Pilot Commands TOGA; A320 lands anyway

[SaturnV]

From this week's "Aviation Week":

Incident Prompts Airbus
To Alter A320 AOA Limits
PIERRE SPARACO/TOULOUSE, FRANCE

Revised software, to be implemented soon, will increase pilots' authority over automated systems

In the wake of a serious landing incident, Airbus plans to revise the A319/A320 twinjets' automated angle-of-attack (AOA) protection.

Recently, a 150-seat A320, operated by an unspecified European carrier, made a hard landing, in nose-down attitude, despite the pilot-in-command's decision to go around and the application of maximum power. The aircraft's front landing gear collapsed, and the engine nacelles were damaged. Light turbulence but no wind shear had been reported to the flight crew before the nighttime ILS approach began.

An investigation team, supported by the European manufacturer's flight operations department, determined that during the final approach, the A320 entered into heavy turbulence at about 200 ft. altitude. Wind conditions were significantly more severe than initially reported to the flight crew, with up- and downdrafts and gusts that also involved an inversion of wind direction. The digital flight data recorder and additional inputs helped investigators determine that the A320 encountered strong tailwinds, a 1.25g-updraft, then a downdraft followed at 50 ft. by a tailwind gust.

DURING THE UPDRAFT, the flight crew applied a forward side stick input, then aft input to reduce the aircraft's increasing sink rate. As the Ground Proximity Warning System (GPWS) sounded, they moved engine throttles to takeoff/go around power, but the aircraft nevertheless touched down, according to Capt. Michel Brandt. He is Airbus' deputy director of flight operations support. He added that the A320's estimated vertical speed, when it impacted the runway, was 1,200 ft./min.

The recently completed investigation has shown that the combination of up and down wind gusts and the flight crew's actions on flight controls led the aircraft to hit the automated systems' high angle of attack protection and prevented a normal flare.

The incident was reproduced here in a full-flight simulator and led Airbus to a decision to modify the AOA protection's control laws to increase the flight crew's authority. Such a modification, which has been ratified by DGAC French civil aviation authority and European Joint Aviation Authorities, will cover all in-service A319s and A320s, but will not affect the stretched-fuselage A321.

The revised software is expected to be validated in June, and the retrofit program will be implemented rapidly, Brandt said. He added that in the shorter term, A319/A320 operators will temporarily apply precautionary measures in gusty wind conditions such as a slightly higher approach speed and immediate go-around in case of sink rate GPWS warning below 200 ft.

In an unrelated development, the British transport ministry's Air Accident Investigation Branch (AAIB) this month completed the investigation of a tail strike accident that occurred last year to a Lufthansa German Airlines A321.

DURING THE FINAL approach to Heathrow airport, the aircraft went below nominal glidepath, and the flight crew increased the attitude to reduce the rate of descent. The sink rate GPWS sounded, full aft side stick was applied, and the aircraft bounced on the runway after touching down for the second time. AAIB investigators determined that the aircraft's attitude peaked at 10.6 deg., just above the 9.7-deg. touch down limit with the main landing gear's oleos fully compressed. A similar incident occurred at Heathrow a few months earlier. Brandt noted that A321 landing tail strikes are not a noticeable concern and largely remain within tolerable limits.

[411A]

ScareBus, very bad news for pilots. Real pilots, not just system operators. To be avoided like the plague.

[wooof]

411A

Please for the benefit of all fellow PPRuNers could you tell us how many hours you have on the Airbus.

[planecrazi]

411A, What is your point that you are making?
This A320 landed with probably with no injury to anyone due to it's avanced flight laws and protection.Without this, who knows what would have happened? The Tri-Star didn't have this protection when it encountered the micro-burst in Dallas, if I remember. Both are good aeroplanes and I'm sure the crew were experienced in both cases. Airbus is now improving there aircraft to be even better. I don't believe one should stay away from an airbus because of it's technology. I enjoy the Airbus and believe it to be very safe, so long as it is treated with the due respect that any aircraft would need.

[Mishandled]

I sincerely hope that were not going to get another Airbus/Boeing tit for tat again. Maybe there should be a separate forum for these arguments. I dont profess to know much about their respective merits as aeroplanes other than the inhold systems, and other ground handling aspects, but it seems to me that there is a hard core of people who are either for Airbus or Boeing, and will never vary from that opinion. In this thread it would be interesting to hear from pilots who have experienced this situation. (IMHO of course)

[CaptainSquelch]

"and immediate go-around in case of sink rate GPWS warning below 200 ft."
Is that a new procedure? In my flyingclub a go-around is compulsary at any altitude. Is this an exeption?

Sq

[EGGW]

Anyone know which airline and where the first incident happened?? This is why Airbus have an AD out at present, with procedures for 320's to land in config 3 in gusty conditions!

[trend vector]

This incident actually took place in the US and not in Europe from what I am made to beleive and this glitch( if you will call it that) affects only A320's not 319 or 321's.Apparently as the TOGA was applied the aircraft was very close to VLS at which stall protection eases the nose down limiting Nose up authority.Airbus is looking into it but for the moment Flap 3 landing is reccomended if turbulence or wind shear is reported in the approach phase or later.

[Thrust]

At the end of the day it is still an aeroplane. Mother nature will win every time if she want's to.

So the AOA protection reduced the chance of a stall and contact was made with the runway. Everyone survived and had the go around been made as per the manual.... who knows. Engineers and system designers can only do their best and I'll take what Airbus offers as it's the best available to me. I'm better off with the protections than without.

[Magplug]

This was an Iberia A320 at BLV (Bilboa) the event occurred in early February. The aircraft remained at BLV for some weeks (may even still be there?) due to severe damage to the nose gear.

The crux of this matter is that the crew hit a massive updraft with wind shift below 200' and corrected with a comensurately large amount of forward control. Guess what comes next???

Having got a really good rate of descent going they should have expected the following downdraught. Due to the lack of altitude, full power a max AOA demand was insufficient to stop the aircraft executing a very hard 3-pointer.

The nose gear was written off and they evacuated on the runway.

Evidently Airbus Industrie have been asked to expand the max alpha envelope to accomodate pilots with slow reactions.

Perhaps if they had reacted to the warning signs in the first place & gone around this would not have happened.

Judging by some of the posts above I would say there is not much experience making comment here.

*** A superior pilot is one who uses his superior judgement to avoid situations which might require the use of his superior skill ***

If it balloons before the landing - you know what is coming next.............

[iflyboeing747]

Magplug

Well commented indeed..!
Personally I would never try to predict if things could have been another way - after they've happened, but I agree in your points that evaluating the situation and take early action is to be expected from pilots.

[DoctorA300]

Magplug,
Hindsight is a wonderful thing. If you know how to foresee such events, why don´t you enlighten your collauges
Brgds
Doc

[TEMP0+TSRAGR]

Just after that incident my company introduced a new procedure in gusty conditions with >10kts above the mean windspeed, or moderate/severve turbulence on short finals.

In these cases we MUST land with CONFIG 3 with minimum Vapp of Vls + 10Kt. If 'Sink Rate' below 200' immediate go-around.

This is a procedure to avoid the pitch down affect during the last phase of the approach due gusts causing Alpha protection to kick in close to the runway.

The problem is we are now restricted operating into shorter runways.

I fly the airbus, and ask myslef why design the a/c like this ? Why not have a FBW system which gives proportional movements of the control surfaces, like the 777 ?
Also normal moving throttles that you could 'nudge forward' in gusts would be a great help ....

I dont make the rules, just play the game !

[DownIn3Green]

Sum it all up in one word: Airbus.

[Flight Safety]

T & T, you've made what I feel are the most informative comments yet on this thread.

I agree with you, why does the aircraft have to be designed this way? Why should a wind gust near the runway be allowed to "trick" the computer into thinking that the AOA is higher than it actually is? I can't imagine as a pilot making a decision to go around at 200 ft or less, applying TOGA power and then trying to hold a pitch attitude suitable for climb out, only to have the airplane decide on its own that a pitch attitude into the runway is better (thus overriding my judgement), at full power no less!!! Man, my speech would be unrepeatable for an hour after an incident like that.

I'm glad that the condition was repeatable in the sim so it can be corrected. But this leads me to think that a gung-ho approach to computerizing every function on an airliner for the sake of claiming to the be most "technologically advanced", can come at a price. These types of systems are new and in some ways untested as this incident proves.

From my experience with computer systems, anytime you choose to automate a process which has enough complexity so that a human being is required to both monitor and exercise judgement over that process, then you'd better think through that automation very carefully. You're proposing no less than to automate human judgement. Automation is good at assisting human judgement in that it can help to prevent common human mistakes and it can react quickly to situations that don't require much analysis, but to override human judgement when many factors have to be considered and many possible choices are available, is sheer folly for the computer automater.

In this case the computer "judged" wrong, and overrode the judgement of the pilot in what could have lead to a tragic outcome. Thankfully in this case it didn't.

------------------
Safe flying to you...

[This message has been edited by Flight Safety (edited 30 May 2001).]

[EGGW]

If you have trouble maintaining speed with the Autothrust ON, just push the levers slightly out of the CLB gate, and you will get an increase of power towards the MCT setting. When you have your speed back under control, bring the levers back to the CLB gate.
There is a mentality that the A320 and its FBW bretheren will get you out of trouble, no matter what, you know its made for spear throwers etc.. But its still an aeroplane, and can bite back, it will stall if mother nature chucks its' worse at you. Ever been at 390, made it to the altitude just, perhaps a little early, then it gets turbulent. Like sitting on a knifes edge, no matter what the manuals say :)

[Big Buddha]

BLV, that'll be the VOR then, BIO is the airport.

