Hi there to the community!:)
This is a question that I have making to me until I started to play if, so if you guys know a way to descend, feel free to leave it in the comments. Sorry if the presentation is a little bad, I am new here:).
One way that i use for long haul it’s the next:
1st- I Take my altitude to Floor level (FL)
The acreage descend speed is 200kts, so if my speed is 270kts, then I have to lose 70kts
If I have a tail wind of 30kts, I divide 30:10=3NM
•Dividing by 10 it’s just a way to convert the components in NM:)
4-Add the facts
116NM gotten from the altitude
+7NM from the speed
3NM from the cross wind
Is equal to 126NM before airport
5th-Now for easier calculations
120:200which is the average speed=0.6=35min
Hi there to the community!:)
I don’t understand your question
She’s/He’s explaining how he/she calculates his/her descents.
I too have the same question … Thank you @JuanCrafter_Pro for portraying the question so well. I hope someone will clear our doubts
I mean if you guys know a way different from mine to calcule when to descend, that was my question
Thank you for reading, i really appreciate your comment!
3 times your height for descent point. Plus or minus a bit for wind.
Half your ground speed for descent rate (480/2 = 240 so 2400fpm).
That’ll give you a good 3 degree descent path.
Pretty sure it’s Flight Level
From TOD to 11k or 10k (just to make sure Speed is below 250 KIAS before going lower, shoot for a spot 30 nm from intercept):
(Altitude to lose * GS) / (V/S * 60) = DME from chosen spot to begin descent
As you’re descending and GS decreases, you may need to adjust your V/S:
(Altitude left to lose * GS) / DME to target / 60 = Required V/S
I see a ton of descent calculations here, but anything which doesn’t account for GS isn’t going to be anything more than a rough estimate.
30 Knots divided by 10 (no units) equals 3 knots. It doesn’t magically convert units.
Well, I’m a noob, so I wish one day I could apply your descend technique with wind calculations like that guy Capt’n Joe. But here’s mine, and since you ask for “a way” my answer won’t be pure maths, it never failed me not even once as I descend in two steps:
(Current Alt - Target Alt)/time = V/S
*Time is time needed at current speed to get to any two waypoints you wanna get from and to.
- So first I will always set target above 10,000 feet, like FL150 - FL120 so I could set things ready and check my speed in a safe height (Avoiding violations… AND check AGL for surrounding terrain).
Always know your terrain!
If I have another device I will check target terrain in an unfamiliar territory using liveflightapp, in case a plan B, i.e. a Descend Pattern would be needed (when you won’t have ATC to guide you). It saved my IF live once above Southern Java island! :D
During a first descend, I don’t care if my V/S exceeds 1,600 …as long as the passengers don’t complain :p
- Now with the new slower speed at your first target alt and waypoint, check time again (time needed to get to your next and final target - the airport cone approach at 3000 feet). I’ll be doing a second calculation to meet the localizer at Target Alt FL30 (plus airport height when applicable). Excited as always to hear IF-A stewardess letting know passengers we’re on a descend. Turn on the seatbelt sign and away we go!
And I always set a rule (depends on type of aircraft as well tho), that rule is:
If V/S is above 1,600 ft/min…
Then I’m in for a possible trouble ahead - a miss approach or possible speed violation or both.
So I’ll revisit my waypoints and see what other options I have. I could actually calculate roughly these two steps even as I’m still on initial climb with hours away to destination - always plan ahead for descend, not whenever you want to.
So there you go, made it up myself and have not crashed since, ofcourse I’m open to new techniques and sugestions, but as I fly even during work hours my workmates are always amused everytime I’m on descend, timer alarm going off, math scribbles and calculations, etc… they always come to watch - except for my boss who’s sitting right next to me, “aren’t life complicated enough?!” she always says, lol!
I also read somewhere you don’t need that 3 degree angle all the time, just go nice and slow, give yourself enough time to see what’s going on at EGLL in the afternoon and decide how to enter the carnage and make friends with ATC. Hope that helps :)
I apologize, thanks for the correction as Isaí I’m new posting in the forum
Hi, could you elaborate on the first step, I’m not sure what you mean by it.
Awesome! Now will be so much easier, thank you!
Three times table is your best friend for easy and quick descent calculations for a roughly three degree descent angle that you can do in your head. As you gain experience with aircraft you fly in IF, like in my case the Q400 and 777, you learn how the aircraft flies on descent and get a better idea of what you really need. Although the Q400 has very simple descent profiles.
Stu already mentioned the three times table, but here is a clarification.
Take the difference from your current altitude to the target altitude. So say 25,000ft down to 8,000ft. The difference is 17,000ft.
17 * 3 = 51
So you’ll need 51nm to lose 17,000ft.
Rate of descent was clear enough from Stu.
Noted! Thank you:)
1st-Yoy have to covert your altitude to Flight level (FL) and then divide it by 3
2nd-Divide the speed you have to lose to get 200kts which is the average descend speed by 10
You have 280kts, then you have to lose 80kts
3rd-Divide the crosswind by 10
4th-Make a sum with the facts
So then you start your descend at 126NM:)
When you are at 126NM before airport
Divide the altitude in ft by the ETE left
At 126NM, my ETE is the 17min
I hope that in this answer I have correct my mistakes
Thank you for reading, hope that I had help others