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Preliminary report published: 30 August 2018

Sequence of events

On 18 July 2018 Malaysia Airlines Airbus A330-300, registered 9M-MTK, was scheduled to operate on a regular public transport flight from Brisbane, Queensland to Kuala Lumpur, Malaysia. The scheduled departure time was 2320 Eastern Standard Time.[1]

The aircraft had landed at Brisbane Airport at 2011, after a flight from Kuala Lumpur. The captain, first officer and certifying maintenance engineer from the previous night’s flight, who had been resting at a Brisbane hotel, arrived at the airport to commence their duties for the 18 July outbound flight.

Soon after the aircraft had landed, covers were placed on the aircraft’s three pitot probes.[2] Subsequent inspections during the turnaround did not identify the presence of the pitot probe covers and they were not removed prior to the aircraft’s departure (Figure 1).

Figure 1: Aircraft about to be pushed back with pitot covers in place (two of three visible)
Figure 1: Aircraft about to be pushed back with pitot covers in place (two of three visible). Source: Brisbane Airport Corporation. Image annotated by ATSB.Source: Brisbane Airport Corporation. Image modified by ATSB.

The first officer was the pilot flying (PF) and the captain was the pilot monitoring (PM).[3] Prior to aircraft pushback, the captain and first officer calculated the aircraft’s ‘V’ (critical) speeds for the take-off.[4] For this flight, the decision speed V1 (the maximum speed at which a rejected take-off can be initiated in the event of an emergency) was 153 kt and the rotation speed VR (when rotation should be initiated) was 160 kt.

The operator’s standard operating procedures for take-off required the PM to announce when the airspeed reached 100 kt and for the PF to cross check this airspeed indication.

The wind was calm and there was no cloud. At 2324, the flight crew commenced taxi for a take-off on runway 01. Subsequent events included:

  • 2331:05: The flight crew commenced the take-off roll.
  • 2331:38: The cockpit voice recorder (CVR) recorded that the captain called ‘100 knots’. The the aircraft’s recorded groundspeed at this time was 100 kt.
  • 2331:47: The first officer initiated rotation. The recorded groundspeed at this time was 165 kt.

The flight crew recalled that they detected an airspeed anomaly during the take-off roll, including red speed (SPD) flags on both primary flight displays (PFD).

The standard operating procedures stated that the captain held responsibility for the decision to reject the take-off or continue. It stated that rejecting a take-off between 100 kt and V1 was a serious matter, that a captain should be ‘go-minded’, and that very few situations should lead to the decision to reject the take-off. There was no indication on the CVR recording that the captain or the first officer discussed rejecting the take-off.

After take-off the flight crew carried out actions for unreliable airspeed indications and made a PAN call[5] to air traffic control (ATC), advising they had unreliable airspeed indications.

The flight crew continued to climb above 10,000 ft and manoeuvred the aircraft to the north-east of Brisbane Airport where they carried out several checklists, troubleshooting and preparation for an approach and landing on runway 01 (Figure 2).

Figure 2: Flight path of 9M-MTK during turn-back
Figure 2: Flight path of 9M-MTK during turn-back. Source: Google Earth / ATSB.Source: Google Earth / ATSB.

In accordance with published procedures, the flight crew turned off the three air data reference systems (ADRs) at 1343. This activated the aircraft’s backup speed scale (BUSS) (Figure 3), which provided a colour-coded speed scale derived from angle of attack and other information, and altitude derived from GPS data.[6] The flight crew also obtained groundspeed information from ATC, and used the aircraft’s radar altimeter.

Figure 3: Example of the backup speed scale (BUSS), showing the colour-coded scale (left) that indicates derived speed, and a GPS altitude scale (right)
Figure 3: Example of the backup speed scale (BUSS), showing the colour-coded scale (left) that indicates derived speed, and a GPS altitude scale (right). Source: Airbus
Source: Airbus

Normal landing gear extension could not be accomplished with all three ADRs off.[7] The flight crew performed a landing gear gravity extension before conducting an overweight[8] landing on runway 01 at 0033.

