Accident Overview
On April 28, 2024, at approximately 1815 Pacific daylight time, a Bellanca 17-31ATC (registration N8800V) was substantially damaged in an accident near El Cajon, California. The pilot sustained minor injuries. The flight was conducted as a personal flight under Title 14 Code of Federal Regulations Part 91.
Flight and Maintenance History
The pilot reported that the airplane had just undergone an annual inspection, and the purpose of the flight was to perform a test flight to verify proper functioning. During preflight, the pilot checked the engine oil level, which appeared to be about 10 quarts and seemed new. During takeoff climb, the engine oil pressure began to decrease. Concerned, the pilot decided to return to the airport. Shortly after, the oil pressure dropped to zero, followed by a complete loss of engine power. Unable to reach the airport, the pilot executed an off-airport landing on a nearby road. During the landing, the airplane struck a power line and impacted a utility pole before coming to rest upright.
Maintenance records indicated that an annual inspection was completed on April 3, 2024. According to the engine maintenance logbook, a serviceable vacuum pump was installed during that inspection. The A&P IA (Inspection Authorization) reported that a mechanic trainee performed the maintenance under his supervision. The A&P IA discussed the work scope with the trainee and periodically checked the work. After completion, he verified the work but did not check whether the hardware on the engine-driven vacuum pump was tight or torqued to a specific value. An engine test run was conducted, and the airplane was returned to the owner.
Postaccident Examination
Examination of the wreckage revealed that the nose landing gear was fracture-separated, and the fuselage near the main landing gear showed buckling. The left wing was separated at the root by recovery personnel; the right wing was separated at the root and fractured into sections. Oil residue was found along the fuselage undercarriage extending to the empennage.
The engine remained attached to its mounts, with all six cylinders and accessories still in place. Cracking was observed on the top of the engine crankcase between cylinders No. 5 and 6. The oil dipstick registered no oil in the sump.
The engine-driven vacuum pump was loosely secured to its mounting pad, with about 1/8 inch of forward-and-aft movement possible with minimal resistance. All four mounting studs were loose and had backed off from the vacuum pump. Examination of the No. 6 cylinder and piston revealed a cracked section of the crankcase. Damage to the interior crankcase near cylinders 5 and 6 was noted, along with a fractured camshaft at the rotating plane of the No. 6 connecting rod. The No. 6 connecting rod was separated at the journal end, exhibiting dark discoloration consistent with thermal damage from lubrication deprivation.
The airplane was equipped with a dry vacuum pump. According to the engine manufacturer, the vacuum pump mounting pad has a drilled passage that supplies pressurized oil for wet pump applications. In dry pump installations, this passage is sealed by the clamping force and gasket of the dry pump. If that clamping force is not maintained, oil can leak out, depleting the sump.