flight Service requesting an updated weather forecast for Jandakot Airport. The amended forecast passed to him indicated that widespread low cloud was now expected to continue in the Jandakot area for some time with periods of reduced visibility in drizzle and low cloud.

Amended forecasts for the areas south and north of Narrogin were issued between 0915 and 0940 indicating that cloud, fog and drizzle would be worse than originally forecast. These amended forecasts were not requested by the pilot and, therefore, not passed to him.

Between 1030 and 1100, witnesses reported hearing an aircraft at low level in poor weather, south-east of Narrogin. Shortly after 1100 an aircraft was observed circling Narrogin townsite (38 km left of the direct track planned by the pilot) at approximately 100 - 150 ft AGL with landing gear and flaps extended. The aircraft passed in and out of the low cloud as it circled.  Weather conditions at Narrogin at the time were a low cloud base (estimated to be 100 ft and observed to be down to the tops of trees in places), fog patches, no rain and a light and variable wind.

At approximately 1115 the aircraft crashed, in a near vertical attitude, into a farm paddock between the Narrogin townsite and the Narrogin airstrip.

The mode of impact, aircraft vertical, left wing low and yawing to the left, indicated that the aircraft was not in controlled flight at the time and the localised damage to the fuselage forward of the pilots' seats combined with the slight damage to the fuselage aft of the pilots' seats, indicated that the loss of control had occurred at low altitude. The generator and battery switches were found in the off position following the accident. The aircraft's automatic direction finder (ADF) was also found switched to the off position.

The flight plan, found in the wreckage, indicated the pilot's in-flight navigation procedures began to deteriorate after he passed abeam Lake Grace at 1004. The last entries made on the plan were his planned estimate abeam Kulin of 1042 and a copy of the amended Jandakot forecast given to him by Perth Flight Service. He also annotated that he had 30 gallons of fuel in each wing tank at that time.

The pilot's planning for the trip was comprehensive. He obtained the weather forecasts, prepared a flight plan and submitted flight notification to the Civil Aviation Authority.

The forecasts indicated that the weather would clear from 0900 onwards and, as he planned to depart at 0850 there was no reason for the pilot not to proceed with the flight to Jandakot.

The weather from Esperance to abeam Katanning was essentially as forecast.

The pilot requested the latest Jandakot weather at 1009 or about 20 minutes prior to encountering the poor weather conditions north of Katanning. It is possible that this request was precipitated by indications of poor weather ahead.

It is probable that the pilot, confronted with poor weather ahead made a decision to divert to Narrogin, an airport he was familiar with, instead of continuing to Jandakot. It is likely that the pilot was not aware of the full extent of the poor weather between his current position and Jandakot as he did not request an update, although he would have been able to see the general deterioration.

Witness information and the fact that the ADF was found switched off, indicated that the pilot probably descended to low level to remain in visual contact with the ground as he attempted to find Narrogin Airport.

Aircraft damage indicates that the aircraft probably stalled with a subsequent loss of control during the final landing manoeuvre.

Indications of an impending stall are normally provided by the aircraft's stall warning system. Once the pilot selected the battery switch off, the stall warning system would have been rendered inoperative. As a result, the pilot probably inadvertently removed an important indication that loss of control was imminent.

The passenger was not wearing the sash part of the seat belt at the time of impact.

Significant Factors

The following factors are considered relevant to the development of the accident.

1. The pilot did not request all the weather information available to him before making a decision on whether or not to continue the flight.
2. The pilot continued the flight into weather that was not suitable for visual flight.
3. The pilot inadvertently disabled the stall warning system.
4. The aircraft stalled at a low altitude from which recovery was not considered possible.

The pilot was spraying a tomato crop at the time of the accident. A set of three powerlines ran along the edge of the field at approximately 20 degrees to the direction of flight. It was reported that the pilot had been turning left off his spray runs and, on this occasion, the right wing had collided with the three wires from below during the start of the turn. The tip of the right wing struck the wires first. The aircraft then appeared to have rolled right and struck the ground with the right wing, cartwheeling until it came to a stop. The engine bay was destroyed decreasing the occupiable space in the cockpit. The pilot was still conscious when he was pulled from the left side of the wreckage. He was wearing a helmet which had been retained during the crash sequence and had suffered facial injuries as well as broken limbs. His visor appeared to have been up at impact.

The sun angle was off to the pilot's left by about 45 degrees and about 30 degrees above the horizon. It was reported that the wires were shiny with reflected light, immediately after the accident, and they should have been visible from the direction of flight.

It is probable that the pilot misjudged his clearance from the powerlines during the turn.

Factual Information

The helicopter was used by the pilot to commute daily between his home at Cape Schanck and the Port Melbourne Helipad.  At 1555 EST he obtained aerodrome forecasts for Melbourne and Moorabbin airports together with an area forecast, covering the area for the trip home.  Those forecasts indicated that showers associated with patches of low cloud could be expected.

At 1710 the pilot reported to Melbourne radar advisory service (RAS) that he had departed Port Melbourne for Cape Schanck and was tracking coastal at 700 ft.  At 1715 he reported to Moorabbin Tower that he was at Brighton at 700 ft for Cape Schanck, tracking via the coast and was in receipt of the Moorabbin automatic terminal information service (ATIS).  The Moorabbin ATIS at that time indicated that the wind was a light northerly, the visibility was restricted to 3,000 m in rain and visual flight rules (VFR) operations were restricted.

At 1728 the pilot reported to Melbourne Flight Information Service that he was at Mornington, at 700 ft, for Cape Schanck.  No further communications were received from the helicopter.  Numerous witnesses close to the accident site either heard and/or saw the helicopter approaching.  It was observed flying low, beneath low cloud and in steady rain, in a southerly direction parallel to a main road.  It then commenced a left turn over some farmhouses and a short distance further on it flew into the ground.

Witnesses reported that the weather in the area of the accident site consisted of low cloud, visibility reduced in steady rain, very dark conditions below the cloud and a light wind. The post-accident report from the Bureau of Meteorology confirmed the witness reports. The reported conditions were not suitable for visual meteorological conditions operations.

Recorded radar data showed that the helicopter tracked via the coast from Port Melbourne to the Rosebud area at altitudes of between 300 and 700 ft.  Approaching Arthur's Seat, a 1046 ft spot height, no further radar returns were received from the helicopter's transponder, indicating that the transponder had been either turned to standby or off. Some primary radar returns were received but these were lost approaching Rosebud, probably indicating that the helicopter was then below radar coverage.  The distance from the last transponder return to the accident site was approximately 11 km.

