Bell BH 206L-3 accident near Brownwood, Texas, November 26, 2006
On November 26, 2006 at about 11:30 pm local time, a Bell BH 206L-3 (helicopter), registered N805SB, was substantially damaged in an accident near Brownwood, Texas (None airport). It was a positioning flight under general aviation rules (Part 91). No one was hurt; 3 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The fracture of the turbine-to-compressor coupling and subsequent overspeed failure of the first stage turbine wheel as result of the improper re-assembly of the engine by maintenance personnel. A contributing factor was the lack of suitable terrain for the forced landing.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- November 26, 2006 · about 11:30 pm local time
- Place
- Brownwood, Texas · None · map
- Type
- Accident
- Injuries
- No one was hurt; 3 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Bell BH 206L-3
- Registration
- N805SB · registry record · serial 51192
- Damage
- Substantial damage
- Flight
- Positioning flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The helicopter pilot experienced a sudden "explosion" followed by an uncommanded left yaw while initiating an approach. During the autorotation the pilot was forced to increase collective pitch in order to clear a berm resulting in a loss of main rotor RPM. The helicopter landed hard and remained in the upright position. A review of the turbine engine's maintenance records and work orders revealed the engine had been repaired and inspected in December 2005 for "a sudden stoppage." At that time, the compressor, gearbox, and turbine were replaced. A teardown examination of the engine revealed that the aft end of the turbine-to-compressor coupling had fractured in the region where it mated with the turbine splined adapter. The coupling fracture resulted in a loss of continuity in the N1 drive train and an overspeed failure of the first stage turbine wheel. Metallurgical examination of the fracture surfaces of the remnants of the first stage turbine wheel revealed there was no fatigue fractures. Examination of the splines in the aft end of the coupling and on the pieces from the fractured section revealed fretting and a fractured spline tip in the area of contact with the turbine spline adapter. There was non-uniform wear on 16 consecutive external splines on the turbine splined adapter and there was also non-uniform wear of the splines in the area where the adapter mated with the aft end of the turbine-to-compressor coupling. When the engine was disassembled, there was a discrepancy noted between the thickness of the shims (used for alignment of the gas producer and power turbine drive trains) on the mounting pad between the exhaust collector support and the accessory gearbox than what had been entered in the engine logbook or what was etched on the exhaust collector support. In addition, the balance marks on the spur adapter gear shaft and the turbine-to-compressor coupling were not aligned. According to the Rolls Royce 250-C30 series Overhaul Manual, the balance marks were required to be aligned during re-assembly of the engine. The Overhaul Manual also stated that the cracks found on the vertical fire shield could have been as a result of "abnormally high engine vibration."
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: airline transport pilot, flight instructor, commercial pilot
- Ratings: single-engine land; instructor: helicopter; instrument: airplane; instrument: helicopter; rotorcraft: helicopter
- Flight time: 6,845 hours in all; 2,181 in this make and model; 64 in the last 90 days; 16 in the last 30 days; 4,889 as pilot in command
- Last flight review: June 1, 2006
- Medical certificate: Class 2 (with waivers/limitations)
- Seat: frt
- Injury: no injuries
The aircraft
- Airframe total time: 10,604.8 hours
- Last inspection: approved inspection programme, October 1, 2006
- Maximum gross weight: 4,150 lb
- Seats: 4
- Landing gear: fixed
- Engine: Rolls-Royce 250-C30P (turboshaft); 0 hours total
- Fire on the ground
The flight
- Departed from: ABI Abilene TX at 10:50 pm
- Destination: Brownwood TX
Weather at the time
- Light: daylight
- Wind: from 160° at 8 knots
- Visibility: 10 statute miles
- Sky: broken clouds at 6,000 ft; a few clouds at 4,300 ft
- Temperature: 70°F (21°C), dew point 55°F (13°C)
- Altimeter: 30.02 inHg
- Observation at 11:25 pm from BWD, 3 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 | |||
| Passengers | 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.
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.