"d&tm" wrote in message
...

"Chad Speer" wrote in message
oups.com...
Terry - thanks for the reply, but heading is not known.

Stefan - we need to be able to plug these known values into a formula
and kick out a result. Assuming the original responder was on the
right track, I still don't know what to do with his suggestion. Any
ideas on that? I'm not lazy, this just went over my head a long time
ago. :-)

Chad, sorry misread the question. But I like a challenge so I had another
go.
Firstly I dont believe the equations given by the original poster are
correct. if you apply the cosine rule to the wind triangle for 2 aircraft
you get the following 2 equations.

TAS1^2=WS^2+GS1^2-2WSGS1COS(180-ABS(WD-TR1)
TAS2^2=WS^2+GS2^2-2WSGS2COS(180-ABS(WD-TR2)

WHERE TAS1 AND TAS2 ARE TRUE AIRSPEEDS FOR AIRCRAFT 1 AND 2
WS = WIND SPEED
WD =WIND DIRECTION IN DEGREES MAG
TR1 AND TR2 ARE TRACKS MAGNETIC FOR AIRCRAFT 1 AND 2
GS1 AND GS2 ARE GROUND SPEEDS FOR AIRCRAFT 1 AND 2.
(180-ABS(WD-TR) WILL GIVE YOU THE ACTUAL ANGLE BETWEEN WIND DIRECTION AND
TRACK.

Now we have 2 equations with 2 unknowns ( WS and WD) which should be
solvable but I am stuggling to get it out. However I did a little
exercise
which suggests the end result may not be very useful. because small errors
in the ground speeds will cause very large errors in the calculated wind
speed.

By subtracting the 2 equations above you get

WS=(GS2^2-GS1^2-TAS2^2+TAS1^2)/(2(GS2COS(180-ABS(WD-TR2)-GS1COS(180-ABS(WD-T
R1))
What I then did was calculate the ground speeds for 2 aircraft for a
known
wind of 20 kts from 220 M

aircraft 1 aircraft 2
TAS 120 100
GS 111.7 91.4
TR 290 150

If I then use my above equation for WS after setting wind direction to
220,
I get 20 kts as expected. However if I round off the GS to 112 and 91 kts
the Wind speed changes from 20 to 9.5kts which suggests the ground speeds
have to be super accurate to get anywhere near the right wind speed..
Given
that also you are taking the TAS from a flight plan, which will vary with
density altitude and RPM setting etc. suggests your objective is going to
be
rather difficult to achieve in practice.

Hope this helps and good luck. If you come up with the solution I would
love
to see it.
terry

should have mentioned
in 180- ABS( WD-TR)
ABS is absolute , ignore negatives.
terry