Accident Overview
After approximately one hour of flight, the engine lost power and the airplane collided with obstacles and the ground on a freeway during an attempted forced landing. The engine had recently been overhauled and was installed in the airframe the morning of the accident; this was the first flight following that maintenance.
Flight and Maintenance History
The mechanic who installed the engine performed a 20-minute ground run after reinstallation. During that run, a fuel leak was noted in a fitting on the line to the carburetor, which was then tightened. No other discrepancies were observed in the engine indications. The pilot arrived after the ground run and was told by the mechanic that the airplane was ready for a test flight, recommending a one-hour flight to break in the engine by varying rpm every five minutes.
Preflight and Flight Details
The pilot conducted a preflight inspection, determining that each wing tank contained 6 gallons and the header tank also held 6 gallons, totaling approximately 18 gallons. After starting the engine and taxiing, a normal run-up was performed, including two magneto checks. Following takeoff, the pilot flew about 3 miles away, orbiting while varying the rpm every five minutes. Throughout the flight from engine start to just before the incident, the powerplant operated normally with no abnormal indications.
Engine Power Loss
At the end of one hour, the pilot reported to the control tower that he was ready to land and turned inbound toward the runway. On final approach, the engine suddenly quit without any preceding roughness or spool-down. The pilot described it as "like someone just turned off the key." Lacking sufficient altitude to reach the runway, the aircraft struck a fence and came to rest inverted on the highway.
Post-Accident Examination
Examination of the engine and related systems revealed numerous discrepancies and abnormal conditions attributable to the engine overhaul and reinstallation. While many of these would have eventually caused catastrophic failure, they were not contributory to the power loss. Three specific conditions were likely related: the engine-driven fuel pump's outlet fitting was loose and easily moved; the nuts attaching the fuel pump to the crankcase were only finger tight; and the nuts securing the P-leads for both magnetos were loose (two turns from finger tight). Additionally, scuffing on the pistons indicated that the overhaul shop did not pre-oil the pistons, rings, and cylinders during reassembly. This dry condition allowed significant oil migration past the rings, fouling the spark plugs with carbon deposits.
Fuel System Analysis
The aircraft's fuel system consists of a 6-gallon tank in each wing and a 6-gallon header tank mounted in front of the cockpit. Fuel is supplied to the carburetor via gravity feed only from the header tank. The engine-driven fuel pump moves fuel from the wing tanks to the header tank to replenish the supply as the engine consumes it. According to the Teledyne Continental operating manual for the C75 engine, typical cruise fuel consumption is between 5 and 6 gallons per hour. At the conclusion of the impact sequence, all three fuel tanks were breached. Investigators estimated at least 10 gallons had leaked based on the fuel stain size. The loose fitting on the fuel pump likely allowed air to be sucked in, causing inefficiency and depleting the header tank, resulting in fuel starvation.