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 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".
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.
- The pilot planned the flight using a fuel consumption rate that was significantly less than the actual consumption.
- There was no logging of fuel usage for the helicopter that would have alerted the pilot to the greater than planned consumption rates.
- The pilot did not check the actual fuel consumption.
Local safety action
As a result of investigations into the circumstances of this accident the Bureau expressed concern to the helicopter manufacturer about aspects of the text in the Flight Manual relating to the Low Fuel Warning Indicator. These were:
- references to the remaining flight time from when the warning light first illuminates. The test of this system only determined a remaining fuel quantity. The remaining endurance was predicated on a fuel consumption that may differ from actual fuel consumption rates.
- the wording of the CAUTION could be misinterpreted and it should be made clear that flight is discontinued as soon as possible after the low fuel indicator lamp illuminates, and
- the importance attached to this information was better emphasised by a WARNING annotation, rather than a CAUTION.
Correspondence from the helicopter manufacturer, dated 18 October 2000, stated that they intend to incorporate these changes with an upgraded and reformatted Flight Manual within the next 12 months.
|Date:||02 March 2000||Investigation status:||Completed|
|Time:||1640 hours ESuT|
|State:||Victoria||Occurrence type:||Fuel exhaustion|
|Release date:||15 November 2000||Occurrence class:||Operational|
|Report status:||Final||Occurrence category:||Accident|
|Highest injury level:||Serious|
|Aircraft manufacturer||Brantly International Inc|
|Type of operation||Private|
|Damage to aircraft||Destroyed|
|Departure point||Moruya, NSW|
|Departure time||1412 hours ESuT|
|Role||Class of licence||Hours on type||Hours total|