The time of the accident was estimated to be 1737 which was between one and two minutes before calculated last light at Rosebud.  Actual last light occurred earlier because of the weather conditions.

All of the pilot's flight time was logged on helicopters and although he had no instrument flying qualifications, he held a night VFR rating.

A detailed examination of the wreckage and the accident site indicated that the helicopter flew into the ground while turning to the left with the engine developing significant power.  The examination did not reveal any pre-existing defects that could have contributed to the accident.

The only technical aspects meriting discussion were the pre-crash condition of the attitude indicator (AI) and the altimeter.

Upon disassembly of the AI, a small stop pin was found dislodged from its locating hole.  A specialist examination concluded that it was most likely that the pin was dislodged during the accident.  If the stop pin was dislodged prior to flight, then the AI could not have been caged or subsequently erected on startup.  Had this been the case, then it is reasonable to assume that the pilot would have noted this and been aware that the AI was unreliable.  The pilot was neither trained nor qualified to operate the helicopter by reference to the AI.

The altimeter had a general error of minus 120 ft across its operating range. At 1,000 ft the error was 110 ft meaning the aircraft would be 110 ft higher than the altitude indicated on the altimeter.

During the investigation, the pilot's night flying training record was checked.  Some of that training was completed at his property at Cape Schanck where there was limited ground lighting. On occasions, during circuit training, it was necessary to fly in a direction which was out of sight of all ground lighting.  On several occasions when this occurred, the pilot experienced difficulty controlling the helicopter and the instructor had to take control.

Findings

1. The pilot held a night-VFR rating, but he was not instrument rated (i.e. he was not qualified to fly in instrument meteorological conditions).
2. There were no pre-existing defects found with the helicopter that could have contributed to the accident.
3. The pilot obtained appropriate weather forecasts prior to the flight.
4. The en route weather conditions encountered by the pilot were in accord with the area forecast and were not suitable for night-VFR flight.
5. The helicopter was flown at en route altitudes of between 300 and 700 ft.
6. At impact the engine was producing considerable power, and the helicopter was travelling at a significant forward speed.

Significant Factors

The following factors were considered relevant to the development of the accident:

1. The helicopter was flown into non-VMC at night.
2. The pilot probably lost visual reference, became disoriented and flew the helicopter into the ground.

1. FACTUAL INFORMATION

1.1 Sequence of events

The aircraft had been flown from Brisbane to Luskintyre to carry out a series of joy flights over the weekend. At the completion of those flights, it was configured for a wing-walking demonstration in which, during flight, a person would stand strapped to a demountable frame installed above the fuel tank on the upper wing centre section.

The aircraft was refuelled during the morning prior to the accident. Two local flights were flown before the wing-walking frame was installed. The wing-walker, who was also a Tiger Moth pilot and was experienced with this routine, was strapped into the frame. After starting the engine, the pilot boarded the aircraft, taxied to the eastern end of the airfield, turned, and commenced a take-off to the west.

After lift-off, a climb was made at a low airspeed. At approximately 150 ft above the ground, the aircraft's engine lost power. The aircraft commenced a turn to the left, the turn continuing to develop until the aircraft's nose dropped. The aircraft then descended steeply into the ground, caught fire, and was destroyed. Both pilot and passenger were fatally injured.

The accident occurred within the confines of the airfield, and no other property was involved.

1.2 Crew information

The pilot held a commercial pilot licence. He had 1,200 hours flight time, of which 570 were on Tiger Moth aircraft. Both his pilot licence and medical certificate were valid.

The wing-walker also held a pilot licence and was endorsed on the Tiger Moth aircraft.

Both crew members were experienced with the wing-walking routine.

1.3 Site, aircraft and wreckage information

The weather was fine with a light breeze from the north-west. Weather was not considered to be a factor in the accident.

There were no known unserviceabilities with the aircraft prior to the flight. The aircraft was properly certificated, and the maintenance release was valid. The last periodic maintenance inspection was performed in December 1993 and was valid for 12 months or 100 hours, whichever was the sooner. The aircraft had flown approximately 30 hours since that inspection.

The airframe was extensively burned and had suffered impact and heat distortion. It was not possible to definitely establish pre-accident serviceability. However, the wreckage examination disclosed an apparent anomaly with the flight control system in that the right rudder control horn was fractured. Specialist metallurgical examination determined that the fracture had occurred after the horn was affected by the post-accident fire.

The engine was extensively damaged by impact and fire. There was no evidence of power interruption from water contamination or mechanical damage, and evidence of sufficient fuel supply was obtained.  However, during a strip inspection it was found that an unmodified fuel needle valve was fitted to the carburettor.

1.4 Engine examination

The carburettor contained a fuel needle valve of a design that the manufacturer had declared obsolete in 1957. The needle fitted to the carburettor was Part Number CH 28696 and should have been replaced by Part Number CH 46155 in accordance with Gipsy Major Modification G1136. The modified needle was introduced to obviate sticking of the needle. This was accomplished by increasing the side clearance between the needle and the housing to 12-15 thousandths of an inch (0.012-.015 in). The original had a maximum clearance of two thousandths of an inch (0.002 in). The British manufacturer of the carburettor had declared the modification to be "highly desirable and strongly recommended to be embodied not later than the next complete overhaul provided parts are available". Existing needles were able to be modified, and new needles were manufactured.  After consideration, the Australian regulatory authority at that time did not make compliance mandatory for Australian-registered aircraft.

The engine was last overhauled in Griffith, NSW during 1982. There was no record of the fuel needle valve modification being incorporated nor was a mandatory requirement in force in 1982 for the modification to be incorporated. Since this accident, other engines in service on Australian-registered Tiger Moth aircraft have been found fitted with the obsolete fuel needle valves.

The carburettor needle and the needle valve seat exhibited signs of particulate contamination which appeared to be compacted dust or dirt.

There were no defects found in the remaining component parts of the engine or its accessories.

1.5 Video recording

A visitor to the airfield filmed both the preparation for the flight and the flight itself on a hand-held video camera. The video recording (with sound) revealed that the engine was operating normally during the take-off and initial climb but then lost power. The engine continued to run with the spluttering, staccato beat typical of an engine of this type at idle power. The recording also showed that right aileron and left rudder were applied for much of the period after the engine lost power.

