On 23 December 2009, a Garlick Helicopters Incorporated TH-1F
helicopter, registered VH-UHD, was engaged in aerial firefighting
operations in the Nangar National Park, New South Wales. At about
200 ft above ground level, the nose of the helicopter unexpectedly
yawed to the right. The pilot made a corrective input on the
tailrotor pedals, but was unable to stop the yaw and the helicopter
began to rotate. The pilot guided the helicopter to a less-timbered
area for an emergency landing. The helicopter descended into the
trees and was seriously damaged. The pilot, the sole occupant, was
seriously injured.
The loss of directional control was due to a structural failure
in the helicopter's tailrotor control system, likely precipitated
by the failure of an attachment bolt.
The investigation identified a safety issue with the maintenance
and operation of ex-military helicopters being used in repetitive
heavy lift operations. In response, on 5 July 2011, the Civil
Aviation Safety Authority published Airworthiness Bulletin 02‑40
Issue 1 to advise operators and maintainers to investigate the
basis for, and the correct implementation of, the continuing
airworthiness requirements of the applicable type certificate data
sheet and incorporated supplemental type certificates, particularly
in regard to the retirement lives of all life-limited
components.
