Accident Narrative
According to the flight instructor, engine power rose smoothly during the takeoff roll. However, at approximately 600 feet above ground level, the engine abruptly ceased operation. The instructor assumed control of the aircraft, aligned the airplane with a major interstate highway, and touched down on the northbound travel lanes. During the landing rollout, the right wing contacted a bush, causing the airplane to rotate and depart the highway, coming to rest down the adjacent embankment.
Engine Examination
A subsequent teardown of the engine disclosed that the crankshaft idler gear, associated with the left magneto, had become detached from its mounting pad at the rear of the crankcase. The crankshaft gear was not secured to the crankshaft, and the locating dowel pin was found fractured and separated. Further inspection of the idler gear shaft and attaching hardware revealed severe wear on the attachment bolts and locking plate. The bolts exhibited wear patterns consistent with prolonged contact with the rotating idler gear. The bore of the idler gear shaft mounting pad was also severely worn and elongated. At the crankshaft counterbore and corresponding gear, fretting and corrosion were present at the mating surfaces. The dowel pin was separated along the parting surfaces of the gear and counterbore, and the fracture surface displayed characteristics of fatigue.
Propeller Maintenance
A propeller overhaul had been completed 20 flight hours prior to the accident. According to the Hartzell propeller manual, balance weights are limited to a maximum of 0.9 ounces (25.51 grams) at any single location on the spinner. During the post‑accident inspection, balance weights totaling 36 grams were found installed at one location on the airplane's spinner.