Eurocopter AS350B3 accident near Eagle Pass, Texas, September 2, 2002
On September 2, 2002 at about 2:40 pm local time, a Eurocopter AS350B3 (helicopter), registered N747R, was substantially damaged in an accident near Eagle Pass, Texas. It was a business flight under general aviation rules (Part 91). No one was hurt; 1 person was on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The insufficient length of the stepper motor rack inside the HMU, which caused the red "GOV" light to illuminate and the fuel metering valve to freeze causing the engine to automatically engage the manual mode.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- September 2, 2002 · about 2:40 pm local time
- Place
- Eagle Pass, Texas · map
- Type
- Accident
- Injuries
- No one was hurt; 1 person was on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Eurocopter AS350B3 · all AS350B3s on the register
- Registration
- N747R · registry record · serial 3341
- Damage
- Substantial damage
- Flight
- Business flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The commercial pilot was in cruise flight with the auto-pilot engaged when the red "GOV" light illuminated and the audio sounded. He disengaged the autopilot and resumed manual control of engine RPM. As the pilot was turning toward his home base, the pilot re-engaged the autopilot, and the engine RPM began to increase and decrease. The pilot was unable to control the RPM and initiated an autorotation to a field. The helicopter landed hard separating the tail boom and fracturing two arms of the main rotor starflex. The helicopter was equipped with a Turbomeca Ariel 2B series engine, which incorporated an electronic engine control unit (EECU) that electronically controlled engine fuel flow via a Hydromechanical Metering Unit (HMU). Data retrieved from the helicopter's flight data computer revealed that the fuel-metering unit valve had malfunctioned. Further investigation revealed that there had been 10 previous incidents worldwide where there was an internal failure in the EECU, which resulted in a red "GOV" warning light illuminating during flight. When this light illuminated, it caused the fuel metering valve to freeze in the position it had at the time of the detection, and therefore engine power could no longer be automatically controlled. The HMU consisted of a resolver and a stepper motor. The resolver measured/sensed the position of the fuel metering valve. The stepper motor took commands from the EECU and physically moved the metering valve. In automatic mode, the HMU compared the resolver information and stepper motor information, as to the position of the fuel -metering valve. When a cumulative mismatch of greater than 7 degrees occurred, the red "GOV" light illuminated and the pilot had to revert to manual mode for throttle operation. Further examination of the Hydromechanical Metering Unit (HMU) revealed that the stepper motor rack was too short and needed to be lengthened.
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
Pilot
- Certificate: commercial pilot, private
- Ratings: multi-engine land; single-engine land; instrument: airplane; rotorcraft: helicopter
- Flight time: 3,398 hours in all; 255 in this make and model; 99 in the last 90 days; 35 in the last 30 days; 1,993 as pilot in command
- Last flight review: February 7, 2002
- Medical certificate: Class 2 (valid medical--w/ waivers/lim.)
- Seat: rgt
- Injury: no injuries
The aircraft
- Airframe total time: 401.5 hours
- Last inspection: 100-hour inspection, August 29, 2002; 5.8 hours since
- Maximum gross weight: 4,961 lb
- Seats: 6
- Landing gear: fixed
- Engine: Turbomeca Arriel 2B (turboshaft); 0 hours total
The flight
- Departed from: DRT Del Rio TX
- Destination: Encinal TX
- Flight plan: none
Weather at the time
- Light: daylight
- Wind: from 135° at 10 knots, gusting 10
- Visibility: 20 statute miles
- Sky: scat at 5,000 ft
- Temperature: 95°F (35°C), dew point 0°F (-18°C)
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 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.
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.