What happened
On March 24, 2006, at approximately 17:10, a Cessna 172P equipped with a diesel engine, registration OH-CVB, experienced a sudden engine failure during the takeoff roll at Joensuu Airport. The pilot, flying solo, had initiated the takeoff from the midpoint of the runway. At an altitude of approximately 300 ft, the engine ceased operation, forcing the pilot to perform an emergency landing in a snowbank in the forward sector of the airfield. During the landing roll, the aircraft overturned. The pilot sustained only minor injuries.
The investigation
The investigation focused on the engine's failure and the circumstances surrounding the recent maintenance of the aircraft. Prior to the flight, the aircraft had undergone a 200-hour scheduled maintenance check and an annual inspection. During this service, an oil pressure sensor was replaced, which required manipulating the intake air tube. The investigation established that while one mechanic performed the sensor replacement, a second mechanic was tasked with reattaching the tube. To alleviate tension in the tube, the second mechanic loosened a rear worm-drive clamp but failed to retighten it.
Investigators also examined the engine ground test performed after the maintenance. Due to a slippery apron surface, the test run at maximum power was cut short and did not meet the 30-second duration specified in the maintenance instructions. Furthermore, the investigation found that the pilot had not utilized the full length of the runway for the takeoff, which limited the available distance for an emergency landing on the pavement.
Findings
- The primary cause of the engine failure was the disconnection of the intake air tube attachment during the initial climb. The loose connection allowed the flexible rubber tube to be sucked into the intake, causing an immediate blockage and engine shutdown.
- The loose clamp was not detected during the final maintenance inspection or during the abbreviated engine ground test.
- The engine ground test was insufficient because the slippery surface prevented the aircraft from remaining stationary during the required 30-second full-power application, a duration necessary to reveal potential loose fittings.
- The emergency landing occurred off the runway because the takeoff was initiated from the middle of the runway, leaving insufficient pavement for a landing.
- The pilot did not utilize flaps during the emergency descent, which could have increased the rate of descent and shortened the landing distance.