B737NG DESCENT CALCULATION
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B737NG DESCENT CALCULATION
I have been told that there are various methods that can be used for descent planning on the B737NG using
1) The Cabin Altitude & Cabin rate indicator.
2) Existing Radial - Final Course
3) Using the meters scale
Appreciate if some one could shed some light on these, or any other method.
1) The Cabin Altitude & Cabin rate indicator.
2) Existing Radial - Final Course
3) Using the meters scale
Appreciate if some one could shed some light on these, or any other method.
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Actually I don't think that many TRTOs teaches descent planning. This is what Line Training if for. Everyone has to begin somewhere...
Using the meters scale is very simple. Basically it's 3x altitude as well - it just saves you the calculation. 30,000 feet = 9144 meter. Take the first two digits "91" and this is the approx. miles you require. Check this against your distance to touchdown on the FMC progress page. If there is less than 91 nm (in the example) you are high, and if more, you are below path. Depending on your speed, wind and number of turns, you might want to adjust a bit back or forth.
If being radar vectored, make sure the LNAV path also corresponds to what you expect to fly, obviously! Or replace the distance from the progress page with some trigonometry in your brain. Like distance to FAP, plus the distance of the approach, for the most simple and shortest distance. Or "the controller will probably take me 40 this way, then 7 nm base, a 4 miles intercept plus 10 nm final approach" = 61 nm (in which case you should be around 6100 meters height or 20,000 feet).
Using the meters scale is very simple. Basically it's 3x altitude as well - it just saves you the calculation. 30,000 feet = 9144 meter. Take the first two digits "91" and this is the approx. miles you require. Check this against your distance to touchdown on the FMC progress page. If there is less than 91 nm (in the example) you are high, and if more, you are below path. Depending on your speed, wind and number of turns, you might want to adjust a bit back or forth.
If being radar vectored, make sure the LNAV path also corresponds to what you expect to fly, obviously! Or replace the distance from the progress page with some trigonometry in your brain. Like distance to FAP, plus the distance of the approach, for the most simple and shortest distance. Or "the controller will probably take me 40 this way, then 7 nm base, a 4 miles intercept plus 10 nm final approach" = 61 nm (in which case you should be around 6100 meters height or 20,000 feet).
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There is a variation based on using VS.
30,000 at, say, 2000fpm =15 minutes at .7M (= ~420kts ie 7nm/min ) =105 miles.
2500fpm would be 12 minutes so 84 miles.
The basic 3x table method (3x Alt in 1000's + slow down allowance as needed) worked for me for 30 years though.
30,000 at, say, 2000fpm =15 minutes at .7M (= ~420kts ie 7nm/min ) =105 miles.
2500fpm would be 12 minutes so 84 miles.
The basic 3x table method (3x Alt in 1000's + slow down allowance as needed) worked for me for 30 years though.
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Am I beng thick, but I have no idea what you mean by No 1 & 2.? Why do so many so called educated pilots with a supposed above average grasp of mathematics need to resort to such tricks a using the metre scale? If you can't divide or multiply by 3 then god forbid you ever end up in my cockpit. AND don't even think about using a calculator for a load sheet.
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Gentlemen, you're getting trolled up. Literally.
And this for a top of descent calculation? Between airline pilots?
At the end of this one I will believe a descent calculation is B737NG-specific!
And this for a top of descent calculation? Between airline pilots?
At the end of this one I will believe a descent calculation is B737NG-specific!
Last edited by latetonite; 10th Jun 2014 at 17:07. Reason: Adding
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I use 3 times height in thousands plus a mile for every ten knots over 200 plus a mile for every ten knots of tail wind.
So 15000 at 270 kts with 30 kt tail wind needs 45 + 7 + 3 = 55 miles to touchdown.
Seems to work well.
Alternatively put the centre fix and desired alt in descent page for exact v/s to fly as a direct path.
So 15000 at 270 kts with 30 kt tail wind needs 45 + 7 + 3 = 55 miles to touchdown.
Seems to work well.
Alternatively put the centre fix and desired alt in descent page for exact v/s to fly as a direct path.
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I think you will not get many answers anymore from real pilots the way you insult people who are trying to help your knowledge upgrade.
I see my comment is not longer applicable anymore.
I see my comment is not longer applicable anymore.
Last edited by latetonite; 11th Jun 2014 at 15:13. Reason: Adding