[airforcenone]

The A320 series are designed to fly a 1g trajectory for pax comfort. In part this is done by the use of a 'soft' elevator which operates far more slowly than it should. (Notice next time you do your flight control checks how slowly the elevator moves relative to the stick movement).

This is why overspeeds in the descent are fairly easy to achieve (maximums of .78/320kt generally will prevent this), however I can't help feeling the 'soft' elevator was a contributary factor in Bilbao.

TEMPO is absolutely right when he suggests that a directly proportional response to stick movement would be better. Direct Law anyone?

Edited to give proper credit to TEMPO whose username I had screwed up!

[This message has been edited by airforcenone (edited 30 May 2001).]

[Heavens Gate]

To Flight Safety:

Entering Low Level Windshear of sufficient magnitude, can definitely give you an AOA way beyond Alpha Max as several windshear crashes have shown, no matter what your GoAround attitude and thrust.
Therefore it is quite possible that the AOA protection was actually saving the a/c from worse, just as it did in Habsheim.
However, having flown both the B777 and the A330/340 I have to say that my "OPTIMUM" a/c would be a B777 with the envelope protection of the A330/340.

[screwjack]

Folks:


step by step. I have reason to believe that AI did sent this article straight forward into the editors laptop. Read it carefully:


1.) the article says "landing incident". Well, I believe everyone here knows the proper definition and the slight little difference between an "incident" and an "accident". The article mentioned a "collapsed nose gear" and "engine nacells damaged". So it would be appropriate to term this thing ACCIDENT!


2.) as a matter of fact it was the Iberia accident in Bilbao. What is not mentioned here is the fact that it was a training flight for the F/O. Maybe nice to know...


3.) never trust ATC: apparently the WX was not as reported to the crew. This might excuse another little "glitch" in the making of this accident:


4.) what "son of a gun" would dare to use full flaps in x-wind and strong gusts? This might explain the French DGAC AD-Note in regards to this case and the +10kts and flaps 3. (BTW: this seems to be the stopgap for all kinds of software related problems with their FBW a/c. I recall that in full flaps your speed brake lever is nothing more than a useless handle. If you don't have (automatic) spoiler deflection after touchdown and you pull, nothing will happen. In flaps 3 you'll get partial flight spoilers - this had been some minor issue in the LH A320 landing accident in WAW some years back.)


5.) "inversion of wind direction" - nice terms! - Wouldn't it be more appropriate to say: "windshear" ? Well maybe but in this case isn't there something like a "windshear warning system" incorporated in the design??? Did it trigger??? What is the procedure? - Maybe add a little bit of power?


6.) TOGA power, "..but nevertheless the aircraft touched down". Well given the specific circumstances of this situation I might be a bit "off" but I still recall a chap named Cpt. Michel Asseline who fried the first A 320 delivered to AF back in 1988 (aka. the "Infamous Chain-Saw"). Different situation, nice weather and so, and obviously too low during a low pass (who is capable of reading French or Japanese should read his book "Le pilot est-il coupable", where you find ,among other pretty interesting stuff a very solid explanation for a wrong altitude indication in the cockpit - a thing that always bothered me that two grown up AF Captains couldn't read their altimeter - but I don't want to go into these details again). He (Asseline) always stated that nothing happened when he applied TOGA... One might conclude that a proper analysis of this sad event might have triggered a warning flag a bit earlier, specially taking adverse wx - conditions into account, - but again, just a thought!


7.) Apparently and sadly AI will never get it...


Just reflect for a second upon the following line from the article: "...the flight crew's actions on flight controls led the aircraft to hit the automated systems' high angle of attack protection and prevented a normal flare."


Excuse me? Here we go again?


The crew's action? Wouldn't a wording similar to "...the design of the alpha protection in this case prevented a normal flare" be a little bit more appropriate? - Was there anything the crew could do different than commanding nose up and hitting TOGA to recover? Did the a/c respond?

As we learned: no - it followed exactly its logic and as designed. Great! Do we learn that, can we read it in the FCOM or AOM? - What does AI teach their crews in their flight training and type-ratings in such an event? "P** in your pants and pray?"


Well "ping*", "careful" Mesdames et Messieurs in TLS! Some people might react extremely 'sensitive' to such statements. I believe you realized that quite 'painfully' in the past..


*(for non Airbus pilots: announcement sound of ECAM-message)

8.) Highest scores for Toulouse in regards to the announced modification of the program. This would have been out of proportions and unthinkable just a few years back. Remember, we are talking the prestigious alpha-protection of AI! Don't mess with that as I truly believe it has saved a couple of these planes, -including what was carried inside, in the past.

9.) Somehow "funny" are the closing remarks of Cpt. Michel Brandt in ref. to A 321 tail strikes: "...A321 landing tail strikes are not a noticeable concern and largely remain within tolerable limits." - Does anyone have any clues what this gentleman might want to say by this? - I recommend to ask some of the operators who had this "unnoticeable concern" in form of heavily damaged airplanes, being grounded and repaired for several weeks...


sj


[This message has been edited by screwjack (edited 30 May 2001).]

[Tankengine]

Of course in a Boeing up elevator means up elevator and thrust lever forward means full thrust! [some things are meant to be simple!]

[Icarus]

Updraft, downdraft, then tailwind.
Did anyone mention micro-burst?
I thought these things were easier for ATC/MET staff to spot (and hopefully report!)these days. Perhaps not in this case.

[Flight Safety]

Heaven's Gate, the following quote is from the article:

<font face="Verdana, Arial, Helvetica" size="2">Wind conditions were significantly more severe than initially reported to the flight crew, with up and downdrafts and gusts that also involved an inversion of wind direction. The digital flight data recorder and additional inputs helped investigators determine that the A320 encountered strong tailwinds, a 1.25g updraft, then a downdraft followed at 50 ft. by a tailwind gust.

DURING THE UPDRAFT, the flight crew applied a forward side stick input, then aft input to reduce the aircraft's increasing sink rate. As the Ground Proximity Warning System (GPWS) sounded, they moved engine throttles to takeoff/go around power, but the aircraft nevertheless touched down, according to Capt. Michel Brandt. He is Airbus' deputy director of flight operations support. He added that the A320's estimated vertical speed, when it impacted the runway, was 1,200 ft./min.

The recently completed investigation has shown that the combination of up and down wind gusts and the flight crew's actions on flight controls led the aircraft to hit the automated systems' high angle of attack protection and prevented a normal flare.

The incident was reproduced here in a full-flight simulator and led Airbus to a decision to modify the AOA protection's control laws to increase the flight crew's authority.</font>

Your comments suggest that a windshear encounter of sufficient magnitude could not be overcome by the pilots. If the magitude of THIS windshear encounter exceeded the performance parameters of the aircraft thus making it impossible for the pilots to recover, then you're correct. No software mod of any kind can overcome the laws of aerodynamics.

But at least a couple of things can help the pilot as he nears the ground in a windshear encounter. The wind becomes more horizontal as the aircraft nears the ground, thus causing more of an airspeed/power problem than an AOA problem (assuming the aircraft has already flown past the center of the microburst). There's also the ground effect of the runway for extra lift if it's needed, while airspeed is being recovered for a go-around.

But if the windshear conditions are of insufficient force so as to allow the aircraft's attitude to be recovered, then the pilot MUST have precise control of the elevator (and throttles) to get out of the condition safely.

I'm convinced that this aircraft's attitude was recoverable and that the computer flew this aircraft into the ground, otherwise the software mod being proposed would be pointless.

------------------
Safe flying to you...

[CaptSensible]

airforcenone, are you sure about what you wrote?

<font face="Verdana, Arial, Helvetica" size="2">this is done by the use of a 'soft' elevator which operates far more slowly than it should. (Notice next time you do your flight control checks how slowly the elevator moves relative to the stick movement).</font>

I understood that on the ground the a/c is in 'Ground Mode' and the stick to flight control relationship is a direct one (like in direct law in flight). Since the a/c normally operates in 'Normal Law' when airborne the 'G' demand is metered not by a 'slow elevator' but rather by the 1G computed by the ELAC?

[gaunty]

Flight Safety
Wel put, in this case it sounds like the tail is wagging the dog.

[Heavens Gate]

To Flight Saftey:

My initial reply was solely of technical nature. You wrote about the a/c being tricked into believing the AOA was too high, and about selecting TOGA and a suitable GoAround attitude below 200 ft will get you climbing in anything but an A320.
Remembering the doomed L1011 at Dallas (as well as many others) selecting TOGA and the proper attitude WILL NOT get you safely away from the ground if the energy and height required is less than the energy and height available. In case the a/c was rapidly approaching the stall AOA, adding further UP-elevator would only serve to increase the drag and trigger the stick-shaker in a non-Airbus fly-by-wire a/c (the pusher being disabled at such a low altitude). Therefore your choices would be limited to hitting the ground as controlled as possible on the shaker or stalling, going down uncontrolled, which the AOA-protection tries to avoid.
Please consider this reply again as technical, not as a pro-Airbus statement. But I have been part of some accident investigations in the past, and I can safely say that AOA-protection would have prevented some of those unfortunate accidents, as instant energy just isn,t available close to the stall - no matter how you got there.

Best regards ...

[Heavens Gate]

Sorry I made a mistake. Of course it must read: ...if the energy and height required is more than the energy and height available.

