Fuel exhaustion

Sequence of events

On 5 March 2005, at about 1240 Western Standard Time, an Avions Pierre Robin R-2160 aircraft, registered VH-OXY, was inbound to Jandakot Airport, WA. The flight was being conducted in the private category and the pilot was the sole occupant of the aircraft.

The pilot recalled that the aircraft was about 2 ½ NM west of the aerodrome and at an altitude of 1,200 ft when the engine suddenly lost power. The pilot was attempting to make an emergency landing on a residential street, when the outboard portion of the right wing collided with a suburban power pole. The aircraft rolled inverted before impacting the ground. The aircraft was substantially damaged. The pilot sustained minor injuries and vacated the aircraft without assistance. There was no spillage of fuel at the accident site and no post-impact fire. The maintenance personnel who attended the accident site inspected the aircraft's fuel tank and found that it did not contain any fuel.

An overhauled engine had just been fitted to the aircraft and the pilot reported that he was carrying out the engine manufacturer's procedure for engine break-in¹. That procedure included that, after reaching cruise altitude, a pilot conducting the recommended 2.5 hours break-in flight should:

• Reduce the engine power setting to 75% maximum rated for the first hour of the flight. Data contained in the engine manufacturer's operator's manual indicated that 75% power was obtained at 2,450 RPM, and that the fuel consumption at that power was about 38 L/hour.
• Alternate the engine power between 65% and 75% during the second hour. The engine manufacturer's operator's manual indicated that 65% power was obtained at 2,350 RPM and resulted in a fuel consumption of about 34 L/hour.
• Operate the engine at 100% power for 30 minutes, provided that the engine and aircraft are performing within the published operating manual specifications. Data extracted from the engine manufacturer's operator's manual indicated that 100% power would be achieved at 2,700 RPM and resulted in a fuel flow of about 53 L/hour.

Based on data contained in the engine manufacturer's operator's manual, it was estimated that the recommended engine break-in flight could have consumed between about 108 and 137 L of fuel.

The pilot reported that, during the engine break-in flight, he operated the aircraft's engine as follows:

• between 2,500 and 2,600 RPM for the first 2 hours of the flight
• at 2,700 RPM for the remainder of the flight before returning to Jandakot. The aircraft engine lost power 2 hours 41 minutes after take-off.

The pilot stated that he used a calibrated dipstick to dip the aircraft's fuel tanks prior to the flight, and that the tanks contained 118 L of fuel. He had expected the aircraft to use 35 L/hr, which was the standard fuel consumption used by the company for flight planning in that aircraft type.

The aircraft was equipped with an annunciator panel that included a warning light to indicate a low fuel quantity. However, black adhesive tape had been stuck over that panel, preventing the pilot's view of the low fuel quantity warning light. Neither the aircraft's owner/operator nor the relevant maintenance organisation could explain why the tape was stuck over the panel.

1. First in-flight run of a newly overhauled engine.

At about 1240 Western Standard Time on 05 March 2005, an Avions Pierre Robin R-2160 aircraft, registered VH-OXY, crashed on a residential street, about 2 ½ NM west of Jandakot Airport, Western Australia.

The pilot reported that he was inbound to Jandakot when the engine suddenly lost power. The outboard portion of the right wing collided with a suburban power pole during the approach for the emergency landing and the aircraft rolled inverted and impacted the ground. The pilot, who was the sole aircraft occupant, sustained minor injuries and vacated without assistance. There was no spillage of fuel at the accident site and no post-impact fire. Personnel at the accident site inspected the aircraft’s fuel tank and observed that it did not contain any fuel.

The aircraft was on its first flight following maintenance, which had included the installation of an overhauled engine. During the flight the pilot completed the procedure for break-in of an overhauled engine. At the time of the accident, the aircraft had been airborne for 2 hours 41 minutes.

The circumstances of the engine failure were consistent with fuel exhaustion. Contributing to the fuel exhaustion were the higher than normal power settings, and therefore fuel consumption, associated with the conduct of the break-in flight.

