WPR23LA239

A loss of engine power due to the failure of the right magneto distributor gear and the pilot’s decision to conduct a test flight with known mechanical issues.

The pilot reported that, shortly after takeoff, the airplane’s engine began to run rough, so he returned to the airport, landed uneventfully, parked the airplane, and deplaned his passengers to conduct another preflight inspection. The pilot sampled the fuel, checked for loose spark plugs, and checked the magnetos. The pilot then decided to do an engine run-up and test flight before departing the area with the passengers. After takeoff, about 100 ft above ground level (agl), the engine began to shake violently, and he initiated a turn back to the airport. The engine lost total power, and the airplane landed hard and came to rest upright in the grass adjacent to the runway, resulting in substantial damage to fuselage, both wings, and the right horizontal stabilizer. Postaccident examination of the engine established mechanical and valvetrain continuity. When the propeller was rotated, the No. 5 ignition harness top lead did not spark. The right magneto was removed and functionally tested with an intermittent spark. The left magneto was also removed, and spark was obtained on all posts during the functional check. Further testing revealed that the intermittent spark from the right magneto could not be duplicated. Disassembly of right magneto revealed about 1/4 of the teeth were separated from the distributor gear, which would likely result in a partial loss of engine power and a rough running engine. No additional evidence of any preexisting mechanical malfunctions that would have precluded normal operation were observed with either magneto.

On June 25, 2023, at 0900, Pacific daylight time, a Piper PA-24-250, N6430P, was substantially damaged when it was involved in an accident near Alturas, California. The pilot sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that, after departure from Alturas Municipal Airport (AAT), with two passengers onboard, the engine began to miss and run rough. He returned to the airport, landed uneventfully, parked, and exited the airplane. He stated that he performed a full preflight inspection of the airplane, which included sampling fuel from all four fuel tanks and checking for “loose spark plugs, mags, [etc].” All engine components “looked good.” The pilot stated that he wanted to do an engine run up and test flight without his passengers before continuing the flight to their intended destination.  The pilot stated that the pre-takeoff engine run up was normal, and he departed from runway 21. After climbing “a couple hundred feet,” the engine began to violently shake. The pilot initiated a left turn back to the airport and the engine lost all power. The airplane descended, landed hard, and came to rest upright in the grass adjacent to the runway. The on-site examination revealed that the airplane remained upright and intact with substantial damage to the fuselage, both wings and the right horizontal stabilizer. Postaccident examination of the airframe revealed no preimpact mechanical malfunctions that would have precluded normal operation. Postaccident examination of the engine revealed several pin holes in the exhaust tube surrounding the exhaust gas temperature (EGT) probe hole. Mechanical and valvetrain continuity was established via manual rotation of the propeller. However, when the propeller was rotated, spark from the ignition harness No. 5 top lead was not present. Both magnetos were intact and secure at their respective mounting pads. The right magneto was removed and a functional test garnered intermittent spark. The left magneto was also removed and functionally checked with no discrepancies. Both magnetos were shipped to Continental Aerospace Technologies with no discrepancies noted during a bench test. The right magneto was disassembled and about 1/4 of the distributor gear teeth were found separated from the distributor gear. No evidence of any additional mechanical anomalies was observed with either magneto. No maintenance records for the magnetos, engine or airframe were made available during the investigation.