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Distance to commence a descend

• Posts: 163

jukzizy created the topic: Distance to commence a descend

Sir please just explain this to me how to calculate this..question.

Cruising level= 060
Gs= 120
Rod= 500fpm

You are required to reach 3000ft by 10nm from destination. What distance from destination should you commence decend?

t=3000ft÷500ftpm=6 minutes
D= S×T
120×6=720÷60=12 NM

12nm+10nm=22nm

Please just check and help me out.

• Posts: 512

Stuart Tait replied the topic: Distance to commence a descend

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• Posts: 168

Carello replied the topic: Distance to commence a descend

If 3000' is an altitude, your working is correct.

If 3000' is a height AGL, you will need to account for the aerodrome elevation.
The following user(s) said Thank You: jukzizy

• Posts: 45

Sofeopka replied the topic: Distance to commence a descend

Looks okay, I got 23NM but I used E6B computer and rounded the distance 13NM for the distance covered during the descent.

You state cruising level 060. I think levels normally apply above the transition layer. So unless it was FL 600 in the question, but I don't think it was because that would have to come accompanied with a QNH to allow the same datum to be used for correct measuring of vertical distance required to climb or descend.
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• John.Heddles
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• ATPL/consulting aero engineer
• Posts: 494

John.Heddles replied the topic: Distance to commence a descend

I got 23NM but I used E6B computer and rounded the distance 13NM for the distance covered during the descent.

Then you are using your computer incorrectly. Can you take a photo of your settings and post them so we can sort out whatever problems you might be having with its use, please ?

I think levels normally apply above the transition layer.

"level" is just a generic term. It would have been better had the question referred to A060 to make it clearer that the intention was to refer to an altitude rather than a flight level.

Engineering specialist in aircraft performance and weight control.

• Posts: 45

Sofeopka replied the topic: Distance to commence a descend

Silly me. I misread my E6B. Yes it's 12 and subsequently 22.

Thanks John. Picture included highlighting my silly error!

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• Posts: 494