What happened
On 19 July 2007, a Piper PA-28-181 Cherokee Archer III, registration G-LKTB, was conducting a private flight from Manchester International Airport to Halfpenny Green. Approximately 30 to 35 minutes into the flight, the aircraft's GPS and radio displays began to flicker and eventually failed. Simultaneously, the engine power became unresponsive and the engine began running roughly.
After notifying Shawbury Radar of the situation, the pilot lost radio contact, though subsequent calls were answered by London Information. Believing the aircraft was suffering from both engine and electrical faults, the pilot initiated a precautionary landing at Otherton Airfield. During the approach to Runway 25, the engine again showed poor acceleration. Although the pilot touched down at the threshold, the downhill gradient of the runway prevented the aircraft from stopping within the paved surface. The aircraft travelled approximately 20 to 30 feet into a recently ploughed field, resulting in a nosewheel collapse.
The investigation
The AAIB examined the aircraft's electrical and engine systems. Following repairs, maintenance testing of the engine, electrical generation, and warning systems showed all components were performing correctly. The investigation focused on why the electrical displays failed and why the engine responded poorly to throttle inputs.
Findings
- The loss of electrical power was likely caused by the alternator being left in the OFF position during pre-flight checks, leaving the electrical equipment to run solely on battery power. This would lead to a total failure of the equipment after approximately 30 minutes of use.
- The engine's poor response to the throttle was likely due to the carburettor heat being set to the HOT position, which enriches the fuel/air mixture. This effect was likely worsened by the pilot rapidly advancing the throttle during a stall recovery maneuver, which can cause the engine to run roughly and accelerate slowly.