Information was provided to the investigation team suggesting that an independent examination of the video recording had found evidence that the pilot's arm could be seen waving out of the cockpit, and that he was probably trying to grab flailing rudder cables. It was also reported that the recording indicated that the rudder was jammed to the left by the tail skid.

However, the video recording showed that the aircraft was normal in all respects as it taxied and lined up and took off. Had the rudder jumped over the skid keepers and been jammed, the pilot would not have been able to effect a straight take-off. The wreckage examination did not show any marks on the skid or the rudder to indicate that the rudder was restricted, and the skid itself was free to rotate in its tube housing. Because the skid was free to rotate in its housing, even if the rudder had jumped over the keepers, the rudder would still have been able to travel side to side had the pilot applied pressure to the control bar. However, total movement in one direction would have been slightly reduced.

The flailing rudder cables were supposedly from the failed right rudder control horn. Metallurgical examination did not support this hypothesis, and the wreckage examination did not show any other areas of distress within the rudder control system.

The video recording was digitised to aid enhancement. The images in the early part of the accident sequence, purported to be of the pilot's arm, were found to be images of the cowl-mounted air cleaner scoop and the propeller. An image adjacent to the fuselage in the area of the left wing root, noticeable on frames immediately prior to impact, was found to be the left cockpit door which was open throughout the flight. Both images were affected by pixel flare. (Pixel flare is the merging of the dots that make up the screen picture and is very evident in an image that is fast-moving on a screen.)

Specialist examination determined that the recording of the accident was of such a quality that even with enhancement it was not possible to detect the control cables.

1.6 Wing-walking

Wing-walking was prohibited in Australia until 1989 when Civil Aviation Regulation 250 was amended to relax this total prohibition. Regulations were drafted to allow wing-walking stunts in special circumstances under vigorously controlled conditions. Flying Operations Instruction 27-2, Issue 1, dated 21 April 1989, was raised to specify those circumstances and conditions.

Flying Operations Instruction 27-2 approved wing-walking stunts only at the following venues:

1. an Authority-approved air display as detailed in Flying Operations Instruction 27-1;
2. a commercial film production; or
3. practice sessions for either of the above.

The wing-walking stunt on the day of the accident was for the benefit of a welfare group with whom the pilot and wing-walker were associated. The event was not an Authority-approved air display, nor was commercial filming undertaken. The Flying Operations Instruction did not contain guidance for approving the event as a practice session and there was no evidence that the pilot had been granted blanket approval to use this sort of event as a practice session.

The Flying Operations Instruction contains a requirement that the flying display be previewed and approved by the Authority. The preview is to be an assessment of the display sequence flown by the display pilot, with the aircraft fitted with the approved wing-walking structure containing a dummy of equivalent weight to the intended wing-walker. Although there has been verbal advice to the Bureau that an assessment was made, the Civil Aviation Authority files available to the investigation did not contain evidence that the Authority had formally assessed and approved the sequence flown by the pilot. There is no evidence that an assessment had been made of the performance and handling characteristics of VH-UNA when configured for wing walking. The Flying Operations Instruction required such an assessment to be made.

Neither the Civil Aviation Authority files nor those files held by the pilot contained any evidence that the pilot had applied to the Authority for permission to install the frame assembly and carry out wing-walking. Accordingly, there was no evidence that the pilot had been formally apprised by the Authority of its requirements. Although there was no formal record of the stunt being assessed and approved, the stunt had been incorporated into some airshow programs approved by the Authority.

1.7 Aircraft performance

The Tiger Moth is a low powered, high drag aircraft. During the investigation it was found that a wing-walker would increase the drag by 27%. This increased drag would reduce the aircraft's maximum cruise speed from 75 kts to 58 kts.

The wing-walking frame fitted to the accident aircraft was manufactured for and fitted to Tiger Moth VH-GVA in January 1990. This aircraft was subjected to flight tests (supervised by the Civil aviation Authority) to assess, in accordance with Flying Operations Instruction 27-2, its performance and handling characteristics. The investigation found no evidence that any performance calculations were made prior to the flight tests.

During the initial flight test, VH-GVA was fitted with a propeller having a 4 ft 6 in pitch. On a subsequent flight, with a 4 ft 2 in pitch propeller fitted, the rate of climb improved, and it was established that the particular aircraft/engine/propeller/pilot combination achieved a best initial climb speed of 53 kts. The maximum attainable straight and level speed was 63 kts. The normal climb and cruise speeds are 59 kts and 75 kts respectively. The accuracy of the test results could not be determined as there was no requirement to calibrate the instrument system on the aircraft prior to the tests.

The flight tests found that before being fitted with the frame, VH-GVA accelerated from 50 kts to 70 kts in 12 seconds. With the frame fitted and a dummy installed, the aircraft took 24 seconds to accelerate from 50 kts to its maximum straight and level speed of 63 kts. There was also a noticeable rudder buffet that was later found to be reduced if the wing-walker stood with feet apart.

The wing-walk frame was later sold to the pilot of VH-UNA, who fitted it to his aircraft in February 1992, in accordance with an engineering order approved by the design engineer involved with the original installation on VH-GVA.

Along with the engineering order, the pilot received a copy of Civil Aviation Authority letter V131/24/34, dated 28 March 1990, which required among other things that for all wing-walking flights the propeller fitted to the aircraft should be of 4 ft 2 in pitch. The propeller fitted to the aircraft at the time of the accident was Part Number

DH5220/H/26 and of 4 ft 11 in pitch. There was no record of a fine-pitch propeller having been fitted to VH-UNA since the wing-walking frame was initially fitted in 1992.

There is no regulatory requirement for the owner of an aircraft to inform the Authority of any approved modification being fitted to an aircraft. Also, for this particular modification, there was no requirement for the flight manual to be amended to detail the conditions surrounding the installation of the modification. Consequently, the Authority's file for the aircraft did not contain details of the fitting of the frame to the aircraft.

The first entry in relation to the wing-walking equipment occurred one year after installation when an airworthiness survey of the aircraft found irregularities in the procedures used during installation. Certification for manufacture of the frame had not been made, and weight and balance considerations had not been addressed. The Authority's file did not contain a copy of the Authority's own letter that required a fine-pitch propeller to be fitted, nor did the survey disclose that an incorrect propeller was installed.

