What happened
On 31 May 2017, a Reims Cessna FR172F Rocket, registration G-DRAM, was conducting a private flight when the engine began running roughly. This mechanical issue forced the pilot to declare a PAN-PAN urgency and prioritize an immediate landing at Prestwick Airport.
During the approach, the pilot selected the landing gear to the down position. Both the pilot and the passenger observed the mechanical gear indicator flags to verify the gear status, though the pilot could not definitively confirm if all green 'down and locked' lights were illuminated. Following a smooth touchdown, the aircraft traveled approximately 4/50 metres along the runway before veering left and coming to a halt on the runway shoulder. The impact resulted in damage to the left float.
The investigation
Investigators examined the aircraft to determine why the gear failed despite the mechanical indicators suggesting it was down. Upon lifting the aircraft, the left main gear was found to be extended and locked. Subsequent testing of the retractable landing gear system revealed no operational faults or malfunctions.
An inspection of the engine identified significant fouling on one of the spark plugs, which was linked to the engine roughness experienced during flight. The investigation also looked into the pilot's actions during the emergency, noting that the pressure of the PAN-PAN situation may have limited the opportunity to perform a secondary verification of the gear configuration.
Findings
- The primary cause of the engine instability was significant fouling of a single spark plug.
- The left landing gear collapsed during the landing roll, causing the left float to strike the runway.
- The pilot's focus on managing the engine emergency may have prevented a thorough secondary check of the landing gear lights.