R. Manasseh Papers
R. Manasseh Home
In what follows, gusts will be considered `relevant' if they occur at the end
of a runway where landing aircraft touch down, or at the end of a runway where
aircraft taking off leave the ground. Four sensors, at the ends of each of the
two cross runways, will be considered. Here, the local mean wind direction at
each sensor is calculated over the 20 s averaging period and used to determine
if it is relevant to either landing or taking off, on the basis that
controllers will always try to have aircraft landing and taking off into the
wind. For example, sensor 1 would be considered relevant for landing (on
runway 07) during a particular 20 s period if the wind has a negative 
component, and relevant for taking off (on runway 25) if there is a positive
component. Naturally, the actual usage of the runways will depend on
decisions made by controllers over timescales much longer than 20 s and may
take criteria other than wind direction into account. However, it is presumed
that the local mean wind direction will be, on average, a reliable estimator of
the direction of runway usage.
Positive gusts are those in the same direction as the along-runway component of local mean wind velocity and hence impart extra lift to the aircraft. Negative gusts remove lift from the aircraft. `Left' gusts, defined as negative cross-track gusts, are those pushing an aircraft to the left of its path and vice versa for `right' gusts. The `landing' gusts for 13 April 1994 are in table 2 and the `take-off' gusts in table 3. The direction of aircraft operations defines the runway number referred to. Landing gusts for `runway 07', for example, are gusts occurring at sensor 1, while the take-off gusts for `runway 07' are gusts occurring at sensor 2. The gust bins are defined as for the true-direction gusts.
It can immediately be seen that there are very few landing or take-off gusts
of both along-track and cross-track varieties for Runway 34. This simply
reflects the fact that on a day of strong southerly winds there were very few
occasions in which the local mean wind might have permitted aircraft landings
or take-offs on a bearing of 
. In reality, it is probable that
these few occasions were isolated 20 s reversals of the local mean wind and
that controllers would not have changed the direction of operation in response
to them.
Table 2: Operations-relevant gusts at Sydney Airport on 13 April 1994:
Landing gusts. `A' denotes gusts along the aircraft track; `C'
denotes cross-track gusts. See text for explanations.
Bin increments as for
table 1
Table 3: Operations-relevant gusts at Sydney Airport on 13 April 1994:
Take-off gusts. `A' denotes gusts along the aircraft track; `C'
denotes cross-track gusts. See text for explanations.
Bin increments as for
table 1
R. Manasseh Papers
R. Manasseh Home
