And the paragraph before the last quote

"Under normal law, when the angle-of-attack becomes greater than αprot, the system switches elevator control from normal mode to a protection mode, in which the angle-of-attack is proportional to sidestick deflection. That is, in the αprot range, from α prot to αMAX, the sidestick commands α directly. However, the angle-of-attack will not exceed αMAX, even if the pilot gently pulls the sidestick all the way back. If the pilot releases the sidestick, the angle-of-attack returns to αprot and stays there. This protection against stall and windshear has priority over all other protections. The autopilot disconnects at α prot + 1 °."

Well, will come back to all this later: just these questions:

How do we leave Alpha protection? Ok, agreed. The elevators simply pitch down the plane. (By the way, you say that the plane will return to normal law but even during Vprot, the plane is in normal law.).

Will the elevators pitch UP at VLS or something like that?
When does the elevator STOP pitching DOWN??

At VMO/MMO protection, I think that the plane will pitch UP only if we release the stick.

But, I have already asked these questions few months ago.
See what Flight Detent has answered!

Answer #3: " You fly level, with stick released, and set throttles to idle. The aircraft will start decelerating toward speed Valpha prot (the yellow band). At Vaprot the low speed protection activates, and in order not to go any slower, the aircraft will pitch down to maintain Vaprot."

He clearly says "MAINTAIN Vaprot."

But I still have a doubt so I ask him in QUESTIONS AT LEVEL N°4:
" Will "that" speed be managed by pitch?"

---> "that speed" = Vaprot.

His answer #7:

" Yes, the aircraft will pitch up or down to maintaint V alphaprot."

You can just check all this page 1! ;)

Well, I think that Flight Detent is a real airline pilot.

Thanks

haha that must make me a fake airline pilot??

Flight detent is quite right, it will maintain v.a.prot in that situation. But until when is the question? I had thought protection will stop as soon as the aircraft accelerates faster than v.a.prot (Either by increased thrust or pilot pitching down), until I read that in fact high AoA protection needs to be disengaged. Now it is a bit of a grey area for me. To be honest, I have never tried this in the aircraft or sim.

"Will the elevators pitch UP at VLS or something like that? "
Why would they do that? Seems counterintuitive to me.

"When does the elevator STOP pitching DOWN??"
When the airspeed is stable at V.a.prot. It is maintaining that speed, remember?

Hi,

Happy new year!! ;)

Ok, so you agree with me now.
What if A/THR is ON when we hit Vprot? A/THR will still try to manage the selected target, isn't it? So no Vprot managed by ELAC, hein?

Regards,
AF330

Happy new year!

The elac will pitch down to avoid going below v.a.prot, REGARDLESS of what athr is doing.

Good morning!

Thanks,

So if I mix your and Flight Detent's knowledge, it gives me this:

Flight Detent: When the plane reaches Vprot, the ELAC pitches down and maintains Vprot. We can override it by pulling up. The "plane" will pitch up and down to maintain Vprot

AF330: The plane? Hmm... But what If A/THR is OFF?

Dupre: ELAC will maintain Vprot. ELAC knows it's IAS and the plane's load factor. It maintains Vprot.

AF330: Ok...and what if A/THR ON at Vprot?

Dupre: ELAC has been programmed and knows if A/THR is ON or OFF. If A/THR is ON:
ELAC will pitch down at X° (programmed value). A/THR will keep managing the target speed TILL AoA Alpha floor where FAC's will ask to give A/THR full TOGA thrust.

AF330: What If we try to disconnect A/THR while Alpha floor?

Dupre: Here is what we can read on the FMA:

A.FLOOR - which means that we ARE at AoA Alpha Floor. We get TOGA from A/THR but we can't disconnect it.
TOGA LCK: We can disconnect A/THR - Even If we are at Vprot (Vprot protection will activate)

Do you agree with this now? ;)

Just waiting for your confirmation!

