Accident
During the accident flight, the aircraft's engine ceased operation after approximately 25 minutes. The pilot executed a forced landing. Following the landing, a mechanic examined the aircraft and discovered that the carburetor bowl was dry and the fuel line vent was stuck in the closed position.
Findings
The fuel caps fitted to the aircraft were of the old unvented type. An Airworthiness Directive (AD), effective June 6, 1979, had mandated the use of vented fuel caps. However, the aircraft had not accumulated 100 flight hours since 1979, which technically exempted it from the AD's requirement. Despite this, the investigation noted that a current annual inspection would have drawn attention to the non-compliance with the AD.
Regulatory Context
The aircraft had not received an annual inspection for over 13 years, nor had it been flown in the eight years preceding the accident. The lack of a current annual inspection meant that the AD non-compliance remained unaddressed.