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Analysis

Summary

The impact damage to the right fuel cell bladder and extended periods of ground running during the day's operations prevented the investigation from determining an accurate fuel consumption. The investigation determined that a landing on sloping ground should have affected both the fuel quantity indicator and fuel low level advisory light equally. An indicated fuel quantity of 100 lbs (86.9 lbs useable) and coincident illumination of the fuel low level advisory light, both reported by the pilot, could not be explained.

Technical examination of the helicopter's fuel indicating system established that illumination of the fuel low level advisory light coincided with 35 lbs (21.9 lbs useable) indicated on the fuel quantity indicator. At the company flight planning fuel consumption rate of 176 lbs per hour, 21.9 lbs of useable fuel would likely have equated to a flight time of approximately 7 minutes. In that case, a reported departure from Lake Nameless Hut at 1515 hours would have likely resulted in engine fuel starvation at about 1522 hours.

Technical examination of the helicopter and engine revealed no anomalies. Therefore, the helicopter was considered capable of normal flight prior to the occurrence. The amount of fuel onboard the helicopter, less than that expected by the pilot, likely resulted in unporting of the fuel cell fuel supply hose, and engine fuel starvation during the turn to land at Tom Whitely's Hut. Due to impact rupture damage of the right main fuel cell, an accurate fuel quantity remaining could not be measured.

The pilot reported that the autorotation landing was normal and that contact with a wire rotated the aircraft through 180 degrees. As there was no evidence of helicopter contact with the fence prior to, or during the initial ground impact, the investigation concluded that the fence did not contribute to the accident sequence.

Ground impact marks indicated a relatively steep approach with low forward ground speed. Examination of the Height Velocity Diagram indicated that, at the pilot reported height of 200 ft above ground level, and airspeed in autorotation of 65 kts, a successful autorotation landing should have been possible. Impact damage indicated that the autorotation landing was unsuccessful. It was therefore likely that the pilot's estimate of height and airspeed at the time the rotor speed decreased was less than actual. In that case, the helicopter may have been at a height and airspeed from which a successful autorotation landing would be difficult to perform.

The pilot reported that he had minimal recent experience on the Hughes 369E helicopter type and had practised autorotation landings in an Augusta 119 Koala helicopter type during the previous week. While it cannot be discounted, the investigation could find no evidence to indicate that lack of type-specific recency, or contradicting cross-type pilot handling, contributed to the unsuccessful autorotation landing.

While the pilot reported asking the passengers to confirm the security of their seat belts prior to take off for the occurrence flight, the passengers reported that headsets were not worn during that flight. The ambient cockpit and other noise as the passengers boarded the engine-running helicopter may have prevented them from hearing any direction from the pilot. The front seat passengers were ejected forward of the helicopter during the impact sequence. The front seat passengers' seat belts, shoulder harnesses and attachment points exhibited no evidence of damage, or having been forced by impact forces. Therefore, it was unlikely that the front seat passengers were wearing seat belts at the time of impact.

In effect, the selection process employed to contract the operator for the day's operation included an informal risk assessment. Risk assessments represent a valuable safety tool. They can range from an informal experiential and environmental audit, similar to that conducted by the coordinator of the Western Tiers operation, to an in-depth analysis of all hazards likely to affect the operation of an aviation system. That analysis includes consideration of the likelihood of an identified hazard to an operation, and the possible consequence to the aviation system resulting from that hazard occurring.

A more formal and inclusive risk assessment, conducted by all participants in the Western Tiers operation, could have enhanced the overall safety of that operation. Some of the risks to the operation, and possible risk treatments that might have been considered by the interacting participants in the operation were:

Pilot experience. The pilot's reported unfamiliarity with the area of operations and lack of recency in the Hughes 369E helicopter type could have been mitigated by a more extensive orientation and check flight and briefing procedure. That process could also have included appraising the coordinator of the operation of the pilot's background and lack of local experience.

Fuel reserve. The 10-minute fixed reserve authorised for external load operations in the company Operations Manual likely maximised flexibility and payload during such operations. However, the operation in the Western Tiers involved the movement of external loads and carriage of passengers in an at times inhospitable area, by a pilot unfamiliar with that area. In that case, modifiers to the company 10-minute fixed reserve may have been pertinent, and the company charter minimum fuel requirements been more relevant to the operation.

Flight following. The operation was conducted in an at times inhospitable and remote area of north-western Tasmania. There was scope for a more formal flight following procedure to decrease rescue agency response time and optimise the safety of the operation overall. Available flight following options included formal employment of a monitored flight and details schedule by the participants in the Western Tiers operation, regular radio contact between the pilot and Air Traffic Services, or the nomination of a SARTIME by the pilot.

The departure of the rescue helicopter from the accident site, without landing, was reported by the survivors to have adversely affected their morale, and confidence in their subsequent rescue. They were not aware that the ground rescue party was enroute to their location. A means of communication from the rescue helicopter to personnel on the ground may have prevented that decline in survivor morale and confidence.

 
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