Regards,
AF330

You have mis-quoted me here... I never said "ELAC has been programmed and knows if A/THR is ON or OFF. If A/THR is ON:
ELAC will pitch down at X° (programmed value). A/THR will keep managing the target speed TILL AoA Alpha floor where FAC's will ask to give A/THR full TOGA thrust."

The ELAC knows nothing of autothrust, manual thrust or anything to do with the engines. When V.a.prot is reached, the ELAC does not pitch down a programmed value, but just enough to ensure that airspeed does not fall below V.a.prot. It does this REGARDLESS of thrust setting, and whether or not autothrust is engaged.

Separately, the Autothrust (if engaged) will still be trying to give sufficient thrust to accelerate to the target speed. That is, until (as you correctly state) Alpha Floor, at which time Autothrust commands TOGA.

Other than that, I agree.

Yes but when A/THR is OFF, ELAC maintains Vprot by pitching up and down.

If A/THR is ON, it would mean that both systems (ELAC/ATHR) are trying to manage 2 different speeds.

So in any case, ELAC should know if A/THR is ON or NOT.
2nd option: FAC is telling to ELAC if it has manage Vprot (A/THR OFF) or simply pitch sown and maintain any speed over Vprot (A/THR ON).

If ELAC doesn't know what A/THR is doing when A/THR is ON...sounds impossible...

The speed autothrust is trying to attain is always more than V.a.prot. If the thrust were sufficient, you wouldn't be at V.a.prot in the first place. Autothrust doesn't forget about it's target speed just because you are so slow that the protection is pushing the nose down.

This protection is completely independent of the autothrust. Remember the autothrust has no control of pitch.

The inputs into the ELACs are: (from the FCOM Flight Control Schematics)

- ON/OFF switches
- Sidesticks
- FMGCs
- ADIRUs
- SFCCs
- LGCIUs
- Hydraulic Pressure
- RAs (roll only)
- Accelerometer (Pitch only - not sure what this is)
- Rudder Pedals (Yaw only)

I am lost....

A/THR has no control of pitch??? CLB mode = Speed managed by pitching up and down. And if A/THR is still ON, it means that your speed is not very slow.

Flight Detent says that the plane maintains Vprot.

So if Vprot = 140kts , ELAC will maintain 140kts.
ELAC won't maintain a speed > 140kts

Ok, so how does ELAC know when to maintain a speed > 140kts and when to maintain a speed = Vprot???

Remember, FMGS = A/THR. A/THR system is part of FMGS.

In CLB mode, autothrust sets THR CLB. That is a fixed thrust mode. The control of the pitch (to maintain airspeed in the climb) is the responsibility of the ELAC, following the guidance of the FDs, which is computed by the FMGS.

So yes, the Athr has no control over pitch.


The question that I am not 100% sure of (and will try out if at my next recurrency sim) is this:
Aircraft in level flight. Reduce thrust to idle, speed reduces, protection engages and nose drops to maintain V.a.prot.
Increase thrust to CLB thrust... but do not touch the stick.
One of two things can happen.
1) Aircraft accelerates quickly, and maintains 1g, essentially maintaining its previous trajectory.
2) Aircraft maintains V.a.prot, but due to the increased thrust, and the fact that I have not disconnected the protection (by using forward stick), aircraft pitches up into a steep climb, still maintaining V.a.prot.

I would have thought that (1) was the obvious option, but now having read more, I am not entirely sure.


"Remember, FMGS = A/THR. A/THR system is part of FMGS." - Touche! But I still don't believe that the ELAC knows or cares about the status of the Athr.


"Ok, so how does ELAC know when to maintain a speed > 140kts and when to maintain a speed = Vprot??? "
The ELAC is only responsible for maintaining airspeed in the following modes:
-High AoA protection
-High speed protection
-SRS
-CLB/OP CLB
-DES/OP DES
So in our case, with AP/FDs off, when we have accelerated out of the high AoA protection (speed > V.a.prot), the ELAC is not maintaining any speed at all. It is just flying straight ahead until we move the stick.

