Accident Overview
On 13 May 2003, at approximately 10:30 UTC, a Piper PA-36-285/400 agricultural aircraft, registration CS-DCJ, was returning to the private airstrip at Águas de Moura, Landeira, after completing two rice seeding flights over fields of the Zambujal agricultural estate. The pilot, the sole occupant, heard a small explosion followed by a complete engine stoppage. Seconds later, the windscreen became completely obscured by engine oil. The pilot opened the aircraft door to maintain visibility and carried out an emergency landing in an uneven vineyard terrain. The landing resulted in a fracture of the left main landing gear leg. The pilot exited the aircraft uninjured.
Engine Examination
The engine was removed and inspected at an INAC-approved facility. Disassembly revealed that the retaining lock for the roller shaft had come loose. One roller detached from its seat and jammed against a connecting rod, breaking it. Fragments of the connecting rod struck the crankcase walls with sufficient force to shatter them.
Similar Occurrences
A search for analogous events found that between 1983 and 1998, 13 similar engine failures had been recorded in Portugal. In the United States, 23 notifications of engine failures—involving not only the IO-720 series but also L(O)-360, (L)IO-360, AEIO-360, O-540, IO-540, AEIO-540, (L)TIO-540, and IO-580 engines—were attributed to connecting rod fractures. The frequency of such accidents, some with fatal outcomes, led the Federal Aviation Administration (FAA) to issue an Airworthiness Directive (AD) in 2006 requiring replacement of certain connecting rods. The aircraft manufacturer also issued a mandatory Service Bulletin in 2006, mandating replacement of affected connecting rods by February 21, 2009.
Conclusions
The investigation determined that the accident was caused by an engine failure resulting from a connecting rod fracture due to the detachment of a roller from the connecting rod shaft.