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A320/A321 energy management and configuration

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A320/A321 energy management and configuration

Old 29th May 2023, 20:44
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A320/A321 energy management and configuration

Dear colleagues,

I’ve just ended my Line training on A320/A321, I’d like to ask your opinion about some thoughts about energy management. In my airline we are encouraged to use OP Des and V/S for descent planning, in order to be able to compute ourself.
My question are:
/ how many miles do you add in order to decelerate? Normally I use 3xAltitude (even if some colleagues suggest 3xdistance as this gives a shallowe profile) plus 5 miles from 250. I see this rule works very good and is even conservative if I can descend all the way down at 250, level off and decel, configure.
if I have some altitude constraints where I have to decel quite early to 210, I see I have some problems as then the gradient is very shallow and soon I go above profile…

/ If I have an intermediate altitude constraint say 20nm at 6000 how can I know how much to decel? I see in the same scenario colleagues going straight to Sspeed and F1, others maintain 250 as they say that 20nm at 6000 has its margin and descending at 250 is better as far from GDot (best lift to drag ratio) so descent is steeper.

Thanks for your help
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Old 29th May 2023, 23:01
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General Rules of Thumb

The short answer to this is all Arrivals should be via Managed DES and with the PROG page displayed. As soon as you get high above your profile, use the speed brakes. If you have a tailwind, especially on the 321, be especially attentive to the descent. V/S means Very Seldom. Some guys love it and use it like a master, but your protections are gone in V/S. Use V/S out of 12,000, speed 300, down to 8000, and you will soon be flying 300 knots below 10,000 feet, thus busting the 250 below 10,000 rule.

"Open" XXXX (climb/descent) should primarily be used with ATC says "....and maintain" with the clearance. Intermediate descents, say 350 down to 310, due to turbulence at 350, is a DES not Open Descent.

I don't get too worked up over the math I watch the intercept path symbol and descent arrows, and level off point, to manage stuff. I don't have my head in the sand, blindfully ignorant either, but I am just not doing math equations for my descents. I might use "math" for a sanity check nothing more. I am not calculating decel points or things like that.

Also, it is easier to "get down first" then slow down once you level off, versus try to slow down, AND get down. The Airbus really does not slow down and get down well at the same time.

If in the airport environment aka "talking to Approach" and speed 210, go to Flaps 1. Downwind is typically speed 210. Base turn, speed 170-180, Flaps 2.

Watch the VLS with spoilers out, some instructors will tell you "it doesn't matter" if you airspeed enters VLS, others will break your kneecaps if VLS touches your present speed. Speed 210 with Flaps 1 largely mitigates that.

Again, general rules of thumb. Adjust for the operational situation at hand.




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Old 30th May 2023, 14:36
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Originally Posted by FM_A320
Dear colleagues,

I’ve just ended my Line training on A320/A321, I’d like to ask your opinion about some thoughts about energy management. In my airline we are encouraged to use OP Des and V/S for descent planning, in order to be able to compute ourself.
My question are:
/ how many miles do you add in order to decelerate? Normally I use 3xAltitude (even if some colleagues suggest 3xdistance as this gives a shallowe profile) plus 5 miles from 250. I see this rule works very good and is even conservative if I can descend all the way down at 250, level off and decel, configure.
if I have some altitude constraints where I have to decel quite early to 210, I see I have some problems as then the gradient is very shallow and soon I go above profile…

/ If I have an intermediate altitude constraint say 20nm at 6000 how can I know how much to decel? I see in the same scenario colleagues going straight to Sspeed and F1, others maintain 250 as they say that 20nm at 6000 has its margin and descending at 250 is better as far from GDot (best lift to drag ratio) so descent is steeper.

Thanks for your help
Hi,

First off all congratulations for having successfully completed your line training! A little less congratulations for your trainers that have left you with those unanswered questions

Let's look at a basic but effective descent management tool.

The good old Altitude x 3 to start with.
Then adjust the wind -> +/- 10% tail/head winds
Then adjust the speed + 1 NM for every 10 kt above 200 kt which is usually somewhere around Gdot.
Finally the weight adjustment. On the narrow body Airbus I don't bother too much; if I am very light I will probably need to reduce the RoD at some stage and if I am close to Max Landing Weight I might need to use some speed brakes.