The design engineer who completed the original work on VH-GVA and authorised the installation onto VH-UNA is based at Bankstown, and his file was held in the Bankstown, NSW office of the Authority. The aircraft was based at Archerfield, Qld and its file was accordingly held in the Archerfield office of the Authority. There is no system within the Authority requiring that modifications approved by a design engineer be reflected on the file for the aircraft concerned.  Accordingly, there was no opportunity for the Archerfield-based officer carrying out the survey on the aircraft to check the configuration requirements prior to conducting a survey.

The first flight of VH-UNA after it was modified was conducted with the accident pilot in the frame. The pilot on that flight stated that he had difficulty climbing out of ground effect and that he was only able to attain a climb speed of 45 kts. The accident pilot is reported to have later stated that he had developed a slow flying technique that gave a climb performance acceptable to him. This technique is evident from videos taken at previous airshow performances which show the attitude difference between the accident aircraft and another Tiger Moth during take-off.

1.8 Incorporation of modifications

The carburettor manufacturer recommended that the modified fuel needle be introduced at the next overhaul after 29 April 1957, and parts were made available to accomplish that requirement.  The manufacturer's recommendation was not made mandatory by the then Australian Department of Civil Aviation. From 1957 to 1988, aircraft owners and operators were required to incorporate only those modifications made mandatory by airworthiness directives promulgated by the Department and its successor organisations.

Changes to the Civil Aviation Regulations initiated in 1988 made the aircraft owner responsible for deciding what modifications should be carried out. The regulator still retained the capacity to issue airworthiness directives.

Civil Aviation Regulations current at the time of the accident required that aircraft maintenance be carried out in accordance with the applicable provisions of the aircraft's approved maintenance data; that is, in accordance with the manufacturer's instructions specifying how maintenance should be carried out.

The Authority's airworthiness officers interviewed during the investigation disagreed as to whether the effect of that requirement would mean that Modification G1136 would need to be incorporated at next overhaul. One view was that it is impractical to catch up with 50 years of modifications on old aircraft such as the Tiger Moth and that "ancient" modifications could be ignored. A contrary view was that although many older aircraft could be grounded by the requirement, all modifications required by the manufacturer should be incorporated, regardless of the age of the aircraft.

1.9 Pilot reaction time

The time between the first engine splutter and the aircraft commencing a left turn was 3.5 seconds. The time between that first splutter and ground impact was 5.8 seconds. If VH-UNA was climbing at 50 kts, the rate of loss of airspeed after an engine power interruption is estimated to be 5 kts per second. The aircraft has a stall speed of approximately 40 kts. Therefore, the pilot would have had just two seconds to apply corrective action before the aircraft stalled. There is evidence that the aircraft had on at least one occasion attained only 45 kts, which would allow even less time to react to an unexpected emergency situation.

The Royal Air Force Institute of Aviation Medicine, Farnborough, UK carried out two experiments on pilot response times to emergencies presented in flight simulators. The experiments were conducted in the wake of an airliner accident in which the pilot took 5 seconds to react to an unanticipated emergency situation.

The first experiment involved a measure of the time taken to apply brakes after presentation of locked controls at rotation of a fixed wing aircraft. The second involved the time taken for helicopter pilots to depress the collective lever after the presentation of a double engine failure.

The mean reaction time was 3.4 seconds in the first experiment and 3.08 seconds in the second. Although these response times appear long, the fact that they were measured in a simulator in which pilots were expecting emergencies, makes them, if anything, conservative estimates of the response times likely to occur in actual flight. Even in this simulation some pilots took 7 seconds to react to an emergency they would have been anticipating.

2. ANALYSIS

2.1 Introduction

Shortly after the aircraft became airborne the engine lost power, possibly because the carburettor fuel needle became jammed in the housing sometime during taxi prior to take-off. If this had occurred, when the pilot applied take-off power the jammed needle would have limited the amount of fuel able to flow into the fuel chamber to replace fuel being used for take-off power (that is, the needle would have remained in its pre-take-off, idle power position). With the fuel being used at a rate greater than it was being replaced, it would only be a matter of time before the engine lost power. Possibly contributing to the event was a fuel needle valve of obsolete design coupled with the presence of some particulate contaminant.

Although the manufacturer had recommended the fitment of a different fuel needle valve, it was not mandated at the time by the Australian regulatory authority. At the time of the accident there was some confusion as to whether legislation required the installation of the modified valve.

2.2 Aircraft handling

It has been established that the pilot had developed a procedure to fly the aircraft at a very slow speed to obtain a rate of climb that was acceptable to him. The investigation was not able to establish precisely what speed was used, nor what rate of climb was attained. With the very high drag occasioned by the wing-walker, the high-nose attitude and the low forward speed, any loss of power such as occurred on this flight would have led to a very rapid loss of airspeed to a point where control would have been lost unless almost instant corrective action were taken. The most effective corrective action would have been to immediately lower the nose to maintain airspeed. It is not known why this was not accomplished.

The video recording showed that a substantial left rudder deflection and an application of right aileron occurred immediately after power was lost. The left rudder deflection occurred almost simultaneously with the wing-walker adopting the crouched position.

On a previous flight in VH-GVA, it was found that the position of the wing-walker could effect the airflow over the tail of the aircraft, which resulted in rudder buffet if the wing-walker did not stand with feet apart. The investigation was unable to determine whether the position adopted by the wing-walker after the loss of power resulted in the left rudder deflection. The effect of the wing-walker adopting a crouching position is not known but it could be that some airflow disturbance was generated that may have caused the left rudder deflection.

Another possibility is that left rudder was applied by the pilot in an attempt to execute a flat turn back towards the airfield. Yawing the aircraft in this manner would have rolled it to the left, a secondary effect which the pilot may have attempted to counteract by applying right aileron.

The Tiger Moth is fitted with differential aileron control which reduces the yaw effect of aileron application. Flying at slow speed, and thus at a high angle of attack, the down going left aileron would, even with differential aileron control, still increase the effective angle of attack of that wing beyond the stall angle, resulting in the rapid roll to the left, further yaw and nose-down attitude as seen on the video recording. The control positions seen on the video were those which, given low airspeed, could be expected to result in the aircraft entering a spin to the left.

2.3 Aircraft performance

The propeller fitted to VH-UNA had a pitch of 4 ft 11 in, a standard cruise propeller for that aircraft. The initial test on VH-GVA showed the aircraft to be performance-limited when fitted with a 4 ft 6 in pitch propeller. It was necessary to fit a fine-pitch propeller of 4 ft 2 in pitch to obtain a climb performance acceptable to that pilot. With a coarse pitch propeller fitted, VH-UNA would have been even more severely performance-limited than VH-GVA.

