Strom Field Airport
Aircraft Accident/Incident Report

Morton, Washington 98356
Friday, March 19, 2010 19:10 PDT

The airplane was in cruise flight when the engine lost power. The pilot attempted to reach the nearest airport, but the airplane collided with trees about 2.5 miles short of the runway. Non-volatile memory from the cockpit instruments revealed that the engine power decreased to 1,200 and 1,750 rpms, while the fuel flow reached 30 gallons per hour (the maximum range of the fuel flow sensor). Examination of the airframe and engine revealed no evidence of preimpact mechanical anomalies except for the fitting cap on the throttle and metering assembly inlet, which was not installed. The cap was found resting on the cylinder baffle, and there was light blue staining on the crankcase indicating fuel leakage. During a postaccident engine run, the engine operated normally with a substitute cap installed finger tight. An annual inspection was completed about 11 flight hours prior to the accident, during which three engine cylinders were replaced. Following the cylinder replacement, the fuel system pressures were checked with instrumentation that was plumbed into the system at the throttle and metering assembly. Following the pressure tests, the line where the instrumentation was connected should have been secured with the fitting cap that was found not installed. The manufacturer’s maintenance procedure requires that after the pressure tests are completed the cap be torqued and that a leak check be performed. Metallurgical examination of the cap showed that if it had been properly torqued it would have remained secure. Therefore, it is likely that the cap was installed finger tight and was not properly torqued when it was reinstalled. During the accident flight, the cap loosened and came off, resulting in a loss of engine power due to fuel starvation. There was no logbook entry for the most recent annual inspection, nor had the final items on the annual inspection checklist been completed. The Director of Maintenance for the facility had signed off the work order and returned the airplane to service. The assigned mechanic with inspection authorization indicated that he had not completed the annual inspection on the airplane and that the last maintenance he performed was that noted on the work order and annual inspection checklist. If the final checks had been completed, it is likely that the improperly secured cap would have been found because the fuel leakage would have been evident.

The failure of maintenance personnel to properly secure a fitting cap on the throttle and metering assembly inlet after conducting a fuel system pressure check, which resulted in a loss of engine power due to fuel starvation. Contributing to the accident was the decision by the Director of Maintenance to return the airplane to service without verifying with the assigned inspector that all annual inspection items had been completed.