Airbus crash/training flight
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What worries me, however, is whether such a manual override would lead to more or less problems
Fact is that on the other fly-by-wire product, there has not been one incident where a manual override of a computer has led to a worse situation. (Not that i would know of an incident where computers gave erroneous signals, though.)
Fact is as well, that in at least one Airbus (QF72) such erroneous signals led to an erroneous input that was at first not recuperable by the pilot. (A override capability would have been very welcome I suppose.)
Reread the two facts and then the entry argument and very basic common sense will give you an answer, at least to me ......
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llondel...? stickyb...? Clandestino:
FCOM A320 - 1.27.30 Page 2
SmartCockpit - Airline training guides, Aviation, Operations, Safety
Please go to that page and take a look at the schematics. You'll find out the conditions for RECONFIGURATION CONTROL LAWS on A320. Maybe then, you may understand that, despite of being highly improbable, one could fly in a situation where the aircraft doesn't downgrade to alternate law, trapping the pilot among protections "active" leading to lost control. If, by chance, for instance, you get wrong (yet within parameters) hight speed information through all ADR's, the system will be kept in Normal Law, and High Speed Protection will keep active sending a nose up input and pilots will be unable to bring nose down. (That would be a case for a "Red Button" or a new logic to the instinctive disconnection push button, in order to bring the Law's to a degradation mode, where the pilot still have control of the aircraft).
Please tell me, if I'm wrong.
(I'd rather be wrong...)
P.S.- What is the probability of 4 engines failure? Yet it has happened ...
SmartCockpit - Airline training guides, Aviation, Operations, Safety
Please go to that page and take a look at the schematics. You'll find out the conditions for RECONFIGURATION CONTROL LAWS on A320. Maybe then, you may understand that, despite of being highly improbable, one could fly in a situation where the aircraft doesn't downgrade to alternate law, trapping the pilot among protections "active" leading to lost control. If, by chance, for instance, you get wrong (yet within parameters) hight speed information through all ADR's, the system will be kept in Normal Law, and High Speed Protection will keep active sending a nose up input and pilots will be unable to bring nose down. (That would be a case for a "Red Button" or a new logic to the instinctive disconnection push button, in order to bring the Law's to a degradation mode, where the pilot still have control of the aircraft).
Please tell me, if I'm wrong.
(I'd rather be wrong...)P.S.- What is the probability of 4 engines failure? Yet it has happened ...
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possibility of all four engine failure
British airways B747 once lost all four engines due to volcanic ashes. but i believe they got them back also and made a emergency landing. This flight was from manila.
thanks
thanks
Fact is as well, that in at least one Airbus (QF72)
However this report is final, I recomend it for those interested in FBW architecture and voting issues. I apologise for being unable to provide Airbus example.
despite of being highly improbable, one could fly in a situation
What is the probability of 4 engines failure? Yet it has happened ...
Clandestino
as of today, former Airbus driver.
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stickyb: clearly, there are no pushrods and for FBW you will always have an electronic middle-man to some extent. However i thought the idea of direct law was to have a simple backup bit of software that was highly unlikely ever to cause control problems due to software/sensor malfunction. I'm just surprised that the pilot apparently cant easily select it.
i understand why its designed to degrade automatically to direct law in some non normal situations when you drop the gear etc - to ensure the thing will definitely flare when you pull the stick back etc.. but what about the oh **** scenario where the plane suddenly bunts towards the ocean for no apparent reason? Don’t you need a way to tell it to stop obeying the busted AOA probe and deflect the elevator back to where you want it?
(this discussion is not intended to speculate on the accident cause)
i understand why its designed to degrade automatically to direct law in some non normal situations when you drop the gear etc - to ensure the thing will definitely flare when you pull the stick back etc.. but what about the oh **** scenario where the plane suddenly bunts towards the ocean for no apparent reason? Don’t you need a way to tell it to stop obeying the busted AOA probe and deflect the elevator back to where you want it?
(this discussion is not intended to speculate on the accident cause)
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As long the final report is not out, it is not a fact!!!!!!
On a lighter note Clandestino, enjoy your retirement, or did you really change to the dark side?
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aguadalte:
I don't trust computers to handle anything more serious than trivial fault conditions and I design them and things using them. Ultimately they have a set of instructions on what to do, which is presumably arrived at by a bunch of experts writing down a load of scenarios, what inputs indicate problems and what the automatics should do about it. They only need to miss one, or consider it so unlikely that they don't need to accommodate it. Even nuclear power station design has the concept of a probability threshold for accidents to limit the cost of safety.
As for all the instruments giving the wrong answers, I'd say that a lot of pilots would find it difficult to fly as well, although given the Mk.1 eyeball, they'd stand more chance than a machine, at least in daylight. (Aeroperu with the ports taped over and in the dark?)
I don't trust computers to handle anything more serious than trivial fault conditions and I design them and things using them. Ultimately they have a set of instructions on what to do, which is presumably arrived at by a bunch of experts writing down a load of scenarios, what inputs indicate problems and what the automatics should do about it. They only need to miss one, or consider it so unlikely that they don't need to accommodate it. Even nuclear power station design has the concept of a probability threshold for accidents to limit the cost of safety.
As for all the instruments giving the wrong answers, I'd say that a lot of pilots would find it difficult to fly as well, although given the Mk.1 eyeball, they'd stand more chance than a machine, at least in daylight. (Aeroperu with the ports taped over and in the dark?)
