General Forums => The O' Club => Topic started by: pembquist on December 01, 2015, 06:00:46 PM
Title: Air Asia A320
Post by: pembquist on December 01, 2015, 06:00:46 PM
Ok, once again I am baffled by some of the finer points of the airbuses and for all I know what is now normal in big airplanes. Among other things, I don't understand how you can design a flight control system that is partially controlled by two joysticks that can be operated independently, and beyond that if the joysticks are in conflict the computer just sums them. I don't THINK this is an exageration but I hope it is. I especially don't understand how with the computer/autopilot thingy reverting to the least assisted "law" you would......oh nevermind.
Title: Re: Air Asia A320
Post by: Ripsnort on December 01, 2015, 07:03:22 PM
Don't get too confused. Just remember, if you are going make sure it's a Boeing. :P
Title: Re: Air Asia A320
Post by: NGXPilot on December 01, 2015, 08:37:51 PM
The yoke will always be superior to sidestick. I've never personally flown Boeing / Airbus aircraft, but from the looks of it, it seems a yoke allows for much more precise, minute changes. I could never understand how a stick would be better than a yoke, especially that following a flight director on the exact can be difficult in itself sometimes. Personally, I don't know much about Airbus FBW system because it's a closely guarded secret of the company as far as I know. Good documentation on it is few and far between.
The best thing you could do is ask a 320 pilot on how it all works, and I'm sure it's been talked about plenty here:http://www.airlinepilotforums.com/ (http://www.airlinepilotforums.com/)
Title: Re: Air Asia A320
Post by: pembquist on December 02, 2015, 12:45:51 AM
The general outline is pretty easy to read about, the "laws" which seem like feature levels of software aid that change as sensors or equipment fails, (when its all working you can pull full aft on the stick and it will fly best glide or anyway won't stall, when it isn't you get Airfrance if you manhandle it while the captain is in the toilet.) Which all seems great except that some of the accidents seem to happen when the pilots behave as if they have forgotten how the system works when it busts a little. The joystick thing, its not degree of precision its that you have two joysticks and one can be pushed forward and the other pulled back simultaneously. If there is a conflict from the control inputs the computer compromises. I just can't understand why you would ever allow control sticks to not both move when one is moved. I don't believe I am spreading misinformation, there is an excellent article by William Langwiesche in Vanity Fair about it, (read it a while ago,) which is where my understanding of how airbuses work comes from, (that and the more general bowels of the internet.) Along with talking about the Air France crash he describes the evolution of the Airbus approach, if I remember right he said it is based around cockpit resource management and expects a high degree of crew communication. But when the toejam hits the fan it seems like you would want no ambiguity about what position the controls are in without having to talk about it.
Title: Re: Air Asia A320
Post by: pembquist on December 02, 2015, 12:50:49 AM
Here is the relevant quote from Langewiesche's article:
This is not the time for a dissertation on the Airbus flight-control system, which is criticized by Boeing, but to the extent that it embodies a mistake in design, it is that the pilot’s and co-pilot’s side-sticks are not linked and do not move in unison. This means that when the Pilot Flying deflects his stick, the other stick remains stationary, in the neutral position. If both pilots deflect their sticks at the same time, a DUAL INPUT warning sounds, and the airplane responds by splitting the difference. To keep this from causing a problem in the case of a side-stick jam, each stick has a priority button that cuts out the other one and allows for full control. The arrangement relies on clear communication and good teamwork to function as intended. Indeed, it represents an extreme case of empowering the co-pilot and accepting C.R.M. into a design. More immediately, the lack of linkage did not allow Robert to feel Bonin’s flailing.
Title: Re: Air Asia A320
Post by: Zimme83 on December 02, 2015, 01:00:58 AM
AF 447 was about a lot more than just the sidesticks. Airbus safety record is extremley good so it is not a big issue. Side stick or not is a boeing vs airbus fanboy debate. It works either way. There are accidents that could have been avoided with a side stick instead of a yoke too.
Title: Re: Air Asia A320
Post by: earl1937 on December 02, 2015, 03:51:28 AM
AF 447 was about a lot more than just the sidesticks. Airbus safety record is extremley good so it is not a big issue. Side stick or not is a boeing vs airbus fanboy debate. It works either way. There are accidents that could have been avoided with a side stick instead of a yoke too.
:airplane: I play golf quite often with a major carrier pilot, who has flown the Airbus and now is on the MD88 as a captain. We have discussed the "stick" issue quite a bit and he is very positive that he can control the aircraft much better with a "yoke" than with a "side" stick! Maybe Airbus needs to consider a "stick" between the legs set up, with a linkage between the two under the floor and that would eliminate the inter action conflict which exist with the current set up! But we know that would be to "simple" of a fix for an engineer, it has to be complicated in his mind because of the challenge of designing a better "mouse trap"! Oh, don't worry about test flying the thing by the public, we will get all the bugs out in due time, but not sure how many lives it will cost!
Title: Re: Air Asia A320
Post by: WaffenVW on December 02, 2015, 04:21:29 AM
Yeah what a bunch of morons over at Airbus. How could anyone think that a side stick would be the best way to control an aircraft! What were they thinking! Next thing you know, they'll be making fighter jets with this God awful contraption they call fly-by-wire too! We'll lose every air war like... EVAR!
:airplane: I play golf quite often with a major carrier pilot, who has flown the Airbus and now is on the MD88 as a captain. We have discussed the "stick" issue quite a bit and he is very positive that he can control the aircraft much better with a "yoke" than with a "side" stick! Maybe Airbus needs to consider a "stick" between the legs set up, with a linkage between the two under the floor and that would eliminate the inter action conflict which exist with the current set up! But we know that would be to "simple" of a fix for an engineer, it has to be complicated in his mind because of the challenge of designing a better "mouse trap"! Oh, don't worry about test flying the thing by the public, we will get all the bugs out in due time, but not sure how many lives it will cost!