The pilot was forced to land on a road when the useable fuel on board the aircraft had been consumed. The aircraft fuel quantity had been verified with an incorrect fuel dipstick that indicated unusable fuel as being useable fuel. The aircraft fuel gauges were capable of indicating fuel quantities that were consistent with the last fuel calibration card in the cockpit.

The incorrect markings on the dipstick accounted for a fuel discrepancy of 23 litres. The investigation could not determine the source of the remaining 20 litre fuel discrepancy.

The pilot had flown the Cessna 172 aircraft, registered VH-DBG, from Derby to Fitzroy Crossing earlier in the day. The pilot reported that, prior to departure from Derby, he had dipped the tanks using a dipstick, which displayed that there was 100 litres of fuel on board. After arrival at Fitzroy Crossing, the pilot added 44 litres of fuel to the aircraft. The pilot reported that he again used the dipstick to check the amount of fuel. He said that the dipstick displayed that there was 100 litres of fuel on board the aircraft.

The aircraft departed from Fitzroy Crossing and the pilot conducted a scenic flight on the return leg to Derby. As the aircraft was approaching Derby, cruising at 3000 ft, the engine began to splutter and then lost power. The pilot turned the aircraft towards a sealed road and, after transmitting a PAN call, conducted a forced landing onto a road. There were no reported injuries. The pilot reported that the flight time for the return flight was 1.8 hours. He also reported that he had leaned the mixture during the cruise portions of the flight in accordance with the engine manufacturer's operating manual. The ATSB did not attend the site, however the investigation was conducted with reference to information provided by the pilot in command, the operator and several other parties.

The pilot arranged for a licensed aircraft maintenance engineer to attend the aircraft on the road. The engineer reported that when he arrived at the aircraft and checked the fuel tanks, there was no useable fuel in either of the tanks. The pilot also reported that there was no useable fuel remaining in the fuel tanks. The engineer then checked the aircraft engine and fuel system and, after adding fuel, the aircraft was flown back to Derby with no reported problems.

Once the aircraft was back at Derby, further checks of the aircraft and its systems were conducted, with no reported defects found. The engineer reported that he added approximately 60 litres of fuel to each tank in 30 litre increments and found that the cockpit fuel gauges were showing quantities that were consistent with the fuel calibration card that was present in the cockpit.

A post occurrence flight plan of the proposed flight, in accordance with the company operations manual, revealed that the aircraft was required to carry 104 litres of fuel. With this amount of fuel onboard the aircraft, and a normal inflight fuel burn, there would have been 43 litres of fuel remaining in the aircraft at the point where the engine stopped.

The operator conducted an investigation into the circumstances of the occurrence. The operator's investigation found that the dipstick used by the pilot in command to check the fuel quantity incorrectly indicated unusable fuel as useable fuel. The amount of unusable fuel totalled 23 litres.

1. The pilot used an incorrect technique to dip the helicopter's fuel tank and consequently overestimated the fuel on-board.
2. The helicopter operator had not advised the pilot of the change in method for measuring the fuel quantity with the new wooden dip stick.
3. The pilot did not detect the discrepancy between the dip stick reading, the physical level of fuel contained in the tanks and the reading from the cockpit fuel gauge.
4. The helicopter fuel log contained ambiguous entries which the pilot used to resolve the discrepancy between the incorrect dip stick reading and the fuel quantity recorded on completion of the previous day's flying.
5. The helicopter was being flown with insufficient fuel to complete the flight.

The aircraft had been assessed as having 280 L of fuel on board prior to departure from Canberra, based upon the delivery pilot's calculation. ATSB calculations, using the operator's own fuel planning figures, indicated that the amount of fuel consumed during the 1.8 hour delivery flight from Tamworth would likely have equated to a fuel remaining figure of approximately 265 L. In addition, no allowance was able to be determined for the amount of fuel consumed during the engine ground runs at Tamworth, between the time of the last recorded refuel and the delivery flight. Accordingly, the actual fuel tank contents on departure from Tamworth for the delivery flight could not be accurately determined and would probably have been an amount less than the maximum useable.

