Fuel exhaustion

The pilot had purchased the aircraft earlier in the day and was flying it home to Kingaroy. During the pre-flight inspection he noted that the fuel quantity indication in the sight gauge was 35 litres. This was assessed as adequate for the 20-minute flight, plus reserves.

About 8 km before the destination the pilot again checked the fuel quantity, which was reported to be 10 litres. This was assessed as adequate for the remainder of the flight. Shortly after, the engine failed, and a forced landing was conducted. The paddock chosen appeared to be covered in smooth grass. During the landing roll a wheel struck a clump of the long grass, and the aircraft nosed over, coming to rest inverted.

Examination of the aircraft found that less than three litres of fuel were in the aircraft when the engine failed. The pilot was not aware that the fuel sight gauge was accurate only in flight. There was no mention of this in the aircraft manual.

Factors

1. The pilot had little experience on the aircraft type.

2. The engine failed due to fuel exhaustion.

3. A clump of grass caused the aircraft to nose over.

A video camera was mounted in the cockpit to record the pilot’s actions and comments. This also recorded some of the data presented on the instrument panel and some of the view out of the front windscreen. Most of the record from the video survived the impact and was able to provide a comprehensive record of the flight. Further information was gained from a flight data acquisition unit fitted to the aircraft and from a ground-based video camera which recorded the spin sequence. Later in the investigation the second prototype aircraft was flown and provided additional information.

The aircraft had been spun approximately 60 times prior to this flight. The spins had started with the aircraft set up with low weight and optimal C of G and had progressed to this flight which was conducted at the most critical weight and C of G configuration required for certification.

The spinning flight immediately prior to the accident flight was conducted at a slightly lower weight and at a not so critical C of G. The pilot was not able to recover from the spin on this flight until he had dumped the ballast and deployed the anti-spin parachute. The manufacturers investigation determined that the pilot had been slow to apply the correct control inputs, and the elevator control rigging did not allow full down movement of the elevator. The control cables were reset to ensure that the elevators were able to operate to the stops. After the accident there was not sufficient data available to show whether these corrective actions were effective in restoring full elevator control during a spin, although ground checks had shown full and adequate movement was available.

The investigation into the accident determined that inadequacies in the design of the fin and rudder, and in the rudder control system, had combined with the airflow blanking effect of the horizontal stabiliser, the elevators, and the slab sided fuselage, to preclude adequate spin recovery.

The fin and rudder were assessed as having insufficient area outside of the blanking flow when the aircraft was spinning. The manufacturer has since extended the chord and height of the fin to increase the area outside of that which is blanked during a spin.

The rudder has been extended in chord and lowered in position relative to the tailplane. The fin has been increased in height thereby increasing its aspect ratio. A ventral fin has been fitted to the underside of the fuselage. These measures should increase the effectiveness of the empennage.

The second prototype aircraft was initially flown with essentially the same empennage as the accident aircraft. After some flights on the second aircraft the rudder hinge moment was found to be inadequate. This factor had been masked in tests on the accident aircraft by the use of bungies in the nose wheel steering system. Installation of springs in the nose wheel steering system of the second aircraft showed up the hinge moment inadequacy which the manufacturer has corrected in the redesign of the rudder system.

Analysis of the accident data, and of subsequent test flights, has raised some doubts as to the effectiveness of the application of the elevator control during critical spin recovery. Tests are continuing in an endeavour to assess whether or not there is a problem in this area.

After the accident a review of literature concerning the effectiveness of anti-spin parachute installations was undertaken. This disclosed that the use of a parachute on a long lanyard to pitch the aircraft out of a spin has been rejected in favour of stopping the rotation through use of a larger parachute with no lanyard and short risers.

Analysis

This was a prototype aircraft and some deficiencies and/or problems during testing are to be expected.

With this particular aircraft the fact that the inadequate rudder hinge moment was masked throughout flight testing meant that the inadequate rudder performance during critical spin recovery was not clearly detected until it combined with other factors to become critical. These other factors included an ineffective anti-spin parachute, extensive blanking of the fin and rudder, and flight at the extremes of the weight and C of G envelope.

It is not known what, if any, effect the previous rerigging of the elevator controls had on this flight.