Do you mean that in climb mode, AP/FD has to manage and control the speed? I had thought that A/THR will send to the AP/FD the pitch the plane should have...Do you mean that in this case, FM will send the pitch the plane should have to manage the speed??? So basically FM is managing the speed?

2) NO, in any case you will have AP OFF at Vprot (Vprot - 1kt).
The plane will PITCH DOWN and KEEP Vprot. It won't just keep pitching down.

We are going no where now...

Ok, example:

- Normal law.
- A/THR ON.
- Target Speed 170kts.
- AP/FD OFF

Pilot pulls the stick.

- Plane hits Vprot = 145kts
- Plane pitches down. ELAC knows it.

1) Now, one question: After pitching down - what speed will the plane try to keep?
Choice 1: 170kts
Choice 2: 145kts.

Example 2:

- Normal Law
- A/THR OFF
- Thrust Idle
- AP/FD OFF

Ok, the plane reaches AoA Alpha protection

- Vprot = 130kts
- Plane pitches down.

Question 2: What speed will the plane keep?
Choice 1: 130kts
Choice 2: A speed > 130kts.

Hope is better...

Now we are getting close!

"Do you mean that in climb mode, AP/FD has to manage and control the speed? I had thought that A/THR will send to the AP/FD the pitch the plane should have...Do you mean that in this case, FM will send the pitch the plane should have to manage the speed??? So basically FM is managing the speed?"
Exactly! Thrust is fixed at Climb power, AP/FD control pitch to keep the speed.

Example 1: This goes back to the question that I am not sure of.
As soon as the protection disengages, it will keep 175kt (controlled by the A/thr, in SPEED mode). Before the protection disengages, I am not sure.
Remember to disengage the protection you have to: Push the stick Greater than 8 ° forward, or,‐Greater than 0.5 °for at least 0.5 s when α < α MAX.

Example 2: Maintains 130kt with no sidestick input.

If an AP/FD pitch mode controls a vertical trajectory, the A/THR mode controls the target SPD/MACH.‐

Ok, so here, if A/THR is controling the target SPD mach, it means that A/THR is in SPEED MODE. So it means that AP/FD are maintaing a certain FPA.

Do you agree?

2) I am pretty sure that for example 1, ELAC will simply pitch down but won't maintain vprot because A/THR is still trying to manage 170kts. So the managed speed will be 170kts!

What do you think? ;)

Thanks a lot!

Yes. The vertical trajectory can be an FPA, or a Vertical Speed.

2. That makes sense and was what I originally believed, until reading about the requirement to disengage the protection. Now I am not 100% sure.

Hey! Thanks Dupre!

Your F-COM is telling you how to get out of ALPHA FLOOR not ALPHA PROT!!
I also had these questions:

1) F speed for take-off = minimum speed at which we can retract flaps from 3/2 to 1? So it is the minimum speed at which we can retract flaps?

2) S speed for take-off = minimum speed at which we can retract flaps from 1 to 0? So it the minimum speed at which we can retract slats?

3) F speed for landing = minimum speed at which we can fly without flaps? So we have to have our levers at 3 when we pass F speed?

4) S speed for landing = minimum speed at which we can fly without slats? So we have to have our levers at 1 when we pass S speed?

Thanks a lot!

1) and 2) Yes.

3) and 4) No. F and S speed are simply the target speeds when in Conf 2/3 and conf 1 respectively, with approach phase activated.

On approach the minimum speed to fly is Vls.

What do you mean by target speed?

We have to be at 1 at S speed and at 2/3 at F speed?

What is the lowest speed the plane can fly without flaps? VLS?

Whats does the amber = mean?

One of two things can happen.
1) Aircraft accelerates quickly, and maintains 1g, essentially maintaining its previous trajectory.
2) Aircraft maintains V.a.prot, but due to the increased thrust, and the fact that I have not disconnected the protection (by using forward stick), aircraft pitches up into a steep climb, still maintaining V.a.prot.

