Civil Aviation Authority of New Zealand
12 September 2006

MEDIA RELEASE

For further information contact:
Bill Sommer
Tel: 0-4-560 9411 or 0-27-546 8216

The accident report can be viewed on the CAA web site, www.caa.govt.nz, under Accidents & incidents - Fatal accident reports - 05/2733 ZK-HVN, Murchison

or use this link:
http://www.caa.govt.nz/Accident_Reports/ZK-HVN_Fatal_26Aug2005.pdf

Begins

Fatal Accident Report: ZK-HVN, Murchison, 26 August 2005

A Civil Aviation Authority safety investigation has concluded that the failure of the tail rotor drive shaft that had been incorrectly assembled caused a Robinson R22 helicopter, ZK-HVN, to crash inverted in a paddock near Murchison on 26 August 2005, killing the pilot and seriously injuring the passenger.

The helicopter had been stored at the premises of a maintenance organisation since April 2005 to undergo a main rotor blade replacement, a 100 hour/annual inspection and defect rectification.

On the day of the accident, once satisfied that the helicopter was operating correctly, the pilot departed from the maintenance organisation for the flight to his home base. He flew for approximately 120 minutes, arriving at his home base at 1515 hours.

Later that afternoon a friend of the family visited the household and as the weather was favourable for flying and the pilot was eager to use his helicopter, he invited his friend to be the shooter on a short deer hunting flight. The 45 minute flight was without incident and after unsuccessfully pursuing some deer the pilot elected to return home. During the approach to land the helicopter was seen to yaw rapidly to the right and continue to rotate uncontrollably before crashing close to the intended landing site.

After a detailed scene examination, the wreckage was recovered to a maintenance facility where a detailed examination was conducted.

Examination of the aft coupling of the tail rotor drive shaft revealed that it was assembled incorrectly. One or more of the unsupervised and unlicensed maintenance personnel had incorrectly bolted the aft flange of the tail rotor drive shaft directly to the input yoke of the tail rotor gearbox which resulted in failure of the tail rotor drive shaft.

The risk taking behaviour exhibited during the maintenance of ZK-HVN allowed a critical defect to be built in to the helicopter's tail rotor drive system andthen allowed it to remain undetected.

Compliance with the applicable Civil Aviation Rules and the associated Advisory Circular would have prevented this accident. The compliance failures noted were:

  • The certifying licensed aircraft maintenance engineer should not have signed the release to service statement as he was not personally and physically present to directly supervise at critical stages during the maintenance.
  • The certifying licensed aircraft maintenance engineer should not have signed the release to service statement without ensuring that the duplicate inspection had been completed and correctly certified, and an adequate physical check had been carried out by the second person.
  • The unlicensed maintenance personnel should not have assembled the tail rotor drive shaft without being directly supervised by the certifying licensed aircraft maintenance engineer.
  • The assisting licensed aircraft maintenance engineer, though not rated on the helicopter, would have known that the certifying licensed aircraft maintenance engineer was required to have been present to directly supervise the reassembly of the helicopter at critical stages during the maintenance. He should have intervened and brought this to the attention of the CEO or the Civil Aviation Authority.
  • The CEO of the maintenance organisation had been made aware of the requirements for direct supervision and should have halted the critical maintenance tasks until the certifying licensed aircraft maintenance engineer was present to directly supervise the maintenance being performed.

By electing to release the helicopter to service without having taken the required steps to comply with the rules, the certifying licensed aircraft maintenance engineer eliminated multiple layers of safety, prescribed by the Civil Aviation Rules, developed specifically to prevent human error from causing a critical safety occurrence.

In summary, the safety investigation concluded that:

  • ZK-HVN had been issued with a non-terminating airworthiness certificate, which was effectively no longer valid, as the maintenance had not been conducted in accordance with the requirements of Civil Aviation Rule 21.179 (a)(2) which states in part - the airworthiness certificate remains in force provided that maintenance on the aircraft is performed in accordance with Part 91 and Part 43.
  • The certifying licensed aircraft maintenance engineer did not directly supervise the unlicensed personnel as he was required to do during the final assembly of the tail rotor drive shaft.
  • Without supervision, the aft coupling on the tail rotor drive shaft was assembled incorrectly.
  • The certifying licensed aircraft maintenance engineer did not adequately check the work carried out by unlicensed personnel and therefore did not detect the incorrect assembly.
  • A duplicate inspection as required by Civil Aviation Rules, which may have detected the incorrect assembly prior to the release of the helicopter to service, was not correctly completed by the certifying licensed aircraft maintenance engineer.
  • The certifying licensed aircraft maintenance engineer released the aircraft to service when maintenance had clearly not been carried out in accordance with the manufacturer's instructions or the Civil Aviation Rules currently in force.
  • The tail rotor drive shaft failed in flight causing the helicopter to become uncontrollable during the landing phase resulting in the fatal accident.

The CAA has taken action to suspend the licence of the certifying licensed aircraft maintenance engineer and at his request the matter has been placed on hold to give him the opportunity to make submissions following the outcome of investigations by other authorities.

The CAA is considering the suitability of the assisting licensed aircraft maintenance engineer to hold a licence. This is currently on hold pending the outcome of investigations by other authorities.

The CAA is developing a plan for systematic surveillance of Part 43 maintenance providers in the year to July 2007. This action appears in the CAA Business plan for the fiscal year 2006-2007.

The CAA is considering a rule amendment which would require that all aircraft maintenance be performed by appropriately certificated organisations employing full time, appropriately rated and licensed aircraft maintenance engineers. As this is considered to be a significant CAA policy change, it has been tabled for discussion with the relevant sectors of the aviation industry at the next Issue Assessment Group meeting for maintenance issues, provisionally scheduled for late 2006.