What happened
On 22 September 1966, a Vickers Viscount 832, registered VH-RMI, was operating a scheduled passenger service from Mt. Isa to Longreach in Queensland. The flight, carrying twenty passengers and four crew members, departed at 12:08 AEST and climbed to Flight Level 175.
At approximately 12:52, the crew notified the Longreach Flight Service Unit that they were performing an emergency descent. Shortly after, the flight crew reported fire warnings involving engines number one and two, noting that while one warning had cleared, a propeller could not be feathered. By 12:59, via a third-party aircraft, the crew communicated that a visible fire was present in the number two engine and that they were diverting to Winton.
At 13:03, observers near Winton spotted black smoke to the west of the town. It was later determined that VH-RMI had crashed into light timber on level ground, roughly 131 miles short of the Winton aerodrome. The impact caused the aircraft to disintegrate, and there were 24 fatalities.
Findings
The investigation concluded that the accident was caused by a fire originating in the number two cabin blower. This fire spread through the engine nacelle and wheel bay into the number two fuel tank, which weakened the main spar upper boom.
Specifically, a rotor break-up within the blower created an out-of-balance condition. The resulting vibrations caused the oil metering unit to detach from its cover. As the detached unit continued to be driven, it caused metal-to-metal contact and extreme heat, which ignited the lubricating oil. This fire in the fuel tank led to the structural failure of the port wing between the two engines, causing the aircraft to crash.