Airbus crash/training flight
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DC-ATE
The two sidestick inputs are normally summed by the computer, unless one side takes control by pressing the red button.
I just have a problem with youngsters who do think their old junk is great because they don't know any better.
Anyway, all modern planes are FBW, and there's no going back.
I just have a problem with youngsters who do think their old junk is great because they don't know any better.
Anyway, all modern planes are FBW, and there's no going back.
Last edited by Dysag; 6th Feb 2009 at 21:07.
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Anyway, all modern planes are FBW, and there's no going back.
Before you know it they will all be FWP as well. That's "Flight without Pilot" for those who are wondering. FBW is just another step towards this, and yes there is no going back.
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Originally Posted by night_flight99
I think your logic is self defeating. In an airbus the standard procedure for taking control, and ensuring that you have control, is to press the red button and keep it pressed (whilst stating "I have control"). You then have absolute control and you decide which way you are going to turn
Regarding the seriousness of the thread, it would be easier if guys pretending demonstrating something based on a specific report could restrain from publishing numbers nowhere to be seen in that very report …
Thanks for your attention Lemurian.
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Back on thread?
Okay I haven't seen anything new coming out of official sources recently. Has anybody else seen anything new?
The debate on ABS performance, ABS design theorum, ABS ops, ABS software heirarchy, ABS v BOE, etc., is great but what's going on with the accident investigation?
The debate on ABS performance, ABS design theorum, ABS ops, ABS software heirarchy, ABS v BOE, etc., is great but what's going on with the accident investigation?
DC-ATE;
This is likely in the thread earlier on but I'm just lighting up the computer after a few days away.
As Dysag says, the 320 sidestick inputs are summed but the important point is, they are summed algebraically.
Double sidestick input is a serious no-no in 320-type aircraft. It continues to occur however, at least as shown in flight data analysis. Usually it's a training-line indoc situation. That said, CONF iture, you are absolutely right in what really happens.
What some transitioning to fbw (Airbus style) initially may not appreciate because it may not be emphasizd in training is, the stick does not control ailerons/elevators; - it "requests" a roll-rate or a g-force. You may still recall a CWS mode - Control Wheel Steering - where, when engaged the airplane "stayed" in the last attitude set by the controls before engaging. That is essentially what fbw/sidestick control is. "No input, no change".
The autoflight-autothrust-flight director-flight management guidance computer systems are deeply intertwined with one another, all talking to each other. The non-moving thrust levers is a non-issue in such a system as the various flight modes look after thrust when the levers are set in their normal flying position, called the "CLB" or climb position. In this mode depending upon climb, cruise or descent, the engines will respond to airspeed, rate of climb or cruise speed commands from the FMGC, (Flight Management Guidance Computer).
For example, in a climb, with autothrust engaged but the a/c being manually flown, power is "on the elevator". That means power is adjusted by FADEC to match the thrust required to maintain an airspeed which is set by the cost index. Usually that's the old max continuous, about 92% N1. If one pulls back, the airspeed will bleed off only because 92% isn't sufficient thrust to keep both the climb and the speed, but power is still governed "by the elevator" in manual flight. To understand this better, take the opposite case where the rate of climb is reduced by gently pushing forward on the stick - the rate of climb will decrease, but without touching the thrust levers, the power will come back to match the speed being commanded by the FMGC.
In descent, the usual auto-flight modes are either "IDLE, OPEN DESCENT" or VNAV. VNAV is a calculated path that is managed by both the autothrust and autopilot - the speed is permitted to vary to take advantage of energy before bringing up the power from Idle.
"OPEN DESCENT" means the engine thrust is commanded to idle, (about 35% N1). The autothrust will not bring the power up until the selected altitude is captured. In this case, it is airspeed, not power, that is "on the elevators". To better understand this, if the sidestick is pulled back slightly, the airspeed will reduce and continue to do so until a minimum speed calculated by the flight augmentation computers using weight, angle-of-attack and CAS is reached, at which point the autothrust will revert from "IDLE" to "SPEED" and the "OPEN DESCENT" mode to "V/S", (to prevent a huge power increase to "chase" the originally targeted speed).
For this reason, in manual flight the flight directors must either be followed or turned off as they are indicating the "thinking" behind the autothrust system. If turned off, the autothrust reverts to the "SPEED" mode to again protect the airplane.
The other vertical modes are either variations on this theme or protections which guard against speed gain/loss or v/s excursions higher than certain values.
The sidestick is a very powerful little handle and is best flown gently, usually with the hand near the base to avoid large inputs.
