ALPHA PROT/FLOOR/MAX
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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 °."
"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 °."
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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
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
Last edited by AF330; 31st Dec 2014 at 09:38.
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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?
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?
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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!!
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
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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
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
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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.
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.
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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...
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...
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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)
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)
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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.
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.
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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.
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.
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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...
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...
Last edited by AF330; 1st Jan 2015 at 17:10.
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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.
"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.
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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!
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!
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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.
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.
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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!
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!
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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.
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.
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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?
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?
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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.
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.
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@ 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
By the way for question 3, I am talking about this:
Primary Flight Display Symbols | Next Flap Extend Speed
Thanks