What happened
On May 13, 2003, at approximately 10:30 UTC, a Piper PA-36-285/40 and registration CS-DCJ was performing agricultural rice sowing operations near Águas de Moura, Landeira. The aircraft, operated by a single pilot, was returning to a private airstrip to refuel and reload seeds after completing two successful flight segments.
During the return leg, the pilot heard a small explosion, immediately followed by total engine failure. Simultaneously, engine oil sprayed across the windshield, completely obscuring the pilot's forward visibility. To maintain visual contact with the ground, the pilot was forced to open the aircraft door and perform an emergency landing with his head protruding from the cockpit. The aircraft touched down in an irregular vineyard, which caused the left main landing gear to fracture.
The investigation
The GPIAAF examined the engine components and the site of the impact. The investigation focused on the internal mechanics of the Lycoming IO-720-A1B engine. Investigators found that a brake responsible for securing the roller shaft had detached. This caused a roller to dislodge from its seat and jam into a connecting rod, breaking the rod and sending fragments into the crankcase walls, which shattered the casing.
The investigation also reviewed historical data regarding similar engine failures. It was noted that a pattern of similar failures involving crankshaft/component issues had been documented both in Portugal and the United States, affecting various Lycoming engine series. The investigation confirmed that the aircraft's documentation was valid and that all maintenance programs had been strictly followed.
Findings
- The primary cause of the accident was an internal engine failure caused by the detachment of a roller shaft brake.
- The sudden engine failure and subsequent oil spray onto the windshield created a critical loss of visibility.
- The irregular terrain of the vineyard contributed to the structural damage of the left main landing gear.
- The pilot was uninjured during the occurrence.
- The engine failure type was a known recurring issue, which eventually led to the issuance of an Airworthiness Directive (AD) by the FAA and a mandatory Service Bulletin by the manufacturer.