While planning for the accident flight utilising a computer-based application, the pilot used an incorrect figure (465 L) with respect to total versus useable fuel tank contents (454 L). That led the pilot to include 11 L of fuel, which was unavailable for engine consumption. In addition, he omitted to plan an allowance for fuel consumption during the approximately 12-minute Sydney Harbour scenic flight. Using the operator's fuel consumption planning figure, this may have involved consumption of up to 20 L of additional fuel.

The pilot's use of the computer-based flight planning application included calculations for aircraft weight and balance. His utilisation of the full fuel planning figure in these calculations, instead of the assessed fuel load figure of 280 L, may have led to an erroneous perception that he would be overweight following embarkation of the five passengers at Bankstown, if he added fuel prior to take-off from either Bankstown or Canberra. Had the pilot used the assessed fuel tank content figure, he would have realised that he could have added fuel and remained within aircraft weight limitations.

The manufacturer's fuel usage figures are determined using a recommended technique for leaning of the fuel mixture supplied to the engines. During the accident flight, the pilot deviated from the recommended technique. That deviation would likely have increased the engine fuel consumption.

Technical investigation of the right engine indicated that it was capable of normal operation. Examination of the left engine indicated that it should still have supplied at least partial power in flight. The failure mode of the exhaust valve rocker stud and the bending of the inlet valve pushrod were examined in consultation with a representative of the engine manufacturer and engine overhaul specialists. Although an exact reason for the failure could not be determined, it is possible that the damage may have occurred following the loosening of one or both of the rocker pivot retaining nuts. As the nut(s) loosened during engine operation, the exhaust valve rocker would have lifted, preventing the exhaust valve from opening. During the valve overlap stage of the engine operating cycle, prior to the start of the induction stroke, the ignited and expanding combustion gasses may have been unable to escape through a now closed exhaust valve. That scenario would have greatly increased internal cylinder pressure which could have prevented the inlet valve opening and, consequently, resulted in the bending of the inlet valve push rod as it tried to move the valve. The damage to the inlet valve pushrod was also considered to have been consistent with the rotation of the engine with a "hydraulic lock" situation existing in the cylinder. Such a condition may occur in the cylinder if the engine was over primed prior to an engine start.

It is likely that the engine failures occurred as a result of fuel exhaustion.

1. The pilot planned the flight using a fuel consumption rate that was significantly less than the actual consumption.
2. There was no logging of fuel usage for the helicopter that would have alerted the pilot to the greater than planned consumption rates.
3. The pilot did not check the actual fuel consumption.

The circumstances leading to the loss of engine power were consistent with fuel exhaustion. The same consumption rate achieved on the flight from Bankstown to Moruya would have used all the helicopter's useable fuel in the elapsed flight time from Moruya to the accident site at Raymond Island.

The lack of any recorded fuel consumption checks meant that actual fuel consumption rates were not readily available to pilots flying the helicopter. This meant significant differences between planned and actual fuel consumption rates remained undetected. However, the quantity of fuel added at Moruya was greater than the planned fuel burn-off and should have alerted the pilot to the need for a check of the helicopter's actual fuel consumption. The remaining useable fuel at Moruya represented the minimum recommended allowance of 20 minutes fixed reserve. Any attempt to fly a greater distance under those conditions would have only been achieved by reducing the reserve fuel allowance.

The fuel consumption rate may have been masked by the reported anomalous fuel quantity indication. The reported 1/4 indication on the fuel gauge prior to the loss of engine power was just greater than the quantity that the pilot would have expected at his planned consumption rate. This may have reinforced his assessment of the actual fuel status and caused him to doubt the veracity of the low fuel warning.