Yes! Ban everything new! Cables and rods is the concept, back in the old days noone ever crashed an airliner.
I dont see why this topic is relevant, it had nothing to do with Air Asia crash (as stated) Side stick vs yoke is btw the least difference between the Boeing and Airbus. Airbus use a Fly-by-wire system that are similar to the ones used on every modern fighter, the computers decides if a control input is within the limits, Boeing has no such limitation but uses artificial feed back to prevent pilots from overstressing the plane. (simulates heavy controls). Both systems works perfectly fine. Having a computer that prevents the pilot from stalling have a lot of advantages. In the case of AF 447 the plane went into an alternate mode, the computers stopped filtering the inputs and left the plane in the hands of the pilots.
Planes crashing because of pilots pulling back on the stick after a stall is nothing new, it has happen as long as people have flown. If you go down the natural reaction is to pull up. Accidents like AF 447 has occurred hundreds of times over the years, regardless of cockpit designs. Its about pilot training.
Title: Re: Air Asia A320
Post by: colmbo on December 02, 2015, 07:48:31 AM
Yes! Ban everything new! Cables and rods is the concept, back in the old days noone ever crashed an airliner.
:airplane: To my knowledge, there was never a crash which resulted from a loss of control, due to flight controls being incapacitated due to mechanical failure. Almost all aircraft crashes through the 90's were mostly pilot error, in one way or the other! there were some accidents, due to loss of flight control because of cargo shift and I almost had a bad situation once with a DC-3 loaded with metal, which the pallets in back had broke loose due to turbulence around some CB's over the Gulf! When I landed at the nearest airport that I could get to, I landed in a 3 point stance, with full forward elevator! I had even rolled the elevator trim tab all the way to the "up" position, in order to get that extra leverage for control! I doubt if I could have maintained control for another 10 or 15 minutes.
Title: Re: Air Asia A320
Post by: Zimme83 on December 02, 2015, 08:14:58 AM
:airplane: To my knowledge, there was never a crash which resulted from a loss of control, due to flight controls being incapacitated due to mechanical failure. Almost all aircraft crashes through the 90's were mostly pilot error, in one way or the other! there were some accidents, due to loss of flight control because of cargo shift and I almost had a bad situation once with a DC-3 loaded with metal, which the pallets in back had broke loose due to turbulence around some CB's over the Gulf! When I landed at the nearest airport that I could get to, I landed in a 3 point stance, with full forward elevator! I had even rolled the elevator trim tab all the way to the "up" position, in order to get that extra leverage for control! I doubt if I could have maintained control for another 10 or 15 minutes.
Most crashes are due to pilot error, thats why computers are used to assist the pilots and preventing them from doing those errors. Qantas 32 is a good example of the advantages with FBW, despite loss of a lot of vital system the computers did the job of keeping the plane in the air so the pilots could focus on getting it back on the ground instead of fighting to keep the plane flying.
Quote
To my knowledge, there was never a crash which resulted from a loss of control, due to flight controls being incapacitated due to mechanical failure
Loss of hydraulic pressure have brought down more than one plane over the years...
Title: Re: Air Asia A320
Post by: FTJR on December 02, 2015, 09:32:46 AM
A friend of mine flys the 320 for a living. He has told me that the Captains stick has priority if both are being used.
Incorrect. There is a "take over" button on each stick, the logic is the last person to push the "take over" button has priority. The other person has to release and press their button to resume control. If they're doing that, then there is a bigger problem in the cockpit then how the plane is designed.
Title: Re: Air Asia A320
Post by: Serenity on December 02, 2015, 10:12:44 AM
I'm quoting all of you, because you ALL bit off on the sidestick-vs-yoke, rather than the more important argument: "Why can both controls be moved in opposite directions?!"
The original post wasn't so much about the physical object you're holding, but rather the fact that whatever object it is can move in two different directions at once.
I'm no commercial pilot, my personal experience is fairly limited (SGS-232, SGS-233, Lark, Samba XXL, Cessna 172, Cessna 182, Cessna 206, T-6B, trivial time at the controls of a C-17 and CH-53E), but EVERY SINGLE ONE OF THESE AIRCRAFT had something in common: When one [insert control object here] moves, the other moves in the exact same direction, at the same rate. To my knowledge, it has been this way throughout history. And for a good reason. Airplanes are not inherently more dangerous than other objects, but they are IMMENSELY unforgiving. From experience, when things go wrong, they go wrong quickly, and you have ZERO time to discuss the matter. I've done everything from dodging birds and deer, to losing control surfaces, to hydraulics, and plenty of other issues among most of these aircraft, and I can count on one hand the number of times I've had time to do so much as say "oh $%#@!!!" before having to do something fairly drastic with the controls. Even in the T-6, er brief before every flight, "If you see something AND HAVE TIME, say it. If not, grab the controls, and muscle it over to avoid the situation. If you feel me jerk the controls away, let it go, I see something you don't, AND TALK ABOUT IT WHEN WE HAVE TIME." There are MANY situations where you don't have time to discuss what's happening, but in every other aircraft design, if someone sees something and slams the stick over, he doesn't have to say anything to the other pilot, that guy can FEEL that something is being done.
Title: Re: Air Asia A320
Post by: WaffenVW on December 02, 2015, 10:30:06 AM
Well, to my knowledge none of the aircraft you mentioned have side sticks. How do they do it on the F-16B/D/F?
