Lack of maintenance leads to forced landing

The sport pilot was conducting a cross-country flight in the light-sport airplane, a Rans S12XL, when, after about an hour of flight, the engine first experienced a partial loss of power, followed shortly by a total loss of power.

The pilot twice unsuccessfully attempted to restart the engine using the emergency checklist before performing a forced landing to a field near Guanica, Puerto Rico. During the landing, the airplane sustained substantial damage to the fuselage.

The engine was manufactured about 10 years before the accident and maintenance logs indicated that it had not been overhauled since that time.

Examination of the engine revealed that connecting rod bearing material was distributed throughout the power take off (PTO) section of the engine. Furthermore, corrosion was noted on the PTO connecting rod and connecting rod bearing.

Although the engine had not yet reached the manufacturer’s recommended 300 flight hour time limit for overhaul, it had exceeded the recommended five-year calendar time limit for overhaul by five years.

It is likely that a piece of the failed bearing became lodged in the rotary valve disc, which prevented the disc from rotating, and subsequently blocked the air and fuel to the engine, which resulted in a total loss of engine power.

Had the engine been overhauled, the corrosion likely would have been discovered and the inflight loss of power prevented.

Probable cause: The pilot/owner’s failure to maintain the engine in accordance with manufacturer guidance, which resulted in the undetected corrosion of the power takeoff bearing, subsequent bearing failure, and a total loss of engine power.

NTSB Identification: ERA16LA076

This December 2015 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.