Narrative:On 14 March 2015, at about 07:50 LT an Airbus A330-343 aircraft operated by Malaysia Airlines, began its final approach to runway 34 at Melbourne Airport in Australia. The flight was a regular passenger service from Kuala Lumpur, Malaysia to Melbourne. The flight crew consisted of a captain, who was the pilot flying (PF) and a first officer, who was pilot monitoring (PM).
The approach to runway 34 at Melbourne airport was not equipped with an Instrument Landing System (ILS), so a non-precision approach was performed, aided by PAPI lights.
Flight data showed that the PF disengaged the autopilot at approximately 700 feet above ground level (AGL) and from that point until touchdown there was an increase in the frequency and magnitude of sidestick pitch control inputs by the PF.
In response to these inputs the aircraft’s autothrottle system varied the engine thrust to maintain a target speed, as per system design, and the aircraft pitch angles fluctuated between approximately -0.5° nose down and +5.0° nose up. The net result of the varying thrust settings and pitch angles was a fluctuating rate of descent between approximately 380 and 960 feet per minute.
Large sidestick inputs, specifically nose-down, also have the potential to inhibit the vertical speed reduction function, which is an automated function that provides some protection against touchdown at very high vertical speeds.
As the aircraft passed 300 feet a rate of descent of 960 feet per minute was recorded. This neared the operator’s maximum stabilised approach limit of 1000 feet per minute when below 500 feet AGL. As well as a high rate of descent, actual exceedances of the operator’s stabilisation criteria included: large changes to pitch inputted by the pilot flying, including negative pitch values, fluctuations in the rate of descent over a large range that were abnormal for the phase of flight, incorrect glide path.
From approximately 250 feet AGL, the aircraft was trending low and continuing below the glide path. At this point the pilots would have been able to observe 3 red lights and one white light on the PAPI. This trend was allowed to continue until the aircraft was well below the desired glide path to the extent that the PAPI would have indicated 4 red lights from approximately 125 feet AGL. From this point the PF made numerous pitch commands which were mostly nose down. These included a full range nose down deflection at 24 feet AGL.
The company procedures and manufacturer’s recommendations dictated that if an approach becomes unstable below 500 feet AGL, a go-around must be initiated by the pilot flying (PF) and/or the pilot monitoring (PM) must alert the PF of the unstable approach and encourage a go-around.
At 60 feet AGL the captain moved the thrust levers forward momentarily into the TOGA (Take-off/Go Around) detent. The captain stated that this was done in response to a feeling that the aircraft was sinking below the path, and the intention was to reduce this sink by applying more thrust to the engines. The placement of the thrust lever into TOGA placed the aircraft automation into the go-around autopilot modes and changed the display on the primary flight display flight mode annunciator (FMA). The captain subsequently reduced the thrust levers.
The PM, on seeing the modes on the FMA change assumed that a go-around was being conducted and awaited further announcement from the captain. The PM reported noticing the thrust levers reducing and that the aircraft was not flaring and applied nose up input to the sidestick at the same time as the PF.
At the time of the occurrence there was no procedure on the A330 for the use of manual thrust for this purpose. Prior to 2009, a procedure existed in the Airbus A330 documentation that allowed a specific use of manual thrust in difficult environmental conditions. Airbus advised that after an analysis of in-service events the procedure was removed from all operational documents.
Manipulation of the thrust levers in this manner had the effect of disengaging the autothrottle thereby inhibiting some of the available auto flight system protections including the target speed function (which automatically maintained the desired speed and adjusted for fluctuation in the wind), and the vertical speed reduction function.
It also caused a pitch up tendency which usually requires a large nose down input by the pilot flying to prevent the aircraft from pitching up. At this stage in the approach applying large nose down inputs differed from the gradual nose up input normally required to complete the flare.
Furthermore, it resulted in breaking down of the shared mental model between the pilot flying and pilot monitoring in that the pilot monitoring believed the advancement of the thrust levers was the initiation of a go-around.
Shortly after this action, the aircraft touched down at a vertical speed of approximately 700 feet per minute and a vertical acceleration of 2.61 G was recorded. The aircraft also touched down at approximately 170m (560 feet) from the landing threshold, short of the normal touchdown zone of between 304m (1000 feet) and 609m (2000 feet).
The manufacturer of the aircraft produced a complete load analysis of the event based on recorded flight data provided by the operator. The conclusion of this analysis was that several components in the left and right gear had "exceeded their design load limits and may have been detrimentally overloaded".
There were no injuries reported as a result of the hard landing.
The airplane remained at Melbourne until March 26, when it was ferried at low altitude to Darwin, Australia, and continuing to Kuala Lumpur the next day for further repairs.
Probable Cause:Contributing factors:
- The final approach became unstable at around 300 feet above the ground due to the control inputs from the captain.
- Inadequate monitoring and communication by the crew led to a lack of recognition of the undesirable flight state and the continuation of an unstable approach.
- Continuation of the unstable approach led to a high rate of descent at touchdown and resulted in a hard landing in excess of the aircraft design loads and short of the normal touchdown area.
Other safety factors:
The captain used an unapproved manual thrust procedure in an attempt to recover the approach
|investigating agency: ||Australian Transport Safety Bureau (ATSB) - Australia |
|released:||5 April 2017|
|duration of investigation: ||2 years |
|download report: ||
METAR Weather report:
20:30 UTC / 07:30 local time: YMML 132030Z 36012KT CAVOK 11/07 Q1016 NOSIG
21:00 UTC / 08:00 local time: YMML 132100Z 36015KT CAVOK 12/07 Q1016 NOSIG
Graphical representation of the flight data from the incident approach
This map shows the airport of departure and the intended destination of the flight. The line between the airports does not
display the exact flight path.
Distance from Kuala Lumpur International Airport to Melbourne-Tullamarine Airport, VIC as the crow flies is 6284 km (3928 miles).