What happened
On 19 September 2009, an Auster J5F Aiglet Trainer, registration G-AMZU, was performing a private takeoff from Bicester Airfield in Oxfordshire. The pilot, intending to avoid glider activity at the southern end of the airfield, commenced the takeoff run approximately 150 to 200 metres from the start of the 1,000-metre runway.
During the takeoff roll, the aircraft experienced slow acceleration. Once airborne, the aircraft climbed poorly and began a gentle right turn. As the aircraft approached a line of trees, it appeared to stall at a very low altitude. The left wing dropped and the nose pitched down, causing the aircraft to strike the trees and come to rest approximately 380 metres beyond the runway end. The impact caused significant damage to the landing gear, propeller, right wing, and left wing. The pilot sustained serious injuries, while the passenger suffered minor injuries.
The investigation
The AAIB investigation examined the aircraft's performance, the environmental conditions, and witness accounts. Witnesses observed the aircraft's takeoff behavior, with one noting a sudden pitch upward and another observing a nose-down attitude that might have increased tyre friction and hindered acceleration.
Investigators also reviewed the weather data, which indicated a temperature of 25°C and a dew point of 13°C. The investigation looked into the possibility of incorrect elevator trim or flap settings, though it could not be definitively determined if the pilot had altered these settings during the flight. There was also an assessment of whether the aircraft's takeoff position and the prevailing atmospheric conditions influenced the climb gradient.
Findings
- The takeoff run began much further down the runway than usual, leaving less distance for acceleration.
- A high density altitude likely degraded the aircraft's climb performance.
- The aircraft likely stalled at a low altitude, making recovery impossible.
- A slight tailwind during the early part of the takeoff run may have contributed to a longer ground roll.