Piper PA46 N4646G accident near Radisson, Wisconsin

Probable cause

The non-certificated mechanic’s failure to properly tighten and torque the fuel system pressure test port cap, which resulted in a total loss of engine power, and a subsequent forced landing.

NTSB analysis

The engine sustained a total loss of power when nearing the destination airport during a cross-country flight. The pilot performed a forced landing to a rural grass field and the airplane landed hard, coming to rest upright. The pilot was able to egress from the airplane without further incident. The airplane sustained substantial damage to the fuselage and the empennage.

An on-site examination of the engine found that a cap was missing from the fuel pressure test port near the front top area of the engine. The test port is where a gauge would connect during maintenance work to test the fuel pressure. The test port and the aluminum housing that the port connects to both had blue staining. The exposed threading that the cap screws onto was found intact and the missing cap was not located.

A review of the engine monitor performance data showed performance consistent with a total loss of engine power. The fuel flow rate had increased up to the maximum reading, about 80 gallons per hour, at the time the total loss of engine power occurred.

A review of the most recent airplane maintenance records showed than an annual inspection was performed on the airframe, engine, and propeller about six weeks before the accident. The records reflected work completed on the fuel injection system, including the installation of new fuel injectors. According to the engine manufacturer, a fuel system operational check is required if fuel injectors are replaced. Test equipment is connected to the fuel pressure test port and a test is performed. Once the test work is completed, a cap is required to be tightened and torqued on the test port.

The individual who performed the most recent annual inspections on the airplane did not hold an airframe and powerplant certificate, nor did he hold inspection authorization. The non-certificated mechanic signed off the annual inspections and returned the airplane to service using the airframe and powerplant mechanic certificate number of his deceased father, who held inspection authorization.

The test port had blue staining present, and the exposed threading was found intact. The aluminum housing that the port connects to also had blue staining present. The blue staining was likely from a 100 low-lead fuel leak while in-flight. It is likely the loss of fuel and fuel system pressure caused a total loss of engine power.

Based on the available evidence, it is likely that the non-certificated mechanic forgot to properly tighten and torque the fuel pressure test port cap, which resulted in a total loss of engine power. The non-certificated mechanic fraudulently represented himself as a certificated mechanic with inspection authorization and the appropriate knowledge, training, and experience by signing off the annual inspections and returning the airplane to service.

Text from the NTSB. Open the NTSB docket for CEN24LA286 for the full record.