Crosswind Cal Culations for T-6A

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CHAPTER FIVE
Typically, this is easier when the smoke has a point source, such as a smokestack. Figure 5-14
gives a rough guide for estimating wind velocity based on its angle with a vertical axis. Be
careful to visually follow the path of smoke path in its ascent, as this can provide visual cues to
the existence of horizontal shear, in which either the wind magnitude or direction (or both)
changes.
Forecast wind manipulation involves imagining the forecast wind and changing it by magnitudes
based on course and/or time deviations. Refer to the following sections for methods of
506. CROSSWIND CALCULATIONS FOR T-6A
Crosswind is the component of the wind that "pushes" the aircraft off course. It is nothing more
than the velocity of the aircraft perpendicular to its heading. This lateral component may be
calculated using the following formula:
Distance off course (NM) X 60 min = Crosswind (knots)
approx. time flown (min)
1 hr
An alternative method of computing crosswind values is to convert the distance off into seconds,
and apply the following equation:
Distance off course converted to time (sec)
X
6
= Crosswind (knots)
Time flown (min) since last compensation update
2
For this equation, 6/2 represents your "miles-per minute." For a planned ground speed of 180
knots, this is equal to 3.0 NM/min at 300 knots, this value increases to 5 NM/min. Additionally,
for 180 knots 1 NM is equal to 20 seconds. For 180 knots, 1 NM equals 20 seconds.
Example
On the first leg of a low-level you acquire a road/ railroad intersection, which should be 1/2 mile
left of course at time 5+48. At time 5+50 the intersection passes down the right side of the
aircraft at 1/2 mile. How much crosswind are you encountering assuming no prior
compensations for the wind?
You are 1 NM left of course, and have been flying for about 6 minutes. Before working the
numbers, realize you have a right crosswind because you are left of course, then:
1 NM X 60 min
= 10 knots right crosswind
6 min
1 hr
-
OR ­
20 sec X 6
= 10 knots right crosswind
6 min
2
FLIGHT PROCEDURES
5-23

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