Takeoff: Retracting from CONF 1 to 0

[David1991]

Hey guys, about to start a Type Rating 320 soon doing some pre-study.

I have a question regarding flap/slat retraction during a heavy takeoff.

Conditions:

-max speed on SID 220
-S speed at 208
-Green Dot at 223 kts

1. with S being the min slat retraction speed why am I not allowed to select Flaps 0 after passing S speed + a positive trend vector? Why do I have to wait after the speed restriction has been passed in order to reach green dot? Is S speed just defining the speed where you can retract to 0 and with having positive acceleration it will fit perfectly to reach green dot speed when finished

2. how would you manage this situation?

I was thinking about pre-selecting/pulling Speed to 205kn avoiding auto flap retraction..then after passing the speed restriction order „manage speed“ and retract the flaps to 0?

thank you indeed!

[FlightDetent]

The way you set up the question makes it easier.

A) Retract at S and pull speed for 220kts. Fly at GD minus 3 kt where VLS will be approx 205, where GD is the best EO speed.

B) select speed 220 or keep managed and don't retract anything. The auto F1 to F0 will happen at 210, useful.

C) ask clearly and directly for speed 230 from ATC. (pending turn trajectory and boundary area consequences.

Indeed the case can be built more on the edge, speedwise.



Though you may be looking for another piece to fill the puzzle from the original dilemma.
=
​​​​​With S+F at 0, the FMGS will disregard any max speed constraint below GD and target the GD instead.

Enjoy, good knowledge is power.
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[Check Airman]

Hey guys, about to start a Type Rating 320 soon doing some pre-study.

I have a question regarding flap/slat retraction during a heavy takeoff.

Conditions:

-max speed on SID 220
-S speed at 208
-Green Dot at 223 kts

2. how would you manage this situation?



2. Clean up as normal and fly at green dot.

[hans brinker]

Hey guys, about to start a Type Rating 320 soon doing some pre-study.

I have a question regarding flap/slat retraction during a heavy takeoff.

Conditions:

-max speed on SID 220
-S speed at 208
-Green Dot at 223 kts

1. with S being the min slat retraction speed why am I not allowed to select Flaps 0 after passing S speed + a positive trend vector? Why do I have to wait after the speed restriction has been passed in order to reach green dot? Is S speed just defining the speed where you can retract to 0 and with having positive acceleration it will fit perfectly to reach green dot speed when finished

2. how would you manage this situation?

I was thinking about pre-selecting/pulling Speed to 205kn avoiding auto flap retraction..then after passing the speed restriction order „manage speed“ and retract the flaps to 0?

thank you indeed!

It’s a max speed, so I preselect 200 before departure, wait till I’m past the constraint or get ATC clearance to go faster. At that point, manage speed, accelerate and clean up. And everyone before me had it right also. Whatever works for you & your company.

[vilas]

Hey guys, about to start a Type Rating 320 soon doing some pre-study.

I have a question regarding flap/slat retraction during a heavy takeoff.

Conditions:

-max speed on SID 220
-S speed at 208
-Green Dot at 223 kts

1. with S being the min slat retraction speed why am I not allowed to select Flaps 0 after passing S speed + a positive trend vector? Why do I have to wait after the speed restriction has been passed in order to reach green dot? Is S speed just defining the speed where you can retract to 0 and with having positive acceleration it will fit perfectly to reach green dot speed when finished

2. how would you manage this situation?

I was thinking about pre-selecting/pulling Speed to 205kn avoiding auto flap retraction..then after passing the speed restriction order „manage speed“ and retract the flaps to 0?

thank you indeed!
Put in MCDU preselect speed 220kts and after takeoff let flap auto retract then retract slat and the aircraft will automatically fly 220ks in select speed. Not much issue.

[Bula]

You don’t need to avoid Auto Retraction. In fact, it is pretty much necessary on the A321 at heavy weights.


Select 210. Let it auto retract, fly 210 until clear of the constraint.

[FlightDetent]

Hello FlightDetent, I am trying to find a reference to this in the FCOM, do you know where? My understanding is that if the constraint (eg 220KT) is below Green-dot then the aircraft will fly the constraint still? Or am I missing something somehwere?

FCOM DSC-22_30-40 "B": MANAGED SPEED/MACH TARGET

Note (3): The managed speed/Mach target may be set below maneuvering speed but as long as the speed target is managed, the FMGS limits the aircraft to the maneuvering speed of the current slats/flaps configuration (VAPP, F, S, Green Dot).

[k.swiss]

FCOM DSC-22_30-40 "B": MANAGED SPEED/MACH TARGET

Note (3): The managed speed/Mach target may be set below maneuvering speed but as long as the speed target is managed, the FMGS limits the aircraft to the maneuvering speed of the current slats/flaps configuration (VAPP, F, S, Green Dot).

Thank you for your reply, yes in the FCOM it says this but under NAV mode something else will happen.

How about this, next time check the PERF page and scroll to CLB. It says "managed target" and the constraint speed is there so I believe if under NAV mode the constraint will be obeyed regardless of configuration. If in HDG then I agree, the AC will go directly do Green Dot. The reason I want to clarify this is because I see a lot of people pre-selecting the constraint speed on takeoff.

What do you think?

[AerocatS2A]

Thank you for your reply, yes in the FCOM it says this but under NAV mode something else will happen.

How about this, next time check the PERF page and scroll to CLB. It says "managed target" and the constraint speed is there so I believe if under NAV mode the constraint will be obeyed regardless of configuration. If in HDG then I agree, the AC will go directly do Green Dot. The reason I want to clarify this is because I see a lot of people pre-selecting the constraint speed on takeoff.

What do you think?
No, even in NAV a constraint below a manoeuvring speed will not be respected. The performance page may show the speed as the constraint but when you actually get there, if the constraint is below green dot, the speed will be green dot. It's up to you to manage configuration so the constraint is achievable. On the other hand, a selected speed WILL be respected even if it is below the applicable manoeuvring speed, so if GD is 212 and the constraint is 210, it will fly 212 knots in managed but 210 knots selected. Again it is up to you to ensure the configuration is appropriate for the speed.

[k.swiss]

Yes guys, I checked it on my last flight. AC goes to GD :D my mis-interpretation.

Cheers.