Australian Flying — November-December 2017

also removed. Pilots who f ly at
mid-levels will therefore already be
familiar with the GPWT.
Besides showing the wind
strength and direction, GPWT
charts also show the temperature
for each altitude. Because there
are multiple grid points within a
particular forecast area, it’s now
possible to calculate headings and
groundspeeds more accurately
than could be done with just one
set of winds for an entire
forecast area.
For many GA pilots getting
used to GPWTs instead of the
forecast wind section of the
ARFOR will be the change
that needs most attention. For
convenience, the GPWT charts
are available in five degree
latitude-longitude grids for the
whole country, or in 1.5 degree
grids, broadly consistent with
the GAF boundaries. Low-level

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GPWTs are already available in

NAIPS, 21 hours in advance, and

can be used to advantage for long-

distance flight planning.

To use a GPWT, you need

to think about when and where

the f light is going – from which

you choose the correct chart

and grid point(s); then interpret

the grid box, remembering the

wind direction is given in tens of

degrees for 1000, 2000, 5000,

7000, 10000 and FL140, in order.

There’s a legend box to remind

you, and colour coding and

+/- signs to easily separate the

temperatures from the other data.

It’s important to realise that

this change means that you need

both a GAF and GPWT as the

principal parts of an enroute

weather briefing.

The major EFBs and f light

planning apps will obtain

GPWTs automatically. Sample GPWT Forecast for Tasmania.