Hi Bob

I'm doing exercise 11 on page 53 of the irex book and question 4 asks for,
1. Heading required to intercept FPT
2. The heading required to maintain FPT after intercept.
3. The drift experienced.

My workings are 1. 085
2. 145???
3. 10 degrees left drift.

I can't seem to work out how your getting 155 degrees magnetic for no2??

I'm sure I'm probably doing something silly but I can get the first 3 questions no worries.

Kind Regards
Jacob

The drift you experienced on the original inbound track was 10°L (HDG 150 and ADF 350)
Once you have intercepted the FPT, it is reasonable to assume that the drift will be much the same since the wind and TAS haven't changed.
So you should have 10° of left drift on a FPT of 145°. That means your heading would have to be 155° and your ADF would read 350 once more.

Hi Bob.

Why are the questions in exercise 11 on page 53 using drift to create the new heading after intercept, when the examples on the previous pages are using the Track error (TE) to create the new heading after interception the correct track?

I can understand the use of drift, but I can't see why TE is being use on pages 51 and 52.

Thanks

You were originally tracking 140°M to the station with 10° of left drift (heading 150°M and ADF reading 350°R). After you have intercepted the required inbound track of 145°M, it is reasonable to assume that you will have the same drift, 10° left.

So the heading to keep you on the 145°M inbound track would be 145 + 10 = 155°M. (the ADF would again read 350°R as you flew towards the station).

In question 2 on page 52, you are outbound with a heading of 080°M. The ADF reads 170°R (-10 from). So your drift has been 10° left and the track made good is 070°M. The track error therefore, has been 20°. After you have intercepted the required outbound track of 090, you apply that same track error (that means you are assuming that the drift will not change).

So it really depends on what information the examiner gave you in the first place.

Bob

Thanks Bob.

I think I have it. Essentially it's the same thing. The example questions are taking the Track Error, which also includes the drift and adding or subtracting that from the original heading, but the exercise questions on page 53 are using the drift only and adding or subtracting to the FPT

Matthew

Yes Matthew, you've got it. Well done!