The pilot of VH-UNA possessed a copy of a Civil Aviation Authority letter that detailed the requirement to fit a fine-pitch propeller. It is not known why he did not comply with the requirement. However, had he fitted a fine-pitch propeller prior to departure from Brisbane, his cross-country cruise capability would have been degraded.

The Authority's procedures for recording that the wing-walking frame had been installed onto VH-UNA were deficient. Although the details were held on file in the Authority's Bankstown office in relation to the design engineer who approved the installation, they were not required to be copied to the aircraft file for VH-UNA which was held at Archerfield. The Queensland-based officer carrying out the survey on the aircraft would not have been aware from the data held on the aircraft file that the modification had been carried out some 12 months prior to the survey. Nor would he have been aware of the conditions surrounding the installation and operation of the wing walking frame.  Accordingly, the chance to detect the incorrect propeller installation was missed.

2.4 Organisational factors

The aviation system has a number of built-in defences which are designed to detect any hazards before they lead to an accident. In this case, when the regulations were altered to allow activities such as wing-walking, instructions were issued by the Authority to regulate the conduct of the activity. These instructions were, in effect, aircraft and event specific in that they required approval on an individual basis.

The pilot of VH-UNA had acquired the wing-walk frame which he subsequently fitted to his aircraft under the approval of an authorised person.  There was no evidence that the Authority was aware of the fitment of the frame other than when the pilot was approved to take part in certain air displays.  Accordingly, the Authority did not carry out, as required by the Flying Operations Instruction, an airworthiness inspection, nor an assessment of the aircraft's performance.

Similarly, there was a requirement that the wing-walking stunt be previewed and approved by the Authority. Although the investigation received anecdotal evidence that this was done, no formal evidence of the preview having taken place was found. If the preview did take place, it was apparently of a cursory nature in that it did not detect that there had not been an airworthiness inspection, nor an assessment of VH-UNA's performance.

Moreover, surveillance conducted by the Authority on the aircraft did not detect that the fitment of the wing-walking frame had not been completed as required and that the aircraft was fitted with an incorrect propeller of a coarser pitch.

When the pilot purchased the frame, he obtained a copy of the engineering order relating to the fitment of the frame and an Authority letter that required the fitment of a fine-pitch propeller to the aircraft for wing-walk activities. He apparently chose not to fit the propeller. In so doing, he circumvented the protection afforded by the fitment of a fine-pitch propeller which would have improved the climb performance.

Following the poor climb performance obtained on the initial flight with the frame fitted, the pilot apparently developed a flying technique which involved operating at a slower climb speed. By using a lower climb speed, the pilot had almost entirely removed any margin of performance to allow adequate reaction time in an emergency.

3. CONCLUSIONS

3.1 Findings

1. The pilot held a current commercial pilot licence, and his medical certificate was valid.
2. Both crew members had previous experience with wing-walking activities.
3. The performance of the aircraft was significantly degraded when carrying a wing-walker.
4. The extent of the performance degradation was not calculated during the initial approval process.
5. The calculations made as a part of this investigation showed that the Tiger Moth was probably not an appropriate aircraft for carrying out wing-walking stunts.
6. The processes involved in approving the stunt, and in approving the pilot to carry out the stunt, were ineffectively controlled and poorly documented by the Civil Aviation Authority.
7. The pilot did not carry out this particular flight under the conditions specified by the Civil Aviation Authority.
8. The aircraft was not fitted with the required fine-pitch propeller.
9. The incorrect propeller installation was not detected during an airworthiness survey of the aircraft.
10. The fuel needle installed in the carburettor was of an obsolete configuration and a modification, to increase the fuel needle to housing clearance to preclude jamming, had not been carried out.
11. The fuel needle and housing showed evidence of particulate contamination which would have increased the probability of the needle jamming.
12. The manufacturer introduced the modification in 1957 for incorporation at the next overhaul. The Australian regulatory authority did not list the modification for mandatory incorporation.
13. The engine lost power suddenly, possibly because of a jammed fuel needle valve.
14. The loss of power occurred shortly after take-off while the aircraft was climbing at slow speed in a nose-high, high-drag configuration.
15. The aircraft's speed rapidly decayed to a point where control was lost.
16. The video recording showed that, following loss of power, the nose of the aircraft was not effectively lowered, and the controls were in a pro-spin configuration (i.e. left rudder and right aileron applied).
17. When control was lost there was insufficient height to effect a recovery before the aircraft impacted the ground.

3.2 Significant factors

The following factors were considered relevant to the development of the accident.

1. The performance of the Tiger Moth was such that the aircraft was probably inappropriate for carrying outwing-walking stunts.
2. The flight was not carried out in accordance with the conditions for wing-walking prescribed by the Civil Aviation Authority.
3. The aircraft suffered a power loss while in the climb.
4. Immediate, appropriate control inputs were not applied, and control was consequently lost at a height insufficient to effect a recovery.

4. SAFETY ACTION

4.1 Recommendations

As a result of this investigation the Bureau, on 14 June 1994, issued Interim Recommendation IR940146, which stated:

The Bureau of Air Safety Investigation recommends that the Civil Aviation Authority review all approvals granted for high drag installations fitted to aircraft to ensure that the particular aircraft has been proven to have a satisfactory performance. This should meet, as a minimum, the manufacturer's climb speed, and take regard of common emergency conditions that could arise.

The Civil Aviation Safety Authority response, dated 30 August 1995, stated:

The Authority does not maintain a central register of approvals issued for high drag installations. However, the number of such approvals is small, and most are issued for reasons unrelated to high drag or low performance. I am therefore confident that the problem highlighted by this accident is confined to "wing walking" situations.

The Authority formally accepts your recommendation and will review any further applications for "wing walking" flights to take account of the performance parameters outlined in the recommendation.

4.2 Safety advisory notices

As a result of the investigation into this occurrence, The Bureau of Air Safety Investigation issues the following Safety Advisory Notice.

SAN960062

The Bureau of Air Safety Investigation suggests that the Civil Aviation Safety Authority advise all owners of Gipsy Major-powered aircraft to expedite the incorporation of Gipsy Major modification G1136.