Title: Re: Air Asia A320
Post by: earl1937 on December 02, 2015, 10:50:19 AM
Most crashes are due to pilot error, thats why computers are used to assist the pilots and preventing them from doing those errors. Qantas 32 is a good example of the advantages with FBW, despite loss of a lot of vital system the computers did the job of keeping the plane in the air so the pilots could focus on getting it back on the ground instead of fighting to keep the plane flying.
Loss of hydraulic pressure have brought down more than one plane over the years...
:airplane: Most aircraft, back in the "day", so to speak, did not have hydraulic controls, but some had hydraulic assisted controls, but you could still fly the thing if you had no hydraulics'. Most aircraft had hydraulics' to lower gear, flaps and brake systems. The biggest reason they ever went to FBW systems to begin with, had nothing to do with safety, it was about the weight saved in the design of the aircraft. True, there was a lot of thought given to taking the "flight" decisions away from the pilots when they screwed up, but the computer CAN'T think! I remember a Airbus test flight many years ago and there is a video of this on utube, but I don't have time to look it up, the thing took off, climbed about 50 fifty feet and crashed straight ahead into some woods! All the pilots had to do to save this thing was just push the thrust levels full up and take command away from the computer and they would have saved the aircraft and lived! I know I am not going to "win" this discussion in any fashion, but there are some things on the new modern aircraft of today, which I wish we could do with out and FBW is one of them. Case in point is the "knob" on the eyebrow of the instrument panel, by which the pilots can control the speed of the aircraft! Wouldn't pilot proficiency be on a much high scale, if they had to fly the thing all the time manually? I think it would!
Title: Re: Air Asia A320
Post by: Serenity on December 02, 2015, 10:57:00 AM
Well, to my knowledge none of the aircraft you mentioned have side sticks. How do they do it on the F-16B/D/F?
Does it matter? The issue in question isn't the location of the stick, but rather the effect of not linking the controls.
Title: Re: Air Asia A320
Post by: WaffenVW on December 02, 2015, 11:04:31 AM
On commercial aircraft only one pilot should be in command at any one time, and in the scarebus there's an audible alarm if both sticks are used simultaneously.
Title: Re: Air Asia A320
Post by: Zimme83 on December 02, 2015, 11:05:41 AM
:airplane: Most aircraft, back in the "day", so to speak, did not have hydraulic controls, but some had hydraulic assisted controls, but you could still fly the thing if you had no hydraulics'. Most aircraft had hydraulics' to lower gear, flaps and brake systems. The biggest reason they ever went to FBW systems to begin with, had nothing to do with safety, it was about the weight saved in the design of the aircraft. True, there was a lot of thought given to taking the "flight" decisions away from the pilots when they screwed up, but the computer CAN'T think! I remember a Airbus test flight many years ago and there is a video of this on utube, but I don't have time to look it up, the thing took off, climbed about 50 fifty feet and crashed straight ahead into some woods! All the pilots had to do to save this thing was just push the thrust levels full up and take command away from the computer and they would have saved the aircraft and lived! I know I am not going to "win" this discussion in any fashion, but there are some things on the new modern aircraft of today, which I wish we could do with out and FBW is one of them. Case in point is the "knob" on the eyebrow of the instrument panel, by which the pilots can control the speed of the aircraft! Wouldn't pilot proficiency be on a much high scale, if they had to fly the thing all the time manually? I think it would!
That crash had nothing to do with the Fly by wire system, it was a pilot error and did not occur as you describe it. https://en.wikipedia.org/wiki/Air_France_Flight_296 If something it was a false belief that the FBW system would save them from anything, it did prevent them from stalling but they had no speed to climb since they were in a near stall position.
Like it or not: FRW and computers have made commercial aviation a lot safer, it cannot eliminate all risks but it helps the pilots to avoid most of the common mistakes. If pilots had to fly manually they would be better pilots for sure, but they would also crash a lot more often. We cannot have commercial jets flying with a compass and a clock just because it was the way it was done in the past. Commercial aviation is about moving people and stuff from A to B in the safest and most efficient way. If you want to experience the freedom flying can give you then General aviation is there for you. I prefer to fly that way but just because I do it doesnt mean that i want the guys in the airliner im riding with to do the same.
Title: Re: Air Asia A320
Post by: Serenity on December 02, 2015, 12:15:43 PM
On commercial aircraft only one pilot should be in command at any one time, and in the scarebus there's an audible alarm if both sticks are used simultaneously.
On ANY airplane, only one pilot should be in command.
Other things that SHOULD happen: -Birds should avoid planes -Engines and equipment should work -Storms should not appear without warning -Pilots should constantly be in close communication with their crew
Just because something SHOULD happen doesn't mean there aren't extenuating circumstances. The thing with having more than one set of eyes in the cockpit is occasionally one set sees something the other doesn't, and in these circumstances, the one to see it may not be the one who SHOULD be in charge, but time may not allow communication of both the issue and the corrective action.
While you will say "There's a 'takeover button' for that!" it's not an end-all excuse. What if both see the situation, both push the takeover button, neither knows what the other is doing, the situation becomes more frantic as the one NOT in control doesn't realize the other is acting on the airplane. Beyond that, as a firearms guy, the one thing you hear a million times is "When your life is on the line, fine motor skills are the first thing that goes". How often do you think these pilots drill to press that little button in an emergency? And keep in mind, I speak from experience when I say emergency drills in a simulator are NOTHING like drills in the actual airplane.
Title: Re: Air Asia A320
Post by: WaffenVW on December 02, 2015, 12:27:11 PM
Pretty.
