Robinson R44 N33PX accident near Jackson, Mississippi

Probable cause

The pilot's failure to maintain adequate main rotor rpm, for undetermined reasons.

NTSB analysis

The Federal Aviation Administration (FAA) Flight Standards District Office (FSDO) inspector arranged to conduct a flight as pilot in command (PIC) of the helicopter as part of his participation in the FAA's internal flight currency and proficiency program, informally referred to as the "4040 program." The PIC and the FSDO manager agreed that the flight could also serve as a familiarization flight for a newly-hired, pilot-rated FSDO inspector.

Shortly after takeoff, the PIC informed an air traffic controller that he had changed his plans, and he was cleared as requested to a nearby airport. The helicopter was observed to hover, land, and lift off for a circuit of the traffic pattern. It landed again, and began a second circuit. While on the downwind leg, the helicopter entered a descent that had a rate of approximately 2,400 feet per minute and subsequently impacted trees, terrain, and a house in a residential neighborhood.

The PIC held multiple certificates and ratings, and the vast majority of his experience was in fixed-wing aircraft. He had about 140 hours of helicopter experience, and about 60 hours in Robinson helicopters. The second pilot held multiple certificates and ratings, and had over 4,000 hours of helicopter flight experience. His most recent helicopter piloting experience was about 9 years prior to the accident. Due to certain flight and operational characteristics, the FAA mandated Robinson-specific training for pilots, via Special Federal Aviation Regulation (SFAR) 73. The accident flight was the second pilot's first flight in a Robinson helicopter, and no records of any Robinson-specific training or endorsements, including those required by SFAR 73, were located for him.

The final trajectory of the helicopter was consistent with a main rotor stall that developed when the helicopter was on the downwind leg. Post-accident examination and testing of the helicopter and components, including a full-power run of the engine, did not reveal any evidence of pre-impact failures or malfunctions. The helicopter manufacturer published notices for pilots that stated that main rotor stall due to low rotor rpm could occur rapidly, and at any airspeed, and could make "recovery virtually impossible." Other guidance noted that appropriate pilot response to an impending stall in an airplane was the opposite of the appropriate response for the helicopter, and could result in, or aggravate, rotor stall. The reason for the decay of the main rotor rpm could not be definitively determined.

Text from the NTSB. Open the NTSB docket for ERA09FA497 for the full record.