#2 is closer, but it is the AoA that is maintained not the airspeed.
V.a.prot, the steady-state airspeed corresponding to a.prot, is only calculated for display on the airspeed tape, it is not the control target.
In a non-steady-state condition the actual airspeed can be quite different.
SeeAir Accidents Investigation: Airbus A330 C-GGWD and Airbus A340 TC-JDN
for an example where turbulence caused an A340 to exceed a.prot during cruise. Alpha prot engaged and the aircraft zoom climbed over 2000 feet before the PF disengaged the mode, with airspeed well above v.a.prot the whole time.

@ m39462: Thanks but do you mean that at Vprot the plane maintains AoA Alpha protection??? Well, if the plane pitches down, it is no more maintaining AoA Alpha protection.

By the way for question 3, I am talking about this:
Primary Flight Display Symbols | Next Flap Extend Speed

Thanks

"What do you mean by target speed?"
I mean the speed autothrust will maintain if it is engaged.

"We have to be at 1 at S speed and at 2/3 at F speed? "
No there is no such requirement.

"What is the lowest speed the plane can fly without flaps? VLS?"
In any configuration the lowest speed you should go is Vls. In Conf0,1,2,3,Full, you can go down to Vls. The plane can go slower of course, but this is not ideal (Except in case of Gpws warning or windshear, when you can go below)

"Whats does the amber = mean?"
Those are the VFEnext marks, indicating the speed you must be below in order to increase flap config by 1 stage.

Wow thanks for that document m39462! Very interesting to read.

Seems crazy that in turbulence, as soon as you reach A.prot, even if it just clicks over for a second, the plane will maintain it and zoom climb thousands of feet without any sidestick input!

And with AP engaged, the same happens at A.prot +1° as it then disengages AP and enters AoA protection.

I wonder how many airbus pilots are aware of this? I was not, and I suspect I am not alone.

This could even have some relationship with Air Asias recent crash... turbulence followed by zoom climb...

I am not able to get you.

1) What is F speed and S speed for landing? You said they were target speeds. Please explain. You mean to say Athr will manage F speed and S speed? What is the relation between Athr and flaps/slats speed????

2) You don't have VFE for take-off?

Thanks

Ok so whether you are accelerating or decelerating, you need to know at what speed you can extend or retract one more stage.

If you are accelerating, those speeds are F speed (to conf1) and S speed (to conf0).

If you are decelerating, those speeds are the amber = marks which move down every time you select a new conf.

So to answer your questions...
1. Yes, Athr will maintain F/S/O speed for you, so long as it is engaged, and the approach mode is activated on the fmgs.
O speed (green dot) in Conf0
S speed in conf1
F speed in conf2/3
Approach speed in conf full (Or conf3 if that is landing configuration)

2. Yes of course you have Vfe. It is Vmax, the top red band on the speed tape. Vmax=lowest of Mmo, Vmo, Vle, Vfe.

So you have three speeds relating to the flaps configuration...
1) Vmax, which is your maximum speed for the configuration (=Vfe on approach)
2) amber "=" which is what the Vfe will be if you select one more stage of flaps
3) F/S speed which is the min speed before you can safely retract one stage. (Think of it as roughly where the new Vls is going to be after selecting one stage up)

So while landing, you have to be below the amber = and F speed to retract your flaps?
So when you go to 2, F speed will go down and the amber =. When you will be below the amber =, you can retract your flaps to 1?

Thanks

Ok.

1) VFE is the maximum speed at which we can fly without braking our flaps/slats. Right?

2) Is F speed for landing a target speed where we have to have our flaps at conf 2/3 or is it the minimum speed at which we can fly without flaps 2/3?

3) Same question for slats.


So when we extend our slats to 1, we can see the amber =
That is the maximum speed we can fly with our slats. Then there is S speed which is.........

