Incident Overview
On May 10, 2012, at approximately 1015 mountain daylight time, a Robinson R44 II helicopter, registration N7523S, performed an autorotation following a loss of engine power near Grants, New Mexico. The flight was conducted under 14 Code of Federal Regulations Part 91 as a positioning flight, operated by iPrerogative Inc. of Washington, Utah. Visual meteorological conditions prevailed, and the flight operated on a visual flight rules flight plan. The helicopter had departed the Albuquerque International Airport (KABQ), Albuquerque, New Mexico, about 0900, and was destined for Page Municipal Airport (KPGA), Page, Arizona.
Flight Crew and Injuries
The helicopter was occupied by a certificated flight instructor (CFI) and a commercial pilot. Neither occupant was injured.
Sequence of Events
According to a statement from the CFI, while cruising over mountainous terrain at 10,000 feet mean sea level (msl), the CFI slowed the helicopter to 70 knots and initiated a practice autorotation to maintain autorotation proficiency. The pilot reported checking 80 percent engine rpm at least twice during the maneuver. At approximately 9,200 feet msl (about 600 feet above ground level), the CFI attempted to restore engine power, but the engine had ceased producing power, as verified by the engine tachometer. The pilot continued the autorotation, lined up with the best available landing area, and landed. Upon touchdown, the helicopter’s main rotor blade contacted the tail boom, severing it. Substantial damage was sustained to the main rotor blades, tail boom, and tail rotor blades.
Postaccident Examination
A postaccident engine run was conducted by the National Transportation Safety Board and a technical representative from Lycoming Engines. The engine started and ran for several minutes; however, it occasionally ran rough at idle power with a full rich mixture setting. Leaning the fuel mixture via the cockpit mixture control improved engine performance. The density altitude at the time of the engine run was approximately 8,100 feet.
Maintenance History
A review of maintenance records revealed that maintenance work was performed in Florida at an altitude of 100 feet mean sea level. Any adjustment to the fuel control unit, which sets the idle mixture, would have been set at this altitude by maintenance personnel.