Malaysia Airlines Airbus A330-300, registered as 9M-MTK, was performing flight MH-134 from Brisbane Airport (BNE),  Australia to Kuala Lumpur International Airport (KUL), Malaysia on July 18, 2018, when soon after a takeoff flight crew realized airspeed indicators were failing. The plane turned back and landed safely in Brisbane.

On August 30, 2018, the Australian Transport Safety Bureau (ATSB) published preliminary results of its investigation. The report confirms that the incorrect airspeed was due to covers protecting the pitot probes.

The covers used on 9M-MTK were fitted by a local support engineer, who claims he warned the operator’s maintenance engineer. However, the latter did not recall being advised of the covers’ presence. During the two inspections that the plane underwent in the three hours turnaround in Brisbane, both the technical crew and the flight crew failed to “identify the presence of the pitot probe covers [which] were not removed prior to the aircraft’s departure”.

Despite observing the incorrect airspeed during takeoff, the flight crew chose to proceed. Once airborne, they engaged safety procedures, turning off all three ADRs to activate the aircraft’s backup speed scale (BUSS). As the landing gear could not be extended normally with the ADRs off, the crew performed a landing gear gravity extension.

Using the data available, the ATSB determined that “the aircraft was flown within operational limits” following the activation of the BUSS.

Pitot probe covers are used in Brisbane due to a high level of insect activity. ATSB indicates that from 2008 to 2018 at least four of the 15 incidents at Brisbane airport where one of pitot probes had a partial or total blockage were attributed to insect nests. The Civil Aviation Safety Authority (CASA) states that wasps can build a nest in an uncovered pitot probe in less than 20 minutes.

Following the incident, the ATSB issued a safety warning (AO-2018-053-SAN-003) advising every operator in Brisbane airport to “consider the use of pitot probe covers”, and to ensure that check up routines include procedures to confirm covers are removed.

The next stage of the ATSB investigation is now to “determine the airspeed indications and related warnings and cautions being displayed to the flight crew during the take-off roll”.