Once again, sorry about that ... Best regards

[airforcenone]

CaptSensible,

I must admit I may have got a little confused, however you have to admit that close to the ground, when you pull back fairly firmly, you want the bl**dy thing to go up! As you say, in flight the aeroplane is in Normal Law (ie. 1g trajectory). When it is on the ground, Direct Law applies (I think). During take-off, Direct Law 'blends' into Normal Law, however on landing it's one or the other. As far as I'm aware, this incident/accident occured before the aeroplane touched the ground. The other alternative is that it was in the flare, in which case, the aeroplane was trimming forwards to give the pilots something to pull against.

Someone feel free to put me right 'cos I do have a habit of digging big holes for myself!

[Flight Safety]

Heavens Gate, I generally agree with you. If the energy and height required are greater than the energy and height available, then there's nothing you can do except to try and achieve a minimum rate of descent and a flat attitude on impact. Stalling the aircraft in an attempt to recover from windshear is also not helpful, and AOA protection would theoretically be useful in preventing this. But I emphasize the word theoretically.

I also agree that this really has nothing to do with Airbus or any other manufacturer. This is really about an aircraft designed with a particularly unique feature called "Alpha Protection" that has "Alpha Floor" and "Alpha Max" modes.

Apparently during the simulator portion of this accident investigation, it must have been determined that the AOA was not calculated properly due to the sequence of updrafts, downdrafts, and changing airspeeds from gusts and "wind direction inversions" just prior to the flare. If the AOA was not calculated properly, then the "Alpha Protection" is of no help to the pilot, and in fact may hinder his ablility to recover the aircraft if sufficient height and energy ARE available for recovery. I think that's precisely what occurred here, and that's why the investigation has recommended modifying the software to give the pilots more direct control in the flare.

But this software mod poses some interesting questions. On the one hand I see this mod as perhaps partially negating the benefits of AOA protection. On the other hand, if the rapidly changing wind conditions that existed in this accident prevent the possibility of accurately and reliably calculating the AOA, then a switch to Direct Law would be the preferred solution. What I'm not clear on is whether this software mod will cause a reversion to Direct Law in all cases just prior to the flare, or only in cases where rapid changes in wind direction cross a threshold of AOA calculation "unpredictability", thus forcing a reversion to Direct Law in only those instances.

------------------
Safe flying to you...

[This message has been edited by Flight Safety (edited 01 June 2001).]

[Heavens Gate]

To Flight Safety:

It is good to see that at least some professionals are left on pprune who are able to discuss a topic in a respectful and openminded way - my respect to you.

Best regards ...

[411A]

AirBus seem to make changes to the software every time there is an incident/accident. Surely the question must be.....WHY was it not designed properly in the first place? Altho the A320 was the first FBW airliner and a certain amount of "adjustment" was needed from time to time, surely now that it has been around for a long time and is a mature design, was it perhaps designed initially around a flawed principle? The B777 does not seem to have these same type of "problems".

[Flight Safety]

411A, the Boeing FBW system of "envelope protection" uses pitch control to maintain airspeed, rather than using pitch control to maintain an AOA value. It's a fundamentally different approach, although I must admit I understand the Airbus system better than I understand the Boeing system.

Because the basic approach to "envelope protection" is fundamentally different between the designs, the possibilities and permutations MUST be different when flight occurres near the "edge" of the envelope. These are the areas of flight where the weaknesses of either design will be exposed.

Now I want to go learn more about the Boeing system...

[Diesel8]

FS,

Perhaps the fix will be similar to the one used in abnormal attitude law (?).

[Ignition Override]

411A raised a very good question, and I know nothing about fly-by-wire. AS for angle-of-attack info, aren't there conflicts between any system which tries to protect us from terrain (GPWS-old, or new EGPWS) and at the same time protect us from windshear, since there must be a priority?

It seems a little strange to me that the US FAA (CAA etc?) never required a true angle of attack indicator system (with precise limits) for US transport aircraft, however the FBW Airbus or Boeing flight control computers appear to know the desired AOAs at all times. AOA would be much better than using airspeed and pitch, but I doubt that the optimum or max lift AOA is displayed on any modern ADI or PFD, knowing that the FAA has no desire to develop a program for this (too much $?). The US AIR DC-9 windshear recovery procedures at Charlotte (CLT) were seriously hindered by input during changing flap positions, and by weather/wind info not being quickly shared between controllers on different frequencies at the same airport facilities.

Is it likely that several crashes might have been avoided if a user-friendly AOA system (with training on it) had been in use for decades on civil and military transports, as on military tactical and trainer jets?

[screwjack]

Ignition Override:

An AoA indication is available at AI as an extra option, for an extra price. Some former Air Inter A 320 have this feature installed. I beleive the a/c are now with AF.
Rgs

screwjack

[Burger Thing]

Hi 411A, you wrote:
<font face="Verdana, Arial, Helvetica" size="2">AirBus seem to make changes to the software every time there is an incident/accident. Surely the question must be.....WHY was it not designed properly in the first place? </font>

The Airbus is an highly computerized airplane. Airbus made this approach in the believe and goodwill to increase saftey: reducing pilots workloads, providing crew, passengers and aircraft with all kind of safety systems, some of them even overrides wrong pilots inputs.

But this philosophy is not free of risks. Like any other computer system, Soft- and Hardware designers are given in the beginning of their work a specification envelope. Based on this specifications, they create, design, build Hardware and write Software. The varification process comes afterwards, to see and check, if all the systems work properly under all circumstances WITHIN the given speficication envelope. The flight test is also part of this varification process.

The ideal case is, that on every given input (within the specifications) the computer produces a correct output. In an aircraft computer system this means, that the Hard- Software senses for example dangerous situations (input) and takes corrective action (output). Ideally these systems works great and increase saftey dramatically. But only within the given specification envelope!

And here lies the danger of Airbus philosphy and in fact of every automated system: Something occurs outside the specification envelope which has not been foreseen by the engineers, computer designers, etc. This can be in case of an aircraft weather phenomena, technical defects, runway conditions, or a combination of everything, etc.

The worst case scenario is, that the pilot can't react to this situation, because the computer doesn't allow him/her to do so, because the computer does not see this specific input, thread, or situation.

Because of this reason, we see after almost every Airbus incident/accident a change in Soft- and Hardware. Guys, don't get me wrong. I don't want to contribute in an emotional Airbus vs. Boeing clash. But I just hope, the engineers have prepared and designed the systems on an Airbus in a way, that in a couple of years, when the A320 is flown somewhere as a cheap old model (maybe to replace an old 737-200 :) ) in a third world operator (maybe in poor technical conditions), it brings the people on board safely from A to B.

[Heavens Gate]

One of those a/c is on short term lease to us from Air France. However, as this AOA indicator does not have any limit markings on it, it is of limited use only.

To 411A: the fly-by-wire system in the 777 is of a much simpler design, so may be that is the reason it doesn,t have as many teething problems. As I have stated before, on a day to day basis I prefer to fly the 777, but when reaching any limit I still prefer the Airbus way of keeping me out of trouble.

[ex-expat]

Guys,
Seems to me the Airbus FBW system is that the pilots make an imput on the controller and that is their vote. Then the three computers vote. Then the airplane does something...maybe.

The B-777, the pilots have veto power and the control surfaces will move if you insist. A very different design philosophy if you will.

At Airbus, pilots are a necessary political problem to overcome as they are always out their crashing their perfectly designed and thoughtout airplanes. See the movie German TV documentry "Fatal Logic" and you'll understand what the powerful EU engineers at Airbus think of your skills and judgment as a pilot.

[electricjetjock]

We are all speculating here ( and I am about to add my twopenny worth) but yet again it has developed into A Vs B.


1. Why was GA action not taken immediately!

2. If idle had been commanded as part of the flight path correcting actions, then you can select TOGA but you are not going to get it in 1 to 2 seconds! The time available before ground impact is not there.

3. If the aircraft did not have AOA / Stall protection. Then all you guys saying that you want the controls to do what you ask, would have had the nose come up (making you feel good), stalled the aircraft, increased the ROD and impacted the runway tail first and we can all guess the outcome of that!

What a lot of you seem to forget is that the americans did it first with the F16. Also there was a lot of design input to the 777 by a few dino's in the US majors. Otherwise why would you have that great control wheel to turn a few electrical transducers!! not forgetting the other control wheel.

------------------
Keep smiling!!!!

[Tarmach]

I have zero hours on any Airbus, i'll be the first to admit it! But what are thay trying to pull over pilots. For instance I can't believe anyone really likes that sidestick, it seems more of a gimmick to enable airbus to sell more aeroplanes than a real aid to the pilot- so what the pilot has more leg room- whoophy!! Further, with any normal yoke when the A/P is connected the pilot can tell exactly what the aeroplane is doing just by placing their hands on the control column, however, with that stupid sidestick you can't tell jack s*** whats happening. In addition to this the throttles don't move either, when the A/T is engaged. Give me a Boeing any day, airbus has LOST THE PLOT!! Apologies for going slightly off-topic!

[northern boy]

Tarmach,

You state that you have "zero hours on the airbus". Just about anyone who has likes it and the sidestick is a total non issue, as you would appreciate if you had flown it. If you want to know what the aircraft is doing try looking at the instruments or even outside!.I've never flown the 777 so I shall refrain from comment on what I am sure is a nice aircraft.
Please lets not have another Boeing/Airbus slanging match.If they wern't safe they never would have been certified.