Significant factors

1. The rudder and fin effectiveness was inadequate for the spin test being undertaken.
2. The anti-spin protection systems were ineffective.

The aircraft was not able to be recovered from an intentional spin.

The pilot of the Piper Pawnee had completed spraying the first property for the day. After landing, the operator discussed the next job with the pilot, including the area to treated, the rate of application of the chemical, and fuel management. The operator and his son then drove to the next property to mark a cotton field to be sprayed.

Spraying of the field commenced approximately 30 minutes later. After operating for about 50 minutes the engine stopped as the aircraft was flying at about 10 feet above the crop, during a swath run. The pilot climbed the aircraft to 60 feet, performed a trouble check, and then carried out a forced landing straight ahead into the cotton crop. During the landing the wheels entered soft, muddy conditions. The aircraft decelerated rapidly, pitched onto its nose, and then overturned.

Owing to the wet conditions, it took the operator about 20 minutes to get to the accident site. On arrival he found the pilot walking along a fence line, dazed and in shock, carrying his helmet which had sustained a large crack on the top.

A subsequent examination of the aircraft by the operator found an absence of fuel. The time airborne had exceeded the fuel endurance of the aircraft. In addition, the pilot did not have a reliable means of determining elapsed time to enable him to monitor fuel endurance. It was reported that the aircraft fuel contents indicator was not sufficiently accurate for precise measurement of the fuel tank contents.

The task required the helicopter to carry a surveyor to locations two kilometres apart along north east lines. The time on the ground at each location averaged four minutes and flight time between locations was approximately one minute. Normal endurance for the helicopter, excluding reserve fuel, was 150 minutes (70 l/hr). Due to the amount of time spent with the helicopter ground running at each location, the pilot recalculated the endurance and increased it to 240 minutes (45 l/hr), excluding reserve fuel.

The recalculated endurance was checked daily for any variation in consumption rates. Also taken into account was variation of distance back to the base camp at normal power setting (70 l/hr) for arrival with reserve fuel (25 l) intact on all occasions. On the day of the accident, it was decided to carry two surveyors as they had to return to points which had already been surveyed. These points had been marked by pegs and surveyor tape to identify the locations. The second surveyor was carried to enable easier sighting of the survey pegs.

The pegs proved harder to locate than expected and the helicopter spent more time in the air than anticipated at each location. The aircraft had originally departed camp at 0700 and at 1045, 80 litres of fuel was added from jerry cans carried on board the aircraft. At 1140 the pilot advised the surveyors that they had to return to the camp which would have them back at 1200. A request by one of the surveyors to stop for a gravity reading at a position approximately one kilometre off the track to the camp site was agreed to. Approximately one kilometre from camp the engine stopped. The aircraft was at an approximate height of 80 ft on descent to the campsite with a tail wind of 15-20 kts at the time. The pilot attempted to turn the helicopter into wind to make a landing, however at 120 degrees from its original direction of travel to the left, the helicopter collided with the ground on the side of a dry creek bed.

Seven litres of fuel was drained from tanks, most of which would normally be unusable. At the time of the accident the fuel gauge indicated approximately one quarter full. The pilot did not consider the fuel gauge reliable enough to use as an indication of fuel contents and relied on a combination of dip stick readings, time in operations and fuel logs, based on average daily consumption rates, to determine the fuel state.

The investigation concluded that the extra weight of an additional passenger required more power when flying around to locate the survey pegs and the difficulty in locating the survey pegs required more hovering (at higher power settings) than anticipated. Overall hourly consumption rate had increased above planned levels leading to fuel exhaustion well before the pilot's fuel logging indicated it might happen.

The flight was intended as a brief pleasure/practise flight in the local area in an aircraft borrowed from a friend.  The pilot had only 90 minutes previous flying experience in the aircraft while sitting in the right front seat with the owner/friend acting as pilot-in-command in the left seat.  However, the pilot had flown several hours as pilot-in-command of a Debonair, which is similar, and advised that his friend had pointed out the differences between the Bonanza and the Debonair.  The accident flight lasted only 30 minutes and was the first time the pilot had acted as pilot-in-command of a Bonanza.

