History of Flight
On April 22, 2009, about 1400 Pacific daylight time, a Schweizer 269C helicopter, registration N17YS, experienced a hard landing following a loss of engine power near Las Vegas, Nevada. Airwork LLC operated the helicopter under 14 Code of Federal Regulations Part 91. The commercial pilot, who held a certified flight instructor (CFI) certificate, and a student pilot undergoing instruction were not injured. The helicopter sustained substantial damage when it rolled over. The local instructional flight had departed North Las Vegas Airport about 1330. Visual meteorological conditions prevailed, and no flight plan was filed.
The CFI reported that during an approach to land on a pinnacle, the helicopter engine lost power when the aircraft was approximately 15 feet above the ground. The helicopter struck the ground hard and then rolled down a hill, coming to rest on its right side.
Examination
Federal Aviation Administration (FAA) inspectors examined the helicopter at the site and later recovered it for further investigation. When they attempted to start the engine, it appeared to be “locked up.”
On May 13, 2009, investigators examined the engine at the owner’s hangar facilities at North Las Vegas Airport. They removed the top spark plugs and noted no mechanical malfunction at the electrodes. When the engine cooling fan was rotated by hand in the direction of normal rotation, copious amounts of engine oil were forced out of the spark plug holes of the number 2 and 4 cylinders. Mechanical continuity was established throughout the engine during a thumb compression check. The magnetos remained secure on their mounting flanges. The spark plugs and exhaust system components exhibited a light gray-brown coloration and were free of oil residue. The oil suction screen had no visible contaminants.
Engine Test
The engine was transported to Nevada Aircraft Engines in Henderson, Nevada, for a dynamometer test under the supervision of the investigation team. The engine started on the first attempt. After warm-up and a magneto check, it produced 185 horsepower at 3,065 rpm. According to the data plate, the engine is rated at 190 horsepower at 3,200 rpm. The engine ran smoothly with no abnormal indications or sounds.
Investigators concluded that engine oil migration into the number 2 and 4 cylinders occurred while the helicopter lay on its right side after the accident. This created a hydraulic lock condition when FAA inspectors attempted to start the engine. Once the oil drained from the cylinders during the thumb compression check, the condition was resolved, allowing unimpeded full crankshaft rotation.