[Ignition Override]

Northern Boy-I'm not referring to any Airbus here, but let's not forget how many planes with questionable characteristics were "certified" by the US FAA (and allowed to operate with no changes until tragedies took place, while intentionally disregarding serious concerns from overseas operators , i.e. the ATR-42 in icing conditions).

This was in order to "promote aviation", which was the FAA's basic mandate, until the Valuejet (now Airtran) crash.

Have people forgotten the FAA's overriding philosophy in making safety decisions? It is still the "cost vs benefit" analysis. This is understandable, at least to some extent.

[This message has been edited by Ignition Override (edited 01 June 2001).]

[Tarmach]

Northern boy, ok you make some interesting comments. I too don't want to venture into an Airbus/Boeing type of debate. However, I do believe I have a point with the sidestick which is just another facet of the Airbus philosophy. Ok a pilot's job is to process information which appears in visual, audio and say 'feel' or 'seat of the pants' channels. What I'm saying is Airbus seems to present everything to a pilot through his much acclaimed visual channel which could become overloaded in times of high workload. Therefore the main crux of the argument is that a pilot could without the need to visually process the information tell you or I exactly what the aeroplane is doing by simply placing his hand on the control column and not overloading his visual channel which can be used for other things. However with Airbus this does not apply. Ignition Override is correct with the safety issues, many decisions are political.

[Frederic]

Electricjetjock, you are hitting the nail on the head!
The aircraft in this incident needed the maximum manoeverability and so the maximum amount of G it could get.
In ANY flight condition the maximum amount of G is obtained through applying Alpha max.
The AI FBW is designed to give you alphamax or the G limit when full aft stick is applied. In thid case the aircraft was below it's corner velocity and so the G limit could not be reached, so the FBW gave A-max.
In this case there simply wasn't enough lift available to make the aircraft touch any softer.
So if you would be flying a conventional aircraft in this incident, the pilot would indeed have more authority. More authority to get the aircraft into a higher alpha situation leading to an even higher sinkrate and a misleading higher nose position. It is important to understand that when you are at max alpha, that's it, you got all the lift you can get. Pulling the nose up further will only make the sitiuation worse (you are over the top of the alpha/CL curve).
Although I love AI aircraft I always try to keep an open and logical mind about a sitiuation like this. I don't always defend airbus, but this time, a big thumbs up for AI. People who think the airbus doesn't let the pilot fly the aircraft anymore have a very narrowminded view and a low understanding of FBW systems. What about ALL of the current generation fighters? They limit the alpha and G, and, yes, in a way the pilot "authority", but for a darn good reason. Don't forget that every aircraft has its aerodynamic limits. If this would have been a B757 (don't get me wrong, it's a great aircraft!) it wouldn't have stood a better chance, probably a worst. If you think Boeing is better in that respect, lets start a string about the Brittania Gerona and Transavia Amsterdam incidents! This is not a Boeing vs. Airbus issue... This is a winshear and airmanship issue.

[whats_it_doing_now?]

I'm not getting involved in any slanging match here, but if your last thoughts as the aircraft ploughed into the runway were 'I know I'm doing the right thing, but that smart peace of silicon wont let me!' Wouldn't you be a bit annoyed? I don't fly airbus, but it seems the laws it flies by have cought one or two people out over the years. Could it be that they aren't quite as natural as the traditional ones virtually every other aircraft uses? I know technology has to move along, and many of the systems on the airbus may be a step in the right direction, but it doesn't seem a good idea that the aircraft can override the pilots commands at such a critical phase of flight. It may take a second for the pilot to realise nothing is going to happen, and as in this case, that second may be too much.

[Diesel8]

Frederic,
Great response.

As usual this in turning into the usual Airbus slagfest, particularily when it comes to the FBW system. I simply do not have the time nor inclination to explain all the intricacies and protections in this system to non Airbus pilots. Besides, I am a lousy instructor, not to mention my extremely poor typing skills.

Everytime a FBW Airbus has an incident, everyone rushes to judgement about the viability and useability of the FBW, "it must have been the silly computers", so on, so forth. I need not remind you, as some one earlier did, Mother Nature is very powerful and sometime she wins. Just perhaps the outcome would have been exactly the same in the much flaunted Boeing 777. I do not fly one, so I can only speculate.

I have spent a fair amount of time on the FBW Airbus and absolutely love it. I have yet to see any real problems and find the aircraft a delightful place to work. From experience it seems that those who fly it or have flown it, really like it and most of its detractors have never set foot in one.

D8

[aviator]

Frederic,

It seems to me, that if the Airbus engineering did in fact save the day, why is Airbus revising the software??????

Please help me understand.......

"Revised software, to be implemented soon, will increase pilots' authority over automated systems."

"In the wake of a serious landing incident, Airbus plans to revise the A319/A320 twinjets' automated angle-of-attack (AOA) protection."

[Frederic]

Dear Aviator,
There is currently not enough information available to me to answer that question. I have not read the accident report and I am not and do not claim to be an aircraft design or test engineer or testpilot. So I simply don't know. HOWEVER, it would seem very unlikely to me that AI would increase the alpha available much above alpha max since that won't increase the lift available. What they might tweak a little is the reaction TIME. Someone made a very good point about the elevator being a bit slow in responce. It is however not possible to make a FBW system with zero responce time since the processors although extremely quick still need some time to "think". There also needs to be some lag and/or limit overshoot built into the system since if you make a totally "stiff envelope protection system this could result in violent oscillations since the system will not allow any overshoots and will thus move the controlls into the "below limit" position to quick. I think it is a good thing that AI are prepared to change and devellop their FBW system. Compare it to your flying skills. The worse pilots there are are those who think they have nothing to learn because they've passed a certain number of hours. Skills are something you devellop during your whole lifetime. There is nothing like a "born pilot". In much the same way, systems need to be develloped.
Open your mind...

PS: Whats it doing now, have you at all read my responce?? Even if the pilots would have totally overridden the computers, they could have only made the situation worse. Alpha max is an AERODYNAMIC limit that provides you with the maximum lift coefficient available. Pulling the stick further aft increases the angle of attack and decreases the Cl wich would result in the sink rate increasing!

[This message has been edited by Frederic (edited 02 June 2001).]

[ex-expat]

Excuse me gentelmen,
But didn't the airplane in question land not only in a high sink rate but also on the nose gear? Wasn't that perhaps the major reason we went from a just hard landing to a very damaged airplane? My Boeing would have at least hit on the mains as I have control of the attitude, not just a vote in it.

Without a doubt the Airbuse has a better cockpit to eat and converse in, but the software in the glass, and the FBW design philosophy is something a pilot must learn to adjust to, trick and fly around.

[Flight Safety]

Gentleman, a quote from the article:

<font face="Verdana, Arial, Helvetica" size="2">The recently completed investigation has shown that the combination of up and down wind gusts and the flight crew's actions on flight controls led the aircraft to hit the automated systems' high angle of attack protection and prevented a normal flare.</font>

The pilot couldn't even flare the airplane prior to touchdown. The "Alpha Max" function was activated prematurely because the AOA was calculated improperly in the unique sequence of events. This is why the software mod is required.

One of the main purposes of the flare is to arrest the vertical descent speed just prior to touchdown is it not? Or am I the only one who sees anything wrong with this?


------------------
Safe flying to you...

[This message has been edited by Flight Safety (edited 02 June 2001).]

[Joey Gray]

Hi Fella's

I fully agree with Thrust " Any plane will do the same regardless of protections- If Mother Nature's not on your side that day you're in for a rough time" As far as Tempo-TSRA are concerned, you guys need to understand the plane a little better, If you nudge the thrust levers anytime out of the Clb Gate you will get more thrust- you can apply this whenever yourspeeds bleeding on short finals so try it next time dont forget to get the levers back to the climb gate quickly or else you will hit TOGA and the Capt will be p*##@^ off.

[Critical Mach#]

From a very much edited report coming from the operator of the 320 damaged in BIO.

The A320 softaware prevented the crew from obtaining Max AOA when GA was called.
During the approach and below 150feet a very potent downdraft hit the aircraft. The F/O was PF at the time and pulled back on stick to arrest the rate of descent. At the same time the capt called for GA while pulling on sidestick without pressing priority button. The computers sensed that the sumation of both inputs would have placed de Aircraft beyond MAX AOA (Flaps 3) and responded with a zero increase of AOA. AOA at the time was 3degrees. Aircraft impacted on rwy at 3 degrees AOA main gear first with 4.8g´s and bounced. During the second impact nose gear collapsed.

´Regards



[This message has been edited by Critical Mach# (edited 02 June 2001).]

[Flight Safety]

Gee, it's worse than I thought.

I thought the AOA was being misculated because of the conflicting wind inputs and pilot responses, but now I see the computer made a more fundamental logic error. If sumation of the pilot inputs would have pitched the airplane above AOA Max, then why not just sum the inputs to the value of Alpha Max? I suppose that it might not have occurred to the software engineers that in an emergency, both pilots might pull back on their respective joysticks at the same time. Pitching up to Alpha Max is still safe, while not pitching up at all could be deadly.

Gee whiz...

[411A]

AirBus technology seems not to work very well in critical situations. The B777 FBW system does seem to keep the pilots in the loop to a much greater degree.
Have noticed that the A330/340 have not had as many problems. Would this be because these types fly longer sectors and make fewer approaches/landings?

