News: Aircraft performance

The ATSB’s investigation into the fatal accident of an Air Tractor AT-502 revealed several factors that contributed to the tragedy, and the measures that aerial application pilots and operators need to be taking.

Accident site of Air Tractor AT-502, VH-LIK, 50 km east of Walgett, NSW.

The accident occurred on 5 November 2016 at an airstrip at Cryon, NSW. The aircraft was conducting aerial application operations. After commencing the take-off, the aircraft failed to gain any significant altitude, and clipped the top of a fence about 1,300 m beyond the start of the runway. After climbing about 20 feet above the ground, the aircraft descended, and collided with trees and the ground before coming to rest inverted. The pilot was fatally injured and the aircraft was destroyed by impact forces and a fuel-fed fire.

The ATSB investigation found that the flaps were either never extended or were retracted at some point during the take-off. The reason for the retraction could not be determined, but it significantly degraded the take-off and climb performance. This effect was compounded by the estimated weight of the aircraft, the local temperature and the wind conditions.

The aircraft reached a height above the ground where the reduced benefit of ground effect further degraded the aircraft’s performance. The low height and airspeed precluded the pilot from turning the aircraft towards a clear area, and so the aircraft descended into the trees.

... the aircraft manufacturer is updating the maintenance section of the aircraft owner’s manual to specify that the gatebox and emergency dump controls are to be inspected periodically for condition, function and adjustment.

Recorded data from the aircraft indicated that the pilot had attempted to dump the hopper contents after becoming airborne – a move which would have achieved significant gains in climb performance. However, for unknown reasons, a complete dump was not achieved.

The performance benefits of quickly and significantly reducing an aircraft’s weight means that a proper functioning  emergency jettison system to dump the contents of a hopper is vital. Pilots rely on the system in case performance is inadequate, particularly when taking off with a heavy load. Registered operators should ensure adequate ongoing maintenance and regular checks to maintain serviceability of the system.

As a result of the accident, the aircraft manufacturer is updating the maintenance section of the aircraft owner’s manual to specify that the gatebox and emergency dump controls are to be inspected periodically for condition, function and adjustment.

This accident also serves as an important reminder for pilots to monitor weather conditions like temperature and wind and to anticipate the potential adverse effects of local conditions on aircraft performance.

Read the final report, AO-2016-146: Collision with terrain involving Air Tractor AT-502, VH-LIK, 50 km east of Walgett Airport, NSW, on 5 November 2016.

 

Last update 20 November 2018