Wind effect on descent A320

[easymxp]

Hi!

I’m trying to find an easy rule of thumb to monitor my descent with significant tailwind on descent.
let’s assume tailwind is 50 knots at TOD, normally I use 3*altitude plus deceleration plus tailwind. For tailwind I use 1nm each 10knots of tailwind. I see this works with a high speed descent (say over 300 knots) but with our CI we have around 270 and it is not enough. Anyone with a better estimation of wind effects on descent computation?

If asking why I do all this when I have managed des , is bcs with trombone style arrivals (snake) most of the times I get major shortcut so to mitigate this I use OP des and stay lower

[enzino]

I operate out of another airport with those RNAV STARs, and to be fair the first altitude constraints work. I fly in managed descent until that point, then depending on what I perceive in terms of air traffic load, I use selected modes. This has worked well for me in places like FCO, BER, BCN, etc.

And I always insert descent forecast winds.

[KingAir1978]

Originally Posted by easymxp

Hi!

I’m trying to find an easy rule of thumb to monitor my descent with significant tailwind on descent.
let’s assume tailwind is 50 knots at TOD, normally I use 3*altitude plus deceleration plus tailwind. For tailwind I use 1nm each 10knots of tailwind. I see this works with a high speed descent (say over 300 knots) but with our CI we have around 270 and it is not enough. Anyone with a better estimation of wind effects on descent computation?

If asking why I do all this when I have managed des , is bcs with trombone style arrivals (snake) most of the times I get major shortcut so to mitigate this I use OP des and stay lower

I find that the bus generally does a pretty good job with the profile. But... garbage in ==> garbage out. A "Trick" that I sometimes use during the descent preparation is to copy the active Flight plan into the secondary flight plan. Now I modify the secondary flight plan, into what I think we would REALLY get, in terms of ATC clearance. If you expect to fly from position X directly to the final fix, I would modify it (in the secondary) into that. If you now look back through the secondary flight plan you can take another point (before point X) and look at the predicted altitude/speed. You can make THAT altitude/speed combination a restriction in the PRIMARY flight plan. This way the 'bus will calculate an idle descent to that first restriction. You now have an accurate TOD... Hope this helps.

With regards to a rule of thumb 10 kts of tailwind adds about 1 nm... Obviously if you fly slower, you will spend MORE time in the tailwind condition, but the wind usually decreases with altitude...

[Amadis of Gaul]

Originally Posted by easymxp

Hi!

I’m trying to find an easy rule of thumb to monitor my descent with significant tailwind on descent.
let’s assume tailwind is 50 knots at TOD, normally I use 3*altitude plus deceleration plus tailwind. For tailwind I use 1nm each 10knots of tailwind. I see this works with a high speed descent (say over 300 knots) but with our CI we have around 270 and it is not enough. Anyone with a better estimation of wind effects on descent computation?

If asking why I do all this when I have managed des , is bcs with trombone style arrivals (snake) most of the times I get major shortcut so to mitigate this I use OP des and stay lower

I am not very smart, so I just use the 3:1 rule, wind be damned, works out pretty well the vast majority of the time. I feel like people who feel the need to complicate this any more than that are the same people whose coffee order at Starbucks is at least fifteen words.

10 years in the 320 series now, in case that matters.

[CaptainMongo]

Originally Posted by Amadis of Gaul

I am not very smart, so I just use the 3:1 rule, wind be damned, works out pretty well the vast majority of the time. I feel like people who feel the need to complicate this any more than that are the same people whose coffee order at Starbucks is at least fifteen words.

10 years in the 320 series now, in case that matters.

Agreed, I’m not smart but I am old.

I plan for what I filed. If ATC gives us a shortcut or early speed reduction on a STAR which creates a problem with a restriction I just ask them if they want the altitude or airspeed at the next point (cause they aren’t going to get both)

[Capn Bloggs]

Originally Posted by Mongo

I just ask them if they want the altitude or airspeed at the next point (cause they aren’t going to get both)

​​​​​​​Doesn't the scarebus have a speedbrake.