The pilot advised that, as part of the preflight inspection, he had visually checked the contents of both main fuel tanks and assessed that there was enough fuel on board for a short flight.  He did not dip the tanks.  He started the engine on the left main tank and maintained that selection in flight until the engine lost power on final approach for runway 35 at Tyabb.  He then changed the fuel selector to the right main tank.  The engine did not regain power. The aircraft touched down on its wheels in an open paddock about 400 metres short of runway 35 threshold.  During the landing roll the aircraft ran through a farm fence before coming to rest about 200 metres short of the threshold.

An inspection and tests conducted after the accident confirmed that the engine had failed due to fuel starvation.  The fuel gauges read zero.  No fuel leaks were found.  Both main fuel tank floats were resting on their static low stops, namely the bottom of the rubber fuel cells. After the aircraft was recovered, the engine was started and ran normally after air was purged from the fuel lines.  When asked about the low fuel gauge readings at the commencement of the flight, the pilot said that he did not take too much notice of them because he had visually assessed the fuel level as adequate for the flight and that flying instructors in the past had told him that fuel gauges could not be believed because they were notoriously inaccurate in light aircraft.

Total engine time for the flight was about 35 minutes.  When both main tanks were drained after the accident, one third of a litre of AVGAS drained from the left main tank and eight litres from the right main tank.  Both of the auxiliary fuel tanks were empty.  The approved flight manual lists the unusable fuel in both main tanks combined as 22.7 litres (i.e. 11.35 litres per main tank).  The flight manual also states, "Do not take-off if fuel quantity gauges indicate in yellow band or with less than 11 Imperial or 13 U.S. gallons in each main tank" (i.e. 49 to 50 litres in each main tank).  The pilot said he did not recall this comment in the flight manual.

Pilots experienced in this model Bonanza advised that it uses about 42 to 45 litres of AVGAS per hour.  VH-AYU's engine somehow managed to use about 11 litres of the unusable fuel from the left main tank before it lost power.

When the pilot selected the right tank, its fuel level was already within the unusable fuel range; it contained only about 9 litres.  There was probably insufficient time and insufficient fuel in the right main tank to achieve adequate fuel flow/pressure to restart the engine before the aircraft touched down in the paddock.

Significant factors

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

1. The pilot's visual assessment of the fuel quantity within both main tanks was incorrect.
2. The pilot ignored the fuel gauge readings.
3. The pilot's knowledge of the flight manual content was inadequate.
4. The engine failed due to fuel starvation.

The pilot said that he had been working for the operator for one week prior to the accident. He was employed on a casual basis, based in Cootamundra.

After conducting his normal freight flight to Hay, he arrived back at Cootamundra at about 1845, whereupon he unloaded the freight he had been carrying, and went to his car to collect personal belongings for a ferry flight to Bankstown. At the same time, the aircraft was being refuelled. A total of 313 litres of fuel was added to the aircraft, filling all tanks with the exception of the right auxiliary, which was filled to 20 litres less than capacity. By the time the pilot had returned to the aircraft the refueller had left. He said he carried out a fuel drain but then became distracted by the imminent arrival of another aircraft. He subsequently believes he did not check the status of the fuel caps.

The aircraft departed Cootamundra at about 1912 for an IFR flight to Bankstown. The planned cruising level was 5000 feet in order to minimise delays with entry to controlled airspace. Main tanks were selected for take-off and initial climb. Shortly after take-off, the left and right auxiliary tanks were selected to feed their respective engines. During the cruise the pilot said that he noticed, after some time, that the fuel contents indicators appeared to be giving erratic readings. He was not concerned at this because he was confident the aircraft was carrying a very large margin over the fuel required for the flight.

As the aircraft passed Bindook VOR the pilot said he changed back to both main tanks. Shortly after this the left engine stopped. He commenced to go through the appropriate checklist items when the right engine also stopped. He immediately changed back to the auxiliary tanks without effect, then tried a number of tank/crossfeed selections, combined with various fuel pump and mixture settings. A momentary surge of power from one engine was all that could be achieved. The pilot gave a Mayday call, extended half flap and reduced speed to 75-80 knots. Nothing could be seen outside the aircraft due to darkness, low cloud and rain.

