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Confusing Question in the Text Book

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P.Potter created the topic: Confusing Question in the Text Book

Evening All,

In the text book Exercise 9 question 4. See attached.

I do not understand how if the FPT is 200, track to the station is 215 and on the left of the FPT, how does 245 end up on the other side of the 200 FPT???

Thanks in advance.
Phil
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  • John.Heddles
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John.Heddles replied the topic: Confusing Question in the Text Book

ADF work can be quite confusing until you get on top of it.

Keep in mind that successful ADF flying is all about continuous orientation. Where am I pointing ? (HDG). Where is the station ? (Relative bearing - the needle more or less points at the station). What is the bearing to (or from) the station ? (HDG and relative bearing) - if all else fails, think about turning to point directly at the station and the heading will be the bearing to the station. Different folks learn differently. For me, I drew lots of pictures to get my head around things. This may work for you - give it a try.

In this case, you start off pointing 205M. The station is ahead with a relative bearing of 010 so the bearing to the station is on the right of the HDG by 10 degrees ie 215M. You wish to track in on a bearing to the station of 200M. This means you have to turn right so that you have the station on your left side (otherwise you won't intercept). Keep it simple, we like 30/45/60 degree intercepts so let's use 45 degrees and make the heading 245M. This gives a target intecept of 45 degrees with respect to the inbound bearing. When we get to the inbound bearing (200M) that will make the relative bearing 45 degrees on the left of the nose (315R). In practice we watch this approaching and turn a bit early ("lead") to allow for the turn radius onto the required inbound track. Then it's a matter of figuring a likely drift, apply it, and monitor the results, adjusting things as you need to achieve the track.

30/45/60 are typical but, should you want to make an intercept of 27.5 degrees, go right ahead and fill your boots. The technique doesn't change - only the sums get a bit messier and, for flying, simplicity is money in the bank.

It is just "draw a picture on a bit of paper" geometry.

If you draw the picture, I think that your confusion will evaporate. If not, try rephrasing the question and we will rephrase the answer to suit.

Engineering specialist in aircraft performance and weight control.
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bobtait replied the topic: Confusing Question in the Text Book

I don't know where the '245' came from. I assume you meant 215.
When you are inbound to the destination, you need to project the track through the azimuth scale to the outbound side. It then becomes clear that the higher number will always be on your left if you are inbound.
Bob

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P.Potter replied the topic: Confusing Question in the Text Book

Hi John,

Thanks for the reply and answer. I was getting the "from" the station all right but the interception "TO" the station was what was getting me confused.

Cheers,
Phil.
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P.Potter replied the topic: Confusing Question in the Text Book

Afternoon Bob,

Thanks for the reply.

Just as an FYI, the 245 was the heading to intercept a 200 degree FPT by 45 degrees. As per the answer in your text book. I was just confused as to how the 245 was on the opposite side of the FPT 200 from the 215 adjusted ADF read.

I think after your drawing i have a different way of looking at it.

Thanks for your response.
Phil.
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