After landing the flight crew stopped the aircraft on the runway as nose wheel steering was unavailable following a landing gear gravity extension. The main landing gear doors, which remain open following a gravity extension, had minor damage where they contacted the runway surface. The aircraft was towed to the gate where the passengers and crew disembarked. There were no reported injuries during the flight.

A subsequent inspection identified that the pitot probe covers were still fitted to the aircraft’s three pitot probes after it landed.

Recorded data

The ATSB recovered and downloaded data from the aircraft’s CVR and flight data recorder (FDR), and obtained data from the aircraft’s digital ACMS[9] recorder (DAR), used for routine monitoring by the operator.

The data from the CVR and FDR contained all of the occurrence flight, while the DAR included all data up to 2348 and intermittent data after that time.[10] At the time of publication, the ATSB had not fully validated the data and analysis is ongoing.

The aircraft had three sources of airspeed:

  • ADR1, processing data for the captain’s pitot probe on the left side of the airframe, and usually presented on the captain’s PFD.
  • ADR2, processing data from the first officer’s pitot probe on the right side of the airframe, and usually presented on the first officer’s PFD.
  • ADR3, processing data from the standby pitot probe on the left side of the airframe, and usually presented on the integrated standby instrument system to the right of the captain’s instruments.

Airspeed was not recorded or displayed to the flight crew when it had a calculated value below 30 kt.

The FDR recorded airspeed from ADR3 once per second, and additionally from any one of the three ADRs twice per second depending on flight crew selection and data validity. Data from the FDR showed that ADR1 first sensed airspeed above 30 kt at 2331:39. At rotation, the FDR recorded 38 kt airspeed from ADR1 and the airspeed from ADR3 had not yet reached 30 kt. ADR3 first sensed airspeed above 30 kt at 2331:54.

The DAR sampled airspeed once per second and preliminary analysis shows broadly similar values as the FDR.

The maximum recorded airspeeds after take-off were 66 kt on the FDR and 57 kt on the DAR, prior to the ADRs being selected off when the data became invalid. These recorded airspeeds were consistent with the pitot probes being covered.

Preliminary analysis of the available groundspeed and angle of attack data indicated that the aircraft was flown within operational limits.

Further investigation is required to determine the airspeed indications and related warnings and cautions being displayed to the flight crew during the take-off roll.

Previous occurrences at Brisbane Airport

There have been multiple reports of insect activity disrupting aircraft systems at Brisbane Airport. These included blocked pitot probes, mainly from nests built by mud-dauber and other wasps, resulting in airspeed discrepancies and other effects.

A preliminary review of the ATSB database indicated that, from 2008 to 2018, there were at least 15 incidents involving high-capacity regular public transport aircraft departing from Brisbane Airport where one of the pitot probes had a partial or total blockage, at least four of which were identified as insect nests. These resulted in three rejected take-offs, four aircraft returning to Brisbane Airport after continuing the take-off and one aircraft that continued to its destination.

The ATSB investigated two rejected take-offs that involved A330 aircraft where one of the pitot probes had been blocked with wasp nests, one in 2006 and one in 2013.[11]

After the 2006 occurrence, the Brisbane Airport Corporation (BAC) commenced a monthly wasp eradication program, which was made weekly after the 2013 occurrence. BAC also undertook research to understand wasp behaviour and identify the pitot probe types at highest risk of contamination.

In May 2015, the Civil Aviation Safety Authority (CASA) issued Airworthiness Bulletin 02-052 ‘Wasp Nest Infestation – Alert’[12] to ‘urgently advise operators, maintainers and pilots of the dangers associated with undetected wasp infestation in aircraft, and the circumstances under which they can occur.’ It stated that wasps could build nests in aircraft that are stationary for more than 20 minutes with uncovered pitot probes.

From November 2015 onwards, the Airservices Australia produced publication En Route Supplement Australia (ERSA) entry for Brisbane Airport included a note that stated:

Significant mud wasp ACT WI AD VCY [activity within aerodrome vicinity] affecting pitot tubes [probes]. Pitot tube covers recommended.

