Descent Planning
04-28-2011 | 07:40 PM
#11
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Joined: Feb 2006
Posts: 3,732
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From: DD->DH->RU/XE soon to be EV
altitude to lose (in thousands) x 3 = dme to start down
G/S divided by 2, add a 0 = FPM required for 3:1 calculation. (also works for FPM required for glideslopes)
example: you are 24000 need to cross nesto at 10000. Groundspeed is 420
14 x 3 = 42nm
420 / 2 = 210 add zero 2,100 FPM
start down at 42nm and use 2100 fpm
make sure to increase descent rate when GS increases
G/S divided by 2, add a 0 = FPM required for 3:1 calculation. (also works for FPM required for glideslopes)
example: you are 24000 need to cross nesto at 10000. Groundspeed is 420
14 x 3 = 42nm
420 / 2 = 210 add zero 2,100 FPM
start down at 42nm and use 2100 fpm
make sure to increase descent rate when GS increases
And remember everyone, the pu$$y paddles are for your mistakes, NOT the controllers.
Last edited by dojetdriver; 04-28-2011 at 09:20 PM.
04-28-2011 | 09:15 PM
#12
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Joined: May 2007
Posts: 144
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From: 757 FO
altitude to lose (in thousands) x 3 = dme to start down
G/S divided by 2, add a 0 = FPM required for 3:1 calculation. (also works for FPM required for glideslopes)
example: you are 24000 need to cross nesto at 10000. Groundspeed is 420
14 x 3 = 42nm
420 / 2 = 210 add zero 2,100 FPM
start down at 42nm and use 2100 fpm
make sure to increase descent rate when GS increases
G/S divided by 2, add a 0 = FPM required for 3:1 calculation. (also works for FPM required for glideslopes)
example: you are 24000 need to cross nesto at 10000. Groundspeed is 420
14 x 3 = 42nm
420 / 2 = 210 add zero 2,100 FPM
start down at 42nm and use 2100 fpm
make sure to increase descent rate when GS increases
1-degree nose down = ~100 ft/nm down
Therefore, another, perhaps easier way (depends on how your brain works I guess) to come up with the same 2,100 fpm above would be:
420 GS = 7 nm/min
7 * 3 (your desired glideslope) = 21 (add the zeros to get 2,100 fpm)
For crossing restrictions, figure out the required glideslope, then use that x your NM/min to determine fpm.
04-29-2011 | 06:06 AM
#13
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Joined: Jun 2008
Posts: 169
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From: Rebuilding the career
For years on our 727's we only had 2 VOR's and a DME...with no groundspeed readout (some things in the "good ole' days" weren't that good). I always used 3:1 and 3,000 fpm flight idle decent as a starting point - then checked my progress every 1,000 feet or so to see how I was doing and adjust the decent rate for apparent headwind/tailwind. I always enjoyed the challenge of timing the restrictions just right. Kept things interesting.
Of course, many of these rules of thumb will soon be lost on the next generation.
Soon the common answer is gonna be...
"Build the fix with the altitude restriction on the FMS, select VNAV, let the autopilot follow the snowflake."
(a part of me feels like it it cheating...tho I admit...it works very well
)
Of course, many of these rules of thumb will soon be lost on the next generation.
Soon the common answer is gonna be...
"Build the fix with the altitude restriction on the FMS, select VNAV, let the autopilot follow the snowflake."
(a part of me feels like it it cheating...tho I admit...it works very well)
04-29-2011 | 08:06 AM
#14
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Joined: Jan 2009
Posts: 324
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From: Going Mach Chicken
Also with the 3:1 rule, add a few miles of buffer if you have a strong tailwind. Also if you need to comply with a speed restriction (10,000ft and 250kts at XXXXX), I would increase the decent and/or distance to allow enough time to slow.
04-29-2011 | 08:41 AM
#15
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Joined: Feb 2006
Posts: 3,732
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From: DD->DH->RU/XE soon to be EV
Of course, many of these rules of thumb will soon be lost on the next generation.
Soon the common answer is gonna be...
"Build the fix with the altitude restriction on the FMS, select VNAV, let the autopilot follow the snowflake." (a part of me feels like it it cheating...tho I admit...it works very well)
Soon the common answer is gonna be...
"Build the fix with the altitude restriction on the FMS, select VNAV, let the autopilot follow the snowflake."
(a part of me feels like it it cheating...tho I admit...it works very well)
04-29-2011 | 02:06 PM
#16
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Joined: Jun 2008
Posts: 169
Likes: 0
From: Rebuilding the career
The old guys used to complain..."you young kids with your fancy 'wing-warping'! In my day, when we wanted to turn, we had to shift our bodyweight!".
Seriously though, I love and embrace new technology in the cockpit. It certainly has made things nice. Different skill sets required, though - which is why some of the mental math gymnastics will all but go by the wayside someday. Anybody remember how to determine your distance from a crossing VOR or NDB by timing as you cross radials/bearings? The 60:1 thing?(I never could remember that one - nor did I ever find the need to use it.)
But I'm afraid that eventually it will get to the point when the "aircraft operator" will just push the "take me to Chicago" button and then watch it all happen, and then it won't be any fun anymore.
Seriously though, I love and embrace new technology in the cockpit. It certainly has made things nice. Different skill sets required, though - which is why some of the mental math gymnastics will all but go by the wayside someday. Anybody remember how to determine your distance from a crossing VOR or NDB by timing as you cross radials/bearings? The 60:1 thing?(I never could remember that one - nor did I ever find the need to use it.)
But I'm afraid that eventually it will get to the point when the "aircraft operator" will just push the "take me to Chicago" button and then watch it all happen, and then it won't be any fun anymore.
Last edited by Likeabat; 04-29-2011 at 02:36 PM.
04-29-2011 | 03:26 PM
#17
Gets Weekends Off
Joined: Mar 2009
Posts: 173
Likes: 0
From: E-170
The old guys used to complain..."you young kids with your fancy 'wing-warping'! In my day, when we wanted to turn, we had to shift our bodyweight!".
Seriously though, I love and embrace new technology in the cockpit. It certainly has made things nice. Different skill sets required, though - which is why some of the mental math gymnastics will all but go by the wayside someday. Anybody remember how to determine your distance from a crossing VOR or NDB by timing as you cross radials/bearings? The 60:1 thing?(I never could remember that one - nor did I ever find the need to use it.)
But I'm afraid that eventually it will get to the point when the "aircraft operator" will just push the "take me to Chicago" button and then watch it all happen, and then it won't be any fun anymore.
Seriously though, I love and embrace new technology in the cockpit. It certainly has made things nice. Different skill sets required, though - which is why some of the mental math gymnastics will all but go by the wayside someday. Anybody remember how to determine your distance from a crossing VOR or NDB by timing as you cross radials/bearings? The 60:1 thing?(I never could remember that one - nor did I ever find the need to use it.)
But I'm afraid that eventually it will get to the point when the "aircraft operator" will just push the "take me to Chicago" button and then watch it all happen, and then it won't be any fun anymore.
03-21-2012 | 02:37 AM
#20
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Joined: Feb 2007
Posts: 1,292
Likes: 1
Use the app with a grain of salt (is that the saying?). Learn a few fundamental rules of thumb and they will be with you for the next 30 years of your career.
Last edited by usmc-sgt; 03-21-2012 at 06:19 AM.
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