Title: Re: Air Asia A320
Post by: WaffenVW on December 02, 2015, 12:30:51 PM
Bruce Dickinson flies the A320! :rock
Title: Re: Air Asia A320
Post by: pembquist on December 02, 2015, 01:40:34 PM
I wasn't contrasting side sticks to yokes, Serenity understands. If what Columbo says is correct across all implentations than it is a moot point. The fact of the matter is that in the reports that I have read both the Air France and the Air Asia crashes had instances of two crew members giving opposite uncommunicated control inputs under severe stress. Unfortunately at the time they were doing this the computer was in the lowest state of "law" so staying within the flight envelope was up to the crew which as far as I can tell is an extremely rare event. I am saying that for that rare event when the fly by wire is degraded it seems like the existing design is suboptimal. And as for training, which is not airbuses fault, it seems like the crews had not trained enough to recognize and react when they were more directly in control of the aircraft, thats why they call it pilot error.
Before airbus crews flew perfectly good airplanes into the ground when their instruments went wonky so I'm NOT BLAMING AIRBUS for the crashes, I'm just wondering why they have this one particular design feature that doesn't help offset human fraility but aggravates it and as a lay person seems kooky.
I'd buy the argument that statistically airbuses probably prevent way more crashes than they "cause", (just like ABS and stability control in autos,) but that isn't a reason not to scratch against the itch of suboptimal crisis-ergo design.
Title: Re: Air Asia A320
Post by: NatCigg on December 02, 2015, 02:01:27 PM
the pilots crashed the plane.? ok. we can fix that right? better training and wallah, and besides the point, how many times has this technical flaw been correctly handled by the pilots? but what is really scary is how come a faulty solder joint went a year without fixing until the plane crashed?
"In the AirAsia disaster, the system that regulates the plane's rudder movement kept malfunctioning because of a cracked solder joint. Aircraft maintenance records found it had malfunctioned 23 times in the year before the crash, and the interval between those incidents became shorter in the three months prior to the crash, Indonesia's National Transport Safety Committee said in a report."
Title: Re: Air Asia A320
Post by: Serenity on December 02, 2015, 04:42:00 PM
Incorrect. There is a "take over" button on each stick, the logic is the last person to push the "take over" button has priority. The other person has to release and press their button to resume control. If they're doing that, then there is a bigger problem in the cockpit then how the plane is designed.
"It's mine."
"No, mine."
"NO. Mine."
"It's mine."
"Mine!"
"No! Mine!"
"MINE!"
Title: Re: Air Asia A320
Post by: WaffenVW on December 02, 2015, 05:40:13 PM
Pilots behave that way? They should all be shot! :uhoh
Title: Re: Air Asia A320
Post by: FTJR on December 02, 2015, 06:10:31 PM
I'm quoting all of you, because you ALL bit off on the sidestick-vs-yoke, rather than the more important argument: "Why can both controls be moved in opposite directions?!"
The original post wasn't so much about the physical object you're holding, but rather the fact that whatever object it is can move in two different directions at once.
I'm no commercial pilot, my personal experience is fairly limited (SGS-232, SGS-233, Lark, Samba XXL, Cessna 172, Cessna 182, Cessna 206, T-6B, trivial time at the controls of a C-17 and CH-53E), but EVERY SINGLE ONE OF THESE AIRCRAFT had something in common: When one [insert control object here] moves, the other moves in the exact same direction, at the same rate. To my knowledge, it has been this way throughout history. And for a good reason. Airplanes are not inherently more dangerous than other objects, but they are IMMENSELY unforgiving. From experience, when things go wrong, they go wrong quickly, and you have ZERO time to discuss the matter. I've done everything from dodging birds and deer, to losing control surfaces, to hydraulics, and plenty of other issues among most of these aircraft, and I can count on one hand the number of times I've had time to do so much as say "oh $%#@!!!" before having to do something fairly drastic with the controls. Even in the T-6, er brief before every flight, "If you see something AND HAVE TIME, say it. If not, grab the controls, and muscle it over to avoid the situation. If you feel me jerk the controls away, let it go, I see something you don't, AND TALK ABOUT IT WHEN WE HAVE TIME." There are MANY situations where you don't have time to discuss what's happening, but in every other aircraft design, if someone sees something and slams the stick over, he doesn't have to say anything to the other pilot, that guy can FEEL that something is being done.
FTJR flies commercial airliners for a living. I differ to him to be honest.
Title: Re: Air Asia A320
Post by: Serenity on December 02, 2015, 06:22:49 PM
He hasn't really commented on the controls moving in different direction though, he was arguing yoke vs sidestick.
Because the topic is about the Air Asia A320 crash, not the controls, the captain pulled a CB that should not have been pulled in flight, did it affect the flight controls yes, were they moving in different directions (in the AAsia crash) no, and there was no input whatsoever for 9 seconds after things went wrong.
The computers average out the combined sidestick inputs, i.e someone pulls full up, the other pushes full down, the result is neutral. If you have a dual input, it tells you both with a light and aural warning. In this case it seems that a conflicting command was given "pull down" so the FO, who I believe was a French national (English not his first language?) may have been confused as to what he should have been doing, which would be really understandable as it was going very wrong, very quickly.
I was not arguing yoke vs sidestick, i was saying that argument was not applicable to the topic. and I corrected one misconception.
If you want to discuss the flight control laws, im happy too, but open a new discussion.
Hi Karaya <S>
Title: Re: Air Asia A320
Post by: pembquist on December 02, 2015, 11:22:19 PM
Because the topic is about the Air Asia A320 crash, not the controls, the captain pulled a CB that should not have been pulled in flight, did it affect the flight controls yes, were they moving in different directions (in the AAsia crash) no, and there was no input whatsoever for 9 seconds after things went wrong.
