@Chaptain_JingRan
MaxSez: Try this:
It doesn’t take into account speed changes, and I doubt (although feasible) you’d want to recalculate with every 20 knot loss.
@TOGA. MaxSez… Elementary my dear Toga… we must always remember that we’re dealing with a general population. The KISS principle is the key 🔑. Most aviation enthusiasts,our general population, has limited technical expertise. Always play to the general audience it is more rewarding.
MaxSends
To calculate your VS you have to do GS x 5 ,for example 400 GS x 5=2000 so your VS will be -2000. Instead to calculate the distance when you have to start your descend you have to do FL: 3 ,for example FL350 : 3 = 117, so you have to start your descend at about 117 nm at -2000 VS.
maybe it’s little low
I usually descend anywhere from -1300fpm to -1700fpm when flying the A359.
Usually i aim for -2000 at about 110nm.
I usually use the following formula to determine when to begin my descent:
At time [in minutes] = (Cruise Altitude)-10
I usually start at around -1000 to -1200 ft./min and gradually increase or decrease the VS depending on the flight parameters. I rarely ever exceed -1500 ft/min though.
My typical final cruising altitude is anywhere between FL380 and FL430, so using the above formula, I usually begin my descent around the 28-33 minutes to destination (ETE to Dest) mark. This is typically how a long a realistic descent lasts in real life commercial services. Including the slowing down and pattern, my total time from initial descent to touchdown lasts around 45 minutes.
Although this is sometimes a crude way of doing it, I find that it gets the job done while allowing for flexibility in my approach. However, if you want to go very mathematical about it, I recommend some of the links given above. Hopes this helps!
I use the following formula for my descends
How to calculate a descent
Find the amount of feet you need to descend.
-E.g 37000 FT
•Take the last two digits off.
= 370
•Divide by 3.
= 123
That is the distance you need to start your descent away from the airport.
You need to track your descent as you descend, to do that you need to work out the distance away from the airport you’ll be at a given altitude.
The altitude can change depending on how high above sea level the airport is.
FT(AGL) / NM
420 =140
410 =137
400 =134
390 =130
380 =127
370 =123
360 =120
350 =116
340 =113
330 =110
320 =107
310 =103
300 =100
290 = 97
280 = 94
270 = 90
260 = 87
250 = 83
240 = 80
230 = 77
220 = 73
210 = 70
200 = 67
190 = 63
180 = 60
170 = 57
160 = 53
150 = 50
140 = 47
130 = 43
120 = 40
110 = 37
100 = 33
Continue to descend at the correct rate as shown below; to intercept the localizer.
How to calculate descent rate (v/s)
Take your GS (ground speed) and multiply it by minus 5.
-E.g 440 x -5 = -2200
Your rate of descent will change as you descend.
Your speed will either increase or decrease.
You will need to adjust your v/s.
To insure you are descending correctly use the below table.
• GS / VS
• 520 = -2600 / 500 = -2500
480 = -2400 / 460 = -2300
440 = -2200 / 420 = -2100
400 = -2000 / 380 = -1900
360 = -1800 / 340 = -1700
320 = -1600 / 300 = -1500
280 = -1400 / 260 = -1300
240 = -1200 / 220 = -1100
200 = -1000 / 180 = -900
160 = -800 / 140 = -700
120 = -600 / 100 = -500
•Insure you are using GS not airspeed.
Forumula created by @IF.Mike
Altitude/1000 x 3.5 + 10 to work our distance
Eg. FL340
34000/1000=34
34 X 3.5 = 119
119+10=129
And this is at a constant -1,500VS
KISS indeed, this is why I work on a rule of thumb principle for speeds, when you to use flaps, when to descend and VS speeds to use. Years ago I produced a quick cheat sheet as a QR, it’s on my old computer so I think I will have to write it out again.
Seems it’s been covered well already for for descent rates the rule of 3 is a good starting point.
Say you’re cruising at FL350 then as a rule of thumb 35 x 3 = 105
That means you roughly need 105 miles from your destination to descend.
In terms of regulating your vertical speed, a 3° descent profile is based around 1/2 of your ground speed.
G/S 420kt then vertical speed should be 2100ft/min
So from FL350 at 420kt ground speed I’d suggest 115mi (accounting for winds etc) and a vertical speed initially of 2100ft/min adjusting accordingly for your ground speed which will reduce the lower you go.
Past FL150 I’d suggest dialling back to 250kt so you’re on the money for passing FL100 but you will or should maintain inertia whilst descending so fuel burn should be reduced.
This tends to be called a continuous descent approach (CDA).
Once you’re below FL100 and on a STAR then the chart will offer guidance about altitudes and speeds which then can be adjusted accordingly.
Hope you find this useful.
I guess we all have thumbs and all manage to bring oir plane down eventually!
In my case, it all depends whether I need to speed things up (late and fast descent) or slow them down (early slowish descent) according to my RL situation ;)
Well, what I do is quite different, here are my steps!
2.Multiply that number by 3 (32 x 3 = 96)
3.Round that number (96~100)
Add 10 (for crosswinds etc 110)
Start to descend 110 nautical miles with VS between -1800 to 2000.
I hope it helps! Correct me if I’m wrong of course!
So, what I do is I take my arrival airport’s elevation and add 3,000. I subtract that number from my cruising altitude. I then divide that number by the V/S I want to descend at (usually -1500 for me). Subtract 1 from that number and multiply the decimal part by 60. That new number is basically the time ETE that you start descent.
For example, let’s say we are approaching KSEA at 35,000 feet. KSEA’s elevation is 433 feet. We subtract 3,433 from 35,000 to get 31,567. Divide that by 1500 to get 21.04. Subtracting one and multiplying the decimal by 60 brings us to 20.02. Begin your descent 20:02 away.
Speeds
270 KIAS under 20,000
260 KIAS under 15,000
240 KIAS under 12,000
Then, just eyeball it until landing.
This is how I’ve done it and it’s never overshot or come short. Also, you can use the altitude “banana” on the map for help.
Let me know if you have any questions!
That sounds like a good method. I might try that.
A flight instructor told me something similar to this
Awesome! Have fun flying!
pro gamer moves 100
Thats a great method!