Accident Summary
On January 13, 2019, at 1746 eastern daylight time, a Piper PA-32R-300, registration N8892E, lost all engine power while on a visual approach to runway 5 at Lenawee County Airport (ADG) in Adrian, Michigan. The airplane subsequently struck a fence and the ground short of the runway, resulting in substantial damage. The private pilot and an airplane mechanic on board received minor injuries.
Aircraft and Flight Details
The flight was conducted as a maintenance test flight under 14 CFR Part 91, without a flight plan. Day visual meteorological conditions prevailed. The aircraft, registered to Northern Aviation Ltd, departed ADG at 1630. The pilot reported flying north between Jackson and Lansing, then southwest to Coldwater and Hillsdale, before returning to ADG for landing.
Pilot and Mechanic Statements
According to the pilot's statement to the FAA, the flight was a post-annual inspection check with the mechanic who had signed off the last annual. During the approach, the pilot had set engine power to 14 inches of manifold pressure, with landing gear and flaps extended. On short final, the engine shut off abruptly, with no sputtering—as if the ignition had been switched off. The pilot did not complete the NTSB accident report narrative section.
Post-accident interviews with the airframe and powerplant (AP) mechanic who overhauled the engine revealed that he was the owner of a tool and die shop and spent about 25% of his time on aircraft repairs. He stated this was the first large Lycoming engine he had overhauled, that he found Lycoming manuals difficult to follow, and that he did not torque the crankshaft gear bolt to manufacturer specifications. The AP had contacted Lycoming for documentation assistance. The mechanics who signed off the overhaul included an IA who removed and reinstalled the engine.
Post-Accident Examination
Examination of the Lycoming IO-540-K1G5D engine (serial number L-13642-48A) revealed that the crankshaft gear bolt (part number 13S19649) was fractured. Logbook entries from August 24, 2013, indicated that during an overhaul at tachometer time 3,399.87 hours, an AN8-14 bolt was installed; however, the illustrated parts catalog and mandatory service bulletin 475C specified an AN8-14A bolt. The tachometer at the accident was approximately 3,466 hours. The NTSB Materials Laboratory examined the fractured bolt and found its dimensions consistent with an AN8-14A bolt (no drilled hole in the shank).
Crankshaft Gear Bolt Analysis
Fractographic analysis using visual and scanning electron microscopy showed features consistent with fatigue crack propagation and subsequent overstress. Two thumbnail cracks were present on opposite sides of the fracture surface, near the bottom of a thread root. The larger crack exhibited fatigue striations and crack arrest marks; the smaller crack also showed striations. The cracks propagated inward from multiple initiation sites. There were no material or mechanical defects such as corrosion pits, pores, or voids. The remaining cross-section fractured from overstress. The bolt had been cycling under reverse bending, leading to fatigue cracking. The AP mechanic's failure to torque the bolt to specifications was noted in the investigation.