A maintenance test flight ended in a crash when a Piper PA-32R-300 experienced a total loss of engine power during a visual approach to Runway 5 at Lenawee County Airport (KADG) in Adrian, Michigan.
The airplane hit a fence and terrain short of the runway and sustained substantial damage. The private pilot and an airplane mechanic received minor injuries.
According to the pilot, the flight departed with the airplane mechanic with inspection authorization (IA) who signed off the airplane’s last annual inspection, for a post annual inspection flight. They flew north between Jackson and Lansing, Michigan, and then proceeded southwest to Coldwater, Michigan, and then Hillsdale, Michigan.
They returned for an approach and landing to KADG on Runway 5 with engine power set to 14 inches of manifold pressure, landing gear extended, and flaps extended. On short final for Runway 5, the “engine shut off,” according to the pilot, who added there was “no sputter — it acted as if someone shut off the key.”
Post-accident examination of the engine revealed that the crankshaft gear bolt was fractured through. A logbook entry dated Aug. 24, 2013, at a tachometer time of 3,399.87 hours and a time since overhaul of 0 hours, stated that the engine was disassembled, and an AN8-14 bolt was installed.
Following the accident, FAA inspectors interviewed the airframe and power plant mechanic (AP) who last overhauled the engine. During the interview, he stated he is the owner of a tool and die shop that also does manufacturing of various parts for the auto industry. He spends about 25% of his working time in his hangar performing aircraft repair. He stated that he is most comfortable working on old, small, fabric-covered aircraft.
The AP stated that he was the one that overhauled the engine on N8892E and the IA just removed and re-installed the engine onto the airplane.
The AP also stated that this was the first of the “big” Lycoming engines that he had overhauled. The AP told inspectors that he does not like using the Lycoming manuals, as they are hard to follow. The AP mentioned several times that he had contacted Lycoming to request assistance, and they worked with him in providing the necessary documentation needed for the work he was doing. The AP stated that he did not torque the crankshaft gear bolt to the engine manufacturer’s specifications.
The engine overhaul was signed off by the AP.
A National Transportation Safety Board Materials Laboratory post-accident examination of the bolt revealed that it had fractured 1.038 inches below the bolt head.
The bolt features were consistent with fatigue cracking that initiated at multiple sites near the bottom of a thread root. These smaller cracked coalesced and propagated inward through more than half the crack section of the bolt. The bolt began to cycle under reverse bending, which initiated fatigue cracking at multiple sites along the thread root on the opposite side. Once both cracks had propagated inward to the extent present on the fracture surfaces, the remaining cross section of the bolt fractured from overstress.
Probable Cause: The airframe and powerplant mechanic’s lack of experience in the overhaul of the engine model and the improper torque of the crankshaft gear bolt, which resulted in fatigue failure of the bolt and a total loss of engine power during an approach for landing.
This January 2019 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.