Bell 206 accident near Sevierville, Tennessee, February 15, 2015
On February 15, 2015 at about 8:00 pm local time, a 1983 Bell 206 (helicopter), registered N3176L, was substantially damaged in an accident during takeoff near Sevierville, Tennessee (Sixty Six airport). It was an aerial observation flight under general aviation rules (Part 91). No one was hurt; 6 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
An uncontained engine failure, which resulted from insufficient lubrication of the No. 4 bearing due to carbon buildup on the filter screen of the bearing's oil supply nozzle.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- February 15, 2015 · about 8:00 pm local time
- Place
- Sevierville, Tennessee · Sixty Six · map
- Type
- Accident
- Injuries
- No one was hurt; 6 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Bell 206 L1, built 1983 · all 206s on the register
- Registration
- N3176L · registry record · serial 45648
- Damage
- Substantial damage
- Flight
- Aerial observation flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The commercial pilot was departing in the helicopter for a local aerial sightseeing flight with five passengers. The engine was operating during the boarding process. After the passengers were seated and had fastened their seat belts, the pilot increased the engine power to 100%, raised the collective, and felt the helicopter shudder. He lowered the collective and looked to make sure all passengers were seated. He raised the collective a second time, again felt the shudder, lowered the collective, and then heard "a loud bang." He subsequently turned off the fuel to shut down the engine. A fire began in the engine compartment, and ground personnel helped evacuate the passengers and extinguish the fire. Multiple fragments of engine turbine section components were found resting in the engine bay, on the ground around the helicopter, and embedded in the bottom surfaces of the main rotor blades. Postaccident examination of the engine revealed that the power turbine shaft had decoupled due to a No. 4 bearing failure. Carbon buildup was found on the filter screen of the No. 4 bearing's oil supply nozzle that partially obstructed oil flow to the bearing and likely resulted in insufficient lubrication of the bearing. The No. 4 bearing inner race spun on the bearing journal instead of remaining stationary as designed. The turbine rotates at extremely high speeds, and the resistance from the failed bearing caused the power turbine pinion splines to decouple, leading to an instantaneous power turbine overspeed. The overspeed led to a third stage turbine disk burst and radial uncontainment of fragmented power turbine components through the exhaust support and airframe. All turbine component fractures were due to overload failure, and there was no evidence of fatigue. Therefore, it is likely that the uncontained engine failure was the result of insufficient lubrication of the No. 4 bearing due to carbon buildup on the oil supply nozzle's filter screen.
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
- Part(s) separation from AC during takeoff
- Uncontained engine failure during takeoff defining event
- Fire/smoke (non-impact)
The NTSB's findings
- cause Aircraft › Aircraft power plant › Engine (turbine/turboprop) › Turbine section › Failure
- cause Aircraft › Aircraft power plant › Engine (turbine/turboprop) › Oil system › Damaged/degraded
- Personnel issues › Task performance › Maintenance › Scheduled/routine maintenance › Maintenance personnel
Pilot
- Certificate: commercial pilot
- Ratings: instrument: helicopter; rotorcraft: helicopter
- Flight time: 1,385 hours in all; 859 in this make and model; 120 in the last 90 days; 40 in the last 30 days; 1,262 as pilot in command
- Last flight review: January 24, 2014
- Medical certificate: Class 2 (without waivers/limitations)
- Seat: rgt
- Injury: no injuries
The aircraft
- Airframe total time: 8,586.1 hours
- Last inspection: annual inspection, February 2, 2015; 13 hours since
- Maximum gross weight: 4,251 lb
- Seats: 6
- Landing gear: fixed
- Engine: Allison 250-C28B (turboshaft); 8,204 hours total
- Fire on the ground
- Operator: Great Smoky Mountain Helicopter Inc
The flight
- Departed from: 6TN3 Sevierville TN at 8:00 pm
- Destination: 6TN3 Sevierville TN
- Flight plan: none
Weather at the time
- Light: daylight
- Wind: from 020° at 7 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 25°F (-4°C), dew point -8°F (-22°C)
- Altimeter: 30.31 inHg
- Observation at 7:55 pm from KGKT, 3 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 | |||
| Passengers | 5 |
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.