What happened
On September 10, 2020, a Piper PA-28R-201T departed from a private airstrip near Slots Bjergby, Denmark, bound for Omø. During the initial climb, at an altitude of approximately 300 feet, the engine power abruptly dropped from takeoff power to idle. To avoid power lines, the pilot executed a left turn toward a southern heading.
Following the engine power loss, the pilot initiated emergency procedures but was unable to restore engine RPM. The pilot subsequently selected a harvested rapeseed field for an emergency landing. During the touchdown, the landing gear collapsed, causing the propeller, wings, and the lower fuselage to contact the ground. The aircraft skidded for approximately 50 to 100 meters before coming to a stop. There were no injuries to the pilot.
The investigation
The Danish Accident Investigation Board conducted a technical examination of the aircraft's fuel system and engine components. The investigation focused on the fuel primer valve, which is used to facilitate cold engine starts by directing fuel to specific nozzles.
Technical tests revealed that while the primer valve functioned as designed during controlled laboratory settings, the engine exhibited significant power fluctuations when the primer valve was activated during testing. Specifically, once the valve was activated at low RPM, the engine failed to return to its original RPM even after the valve was deactivated, making throttle control impossible.
Furthermore, the investigation identified that two critical manufacturer notices had not been addressed on OY-BYC. A 1989 Piper Service Bulletin, which mandated the replacement of the primer valve switch to prevent uncontrolled activation, had not been implemented despite the aircraft having flown well beyond the 100-hour service limit. Additionally, a 2019 Continental Critical Service Bulletin, which recommended the complete removal of the primer valve to prevent power loss, had also not been carried out.