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ATSB releases 2nd interim report on in-flight pitch disconnect incident involving ATR-72
5 May 2017

The Australian Transport Safety Bureau (ATSB) released its second interim report into an incident involving a Virgin Australia Regional Airlines ATR 72 aircraft near Sydney on 20 February 2014.

During a flight from Canberra to Sydney, the aircraft sustained a ‘pitch disconnect’ while descending into Sydney. The pitch disconnect occurred when the two flight crew attempted to slow the aircraft down and inadvertently applied opposing control inputs (one pilot pushed the control at the same time the other pilot pulled), and resulted in significant damage to the aircraft’s tail structure.

On 15 June 2016 the ATSB released an interim investigation report that contained the following safety issue:
Inadvertent application of opposing pitch control inputs by flight crew can activate the pitch uncoupling mechanism which, in certain high-energy situations, can result in catastrophic damage to the aircraft structure before crews are able to react.

While this issue focussed on the potential for catastrophic damage during inadvertent activation of the pitch uncoupling mechanism (PUM) from opposing dual control inputs, additional investigation identified that the inherent behaviour of the elevator control system design could potentially result in an ultimate load exceedance from the deliberate activation of the PUM to overcome a jam. Based on the results of this additional investigation, the ATSB made the following finding on May 5, 2017:
The aircraft manufacturer did not account for the transient elevator deflections that occur as a result of the system flexibility and control column input during a pitch disconnect event at all speeds within the flight envelope. As such, there is no assurance that the aircraft has sufficient strength to withstand the loads resulting from a pitch disconnect.

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