What happened
On 29 August 1999, a DHC-1 Chipmunk 22, registration G-BDCC, was performing a private aerotow flight at Husbands Bosworth Airfield in Leicestershire. The flight proceeded normally during the initial climb until approximately 500 feet, at which point the pilot retracted the flaps and deactivated the fuel boost pump. As the aircraft climbed through 800 feet, the engine speed began to fluctuate significantly. To ensure safety, the pilot signaled the glider pilot to release the tow rope.
Following the release, the pilot reactivated the fuel boost pump and performed standard engine failure procedures. While attempting to turn back toward the airfield, the engine lost power. Although the pilot managed to find intermittent power by adjusting the throttle, the engine could not maintain altitude. The pilot attempted a landing on a downslope, downwind approach toward the western part of the airfield. Due to the challenging wind and terrain conditions, the aircraft could not clear the northern boundary fence, forcing the pilot to pull up and attempt a landing in a nearby field.
During the forced landing, the right main landing gear struck a solid object. The aircraft subsequently crossed a cutting containing a quarry conveyor belt system before coming to a stop. The pilot sustained serious injuries. Following the impact, the pilot successfully shut off the fuel and electrical systems to mitigate fire risks before being rescued by airfield personnel.
The investigation
Investigators examined the aircraft at the accident site and later dismantled it for further inspection. An examination of the fuel system, including fuel lines and filters, showed no obstructions, and the tanks contained the correct fuel type in sufficient quantities. The engine air intake was also found to be clear.
Detailed testing of the carburettor by an approved overhaul organisation revealed no faults. Furthermore, a ground run of the engine, conducted with the fuselage secured on trestles, showed satisfactory operation with normal gauge readings and acceptable magneto checks. The investigation also noted that the aircraft had undergone repairs following a separate incident in June 1999, but had flown successfully for 50 hours prior to this event.
Findings
- The engine power loss occurred during a turn following the release of a glider.
- The aircraft was unable to land on the intended strip due to the combination of a tailwind and the downslope nature of the landing area.
- A temporary restriction of fuel flow to the engine likely occurred during the climb, which the re-engagement of the boost pump failed to rectify.