What happened
On 14 June 2009, a pilot was conducting a local private flight in an Acrosport 2, registration G-NEGG, near Bidford Airfield in Warwickshire. Following standard pre-flight and engine checks, the pilot commenced a takeoff from the grass runway. During the initial climb, the pilot noticed the aircraft was not climbing at its expected rate. In an attempt to rectify the issue, the pilot applied full throttle and raised the tail, but the engine power continued to diminish.
Realising that completing a standard circuit was impossible, the pilot attempted to climb straight ahead to maintain altitude. As the power continued to drop, the pilot was forced to descend and search for a suitable landing site. The pilot selected a field of barley approximately 1 metre high. The landing was difficult due to the low altitude, a steep glide angle, and limited visibility over the aircraft nose. The aircraft struck the crop at a low speed, causing the main landing gear to detach. The pilot sustained a serious head injury when striking the windscreen during the abrupt deceleration.
The investigation
Investigators reviewed the pilot's account and examined video footage of the takeoff. The footage confirmed that the engine note gradually decreased during the climb. Notably, the pilot was wearing a new active noise-reduction headset, which may have masked the audible signs of the power loss that would have been more apparent with conventional equipment.
An examination of the aircraft revealed no evidence of damage prior to the impact. However, investigators found that the spark plugs connected to the left magneto were heavily fouled with soot. The owner planned to inspect the magneto and engine during a future overhaul.
Findings
- The engine failed to develop full RPM during the takeoff roll and climb.
- The use of an unfamiliar active noise-reduction headset likely prevented the pilot from detecting the changing engine note earlier.
- The sooty condition of the left magneto spark plugs was identified as a significant finding during the technical examination.