The aircraft collided with trees in rugged terrain and came to rest, relatively intact. The pilot said he struck his head on the instrument panel, sustaining a small cut on the forehead. At the time of impact, he did not have his shoulder harness secured, being only restrained by his lap belt. He had unbuckled the shoulder straps during cruise because they were chafing his neck. After the loss of engine power, he did not have sufficient time to refasten the harness.

Immediately after the aircraft came to rest, he kicked open the main door and rapidly evacuated the aircraft, as he was concerned that the aircraft may have caught fire. There was no fire and so he was able to re-enter the aircraft after a short time and use the aircraft radio to notify his position, and to communicate with rescuers. Although located that evening by rescue helicopter, due to poor weather conditions, and hazardous terrain, he was not extracted from the crash site until the following morning.

Inspection of the wreckage revealed that all four fuel tank caps were unlatched, allowing fuel to be vented overboard during flight. It was subsequently reported that the refueller had been specifically instructed by a previous company pilot not to latch the fuel caps after refuelling. This procedure required the fuel contents to be checked, then the fuel caps to be fastened, by the pilot-in-command. The new pilot of VH-USP was aware of this procedure, however, when he failed to check the fuel caps there was no fail-safe capability to prevent a consequent loss of fuel during flight.

The pilot had flown the helicopter from Darwin to Jabiru, carried out some local flying at Jabiru and then returned to Darwin on the day of the accident. As the helicopter was approaching Darwin the pilot was instructed by an air traffic controller to hold position in the Palmerston area and await further clearance. Shortly afterwards the engine stopped, and the pilot was forced to complete an autorotational landing. The pilot misjudged the approach, and the aircraft landed heavily.

The pilot did not complete a flight plan prior to the flight and no evidence was found to indicate she used any form of formal fuel management to ensure that fuel available met the required reserves.

The aircrafts total fuel capacity of 200 L provided for an endurance of approximately 2.6 hours at a normal fuel consumption rate of 75 L/hour. The flight to Jabiru took 2.5 hours. A total of 194 L of fuel was required to fill the tanks following this flight. The tanks were also refilled following the local flying. Although almost all the fuel had been exhausted on the flight to Jabiru the pilot departed for the 2.5 hour flight to Darwin without having made any alternative fuel arrangements. The fact that the aircraft had almost run out of fuel on the flight to Jabiru did not register.

When the pilot was instructed to hold position in the Palmerston area and await a further clearance she advised the controller that the aircraft was low on fuel but she did not communicate any urgency about the situation. Ten minutes later, whilst still in a holding pattern, the engine stopped as a result of fuel exhaustion. The helicopter had been airborne for 2.6 hours when the engine stopped.

The pilots actions indicate she was never sufficiently aware of the aircraft's fuel situation. The lack of planning and the failure to use a formal management procedure probably exacerbated the situation.

The pilot refuelled the aircraft to full tanks on the evening prior to the accident. The aircraft remained parked at Griffith aerodrome overnight.

The next day, the pilot completed two tasks of 0.8 hours each. He then conferred with his chief pilot, about the fuel endurance of the aircraft, before commencing another 0.8 hour task.

After a flight time of 0.7 hours, while completing the "clean-up" run, the engine stopped. The pilot completed the emergency checks but was unable to restore engine power. He was then faced with a forced landing in a rice paddock. During the landing roll, the aircraft struck a dirt bank which bent the landing gear and damaged the fuselage and hopper.

The pilot was familiar with the fuel usage rate of the aircraft and planned on a rate of 100 litres per hour. The fuel capacity of the aircraft was 328 litres and at the expected usage rate should have allowed an endurance in excess of three hours. The pilot believes that the aircraft was tampered with overnight. The fuel contents were not checked prior to departure that morning.

HISTORY OF THE FLIGHT

VH-EPJ was engaged in an instrument flight rules charter flight, with two passengers, from Telfer to Port Hedland. The flight had departed Port Hedland at 0650 that morning, arriving at Telfer at 0759. The aircraft remained at Telfer until 1526 after which, it departed for Port Hedland.

