Bell 407 N407MH

Summary

On 3 May 2014 at about 16:30 local time, a Bell 407 registered N407MH, operated by Classic Medical Inc, was involved in an accident near Telluride, Colorado, United States. 3 people were on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

3 May 2014 at 16:30

Classification

Accident

Location

Telluride, Colorado, United States

Coordinates

37.8350, -107.8817

Aircraft

Bell 407

Registration

N407MH

Category

Helicopter

Year built

1997

Engines

1

Operator

Classic Medical Inc

Operating rule

Part 135: Air Taxi & Commuter

Phase of flight

Not recorded

Route

Moab → Telluride

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

CEN14FA232

Nobody was injured.

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.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

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.

Quoted verbatim from the NTSB record.