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Figure 5: Melbourne airport3
The recorded data from the MLW1 anemometer revealed that, during the period between
1100 and 1200, the mean wind direction ranged from between 245 to 352 degrees true.
During that same period, the maximum wind speed ranged from 6 kts to 27 kts, and was
greater than 15 kts for a total of 34 minutes.
Table 1: Melbourne airport anemometer data at 1200
Anemometer Wind
speed,
(Mean)
Wind
speed,
(Min.)
Wind
speed,
(Max.)
Wind
direction
(Mean)
Wind
direction
(Min.)
Wind
direction
(Max.)
MLW1 20 kts 15 kts 27 kts 260 True 247 True 273 True
MLW2 21 kts 18 kts 25 kts 258 True 260 True 266 True
A wind rose providing information about the 1-minute distribution of maximum
wind speeds and the frequency of the varying wind directions that were recorded by
the MLW1 anemometer between 1100 and 1200 is depicted at figure 6.
© Airservices Australia 2006. Reproduced with the permission of Airservices Australia.
– 7 –
3
Figure 6: MLW1 anemometer wind rose for period 1100 to 1200
The wind displays in the control tower at Melbourne Airport showed a graphical
depiction of wind direction, accompanied by a digital representation of the actual
wind strength. The displays were selectable to display actual wind strength, or
crosswind component for the runway selected.
During the investigation, Airservices Australia reported that, during typical tower
operations, it was normal practice to have the wind display in front of the aerodrome
controller selected to display the threshold wind for the duty runway. A second wind
display on the controller’s console was normally selected for a second duty runway,
if in operation, or for a non-duty runway when one was being used. Airservices
reported that the aerodrome controller on duty at the time of the occurrence believed
that the first wind display on the controller’s console had been selected to display the
threshold wind for runway 27, and that the second wind display had been set to
display the threshold wind for runway 16.
Airservices Australia also reported that it was possible that, in the strong westerly
wind conditions that existed at the time of the occurrence, lee turbulence may have
been present in the latter area of the approach onto runway 16. If present, that
turbulence had probably been generated by the passage of the strong westerly winds
over an area known as the Box Forest that was located in the north-west quadrant of
Melbourne Airport, and which was to the west of the runway 16 touchdown zone.
The crew subsequently reported that they were aware of the risk of an engine
‘podstrike’ during crosswind landings on the A340. They also reported that, when the
aircraft was on short final for the landing on runway 16 at Melbourne, they could see
that strong and gusty crosswind conditions existed.
– 8 –
Aids to navigation
Ground-based aids
A windsock was located to the east of the touchdown zone of runway 16. It provided
aircraft crews with a visual indication of the direction of the surface wind and a
general indication of the prevailing wind speed for a landing on runway 16.
Ground-based navigation aids, onboard navigation aids, and aerodrome visual
ground aids, and their serviceability, were not a factor in this occurrence.
Equipment on board the aircraft
Presentation of wind speed and direction data to the crew
The aircraft was fitted with an electronic flight instrument system, comprising of
primary flight display and navigation display (ND) units installed on the flight
instrument panels in front of each crew member. The top left portion of each ND
provided the crew with an inertial reference system (IRS)-derived presentation of
wind speed and direction data in both digital and analogue format. Additionally, the
aircraft’s true airspeed (TAS) and groundspeed (GS) were presented above the wind
speed and direction data.
The inertial reference system (IRS) wind was derived from the aircraft’s TAS and
GS vectors. The IRS wind was computed about 10 times per second, and was
displayed on the crew’s NDs. The displayed IRS wind was therefore, in practical
terms, the real-time wind being encountered by the aircraft.
Air data inertial reference units
The aircraft’s Air Data Inertial Reference System (ADIRS) included three air
data/inertial reference units (ADIRUs). Each unit provided inertial reference
information, and an indication of the aircraft’s attitude (pitch, roll and yaw), heading,
ground speed and present position. Acceleration signals from the attitude and
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