I started the topic and it is about both the airasia crash and about the controls. My curiosity is peaked based on among other things page 59 of the final accident report http://kemhubri.dephub.go.id/knkt/ntsc_aviation/aaic.htm (http://kemhubri.dephub.go.id/knkt/ntsc_aviation/aaic.htm)
This clearly shows the captains side stick is in a 15 degree pitch and 14 degree roll position while the copilots stick is in -16 degrees pitch and -7 degrees roll.
I am not saying that having sticks not working like they do in piper cubs is the reason the plane crashed, (the pilots are supposed to know how to fly the plane in all modes after all,) but to me it seems inexplicable that you would put pilots in the position of having two floppy joysticks competing with each other in a moment of crisis. I am sure there are good reasons for the design but I haven't heard anyone explain what those reasons are and I would like to know because I am interested. Does anyone know why the decision was made, (because it was a decision,) to have unconnected, (mechanically or virtually,) flight controls? All I can think is that it is a way to have redundant control sticks as a jam in one will not affect the other.
Title: Re: Air Asia A320
Post by: FTJR on December 03, 2015, 03:01:26 AM
I started the topic and it is about both the airasia crash and about the controls. My curiosity is peaked based on among other things page 59 of the final accident report http://kemhubri.dephub.go.id/knkt/ntsc_aviation/aaic.htm (http://kemhubri.dephub.go.id/knkt/ntsc_aviation/aaic.htm)
This clearly shows the captains side stick is in a 15 degree pitch and 14 degree roll position while the copilots stick is in -16 degrees pitch and -7 degrees roll.
I am not saying that having sticks not working like they do in piper cubs is the reason the plane crashed, (the pilots are supposed to know how to fly the plane in all modes after all,) but to me it seems inexplicable that you would put pilots in the position of having two floppy joysticks competing with each other in a moment of crisis. I am sure there are good reasons for the design but I haven't heard anyone explain what those reasons are and I would like to know because I am interested. Does anyone know why the decision was made, (because it was a decision,) to have unconnected, (mechanically or virtually,) flight controls? All I can think is that it is a way to have redundant control sticks as a jam in one will not affect the other.
Thanks, let me look at your link, I have to go work for a few days so I wont have time to digest it straight away.
Title: Re: Air Asia A320
Post by: WaffenVW on December 03, 2015, 07:22:49 AM
I've read the report and I'm astounded that they call it a complex emergency situation. Is flying a plane manually a complex emergency situation? It is just one more case of morons failing at flying a perfectly flyable aircraft by deliberately causing a stall.
Title: Re: Air Asia A320
Post by: NatCigg on December 03, 2015, 08:05:22 AM
I've read the report and I'm astounded that they call it a complex emergency situation. Is flying a plane manually a complex emergency situation? It is just one more case of morons failing at flying a perfectly flyable aircraft by deliberately causing a stall.
ht always said full nose down and opposite rudder :old:
Title: Re: Air Asia A320
Post by: Busher on December 03, 2015, 08:56:10 PM
I started the topic and it is about both the airasia crash and about the controls. My curiosity is peaked based on among other things page 59 of the final accident report http://kemhubri.dephub.go.id/knkt/ntsc_aviation/aaic.htm (http://kemhubri.dephub.go.id/knkt/ntsc_aviation/aaic.htm)
This clearly shows the captains side stick is in a 15 degree pitch and 14 degree roll position while the copilots stick is in -16 degrees pitch and -7 degrees roll.
I am not saying that having sticks not working like they do in piper cubs is the reason the plane crashed, (the pilots are supposed to know how to fly the plane in all modes after all,) but to me it seems inexplicable that you would put pilots in the position of having two floppy joysticks competing with each other in a moment of crisis. I am sure there are good reasons for the design but I haven't heard anyone explain what those reasons are and I would like to know because I am interested. Does anyone know why the decision was made, (because it was a decision,) to have unconnected, (mechanically or virtually,) flight controls? All I can think is that it is a way to have redundant control sticks as a jam in one will not affect the other.
Pardon me for interjecting. As a retired airline Captain, I'd like to point out that the control design of the airbus series has proven to be reliable and cost effective for all the airlines who chose them for their fleet. I have never been type endorsed on any of them even though my airline had many types - I preferred the competition. I will be very interested in FTJR's comments on the aircraft.
This strikes me clearly as a CRM failure accident. Airlines with a strong safety culture and ALPA spend countless dollars and hours developing a training a team approach to cockpit operations. Both pilots should be working to assure that the airplane is never placed in a situation where either of them needs to use exceptional "stick and rudder" skills to correct a problem. In any case, only the "pilot flying" should be manipulating the airplane while the "pilot monitoring" offers information to assist in a disciplined fashion.
Do not fault "fly by wire" design. It exists effectively not only in Airbus but Boeing as well (B777 and B787).
Two pilots fighting over the controls whether they be conventional or computerized is a recipe for disaster.
Title: Re: Air Asia A320
Post by: pembquist on December 03, 2015, 09:44:32 PM
Hey Busher:
Sure its a great system.
I said I'd believe it prevents more accidents than it "causes" (don't know how else to put it)
When did I fault fly by wire?
The cause of the accident is that a defective component lead the captain to pull a circuit breaker he wasn't supposed to which caused the FBW to enter alternate law instead of normal law, the copilot couldn't control the airplane under alternate law for some reason, (supposed to be in his wheelhouse I would think,) thus putting the airplane in an upset that the crew could not recover from.
