What happened
On 23 November 2017, a Pilatus PC6-B2-H2, registration EC-EMZ, was performing a commercial skydiving operation at the Empuriabrava aerodrome in Girona, Spain. After completing a parachute drop, the pilot began a descent to join the left-hand traffic pattern for runway 17.
As the pilot increased power to stabilize the descent and continue the pattern, the engine failed to respond. At an altitude of approximately 1,500 feet, the pilot made one unsuccessful attempt to restart the engine. Due to the low altitude and the loss of power, the pilot prepared for an emergency landing. During the approach, the aircraft's airspeed dropped below 50 knots, and the landing gear impacted the edge of a canal, causing the aircraft to strike the ground. The pilot, who was the sole occupant, was uninjured and able to exit the aircraft under his own power.
The investigation
The CIAIAC investigation focused on the engine's performance and the pilot's actions during the emergency. Technical inspections of the engine and the fuel control unit (FCU) were conducted, along with a disassembly and analysis of the engine's hot section. The investigation also reviewed maintenance records, which showed the aircraft had been maintained according to manufacturer recommendations and was in an airworthy condition.
Investigators examined the flight parameters and the sequence of events leading to the engine stoppage. The analysis included testing the fuel control unit and inspecting the engine for any mechanical defects or fuel starvation issues. The investigation also looked into the pilot's use of engine parameters and the execution of emergency restart procedures.
Findings
- The investigation ruled out any technical malfunction in the engine or the aircraft as the cause of the stoppage.
- The engine stoppage was likely a flameout in the combustion chamber caused by an improper rapid descent, where the throttle was held below the idle position, leading to a poor air/fuel mixture.
- The engine actually restarted in flight during the attempt to recover, as evidenced by the fact that the engine was running and the propeller was in a fine pitch position upon impact.
- The pilot did not monitor essential engine parameters, such as ITT and Ng, which could have helped identify the flameout.
- The improper execution of emergency procedures for an engine failure and in-flight restart contributed to the accident, as the pilot failed to recognize the recoverable nature of the flameout at a sufficient altitude.