Collision with terrain followed perceived partial power loss

Wreckage of VH-YPQ, which was partially disturbed during rescue of the occupants

A Diamond DA40 NG light aircraft’s loss of control and collision with terrain just south of Port Macquarie Airport highlights the need to maintain aircraft control in the event of an emergency or abnormal situation, an ATSB investigation notes.

On the evening of 8 September 2017, an instructor and student were preparing to conduct the student’s first series of night circuits, with the instructor at the controls for the first take-off. At about 200 feet above the runway, the instructor observed propeller speed and engine power fluctuations that continued to increase as the aircraft climbed to 400 feet.

Recorded data would show that the engine was producing full power, however, the instructor interpreted the noise and vibrations brought on by the propeller fluctuations as a partial engine power loss and commenced a left turn, aiming to return and land on the runway in the opposite direction to the take-off.

The instructor had considered landing straight ahead but assessed that there was power available to turn and that they would be unable to see and avoid trees or to be sure to land in a suitable clearing ahead.

In the 10 seconds that the instructor was assessing and making decisions about a perceived partial power loss, the airspeed reduced from 75 to 69 knots due to the aircraft’s nose-up attitude. Then, at the same time as commencing the turn back towards the runway, the instructor reduced engine power to 30 per cent, while maintaining a nose-up attitude, and airspeed reduced rapidly.

During the turn, the aircraft stalled, resulting in a loss of control. Although the aircraft pitched down and the instructor subsequently increased power, control was not regained. The aircraft descended and collided with trees, coming to rest inverted.

The student and instructor were seriously injured, and the aircraft was destroyed.

The ATSB’s investigation into this accident found after reducing power, the instructor did not maintain adequate airspeed during the turn. This resulted in the aerodynamic stall and loss of control.

The aircraft manufacturer, Diamond Aircraft Industries, could not determine the reason for the fluctuations. Propeller speed fluctuations had occurred in other DA40 NG aircraft, and either resolved without pilot input or by moving the power lever.

“This investigation highlights three initial actions that pilots should consider to maintain aircraft control in the event of an emergency or abnormal situation, such as in this accident, which was a perceived partial power loss after take-off,” said ATSB Director Transport Safety Dr Stuart Godley.

“Firstly, lower the nose to maintain the glide speed of the aircraft, and if turning, pilots need to keep in mind an increased bank angle will increase the stall speed.

“Secondly, maintain glide speed and assess whether the aircraft is maintaining, gaining or losing height to gauge current aircraft performance.

“Finally, fly the aircraft to make a landing, given the aircraft’s height and performance, and the pre-planned routes for the scenario.”

You can find here the investigation report AO-2017-090: Loss of control and collision with terrain involving Diamond DA40, VH-YPQ, 1 km south of Port Macquarie Airport, NSW, on 8 September 2017

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