At a position 138 km south-east of Port Hedland, whilst cruising at 6,000 ft, the pilot observed that the left fuel quantity gauge was indicating empty. He selected the left fuel selector to 'crossfeed' and turned on the left fuel boost pump. After checking his fuel calculations, the pilot elected to continue the flight to Port Hedland. Within two minutes the left engine began surging. This was followed by surging in the right engine. The pilot completed the basic engine failure drills; however, due to his concern over control difficulties resulting from the yawing caused by the surges, he elected to shut down both engines, feather the propellers, and conduct an emergency landing. The aircraft landed without further incident on the Port Hedland to Marble Bar road.

After obtaining fuel for the aircraft the pilot flew it to Port Hedland.

PERSONNEL INFORMATION

The pilot of VH-EPJ, at the time of the occurrence, was also the Chief Pilot (CP) of the operating company. The CP was the only pilot to operate VH-EPJ after 29 June 1994. The pilot had completed his Beechcraft Baron endorsement in a BE55 which has a different fuel tank configuration to the BE58. During this endorsement the determination of fuel contents using the filling point tabs was discussed. Because the fuel tank arrangement in Baron aircraft does not lend itself to easy determination of the fuel contents, other than through the gauging system, it was recommended to the pilot that he always keep an accurate manual fuel log when operating the aircraft. Although the presence of wing mounted fuel gauges, in the BE58 was mentioned, the specifics of fuel management in the BE58 were not covered. This was left for the pilot to pursue. An endorsement in a BE55 qualifies a pilot to act as pilot-in-command of a BE58.

AIRCRAFT INFORMATION

VH-EPJ is fitted with rubber bladder type wing fuel tanks. An inspection of these tanks indicated that they had not collapsed at the time of the occurrence. The aircraft owner advised that the fuel gauging system had been calibrated twelve months prior to the occurrence and that the average normal fuel consumption for VH-EPJ was 113-115 L/hour.

Wing-mounted fuel quantity gauges provided the potential to indicate fuel quantities between 40 and 60 US gallons (151 L - 227 L) in each wing tank. The fuel tanks were fitted with tabs which had the potential to give a fuel indication of approximately 302 L in each tank.

The aircraft was not fitted with a placard or decal which indicated, to a pilot, what the tab indication meant. Nor was the information included in either the aircraft flight manual or company operations manual. The left and right exhaust gas temperature gauges (EGT), used to assist in accurately leaning the engine fuel mixture in flight, were unserviceable. When power was applied one gauge went immediately to a maximum reading and the other remained at zero. The EGT unserviceability was not entered in the aircraft's maintenance release document.

No evidence (fuel staining) was found which would indicate that fuel had vented from the aircraft in flight. The aircraft performed normally during the ferry flight to Port Hedland following the occurrence.

COMPANY DOCUMENTATION

The company operations manual contains the following requirements:

• Section A:3:6:

'Fuel Usage Records. The aircraft flight time and fuel log sheet includes a section which enables a continuous check of the fuel usage and fuel remaining at the completion of each trip. The pilot in command shall complete this section at the completion of each trip. Fuel used by each aircraft shall be calculated on a monthly basis by the Chief Pilot and fuel consumption determined'.

• Section A:4:6:

'The Pilot in Command is to ensure that sufficient fuel is carried to proceed from the departure aerodrome to the destination aerodrome or alternate aerodrome if required...All company aircraft shall carry a fixed reserve of 45 minutes at the holding rate and a variable reserve of 15% of the flight fuel at the cruise consumption rate. The flight fuel is to be calculated at the consumption rate for each aircraft shown in section B:1:1'.

• Section B:1:1:

'Flight Planning. Use greater of A) 180 knots at 110 litres per hour from departure to destination plus alternate if required, plus 15%, plus 45% (79 litres) or B) single engine use 125 knots 60 litres per hour from critical point to destination plus 15%, plus 10 minutes (18 litres). Taxi Fuel: 10 litres' [plus 45% should read 45 minutes - typographical error].

The operations manual did not contain any information on the determination of fuel contents other than by refuelling the aircraft to full tanks and/or using a manual fuel logging system. Nor did it contain information which would indicate to the pilot that other conditions, such as extended climb time or low altitude operations would affect the fuel burn.