So You need to start your descent from FL350 down to your platform of, let's say, 3000 ft.
32 x 3 = 96 NM
20 kt tailwind = +2 NM
Deceleration = 7 NM (descending at 270 kt)
Start descent in OP DES around 105 NM.
From there keep calculating and adjust, every 5000 feet or so. If you do have STAR constraints to meet in the middle you will need to set targets for the different constraints.

Generally speaking this sort of technique of descending in OP DES/VS works well to optimize fuel consumption when there are not too many constraints to be considered.
It is a "homemade" version of the Descent Profile Optimization by Airbus and can lead to some savings if applied correctly.
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Old 30th May 2023, 15:19
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321XLR I don’t know what protections you are talking about. You are fully protected in V/S mode. Perhaps you mean mode reversions, they are described in DSC 22_30-40-110
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Old 30th May 2023, 16:39
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Originally Posted by tubby linton
321XLR I don’t know what protections you are talking about. You are fully protected in V/S mode. Perhaps you mean mode reversions, they are described in DSC 22_30-40-110
I think he meant that when you go on V/S plane will keep ROD and speed could keep increasing during descent if you ask for too much v/s, and go faster than atc/company restrictions. Whereas in OP DES ROD will reduce to try to maintain the desired speed.
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Old 30th May 2023, 18:00
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Originally Posted by sonicbum
Hi,

First off all congratulations for having successfully completed your line training! A little less congratulations for your trainers that have left you with those unanswered questions

Let's look at a basic but effective descent management tool.

The good old Altitude x 3 to start with.
Then adjust the wind -> +/- 10% tail/head winds
Then adjust the speed + 1 NM for every 10 kt above 200 kt which is usually somewhere around Gdot.
Finally the weight adjustment. On the narrow body Airbus I don't bother too much; if I am very light I will probably need to reduce the RoD at some stage and if I am close to Max Landing Weight I might need to use some speed brakes.

So You need to start your descent from FL350 down to your platform of, let's say, 3000 ft.
32 x 3 = 96 NM
20 kt tailwind = +2 NM
Deceleration = 7 NM (descending at 270 kt)
Start descent in OP DES around 105 NM.
From there keep calculating and adjust, every 5000 feet or so. If you do have STAR constraints to meet in the middle you will need to set targets for the different constraints.

Generally speaking this sort of technique of descending in OP DES/VS works well to optimize fuel consumption when there are not too many constraints to be considered.
It is a "homemade" version of the Descent Profile Optimization by Airbus and can lead to some savings if applied correctly.
Thank you very much!
Unfortunately during training I see some captains are not really able to transmit those things, on energy management sometimes they just rely on experience and feeling in order to judge descent and configuration, which is obviously perfect and normal after many hours, but for a fresh new pilot cadet level some rules of thumb and guidance are still required, as experienced needs to be built…
Thank you for your help, I’ll try. Sometimes I get a common restriction with 9000/29 nm before joining an arc dme and descending on the arc. I reduce to speed 210 and then maintain this speed in order to avoid overshooting. When descending gradually I see losing miles (especially with 10kts tailwind), I try to solve going F1 speed 210 and sbrake but it’s not really efficient and couple of times had to use the gear… Not nice that feeling of rush thinking “will I make it or not” Probably also the plane makes the difference… some of them look very reluctant to descend steep