Similarly, the Jeppesen aeronautical information publication Australia Airport Directory, used primarily by international pilots operating into Australia, also had the following in the Brisbane airport information section:

Significant mud wasp activity within apt [airport] vicinity affecting pilot tubes. Pitot tube covers recommended.

Some operators using Brisbane Airport use pitot probe covers for routine turnarounds.

Operator’s arrangements for ground handling at Brisbane Airport

Having previously ceased Brisbane operations in 2015, the aircraft operator recommenced flights to Brisbane on 6 June 2018. At the time of the occurrence arrangements had been made for the provision of services by a local ground handing provider and a local engineering support provider. On the day of the occurrence, aircraft turnaround duties were shared between:

  • a maintenance engineer from the operator who was rostered to return to Kuala Lumpur as a passenger on the departing aircraft
  • two non-certifying engineers from the engineering support provider
  • four ground handlers from the ground handling service provider.

The operator’s personnel and the ground handlers were both responsible for conducting pre-departure checks.

Use of pitot probe covers

The pitot probe covers were fitted on the aircraft’s three pitot probes by one of the engineering support personnel, as it was his understanding this was normal practice. He later reported that he advised the operator’s maintenance engineer that pitot probe covers were fitted during a brief exchange discussing turnaround tasks, but that the maintenance engineer did not directly respond. The maintenance engineer later reported that he did not recall hearing the advice, and he did not make an entry in the aircraft’s technical log to record that the covers had been fitted.

The presence of the pitot covers was not detected by the operator’s maintenance engineer or captain during separate external aircraft inspections. The operator’s maintenance engineer boarded the aircraft during turnaround, and the engineering support personnel left the bay to attend to other aircraft. The pitot covers were not detected by ground handlers during pushback.

The flight crew and operator’s maintenance engineer later reported that they would not routinely use pitot probe covers on a turnaround. They advised that the operator did not normally fly to airports where the use of pitot probe covers was standard. Security video recordings of the operator’s three previous turnarounds at Brisbane Airport showed that pitot probe covers were not used.

The pitot covers fitted to the aircraft were provided by the engineering support provider and were manufactured to fit Airbus aircraft types including the A330. They consisted of a tightly woven Kevlar sheath about 12 cm long, with a 30 cm streamer.

Examination of the three covers fitted to the aircraft following the occurrence found that they were partially burned by the heated pitot probes. They each had a hole burned through where the cover folded around the probe in the airstream. The streamers were damaged by contact with the aircraft skin during the flight (Figure 4 and Figure 5).

Figure 4: Pitot probe covers removed from 9M-MTK after the incident flight
Figure 4: Pitot probe covers removed from 9M-MTK after the incident flight. Source: ATSB
Source: ATSB

Figure 5: Reconstruction of pitot probe covers on 9M-MTK, showing pitot cover damage and rub marks on aircraft skin from the streamer
Figure 5: Reconstruction of pitot probe covers on 9M-MTK, showing pitot cover damage and rub marks on aircraft skin from the streamer.  Source: ATSBSource: ATSB

Ongoing investigation

The ATSB has interviewed the flight and ground crews, and examined data from the aircraft’s FDR, CVR and DAR, as well as airport security video footage from before and after the flight.

The investigation will examine the:

  • procedures, arrangements and interactions between the operator’s maintenance engineers, flight crews, engineering support provider and ground handling service provider
  • procedures relating to ground and flight crew pre-flight checks, including walk-around procedures
  • training records for flight crew, engineers and ground handling personnel
  • warnings, cautions and other information displayed to the flight crew during the occurrence flight
  • ATC recordings
  • closed-circuit video recordings
  • FDR, CVR and DAR recordings.

The investigation will also interview the air traffic controllers who communicated with the flight crew during the flight.

