Bell 47D1 accident near Ahwahnee, California, September 27, 2011
On September 27, 2011 at about 5:30 pm local time, a Bell 47D1 (helicopter), registered N9158R, was substantially damaged in an accident during landing near Ahwahnee, California. It was a personal flight under general aviation rules (Part 91). 1 person was seriously injured and 1 person had minor injuries. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The pilot’s failure to maintain adequate main rotor rpm during the landing approach, which resulted in a loss of control.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- September 27, 2011 · about 5:30 pm local time
- Place
- Ahwahnee, California · map
- Type
- Accident
- Injuries
- 1 person was seriously injured and 1 person had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Bell 47D1 · all 47D1s on the register
- Registration
- N9158R · registry record · serial 455
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
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.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
What happened, in order
- Loss of control in flight during landing defining event
- Collision with terrain or object (not controlled flight into terrain) during landing
The NTSB's findings
- cause Aircraft › Aircraft oper/perf/capability › Performance/control parameters › Prop/rotor parameters › Not attained/maintained
- cause Personnel issues › Task performance › Use of equip/info › Aircraft control › Pilot
- Environmental issues › Physical environment › Object/animal/substance › Tree(s) › Contributed to outcome
Pilot
- Certificate: private
- Ratings: rotorcraft: helicopter
- Medical certificate: Class 3 (without waivers/limitations)
- Seat: left
- Injury: serious injuries
The aircraft
- Airframe total time: 4,831 hours
- Last inspection: annual inspection, June 14, 2011
- Maximum gross weight: 2,200 lb
- Seats: 3
- Landing gear: fixed
- Engine: Franklin 6V4-178-B32 (piston); 0 hours total
The flight
- Departed from: Ahwahnee CA at 5:20 pm
- Destination: Ahwahnee CA
- Flight plan: none
Weather at the time
- Light: daylight
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 72°F (22°C), dew point 52°F (11°C)
- Altimeter: 30.04 inHg
- Observation at 4:53 pm from KMAE, 33 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 | |||
| Passengers | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Other NTSB records under N9158R the same tail number, which may have belonged to a different aircraft at the time
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.