[TvB]

From my webpage at www.aviationsafetyonline.com (http://www.aviationsafetyonline.com)
with kind regards
TvB

ACCIDENT OF AN IBERIA AIRBUS A 320 IN BILBAO
Airbus Industrie initiates a move to increase pilots authority over automated system

by Tim van Beveren, Miami


The landing accident of an Iberia Airbus A 320 on March 7 in Bilbao, Spain, shows vital consequences for Airbus Industrie. The European aircraft manufacturer recently surprised the aviation community by announcing that it is going to revise the software programming of its automated Angle-of-Attack (AoA) protection, also known as “alpha-protection”. This highly sophisticated safe-guard system has been installed on all of Airbus’ fly-by-wire aircraft, dating back to the first delivery of an A320 in 1988. The alpha protection has always been regarded as one of the prestigious, outstanding and truly safety-enhancing features of the modern Airbus products. The computer guided system prevents the aircraft of entering a stall, resulting from a too high angle of attack. If, for example, the pilot would inadvertently command too much nose up attitude in a climb, which would lead to a subsequent loss of lift, the system will automatically lower the nose by acting on the elevators and thereby prevent the aircraft from entering into a stall. The Airbus A 320 Flight Crew Operation Manual (FCOM) defines it as a system “which provides protection against stall and windshear, (and) has priority over all other protections.” (Emphasis added)

However, according to first released findings of the Bilbao accident investigation, the ‘activity’ of this safety feature was a contributing factor in the event: the alpha-protection contradicted the desired pilots action. During the final approach to runway 30, the Ground Proximity Warning System “sink rate” warning was triggered and the crew applied TOGA-power (Take-Off/Go-Around power) to abort the landing.

Yet, special attention should be given to the specifics of the scenario: At around 23:10 local time Iberia flight 1456 was approaching Bilbao’s Sondica airport. The flight originated in Barcelona. On board were 136 passengers and a crew of seven. As the flight was a training flight for the First Officer, there were three pilots in the cockpit. At the time of their ILS approach the crew encountered a thunderstorm and was advised of light turbulence and surface wind speeds from 240 degrees of only 8 to 9kts, but no windshear. The airport is dreaded among pilots for critical conditions, - especially in the winter, and is not equipped with improved weather measuring equipment or modern windshear detectors. The airport was the scene of two other weather related accidents that occurred during the preceding 15 days and other three in the previous five month.

Bilbao’s Air Traffic Control did not mention to the Iberia crew that, just shortly before the A320 approach three other aircraft had tried unsuccessfully to land at Sondica and had finally decided to divert. According to statements of airport personnel to local media after the event other flights also diverted directly to their alternate, without even trying to land in Bilbao.

During the final approach the A320 encountered heavy turbulence at about 200 ft AGL, with gusts up to 65mph, an 1.25g- updraft, followed by a downdraft and tailwind gusts at an altitude of 70-50ft. The associated change of wind direction during the event clearly points to a windshear encounter.

According to information released by Airbus’s deputy director of flight operations support, Cpt. Michel Brandt, the flight crew applied a forward sidestick input during the updraft, then an aft input to reduce the increasing sink rate. When the GPWS alerted the crew about their unusual increased sink rate, the pilots decided to perform a go-around and applied TOGA-power. But the crew’s desired and commanded action was not performed by the aircraft. As the alpha-protection was triggered during this event, the system commanded a nose down signal, which was performed, even though both pilots had their sticks full backward, commanding a “climb”. Nevertheless the airplane touched down with all three gears struts almost simultaneously and with an estimated vertical speed of 1,400ft./min. The nose gear subsequently collapsed and the plane slid along the runway for about 3,280 ft. before coming to a stop. During the emergency evacuation, four passengers and some of the crew received minor injuries, among those, one passenger, a 75 year old female, was hospitalized.

The barely six month old aircraft received substantial damage, including the wing structure and the engine nacelles. It is beyond economical repair and therefore should be regarded as a total loss. The accident has been under investigation by the Spanish CIAI (Comisión de Investigación de Accidentes e Incidentes). For Spain’s national carrier Iberia this accident represents the first loss of an Airbus A 320. The company operates 85 modern Airbus fly-by-wire aircraft (A319, 320, 321 and 340) and last year transported over 30 million passengers.. The Spanish company CASA is part of the European Airbus consortium.

Back in early April, the French Civil Aviation Authorities (DGAC) had issued an airworthiness directive (AD) for the A319/320 aircraft. It ordered the crews to fly at least 10 kts. faster and use only “CONFIG 3” (flaps 3) setting on approach in conditions with gusts greater than 10kts reported wind increment (max. wind minus average wind), or when moderate or severe turbulence on short finals has to be expected. In such events, the crew must select no more than flaps 3 and maintain a minimum approach speed of Vls (= “lowest selectable speed” ;) + 10kts. If the GPWS “sink rate” warning occurs below 200ft, an immediate go-around is required. Operators incorporated this AD-note into special bulletins for their pilots, but no additional information about the nature of this special procedure was given so far.

In the light of the accident occurring only four months ago, and the sometimes lengthy ‘normal’ timeframe for implementation of safety revisions after an accident, it appears to be of “amazing speed” how Airbus Industrie, - even in the absence of a final report, has already decided and performed a modification on the alpha-protection control laws. This was done in an approach “to increase the flight crew’s authority”, - as Cpt. Brandt was quoted by media. - A step applauded even by staunch Airbus critics among the international pilot community. A revised software version is expected to be validated this month and has already received certification by the French Civil Aviation Authority (DGAC) and the European Joint Aviation Authority (JAA). Airbus plans to implement a “rapid retrofit program” for its entire A319/320 fleet.

[Frederic]

Seems like the A320 didn't reach alpha max at all. If both pilots commanded a-max this might have led to the FCC's overanticipating the alpha demanded. If this would have been the case the problem would not have been a limit protection problem, but an input problem. On one hand it's a shame this happened, but on the other hand I think this incident means a great step forward in FBW devellopement. IF...
Looking forward to reading the report. It would still surprise me if AI would allow the FBW to exceed a-max. To allow it to make a transient overshoot would make sense to me, but just to increase its value wouldn't. But this incident smells of an input problem. So in anticipation of more detailed info I will now shut up and let the AI-bashers vent their anger. (beware though, I will bite back) Would still fly the A320 anyday...
PS: Flightsafety: Normally if both pilots apply full aft stick the FCC command maximum G (2.5) or max alpha, wichever comes first. So it must have been an input or reaction time problem . Another thing I don't understand is that since below 100 feet the aircraft passed from normal to direct law, the envelope protections should have been removed by that time. Strange...

[This message has been edited by Frederic (edited 03 June 2001).]

[Flap 5]

There are a number of replies here which start with 'I don't want to get into a slanging match but ..' and 'I have never flown Airbus but I don't think its much good'. So what follows in these posts is hardly worth reading. I have got over 3500 hours on the Airbus FBW aircraft and over 2400 hours on the B737. The Airbus has its faults, which are often brought out when an unusual incident happens, but they are all excellent aircraft.

It would appear in this instance that the requested input from both pilots was so extreme that the system would not allow it and retained the existing AOA. I would think that Airbus will now change the software to allow this to be accepted by the computer. After all a request of full back sidestick on both sidesticks should be responded to more rapidly than normal by the system, not thrown out as unacceptable. It's not perfect, but it is still very good.

[TowerDog]

Heavens Gate:

You mentioned the Delta L-1011 windshear accident in Dallas as "TOGA power and proper attitude" did not prevent the accident.

Wrong. It was indeed preventable if proper attitude had been flown.

As this happened in 1985. most airlines did not have the Windshear Escape Maneuver simulator profiles we have today.

The Delta crew did a "normal" go around and never pitched up enough to prevent the sink rate encountered.

Nowadays we are taught in the simulators to pitch up enough to actiavate the stall warning, then stay there.

Never flown an Airbus of any kind, how is the
windshear/microburst escape maneuvers taught in the sims?
Full aft input of both side sticks cancel out
the message to the computer???
Must be a typo or misunderstanding, nobody can get that certified...?

------------------
Men, this is no drill...

[Anti-ice]

I've read pieces of this thread , and again a question mark seems to hang ominously over the capabilities / authority of the airbus FBW systems.

I'm not either pro/anti airbus,but do feel more than a shade of concern over the integrity of it's onboard equipment.

The close call on the LH A320 sounds just a little too close to be comfortable - well done guys - , but to have your overall command of an aircraft over-ridden by a computer in such a critical phase of flight seems almost unthinkable.

The series 'black box' is being shown on Sky Wings again at the moment ,with last Fridays programme focusing on Human error -v- Automation.

A clip I've never seen before featured a (Tarom?) A320 seemingly out of control over CDG - the aircraft rocked and yawed over the video cam filming it with engines howling, nose high & gear down at an altitude of i guess 2-3,000 feet .I couldn't believe what i was seeing at first, I dread to think of the reactions onboard.

Inevitably there will be the usual boeing versus reactions to this , and doubtless there are hundreds of airbuses around the world doing a 1st class job, but are airbus open to reviewing and changing systems to ensure the highest level of confidence in them?

[max_cont]

I wouldn't normaly post on this subject because I don't fly Airbus, only Boeing.

I will admit to disliking the idea that I cannot override a computer, especially when it's my ass that's strapped to the seat and not the system designers.

The A/C was designed by people. People are not infallible, they can't think of everything.

The FBW is a great idea, IF you give the pilots a last "out", in that "not considered" scenario.

As someone has already stated, "mother nature" will sometimes come up with the unexpected. Any system as hugely important as the flight control system had better have an answer, even if it's just giving back full control to the pilots.

I know I will probably be slated for this post. Some Airbus pilots seem to respond in an almost rabid manner, to any criticism aimed at the A/C. (we only operate them guys)

I have only been flying Boeing airplanes for 13 years. I accept that there are faults with the design, some found and no doubt some still to be discovered.

