Bell 407 N534MT

Summary

On 29 December 2012 at about 17:48 local time, a Bell 407 registered N534MT, operated by MED Trans Corp, was involved in an accident near Big Lake, Texas, United States. 4 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

29 December 2012 at 17:48

Classification

Accident

Location

Big Lake, Texas, United States

Nearest airport

Reagan County Airport (E41)

Coordinates

31.1950, -101.4708

Aircraft

Bell 407

Registration

N534MT

Category

Helicopter

Engines

1

Operator

MED Trans Corp

Operating rule

Part 135: Air Taxi & Commuter

Phase of flight

Not recorded

Route

Fort Stockton → San Angelo

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

CEN13LA119

Nobody was injured.

The loss of engine power due to the fatigue failure of the outer combustion case at the fuel nozzle port. Contributing to the accident was the operator’s failure to conduct the recommended routine inspections of the outer combustion case.

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

Read the full NTSB narrative

The pilot reported that, while in cruise flight, the helicopter suddenly yawed 10 degrees right. He was able to control the yaw and subsequently heard an alarm and observed an rpm warning light. After silencing the alarm, he noticed a 2- to 3-percent decrease in rpm for the engine and rotor. As the pilot began to scan the flight controls and instruments, he saw the "check instrument segment" illuminate, and the measured gas temperature gauge begin to flash and display a reading of "E 920." The pilot stated that all of the other engine indications were in the normal operating ranges. During the precautionary landing, when the helicopter was about 10 to 15 ft above ground level and 20 knots, the engine "quit." The pilot responded by moving the throttle to idle and increasing the collective pitch. The helicopter subsequently hit the ground hard, which resulted in substantial damage to the tailboom. During the postaccident examination of the engine, three fractures were found in the outer combustion case at the fuel nozzle port. Two of the three fractures originated at the intersection of the circumferential weld that joined the reinforcing ring to the main skin and exhibited heat tinting consistent with the cracks having been open during engine operation. The third fracture ran adjacent to the reinforcing ring to the main skin interface. All three fractures exhibited signatures consistent with high-cycle fatigue. The investigation determined that the operator was not conducting the manufacturer-recommended postflight and scheduled maintenance inspections of the outer combustion case; these cracks would likely have been detected during such inspections.

Quoted verbatim from the NTSB record.