preamble.
to estimate the frontal wind, the typical procedure is follows:
from IAS & altitude, calculate the TAS.
check the difference with the GS.
for exemple
IAS = 110 knt
ALT = 9000 ft
GS = 108 Knt
[ EIGS = 94 knt ]
Wind?
the traditional way is:
Wind = GS - IAS * ( 1 + FL * 1,68 / 1000)
or "simple"
9000 ft / 1000 = 9
9 * aprox 2% = 18%
TAS = 110 * 1,18 =
= 118 plus 10% =
= 118 + aprox 12 = 130 knt
wind = 130 - 108 = 22 knt frontal
is not exact,
is not immediate to calculate. but we have a navigation calculator.
can be helpful when FiF give us an additional speed data indication.
Its easyer when FiF calculate the "Equivalent Indicated GroundSpeed",
and the pilot can easy see the difference IAS - EIGS
without needing any altitude compensation calculation trough the pilots head.
EIGS - IAS 94 - 110 = -
16 knt frontal wind speed. Extremly easy!