What happened
On 23 August 2021, a Piper PA1s registered F-HLOG, operated by a local flying club, was conducting a local flight near the Lille - Marcq-en-Barœul aerodrome. After completing a touch-and-go maneuver on runway 35, the pilot began a left turn on the crosswind leg, announcing an intention to perform a "short circuit" flight.
During the initial climb, witnesses observed smoke emanating from the underside of the aircraft. As the aircraft progressed, witnesses noted a significant reduction in engine speed. While attempting the turn, the pilot lost control of the aircraft, which subsequently struck the ground and caught fire. The impact and subsequent fire resulted in two fatalities and the total destruction of the aircraft.
The investigation
The investigation focused on the mechanical state of the Continental C90-8F engine and the flight dynamics during the emergency. Investigators examined the wreckage and the engine components in a laboratory setting. The engine had recently undergone a general overhaul approximately 100 operating hours prior to the accident.
Technical analysis of the engine revealed a rupture in the left half-crankcase near a crankshaft bearing. Laboratory testing determined that this rupture was the result of a progressive fatigue-cracking process that had developed internally. Because the cracks had not yet reached the exterior surface of the crankcase, they remained undetectable during previous maintenance inspections.