Why is it that some pilots will not even consider, that Airbus could possibly have got some of it wrong?

I write this knowing that in a couple of years I will be OPERATING the A330, since Boeing haven't designed a new airplane to compete with AI.

[M14P]

Once again the sort of tabloid rubbish that ppruners seem so fond of especially 411A (Incidentally the 411A was just about the most dreadful aircraft ever made by Cessna, I digress)

B737 can roll over and die - nobody talks about it much. 747s can explode without reason like the occasional 737 and nobody talks about it.

People talk about FBW and Airbus like it is some evil plague sweeping the community - What are people trying to say here? Because the Airbus is FBW the aircraft has landing accidents? I've seen plenty of other airliners have accidents on landing. Airbus are tackling a potential problem with one 'standard' of ELAC not every ELAC since it has shown that in this instance it could have performed better. Without full knowledge of every single facet of the accident and the data surrounding it none of you pundits can make an informed, professional decision as to the cause of it.

Just because you have a big control wheel in front of you does not mean that you are really 'in control'. 747 - hydraullics and q-feel; hardly wind beneath your wings type stuff is it. Stick pushers, mach trimmers and yaw dampers all mean that the control surface is not necessarlily where the pilot is holding the wheel and they've all been making our lives safer and more comfortable since the 50s.

Grow up children

[max_cont]

Right on cue M14P, demonstrates my point nicely



[This message has been edited by max_cont (edited 03 June 2001).]

[411A]

A320----die by wire, AirBus style. The pilots have limited input, the machine decides what's best, never mind experienced crew. Truly, the tail wagging the dog, French technology at its "best"?

M14P: Well now you do indeed seem very informed about the CE411A, have you EVER operated one? What are your facts? Do you have any? Or only hot air, with AirBus bias.

The A320 seems to be developing a very dubious distinction, many incidents/accidents, and now pilots must be wondering....what the hell is it doing now?

Our company has now decided that the A320/330/340 is to be avoided at all costs for executive/crew travel. Not to be trusted, ever. I wonder if other company travel departments have done the same? I personally know of six. More to follow, I suspect.

[Flap 5]

Anti-Ice

It has been mentioned before in another thread - that aircraft was an A310, a completely different machine and certainly not FBW.

And yet again there are posts from people (pilots?) who have never flown a FBW Airbus. By all means ask questions, but do not make arrogant statements when you don't know what you are talking about!

Edited for typos and yes I feel better now.

[This message has been edited by Flap 5 (edited 03 June 2001).]

[screwjack]

M14P:

I got the impression that you got a bit lost here...

I think nobody is "hitting" on Airbus FBW a/c just because they simply don't like it. But if you carefully follow the history of AI since the introduction of their "new wonder bird" almost 14 years back (prototypes flying around and doing incredible things just to get more customers signing the order book, at the same time promising vast cuts in training budgets (cross crew qualification and so on...) and support costs - because "it is all so and so fail-safe and nobody can do wrong") it is my opinion that AI in general has demonstrated some sort of a serious "attitude" problem, when we are talking "safety".

This is what bothers many people, coming from "conventional" a/c and maybe being a bit too much pampered with manufacturer support, when it came down to problems.

Yes you're right, the B 737 has a Rudder PCU problem and same applies to their center tank/pack design (almost the entire product line). But I'm pretty sure that the guys in Seattle (not their legal department though) are as much concerned about it and trying to improve. Something of that nature was hard to be felt or seen from the folks at TLS - so far...

So I'm very much surprised and even delighted that they obviously have marked a change there recently. Well, keep on the good work, this is the more appropriate track anyways...

Screwjack

[bunyip]

It's not the FBW system that is causing grief, it is the Computer override. A Boeing pilot knows that he can always take over and fly the airplane. A Bus driver cannot;ever.
In the circumstances described with the low level wind shear, I thought that the airplane would recover to the programmed descent profile by itself? For example if a wing drops the pilot need not react since the wing will come back by itself under computer control? Similarly the pitch/rate of descent? If not, what is the point of the design?
And another question please: What are the wind limits for landing and takeoff; crosswind and total wind. Are they different for an auto land (ILS)?

[atomic]

I think some people here should take a quick course in C* Laws and Electrical Flight Control Systems and grasp a few basics about FBW and then learn a bit about the FBW implementation at Airbus.....then come back and tell us something useful.

[Ignition Override]

OK, it's late and I just skimmed over the last two pages of this topic, having read the previous pages, and again, have never received any training on any Airbus type.

Aside from the interesting aspects of fly-by-wire, when a plane encounters an unexpected/variable sink rate on final approach, can the A-320 throttles be pushed forward enough to reduce the sink rate (i.e. 1500 fpm) without activating the TOGA (go-around) mode? Can't you click a button, and just push them up a good bit like on 727s and DC-9s?

Let's say that you suddenly encounter a loss of 10-15 knots on short final while the quartering headwind is 20 gusting to over 30 knots-can you quickly increase the power and still be in whatever is the normal landing throttle mode?

I have no idea when most A-320 (etc) pilots disconnect autothrottles-on the 757 it was our option, but most waited until no more than a few miles out or maybe 2,000 AGL etc for CAT 1 and visual approaches (I preferred flying ILS approaches in the VOR mode on the HSI in order to watch the LOC bar "come alive", planning to go back to the old technology).

Not picking on Airbus here, just curious.

[ShotOne]

Some good information on this thread -and some total garbage...411A! So which company has stopped its crew flying as pax on Airbus then? The Glasgow Bus Co.?

You have contributed nothing to this thread. I doubt you are even a pilot. Please stop wasting everyones time.

[Flap 5]

Ignition Override

For your info it is quite possible to disconnect the auto thrust on the A320 and fly the aircraft like a 737. In fact on the 737 it is highly advisable to disconnect the auto thrust on the approach to avoid porpoising. The A320 has a much better system with the 1g profile of the Normal Law not allowing porpoising and hence it is recommended to leave the auto thrust on.

However if the auto thrust is on and you want a lot more thrust, because of a rapid sink, you just push the levers forward out of the climb gate and the thrust will go up to the thrust for the thrust lever angle. But, by all means, if you are not happy with flying the approach with the A/T take it out. I have flown with many Boeing trained pilots who have preferred doing that when they first get on to the Airbus.

But don't knock it until you know about it.

[bonajet]

411A
Quote:
M14P: Well now you do indeed seem very informed about the CE411A, have you EVER operated one? What are your facts? Do you have any? Or only hot air, with AirBus bias.

I am just curious 411A – from your statements is it true to say that you are experienced on Airbus FBW aircraft? Which type and how many hours? You seem to know a lot and I would love to learn from your obvious experience as I am only a beginner.

[M14P]

No, I've never operated a 411A - but I have operated many similar CE types. When public confidence was severly injured by a number of bad crashes of the 411A due to poor engine reliability and inadequate single engine controlability. Cessna got the F100 (SuperSabre) test pilot to fly an engine failure profile in one as the whole thing was videoed. He crashed the aircraft on final approach. This led to the ultimate demise of the 411A and the development of the much better 421.

Yes, the 411A was a rubbish aircraft - Aviation Consumer said "..we would hesitate to even get in a C411A..."

The A320 series, however, has demonstrated and contiues to demonstrate excellent flying qualities and a fantastic safety record. When all the chaps here talk about 'being unable to override a computer' I am not sure that everybody understands the FBW fundementals. The FBW is normally quite passive - achieving the desired performance by sublty altering control surface deflection (as I said before yaw dampers and rudder ratio units have done this for years and every Boeing around has a fistful of them). The ONLY time that the system becomes 'invasive' is at the performance and structural limit of the envelope - for example at extreme angles of attack where it will maintain maximum alpha with the sidestick fully back or at the G-limit of the airframe thus enabling the pilot to be brutal with the controls but without causing damage to the aircraft.

In summary, the FBW 'limits' are there to make it easy for the 'average pilot' to derive MAXIMUM performance from the aircraft in an emergency situation such as a GPWS alert or in windshear without having to have superhuman piloting abilities.

The situation with L80 Standard ELAC has proven that in ONE very unusal case on an aircraft with ONE VERSION of a flight control computer limited pitch authority occured. Without this it is entirely possible that the aircraft may have stalled on approach with a very different outcome but this is one hypothesis too far.

For the record, I am glad that 411A will not be travelling on any Airbus types - it will severely limit his ability to bother the rest of the planet with hs nonsense and rubbish.

My best regards to all the professionals on this site.

[This message has been edited by M14P (edited 04 June 2001).]

[Richthofen]

Methink we have to update our rules of thumb :

Pushing the stick - houses bigger
Pulling the stick - houses even more bigger

So it comes out that flying is easy with an airbus, no so much difference between the buttons.

[411A]

M14P---
Would agree with you that the A320 series aircraft a unique acheivement, the FBW system does indeed work very well within the performance envelope, but at the edges, when maximim performance is needed to avoid disaster, it would seem to be impossible for experienced pilots to regain the desired profile, unlike in a conventional aircraft. AirBus really does need to vastly improve their product.

With rergard to the 411 aircraft, it was the first cabin class twin that Cessna produced, is very fast, and contrary to your information, the engines are very reliable if treated properly. I have owned one for nine years so I should know. When it was introduced in 1965, it was purchased by attorneys and doctors with the usual predictable results....up in flames on many occasions. If flown properly, much like the A320, it will perform flawlessly, but unlike the A320, it does not have a FBW system to get in the way of a professional pilot. Using a USAF F-100 pilot (single engine) for the test flight was not the brightest idea the manufacturer had. Wonder if ex-French Air Force types are involved with the AirBus?