The hang glider pilot was soaring off the cliffs east of the Cape Byron lighthouse where the nearest area suitable for a landing is Tallows Beach, several hundred metres to the south. The wind had been ESE at about 15 knots prior to a sudden arrival of a front passing through which changed the wind to a 20 to 25 knot southerly. Other hang glider pilots had landed prior to the arrival of the front which was not accompanied by any telltale cloud change. The hang glider pilot was soaring at about 500ft when the change came through and was unable to glide into wind to a beach landing. He landed in the surf and was apparently unable to extricate himself from his harness and drowned.

The above details were provided by the Hang Gliding Federation of Australia.

Summary

On Sunday 24 April 1994, at about 0910 EST, Douglas DC-3 aircraft VH-EDC took off from runway 16 at Sydney (Kingsford-Smith) Airport. The crew reported an engine malfunction during the initial climb and subsequently ditched the aircraft into Botany Bay. The DC-3 was on a charter flight to convey a group of college students and their band equipment from Sydney to Norfolk Island and return as part of Anzac Day celebrations on the island. All 25 occupants, including the four crew, successfully evacuated the aircraft before it sank.

The investigation found that the circumstances of the accident were consistent with the left engine having suffered a substantial power loss when an inlet valve stuck in the open position. The inability of the handling pilot (co-pilot) to obtain optimum asymmetric performance from the aircraft was the culminating factor in a combination of local and organisational factors that led to this accident. Contributing factors included the overweight condition of the aircraft, an engine overhaul or maintenance error, non-adherence to operating procedures and lack of skill of the handling pilot.

Organisational factors relating to the company included:

• inadequate communications between South Pacific Airmotive Pty Ltd who owned and operated the DC-3 and were based at Camden, NSW and the AOC holder, Groupair, who were based at Moorabbin, Vic.;
• inadequate maintenance management;
• poor operational procedures; and
• inadequate training.

Organisational factors relating to the regulator included:

• inadequate communications between Civil Aviation Authority offices, and between the Civil Aviation Authority and Groupair/South Pacific Airmotive;
• poor operational and airworthiness control procedures;
• inadequate control and monitoring of South Pacific Airmotive;
• inadequate regulation; and
• poor training of staff.

During the investigation, a number of interim safety recommendations were issued by the Bureau. These recommendations, and the CAA's responses to them, are included in this report.

FACTUAL INFORMATION

Circumstances

The pilot of the Piper Aztec submitted flight plan details by telephone to Cairns Tower for a visual flight rules (VFR) charter flight from Cairns to Palm Island via Innisfail. The plan indicated an initial track of 153 degrees M at an altitude of 5,000 ft.

The aircraft departed Cairns at 0946 hours EST and the pilot advised Cairns Approach that he was tracking on the

153 omni radial from Cairns. At 0954.35 he reported maintaining 5,000 ft. At 0956.02 a regular public transport (RPT) aircraft inbound to Cairns from the south reported approaching 7,000 ft and was subsequently cleared to descend to 6,000 ft. At 0956.59, after the potential confliction with the Aztec was resolved, the RPT aircraft was cleared to descend to 4,100 ft. At this time the Aztec was 23 NM from Cairns at 4,600 ft and about 2 NM right of track. A short time later the approach controller noticed that the radar returns from the Aztec had ceased.

Terrain in the area is known to cause shielding and the loss of radar returns. The controller assumed that shielding had caused the Aztec to disappear from radar so he instructed the pilot of the Aztec to call the area flight service frequency, as there was no further requirement to remain on the approach frequency. No reply to this transmission was received and this was also thought to be due to terrain shielding. A short time later other aircraft in the area reported the operation of an emergency beacon. A distress phase was initiated, and the wreckage of the Aztec was subsequently located on the western side of a blind valley north-west of Bellenden Ker Centre Peak at about 4,200 ft above mean sea level (AMSL) by a search helicopter.

Examination of the recorded radar data indicated that the aircraft gradually drifted right of track during the climb to 5,000 ft. At top of climb, some 15 NM south of Cairns Airport, it was about 0.75 NM right of track. At around this point, the track deviated further right by about 12 degrees. This track remained relatively constant until the aircraft was about 24 NM from Cairns where it again turned right. The aircraft maintained 5,000 ft to about 19 NM from Cairns after which it descended to 4,800 ft and remained between 4,800 and 4,700 ft until about 23 NM from Cairns. From this position it commenced further descent which continued for about 1 minute until the radar return ceased at a recorded altitude of 4,200 ft. During the descent the computed groundspeed of the aircraft decreased from 137 kt to 105 kt.

Examination at the accident site indicated that the aircraft struck the rainforest canopy at 4,200 ft AMSL with a descent angle of about 8 degrees and banked about 22 degrees to the right. The aircraft track at impact was about 196 degrees M.

Wreckage Examination

Examination of the aircraft wreckage did not reveal any abnormality which might have contributed to the accident.

Other than a complete set of Instrument Approach and Landing Charts, no other maps or charts were found in the wreckage. 

The Pilot

The pilot held a commercial pilot licence and was endorsed to fly PA-23 aircraft. Although his instrument rating had expired, he had conducted some instrument flying practice during the day prior to the accident.

The pilot had only limited flying experience in the Cairns area. This experience consisted of a short check flight at Cairns on 27 February 1994, a flight from Palm Island to Cairns on 17 March 1994, and two check flights at Cairns on 17 and 18 March 1994. The accident flight was the first recorded occasion of the pilot flying from Cairns to another destination.

The aircraft operator indicated that the pilot had not been given any specific briefing on the Cairns area as he considered that a pilot with 4,500 flying hours experience would not require such a briefing.

The post-mortem examination revealed some coronary artery occlusion which was considered to be too minor to have adversely affected the performance of the pilot.

Weather

The weather forecast for the area indicated a fresh to strong south-easterly airflow over the area with isolated showers over the coast and ranges. Broken stratus cloud was forecast from 1,000 to 3,000 ft in precipitation, along with scattered cumulus from 2,000 to 10,000 ft. Rain showers with 4 km visibility and occasional moderate turbulence below 7,000 ft near the ranges were also forecast.

The weather recorded on the Cairns Automatic Terminal Information Service (ATIS) at 0849 was wind 160 degrees M at 10-15 kts, temperature 25 degrees C, two oktas of cloud at 2,500 ft with lower patches and three oktas at 3,500 ft. There were showers in the area. Cairns Tower controllers stated that the top 500 ft of Mt Bellenden Ker appeared to be covered by cloud around the time of the accident.