Pilots of single-engine aircraft should always consider the possibility of an in-flight engine failure and its consequences. The engine failure occurred over water and at an altitude that did not permit an unpowered descent to a suitable land emergency landing site. This meant that the pilot was not in a position to conduct a forced landing without risk of damage to the helicopter and possible injury to its occupants. Evidence at the accident site suggested that contact with the tree canopy was not consistent with an autorotation landing that would have achieved minimum forward speed and rate of descent as recommended in the flight manual. Consequently, the attempted landing into the tree canopy did not achieve optimum conditions for survival.

Witnesses immediately initiated search and rescue action. However, had the helicopter not been seen just before descending into the trees, as might have been the case in more remote parts of the island, the consequences of not carrying an ELT may have been crucial to the survival of both the pilot and passenger.

History of the flight

The pilot and passenger were making a private flight in a Brantly two-place helicopter in accordance with the visual flight rules (VFR) from Bankstown to Lilydale with planned fuel stops at Moruya and Orbost. They departed Bankstown at 1100 ESuT and, following an uneventful flight to Moruya, refuelled the helicopter to full tanks at 1313. While on the ground at Moruya the pilot telephoned the fuel distributor at Orbost to confirm the availability of Avgas and was told that they did not hold any Avgas drum stock. The distributor suggested that he try Bairnsdale where Avgas was readily available. The pilot then elected to fly the extra distance to Bairnsdale after having determined that it was within the safe range of the helicopter and overfly Merimbula where fuel was readily available. At 1412 he departed Moruya with a planned endurance of 2 hours and 50 minutes.

The pilot monitored the progress of his flight by comparing the 10-minute time increments he had marked on his charts against an electronic timer attached to the instrument panel. The passenger reported that as they were approaching Bairnsdale she saw the low fuel warning light begin to flicker. The fuel gauge showed just above one quarter full. Shortly after, she saw the needle of the fuel gauge drop below the quarter full mark and the low fuel warning light stopped flickering and remained on. A few moments later the engine began to run roughly.

The pilot reported that soon after he saw the low fuel warning light illuminate, the engine lost power. He was flying at approximately 1,500 ft over water and turned toward Raymond Island, 7 NM east of Bairnsdale. He elected to land on the tree-covered shore rather than attempt to ditch the helicopter, which was not equipped with flotation gear or life jackets. He could not recall actioning any emergency drills.

At 1640 witnesses on Raymond Island reported seeing a helicopter approaching the southern shore of the island at low altitude with its engine running roughly and intermittently. As it passed low over bushland the engine was heard to cut out and the helicopter descended out of sight behind trees. A few seconds later witnesses heard the sound of two distinct impacts. They immediately commenced a search of the area and after 10 to 15 minutes located the wreckage of the helicopter in the undergrowth. The seriously injured occupants were administered first aid. Rescue and emergency personnel reported that there was no smell or evidence of fuel at the accident site and the injured passenger had told them the helicopter had run out of fuel.

Examination of the wreckage

The helicopter entered the tree canopy at moderate forward speed and travelled through the light timber and scrub for nearly 30 metres before contacting the ground, pitching forward and coming to rest inverted. Although damaged, one of the three main rotor blades was still attached to the rotor hub. The other two blades were shattered outboard of the secondary hinge and the fragments dispersed. Damage to the transmission and main rotor was consistent with no power being delivered to the rotor system. Examination of the wreckage and subsequent testing of components did not reveal any defect that would have contributed to the accident. The upper fuel cell was perforated during the accident sequence and the fuel plumbing damaged. The fuel system was drained and a small quantity of Avgas, approximately 50 mL, was found. The accuracy of the low fuel warning system could not be determined.

Pilot qualifications and experience

The pilot held a Special Pilot (Helicopter) Licence and a valid Class 1 medical certificate. The special licence validated his United States of America, Federal Aviation Administration (FAA) Commercial Helicopter Licence. He also held a United Kingdom Civil Aviation Authority Private Pilot's Licence (Helicopters). His total flying experience was 262 hours helicopter flight time of which 100 hours were on type. Prior to this flight, all but 10 hours of flight time on this type had been undertaken in the United Kingdom.