Thanks again for the help.
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Old 30th May 2023, 18:57
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Originally Posted by snl13
I think he meant that when you go on V/S plane will keep ROD and speed could keep increasing during descent if you ask for too much v/s, and go faster than atc/company restrictions. Whereas in OP DES ROD will reduce to try to maintain the desired speed.
That used to be called airmanship and managing the platform in my day. The FCTM stated 250kt/ 9000 feet above the airfield at 30nm. When I first started flying Airbus every approach was meant to be a decelerated approach and taking flap as soon as you got to target speed as long as you were on the profile. The FCTM seems to have taken out some of this info but it states that the typical descent is based upon n FPA of 2.5degrees.
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Old 30th May 2023, 19:33
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Originally Posted by tubby linton
That used to be called airmanship and managing the platform in my day. The FCTM stated 250kt/ 9000 feet above the airfield at 30nm. When I first started flying Airbus every approach was meant to be a decelerated approach and taking flap as soon as you got to target speed as long as you were on the profile. The FCTM seems to have taken out some of this info but it states that the typical descent is based upon n FPA of 2.5degrees.
I agree a common figure, also in the FCTM and many Airbus FOBN is 250/9000/30. Tbh a part from descent with light weight and a normal amount of headwind I feel on the high side at this distance and height. 9000 at 33nm is generally a better starting point, but I play maybe in the conservative side.
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Old 31st May 2023, 06:42
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Originally Posted by FM_A320
Thank you very much!
Unfortunately during training I see some captains are not really able to transmit those things, on energy management sometimes they just rely on experience and feeling in order to judge descent and configuration, which is obviously perfect and normal after many hours, but for a fresh new pilot cadet level some rules of thumb and guidance are still required, as experienced needs to be built…
Thank you for your help, I’ll try. Sometimes I get a common restriction with 9000/29 nm before joining an arc dme and descending on the arc. I reduce to speed 210 and then maintain this speed in order to avoid overshooting. When descending gradually I see losing miles (especially with 10kts tailwind), I try to solve going F1 speed 210 and sbrake but it’s not really efficient and couple of times had to use the gear… Not nice that feeling of rush thinking “will I make it or not” Probably also the plane makes the difference… some of them look very reluctant to descend steep

Thanks again for the help.
No worries.

Next time take your 9000 ft as your aiming point and calculate from there. You should end up there with Gdot ready for your arc.

To crosscheck how you are doing during descent also use the "official" Airbus formula:
Required Dist to descend = Diff. in FL / FPA
I.e. I am passing FL250 descending FL90 or 9000 ft like in your case so that's a Delta of 160 divided by what the bird shows, let's say 4° probably -> 40NM needed bare minimum distance. That's where all the psychometrics pain in the a°rs math tests come in handy

You can monitor you current FPA in Descent by occasionally going bird ON and see how you are doing.

As a general rule try to correct your descent profile while still far from the target as you will have many more tools, such as increasing your IAS and using speedbrakes. This combination can double your descent gradient when you're still far out and can afford higher rates of descent and speeds.
Below FL100 you will mostly be on a 3° descent on idle thrust, that you can increase by adding speed brakes and bring it up to even 7° by going full manual speed brakes at 250 kt but there are some threats involved in doing that (high rate of descent below FL100, manual flying with tunnel vision). So I would recommend to keep your AP on and accept the half speed brake of the A320.

During your next flight go Bird ON from time to time during descent and see how the aircraft behaves at different levels, how air density variations and wind changes affect your descent gradient. That should help
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Old 31st May 2023, 11:02
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First caveat-I'm not an Airbus pilot. I have been around a very long time though and as I see it your best way to learn is to glean all the worthwhile info from threads like this.

Plan EVERY descent, even as PM fly it in your mind, so that you will build an experience base to work from.

When you are PF fix any errors you see as soon as you see them. Say you're high and fast around 10,000 ft, fix it now don't hope it gets better. You may be wrong with your fix and it would have fixed itself but you demonstrate to any watchers that you have a plan and are aware of variations. This is the stuff that makes aviation interesting and worth doing, the fact that the air is unpredictable.

Accept that even after 45 years you will NOT know it all and keep learning and enjoying the way that things almost invariably change. That's what I did and enjoyed my career immensely.

Good luck!!
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Old 31st May 2023, 20:07
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Generally altitude x 3 times with 1 nm per 10 kt reduce in the speed works well in my experience but what I did (and actually still do is); I enter the runway or the faf to the PROG page and make all the calculations and planning aloud, like "ok we have xx nm to faf, we are at xx feet, we are high/low, I will do this/that", then as written above everyone in the cockpit knows you are aware of the situation and have a plan, and secondly everyone will share their experiences based on the situation.
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Old 13th Jun 2023, 09:43
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Originally Posted by FM_A320
how many miles do you add in order to decelerate? Normally I use 3xAltitude (even if some colleagues suggest 3xdistance as this gives a shallowe profile) plus 5 miles from 250. I see this rule works very good and is even conservative if I can descend all the way down at 250, level off and decel, configure.
Hi,
The more correct formula is "altitude/slope = distance". Altitude x3 puts you on a 3.33° slope (approx) so is indeed steeper.
A good rule of thumb is to add 5 miles for 320kt to 250, and another 5 miles for 250kt to under VFE2.

If you're about 500-700ft above profile you should be more than okay for a decelerated approach (at least on my FMS standard which wants to do an early stabilized..)

