What happened
On July 5, 2014, a Piper PA-31P Navajo, registration N11WB, departed from the Rudniki landing field to conduct a parachute operation. The aircraft was carrying the pilot and 11 occupants, including skydivers and tandem passengers. Shortly after takeoff, at an altitude of approximately 100 meters, the aircraft experienced a significant drop in power and an inability to climb.
The pilot initiated an emergency landing in a field near Topolów. During the final phase of the descent, the aircraft entered a severe right-hand autorotation roll of approximately 270 degrees. The aircraft subsequently struck an apple tree, which severed the left wing tip, before impacting the ground with a steep nose-down pitch and left bank. The impact caused the wings to separate from the fuselage and triggered a massive fuel leak from the damaged wing tanks. The resulting fire spread rapidly, preventing rescuers from reaching several occupants. While three individuals were initially pulled from the wreckage, 11 fatalities were recorded due to impact injuries and burns.
The investigation
The State Commission on Aircraft Accidents Investigation (SCAAI) examined the mechanical condition of the engines and propellers, the aircraft's maintenance history, and its airworthiness status. The investigation focused on the failure of the right engine's propeller system and the use of non-compliant fuel. Investigators also reviewed the aircraft's recent modifications, which had converted the cabin to accommodate 12 passengers for parachute operations.
Findings
- The primary cause of the accident was the destruction of the dowel pin coupling, which disconnected the right engine crankshaft from the propeller gear drive shaft. This rendered the right propeller inoperative and caused the blades to feather, creating a critical asymmetry of thrust that led to a stall and loss of control.
- The aircraft was being operated without a valid Airworthiness Certificate, as its US-based registration had expired.
- The use of automotive gasoline (Verva 98) instead of required aviation gasoline contributed to a power drop in the left engine.
- The aircraft had been modified for parachute operations in violation of its Type Certificate.
- High ambient temperatures and improper maintenance of the engines further degraded aircraft performance.