What happened
On September 14, 2019, a pilot and the aircraft owner departed from a landing strip in Stary Wielisław for a local flight. While flying at approximately 1,000 meters in the Bystrzyca Kłodzka region, the pilot attempted to shut down the engine to utilize thermal updrafts for gliding.
Following the deactivation of the magnetos, the engine seized while the propeller remained in motion. The pilot reported hearing an unusual noise but determined the Pipistrel Taurus 503, registration SP-STAU, remained fully controllable. The pilot decided to return to the departure airfield; however, the aircraft experienced a higher-than-normal rate of descent due to the non-functioning, protruding engine assembly.
As the pilot transitioned to a landing approach on runway 33, they realized the aircraft was too low to reach the landing strip. The aircraft subsequently landed short of the runway on a plowed field. During the landing roll on the uneven terrain, the wingtips struck the ground several times before the aircraft came to a stop approximately 30 meters from the runway threshold. There were no injuries reported.
The investigation
The PKBWL examined the mechanical sequence of the engine retraction system. The standard automated procedure requires the engine to shut down, the propeller to come to a complete stop, and the propeller to reach a vertical position before the engine and propeller assembly retract into the fuselage.
The investigation established that an incorrect and incomplete retraction sequence occurred, which caused the control mechanism to jam. This malfunction resulted in damage to the engine cowlings and the propeller edge. While the pilot suggested a momentary sensor failure might have caused the malfunction, a manufacturer inspection found no issues with the mechanical actuator or the sensor. Following repairs, the aircraft was returned to service.
Findings
- The primary cause of the incident was a momentary malfunction of the control system responsible for the engine retraction mechanism.
- The improper retraction sequence led to the engine assembly becoming stuck in a protruding position.
- The landing on uneven, plowed terrain caused additional damage to the landing gear and wingtips.