Bell 407 accident near Telluride, Colorado, May 3, 2014
On May 3, 2014 at about 4:30 pm local time, a 1997 Bell 407 (helicopter), registered N407MH, was substantially damaged in an accident during maneuvering (low-alt flying) near Telluride, Colorado. It was flown under charter and air-taxi rules (Part 135). 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 failure of the power turbine thrust (No. 5) bearing due to overheating as a result of oil starvation, which led to the engine failure. Also causal to the accident was an undocumented repair to the gearbox cover oil delivery tube port during which an insert was threaded into the oil delivery tube port that subsequently restricted the oil flow to the power turbine thrust bearing.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- May 3, 2014 · about 4:30 pm local time
- Place
- Telluride, Colorado · map
- Type
- Accident
- Injuries
- No one was hurt; 3 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Bell 407 NO SERIES, built 1997 · all 407s on the register
- Registration
- N407MH · no longer on the register · serial 53100
- Damage
- Substantial damage
- Flight
- Flight · charter and air-taxi rules (Part 135)
The NTSB's narrative final · quoted from the NTSB record
The commercial pilot and two flight crewmembers were conducting a search and rescue mission for a local sheriff's department in the helicopter. The pilot reported that, after flying five or six lines of the search grid and while in a right turn to begin flying another line of the grid, the engine noise changed. Immediately thereafter and while the helicopter was 200 ft above ground level, the engine chip detector light illuminated, followed by a full authority digital electronic control degrade light. The pilot started to descend toward an open snow-covered meadow for landing, but the engine rpm degraded, so he initiated an autorotation. The helicopter touched down with little forward airspeed and bounced, and the left skid then became caught on an object under the snow. The helicopter rolled onto its left side and then came to rest. A postaccident examination of the engine showed that the engine gas producer and power turbine drive train had continuity, but there was resistance to the gas producer and scraping of the power turbine when rotated. Further examination of the engine revealed that the gearbox cover had been modified by a repair, which included an insert being threaded into the oil delivery tube port. The insert was blocking the oil flow to the power turbine thrust (No. 5) bearing, which resulted in the bearing overheating and failing due to the lack of lubrication and the subsequent engine failure. No records were found regarding any repair to the gearbox cover oil delivery tube port.
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
- Loss of engine power (partial) during maneuvering (low-alt flying) defining event
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
- cause Aircraft › Aircraft power plant › Engine (turbine/turboprop) › Oil system › Incorrect service/maintenance
- Environmental issues › Physical environment › Object/animal/substance › Hidden/submerged object › Contributed to outcome
- Aircraft › Fluids/misc hardware › Fluids › Oil › Not specified
Pilot
- Certificate: commercial pilot
- Ratings: instructor: helicopter; instructor: instrument helicopter; instrument: helicopter; rotorcraft: helicopter
- Flight time: 4,300 hours in all; 740 in this make and model; 42 in the last 30 days
- Last flight review: March 31, 2014
- Medical certificate: Class 2
- Seat: rgt
- Injury: no injuries
The aircraft
- Airframe total time: 10,730.1 hours
- Last inspection: continuous airworthiness programme, April 30, 2014; 6 hours since
- Maximum gross weight: 5,501 lb
- Seats: 4
- Landing gear: fixed
- Engine: Allison 250-C47 (turboshaft); 0 hours total
- Operator: Classic Medical INC
The flight
- Departed from: MOB Moab UT
- Destination: Telluride CO
Weather at the time
- Light: daylight
- Visibility: 20 statute miles
- Sky: clear
- Temperature: 39°F (4°C), dew point 30°F (-1°C)
- Altimeter: 29.90 inHg
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 3 |
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.