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Analysis

Summary

The aircraft

A detailed examination of all available parts of the helicopter concluded that the engine was most likely to have been operating and driving the main and tail rotors. Consideration was given to failures that could cause an uncommanded descent or turn in flight. However, the investigation considered it unlikely that an experienced pilot would allow the helicopter to smoothly descend to collision with the ground.

No evidence was found of any pre-existing defect or malfunction to the aircraft that may have contributed to the development of the accident.

The flight path

Under the prevailing conditions, the investigation considered that the track flown by the helicopter was in keeping with the pilot's normal routine. The unusual aspect of the flight path was its inappropriately timed descent.

The helicopter was reported to be in a smooth flight path, with no jerking and no abnormal sounds such as would be produced with an engine power change or sudden control inputs. On impact with the trees, the helicopter was in a steady flight regime, laterally-level and descending at about 1,200 ft/min. This could indicate that the pilot was maintaining his grip on the cyclic control. If the cyclic control was released, it would most likely have fallen to some abnormal position in a short time. This could have caused the helicopter to adopt an unusual attitude very quickly. The conclusion, therefore, is that the pilot may have been able to maintain control in some form or other: from fully conscious, to a situation where he had managed to "freeze" on the controls and simply maintain them in position.

If the pilot was fully conscious, then the flight path may have resulted from a distraction. However, no evidence was found of anyone making a phone call to the aircraft around the time of the accident. In any case, it is unlikely that an experienced pilot flying at low altitude toward rising terrain would allow himself to become distracted for the time involved in this accident sequence (about 15 secs) and not pay any attention to the flight path.

The pilot

The pilot had visited a DAME a few weeks prior to this accident. This was as a result of headaches that had increased in severity and involved vision disturbances. The ENT specialist found a suspected sinus infection and prescribed a course of antibiotics. The investigation found no underlying personal factors, other than the headache problem, that may have played a role in this accident sequence.

There is no evidence that the pilot complied with the relevant regulations, other than his initial referral of the problem to a DAME. CAR 6.16A imposed a condition on the pilot that he not resume flying duties until being cleared to do so. It is likely that the pilot was reluctant to cease his normal duties unless strongly advised. The DAME had not yet reported the pilot's medical situation to CASA. Consequently, CASA were not in a position to take more positive control of the case.

 
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