Hughes 369D N633WA

Summary

On 26 June 2003 at about 23:15 local time, a Hughes 369D registered N633WA was involved in an accident near Kualapuu, Hawaii, United States. One person was on board and one was seriously injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

26 June 2003 at 23:15

Classification

Accident

Location

Kualapuu, Hawaii, United States

Coordinates

21.1167, -157.1000

Aircraft

Hughes 369D

Registration

N633WA

Category

Helicopter

Engines

1

Operator

Not recorded

Operating rule

Part 133: Rotorcraft Ext. Load

Purpose of flight

Other Work Use

Phase of flight

Not recorded

Route

Molokai → Unknown

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

LAX03LA212

1 person was seriously injured.

the total loss of engine power resulting from a fatigue failure of the 3rd stage turbine wheel airfoils. The reason for the airfoil's fatigue failure could not be determined.

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

Read the full NTSB narrative

The pilot made a hard landing in the single-engine helicopter after experiencing a loss of engine power at 40 knots and 150 feet agl. The pilot was conducting fire suppression operations and had maneuvered the helicopter over a pond to pickup water. He heard a loud bang and looked over his shoulder to observe white smoke coming from the engine exhaust. The pilot entered an autorotation and began a flare at 50 feet agl with a high rate of descent. The helicopter impacted the ground and a fire ignited. The engine accumulated approximately 1,043 hours since undergoing a modification to its turbine section (approximately 707 hours short of its recommended overhaul time). The modification was part of a commercial engine bulletin, which converted the engines to obtain better performance "from the improved power turbine air flow characteristics." The conversion included a replacement of the 3rd and 4th stage turbine nozzles and wheels. A post-accident examination of the engine revealed the airfoils on the 3rd stage wheel failed as a result of fatigue cracking that originated at the airfoil's trailing edge and progressed toward the leading edge of the blades. All of the 3rd stage airfoils displayed some form of cracking near the airfoil roots at their trailing edges. A number of the cracks were attributed to fatigue propagation; however, some were attributed to overload. The 3rd stage turbine wheel and airfoils met the manufacturer's specifications and no material flaws or defects were noted at the fatigue cracking origins. The reason for the fatigue cracking and subsequent failures could not be determined.

Quoted verbatim from the NTSB record.