PILOT OBSERVATIONS

The pilot indicated that he was not aware of any method of determining the fuel contents in a BE58, other than by reference to the main fuel gauges, except for refuelling the aircraft to full tanks and maintaining an accurate fuel log from then onwards. The aircraft had been refuelled, for the occurrence flight, at Port Hedland and the pilot had completed fuel drain checks for water at both Port Hedland and Telfer. During the flight from Telfer, he had checked the fuel indications each 10 minutes and he did not notice anything abnormal until immediately before the surging started. At that point the pilot noticed that the left fuel gauge was indicating empty and the right gauge 1/4. The right gauge had dropped rapidly to about 1/8 when the right engine also started surging.

The pilot initially thought there was a problem with the contents of the left tank only and that he had sufficient fuel in the right tank to continue to Port Hedland. He was aware that he would arrive at Port Hedland (a further 27 minutes flying) with little or no fuel remaining. His initial decision was to continue with the flight. When the right engine started surging, he knew the problem was one of exhaustion rather than starvation and elected to complete a precautionary landing.

As the EGT gauges were unserviceable the pilot relied on the fuel flow gauges to lean the fuel mixture to the cruise setting.

The pilot also indicated that he was concerned that the aircraft could be damaged if it was left parked on the road for any length of time. He did not make an attempt to contact a licensed aircraft engineer to inspect the aircraft before proceeding to Port Hedland as he knew it was unlikely that one would be available at short notice.

FUEL CALCULATIONS

The pilot had determined that 430 L of fuel was onboard the aircraft at Port Hedland, prior to departure, by reference to the company fuel remaining record, for which, as the only pilot of the aircraft since the 100 hourly inspection on 2 June 1994, he had been solely responsible. The record indicated that the fuel tanks had been last filled to capacity on 17 July 1994, and that the aircraft had subsequently flown some 38 hours.

The pilot had maintained the fuel record from that time by:

• including fuel added to the aircraft (using known amounts from drums or refuelling contractors) and
• by deducting fuel used (calculated using 110 L/hour).

The pilot used 110 L/hour for flight times recorded by the flight time meter, plus an allowance for fuel usage during taxi of between zero and 15 L, depending on the actual taxi time. He had determined the 110 L/hour usage rate as a result of a flight to and from Perth in July 1994 which had permitted the use of full fuel tanks. The operations manual also indicated that 110 L/hour should be used for flight planning. Subsequent monthly checks of fuel consumption rates, as required by the company operations manual, had not been completed.

The pilot indicated that he mistrusted the fuel quantity indications provided by both the main fuel indicating system and the wing mounted fuel gauges as their readings did not correspond with the contents indicated by his fuel log. Although he believed the gauging system to be inaccurate, the pilot did not enter it as an unserviceable item in the aircraft's maintenance release. As a result of the pilot's mistrust of the aircraft fuel quantity gauges, the company fuel remaining record was the sole source of fuel quantity information used by the pilot.

During the investigation, the pilot reported that following the incident he had detected an error in the fuel remaining record. An entry on 4th October 1994 indicated a fuel added amount of 200 L when the actual amount had only been 100 L. The pilot indicated that he had ordered, and believed he had received, 100 L per side. However, the fuel docket issued by the refuelling agent indicated a total of 100 L.

CAA SURVEILLANCE

The pilot was interviewed by the CAA on 16 June 1994 and granted CP approval on 20 June 1994. The CAA's Aviation Safety Surveillance Program calls for one operational surveillance visit per year on an operator such as the one involved in this occurrence. No operational surveillance had been carried out since the appointment of the new CP. A CP is appointed only after they have satisfied the authorised CAA officer, at interview, that they have the qualifications, knowledge, and experience to perform the duties set out in CAO 82.0. The authorised CAA officer advised that the CP, in this case, had satisfied the CAO requirements.

ANALYSIS

Cause of the Surging

Possible explanations for the surging were:

1. A non-fuel-related problem in the engines

- This possibility was considered very unlikely as both engines were similarly affected at the same time.

