Formula For Climb Gradient

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05-04-2009 | 04:59 PM

#21

Dan64456

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Quote:

Originally Posted by geosynchronous

500 feet per nautical mile divided by 6076' (one nautical mile) x 100 will give you the required climb gradient.

500/6076x100= 8.23%

Take your gradient times your groundspeed to get a climb rate in feet per minute

8.23x150= 1235 feet per minute

Would someone care to explain the last part for me? How does the gradient %times groundspeed translate into FPM?

Thanks!

05-05-2009 | 03:47 AM

#22

geosynchronous

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From: Corporate Captain

Sure!

For example, if you have a rise of 500 feet per mile, and the run is one nautical mile, you divide rise over run, move the decimal over two places (x 100) and then you have a gradient.

A good rule of thumb is to take the gradient times your groundspeed to have and estimated climb rate in feet per minute. Or, you can look at the rate of climb table in the front of the Jeppesen (tables and codes) book.

I'm dusting off my trigonometry here, so mathematically the vertical distance that you are climbing equals the sine of 8.23 times the opposite over the hypotenuse: take that distance and divide it by 360 to arrive at feet per minute.

Last edited by geosynchronous; 05-05-2009 at 04:00 AM.

05-06-2009 | 07:07 PM

#23

RAHPilot5

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Quote:

Originally Posted by jetjockee

Try this-

Ft per NM divided by 6000 times 100, this will give you the Climb Gradient..

500
----- X 100 = .0833333 X 100 = 8.33% Climb Gradient
6000

500' = Ft per NM

6000' = How many feet in a NM ( I believe its 6032' per NM, I just round it off )

that better be a chick's a$$

10-31-2014 | 08:24 AM

#24

AF330

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How do you calculate FT/NM?

Thanks

10-31-2014 | 11:54 AM

#25

RI830

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From: Left seat on a kite

Quote:

Originally Posted by AF330

How do you calculate FT/NM?

Thanks

groundspeed / 60 = Z (nm per minute)

Climb rate / Z = Ft per NM
.................................................. ..

120kts / 60 = 2 nm per minute

2000 / 2 = 1000 ft per nm

10-31-2014 | 09:14 PM

#26

RodJohnson

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Get ultranav.. Does it all for you

11-01-2014 | 03:51 AM

#27

AF330

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Thanks RI830

02-17-2020 | 03:04 PM

#28

alexixalex

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Quote:

Originally Posted by Dan64456

Would someone care to explain the last part for me? How does the gradient %times groundspeed translate into FPM?

Thanks!

If Gradient = fpm/feet_in_one_minute

then fpm = feet_in_one_minute * gradient

ex: 450 fpm, 150GS

find how many feet traveled over the ground in one minute: 150kts/60' = 2.5 NM * 6000 = 15000ft traveled over the ground in one minute.

then

Gradient = 450ft/min/15000 = 0.03 * 100 = 3% gradient

so 3(gradient) * 150(GS) = 450 ft/min
or 0.03(before the multiplication) * 15000(feet traveled in one minute) = 450ft/min

whichever you like