If you're (very) high, it's usually best to slow speed first, get flaps 2, full spoilers (sometimes gear down even) and then dive. This will give you almost 10 degrees..

To avoid unstabilzed approaches, I put the runway in prog page and don't turn to base then final unless my altitude is lower than distance x 3 + 1000ft (to account for the turn)

You can also compute your own FPA. Compute your nautical miles per minute first : 120kt is 2 nm/min, 180 is 3 and so on. Just use the nearest figure, closest to your ground speed. Then, there is 100fpm for each degree and each nm/min. For example at 240kt, if you want to go down by one degree, you need 400fpm.
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Old 12th Sep 2023, 12:00
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Hello everyone,

Thanks to all your advices my descent management has significantly improved. With 3*Altitude + 1nm each 10kts to lose down to 200 (+\- wind adjustment) descent goes really fine. Just one question. Sometimes ATC asks me 210 quite early due to traffic sequencing, especially at heavy weights this can give some troubles as gradient is shallower and S/brakes are very limited due to VLS (unless I use Flaps). When you expect 210 very early due you still use 3xAlt to monitor your descent, and if you start drifting high you go F1 + Sbrakes or you modify your computation to allow for this?
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Old 12th Sep 2023, 18:16
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OP DES is faster than DES even if “THR IDLE” is shown on both.
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Old 4th Oct 2023, 18:06
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This information is quite valuable; thank you for sharing.
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Old 5th Oct 2023, 14:49
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keep in mind OPEN DESCENT up at cruise altitudes is basically a rock falling out of the sky and may trigger some TCAS alerts due to "excessive descent rate" and closure rate calculations with out traffic

I personally dont really use it unless below 18,000

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Old 10th Oct 2023, 22:42
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What I find interesting about this question is that it gets asked all the time, and every time it's like someone is discovering something new. Personally, I'm not particularly smart, so I just use straight 3:1 rule. Has worked peachy in every type I've flown. Mind you, I am a big-time overthinker by nature, but not in this case.
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Old 11th Oct 2023, 03:49
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Originally Posted by Fursty Ferret
OP DES is faster than DES even if “THR IDLE” is shown on both.
Have you compared fuel flow for both when THR IDLE is displayed? If the FF is the same, the descent rate has to be the same for the same speed.

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Old 11th Oct 2023, 04:11
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Originally Posted by hans brinker
Have you compared fuel flow for both when THR IDLE is displayed? If the FF is the same, the descent rate has to be the same for the same speed.
I don't know whether it's true now because lot of changes take place. Previously managed descent thrust idle fuel flow was at anti ice on fuel flow to keep predictions accurate should anti ice be required. OP DES was normal idle. That's why the difference.
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Old 5th Mar 2024, 14:36
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Originally Posted by sonicbum
No worries.

Next time take your 9000 ft as your aiming point and calculate from there. You should end up there with Gdot ready for your arc.

To crosscheck how you are doing during descent also use the "official" Airbus formula:
Required Dist to descend = Diff. in FL / FPA
I.e. I am passing FL250 descending FL90 or 9000 ft like in your case so that's a Delta of 160 divided by what the bird shows, let's say 4° probably -> 40NM needed bare minimum distance. That's where all the psychometrics pain in the a°rs math tests come in handy

You can monitor you current FPA in Descent by occasionally going bird ON and see how you are doing.

As a general rule try to correct your descent profile while still far from the target as you will have many more tools, such as increasing your IAS and using speedbrakes. This combination can double your descent gradient when you're still far out and can afford higher rates of descent and speeds.
Below FL100 you will mostly be on a 3° descent on idle thrust, that you can increase by adding speed brakes and bring it up to even 7° by going full manual speed brakes at 250 kt but there are some threats involved in doing that (high rate of descent below FL100, manual flying with tunnel vision). So I would recommend to keep your AP on and accept the half speed brake of the A320.

During your next flight go Bird ON from time to time during descent and see how the aircraft behaves at different levels, how air density variations and wind changes affect your descent gradient. That should help
very interesting. More or less what the DPO does. But do you think on most A320 Ceo at 210 (or very close to GDot) you will be able to descend on a 3°? So 210/6000/19, 210/5000/16? I see most of the times it’s slightly shallower than 3° and deceleration takes longer….
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