2. Fuel quality problems

- This possibility was considered very unlikely as the previous refuel had been conducted at Port Hedland using high standard refuelling equipment. Further, the pilot had completed fuel drain checks at both Port Hedland and Telfer with negative results.

3. Fuel starvation due to a mechanical defect in the aircraft (such as collapse of the fuel tank bladder) or the fuel system, resulting in interruption of the delivery of fuel to the engine, despite adequate fuel remaining on board the aircraft.

- This possibility was considered unlikely in view of the subsequent successful flight from the incident site to Port Hedland and an inspection of the fuel system did not disclose a collapsed bladder or any other problem.

4. Fuel exhaustion.

- This is considered the most likely cause and was the focus of the investigation. The following possible reasons were considered.

(a) There were faulty fuel drain valves, or the fuel drain valves were not fully closed.

- There was no evidence of fuel leakage around the fuel drain valves to support this possibility.

(b) There was a theft of fuel.

- There was no evidence to support this possibility.

(c) The pilot had miscalculated the fuel contents.

Miscalculation of fuel contents

An analysis of the flight suggests that the likely fuel on departure from Port Hedland, assuming a usage rate of 113 L/hour (based on information provided by the aircraft owner), 10 L taxi allowance and fuel exhaustion, was 226 L.

total of 130 L and Telfer to the incident site was 40 minutes @ 113 L/hour for a sub-total of 76 L) and adding the taxi fuel (two periods of taxiing @ 10 L each for a sub-total of 20 L).

As the calculated amount of fuel was 226 L, a discrepancy of 204 L existed with the 430 L calculated on the pilot’s fuel remaining record. Whilst 100 L was accounted for earlier in the report, a discrepancy of 104 L remained. This amount may be attributable to an actual fuel flow rate in excess of 110 L/hour. Over the 38 flight hours since the last positive check of fuel on board, a rate of 113 L/hour would account for the discrepancy.

A difference of 3 L/hour is not considered significant, on any single flight if the pilot is aware of the actual fuel state on departure, as it would be adequately covered by the variable (15%) and fixed reserve (45 minutes) that must be carried as part of the operations manual requirements. However, such a small difference can be significant over a longer period of time as was the case leading up to this occurrence. Had the pilot, in his role as CP, carried out the monthly calculation of fuel usage, as required by the operations manual, he probably would have been aware of the higher-than-expected fuel usage rate and made allowances for it.

SIGNIFICANT FACTORS

1. The pilot was not sufficiently aware of all the methods for determining the actual fuel contents.
2. The use of 110 L/hour for both fuel planning and actual consumption was insufficient to cover all types of operations in the Beechcraft Model 58.
3. As CP, the pilot did not calculate the actual fuel consumption on a monthly basis therefore he deprived himself of more accurate fuel consumption figures on which to base his fuel log.
4. The pilot believed, probably incorrectly, that the fuel indicating systems were inaccurate and as a result he did not make sufficient use of them in his fuel calculations.
5. When convinced that the fuel indicating system was too inaccurate to use, the pilot did not place the system unserviceable. This deprived him of another method of determining the fuel contents.
6. Both exhaust gas temperature gauges were unserviceable, and the pilot did not attempt to have them repaired. This deprived him of accurate fuel mixture control which, in turn, may have led to a higher-than-expected fuel consumption.
7. The pilot made an error in one entry in his fuel log which created the impression that the aircraft contained 100 L more fuel than it actually did.
8. The operator's documentation either did not provide sufficient fuel management guidance to the pilot, or the guidance was incorrect.

The pilot had been operating the aircraft in the area for several weeks in support of parachuting operations. Towards the end of the day, he requested to be refuelled, but the refueller was busy and could not immediately attend to the request. The pilot departed without refuelling and whilst turning onto finals at the conclusion of the sortie, the engine sputtered and stopped. In order to avoid undershooting and possibly landing in houses, the pilot elected to land in a clear area of mangrove. When the wheels sank into the sift surface, the aircraft overturned.

Minimal quantities of fuel were discovered in the aircraft and the fuel system after it was righted, and the investigation did not discover any reason for the engine stoppage other than fuel exhaustion. The most likely explanation for the fuel exhaustion was the poor fuel management practices of the pilot.