Fuel starvation

The pilot reported that while cruising at 1,000 ft the engine started to make unusual noises. He decided to make a precautionary landing on a beach. During the landing roll the aircraft entered soft sand. The nose gear broke off and the propeller was bent.

An inspection after the accident found one fuel tank was empty. No fault was found with the engine. A new nose gear and propeller was fitted, the engine was run, and the aircraft was flown off the beach and returned to its base.

History of the flight

The pilot conducted a scenic flight of approximately one hour duration from Stawell around the Grampians with three passengers on board.  At the end of the flight, the pilot approached Stawell from the west and joined the circuit via an upwind leg to the south, then a right circuit for a landing on runway 18.  In the area of late downwind/early base the engine stopped.  The pilot continued turning right towards the aerodrome, but it became obvious that the aircraft was not going to reach the aerodrome without engine power.  He performed some checks but was unable to restore engine power.

There was no area suitable for a forced landing between the aircraft and the aerodrome because the area had moderate tree cover.  The pilot positioned the aircraft towards a clump of small trees and warned his passengers of the impending impact.  The aircraft stalled into the trees and ignited on impact with the ground. All occupants escaped, but three received serious burns.  The aircraft was destroyed by impact forces and fire.

The engine

Although most of the fuselage and right-wing area were consumed by fire, the engine was not fire damaged.  The firewall was intact and the engine cowl, although heat affected, was not burnt. The engine was recovered and subjected to a thorough examination which was unable to determine any reason for the engine failure or why the engine was not capable of producing full power.

The pilot

The pilot was checked in this aircraft by an instructor two weeks prior to the accident. The check involved a check on the aircraft type, a constant speed propeller endorsement and a retractable landing gear endorsement.  Prior to this check the pilot had flown the aircraft once with the owner occupying the right seat as pilot in command.  The instructor who conducted the check flight reported that the pilot handled the aircraft well and was knowledgeable on its systems. After the check flight, the pilot did not fly the aircraft again until the day of the accident.

Fuel considerations

Calculations were made of estimated fuel usage against time flown since the aircraft was last known to have had full tanks.  The result was that at most there was a total of 45 litres remaining in the tanks when the engine failed.  The distribution of the fuel remaining could not be determined.  If evenly distributed, there would have been 22.5 litres per tank.  The pilot said he had the selector on the left tank which by gauge indication had the higher quantity of fuel.  Fire damage at the scene indicated that the right tank probably contained more fuel than the left.

Other evidence

The pilot's operating handbook for the aircraft type warns about taking off with less than 13 US gallons (49 litres) in each main fuel tank.  If a main fuel tank contains less than 49 litres, there is a possibility that a tank outlet will be uncovered (i.e. no fuel available at the outlets and air will be sucked into the fuel lines) during a tight turn while taxiing.  If such a turn is executed immediately prior to take-off, it is possible for the engine to fail during take-off.  It is also possible for a tank outlet to be uncovered during unbalanced flight and accordingly the pilot's operating handbook contains time limits for "maximum slip duration" consisting of 20 seconds for aircraft fitted with unbaffled fuel tanks and 30 seconds for aircraft fitted with baffled tanks.

The pilot advised that when he made the right turn to join the downwind leg of the circuit, he and his passengers were watching a preceding aircraft land.  To facilitate this, he kept the bank angle low and applied right rudder to complete the turn.  This would have resulted in an unbalanced turn.

If the engine stops due to fuel starvation, the procedure for restarting involves selecting the tank which contains the most fuel, retarding the throttle and turning the boost pump on.  Even with these actions correctly taken, it can take a considerable time to restart the engine.  In a recent case involving a similar aircraft, the pilot of that aircraft reported that it took 20-25 seconds to restart the engine with the boost pump set in the on position.  In the present case the pilot completed a series of checks to determine the cause of the engine failure but did not turn the boost pump on. He believed he positioned the throttle to one quarter open because that was what he had been trained to do.  When the wreckage was examined, the throttle was found in the fully open position. The propeller and mixture controls were also in the full forward position.

The severity of the post-impact fire was discussed with an experienced fire investigator. His advice was that a fire of the intensity that had occurred could have been fuelled with less than 45 litres of aviation gasoline.

The post-accident fire damage to the right wing and fuselage precluded any assessment of loss of fuel in flight via a leak somewhere in the system.  The left wing was largely undamaged by fire and there was no evidence of any fuel leakage from that wing.

Analysis

Examination of the engine found no reason why the engine stopped.  Calculations of time flown against fuel usage showed that at the time the engine failed there was probably a total of no more than 45 litres of fuel in the tanks. Fuel distribution could not be determined. The pilot believed that the left tank contained more fuel than the right tank, but the post-impact fire damage suggested that there was more fuel in the right tank.

Immediately prior to the engine failure, the pilot made an unbalanced turn to the right with the left fuel tank selected.  With the amount of fuel remaining in the tanks, this probably uncovered the outlet in the left tank and starved the engine of fuel.  After the engine failed, the pilot did not turn the boost pump on and may not have correctly positioned the throttle, as recommended in the pilot's operating handbook, in order to restart the engine. However, even if the pilot had performed all actions correctly, it may not have been possible to achieve a restart in the time available.

