What happened
On 25 May 2020, a Pioneer 300, registration G-CGTL, was conducting a post-maintenance check flight near Abergavenny Airfield. The aircraft had recently undergone significant maintenance and reassembly under the supervision of a Light Aircraft Association (LAA) inspector.
During the climb to 600 ft, the pilot received an electrical power warning via the headset. Shortly after, while performing a turn to return to the airfield, the engine began to vibrate violently before losing power and stopping. The pilot attempted to restart the engine, but it failed to maintain thrust.
In an attempt to prepare for landing, the pilot selected the landing gear to the down position. However, the gear failed to extend, and the landing gear circuit breaker tripped repeatedly upon attempts to reset it. With insufficient time to perform a manual extension, the pilot executed a wheels-up forced landing in a field approximately 1.6 miles from the airfield. The pilot was uninjured, though the aircraft sustained damage to the propeller and lower fuselage.
The investigation
The investigation examined the aircraft's recent maintenance history, the use of Mogas fuel, and the mechanical state of the landing gear system. While the AAIB did not examine the aircraft directly, an examination by the LAA Engineering department revealed that the nose landing gear did not retract fully into its housing.
Investigators also looked into the potential for fuel system issues. The aircraft was using Mogas, which is more prone to vapour lock than Avgas. The investigation considered whether heat-soaking from the sun and an extended ground run had caused fuel to vaporize. Additionally, the investigation reviewed the electrical system, noting that the pilot had previously experienced similar electrical warnings on this aircraft, which were reportedly resolved by operating the landing gear.
Findings
- The loss of engine power may have been caused by vapour lock in the fuel system, potentially triggered by the use of Mogas in warm conditions following a period of heat-soaking.
- The failure of the landing gear to extend may have been caused by an electrical current issue or improper adjustment of the landing gear microswitches, which could cause the circuit breaker to trip to protect the system.
- The pilot's focus on the electrical warning may have contributed to the aircraft climbing away from the airfield, reducing the available gliding distance for a return to the runway.