• A Google Earth image annoted by the ATSB showing the flight path of VH-UZB from Pimpama airfield. (ATSB)
    A Google Earth image annoted by the ATSB showing the flight path of VH-UZB from Pimpama airfield. (ATSB)

The Australian Transport Safety Bureau (ATSB) last week released the final investigation report into the fatal crash of a Tiger Moth at Pimpama, Queensland, in December 2015.

Tiger Moth VH-UZB was on an adventure flight when the engine partially failed at 200 feet soon after take-off, crashing into trees during an attempt to return to the airport. The pilot was severely injured and the passenger was killed in the crash.

According to the ATSB report, the pilot lost control of the aircraft during the turn back to the airport, resulting in a stall and spin from which the aircraft didn't recover before impacting the ground.

"Shortly after take-off, the aircraft had a partial engine power loss," the ATSB has reported. "In response, the pilot elected to return to the landing area. During the subsequent left turn, the aircraft stalled and entered a spin, at a height from which recovery was not possible before the collision with terrain.

"The ATSB established that the pilot was appropriately qualified to be conducting the flight. The pilot had limited experience on the aircraft type, however, it was not possible to determine whether that contributed to the development of the accident as the management of this emergency would have challenged most pilots."

The ATSB was unable to determine why the partial power loss occurred, but found a crack in the carburettor float varnish and an anomaly with a valve clearance, neither of which is thought to have been the cause.

Analysis of an audio track from a video supported the pilot's contention that the engine noise reduced at around 200 feet AGL.

"A partial engine power loss presents a more complex scenario to a pilot than a complete engine power loss," the ATSB states. "Following a complete engine failure, a forced landing is the only option whereas in a partial power loss, pilots are faced with making the difficult decision of whether to continue flight or to conduct an immediate forced landing.

"ATSB research found that the two-thirds of pilots who experience a partial power loss after take-off elect to return to the landing area. The pilot of VH‑UZB ... similarly elected to return to the airfield."

The full investigation report is on the ATSB website.

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