Operating requirements

Aeronautical Information Publication (AIP) Australia RAC - 50a para 43.5.1 addresses flight under the VFR. The requirements include, inter alia:

1. the pilot in command of a VFR flight in controlled airspace must navigate by visual reference to the ground or water; and
2. when operating at or below 2000 ft above the ground or water, the pilot in command must be able to navigate by continuous visual reference to the ground or water or by the use of approved radio navigation apparatus as specified in CAO 20.8.

Under the VFR, AIP RAC - 33 requires that for the track being flown by the accident aircraft, the appropriate altitude would have been odd thousands of feet plus 500 ft for example 5,500 ft or 7,500 ft.

RAC CTL - 1 para 14.1 states, inter alia that a pilot must not deviate from track or change level without obtaining ATC approval when in controlled airspace.

The Approach Controller's duties included a requirement to maintain general radar surveillance of his area of responsibility insofar as the performance of other functions permitted. As part of this monitoring function, the controller was required to advise the pilot of a radar identified aircraft when that aircraft was observed to deviate beyond the normal navigational tolerance from the intended track. This tolerance is defined in the Manual of Air Traffic Services (MATS) as plus or minus 2 NM when an aircraft is 2,001 to 5,000 ft AGL and is navigating by visual tracking and position fixing.

MATS indicates that assigned cruising levels shall whenever practicable be in accordance with the level selected by the pilot and assigned levels shall normally conform to the appropriate table of cruising levels. Levels not conforming to these tables may be assigned when air traffic or other circumstances require. Prior to assigning an aircraft a non-standard level the controller shall consider workload and coordination implications along with the effect on aircraft already operating at standard levels.

Air Traffic Control

After the pilot had reported maintaining 5,000 ft he did not request a clearance to descend or alter heading.

A significant proportion of air traffic in the Cairns area operates in the VFR category. These flights often operate in an environment involving inclement weather and high terrain. The Cairns air traffic controllers reported that, particularly during the wet season (December-March), local weather conditions are frequently such that aircraft operating VFR are required to deviate from track to remain clear of cloud or avoid high terrain.  In this environment the controllers become accustomed to aircraft operating adjacent to high terrain or deviating off track and it is not unusual for radar and radio contact with VFR aircraft to be lost because of terrain shielding.

The final 30 seconds of VH-BOC's descent were observed by a supervising controller who was randomly monitoring a radar screen in the control tower. On seeing the radar return from VH-BOC disappear he immediately returned to the Approach Control Centre to check the status of the aircraft, which by this time was no longer in radio contact.

Flight Planning

The pilot was not asked by the briefing officer or the air traffic controller why he chose to fly at 5,000 ft. No explanation was found as to why the pilot chose to fly the route at 5000 ft. There was no requirement for air traffic control to query the cruise altitude nominated by the pilot even though the controllers were aware that 5000 ft was not normally used by VFR traffic in the area. Aircraft operating in the VFR category in the Cairns area normally cruise below 2,000 ft or above 6,500 ft due to the prevalence of cloud on the ranges.

ANALYSIS

The recorded radar data showed a distinct change in aircraft track at about 16 NM from Cairns shortly after top of climb.  The forecast winds were fairly constant from 2,000 ft to 7,000 ft so the track change seems unlikely to have been due to wind. It is possible that the pilot deliberately altered heading towards the blind valley west of Bellenden Ker Centre Peak in an attempt to avoid the deteriorating weather conditions along the intended track.

The descent pattern flown by the aircraft could also indicate that the pilot was manoeuvring the aircraft to remain clear of cloud. Having limited familiarity with the area and apparently no topographical maps on board the aircraft the pilot was not well placed to safely navigate the aircraft. The final descent and right turn made by the aircraft were possibly an attempt to remain clear of cloud.

Once VH-BOC had passed the inbound regular public transport traffic, when traffic separation considerations were no longer a factor, ongoing surveillance of the aircraft reverted to becoming part of the controller's normal monitoring function. A number of considerations influenced the controller's subsequent monitoring of the aircraft. There was other traffic, including IFR traffic, under the controller's jurisdiction which required his attention. The aircraft remained within 2 NM of the Cairns-Innisfail track until about one minute 30 seconds before radar contact was lost. The aircraft was not significantly beyond 2 NM right of track until 30 seconds or so before radar contact was lost. Because of the terrain and weather conditions generally prevailing in the Cairns area, controllers can in effect, become desensitised to track and altitude deviations by aircraft operating in the VFR category.

Had the pilot reported to ATC that he was deviating to the right of track and/or descending or that he was experiencing difficulties with weather conditions, he would have alerted the controllers and been provided with navigation assistance.

CONCLUSION

Significant factors

The following factors were considered relevant to the development of the accident.

1. The pilot was not familiar with the area.
2. The pilot apparently did not have with him in the aircraft any relevant topographical maps or charts covering the route being flown.
3. The pilot did not advise air traffic control that he was deviating from track and/or descending nor that he was encountering weather difficulties.

1. FACTUAL INFORMATION

Sequence of events

On the day before the accident, the aircraft flew from Aurukun to Weipa with the chief pilot occupying the left pilot seat and the pilot involved in the accident occupying the right pilot seat. At Weipa the chief pilot left the aircraft, instructing the other pilot to fly some practice circuits before returning the aircraft to Aurukun. Before commencing the circuits and the return flight to Aurukun, the aircraft's two main tanks each contained 100 L of fuel and the two wing tip tanks each contained about 90 L of fuel.

On the day of the accident the pilot added 200 L of fuel at Aurukun to the aircraft's tanks and then flew the aircraft and the passengers to Weipa. About 50 minutes before sunset, the aircraft taxied for departure from runway 30 for the 25-minute return flight to Aurukun.

When the aircraft was about 300 ft above ground level after take-off, a witness reported that all engine sounds stopped and that the aircraft attitude changed from a nose-high climb to a more level attitude. A short time later, the noise of engine power surging was heard. The aircraft rolled left and entered a spiral descent. It struck level ground some 350 m beyond the departure end of runway 30 and 175 m to the left of the extended centreline.

Wreckage examination

The aircraft had impacted the ground in a 30-degree nose-down attitude with 45 degrees of left bank. The left wing was broken at mid-span. The cockpit and forward cabin were totally crushed back to the leading edges of the wings.