As an aside, while the US Airways flight will have had "Alpha-prot", (stall protection), the fbw system would not have protected this airplane from stalling in this case because the engines were incapable of delivering TOGA (Takeoff/Go Around) power. In "Alpha-prot", the airplane is not pitched down to reduce the AoA - the only airplane response is to increase power, so Captain Sullenberger had to fly the speed indicated on the PFD, (Primary Flight Display) just above the alpha-max stall speed and by the initial indications, this is just what he did. See the graphic below - likely he would have flown between Vls and Alpha Prot but we'll know more after the reports.
This is likely in the thread earlier on but I'm just lighting up the computer after a few days away.
As Dysag says, the 320 sidestick inputs are summed but the important point is, they are summed algebraically.
Double sidestick input is a serious no-no in 320-type aircraft. It continues to occur however, at least as shown in flight data analysis. Usually it's a training-line indoc situation. That said, CONF iture, you are absolutely right in what really happens.
What some transitioning to fbw (Airbus style) initially may not appreciate because it may not be emphasizd in training is, the stick does not control ailerons/elevators; - it "requests" a roll-rate or a g-force. You may still recall a CWS mode - Control Wheel Steering - where, when engaged the airplane "stayed" in the last attitude set by the controls before engaging. That is essentially what fbw/sidestick control is. "No input, no change".
The autoflight-autothrust-flight director-flight management guidance computer systems are deeply intertwined with one another, all talking to each other. The non-moving thrust levers is a non-issue in such a system as the various flight modes look after thrust when the levers are set in their normal flying position, called the "CLB" or climb position. In this mode depending upon climb, cruise or descent, the engines will respond to airspeed, rate of climb or cruise speed commands from the FMGC, (Flight Management Guidance Computer).
For example, in a climb, with autothrust engaged but the a/c being manually flown, power is "on the elevator". That means power is adjusted by FADEC to match the thrust required to maintain an airspeed which is set by the cost index. Usually that's the old max continuous, about 92% N1. If one pulls back, the airspeed will bleed off only because 92% isn't sufficient thrust to keep both the climb and the speed, but power is still governed "by the elevator" in manual flight. To understand this better, take the opposite case where the rate of climb is reduced by gently pushing forward on the stick - the rate of climb will decrease, but without touching the thrust levers, the power will come back to match the speed being commanded by the FMGC.
In descent, the usual auto-flight modes are either "IDLE, OPEN DESCENT" or VNAV. VNAV is a calculated path that is managed by both the autothrust and autopilot - the speed is permitted to vary to take advantage of energy before bringing up the power from Idle.
"OPEN DESCENT" means the engine thrust is commanded to idle, (about 35% N1). The autothrust will not bring the power up until the selected altitude is captured. In this case, it is airspeed, not power, that is "on the elevators". To better understand this, if the sidestick is pulled back slightly, the airspeed will reduce and continue to do so until a minimum speed calculated by the flight augmentation computers using weight, angle-of-attack and CAS is reached, at which point the autothrust will revert from "IDLE" to "SPEED" and the "OPEN DESCENT" mode to "V/S", (to prevent a huge power increase to "chase" the originally targeted speed).
For this reason, in manual flight the flight directors must either be followed or turned off as they are indicating the "thinking" behind the autothrust system. If turned off, the autothrust reverts to the "SPEED" mode to again protect the airplane.
The other vertical modes are either variations on this theme or protections which guard against speed gain/loss or v/s excursions higher than certain values.
The sidestick is a very powerful little handle and is best flown gently, usually with the hand near the base to avoid large inputs.
As an aside, while the US Airways flight will have had "Alpha-prot", (stall protection), the fbw system would not have protected this airplane from stalling in this case because the engines were incapable of delivering TOGA (Takeoff/Go Around) power. In "Alpha-prot", the airplane is not pitched down to reduce the AoA - the only airplane response is to increase power, so Captain Sullenberger had to fly the speed indicated on the PFD, (Primary Flight Display) just above the alpha-max stall speed and by the initial indications, this is just what he did. See the graphic below - likely he would have flown between Vls and Alpha Prot but we'll know more after the reports.
Last edited by PJ2; 6th Feb 2009 at 23:23.
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Thank you Sky Wave, Dysag and PJ2 for the info on the side sticks. It still scares me!
Dysag - "I just have a problem with youngsters who do think their old junk is great because they don't know any better."
Well, I'm working on becoming an octogenarian. Not sure that qualifies me as a "youngster" or not. I feel like one anyway! Probably act like one at times as well. I just have a problem with some of this newer equipment that is slowly taking the pilot out of the loop. But, PLEASE don't call "my" DC-8 "old junk". Not while I'm still around anyway. Those and the Connies (along with a couple of others) took good care of me for thirty years.
