wind estimating facility

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wind estimating facility

Postby Werner » 06 Nov 2020, 13:22

Image
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!
Last edited by Werner on 06 Nov 2020, 14:08, edited 2 times in total.
Werner
 
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Re: wind estimating facility

Postby Werner » 06 Nov 2020, 14:03

for altitude in ft,
EIGS = GS / ( 1 + ALT * 1.68 / 1000)

for altitude in m, substitute 1,68 with 5,52

(regardless speed unit)
Werner
 
Posts: 17
Joined: 08 Mar 2013, 09:44

Re: wind estimating facility

Postby RogerF » 13 Nov 2020, 11:25

FIF already has a "wind measurement" function:

- Click on the compass
- Click on In-flight settings
- Click on Wind
- Click on Measure wind
- Make a 360° keeping a constant IAS.

FIF will calculate the wind component and use it in the display.

At least it should; I experienced some difficulties in using this feature: for a fast turn, the algorithm shows gaps and you need more than a single 360° to get a measurement.
Also, the algorith is not very "fault tolerant" so you need to keep the IAS really accurate during the turn; otherwise, FIF says "Invalid data" and you have to restart the full process.
Maybe Petr will consider making it more flexible.

Note that the calculation formula proposed by Werner would be a fast way to estimate the wind component by typing the compass heading and IAS.
FIF already has all other information.
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