Figure 35

INSTRUMENT NAVIGATION

In Figure 35, the aircraft is crabbing 5 into the wind (095 heading) to maintain its present

radial, 270 and its course of 090.

Figure 35

In addition to the method previously learned using the CR-2 computer, we can determine

how much actual crosswind is acting on this aircraft. It will be a function of the aircraft's true air

speed (TAS) and crab angle. Here is the procedure:

1. Take the aircraft's TAS and divide it by 60 minutes:

For example:

180 - 60

3 NM/MIN

240 - 60

4 NM/MIN

300 - 60

5 NM/MIN

330 - 60

5.5 NM/MIN

420 - 60

7 NM/MIN, etc.

The quotient is your TAS in NM/MIN which we will call your "guide number".

2. Now multiply your crab angle by the guide number. The product of that calculation will

be a rough estimation of your crosswind component.

Therefore, if our aircraft is crabbing 5 and our TAS is 360, then our guide number is 6 and

our crosswind component of the wind is 30 knots. This procedure can also be used in reverse to

solve for a crab with a known crosswind. Simply divide your crosswind component by your

guide number. The quotient is your crab angle.

RADIAL TRACKING AND COURSE CONTROL 3-25