Dysag - "I just have a problem with youngsters who do think their old junk is great because they don't know any better."
Well, I'm working on becoming an octogenarian. Not sure that qualifies me as a "youngster" or not. I feel like one anyway! Probably act like one at times as well. I just have a problem with some of this newer equipment that is slowly taking the pilot out of the loop. But, PLEASE don't call "my" DC-8 "old junk". Not while I'm still around anyway. Those and the Connies (along with a couple of others) took good care of me for thirty years.
It still scares me!
The '8 was my "first love" in the late 50's/early 60's and I had the good fortune and pleasure of a few thousand hours in it before transitioning to the 727, then the 1011, then the 76'.
Congratulations on the octagenarian goal - I would not have guessed that from your writing - like Dysag, I hope to make it as well.
Cheers, sir.
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PJ2 -
"Congratulations on the octagenarian goal - I would not have guessed that from your writing..."
Well, thank you. I'm not there yet; got a few to go, but hopefully, I'll make it. Even though airplanes might've given me the grey hairs I still have, it might have also given me some extra time.
Hope you all enjoy the "new age" of aviation. Good luck!
"Congratulations on the octagenarian goal - I would not have guessed that from your writing..."
Well, thank you. I'm not there yet; got a few to go, but hopefully, I'll make it. Even though airplanes might've given me the grey hairs I still have, it might have also given me some extra time.
Hope you all enjoy the "new age" of aviation. Good luck!
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Clandestino
And Aquadealte, we we been here before just a couple days ago. Please do read your FCOM and understand it. I have expressed myself imprecisely first time, my apologies, but I do maintain that speed stabilities in altn law with reduced protections are not worthy of being called protections as they can be overriden. Your proposed red button would leave pilot able to overbank aeroplane, attain severe pitch-up or pitch down, stall it or overspeed it. In my book this isn't "maintaining a great deal of protections" at all.
I was "proposing" a "solution" that would put the pilot always in control. On the T7, pilots are always in control of the aircraft, because the system allows them to override protections...
One has to choose: either one has "your" type of protections and face the risk of being a "hostage" of an aircraft that flies the way it was designed/programmed to fly or, one has the chance to really have control of it flying a bird that allows those protections to be overridden.
I know what I would choose, if I had the chance to...
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PJ2
Sorry, but there is a rat here :
On the 320, "Alpha prot" is just an AoA protection : between "prot" and "max", the side stick commands alpha directly. However, the angle of attack will not exceed alpha max even if the pilot pulls the stick all the way back. If the pilot releases the stick, the airplane will return to alpha prot and stay there. That,regardless of the thrust you have available.
On the other hand, Alpha floor is the protection which is triggered with a high AoA and the airplane would go into a TOGA mode.
With the obvious lack of thrust, the system stays in AoA protection mode.
That's in all probability what happened to US 1549 as one of the NTSB press conferences mentioned that at their point of ditching, they were two knots below "prot" speed and just five knots above "alpha max" speed for their configuration.
As an aside, while the US Airways flight will have had "Alpha-prot", (stall protection), the fbw system would not have protected this airplane from stalling in this case because the engines were incapable of delivering TOGA (Takeoff/Go Around) power. In "Alpha-prot", the airplane is not pitched down to reduce the AoA - the only airplane response is to increase power, so Captain Sullenberger had to fly the speed indicated on the PFD, (Primary Flight Display) just above the alpha-max stall speed and by the initial indications
On the 320, "Alpha prot" is just an AoA protection : between "prot" and "max", the side stick commands alpha directly. However, the angle of attack will not exceed alpha max even if the pilot pulls the stick all the way back. If the pilot releases the stick, the airplane will return to alpha prot and stay there. That,regardless of the thrust you have available.
On the other hand, Alpha floor is the protection which is triggered with a high AoA and the airplane would go into a TOGA mode.
With the obvious lack of thrust, the system stays in AoA protection mode.
That's in all probability what happened to US 1549 as one of the NTSB press conferences mentioned that at their point of ditching, they were two knots below "prot" speed and just five knots above "alpha max" speed for their configuration.
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PJ2 - sorry, but I do not recognise some of the A320 I fly from your post 
In V/S maybe, but normal (OP) CLB modes it is juts like a Boeing or C152 - Climb Power and Pitch controls IAS...
Ditto - V/S only (and just as a Boeing).
Again, and as corrected above by Lemurian, not correct... IMHO 
Alpha Max / Alpha Prot are not speeds - they are Alpha values. VLS is a "speed"... and hence why in a turn or level off, the 2 Alpha values will increase, and potentially mask VLS.