Conclusions

Findings

1. The pilot was correctly licensed and qualified to fly the aircraft.
2. The pilot had low total flying experience and low experience on type.
3. When the aircraft approached Stawell at the end of the flight, it was calculated that there was no more than 45 litres of fuel remaining in the aircraft fuel tanks.
4. Shortly after completing a 180-degree turn onto the downwind leg of the circuit, the engine stopped.
5. In the limited time available, the pilot was unable to determine the cause of the engine failure or achieve a restart.
6. The aircraft was unable to reach the aerodrome from the position at which the engine failed.
7. The area between where the engine failed and the aerodrome was unsuitable for a forced landing.
8. A thorough examination of the engine found no fault or any reason why the engine was not capable of producing full power.
9. The pilot's operating handbook, in the limitations section relating to fuel management, warns against taking off when the fuel quantity gauges indicate in the yellow band or with less than 13 US gallons (49 litres) of fuel in each main tank.  The same section also specifies maximum slip durations for baffled and unbaffled tanks.

Significant Factors

1. When the aircraft approached its destination, it was calculated that there was no more than 45 litres of fuel remaining in the aircraft fuel tanks.
2. The pilot made a 180-degree unbalanced right turn onto the downwind leg of a circuit. It is probable that the turn resulted in the outlet of the left fuel tank being uncovered.
3. The engine failed over an area that was unsuitable for a forced landing.
4. The pilot was unable to restart the engine.

On base leg for runway 26 at Portland the left engine failed without any prior warning. The crew secured the engine, and a successful single engine landing was accomplished.

The engine was removed and transported to the operator's maintenance facility for investigation. During disassembly of the accessory gear drive it was found that the first idler bearing had collapsed. The bearing supported the accessory gear assembly, part number 3103601-6.

When the bearing collapsed the gear moved about the shaft axis and disengaged from the fuel pump spur gear, part number 3102268-2. With the spur gear disengaged, the fuel pump was not able to supply fuel to the engine which shut down without warning, as reported by the crew.

The failed bearing was returned to the manufacturer for investigation, however the factors surrounding the failure have not been advised.

The manufacturer did advise that they have initiated a program to improve the reliability of the first idler bearing by:

- changing from a ball to a roller type bearing,

- changing the idler housing material, and

- improving the retention of the housing thereby improving support and changing the natural frequency.

The program is now at the implementation stage. The operator has determined to retrofit the improved first idler assembly in accordance with the manufacturer's recommendations.

The pilot reported that he had refuelled the aircraft to full tanks on the day prior to the accident. He intended to carry out some cattle spotting on the way to Eastmere where he intended to refuel. After circling some cattle, he had headed for Eastmere and noticed that the right hand fuel gauge was indicating near empty. He then selected the left tank and shortly after the engine stopped.

The pilot reported that his only option was to attempt a landing, as he was at low altitude. During the landing the aircraft struck trees, the nose gear was torn off and the engine mounts were broken. The aircraft had been flown for approximately 4 hours since the last refuel. It was not determined whether the aircraft had run out of fuel, or the fuel tank outlets had been uncovered, allowing air into the fuel system, during a turn.

The pilot stated that he departed Lismore at approximately 1030 hours for a flight to Evans Head. He carried out two touch and go landings at Evans Head before departing for the return flight to Lismore. At about 1115 when the aircraft was cruising at 1500 feet, the engine lost power and began surging. The pilot said he selected full rich mixture, applied full carburettor heat and gave two strokes on the fuel wobble pump at which time complete engine failure occurred. During this time the aircraft had descended to 1000 feet and the pilot selected a paddock and began an approach at 70 knots.

After flaring slightly to clear 20 metre high trees at the paddock boundary a soft touchdown was made at about 50 knots. The pilot said he had deviated slightly from his chosen path between scattered trees as forward visibility in the aircraft when on the ground is almost nil. Approximately 40 metres after touchdown the right upper wing clipped a tree spinning the aircraft clockwise. The right lower wing and aileron contacted the ground during the rotation. After vacating the aircraft, the pilot noticed flames in the rear of the engine and under the fuselage. The flames were extinguished with water from a nearby cattle trough.

Examination of the engine revealed that the gascolator bowl retaining clip had partially separated allowing the glass sleeve to become dislodged, and this had caused fuel starvation.

The pilot was faced with a forced landing when he inadvertently left the fuel selector on a near empty (left wing) tank. The purpose of the flight had been to inspect a property and when the engine faltered, due to fuel starvation, there was insufficient time and height available to restart the engine using fuel from the right tank.

The aircraft struck a beast, with the left main gear, during the flare. The gear leg was bent back and during a short landing roll, the left wing struck the ground.

The pilot was positioning the helicopter for the first spray run.  As he lowered the collective lever and commenced a turn, he noticed that the rate of descent was higher than usual and that the dual tachometer needles had split. Realising that the engine had lost power, he performed an autorotative descent from less than 100 ft above ground level (agl).  During the touchdown on slightly sloping terrain, the right front skid tube broke, and the helicopter rolled on to its right side.

