Bell UH-1H Iroquois ZK-HJH, in-flight break-up, Taumarunui, 4 June 2001
Status
Closed
Occurrence Date
Report Publication Date
Jurisdiction
NZ
Legacy Inquiry Number
01-005R
On Monday 4 June 2001 at about 1715, ZK-HJH, a Bell UH-1H Iroquois helicopter, was approaching Taumarunui when it was seen to enter a turn and fall to the ground, killing the 3 occupants. The helicopter was observed to break up before it hit the ground.
This report summarises the results of a resumed investigation of the event and supersedes the original report (Report 01 005).
The investigation was resumed because there was some new and material evidence from 2 other UH 1 helicopter accidents that could have affected the conclusions in the original report. The findings and re analysis of the accident sequence and its causal factors are based primarily upon evidence found during the resumed investigation. Only the new findings and how they affected the original conclusions are discussed. Many of the original findings remain valid, and text from the original report that is valid is included in this report.
After considerable component and metallurgical testing and examination of all the available evidence, the resumed investigation could not support the original theory that the accident sequence was probably caused by the tail rotor crosshead coming loose, because of incorrect maintenance.
The resumed investigation found that a bent tail rotor blade pitch link and its subsequent fatigue failure during the accident flight brought about a loss of control and in flight break up of the helicopter. The link had been bent earlier at some point during the accident flight, which allowed it to crack and eventually fail from bending fatigue. The reason the link was bent could not be determined.
Safety issues concerning the operation and airworthiness of ex-military aircraft were identified.
Safety actions by the Civil Aviation Authority and safety recommendations made to the Director of Civil Aviation address these issues.
This report summarises the results of a resumed investigation of the event and supersedes the original report (Report 01 005).
The investigation was resumed because there was some new and material evidence from 2 other UH 1 helicopter accidents that could have affected the conclusions in the original report. The findings and re analysis of the accident sequence and its causal factors are based primarily upon evidence found during the resumed investigation. Only the new findings and how they affected the original conclusions are discussed. Many of the original findings remain valid, and text from the original report that is valid is included in this report.
After considerable component and metallurgical testing and examination of all the available evidence, the resumed investigation could not support the original theory that the accident sequence was probably caused by the tail rotor crosshead coming loose, because of incorrect maintenance.
The resumed investigation found that a bent tail rotor blade pitch link and its subsequent fatigue failure during the accident flight brought about a loss of control and in flight break up of the helicopter. The link had been bent earlier at some point during the accident flight, which allowed it to crack and eventually fail from bending fatigue. The reason the link was bent could not be determined.
Safety issues concerning the operation and airworthiness of ex-military aircraft were identified.
Safety actions by the Civil Aviation Authority and safety recommendations made to the Director of Civil Aviation address these issues.
Location
Taumarunui (-38.861712,175.346582) [may be approximate]