I flew B757/767 prior A320 (and after A340)... The AP modes, once you "translate them" are fairly similar... the FBW protections only come into play when you exceed what you would fly in normal flight. Alpha Floor / Max only come into play with serious abuse, and after a Stick Shaker would have gone off on a Boeing. And in the 1549 case, I doubt any FBW "protections" were invoked, though as above, the Alpha Prot area seems to have been entered... if it was entered gently, Alpha Floor (TOGA) is only asked for "somewhere" in the Alhpa Prot area, and there are a couple of other reasons why it might not have been triggered here (<100R / Engine Out + Slats/Flaps). And even if it was triggered, seems it was not going to get anything
NoD
For example, in a climb, with autothrust engaged but the a/c being manually flown, power is "on the elevator".
In V/S maybe, but normal (OP) CLB modes it is juts like a Boeing or C152 - Climb Power and Pitch controls IAS...
....take the opposite case where the rate of climb is reduced by gently pushing forward on the stick - the rate of climb will decrease, but without touching the thrust levers, the power will come back to match the speed being commanded by the FMGC.
As an aside, while the US Airways flight will have had "Alpha-prot", (stall protection), the fbw system would not have protected this airplane from stalling in this case
so Captain Sullenberger had to fly the speed indicated on the PFD, (Primary Flight Display) just above the alpha-max stall speed
I flew B757/767 prior A320 (and after A340)... The AP modes, once you "translate them" are fairly similar... the FBW protections only come into play when you exceed what you would fly in normal flight. Alpha Floor / Max only come into play with serious abuse, and after a Stick Shaker would have gone off on a Boeing. And in the 1549 case, I doubt any FBW "protections" were invoked, though as above, the Alpha Prot area seems to have been entered... if it was entered gently, Alpha Floor (TOGA) is only asked for "somewhere" in the Alhpa Prot area, and there are a couple of other reasons why it might not have been triggered here (<100R / Engine Out + Slats/Flaps). And even if it was triggered, seems it was not going to get anything
NoD
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Quote Night Flight99: I think your logic is self defeating. In an airbus the standard procedure for taking control, and ensuring that you have control, is to press the red button and keep it pressed (whilst stating "I have control").
Thank you for your answer. I did not go to the end of my reasoning (such as it is) wishing to be short…my mistake. I did not criticize the A320 which I have flown a few years, nor the FBW system, but the side stick in that case…as opposed to a yoke as in the 777 for example. You are right in your description of the priority system but I hope you do not imagine that with a glider filling the windscreen, somebody will say I have control (the captain did not) and push the priority button etc…it is all reflex action. In that case the captain acted on the sidestick laterally and the pilot in the pitch axis (down). I just tried to say that the copilot seing the hands of the captain jumping on the controls will stop doing anything (that’s the best decision in such cases).
As for the original subject of the thread, I shall wait with you for more information, feeling very sad for the crew, and having a thought too for the mechanics who work very well in Perpignan, as elsewhere. I flew many test flights there after heavy overhauls, plus painting jobs, and I can tell you that static ports, pitot tubes, angle of attack vanes were checked on the ground by the mechanics then by the crew before the flight.
Thank you for your answer. I did not go to the end of my reasoning (such as it is) wishing to be short…my mistake. I did not criticize the A320 which I have flown a few years, nor the FBW system, but the side stick in that case…as opposed to a yoke as in the 777 for example. You are right in your description of the priority system but I hope you do not imagine that with a glider filling the windscreen, somebody will say I have control (the captain did not) and push the priority button etc…it is all reflex action. In that case the captain acted on the sidestick laterally and the pilot in the pitch axis (down). I just tried to say that the copilot seing the hands of the captain jumping on the controls will stop doing anything (that’s the best decision in such cases).
As for the original subject of the thread, I shall wait with you for more information, feeling very sad for the crew, and having a thought too for the mechanics who work very well in Perpignan, as elsewhere. I flew many test flights there after heavy overhauls, plus painting jobs, and I can tell you that static ports, pitot tubes, angle of attack vanes were checked on the ground by the mechanics then by the crew before the flight.
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"I can tell you that static ports, pitot tubes, angle of attack vanes were checked on the ground by the mechanics then by the crew before the flight."
Makes one wonder, then, if the letter from Airbus isn't a diversion..
GB
Makes one wonder, then, if the letter from Airbus isn't a diversion..
GB
Originally Posted by DC-ATE
It appears to me that you A-320 drivers can't agree on just what goes on with your FBW systems during various phases of flight.
Not everyone discussing here is an Airbus driver, nor is discussion limited to bus drivers only.
Not everyone claiming to be Airbus driver actually is one.
Rules of the game are quite simple: anyone can have his say but the FCOM trumps all.