Ineffective execution of checklists and the absence of nose-wheel chocking contributed to an Avro RJ85 airliner rolling forward after engine start and colliding with aircraft stairs and a light pole at Perth Airport, a new ATSB report details.
During the 30 July 2019 occurrence, the flight crew of a Cobham Aviation Avro RJ85 were preparing their aircraft for departure for a charter flight with two cabin crew and 62 passengers on-board.
The subsequent ATSB investigation found that the flight crew did not effectively check the brake system pressure during two separate pre-flight checklists, which meant they did not detect that there was insufficient pressure within the braking system, and did not identify that the system needed to be pressurised prior to engine start. (The aircraft had been parked after its previous flight for a number of hours; longer than the brake accumulator reservoir could retain pressure.)
The ATSB found that the initial and primary missed checks related to the captain not performing checklist items as required, and the first officer not effectively monitoring the checking actions of the captain and not independently checking the pressure systems.
Because of the missed checklist items, on engine start there was no brake pressure in the aircraft’s parking brake system. Once the captain gave the ground engineer clearance to remove the main wheel landing gear chocks, there was no other restraint in place to prevent an inadvertent roll forward, as the operator’s procedures did not involve repositioning chocks on the nose-wheel of departing aircraft.
Once started, the combined thrust of the aircraft’s four engines at idle power and the slight apron slope caused the aircraft to inadvertently roll forward. The crew attempted to apply the aircraft brakes. However, because there was no brake pressure, these attempts were ineffective.
The normal after-start checks would have pressurised the brakes, however because the crew were responding to the unexpected roll-forward, they did not perform these checks. The ATSB found that the crew had a very limited opportunity to take corrective action to prevent the collision. The close proximity of the edge of the apron and the surprise associated with the unexpected roll-forward reduced the crew’s ability to respond before it collided with portable aircraft stairs. The aircraft then collided with a bollard in front of a light pole, and then the light pole itself.
“This investigation highlights the importance of ensuring all checklist items are addressed,” says ATSB Executive Director Transport Safety Nat Nagy.
“As highlighted in this accident, individuals can be vulnerable to omitting checklist items and this can lead to accidents.
“Aviation safety relies on a resilient safety system involving multiple defences. In the context of multi-crew operations, one of the key defences against this type of accident is the other pilot monitoring and cross-checking the pilot who is completing the checklist. This can provide a last line of defence to trap individual errors.”
Mr Nagy also noted that although safety systems should seek to reduce errors developing, where possible engineering defences, like wheel chocks, should also be used to reduce error consequences.
Since the incident Cobham have reiterated to their check and training captains the importance of vigilance during checklists, and are planning to update procedures to require the use of nose-wheel chocks when dispatching aircraft from stand-off bays.