WPR09LA213

The flight instructor reported that the helicopter's engine lost power when they were about 15 feet above the ground while making an approach to land on a pinnacle during an instructional flight. The helicopter hit the ground hard and then rolled down the hill and came to rest on its right side. During the post accident inspection, the engine was removed from the airframe and installed into a dynamometer test stand. The engine started on the first attempt and ran smooth and exhibited no abnormal indications or sounds.

HISTORY OF FLIGHT On April 22, 2009, about 1400 Pacific daylight time, a Schweizer 269C helicopter, N17YS, landed hard following a loss of engine power near Las Vegas, Nevada. Airwork LLC was operating the helicopter under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The commercial pilot with a certified flight instructor (CFI) certificate and the student pilot undergoing instruction (PUI) were not injured; the helicopter sustained substantial damage when it rolled over. The local instructional flight departed the North Las Vegas airport about 1330. Visual meteorological conditions prevailed, and no flight plan had been filed. The CFI reported that while making an approach to land on a pinnacle, the helicopter engine lost power when they were about 15 feet above the ground. The helicopter hit the ground hard and then rolled down the hill and came to rest on its right side. The helicopter was examined on site by Federal Aviation Administration (FAA) inspectors and recovered for further examination. The FAA inspectors attempted to start the engine, but the engine appeared to be “locked up.” On May 13, 2009, investigators examined the engine at the owner’s hangar facilities at the North Las Vegas airport. During the engine examination, the top spark plugs were removed and noted that they were free of mechanical malfunction at the electrodes. The engine cooling fan was rotated by hand in the direction of normal rotation, at which time copious amounts of engine oil was forced out of the spark plug holes of the number 2 and 4 cylinders. Mechanical continuity was established throughout the engine during the thumb compression check. The magnetos remained secure on their respective mounting flanges. The spark plugs and exhaust system components exhibited a light gray-brown coloration and remained free of oil residue. The oil suction screen remained free of visible contaminates. The engine was transported to the facilities of Nevada Aircraft Engines, Henderson, Nevada, to be run on a dynamometer test stand under the supervision of the investigation team. The engine started on the first attempt, and after a warm-up and magneto check, the engine produced 185 hp at 3,065 rpm. According to the data plate affixed to the engine, the subject engine is rated at 190 hp at 3,200 rpm. The engine ran smooth and exhibited no abnormal indications or sounds. Investigators concluded that engine oil migration into the number 2 and 4 cylinders occurred during the time the helicopter lay resting on its right side. This contributed to a hydraulic lock event that was present when the Federal Aviation Administration inspectors attempted to start the engine. Once the oil was drained from the cylinders during the thumb compression check, the condition was mitigated, which allowed unimpeded full rotation of the crankshaft.