Bell 47D1 accident near San Martin, California, October 31, 2004
On October 31, 2004 at about 5:22 pm local time, a Bell 47D1 (helicopter), registered N903B, was substantially damaged in an accident near San Martin, California (South County Airport Of Santa). It was an instructional flight under general aviation rules (Part 91). No one was hurt; 2 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
A loss of power for undetermined reasons.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- October 31, 2004 · about 5:22 pm local time
- Place
- San Martin, California · South County Airport Of Santa · map
- Type
- Accident
- Injuries
- No one was hurt; 2 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Bell 47D1 · all 47D1s on the register
- Registration
- N903B · registry record · serial 847
- Damage
- Substantial damage
- Flight
- Instructional flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The helicopter experienced a loss of engine power and rolled over during an attempted autorotation to a soft, muddy field. The helicopter departed for a 22-nautical mile training flight with 10 gallons of fuel remaining in the 28-gallon fuel tank. While en route, both the certified flight instructor (CFI) and student pilot noted that an unusually high application of carburetor heat was required to keep the inlet temperature needle within the normal range. With the intention of entering the traffic pattern at the destination airport, the student pilot initiated a descent and maneuvered the helicopter in a right turn. With the helicopter configured in the right turn, about 500 feet above ground level (agl), the engine experienced a momentary power interruption and subsequently stopped. The student pilot executed an autorotation and the helicopter touched down in a crop field. The right skid dug into the soft muddy field, resulting in the helicopter rotating around the skid and coming to rest on its right side. The fuel tank contained about 5 gallons of fuel just prior to the accident. Due to the orientation of the fuel outlet port inside the fuel tank, the helicopter is susceptible to unporting with low quantities of fuel present during maneuvers. With the outlet located on the left side of the tank, when a helicopter is in a right turn with minimal fuel onboard, the outlet can intake air resulting in fuel starvation to the engine. According to a standard reference icing probability chart, the atmospheric conditions present at the time of the accident were in the range considered favorable for carburetor ice formation.
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
Flight instructor
- Certificate: flight instructor, commercial pilot
- Ratings: multi-engine land; single-engine land; single-engine sea; instructor: airplane multi-engine; instructor: airplane single-engine; instructor: helicopter; instructor: instrument airplane; instrument: airplane; instrument: helicopter; rotorcraft: helicopter
- Flight time: 4,500 hours in all; 75 in this make and model; 70 in the last 90 days; 20 in the last 30 days; 4,300 as pilot in command; 800 on instruments
- Last flight review: June 1, 2004
- Medical certificate: Class 1 (valid medical--w/ waivers/lim.)
- Seat: rgt
- Injury: no injuries
Dual student
- Certificate: student
- Flight time: 170 hours in all; 75 in this make and model; 5 in the last 90 days; 2 in the last 30 days
- Medical certificate: Class 2
- Seat: left
- Injury: no injuries
The aircraft
- Airframe total time: 4,827.1 hours
- Last inspection: annual inspection, March 24, 2004; 5 hours since
- Maximum gross weight: 2,350 lb
- Seats: 2
- Landing gear: fixed
- Engine: Franklin 6V-335-5B (piston); 0 hours total
The flight
- Departed from: RHV San Jose CA at 5:10 pm
- Destination: E16 San Martin CA
- Flight plan: none
Weather at the time
- Light: daylight
- Wind: from 200° at 4 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 61°F (16°C), dew point 54°F (12°C)
- Altimeter: 30.20 inHg
- Observation at 5:53 pm from WVI, 13 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 2 |
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 N903B 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.