I still think it is weird to have two controls that can be placed in opposition to each other. Here is how Airbus addresses the difficulty posed by independent controllers:
Sidestick priority logic ‐ When only one pilot operates the sidestick, it sends his control signals to the computers. ‐ When the pilots move both side sticks simultaneously in the same or opposite direction and neither takes priority, the system adds the signals of both pilots algebraically. The total is limited to the signal that would result from the maximum deflection of a single sidestick. Note: In the event of simultaneous input on both sidesticks (2° deflection off the neutral position in any direction) the two green SIDE STICK PRIORITY lights on the glare shield come on and “DUAL INPUT” voice message is activated. A pilot can deactivate the other stick and take full control by pressing and keeping pressed his priority takeover pushbutton. For latching the priority condition, it is recommended to press the takeover push button for more than 40 s. This allows the pilot to release his takeover push button without losing priority. However, a pilot can at any time reactivate a deactivated stick by momentarily pressing the takeover push button on either stick. If both pilots press their takeover pushbuttons, the pilot that presses last gets priority. Note: If an autopilot is engaged, any action on a takeover pushbutton disengages it. In a priority situation ‐ A red light comes on in front of the pilot whose stick is deactivated. ‐ A green light comes on in front of the pilot who has taken control, if the other stick is not in the neutral position (to indicate a potential and unwanted control demand). Note: If the aircraft is on the ground and commencing its takeoff run and one stick is deactivated, this triggers the takeoff “CONFIG” warning.
Title: Re: Air Asia A320
Post by: Busher on December 03, 2015, 10:06:51 PM
"The cause of the accident is that a defective component lead the captain to pull a circuit breaker he wasn't supposed to"
I say again.... It still strikes me as a CRM accident. Why would a pilot touch a CB in flight unless directed to do so by Emergency Checklist?
As to independent control systems.... is it even relevant if only one pilot should, in a properly managed cockpit, be manipulating the flight controls.
I am sorry but I cannot see fault in the equipment.
With respect Sir.
Title: Re: Air Asia A320
Post by: Serenity on December 04, 2015, 02:10:05 AM
"The cause of the accident is that a defective component lead the captain to pull a circuit breaker he wasn't supposed to"
I say again.... It still strikes me as a CRM accident. Why would a pilot touch a CB in flight unless directed to do so by Emergency Checklist?
As to independent control systems.... is it even relevant if only one pilot should, in a properly managed cockpit, be manipulating the flight controls.
I am sorry but I cannot see fault in the equipment.
With respect Sir.
We're not saying THIS INDIVIDUAL CRASH is caused ENTIRELY by the sticks not being linked. What IS being posed is this: There seems to be ZERO good arguments for NOT linking the controls. There are MANY good arguments for linking them. Thus, as has been asked many times, is there any apparent logic to NOT having controls linked?
Yes, THIS incident was CRM. Yes, you can trace almost every airliner crash down to CRM, and CRM COULD have saved the situation. That being said, while CRM is the root cause, you cannot deny that these sticks being in conflicting positions indicates that perhaps had the sticks been linked, lacking non-verbal communication, the tactile feedback of the stick may have aided in the situation.
So again, this individual incident aside, what is the possible logic behind not linking the sticks?
(If that came off as disrespectful, I'm sorry, but it feels like pembquist and I are talking to brick walls. Everyone is quick to answer the question we're NOT asking.)
Title: Re: Air Asia A320
Post by: Busher on December 04, 2015, 10:20:15 AM
No offense or disrespect at all gentlemen. If the question is as basic as to why Airbus does what it does, I cannot comment. It has always struck me that their vision of flight control could lead to computer techs operating airliners with no "basic operating skills" (a United Airlines term) required.
I never wanted to fly one
<S>
Title: Re: Air Asia A320
Post by: Serenity on December 04, 2015, 01:33:25 PM
No offense or disrespect at all gentlemen. If the question is as basic as to why Airbus does what it does, I cannot comment. It has always struck me that their vision of flight control could lead to computer techs operating airliners with no "basic operating skills" (a United Airlines term) required.
I never wanted to fly one
<S>
Thank you. THAT'S what's driving me nuts. I don't think it caused the crash, but from experience, I've seen a LOT of value in linked controls, and nothing to be gained by controls which aren't linked.
Title: Re: Air Asia A320
Post by: pembquist on December 04, 2015, 02:26:10 PM
No offense or disrespect at all gentlemen. If the question is as basic as to why Airbus does what it does, I cannot comment. It has always struck me that their vision of flight control could lead to computer techs operating airliners with no "basic operating skills" (a United Airlines term) required.
I never wanted to fly one
<S>
No offense taken or intended. Untill I hear otherwise I am going to assume that Airbus viewed the chance of an incapicitated pilot or mechanical issue causing a jam on one stick as more likely than a failure of CRM and so made the sticks independent of each other. Then to address the obvious chance of conflict they came up with warning lights and signals and a slightly complicated takeover button. It seems counter intuitive but perhaps the thinking is that you are trading away an extremely dangerous single point failure (jamming of pitch and roll control) in exchange for a failure mode that requires multiple failures (not in normal law, breakdown of crm, flight skills for the law and conditions inadequate,) to become dangerous. I don't know but I'd like to understand the reason.
This reminds me of Abraham Wald, a Boffin during WW2 who made the statistical argument that can be described in a simplified way as: Don't add armor to airplanes in the places that returning airplanes have bullet holes add it in the places that don't have bullet holes because thats probably where the bullet holes were in the airplanes that didn't return.
Title: Re: Air Asia A320
Post by: WaffenVW on December 04, 2015, 02:40:26 PM
What I gather from Airbus is that they're trying to remove the 'human component' as much as possible, because it is by far the one system component that causes the most accidents. In this case the machine was flying the plane, but something broke and the machine didn't know what to do with it. So it handed the plane and 162 lives over to two humans, who promptly crashed it by doing insane and illogical things, as humans are prone to do.
