Occurrence
On September 4, 2016, at approximately 19:50 local time (16:50 UTC), a Cessna 150M aircraft, registered HA-SKF, departed from Ineu airfield in Bihor County for a private flight with a pilot and one passenger. About 30 minutes into the flight, southeast of Oradea near Cheriu locality, the pilot heard abnormal noises from the engine and noticed a decrease in engine rotation. Other engine parameters appeared normal. When the pilot operated the throttle, engine rotation did not respond.
As the engine no longer provided power, the pilot began a slow descent to search for an emergency landing site, determining that returning to Ineu or Oradea International Airport was not feasible. Shortly after, smoke appeared in the cockpit, prompting the pilot to perform an emergency landing. Considering the terrain and obstacles, the pilot selected an agricultural field east of Cheriu.
The aircraft touched down on its main wheels, but as speed reduced and the nose wheel lowered, it sank into the soft ground, causing the aircraft to nose over. The pilot shut off all electrical contacts and vacated the aircraft with the passenger, neither sustaining injury.
Investigation Findings
The investigation commission examined the aircraft after it was transported back to its departure airfield. Samples of gasoline and oil were taken and analyzed by an authorized laboratory; both met manufacturer specifications.
The engine (Continental O-200A) was removed and subjected to a technical expertise by an approved maintenance organization. The examination revealed that cylinder No. 4 was cracked along approximately 90% of its circumference. The piston rings on that cylinder were broken. Traces of oxidation and rust were present on the crack. The oil filter contained no metallic particles, indicating the failure occurred during the flight.
The crack likely originated in an area not visible during routine maintenance, causing a minor oil leak. As the engine operated, the crack propagated, compromising piston ring function. The rings entered the widened crack and broke, producing the metallic sound, loss of power, and smoke reported by the pilot.
Maintenance History
According to the aircraft logbook, the last flight recorded before the accident was on October 17, 2012. A maintenance activity was noted on May 24, 2012, and the next on January 15, 2016. No maintenance to prepare the aircraft for storage was recorded between these dates.
The engine logbook recorded two overhauls: the first in 1994 after 1,710 hours, and the second in 2002 after 2,139 hours from the previous overhaul. The engine manufacturer's Service Information Letter SIL98-9C recommends overhaul at 1,800 hours or 12 years, whichever comes first. The second overhaul exceeded this limit by 339 hours. Additionally, cylinder No. 4 was replaced on May 12, 2006, but the work was not certified.
In 2016, the aircraft underwent maintenance by an approved organization, concluded with a Certificate of Release to Service on July 25, 2016. An airworthiness review was performed by the same organization, issuing an Airworthiness Review Certificate stating the aircraft was airworthy. The investigation noted that the review did not account for the lack of storage preparation since 2012 and that the engine had exceeded the manufacturer's calendar time limit for overhaul.
Conclusion
The investigation determined that the emergency landing was necessitated by an engine failure caused by a cracked cylinder No. 4, which led to broken piston rings and loss of power.