Safety actions

Proactive safety action

Whether or not the ATSB identifies safety issues in the course of an investigation, relevant organisations may proactively initiate safety action in order to reduce their safety risk. The ATSB has been advised of the following proactive safety action in response to this occurrence.

  • The aircraft operator provided a notice to all of its engineers and flight crew, which highlighted the need for pitot covers to be fitted to aircraft at Brisbane Airport during turnarounds or when parked, as well as the required procedures for their fitment and removal.
  • The aircraft operator and engineering support provider clarified and formalised more detailed service level arrangements.
  • The engineering support provider improved its procedures for conducting turnarounds, including improved inspection, documentation, and tool control.
  • The ground handling service provider provided all employees with a ‘read and sign’ bulletin emphasising its arrival and departure inspection procedures.

Safety advisory notice to all international operators using Brisbane Airport

Action number: AO-2018-053-SAN-003

The Australian Transport Safety Bureau advises all operators that conduct flights to Brisbane Airport to consider the use of pitot probe covers and, if covers are used, ensure there are rigorous procedures for confirming that covers are removed before flight.

 

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The information contained in this preliminary report is released in accordance with section 25 of the Transport Safety Investigation Act 2003 and is derived from the initial investigation of the occurrence. Readers are cautioned that new evidence will become available as the investigation progresses that will enhance the ATSB's understanding of the accident as outlined in this report. As such, no analysis or findings are included in this report.

 

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  1. Eastern Standard Time (EST): Coordinated Universal Time (UTC) + 10 hours.
  2. Pitot probes provide air data computers and flight instruments with airspeed information, and are ineffective if covered or blocked.
  3. Pilot Flying (PF) and Pilot Monitoring (PM): procedurally assigned roles with specifically assigned duties at specific stages of a flight. The PF does most of the flying, except in defined circumstances; such as planning for descent, approach and landing. The PM carries out support duties and monitors the PF’s actions and the aircraft’s flight path.
  4. The V speeds are referenced using airspeed, which is indicated on the aircraft’s primary flight displays. Groundspeed is shown on the navigation displays and is not normally used other than for navigation.
  5. An internationally recognised radio call announcing an urgency condition which concerns the safety of an aircraft or its occupants but where the flight crew does not require immediate assistance.
  6. Pressure altitude is provided by the ADRs and became unavailable after they were switched off.
  7. A safety valve prevents landing gear extension above 280 kt, and must be overridden when airspeed is not available.
  8. An ‘overweight’ landing is conducted at an aircraft weight higher than certified maximum landing weight.
  9. Aircraft condition monitoring system.
  10. The DAR was set to only record information that met the operator’s flight data analysis capture criteria.
  11. ATSB investigation report 200601453, Rejected takeoff - Brisbane Airport, Qld - 19 March 2006 - VN-QPB, Airbus A330-303. ATSB investigation report AO-2013-212, Air data system failure involving Airbus A330-243, A6-EYJ, near Brisbane Airport, Qld on 21 November 2013.
  12. Issue 4 of Airworthiness Bulletin 02-052 was released on 3 May 2018.
 
General details
Date: 18 July 2018 Investigation status: Active 
Time: 2231 EST Investigation phase: Evidence collection 
Location   (show map):Brisbane Airport Investigation type: Occurrence Investigation 
State: Queensland Occurrence type: Aircraft preparation 
Release date: 30 August 2018 Occurrence class: Operational 
Report status: Preliminary Occurrence category: Incident 
Anticipated completion: 2nd Quarter 2019 Highest injury level: None 
 
Aircraft details
Aircraft manufacturer: Airbus 
Aircraft model: A330-323XZ 
Aircraft registration: 9M-MTK 
Serial number: 1318 
Operator: Malaysia Airlines 
Type of operation: Air Transport High Capacity 
Sector: Jet 
Damage to aircraft: Minor 
Departure point:Brisbane, Qld
Destination:Kuala Lumpur, Malaysia

Safety Advisory Notice

Managing the use of pitot probe covers at Brisbane Airport
 
 
 
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Last update 04 September 2018