[M14P]

So you don't like military pilots or test pilots or doctors or lawyers either?

I bet you're real fun in a bar.

Anybody else going to post some sensible responses?

M14P

[Magnus Picus]

Airbus would have done better releasing the following
"Crew are advised not to land our aircraft if windshear exists"
Could have saved themselves all this bickering.

I think the FINGER POINTS AT SPANISH ATC!

Gerona, Britannia 757 - Hull loss due TS/WS
Bilbao, Iberia A320 - Hull loss due TS/WS

Both incidents could have been prevented if a 'Safety conscious' individual had been operating TWR frequency, describing the conditions a little more honestly.

Give the crew a clue, Manuel!

[411A]

Magnus Picus---
The Gerona Britannia 757 accident was due to the aircraft landing very long and over-running. Why would you want to blame the tower controller when the crew clearly mis-judged the approach and landing? The solution is to (what a novel idea)....go around, or divert.

[Kangar]

Folks,
Check the postings in Fragrant Harbour to see why 411A is regarded as a sad old git. Try to make posts with a small basis in fact in the future. Your comments are so uneducated you could not possibly be a pilot.

[Frederic]

411A, AI should improve their product? Ofcourse they should. Any manufacturer producing anything should, and they are.
Do you have any suggestions for our friends at AI on how they should improve FBW. Dying to hear from you! Kind regards, Fred.

[411A]

Fred---
Hiring a few Boeing FBW design engineers would be a good start. Suspect that the AirBus series however is flawed in many areas, see "How safe is the airplane you drive" on R&N. Not a pretty picture.

[shortfinals]

411A

Wrong again two posts ago. At Gerona the 757 went off the side, not over the end, on a very nasty night. The crew had the runway in sight at DH and lost it again in mist just before touchdown. Nose gear went up thru avionics bay and screwed up almost everything electrical as well as electronic. Not nice.

And inadequate weather advice from tower again. The latter is beginning to sound familiar on this thread.

Try again when you know.

[Brad737]

I am comfortable with the redundancies designed into FBW systems, that is functionally. I take issue, though, with a computer programmer acting as PIC in my stead. There should exist, on the yoke, a kill switch to disable all the magic. I can't believe that the response to an accident attributable to software is to "fine tune" that same software. What about the next time an AirBus pilot finds himself in a situation that the programmers hadn't forseen.

[411A]

Shortfinals--
I was at Gerona one week later and talked to the tower supervisor. The Britannia 757 landed half way down the runway and went off the runway (side) at the end. Clearly a mis-judged approach and landing. I have operated to Gerona many times, it is NOT a difficult airport. As the CREW has the responsibility of landing the aircraft (not the tower operator) it is ludicrous to point out otherwise. The wise old advise...if in doubt, simply go-around. Even you should be able to understand this.

Brad737---
It will most likely ah....crash.

[overstress]

oops, see below

[This message has been edited by overstress (edited 06 June 2001).]

[overstress]

411A:

Oh it went off the end, did it? Went there did you? Spoke to ATC eh?

Well take a look at this, 411A, are you capable of clicking on the link?

http://www.geocities.com/Vienna/Opera/7541/balcrash0.jpg

I'll give you a clue, 411A, as you obviously don't have one yourself, the END of the runway is the narrow bit with the numbers painted on it, the side is the longer edge ;)

[This message has been edited by overstress (edited 06 June 2001).]

[411A]

Overstress---
Looks like they are at nearly the end of the runway to me, off to one side. Landed long, just as the tower supervisor mentioned. Clearly a Britannia crew fu@kup to me. How else would you discribe it? Quit making excuses for very POOR pilot technique, ....blame the tower? (the tower made me do it).
Lets put the tail on the donkey....Britannia style.

[airforcenone]

If I remember correctly the BY incident at Gerona had a few additional circumstances:

1. Gerona was the alternate.

2. As a result, the fuel state was likely to have a large significance in the thought process.

3. Bad luck on the day.

As always, please correct me if I'm wrong!

[Edited for poor grammar]

[This message has been edited by airforcenone (edited 07 June 2001).]

[shortfinals]

411A

The guy in the tower would say that, wouldn't he? He's human and is not going to point out, gratis, any ATC shortcomings.

Before dumping any more opinions on us, read the AAIB's preliminary statement on the Gerona event.

Meanwhile your overall thesis in this thread, which remember is about the Bilbao event, seems to be: If it happens to a Boeing, slag the crew off; if it happens to an Airbus, slag the aeroplane off.

It must be very undemanding to live in a world where things are so straightforward.

[caulfield]

Magnus Picus,
Its the pilot-in-commands responsibility to continue an approach or go-around.Not ATC!Your derisory attitude to Spanish ATC is below the belt and misinformed.You're not a white-hatter per chance?Runway condition and windhsear reports(of any value)are mostly pilot-generated anyway.
KLM tried to blame Spanish ATC for the Tenerife disaster.ATC's role was scrutinized in the Eastern 1011 everglades and the Erebus disaster.Unfairly,I believe,on both accounts.
As pilots,we expect and get unrestricted control over our fate.When things go wrong we cant turn around and blame ATC.

[screwjack]

shortfinal:

B R A V O !
D A C A P O !

Why is this sort of "A vs B" always so fanatic? Nothing is perfect...

screwjack


(or like some Chinese saying: "you bette going with Boeing") :-)

[bunyip]

When you criticise an American, even if your points are valid, they respond by attacking you. When you criticise an Airbus pilot you get the same response. In the end, there is no communication.
I do not fly the Airbus, and have never wanted to. I have seen it in the news since it came out, in mostly negative reports. It clearly is not as good as the Airbus supporters think it is, and not as bad as its critics say it is. But even if the truth is in the middle, it has faults (and so does the Boeing product).
My own home PC fails at the most arkward times, and since the A320 (etc) is ultimately flown by the computer with suggestions by the pilot, the pilot is bound to lose control of it once in a while.
The Boeing product takes this into account and if I need to, I can put that airplane wherever I want, whenever I want.
When I feel I am not as good as a piece of machinery made on a production line in Asia, I will be glad to fly the Airbus.

[Frederic]

bunyip,
"The Boeing product takes this into account and if I need to, I can put that airplane wherever I want, whenever I want. " ?
Although I appreciate your view on the subject seems to be more openminded than most other's on this string, I have to disagree with the above statement. You cannot put the any aircraft wherever you want whenever you want. Aircraft have aerodynamic limitations. Maximum angle of attack will give you maximum lift coefficient on any aircraft FBW or not. So the manoeverabimity of an aircraft is limited by the amount of lift it can produce.Boeing aircraft will allow you to pull the aircraft to a slightly higher angle of attack. But what is the use? Higher than max alpha will give you a lower lift coefficient, and so LESS manoeverability. The AI FBW system is designed to give you maximum lift coefficient whit full back stick or max G, whatever is higher. You do need to allow the system to temporarily overshoot it's limits and -MAYBE- that if where AI didn't allow enough "play"?
Where I think most critics of FBW are wrong is that they don't differentiate between design faults and inherent defficienties. In this incident there -probably!- whas a design fault that prevented the aircraft from achieving maximum angle of attack. So there is one element in a much bigger system that failed to work correctly instead of it being inherently defficient. I think every airliner should have angle of attack protection. Please understand that this does not limit the authority of the pilot. On the contrary, it concistently gives the pilot maximum manoeverability right when he needs it by simply applying full aft stick. That is provided it works well. In this case it didn't. So there is a fault in the system. And apparently AI is correcting it. As usual in aviation you immediatly hear about when things go wrong. But how many times did AI's FBW save the day?

[M14P]

Quite.

It doesn't matter how many times you explain it - people who do not want to understand will not.

Having rubbished the whole thing for a purist view they will then fly their aircraft with stability augmentation devices such as slats, yaw dampers, autothrust, Thrust Assymetry Compensation, powered flying controls, autobrakes, mach trimmers, FADEC, and all of the rest of it that we take for granted. This they will do safe in the knowledge that they are 'really flying it' because they have a q-feel back-driven wheel poking out of the floor lending the impression that it is directly connected to the flying controls.

Having done this they will leap into their trusty car - equipped with digital engine managment systems, antilock brakes, traction control, power steering, adaptive suspension, gearboxes that monitor steering wheel angle and throttle pedal position - and drive home.

It's fantastic to live a life so unimpeded by technology.

[adams]

Well I've flown the A320 for 10 years, and on many occasions, following a turbulent approach, I've run out of elevator authority during the flare. I've always filed an ASR, and Airbus have always responded that it was my fault. On one occasion, they said that I probably hadn't applied full up elevator as there is a detent which has to be overcome. Now they have finally recognised the problem, and introdueced a flap 3 procedure for approaches in turbulent conditions. My point is that this problem, which has been experienced by many pilots in my company, so presumably in every other company, should have been recognised and acted on years ago. Mayben some time in the future they'll work on the problem of reversed aileron effect during an approach in turbulence. This is a much rarer problem, but exists none the less. The rudder solves that problem - just like the good old days.

[Haas_320]

I agree wholeheartedly, The AOA protection is a very nice idea but evryone can see that in special circumstances (turbulence, ground effect) the detirmination of AOA can be less than perfect. So pilots end up limited by an inaccurate system. I have always felt that the protection system should be there, but that there should have been pressure sensors in the stick. full deflection would alow the pilot control with in the envelope, but a further pull of lets say 25 pounds would allow the pilot to exeed the envelope, I think this would have been a nice trade off.

