Air Asia A320

[pembquist]

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.

[Ripsnort]

Don't get too confused. Just remember, if you are going make sure it's a Boeing. 

[NGXPilot]

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/

[pembquist]

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.

[pembquist]

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.

[Zimme83]

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.

[earl1937]

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.

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!

[WaffenVW]

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!

[FTJR]

The Air Asia A320 crash had nothing to do with the "yoke vs sidestick" debate.

The captain got out of his seat and  pulled a circuit breaker, which is specifically NOT to be pulled in flight.

On top of that, they were in an active area of CB's

[Zimme83]

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.   

[colmbo]

and beyond that if the joysticks are in conflict the computer just sums them.

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.

[earl1937]

Yes! Ban everything new! Cables and rods is the concept, back in the old days noone ever crashed an airliner.

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.

[Zimme83]

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.

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...

[FTJR]

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.

[Serenity]

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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.