Aerospatiale AS 355F1 N101MZ

Summary

On 3 March 2012 at about 03:40 local time, a Aerospatiale AS 355F1 registered N101MZ, operated by TGR Helicopters, was involved in an accident near Makakilo City, Hawaii, United States. One person was 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 March 2012 at 03:40

Classification

Accident

Location

Makakilo City, Hawaii, United States

Coordinates

21.3401, -158.0802

Aircraft

Aerospatiale AS 355F1

Registration

N101MZ

Category

Helicopter

Engines

2

Operator

TGR Helicopters

Operating rule

Part 133: Rotorcraft Ext. Load

Purpose of flight

External Load

Phase of flight

Not recorded

Route

Makakilo City → Makakilo City

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR12LA125

Nobody was injured.

A partial loss of engine power while maneuvering over rough/uneven terrain that was precipitated by the failure of a 3rd stage turbine blade as a result of high-cycle fatigue.

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

Read the full NTSB narrative

During external load operations, the right (No. 2) engine experienced a loss of engine power; the associated engine chip light illuminated. The pilot executed a running landing to a nearby landing zone. During the landing, the helicopter encountered rough terrain, which resulted in deformation of the tail boom skin. Postaccident examination of the No. 2 engine revealed that a turbine blade had separated from the 3rd stage turbine wheel. Metallurgical examination of the blade determined that it had failed as a result of high-cycle fatigue probably due to an intermittent vibratory state. The engine manufacturer issued a service bulletin in 2006 and a revised bulletin in 2009 that systematically removed the 3rd stage turbine wheel that was susceptible to this failure mode from the fleet of Model 250 Series II engines. The service bulletin required that the 3rd stage turbine wheel must be replaced at overhaul or if the helicopter experienced an one-engine inoperable (OEI) condition. The turbine wheel had not been replaced, and it could not be determined if the helicopter had experienced an OEI condition.

Quoted verbatim from the NTSB record.