Title: Re: Air Asia A320
Post by: earl1937 on December 04, 2015, 04:07:25 PM
That crash had nothing to do with the Fly by wire system, it was a pilot error and did not occur as you describe it. https://en.wikipedia.org/wiki/Air_France_Flight_296 If something it was a false belief that the FBW system would save them from anything, it did prevent them from stalling but they had no speed to climb since they were in a near stall position.
Like it or not: FRW and computers have made commercial aviation a lot safer, it cannot eliminate all risks but it helps the pilots to avoid most of the common mistakes. If pilots had to fly manually they would be better pilots for sure, but they would also crash a lot more often. We cannot have commercial jets flying with a compass and a clock just because it was the way it was done in the past. Commercial aviation is about moving people and stuff from A to B in the safest and most efficient way. If you want to experience the freedom flying can give you then General aviation is there for you. I prefer to fly that way but just because I do it doesnt mean that i want the guys in the airliner im riding with to do the same.
:airplane: Sorry "Charlie" (the tuna), but you are wrong sir! The crash I am referring to is this one:
https://www.youtube.com/watch?v=-kHa3WNerjU
The crew had taken off and after it assumed the VR attitude, the aircraft gained about 50 feet AGL, and proceeded to fly directly into a forest of trees dead ahead and all they would have had to do was knock off the computer and push the thrust levers full up and the crash would have been canceled! The computer "screwed" up and that is my point about FBW, I know that is the way we are going in the future and someday, they will be completely trust worthy, but don't think we are to that point yet! I called that friend of mine this afternoon, who now is a captain on a MD88 and he told me that which ever "stick" moved first, had priority, but the captain could always "over ride" the first officers "stick". It normally stayed in the neutral position unless the captain over rode it. I am referring to the first officer having command of the flight controls! I know that I am old fashioned I guess, but like I said in another post, I have never heard of an aircraft crashing due to flight controls becoming in active of their own accord, I am referring to cable and push rod flight control actuators. Another case in point was the crash off Long Island, where the co-pilots input on the rudder was so much, he broke off the vertical stabilizer and of course, down they came. (I know someone in here argued that you could fly with out a vertical stabilizer, but that is BS, you can't, not with a standard tail arrangement) There are aircraft which can fly without a vertical stab, but that is a all together different flight control system!
Title: Re: Air Asia A320
Post by: WaffenVW on December 04, 2015, 04:25:46 PM
Earl that is Air France 296 you're describing (the title of the youtube video you linked to is "Air France Flight 296 | Airbus A320 Crash" !!! :rolleyes:), but it did not happen the way you remember. It was incidentally the first crash of an A320. Read the wiki article Zimme83 linked to.
Title: Re: Air Asia A320
Post by: WaffenVW on December 04, 2015, 04:33:31 PM
Earl your second example was American Airlines Flight 587, the Airbus A300 that lost its vertstab. It remains the only fatal accident of any Airbus aircraft in North America, and it was an old A300 with NO FLY BY WIRE SYSTEM. Again a case of the human component failing.
Title: Re: Air Asia A320
Post by: earl1937 on December 04, 2015, 04:38:48 PM
Earl that is Air France 296 you're describing (the title of the youtube video you linked to is "Air France Flight 296 | Airbus A320 Crash" !!! :rolleyes:), but it did not happen the way you remember. It was incidentally the first crash of an A320. Read the wiki article Zimme83 linked to.
:headscratch: All I know about it is what the accident report states! If the crew had over rode the computer and pushed the thrust levels full up, it wouldn't have crashed. It reminded me of another crash, which had nothing to do with what we are discussing, a DC9 out of Washington National, with the deicing on the EPR probes turned off, in a snow storm, and the crew failed to recognize what was happening and did not push the "thrust levers" full forward, that to would have prevented a crash! I instructed for many years in a lot of different equipment, and one rule I had everyone implement, where or not it was in the book, if the nose of the aircraft is up, to any degree, in an emergency, push the "Dam+ throttles full forward"! I realize that there were some exceptions to that rule, but the point I wanted to make to the student was just this: "fly the aircraft first, then worry about any damage you might or might not do to the engines! As for as I know, I never had a student make a "sudden, unscheduled" arrival off field somewhere! Remember, there are three things in aviation which you need, but can never use and that is this" Runway behind you Altitude above you Fuel left in that red truck by the terminal
Title: Re: Air Asia A320
Post by: earl1937 on December 04, 2015, 04:42:42 PM
Earl your second example was American Airlines Flight 587, the Airbus A300 that lost its vertstab. It remains the only fatal accident of any Airbus aircraft in North America, and it was an old A300 with NO FLY BY WIRE SYSTEM. Again a case of the human component failing.
:airplane: Please forgive a 81, soon to be 82 year old mind, sometimes I forget the way things actually happened. That is why I quit flying solo about 5 years ago! My mind is ok I think, but there are a lot of "cob webs" in some corners of it! :old:
Title: Re: Air Asia A320
Post by: Zoney on December 04, 2015, 04:43:48 PM
Remember, there are three things in aviation which you need, but can never use and that is this" Runway behind you Altitude above you Fuel left in that red truck by the terminal
The only time you have too much fuel is when your plane is on fire.
Title: Re: Air Asia A320
Post by: WaffenVW on December 04, 2015, 04:49:07 PM
:headscratch: All I know about it is what the accident report states! If the crew had over rode the computer and pushed the thrust levels full up, it wouldn't have crashed."
To me that reads: "If the crew had done what they were supposed to do they wouldn't have flown a perfectly fine aircraft into the ground."
