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The pilot of the Chipmunk did not see the Metroliner. It is likely that the pilot commenced his take-off roll when the Metroliner was at least 3 NM from touchdown. At that distance, the Metroliner may not have been readily detectable by the Chipmunk pilot. His lookout for possible traffic would most likely have been directed towards the circuit and approach of runway 03 rather than towards runway 21 and he would not have been expecting to see traffic approaching from the opposite direction. With the aircraft in the level attitude during takeoff, he would have been looking along the runway and his attention would have been focused on maintaining directional control. The Metroliner would most likely have been obscured from the Chipmunk pilot's view by the nose of his aircraft when he subsequently rotated to the climb attitude.

The crew of the Metroliner did not see the Chipmunk until that aircraft was almost overhead theirs. As they had not received any response to their broadcasts on the CTAF, they were relying on visual acquisition of any unalerted traffic as their only defence against a conflict. However, the Chipmunk was a small visual target with little relative movement. In addition, it had no anti-collision lighting and would initially have been below the Metroliner crew's horizon. The contrast between the background and the colour of the Chipmunk was minimal and would have made the aircraft difficult to discern.

The straight-in approach procedure at CTAF aerodromes did not appear to adequately address the limitations of unalerted "see and avoid" principles. The assumption of two pairs of eyes being more likely to detect unalerted aircraft than one pair of eyes, did not prove to be an adequate defence in this incident.

In this instance, the crew of the Metroliner elected to make a straight-in approach in wind conditions that most probably favoured a reciprocal runway direction. Without any response to their broadcast intentions, the crew probably assumed that there was no traffic and believed it was safe to use runway 21. As regulations in force at the time of the occurrence did not include a requirement for an airline operator to assess the circumstances and the likelihood of encountering non-radio traffic at individual locations, it was likely that many crews were conducting straight-in approaches as an expected routine. Had the crew been aware, for example, of the potential for greater numbers of recreational movements at weekends and on public holidays, they may have decided not to conduct the straight-in approach.

Although the company had provided a radiocommunication service to comply with the requirements for this procedure, its effectiveness to alert the crew to other aircraft was restricted by company procedures and by the physical location of the radio operator. The radio operator was not familiar with aircraft movements and had never been instructed to provide runway-in-use information. Had the radio operator been afforded a full view of the entire runway and the approach path of the Metroliner and permitted to issue traffic information, a timely warning may have been broadcast to the crew of the Metroliner about the presence of the Chipmunk.

The pilot of the Chipmunk chose to continue his flight without radio communication and without knowledge of a procedure that could place him in potential conflict with a passenger-carrying aircraft. Knowledge of scheduled aircraft movements at that location may have influenced the pilot to avoid commencing a non-radio flight when the arrival of a scheduled service was imminent.

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