Thanks

"So while landing, you have to be below the amber = and F speed to retract your flaps?"
While on approach you will be extending your flaps. You only have to be below amber =

"So when you go to 2, F speed will go down and the amber =. When you will be below the amber =, you can retract your flaps to 1?"
When you go to 2, F speed is displayed. It doesnt change, but S speed disappears and F speed appears on the speed tape.

Trying to put it anotherway...
To RETRACT flaps you have to be ABOVE F/S speed.
To EXTEND flaps you have to be BELOW amber =.


1. Yes.

2. Neither. It is a comfortable speed to fly with flaps 2/3. And the minimum speed if you want to retract to flaps1.

3. Neither. It is a comfortable speed to fly with flaps 1. And the minimum speed if you want to retract to flaps0.

"So when we extend our slats to 1, we can see the amber =
That is the maximum speed we can fly with our slats. Then there is S speed which is......."
No. with flaps 1, your Vmax is Vfe. The amber = will show the Vfe for flaps2.

Reading this thread is giving me a persistent visual of a paraplegic monkey trying to copulate with a pigskin. Possibly even two paraplegic monkeys trying to copulate with the same pigskin. Pretty comical, actually.

Ok Amadis....hmmm.....

@Dupre: Thanks a lot Dupre!

Ok...so when we see the first amber = it means that we have to extend slats to 1.
Then, the amber = will go down and S speed will come. So it means that it is a comfortable speed to fly. Now, we reach the amber = , we then extend our flaps to 3. We pass F speed which appears. It is a comfortable speed to fly.

1) Am I right?

2) When do we have flaps full?

3) Do we have to be at conf 2 or 3 when we pass our second amber =?

Thanks

Passing an amber = does not mean you have to extend any flaps at all. It just means you can extend flaps if you want to.

Normally approach sequence goes....

1. Activate approach phase. Autothrust decelerates to green dot.
(green dot around 210kt, amber= 230kt on A320)

2. When below amber = select flaps 1. Autothrust decelerates to S speed.
(S speed around 180kt, amber= 200kt on A320).

3. When you are ready for Flaps 2 (typically just before glideslope intercept) select flaps 2. Autothrust decelerates to F speed.
(F speed around 140kt, amber= 185kt on A320)

4. Gear down (exactly when depends on your judgement of a few factors - winds, altitude, speed etc)

5. When you are nearing the point at which you need to be stabilised, select flaps 3. Autothrust keeps maintaining F speed, Amber= moves to 177kt on A320.

6. Very shortly after, select flaps full (if that is landing configuration), Autothrust maintains Vapp (or GSmini if active) and the amber = will disappear as there is no "next flap setting" from flaps full. (you won't see this on the pfd though, as it will be off the upper end of the speed tape)

7. Call for landing checklist.


Amadis - glad you are enjoying the show :D

Good morning,

Quite confusing!

1) A/THR will manage F/S/O speeds as speed constraints where we don't have to level-off isn't it? So is there a F/S/O point in our F-PLN? If, not how does it know when to manage these speeds? Does it manage F/S/O in selective mode? Because there can be waypoints between F/O/S with speed restrictions too.

Ok, so you activate approach speed, then only it will display the amber =.
The plane will go down to green dot, around 210kts. But the amber = will come at 230kts.
So you can retract flaps below 230kts. When you are at 1, you will see that S speed is around 180kts but the amber = is at 200kts. The plane will go towards S speed. 180kts is a comfortable to fly with flaps 1 but we can go to 2 below 200kts, so once passed the amber =. When you are at flaps 2, you will see F speed around 140kts. Then, you will see that the amber = is at 185kts. When below 185kts, flaps 3. F speed is a comfortable speed to fly with flaps. Finally, you will see the amber = at 177kt, you can then have flaps full. But you can simply fly with flaps 3 at Fspeed (140kts).

2) Is everything right?

3) Is F speed a comfortable speed for flaps 2 or flaps 3??

4) Do you only see the next amber = when you extend of 1?

