Temperature at FL120 =
+15º - (2º x 12) = +15º - 24º = -9ºC.
On nav. computer in the
AIRSPEED window put temperature (-9ºC) next to pressure altitude (FL120), go to
CAS (200kts) on inner main scale and read TAS next to it on the outer scale:
239kts.
Heading = 215ºM,
Variation = 15ºW, Heading = 200ºT. Track = 222ºM, Variation = 15ºW,
Track = 207ºT.
On nav. computer put time
(21 minutes) on inner main scale next to distance (105 nm) on the outer main
scale; go to 60 minutes on the inner scale and read groundspeed next to it on
the outer scale: 300 kts.
On the ‘wind’ side on the
nav. computer put the centre dot on the TAS (239kts), put the heading (200ºT)
next to the HEADING index, mark where the drift (7ºStbd (right)) crosses the
groundspeed (300kts).
Rotate to put the mark
below the centre dot and read the wind: 050ºT/70kts.