ANC99LA043

During initial climb, about 1,500 feet above ground level, as the pilot made his first power reduction, the engine quit. The pilot stated 'it quit so fast I knew I had a problem.' The pilot waited until he cleared trees to extend the landing gear, and landed the airplane on a road. The landing gear did not lock into the down position and collapsed. The right wing struck a snow berm. Inspection revealed that one of the bolts joining the number six connecting rod to the crankshaft had separated. The nut was found in the bottom of the crankcase. Inspection of the bolt and nut at the NTSB metallurgical laboratory did not reveal any preaccident damage to the threads on either the bolt or the nut. The torque on the other 11 connecting rod attachment nuts was checked to be 480 inch-pounds. The engine had been overhauled 241 hours prior to the accident.

On April 5, 1999, at 1053 Alaska daylight time, a Piper PA-32R airplane, N1942H, sustained substantial damage during a forced landing at Fairbanks, Alaska. The solo commercial pilot received minor injuries. The airplane was being operated under 14 CFR Part 135 as a cargo flight from Fairbanks International Airport, Fairbanks, to Fort Yukon, Alaska. The flight departed Fairbanks International Airport at 1050. Visual meteorological conditions prevailed at the time of the accident, and a company VFR flight plan was filed.

According to the two FAA inspectors who interviewed the pilot at the scene, the pilot made an initial power reduction upon reaching 1,500 feet above the ground (agl). He said he then heard a loud "thump" and "it quit so fast I knew I had a problem. I guessed a blown cylinder." He indicated he turned to find a place to land, and waited until he cleared trees to lower the landing gear. He put the landing gear down but they did not lock in place. The pilot landed the airplane on a road, and the landing gear collapsed. The left wing struck a tree and came off, then the right wing struck a snow berm and came off.

Postaccident inspection revealed a hole in the engine case at the number six cylinder, and the number six connecting rod loose inside the engine case. Internal inspection of the engine by an FAA airworthiness inspector on April 8 revealed that one of the connecting rod bolts (Lycoming part number 75060) holding the connecting rod to the journal was separated. The matching nut (Lycoming part number LW-12186) was found in the bottom of the oil sump with no apparent internal thread damage. Inspection of these parts at the NTSB metallurgical laboratory revealed that the threads of both the bolt, and the nut, were not fractured or stripped. The washer face of the retaining nut showed circumferential smearing consistent with tightening contact onto the mating area of the rod.

The Lycoming nut (LW-12186) does not have a self-locking feature. It is specified to be torqued to a value of 480 inch-pounds, or 40 foot-pounds. The breakaway torque on the remaining nuts was checked, and the torque values were 480 inch-pounds. The engine had accumulated 241 hours since overhaul.