Aviation safety investigations & reports

Driveshaft failure and hard landing involving Overseas Aircraft Support UH-1H helicopter, VH-OXI, near Crawford River, NSW, on 7 December 2019

Investigation number:
AO-2019-070
Status: Completed
Investigation completed
Phase: Final report: Dissemination Read more information on this investigation phase

Final Report

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What happened

On 7 December 2019, at about 1034 Eastern Daylight-saving Time, the pilot of an Overseas Aircraft Support UH-1H helicopter (formally known as Bell UH-1H or ‘Huey’ helicopter), registered VH-OXI, experienced a main driveshaft failure and hard landing near Crawford River, New South Wales, while engaged in fire control aerial work. The pilot was not injured and the helicopter was substantially damaged.

What the ATSB found

The ATSB found that the pilot elected to abort the fire control aerial work and conduct a precautionary landing as a result of the failure of the driveshaft. While attempting to land, the pilot experienced an uncontrollable yaw to the right, resulting in a hard landing and substantial damage to the helicopter when the main rotor blades struck the ground and forcibly ejected the main gearbox, mast, rotors and KAflex® driveshaft from the airframe.

The helicopter’s KAflex® driveshaft, which transmits power from the engine to the main gearbox, failed due to a fatigue crack prior to the hard landing. The driveshaft assembly was missing five washers, which increased the risk of a driveshaft failure.

What's been done as a result

Following the accident, the Civil Aviation Safety Authority emailed Australian operators of UH‑1 helicopters a brief on the accident, which included a copy of a previously issued (2007) airworthiness bulletin on the subject of pre-flight inspection requirements for the KAflex® driveshaft. The requirements included checking the condition of all driveshaft hardware in addition to the pre-existing inspection requirements.

As a result of this occurrence, the helicopter operator replaced the KAflex® driveshaft on their other UH-1H helicopter with a new driveshaft. For the new driveshaft, they implemented a maintenance routine to monitor the hours flown and time-in-service, and included a scheduled retirement time of 5,000 hours.

Safety message

In 2018, the driveshaft manufacturer provided a position paper to the United States Federal Aviation Administration, which recommended that driveshafts with the same part number as the accident helicopter should be replaced at 5,000-hours service, or, if the time-in-service could not be determined, removed and replaced. Any legacy driveshafts of the accident part number SKCP2281-103 can be sent to the manufacturer for modification to a new ‘safety of flight’ part number SKCP3303-1.

This accident highlighted the importance of pilots operating helicopters in the low-level environment to respond to the early symptoms of a problem immediately, and to be prepared to commit to a precautionary landing before the condition deteriorates to the point of a forced landing. In this case, the pilot responded without delay and was able to reach a safe landing site before a catastrophic failure of the driveshaft occurred.

Download final report
[Download  PDF: 700KB]
 
 
 

The investigation

General details
Date: 07 December 2019   Investigation status: Completed  
Time: 1035 EDT   Investigation level: Short - click for an explanation of investigation levels  
Location   (show map): near Crawford River (54 km north of Williamtown)   Investigation phase: Final report: Dissemination  
State: New South Wales   Occurrence type: Transmission and gearbox  
Release date: 16 July 2020   Occurrence category: Accident  
Report status: Final   Highest injury level: None  

Aircraft details

Aircraft details
Aircraft manufacturer OAS  
Aircraft model OAS Parts UH-1H (formally known as a 'Huey')  
Aircraft registration VH-OXI  
Serial number 64-13497  
Operator Touchdown Helicopters  
Type of operation Aerial Work  
Sector Helicopter  
Damage to aircraft Substantial  
Departure point Wauchope, New South Wales  
Destination Wauchope, New South Wales  
Last update 16 July 2020