Analyze

STUDENT GUIDE

VISUAL NAVIGATION

7.6.5.1. On course, on heading.

7.6.5.2. On heading, abeam.

7.6.5.3. Turning on the updated time (turn point not in sight).

dist. from

7.6.6. A final note on visual fixing involves a visual guide for

horizon to

measuring distances in the T-1. At 500 feet AGL, a feature

Aircraft = 5nm,

five miles (1-minute) ahead of the aircraft will appear half way

Horizon is

between the horizon and the top of the instrument shroud

15nm away.

panel, and the horizon is approximately 15NM away (3

minutes). (See fig. 7-3)

7.7. ANALYZE

Figure 7-3

7.7.1. Track analysis provides accurate wind information

already separated into components, easing the task of compensation. However, this method of

wind analysis can require more time and concentration--until proficiency is gained. The

methods of wind computation via track analysis are nearly identical to those used in T-34

navigation, with only minor changes due to increased aircraft speed. With the Fix completed, the

analysis begins with crosswind computation:

7.7.1.1. Crosswind Computation

7.7.1.1.1. The basic cross wind formula, introduced in VNAV Unit 5 does not include

any reference to air or ground speed.

Distance off course (NM) X 60 min = Crosswind (kts)

approx. time flown (min)

7.7.1.2. For the above equation, note that both "Distance off course (NM)" and "approx. time

flown (min)" are with respect to the last fix. Also, because this equation is independent of ground

or air speed, it works for T-34s, T-1s, and T-39s as well as F-15s, EA-6Bs and F-14s. Crosswind

is simply the velocity the aircraft is traveling left or right of course. What if the "approx. time

flown (min)" is equal to 6 minutes? Then the equation becomes:

Distance off course X 10 = Crosswind (kts) :(6 minutes)

For 4 and five minutes, the equations become:

Distance off course X 15 = Crosswind (kts) :(4 minutes)

Distance off course X 12 = Crosswind (kts) :(5 minutes)

7.7.1.3. Using the five minute rule learned in T-34 VNAV, for time intervals between 4 and 6

minutes the "5 Minute" rule or equation may be used. However, from the equations above we

see that for time intervals closer to 6 minutes we should round down (or multiply by ten rather

than 12) and for time intervals closer to four minutes, rounding up is more accurate (or

multiplying by 15 rather than 12). Also, for time intervals of 2 to 3 minutes, the error may be

doubled along with the time interval to m0ake computation easier:

EXAMPLE 7-1: After three minutes of flight, a fix reveals the aircraft is NM left of course.

7-5