Thanks GMDS, I'm not retiring, just switching seats and type.
After reading ATSB preliminary report (especially the diagrams at the back) I'm more concerned about output than input. It seems that one AoA signal was spiking wildly, second was stable and third, sadly, is not mentioned in prelim. I'll wait for final report before worrying more, though.
Originally Posted by GMDS
what other than an erroneous computer input could it be?
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If (BIG IF) the accident report were to come out showing a fault in the
FBW/computer system on board, does anyone really think that FBW will be
eliminated from this model or any other model aircraft? Of course not. But, then again, I doubt very much the report would indicate that whether it was true or not.
Aside from the cost savings involved and the fact that engineers now-a-days grew up with arcade games and computer games, what is the big deal with FBW anyway? As someone pointed out, the DC8/9 were the last 'real' airplanes that were cable-operated. FBW originated with the need to control very unstable military fighters. What's the need, other than cost, to carry it over to commercial aircraft? The old saying, "If it ain't broke, don't fix it" would apply here I would think.
If you couldn't tell, I'm not in favor of computers telling the pilot what to
do and what not to do. And, I like the idea of the control wheel and
throttles, etc. connected to something by cables, not an electric current.
FBW/computer system on board, does anyone really think that FBW will be
eliminated from this model or any other model aircraft? Of course not. But, then again, I doubt very much the report would indicate that whether it was true or not.
Aside from the cost savings involved and the fact that engineers now-a-days grew up with arcade games and computer games, what is the big deal with FBW anyway? As someone pointed out, the DC8/9 were the last 'real' airplanes that were cable-operated. FBW originated with the need to control very unstable military fighters. What's the need, other than cost, to carry it over to commercial aircraft? The old saying, "If it ain't broke, don't fix it" would apply here I would think.
If you couldn't tell, I'm not in favor of computers telling the pilot what to
do and what not to do. And, I like the idea of the control wheel and
throttles, etc. connected to something by cables, not an electric current.
If (BIG IF) the accident report were to come out showing a fault in the FBW/computer system on board, does anyone really think that FBW will be eliminated from this model or any other model aircraft?
FBW if it weren't for Iberia crew putting the A320 through its paces.
I'm not in favor of computers telling the pilot what to do and what not to do.
[Steve]
You express yourself quite clearly 
and of course one could add a BRB but the trades would be complex and difficult to certify. But then again our amature discussion of this in this thread gives us something to entertain
I've been trying to write this last paragraph for some time. Please excuse me if I express myself poorly. Even if it were shown that pilots were statistically a far worse bet than potentially failing computers, I would hate to be the pilot who may meet his fate *knowing correctly* that all he needed to do was override a computer :-(
and of course one could add a BRB but the trades would be complex and difficult to certify. But then again our amature discussion of this in this thread gives us something to entertain
Improbable Situation
How do you find yourself in a highly improbable situation is beyond me.
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Clandestino -
"Good, because on Airbus it's the pilot telling the computers what to do. Computers only refuse if one tries to: pitch above 30 deg ANU or below 15 AND, bank over 67 degrees, overspeed, stall or over-G the aeroplane. One just has to fly nicely and smoothly to avoid computer intervention."
---
Well, there just might be a time when those computer limitations NEED to be exceeded. If the airplane can't handle it, then there might just be something wrong with the design.
"Good, because on Airbus it's the pilot telling the computers what to do. Computers only refuse if one tries to: pitch above 30 deg ANU or below 15 AND, bank over 67 degrees, overspeed, stall or over-G the aeroplane. One just has to fly nicely and smoothly to avoid computer intervention."
---
Well, there just might be a time when those computer limitations NEED to be exceeded. If the airplane can't handle it, then there might just be something wrong with the design.
US Airways 1549? Yukla 27 set the precedent, flying through flock of ducks (or were they geese?) and knocking out both engines is not quite an improbable situation.
Into what?!? Stall? Overspeed? Spiral dive? It would be overstatement if I were to say that it's the matter of good airmanship to avoid situations where only limitation busting can save the day - it's the matter of simple self-preservation.
Well, there just might be a time when those computer limitations NEED to be exceeded.
US Airways 1549? Yukla 27 set the precedent, flying through flock of ducks (or were they geese?) and knocking out both engines is not quite an improbable situation
However, in any product caused accident the exact combinations of all causal factors should be thought to be improbable beforehand.
In this accident there may be a surprise ingredient not recognized beforehand. (other example would be the BA038)
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DC-ATE:
Well, there just might be a time when those computer limitations NEED to be exceeded. If the airplane can't handle it, then there might just be something wrong with the design.
Well, there just might be a time when those computer limitations NEED to be exceeded. If the airplane can't handle it, then there might just be something wrong with the design.
It's a *massive* misconception that the A320 FBW system is there to "tell the pilot what to do" or "stop the pilot 's natural ability to command". The A320 FBW will do *exactly* what the pilot tells it, and stay there as long as it is possible to maintain the attitude commanded.
If you think you'll need more than 67 degrees of roll to get out of a situation in an airliner I'd be as concerned as to your abilities as you are about the A320's!
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DC-ATE,
Save the airplane? The computer limits the forces on the aircraft to design limits (with a margin, I assume). If you fly the aircraft manually, how do you know where these limits are?
If the airplane can't handle it, then there might just be something wrong with the design.
Whatever it takes to save the airplane.