Probable cause
The pilot’s failure to maintain adequate main rotor rpm during the landing approach, which resulted in a loss of control.
NTSB analysis
The pilot and mechanic were on a local area flight to warm the oil before changing the oil lines. As they returned, the pilot slowed the helicopter and initiated a gradual descent to the landing site. The main rotor rpm decreased. As they continued the descent, the clearance from the trees surrounding the landing area was minimal. The pilot attempted to avoid the trees as he tried to regain main rotor rpm. The helicopter impacted a tree and descended nose down into the terrain. According to the mechanic and pilot, they encountered no mechanical anomalies during the flight.
Text from the NTSB. Open the NTSB docket for WPR11LA469 for the full record.
Event
- Date
- Sep 27, 2011
- Type
- Accident
- Place
- Ahwahnee, California
- Highest injury
- Serious
- Serious injuries
- 1
- Minor injuries
- 1
- Weather
- Visual (VMC)
- Light
- Day
Bell 47D1
- N-number
- N9158R
- Category
- Helicopter
- Damage
- Substantial
- Operating rule
- Part 91 (general aviation)
- Purpose of flight
- Personal
From the NTSB aviation accident database: N-registered aircraft, events since 2008, data through Oct 28, 2026. The file is published monthly, so the latest weeks are incomplete and recent records can change. The official source is the NTSB aviation investigation search. CheckAero is independent and not affiliated with the NTSB.