Crosswind Cal Culations for T-6A

T-6A NAVIGATION

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

accomplishing this task.

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)

= Crosswind (knots)

Time flown (min) since last compensation update

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

20 sec X 6

= 10 knots right crosswind

6 min

FLIGHT PROCEDURES

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