[sonicbum]

Originally Posted by easymxp

Hi!

I’m trying to find an easy rule of thumb to monitor my descent with significant tailwind on descent.
let’s assume tailwind is 50 knots at TOD, normally I use 3*altitude plus deceleration plus tailwind. For tailwind I use 1nm each 10knots of tailwind. I see this works with a high speed descent (say over 300 knots) but with our CI we have around 270 and it is not enough. Anyone with a better estimation of wind effects on descent computation?

If asking why I do all this when I have managed des , is bcs with trombone style arrivals (snake) most of the times I get major shortcut so to mitigate this I use OP des and stay lower

Hi,

your rule of thumb is good enough. What you can do is to descend in such a way that you will be A) able for a direct to the FAF at any point during the arrival and B) still able to fly the full start without flying levelled for too many miles.

Tip 1) check the historical statistical contingency fuel values for your sector, and if available on your EFB, the statistical approach paths. In this way you will be aware of what you will most likely be flying in terms of STAR hence being able to plan the appropriare shortcut.

Tip 2) Same as above but add FR24 to the equation; check previous historical flight tracks.

Tip 3) Always have in view the PROG page with the runway threshold on PF side and the FPLN on PM side. In terms of energy management consider to fly something in the middle in terms of track miles. I.e. PROG is 100nm, FPLN is 150NM, plan something around 120NM to run. This way you will able for both profiles.

Tip 4) If you are high, no problems. Remember in aviation altitude and speed are a luxury, as no one has ever hit the sky. Increase ROD by increasing IAS and extending the speedbrakes. If it still looks “meh” ask for more track miles to loose altitude. Next time you will do it differently.
Remember altitude and fuel = options. Landing out of an unstable approach with several hundred kgs of extra fuel is not clever. Use it.

[oicur12.again]

Originally Posted by Amadis of Gaul

I am not very smart, so I just use the 3:1 rule, wind be damned, works out pretty well the vast majority of the time. I feel like people who feel the need to complicate this any more than that are the same people whose coffee order at Starbucks is at least fifteen words.

10 years in the 320 series now, in case that matters.

Wind be damned. Interesting technique. You must be rather well versed in the use of speedbrakes or V/S.

And hopefully you are not paying the fuel bill!

What you call a need to “complicate” many would call . . . . professionalism.

[pineteam]

Just wanna share a tips a FO shared with me Yesterday using the ISIS. We all know the basic rules of altitude * 3 + (10 optional ) or track miles to go * 3 work very well. I have been using this for the last 10 years and it’s all you need really... If your mental maths s*ck or you are tired, what you can do is to look at your ISIS and check the altitude in Meters and take the first 2 digits and it will tell you how many track miles you need until landing. For example if you are at 22000 feet you need 22 * 3 = 66nm required or 22 *3+ 10 = 76 nm required. If you look at the altitude in Meters it will be roughly 6700 meters, you just look at the first 2 digits and voilà!—> 67 nm! If you want to be conservative or new on jet aircraft or super heavy and strong tail wind you can add +10= 77nm. And it works all the times since 1 meter = 3.28 feet. Which is close enough to the 1 to 3 rules. I personally do not add + 10 unless very strong tail wind as I rather be too high than too low to stay on idle all the way. I will add one nm per 10kt I need to decelerate to reach green dot. If you are too high you can always speed up (unless ATC restrictions) or use speed brakes at last resort which will give you an angle of descent much more than 3 degrees ( usually around 4/5 degrees) and therefore bring you back to your profile rapidly.

[Amadis of Gaul]

Originally Posted by oicur12.again

Wind be damned. Interesting technique. You must be rather well versed in the use of speedbrakes or V/S.

Quite so. If I need the boards, I use the boards. If I need V/S, I use that. I'm not married to managed descent. What can I say, I must just be an amateur.