An Australian Transport Safety Bureau investigation preliminary report has detailed that an Airbus A350 passenger aircraft was about to be pushed back for departure from Brisbane Airport before it was observed that covers were still in place on its pitot probes.
Aircraft are fitted with pitot probe covers when parked at Brisbane Airport to prevent mud wasps building nests within and blocking their pitot probes, which are used to measure air pressure to calculate airspeed.
The preliminary report on the 27 May 2022 occurrence, released to provide timely information to industry to highlight the importance of pitot probe covers being removed, notes that an aircraft refueller on an adjacent bay observed the pitot probe covers were still in place when the aircraft appeared ready for pushback.
“A known hazard at Brisbane Airport, mud wasps can rapidly build nests in aircraft pitot probes,” noted ATSB Director Transport Safety Dr Michael Walker.
“An aircraft being cleared to commence taxiing and then commence take-off with all pitot probe covers still fitted is a serious event.”
Two maintenance contractor ground crew engineers – a licensed aircraft maintenance engineer (LAME) supervising an inexperienced aircraft maintenance engineer (AME) – had been assigned to conduct scheduled receipt, dispatch, certification, and maintenance duties for the Singapore Airlines A350 aircraft during a two-hour turnaround at Brisbane.
As pushback approached, the covers remained in place until an aircraft refueller, working at an adjacent bay, observed them and alerted the supervising LAME.
The pitot covers were then removed two minutes before expected departure, and pushback occurred shortly afterwards.
As part of its investigation, to date the ATSB has interviewed the LAME, AME and the refueller, and reviewed airport security video, which did not show that the required final walk-around of the aircraft was conducted by either the LAME or the AME prior to dispatch.
“From here, the investigation will include examination of flight crew pre-flight inspection procedures, engineering final walk-around procedures, and induction training procedures,” Dr Walker said.
“It will also examine the engineers’ training records, policies and procedures around fatigue and change management, and more security video recordings.”
The ATSB has previously highlighted the risks of pitot probe covers not being removed prior to departure with its investigation into a March 2018 incident where an Airbus A330 took off from Brisbane with covers still in place, meaning the flight crew were faced with unreliable airspeed indications.
That ATSB investigation (AO-2018-053) identified safety factors across a range of subjects including flight deck and ground operations, aircraft warning systems, air traffic control, aerodrome charts, and risk and change management.
“The loss of airspeed data due to mud wasp ingress can occur even after brief periods, and the use of pitot probe covers for aircraft turnarounds at Brisbane is largely an effective defence,” Dr Walker said.
“However, as that earlier ATSB investigation identified, their use introduces another risk, which is the potential for aircraft to commence a take-off with pitot probe covers still fitted.”
Read the preliminary report: Flight preparation event involving Airbus A350-941, 9V-SHH, Brisbane Airport, Queensland, on 27 May 2022
Read the final report: Airspeed indication failure on take-off involving Airbus A330, 9M-MTK Brisbane Airport, Queensland, 18 July 2018