Figure 7-4

STUDENT GUIDE

VISUAL NAVIGATION

cross wind components, by first computing the distance off to seconds.) As a final note on head

and tail wind computations, note the Head/Tail wind component equation for any aircraft is

basically:

Head/Tailwind (kts)

Time gained or lost (sec)

approx. time flown (min) since

min

last compensation update

7.7.2.5. As a result, whenever the approximate time flown in minutes is equal to the air speed of

the aircraft in nautical miles per minute, the head or tail wind is equal to the number of seconds

off of updated time. With this in mind, the Head/Tail wind equation can easily be used with any

aircraft at any airspeed.

EXAMPLE 7-3: A B-52 crew planned to fly VR-1616 at 360 knots TAS, which equates to 6 NM

per minute. If after 6 minutes of flight the crew finds themselves 15 seconds late, they can

assume a 15 knot headwind. If they found themselves 10 seconds late over three minutes, they

could assume by 6 minutes they would be 20 seconds late, indicating a 20 kt headwind. An EA-

6B Prowler planned at 420 knots TAS (7nm per minute) would assume 10 knots of headwind if

late by 5 seconds over three and a half minutes, or 10 seconds late over 7 minutes.

7.7.3. Totaling the Components:

7.7.3.1. The final step in wind analysis via the

track method is to compute the total wind

15 kts. Head wind

affecting the aircraft. As computation of the out

bound heading and airspeed is necessary to

complete each Two-Minute Prior call, prompt

total wind computation is necessary.

TOTAL WIND:

7.7.3.2. With the basic components derived,

125 degrees at

20 kts.

determine the total wind by using the

proportions shown in figure 7-5. An alternate,

though less accurate, method is to compute the

10 kts Cross wind

wind magnitude by adding half of the smaller

component to the larger component. Using this

technique, compute accurate bearings through

graphical analysis, as described in Unit 5 of the

Figure 7-4

T-34 VNAV text (see figure 7-4). Grading

standards are 30 and 10 kts. As the two-

minute prior call requires total wind computation to determine outbound heading and airspeed,

students must be fluent in these computations. Be careful of the common error of mistaking the

wind direction by 180, which effectively doubles the wind's effect on low-level navigation.

7-7