Incorrect lock-out bolt leaves thrust reverser deactivated
A Fokker F100 airliner inadvertently returned to service with a lock-out bolt installed, rendering one of its two engine thrust reversers inoperative.
An incorrect type of lock-out bolt used during maintenance the previous day meant that when the captain selected reverse thrust on landing at Karratha on a 27 December 2017 flight from Perth, the right engine thrust reverser did not activate. The aircraft was able to decelerate using normal braking and taxied to the gate without further incident.
An ATSB investigation found that during a maintenance task to inspect the aircraft engines’ emergency fuel shut-off cables, to safely isolate the thrust reverser mechanism a maintenance engineer installed the incorrect lock-out bolt, and then did not remove it after the maintenance was completed.
The investigation found that the engineer used the more conveniently located in-service lockout bolt from the aircraft’s flight deck for the task, instead of the appropriate maintenance lockout bolt, which is fitted with a large red warning flag, and had to be checked out of the tool store. As a consequence, the lock-out bolt did not show as missing during a tooling investory check as the aircraft was released to service.
Further, there were no warning labels in the cockpit to warn the flight crew that the bolt may be installed.
“This investigation highlights the risks of varying from procedures when performing maintenance tasks,” ATSB Director Transport Stuart Macleod said.
“It is important that, in all parts of the maintenance system, there is an awareness of human factors associated with completion of the task. An understanding of the demands associated with a task may help identify informal work practices that can then be aligned with the formal procedures.”
In response to this incident, the maintenance organisation has highlighted to maintenance staff the importance of following the safety instructions and warnings contained in the aircraft maintenance manual. Further, the maintenance organisation has reinforced procedures for maintenance activities – including task assessments, tooling, and task procedures.
Over the past three years, the ATSB has now investigated three separate incidents where maintenance engineers have inadvertently left lockout bolts installed in passenger aircraft engines after maintenance. The other two incidents, investigations AO-2018-064 and AO-2017-117, involved maintenance providers in Brisbane and Adelaide, respectively.
Click to read the full ATSB report