During the helicopter retrieval, the engineer estimated that he drained 4 to 5 litres of AVGAS from the helicopter's undamaged fuel tank.  The drained fuel was not accurately measured. The pilot's estimate of drained fuel was 6 to 8 litres.  No evidence was found of fuel having leaked onto the ground prior to or during the retrieval.  The engineer found no evidence of fuel leaks, blockages, water or significant foreign matter in the helicopter's fuel system.  His opinion was that the engine lost power due to fuel starvation.

The pilot cannot remember the fuel gauge reading immediately before the accident.  The failure occurred about 1.5 minutes after take-off from the loading base and 34 minutes flight time since the last refuel.

The pilot had refuelled approximately every 30 minutes of flight time during the previous four hours of spraying. 

After refuelling, he did not dip the tank to measure the fuel accurately. He advised that the last refuel consisted of 60 turns of a rotary hand pump.  He believed that every turn of the handle had pumped 0.8 litre into the fuel tank. In his opinion, the fuel gauge reading compared with the estimated amount of fuel pumped into the tank at each refuel.

A warning in the Hiller 12E flight manual states: - "Operating with fuel indicator in the yellow arc during sideward or rearward flight may result in loss of power", because the fuel tank pickup pipe may be exposed and cause the fuel pump to momentarily suck air in lieu of fuel.  The helicopter was not flying sideways or rearwards when engine power was lost.  The unusable fuel listed in the flight manual was only 1 litre for normal level flight.

The pilot thought that the engine did not stop completely during the descent but ran down to idle and that it idled very briefly after touchdown because he saw a small post-crash fire caused by the drift marker oil, a very light oil, dribbling into the exhaust.  Engineers were doubtful that the engine could have run on the ground with the helicopter steeply on its right side with the two carburettor float bowls side uppermost.

The pilot did not dispute that the helicopter appeared to have experienced fuel starvation.  However, he believed 48 litres of fuel were added at the last refuel before the accident. Since the helicopter had consistently used 60 to 62 litres per hour in recent times and because its tank was not empty at the commencement of the last refuel, in excess of 13 litres of AVGAS should have been in the fuel tank when the power loss occurred.

Several litres of AVGAS have not been accounted for.  No evidence was found to indicate that the drum refuelling pump was unserviceable.

It has not been possible to resolve discrepancies in fuel since the accident; nor has any fault been found with the aircraft which may have contributed to the accident.

Whilst returning from the training area after a period of dual instruction, the engine suddenly stopped. Engine failure cockpit checks, which reportedly included selecting the alternate fuel tank, failed to restore power. The pilot declared an emergency and turned the aircraft toward a racecourse, the only available area for a forced landing. The aircraft touched down safely but the nose landing gear leg failed due to the action of heavy braking on soft earth.

Subsequent investigation determined there was no fuel in the right fuel tank, although the left tank contained about 48 litres. The engine started and ran normally when the left tank was selected. The instructor pilot had failed to adequately monitor the rate of fuel usage from the right tank during the flight and the engine consequently stopped due to fuel exhaustion.

The pilot reported that the aircraft engine lost power when he made a power adjustment whilst on final approach. The propeller feathered and the aircraft landed short of the runway on unprepared ground, incurring substantial damage. 

The aircraft was being used for parachute drops from 14,000ft. When the last parachutist left the aircraft, the pilot would place the aircraft in a steep spiralling descent. During this type of descent, the pilot was known to exceed the 60 degree angle of bank limits for the aircraft.

Low fuel states were reported as being used for the paradrops. It is probable that the fuel flow from the wing cells to the collector tank (18 litre capacity) was interrupted during the descent and air entered the system. The fuel pump was not designed to operate in other than a full collector tank. As a result it is likely that the fuel flow to the engine was interrupted, resulting in engine flame out.

The pilot had been engaged in sheep spotting and was returning to refuel when the engine lost power about 2km from the airstrip at a height of 500 feet. The aircraft was landed on a gravel road, but directional control was lost in the loose gravel, and the wings contacted some low scrub. When the nosewheel was lowered to the ground, the aircraft veered to the left, and came to rest on the propeller spinner, the nosewheel, and the right wingtip.

The fuel tanks were subsequently drained on site and yielded approximately 45 litres of fuel from the right tank. The fuel had drained from the left tank to the right tank because of the aircraft's attitude. The pilot said he had been airborne for 3.5 hours and using the consumption rate of 45 litres per hour, had calculated that he should have had 48 litres of fuel remaining when the engine lost power. However, he had not flown a Cessna 182A before, had not read the flight manual, and was unaware of the unusable fuel quantity. He had been flying a later model which had less unusable fuel.

The flight manual shows that the unusable fuel quantity is 37.7 litres, and useable fuel quantity is 208 litres. The pilot stated that the fuel selector was selected to both tanks (left and right) for the duration of the flight. During the flight the aircraft was turned frequently, and the direction of turn was predominantly to the left. This may have caused fuel to drain from the right wing to the left and allowed air into the system when the quantity fell below the lowest useable level.