What happened
On May 27, 2019, a Cessna 152, registration OK-KAL, was performing a planned flight from Letňany (LKLT) to Plasy (LKPS) via Mníšek pod Brdy. During the takeoff roll from runway 23L, the aircraft accelerated to approximately 60–65 knots before the pilot noticed an irregular engine rhythm and a failure to accelerate further despite full throttle.
Unable to maintain altitude and with insufficient runway remaining to return to the aerodrome, the pilot performed an emergency landing in a nearby field containing tall rapeseed crops, approximately 1.3 meters in height. As the aircraft's nose gear contacted the dense vegetation, the sudden deceleration caused the aircraft to flip onto its back. The pilot sustained one minor injury during the impact with the instrument panel.
The investigation
The ÚZPLN examined the aircraft's technical condition, fuel and oil samples, and the pilot's pre-flight actions. Laboratory analysis confirmed that the fuel (AVGAS 100LL) and oil met all required specifications and were free of contaminants. The engine, electrical systems, and fuel lines were found to be in good working order.
Investigators focused on the fuel selector valve, which lacks fixed end positions and relies on friction to remain in place. Through ground testing, investigators were able to replicate the engine's irregular behavior by partially restricting fuel flow, simulating a partially closed valve.
Findings
- The engine power loss was caused by an insufficient supply of fuel to the engine.
- This restriction was likely due to the fuel selector valve being left in a partially closed position.
- The valve's position was likely not fully secured during the pilot's pre-flight checks.
- The high density of the rapeseed crop was the direct cause of the aircraft flipping during the landing.
- The pilot's decision to perform the emergency landing was appropriate given the low altitude and proximity to urban areas.