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Analysis

Summary

The accident

The investigation disclosed that although there was a minor anomaly in one magneto, the engine was capable of delivering full power. Accordingly, it is likely that the aircraft was flown off the strip with full power available and applied, although it cannot be discounted that there may have been a minor power reduction at some stage due to the loose blade terminal in one magneto. However, the power loss was almost certainly perceived rather than actual, such perception being created by the aircraft sinking after the flaps were raised at an airspeed lower than specified. The pilot did not confirm a power loss from engine instrument indications.

The pilot's natural tendency would be to maintain the nose up climb attitude or raise the nose to try to maintain a climb. This would have caused the speed to further reduce as was evidenced by the pilot reporting that the airspeed dropped to 60 knots. When this occurred the pilot lowered the nose to maintain airspeed and controlled the flight path to avoid obstacles.The aircraft continued to descend to a point where he had to reduce power and flare the aircraft for the inevitable forced landing. The aircraft landed heavily, most probably in a stalled condition.

Human factors

This accident therefore had very little to do with the pilots ability to physically handle the aircraft. It instead involves a corporate culture that allowed poor aircraft and crew selection, inadequate flight preparation, incorrect briefing, and real or perceived peer pressures on the pilot, to combine to place the pilot into a situation from where an accident was essentially inevitable. In other words, a human factors accident.

Human factors is about people in their living and working situations; about their relationships with machines, with procedures, and with the environment about them; and also about their relationships with other people. (ICAO Circular 216-AN/131).

In applying certain techniques to the investigations of the human factors involved in aircraft accidents, BASI uses the Reason accident causation model, and, in the report into the 1993 Piper Chieftain accident in Young NSW(BASI Investigation Report 9302743), defined the common elements in an organisational accident as:

  • latent failures which arise from deficiencies in managerial policies and actions within one or more organisations. Often these organisational factors are not immediately apparent and may lie dormant for a considerable time.
  • local factors, being conditions which can affect the active failures. These include such things as task and environmental conditions.
  • active failures, being errors or violations which have an immediate adverse effect. These unsafe acts are typically associated with operational personnel.
  • inadequate or absent defences which fail to identify and protect against technical and human failings arising from the three previous elements.

Latent failures

Latent failures can be weaknesses or inadequacies within the management of organisations which are not immediately apparent. They can remain dormant for extended periods. These organisational factors can impact upon the workplace to create an environment or a corporate culture which increases the probability of errors or violations, and weakens the systems defences which are designed to minimise the consequences of unsafe acts. These latent failures become apparent when they combine with local triggering events and circumstances such as active failures, resulting in a breakdown of the system.

In relation to this accident the organisational failures included:

  • inadequate management by the chief flying instructor who:
    • scheduled an operating pilot with low total and no recent experience on the type,
    • did not conduct a comprehensive briefing both prior to the exercise and prior to the take off on the accident flight.
    • gave a briefing prior to the accident flight that did not reflect the manufacturers requirements.
  • On a broader scale:
    • the company did not provide adequate management of its human resources.
    • the selection procedures for determining who should operate which flight were inadequate.

Active failures

Active failures are unsafe acts which most generally involve the actions of operational personnel. Such failures can be divided into two distinct groups; errors and violations. Errors may be of two basic kinds and involve attentional slips or memory lapses, and mistakes. Violations may be deliberate deviations from a regulated practice or prescribed procedure.

The significant unsafe act in this occurrence was that the pilot made a mistake by raising the flaps at too low an airspeed.

Local factors

These include such things as task and environmental conditions. A significant local factors in this accident was that the chief flying instructor was part of the ownership and management of the company. Accordingly the authority gradient between the chief flying instructor and pilot was very steep and the pilot would be unlikely to doubt the judgement of a respected peer who had been instrumental in his training and employment. Other local factors were:

  • the chief flying instructor did not adequately assess the knowledge and skills of the pilot relative to this particular operation
  • the pilot was neither experienced nor current on type.
  • the pilot did not use the proper procedure to account for the weight of his passengers.
  • the pilot did not mentally prepare himself for this flight
  • the aircraft used for the operation was inappropriate for the task in that the strip at Taggerty was too short for the combination of aircraft type, its load, and the takeoff procedures being employed.

The inadequate or absent defences included:

  • the company's requirements for pilot currency on type were inadequate
  • the pilot's training did not prepare him for this set of circumstances
  • the assessment of the pilot's skills during licence renewals and endorsements were inadequate
  • the company did not ensure its pilots were complying with the statutory requirements for weight calculation.

CONCLUSIONS

Findings
  1. The aircraft had one minor anomaly in one magneto but was otherwise serviceable for the flight.
  2. The company selected an inappropriate aircraft and an inadequately prepared pilot to undertake the task.
  3. The pilot was neither experienced nor current on the type.
  4. The pilot used an incorrect procedure for calculating the weight and the performance of the aircraft.
  5. The briefings given to the pilot by the chief flying instructor were inadequate.
  6. Because of the steep authority gradient the pilot was unlikely to doubt the decisions of the company and the chief flying instructor.
 
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