Fuel consumption and flight planning

A fuel gauge and engine instrumentation provided pilots with fuel flow information. Apart from this the only fuel consumption data provided to pilots was on a specification sheet published by the manufacturer of the helicopter. This listed a normal cruise fuel consumption of between 38 and 42 Litres per hour (LPH) at a power setting of 75 percent. The engine manufacturer's charts gave fuel consumption rates for the equivalent power from a lean limit of 43 LPH up to a "suggested high limit" of 52 LPH. The reason for the apparent difference in quoted fuel consumption rates was not able to be determined. The fuel consumption rate for the flight from Bankstown to Moruya was calculated to have been between 46 and 47 LPH. This was based on the flight time of 2 hours and 13 minutes. An accurate average fuel consumption rate for the helicopter was not possible because flying times and fuel records were incomplete. Only one pilot had established a consumption rate, reported to have been 48 LPH. Other pilots reported they had conservatively flown the helicopter for periods less than two hours and although they were unsure of actual consumption rates they thought that it was greater than 40 LPH.

The pilot had planned this flight using a fuel consumption rate of 40 LPH, a figure he had used for all his previous flying on the type. The flight from Bankstown to Moruya was the first extended flight he had undertaken in Australia. He had not checked the fuel consumption after refuelling at Moruya and used the same flight planned fuel consumption rate in his fuel calculations for the flight to Bairnsdale.

The helicopter was fitted with a manually operated vernier mixture control. The fuel flow gauge was graduated in US gallons per hour with a corresponding non-linear outer scale for the manifold air pressure (MAP) setting. The pilot reported that he had used a MAP setting of 21 inches of mercury and had adjusted the mixture in accordance with the flight manual procedure. The corresponding fuel flow indication for this power setting equated to 41.7 LPH. In contrast the estimated consumption rate of 47 LPH was equivalent to a MAP setting of 22.5 inches of mercury.

Fuel quantity indications and warnings

The helicopter had an electrically powered fuel gauge with graduations for each quarter of tank capacity. The calibration card showed that the 1/4 capacity graduation corresponded to a quantity of 29 L. Other pilots who had flown the helicopter reported that the gauge readings appeared to be inconsistent with fuel usage and that at lower fuel quantities they thought the gauge over-read.

A warning light provided the pilot with a low fuel quantity warning. The system was pneumatically operated and was independent of the fuel quantity indication system. The low fuel quantity warning light was designed to flash as the fuel level approached the 10 minute reserve. The length of flash became progressively longer until finally a steady red light appeared when approximately 5 minutes of flight time remained. The aircraft Flight Manual stated that flight should not be attempted beyond the first indication of the low fuel warning light. A few pilots reported that on occasions the low fuel warning light had illuminated intermittently during manoeuvring and in turbulence with low fuel quantities.

Autorotation technique

Autorotation facilitates a controlled descent and landing when engine power to the rotor system is removed, such as when an engine fails. The technique normally requires the helicopter to be flared toward the end of the approach in order to arrest its forward speed and use the energy stored in the rotor system to reduce the vertical speed and cushion the helicopter's touchdown. The flight manual recommended a speed of 48 kts for a power-off approach. It also stated that in the event of an engine failure over rough terrain "Increase angle of flare to reduce airspeed to near zero ground speed and allow helicopter to settle vertically".

Search and rescue

The pilot had not lodged flight details or nominated a Sartime, but had arranged for an operator at Bankstown to provide a SARWATCH. Although the pilot had nominated carriage of an Emergency Locator Transmitter (ELT) on his flight plan the aircraft was not equipped with one, nor had he carried a portable unit. Civil Aviation Regulation (CAR) 252A required the carriage of an ELT for this flight. The pilot later reported that he thought the aircraft had an ELT installed. An entry on the Maintenance Release stated "Carriage of ELT in accordance with CAR 252A - As Required".

1. The pilot used incorrect fuel planning data.
2. The pilot did not fully understand the effects on fuel consumption of altitude and engine power settings.
3. The engine failed because of fuel exhaustion.