Interim Report 2

Summary

Second interim report - published: 5 May 2017

On 20 February 2014, a Virgin Australia Regional Airlines (VARA) ATR 72 aircraft, registered VH‑FVR, operating on a scheduled passenger flight from Canberra, Australian Capital Territory to Sydney, New South Wales sustained a pitch disconnect while on descent into Sydney. The pitch disconnect occurred while the crew were attempting to prevent the airspeed from exceeding the maximum permitted airspeed (VMO). The aircraft was significantly damaged during the occurrence.

In accordance with the Transport Safety Investigation Act 2003 (the Act), the ATSB initiated an investigation into the occurrence. On 15 June 2016 the ATSB released its first interim investigation report that contained the following safety issue:

  • Inadvertent[1] 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.

In the interest of transport safety, this safety issue was brought to the attention of the aircraft manufacturer (ATR) and the wider aviation industry prior to completion of the investigation.

During the continued investigation of the occurrence, the ATSB has obtained an increased understanding of the factors behind this previously identified safety issue. This increased understanding has identified that there are transient elevator deflections during a pitch disconnect event that could lead to aerodynamic loads that could exceed the strength of the aircraft structure.

The ATSB also found that these transient elevator deflections were not identified, and therefore not considered in the engineering justification documents completed during the aircraft type’s original certification process. The ATSB considers that the potential consequences are sufficiently important to release a further interim report prior to completion of the final investigation report.

This second interim report expands on information already provided in, and should be read in conjunction with, the interim report released on 15 June 2016 report and an update on the ATSB website on 10 June 2014.[2] It is released in accordance with section 25 of the Act and relates to the ongoing investigation of the occurrence.

Readers are cautioned that the factual information and analysis presented in this interim report pertains only to the safety issue discussed herein. The final report will contain information on many other facets of the investigation, including the operational, maintenance, training and regulatory aspects.

Readers are also cautioned that new evidence may become available as the investigation progresses that will enhance the ATSB’s understanding of the occurrence. However, in order to ensure the veracity of the analysis of the evidence leading to the identified safety issue, the ATSB engaged the UK Air Accidents Investigation Branch (AAIB) to conduct a peer review. The AAIB conducted an analysis of the evidence relating to the safety issue and concluded that their findings were consistent with those provided by the ATSB.

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  1. In the context of this safety issue, ‘inadvertent’ is taken to mean that the opposing pitch control inputs were unintended.
  2. www.atsb.gov.au/publications/investigation_reports/2014/aair/ao-2014-032.

Context

Safety analysis and finding

Findings

Safety issue and actions

Appendix A – Transient response of a simple dynamic system