19980815038059A

(.19) On August 15, 1998, about 1415 Alaska daylight time, a wheel equipped Cessna 172 airplane, N7966B, sustained substantial damage during an emergency landing after takeoff from the Palmer Municipal Airport, Palmer, Alaska. The airplane was being operated as a visual flight rules local area instructional flight under title 14 CFR part 91 when the accident occurred. The airplane is registered to and operated by mustang air, inc., Palmer. The solo student pilot was not injured. Visual meteorological conditions prevailed, and company flight following procedures were in effect. The flight originated at the Palmer Municipal Airport, about 1413. During a telephone conversation with the national transportation safety board investigator-in-charge, on August 15, the student pilot reported that he was departing on runway 15. He said that as the airplane climbed to about 600 feet above the runway, near midfield, the engine developed a severe vibration followed by a "very loud bang." The pilot stated that he made an emergency landing on a golf course at the southeast end of the airport. During the landing roll, the airplane's right wing struck a stand of trees. After the emergency landing, the pilot noticed that the entire propeller, propeller flange and the outboard end of the engine crankshaft were missing from the engine. The missing propeller components were later located near the midpoint of the departure runway. The airplane's right wing sustained substantial damage. (.4) the student pilot was departing on runway 15, on his first solo flight. He stated that during the initial climb, the engine developed a severe vibration followed by a 'very loud bang'. He made a forced landing on a golf course at the southeast end of the airport. During the landing roll, the airplane's right wing struck a small hill, and sustained substantial damage. After landing, the pilot discovered that the entire propeller, propeller flange, and the outboard end of the engine crankshaft were missing. They were later located near the midpoint of the departure runway. An FAA airworthiness inspector's review of the engine log book discovered that the accident engine had previously sustained two propeller strikes. He reported that the log book failed to reflect any inspection following the prop strikes. An NTSB metallurgical examination of the propeller FL ange assembly revealed multiple clamshell marks, typical of fatigue cracking. The engine is the subject of a Lycoming engine service letter, L163C, that recommends that any engine involved in a sudden stoppage event be removed, dissembled, and inspected prior to returning the engine to service. (-23) on August 15, 1998, at approximately 1430 daylight time, Cessna 172, aircraft N766B, made a forced landing on the golf course parallel to runway 15, after departure at Palmer, Alaska. The crankshaft broke off just ahead of the nose case at approximately 600 feet in the air, the propeller/crankshaft flange landed on the runway. After review of the log books, it was determined that in the past, the engine had a prop strike and the owner at the time, elected not to dissassemble and inspect the crankshaft as per the manufacturer's recommendations.