Kaman HH-43B N556D

Summary

On 26 June 2001 at about 15:45 local time, a Kaman HH-43B registered N556D, operated by Precision Helicopters LLC., was involved in an accident near Mullan, Idaho, United States. One person was on board and one had minor injuries. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

26 June 2001 at 15:45

Classification

Accident

Location

Mullan, Idaho, United States

Coordinates

47.4592, -115.7402

Aircraft

Kaman HH-43B

Registration

N556D

Category

Helicopter

Engines

1

Operator

Precision Helicopters LLC.

Operating rule

Part 133: Rotorcraft Ext. Load

Purpose of flight

Other Work Use

Phase of flight

Not recorded

Route

Mullan → Unknown

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

SEA01LA121

1 person had minor injuries.

The development of multiple fatigue cracks which ultimately resulted in the fracture of the 1st stage gas producer turbine rotor sealing disc. Factors contributing to the accident were mountainous/hilly and unsuitable terrain conditions.

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

Read the full NTSB narrative

The pilot was preparing to lift a load of logs from a 150-foot hover in the Kaman HH-43B helicopter when a total loss of power occurred. He transitioned into an autorotation colliding with the steeply sloped, tree covered terrain. A partial disassembly of the ex-military Lycoming T53-L-13B turboshaft engine revealed that the 1st stage gas producer turbine rotor sealing disc was fractured and had broken into three approximately equal sized segments. Metallurgical examination of the disc fragments revealed fatigue cracks through three of the six cooling holes, and examination of the fracture faces for all three cooling holes by scanning electron microscope revealed multiple fatigue striations at each fracture face.

Quoted verbatim from the NTSB record.