The right propeller had gouged a deep hole in the soil and the propeller blades were bent both against the direction of rotation and rearwards toward the engine, indicating that this engine was producing considerable power at impact. The right fuel distributor valve contained fuel.

The left propeller was in fine pitch. One blade was bent rearwards toward the engine and the other blade was undamaged. Part of the spinner was crushed and part of it was almost intact. This damage pattern indicates that the left engine had stopped before impact. The left fuel distributor valve contained little fuel.

The left engine was removed from the aircraft and dismantled. No pre-impact damage that would have prevented the engine from operating was found.

Inspection of the airframe and other systems did not reveal any faults which might have contributed to the accident.

Fuel system

The aircraft had been fitted with the manufacturer's wing tip tank modification. Each tip tank had a useable capacity of 104.5 L and each main tank a useable capacity of 240 L. A flight manual supplement detailing the operation of this fuel system had been issued and incorporated in the flight manual. The fuel management section of this supplement indicates that, for structural reasons, fuel from the tip tanks must be used last, and that 50 L should be retained in each tip tank unless the fuel is needed for holding or diversion to another airfield. There is a warning in the flight manual supplement that take-offs and landings on main tanks are prohibited when the gauges read less than three gallons (about 14 L). There is no corresponding warning for the tip tanks.

Examination of the tip tanks showed that the fuel feed line was located centrally at the inboard tank baffle/outer wing rib near the bottom of the tank. The two main fuel selectors in the cockpit had moved from main fuel cock selection when the cockpit area was crushed during the main impact. However, examination of the fuel system confirmed that the main fuel cocks were open.

Toggle switches which control the main/tip tank selection were destroyed during impact. However, the light globes from the fuel tank indicators were examined and these indicated that the tip tanks were selected at the time of impact. Further inspection of the fuel supply system confirmed that the electrically actuated tip tanks fuel cocks were selected to draw fuel from the tip tanks.

The left tip tank was ruptured and separated from the wing. It contained about 5 L of fuel. The right tip tank was partially separated and did not contain any fuel. Reports from people at the scene immediately after the accident indicated that a large amount of fuel from the ruptured main tanks was present at the site.

The pilot

Six weeks before the accident, the pilot completed his endorsement training on an Islander aircraft which was not fitted with the tip tank modification. However, the endorsing instructor had briefed the pilot on the various fuel systems encountered in the Islander family of aircraft, including the particular wing tip tank modification fitted to VH-JUU. After his endorsement the pilot flew VH-JUU for a total of 3.6 hours until the day before the accident. The duration of the flight on the day before the accident, together with that of the passenger flight to Weipa on the day of the accident, was approximately one hour and twenty minutes. Therefore, at the time of the accident, the pilot had a total of 6.7 hours on the aircraft type.

Passengers and freight

The purpose of the flight was to collect cartons of beer from Weipa. The Aurukun Community had a policy of allowing a maximum of ten cartons to be carried on any one charter flight. However, sometimes passengers would insist on carrying more. The aircraft wreckage contained 30 cartons of beer and two bottles of rum, the latter being totally prohibited by the community. The cartons had been packed on and around seat rows four and five. The load had not been tied down. The aircraft gross weight was calculated to have been 47 kg below the limit for this take-off. The centre of gravity was within limits.

Checklist

The endorsing instructor had given the pilot an Islander checklist. The aircraft usually carried a normal procedures checklist on a clipboard, but this was inadvertently left at Aurukun. A checklist for normal procedures was not found in the wreckage although an emergency procedures checklist was found incorporated in the flight manual carried on board.

Fuel management

For planning purposes on this flight, the flight manual indicated a fuel consumption rate of 135 L per hour. The chief pilot reported that when he handed the aircraft over to the pilot at Weipa on the day before the accident there was about 90 L in each tip tank and that the tip tanks were probably selected to provide fuel to each engine.

2. ANALYSIS

If the tip tanks were selected since the previous day, the tip tank fuel contents should have been exhausted at about the time of the final take-off from Weipa. With a low quantity of fuel in each tip tank, the fuel lines from each tank probably became unported as the aircraft climbed after take-off, resulting in engines losing power from fuel starvation. When the pilot changed the attitude of the aircraft after the loss of power, some fuel probably became available to the right engine which then regained power.

Other factors include the pilot's low level of experience in the aircraft type, the absence of a normal procedures checklist and pressure from the passengers to complete the return flight with the excess alcohol. This pressure may also have accounted for the freight not being correctly secured.

A double, simultaneous engine failure was probably outside the pilot's experience level. A forced landing option was available which would have necessitated the closing of both throttles and landing on the Weipa-Coen road, which cut across the extended centreline of the runway at an angle of about 30 degrees. However, once the aircraft entered a spiral descent at low speed and with asymmetric power, recovery was not possible in the height available.

3. CONCLUSIONS

Findings

The aircraft was being operated within weight and centre-of-gravity limits.

No defects that were likely to have contributed to the occurrence were found with the aircraft.

The aircraft's wing tip tanks were selected to feed fuel to the engines.

The right engine was producing considerable power at impact.

The left engine had stopped before ground impact and the propeller was not feathered.

The pilot did not operate the aircraft fuel system in accordance with flight manual instructions.

Both engines were starved of fuel during the initial climb after take-off.

The pilot had probably operated the aircraft exclusively on fuel from the wing tip tanks, which were near empty at take-off.

A suitable forced landing option was available.

There was no warning in the aircraft flight manual to alert the pilot to the danger of operating with near empty wing tip tanks.

Following the entry into the spiral there was insufficient height available for a recovery to controlled flight. Significant factors

The pilot mismanaged the aircraft fuel system.

Both engines suffered a total power loss due to fuel starvation.

The right engine regained power probably as a result of a change in aircraft attitude.

The pilot lost control of the aircraft.

Recovery was not possible in the height available.

4. SAFETY ACTION

During the course of this investigation Interim Recommendation IR 940193 was issued. It stated:

The Bureau of Air Safety Investigation recommends that the Civil Aviation Authority review the approval for the Flight Manual Supplement pertaining to wingtip fuel tanks on BA-2A-21 aircraft. Consideration should be given to adding suitable warnings that the use of partially filled wingtip tanks during take-off, landing and manoeuvring may lead to fuel starvation.

The following response, dated 8 November 1994, was received from the CAA:

"The Interim Recommendation on the aircraft has been reviewed and action in line with the BASI recommendation is being taken to update the aircraft flight manual."