NTSB Identification: WPR11CA121
14 CFR Part 91: General Aviation
Accident occurred Thursday, February 03, 2011 in Ogden, UT
Probable Cause Approval Date: 06/08/2011
Aircraft: ROBINSON R44, registration: N441TB
Injuries: 2 Uninjured.
NTSB investigators used data provided by various entities, including, but not limited to, the Federal Aviation Administration and/or the operator and did not travel in support of this investigation to prepare this aircraft accident report.
After completing several practice landings and autorotations at the airport, the certified flight instructor (CFI) and student pilot departed for the practice area. The CFI demonstrated straight-in and 180-degree autorotations; the first 180-degree attempt began at 6,000 feet mean sea level and at 55-60 knots. During the second 180-degree attempt, he started about 200 feet lower. The airspeed bled off to about 50 knots during the turn, and the main rotor blades’ rpms began decaying rapidly. About 200 feet above ground level the CFI attempted a power recovery, but the rpms did not increase with an increase in throttle. He unsuccessfully attempted to flair to bring the rpms back before attempting a full down autorotation. He put the helicopter in a level attitude prior to contact with the ground and the helicopter bounced upon initial contact; on the second contact, the right skid dug into the muddy ground and the helicopter rolled onto its right side. The helicopter sustained substantial damage to the airframe and rotor blades. The pilots stated that the helicopter had no mechanical failures or malfunctions prior to the accident.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The certified flight instructor’s failure to maintain adequate main rotor blade rpm during a practice autorotation, resulting in a hard landing and rollover. Full narrative available
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