20150601011989A

A Bell 206, N73AW, reported engine problems, which caused the aircraft to autorotate in a field near Dewey, AZ., on 6/2/15. The helicopter was owned and operated by air medical services of glendale, AZ. And was being ferried from valle airport, grand canyon AZ. (40G) to glendale municipal airport, AZ (geu), when the incident occurred. Damage to the helicopter was substantial. There were no injuries to the lone occupant of the helicopter, the pilot. It was determined at the time that weather was not a factor.

The pilots stated that while he was enroute he heard an audibly loud pop corresponding with a red engine out light and engine out horn. The pilot immediately located a safe area to land and entered into an autorotation. During the descent he was able to confirm that the engine was out. He attempted to rolled throttle to the detent/idle position, but no change occurred. After landing he noted that the main rotor and tail rotor blades were freewheeling until they slowed to a stop. After exiting the aircraft, he saw noticeable damage to various parts of tail section. He stated that prior to the engine out, while enroute, there were two separate occurrences where the engine chip light flashed on and off momentarily.

Prior to the incident the aircraft had had two other engine chip lights recorded in the logbooks. On the first occasion, maintenance did not find any metal particles or sludge on the chip detectors or in the filter. The filter was removed and replaced and the engine was ran and check good. On the second occasion, maintenance did not find any evidence of metal particles again. The operator decided to have the oil analyzed by a laboratory. The aircraft remained at valle airport until the oil analysis was returned. Oil analysis was sent to AOA tribology and came back ?all values appear normal?. This was verified via documentation. After the laboratory results came back normal, the operator decided to ferry the aircraft back to the maintenance base for further troubleshooting.

After the aircraft was released and transported to glendale municipal airport, the chip detector plugs were removed. Both upper rt and lower lt (power), chip plugs were full of metal flakes and sludge, well in excess of the allowable limits as noted in the maintenance manual. There were no other indications noted.

The NTSB and the FAA examined the aircraft and the engine. Once the inlet cowl was taken off, the compressor blades could be seen coated with grey residue, indicative of the compressor seizing. It was at this time that the NTSB and the Bell representative decided to have the engine shipped and torn down at the rolls royce service center in indianapolis, Indiana. The tear-down report will be forwarded to the FAA iic pending completion.

Damage to the helicopter included the following:

Main rotor blade made contact with the vertical fins and tail rotor drive shaft while free-spinning and not under power. Inspections required are; overhauls of the main rotor mast, main rotor hub, swash plate, freewheeling unit, main rotor pitch links, several control tubes, and engine. Inspection of the main rotor blades must also be accomplished. Tailboom, tail rotor drive shaft, vertical fins and main rotor driveshaft have to be replaced.