Undetected Engine Thrust Reverser Deactivation

The Australian Transport Safety Bureau (ATSB) is highlighting the importance of following procedures after a lockout pin was not removed after maintenance, which resulted in an Airbus A320’s left engine thrust reverser not activating when selected on landing.

The Airbus A320 had undergone overnight maintenance in Adelaide before departing for Gold Coast Airport, on the morning of 18 December 2017, operating as a scheduled passenger flight. After a normal descent and touchdown, the captain selected both engine thrust reversers. The left reverser, however, did not activate. The aircraft decelerated using normal braking, and taxied to the gate without further incident.

The ATSB investigation into the incident found that the left engine thrust reverser lockout pin had not been removed after the overnight maintenance, and so the aircraft had returned to service with the thrust reverser deactivated. The lockout pin had not been booked out of the tool store, and its installation was not recorded in the technical log. As a result, the checks that these procedures provided to ensure the pin’s removal were missed.
“This investigation highlights the importance of considering the environmental conditions in which equipment and tools will potentially be used, as well as the importance of following procedures that, in this instance, should have resulted in detecting the error,” ATSB Director Transport Safety Stuart Macleod said.

“When considering the effectiveness of equipment, tooling and procedures that aim to minimise the consequences of an error, an engineered solution is generally more effective than relying on procedural compliance. Further, within procedural compliance a functional check is generally more effective than a self-check of work.”

In response to this incident, the aircraft’s maintenance organization is taking a number of safety actions including highlighting the importance of the aircraft maintenance manual precautions to maintenance staff at Adelaide. All thrust reverser lockout pin warning flags are being lengthened to hang past the closed engine cowls, while pins will also have a warning notice attached for placement on the engine thrust reverser controls during maintenance.

Separately, Airbus has advised it has introduced an operational test of the thrust reverser system to confirm re‑activation after maintenance as part of the latest revision to the aircraft maintenance manual.

Read the report AO-2017-117: Undetected engine thrust reverser deactivation involving Airbus A320, VH-VQG, Gold Coast Airport, Queensland on 18 December 2017: https://www.atsb.gov.au/publications/investigation_reports/2017/aair/ao-2017-117