LAX02FA157 · Ercoupe (Eng & Research Corp.) 415C

After flying for about an hour, the engine lost power and the airplane collided with obstacles and the ground on a freeway during an attempted forced landing. The recently overhauled engine had just been installed the morning of the accident in the airframe and this was the first flight following this maintenance activity. The mechanic who installed the engine said after he completed the reinstallation he performed a 20-minute ground run of the engine. A fuel leak was noted in a fitting in the line to the carburetor and that was tightened. There were no other discrepancies noted in the engine indications. The pilot arrived at the airport after the mechanic had performed the ground run of the engine. He said the mechanic told him that the airplane was ready for a test flight and that he should take it up for about an hour to break-in the engine, changing the rpm setting every 5 minutes. The pilot said he did a preflight inspection, which included the determination that he had 6 gallons in each of the wing tanks and 6 gallons in the header tank, for a total of about 18 gallons. After the preflight, he started the engine and taxied down to the runway where he did his normal run-up process, which included two separate magneto checks. After takeoff he flew out about 3 miles and orbited while varying the rpm every 5 minutes. During the entire flight from engine start, the power plant performed perfectly with no abnormal engine indications. At the end of 1 hour, he reported to the control tower that he was ready to land and turned inbound toward the runway. On final approach, the engine just quit without any precipitating roughness or engine spool down. He said it was "like someone just turned off the key." He did not have enough altitude to make the runway and the airplane hit a fence and landed inverted on the highway. Post accident examination of the engine and related systems found numerous discrepancies and abnormal conditions related to the engine overhaul and its reinstallation in the airframe. While many of these discrepancies would have eventually induced a catistrophic engine failure, they were not contributory to the loss of engine power. Three specific conditions were likely related to the engine power loss. The engine driven fuel pump's outlet fitting was found loose and was easily moved, and the nuts attaching the fuel pump to the crankcase were found to be only finger tight. The nuts securing the P-leads for both magnetos were loose, with the nuts 2-turns from finger tight. The scuffing on the pistons indicates that the overhaul shop did not pre-oil the pistons, rings, and cylinders when the engine was put back together; this dry condition allowed a large quantity of oil to migrate past the rings, fouling the plugs with carbon deposits. The fuel system in the aircraft consists of a 6-gallon tank in each wing and a 6-gallon header tank, which is mounted in front of the cockpit. Fuel is supplied to the engine's carburetor via gravity fed line only from the header tank. The engine driven fuel pump moves fuel from the wing tanks to the header tank to replenish that supply as the engine uses it. According to the Teledyne Continental operating manual for the "C" series engines, the typical cruise fuel consumption rate of the C75 engine is between 5 and 6 gallons per hour. At the conclusion of the impact sequence, the aircraft came to rest inverted, with all three fuel tanks breched. A fuel spill was noted under the fuel tank locations in both wings, and based on the size of the fuel stain, investigators estimated at least 10 gallons had leaked. The loose fitting on the fuel pump likely allowed it to suck air and resulted in inefficeincey to the extent that the header tank was depleted of fuel, which in turn resulted in a fuel starvation event. The mechanic was going to leave town immediately after completing this job for a planned multi week vacation trip.

Verbatim NTSB analysis and probable cause from the NTSB dataset