One thing that to my knowledge is unique to the A320 family is that it is the only mass produced air liner that hasn't killed anyone. There has been no fatal accidents involving the A320 series where the plane broke in a way that the pilots couldn't have saved it by doing their job properly. This Air Asia accident is a perfect example. All fatal accidents with the A320 have been attributed to pilot error or a deliberate act.
Title: Re: Air Asia A320
Post by: Busher on December 04, 2015, 05:39:22 PM
No offense taken or intended. Untill I hear otherwise I am going to assume that Airbus viewed the chance of an incapicitated pilot or mechanical issue causing a jam on one stick as more likely than a failure of CRM and so made the sticks independent of each other. Then to address the obvious chance of conflict they came up with warning lights and signals and a slightly complicated takeover button. It seems counter intuitive but perhaps the thinking is that you are trading away an extremely dangerous single point failure (jamming of pitch and roll control) in exchange for a failure mode that requires multiple failures (not in normal law, breakdown of crm, flight skills for the law and conditions inadequate,) to become dangerous. I don't know but I'd like to understand the reason.
This reminds me of Abraham Wald, a Boffin during WW2 who made the statistical argument that can be described in a simplified way as: Don't add armor to airplanes in the places that returning airplanes have bullet holes add it in the places that don't have bullet holes because thats probably where the bullet holes were in the airplanes that didn't return.
Control Jams have occurred. I believe it was this accident http://www.fss.aero/accident-reports/look.php?report_key=102
and the resulting NTSB report that caused the FAA to require all manufacturers of transport category aircraft (FAR Part 25) to have independent flight control systems between the Captain and First Officer that can be split with a simple action.....usually just a pull and turn-to-lock quadrant. I experienced jammed ailerons in my job about a year before retirement.....system saved my bacon and many more.
Title: Re: Air Asia A320
Post by: pembquist on December 04, 2015, 06:10:46 PM
Thanks Busher. So to be sure I understand this correctly, you have 2 sets of controls that each have there own control path to the flight surfaces. In ordinary operation the controls are connected to each other so that they move in unison, in an emergency they can be disconnected from each other so that the non compromised system can be used. Correct?
I am assuming that there is provision for jammed flight surfaces such that a jammed left aileron will not interfere with the operation of the right aileron, is this true?
I remember reading about a jam that I think was in an airliner and was caused by something as pedestrian as an object falling on the floor and blocking the slot one of the controls moved in. I'll try to look it up.
Title: Re: Air Asia A320
Post by: Busher on December 04, 2015, 06:46:15 PM
Thanks Busher. So to be sure I understand this correctly, you have 2 sets of controls that each have there own control path to the flight surfaces. In ordinary operation the controls are connected to each other so that they move in unison, in an emergency they can be disconnected from each other so that the non compromised system can be used. Correct?
I am assuming that there is provision for jammed flight surfaces such that a jammed left aileron will not interfere with the operation of the right aileron, is this true?
I remember reading about a jam that I think was in an airliner and was caused by something as pedestrian as an object falling on the floor and blocking the slot one of the controls moved in. I'll try to look it up.
Totally correct Sir!
Title: Re: Air Asia A320
Post by: WaffenVW on December 04, 2015, 07:03:20 PM
:airplane: Please forgive a 81, soon to be 82 year old mind, sometimes I forget the way things actually happened. That is why I quit flying solo about 5 years ago! My mind is ok I think, but there are a lot of "cob webs" in some corners of it! :old:
Nothing to forgive sir. We're just having a friendly discussion after all. :)
Title: Re: Air Asia A320
Post by: earl1937 on December 04, 2015, 11:45:19 PM
Thanks Busher. So to be sure I understand this correctly, you have 2 sets of controls that each have there own control path to the flight surfaces. In ordinary operation the controls are connected to each other so that they move in unison, in an emergency they can be disconnected from each other so that the non compromised system can be used. Correct?
I am assuming that there is provision for jammed flight surfaces such that a jammed left aileron will not interfere with the operation of the right aileron, is this true?
I remember reading about a jam that I think was in an airliner and was caused by something as pedestrian as an object falling on the floor and blocking the slot one of the controls moved in. I'll try to look it up.
Control Jams have occurred. I believe it was this accident http://www.fss.aero/accident-reports/look.php?report_key=102
and the resulting NTSB report that caused the FAA to require all manufacturers of transport category aircraft (FAR Part 25) to have independent flight control systems between the Captain and First Officer that can be split with a simple action.....usually just a pull and turn-to-lock quadrant. I experienced jammed ailerons in my job about a year before retirement.....system saved my bacon and many more.
Okay, THIS makes SO much more sense than the airbus model. I can understand the why in this, it solves the problem, without being incredibly weird in the day-to-day...
Title: Re: Air Asia A320
Post by: FTJR on December 05, 2015, 09:28:53 PM
Greetings, I read the report, (thanks for the link) and was horrified at the events. I have to agree with Busher it is a CRM case plus alot of missing training in general airmanship.
But of course that is not the question of why the controls are not linked in Airbus, I cant answer that, the aeroplane was introduced before I joined the airlines in 89, and there was certainly a huge distrust of the machine then.
My personal philosophy is that the company pays me to fly, I fly what they give me. The philosophy between Boeing and Airbus are "different", i've flown the 737(-200,-700/-800), the 767-300, A319/320 and currently the 330. I just passed up the B777 to wait for the A350, so I guess im comfortable with Airbus. Sorry if i cant answer your questions satisfactorily.
Title: Re: Air Asia A320
Post by: WaffenVW on December 10, 2015, 07:19:26 AM
A340 engine failure. What a horrible Swiss accent!