Thanks

The amber= at 230kt is displayed all the time when
1. flaps 0
2. below 20,000 ft (Max flap operating altitude)

The F/S/O speeds are not managed as constraints, and are not in the flight plan. It really is very simple...
Activate the approach phase on the fmgc (Perf page), and the managed speed becomes green dot. Then extend flaps 1, and managed speed is S speed. Flaps 2/3 and managed speed is F speed. You can do this at any stage of the flight and it will work the same. Obviously in normal operations you will only do it on approach.

I think you need to check your definition of retract. Retract means to pull in. Extend means to push out. So you extend flaps from 0 to 1. You retract flaps from 1 to 0.


3. F speed is comfortable for both flaps 2 and 3. there is very little difference between these settings...

4. You will always see the amber =. It is always Vfe of the next greater flap setting. The only times you dont see any amber= is
1) above 20,000
2) when flaps are full.

Thanks

1) So the amber = will keep coming, one after one, even if you don't EXTEND your flaps?

2) Yes, I wanted to say Extract. So is everything else right?

3) Ok here are my wpt:

- AGOPA : 5000ft - 250kts.
- BANOX: 4500ft - 245kts
---> Green dot speed 230kts.
- LORNI: 3000ft 205kts.

Now, you are in ALT managed. What will you read on the FMA after Banox? Will it arm ALT in Blue? Same question with an OP DES and V/S -1500ft/min.

Thanks

Job.
 

Dupre, a complex and interesting topic and I am gaining much insight on "the bus" from your and others attempts to answer these questions from France...I am sure your efforts will be rewarded fully some time down route but you truly Sir, have the patience of Job.
:ok:

Flight sim for PC or MAC, On line access, freedom of information and a limited knowledge on a subject, to which one might feel at 14 they need answers, is a dangerous combination. Only a rich parent or lottery win away from P2F...?

And as for the monkeys and pigskin analogy...been thinking the same but unable to put it quite so eloquently....

1. No, the amber = only changes if you change your flaps.
Conf0, amber= is at 230kt.
Conf1, amber= is at 200kt.
Conf2, amber= is at 185kt.
Conf3, amber= is at 177kt.
ConfF, amber= disappears.

These are true whether you are extending flaps, retracting flaps, or flying without touching flaps.

2. Yes.

3. Need a bit more information. What altitude have you set on FCU? Are you in ALT mode or DES mode? And what altitude are you at?

Thank you, Alex-Flo, for your kind words, and I agree that Dupre does, in fact, have the patience of Job. On a related note, I have some doubts our young friend is either 14 or from France, but, I suppose, that's neither here nor there.

Fingers crossed
 

Then let's also hope he doesn't already occupy a right hand (or for that matter left) hand seat:E

The whole thing is challenging me to think about some things in more depth than I would otherwise, and am learning some good stuff.

Anyway if the internet had been around when I was 14, I would probably have been asking thousands of questions myself. Probably a lot less informed than AF330s too.

It's just that I can't help, but think that someone from France would have a much easier time getting his questions answered on a French forum, especially when those questions concern a French-made aircraft. I don't see a single good reason why he'd come on an English-speaking forum (and then not the correct section) and persist in torturing himself and others.

I doubt this is a potential P2F case either, those guys have very little curiosity in the in-depth workings of their aircraft, especially THIS in-depth.

True....
 

Very benevolent and generous in time and patience of Dupre though. I have wondered why if it's a real AB operator why the constant misunderstanding of configuring tied into the Alpha Floor/Alpha Max issues, the understanding of climb thrust being constant and the pitch inputs of AP to maintain climb speed seem to have illuded our OP some how. Power Attitude Trim....manual or even in automation you can't try and maintain speed or attitude by continually changing both pitch and power....it would be mutually incompatible to have computers fighting each other to maintain control of the same criteria?

I also wonder about the desire to drag it round to what looks like some kind of made up flight plan MCDU home built route where speed and Alt constraints are being built in to perhaps let the Home Flight Sim follow a profile before a STAR begins??

Despite all this however it has still been and is being very informative to me on the logic behind this FBW topic......:8