Hughes OH-6A accident near Tucson, Arizona, October 25, 2004
On October 25, 2004 at about 9:25 pm local time, a Hughes OH-6A (helicopter), registered N6188L, was destroyed in an accident near Tucson, Arizona. It was a public-use flight under public-use (government) rules. 2 people were seriously injured. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The loss of engine power due to a fatigue fracture of the PC line from the governor to fuel control, resulting from fretting damage induced by excessive vibration, which was due to the failure of maintenance personnel to install the proper bearings in the starter/generator. A contributing factor was the loss of power at low altitude and airspeed (height/velocity limitation) which diminished the possibility of a successful autorotation.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- October 25, 2004 · about 9:25 pm local time
- Place
- Tucson, Arizona · map
- Type
- Accident
- Injuries
- 2 people were seriously injured.
- Weather
- visual conditions (good weather)
- Aircraft
- Hughes OH-6A · all OH-6As on the register
- Registration
- N6188L · no longer on the register · serial 891257
- Damage
- Destroyed
- Flight
- Public-use flight · public-use (government) rules
The NTSB's narrative final · quoted from the NTSB record
The engine spooled down during a law enforcement surveillance flight, and the pilot made a hard forced landing in uneven terrain. The crew was performing surveillance at low altitude above an uneven wash, and the pilot was in slow sideward flight. He pulled the collective to gain altitude and airspeed to make another pass. Then he heard and felt the engine spool down. He said that it quit producing power completely, and he attempted to autorotate to the ground. He said that he had insufficient airspeed and altitude to complete a successful autorotation. The helicopter hit the ground hard in a near level attitude. It bounced backwards, and rotated 45 degrees to the right. Metallurgical examination revealed that the governor tee to fuel control PC line fractured as a result of fatigue. The tubes were bent with contours differing from the original manufactured shape, indicative of handling/assembly damage. Disassembly and inspection of the starter/generator revealed conditions indicative of wear and misassembly, including the wrong bearings being installed, which would cause the unit to operate in an out-of-balance condition and induce vibrations.
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; instrument: helicopter; rotorcraft: helicopter
- Flight time: 5,500 hours in all; 2,940 in this make and model; 65 in the last 90 days; 35 in the last 30 days; 4,700 as pilot in command
- Last flight review: February 1, 2004
- Medical certificate: Class 2 (with waivers/limitations)
- Seat: rgt
- Injury: serious injuries
The aircraft
- Airframe total time: 9,463.3 hours
- Last inspection: approved inspection programme, October 1, 2004; 8.6 hours since
- Maximum gross weight: 2,550 lb
- Seats: 2
- Landing gear: fixed
- Engine: Allison 250-C20B (turboshaft); 0 hours total
- Operator: Tucson Sector Air Operations
The flight
- Departed from: Ajo AZ at 6:00 pm
- Destination: TUS Tucson AZ
Weather at the time
- Light: daylight
- Wind: from 290° at 8 knots
- Visibility: 10 statute miles
- Sky: scat at 8,000 ft
- Temperature: 77°F (25°C), dew point 54°F (12°C)
- Altimeter: 29.79 inHg
- Observation at 8:55 pm from TUS
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| 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.
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.