By the way I absolutly hate normal law on final and in the flare turbulent or not otherwise it is a great invention. http://www.pprune.org/ubb/NonCGI/frown.gif

[This message has been edited by Haas_320 (edited 09 June 2001).]

[bunyip]

Obviously the Airbus FBW and control logic will be the future of airline aviation, and if the problems can be recognised they can be worked out. If they are rejected as merely complaints by the uneducated then there is less chance this will happen.
You make the point for me that it might (has) happened that the computers have restricted the airplane maneuverability because of a fault in the computer (logic, maintenance, programming). In a conventional airplane, never mind that the pilot is not really moving the controls but via hydraulic servos, it is possible to set whatever power and attitude desired. Sometimes the pilot can save the airplane this way, and sometimes the Airbus system will prevent it from being saved.
There must be a middle ground.

A question please; I flew the B737-200 and it had Control Wheel Steering. Is the Airbus system similar to this in its operation?

[Amos]

Yes...only better!

[Frederic]

M14P, Adams, Haas 320,
Thank you for confirming the point I was making: Aircraft need systems to provide optimum performance, and limit protections, but the systems that provide them haven't been develloped enough. Don't forget the A320 was the first airliner to have full FBW. So the system is pretty new to airliners and the A320 technology is -relatively- old... On military aircraft FBW has been used since the early 70'ies! (F-15,F-16...) So it has been develloped to a much greater degree and so it currently works so well that there are almost no military aircraft left that are designed without it. The fact that the A320 has problems to atain the required angle of attack during the flare means there is a small (but not insignificant!) problem with normal law in AI aircraft. It does not mean that FBW is inherently defficient. Weigh of the advantages against the disadvantages and I would prefer to fly a protected aircraft any day. Give AI a chance to devellop and don't forget Boeing had to and still has to do the same with their aircraft.
Open your mind...

PS: Haas320: Normal law has converted into direct law by the time you flare (unless you start your flare above 100feet !?) Adams: I see your problem with needing so much aft stick in the flare, and I agree. The A320 artificially lowers the nose during the flare. this is because at first, pilots used to "overflare" the aircraft. Maybe AI has overdone it a bit. Good point. It doesn't feel natural to pull the stick that far back either.

By now you might have gathered that it is a great ambition of mine to go and work for AI to help devellop their FBW system ;-) . Still a long way away though.

[This message has been edited by Frederic (edited 10 June 2001).]

[Haas_320]

Dear Fredrick

You have confused two things in your post on the further developed 330 and 340 Normal law blends into direct law at 100 feet for the flare. In the 320 at 50 RA feet flare law becomes active wichis normal law with the adition of memorising the current pitch attitude and starting at 30 feet begining to reduce pitch attitude to reach 2 degrees nose down in a period of 8 seconds if there would be no pilot action. This is the very thing that would limit your pitch up authority in the flare. Unless like was mentioned in the post that started this thread you would hit A protection because of windshear above 100 feet RA. This system will be with us as long as there are 320 around even though an improved system is available on the 330/340 alas.

The point I was making that if there was an override available that would alow a larger input than full stick by pressure sensors al benefits of FBW could be combined with final authority were it belongs with the pilot.

The Concord was equiped with FBW and could even react to pressure on the yoke should it become yammed.

[This message has been edited by Haas_320 (edited 10 June 2001).]

[411A]

"yammed"? Glory be, a southern boy!

[Haas_320]

Yihaa as far south as SXM DWI beat that.

[Lu Zuckerman]

To see how these problems got started please go to Rumors and News and check the archive for the last ten days and click on HOW SAFE IS THE AIRPLANE THAT YOU DRIVE.

------------------
The Cat

[vikingwill]

The thing that really bothers me about this entire issue is that fact that Airbus expect to have validated update software soon. Presumably the flawed software was validated, but clearly the validation process itself needs to be severely questioned otherwise one has to ask what other forseeable risks are present. I accep that unforseeable risks can not be eliminated, but surely to God wind shear is forseeable, and if the incident (accident) was recreated in the SIM, how on earth was this missed in software validation! There are very good International Standards on risk analysis and management in many fields - were (are) these not used?

[Frederic]

Haas-320, thanks for enlightening me, I learnt something new again...
I know about the derotation law, but I seriously doubt the aircraft would stay in normal law because if it would that would impose a problem after touchdown. Once on the ground the amount of G is of course one, and so a pilot imput demand of , say 1,2 G might result in a controls runaway since it is impossible to reach 1,2 G! So somewhere along the way the aircraft must convert into ground (direct) law? I might be totaly wrong of course, but this is how I understood it. Also if it would stay in normal law, it would conflict with lowering the pitch attitude since normal law tries to keep one G and lowering the nose would result in less than one G.
Your idea of providing pressure sensors is a good one, but on the other hand you will need to train your pilots to recognise when the system needs to be overriden. The purpose of the system is to provide max alpha immediatly with full aft stick. If you allow the pilot to override the system, he will do it also when increasing the alpha will decrease the performance. There is little use in providing a protection system if it can be so easily overriden since the nature of a human is to think he is right. The tiny (although apparently present) risk of the system malfunctioning does not weigh of against the fact that it provides G protection and/or optimum alpha and so performance. If you put two identicial aircraft in the same conditions at the same speed and altitude, the one that provides you with max alpha immediatly will always win in a "pull-up" contest, unless you are above the speed where you can pull more than -in this case- 2,5G. And I am now talking about alpha protection, not about the derotation law wich I never tought was a good idea anyway. But even then the risk of hitting the mountain because you can pull 2,5 instead of maybe 3,5G does not weigh of against you breaking the aircraft in two due to overstress. An ideal FBW system would be one that would have a variable G-limit system continuously weighing of the risk of overstressing the aircraft taking into account its actual weight and load distribution against the risk of hitting an obstacle due to a to low available G-limit. I'm talking about scientificly calculating the risk. I'm sure it is possible to devellop a system like that certainly taking into account EGPWS is now certificated. But this is aviation, and certifying something like that would take years. And AI/FBW slaggers, before you declare me mad again, this would be a system that would provide the pilot with more authority and it would not of course pull up by itself. The imput would be pilot commanded. A lot of people tell me I should stop smoking funny cigarettes when I talk about my idea, but hey, at least I come up with one.

[Flight Safety]

Frederic,

What is needed is a Direct Law override button, which I understand the Boeing FBW system has.

This obviates the need for a "risk analysis" computer. Can you imagine trying to override 2 layers of software in an emergency situation (beyond the FBW software's ability to cope). Not only would have to override the FBW computer software, but also the "risk analysis" software that's trying to decide if it should allow you to override the FBW software or not.

The Direct Law override button will do nicely thank you.

------------------
Safe flying to you...

[TvB]

vikingwill and all:


found this in the last AW (issue June4th, page 22):


" Airbus' revised software covering the A319/A320's automated angle-of-attack (AOA) protection is scheduled to obtain certification by the end of the month. The software now being modified was not the A320 series' original AOA protection, Airbus officials stressed. The in-service protection's software was altered two years ago when operational feedback indicated that heavy wind shear could bring aircraft too close to a stall warning. However, the modification went "slightly too far" and needed to be revised, the Airbus officials noted..."


To me this still doesn't answer what they have designed into these software programs in case of a go-around command by the crew. I believe the a/c should respond to this by all means and not contradicting or interfere with any other modes other than "climb".


I was told a go-around with an A320 would still be possible, even after touch down, but in this case you'll get a master warning (quite disturbing). Apparently this did not work in Bilbao at all, so therefore the parameteres have to be revised.


And I agree vikingwill, the original/altered certification is in question here. But I doubt that in any office of a regulatory/oversight administration we would find people qualified enough to make such a decission. Those who are capable are more likely working on the other side, in the Industry, as they get 3 to 4 times the pay there and have access to all data and design specifications (I believe some of that stuff is still considered "propriatory information" and the manufacturer will not hand it out).


Usually the governing questions in this regards are: "What is required by the certification?" and "How is the aircraft going to perform it?"


The later might become reduced to: "Can the aircraft perform as required?" Answer: "Yes" Stamp: "Approved"

TvB
(independent) aviation editor
www.aviationsafetyonline.com (http://www.aviationsafetyonline.com)



[This message has been edited by TvB (edited 11 June 2001).]

[Frederic]

Flightsafety, you seem to jump into "negative thinking" to quick. Try to find reasons why the system would work, instead of only why it wouldn't. You would not need a "second layer of software" to get this system to work and a minimum amount of 2,5G would always be available as it is now. So it would always provide you with minimum or additional performance. I think people are having problems accepting a system like this because they think it would be very compex. It is very simple to calculate that risk. Here is the logic:

1. Get me (from a database and/or G load and current mass quantity and distribution sensors) the maximum current G-loading the aircraft can handle at this moment before there being a risk of it breaking into two bits.
2. Get me the distance, size and closing rate of the nearest obstacle in the flight path. (Easy peasy, since EGPWS has got all that info ready and certified!) Calculate how much G I need to avoid it.
3. Do this 200 x per second and keep updating the FBW with the lowest of the two values.
Et voila, you have a system that will protect you the best it can.

The problem of a Direct law button is that people would misuse it. If a pilot pulls up for an obstacle and "guesses" he will not make it he WILL push that button. So that means that the whole point of having a protection system is wasted since the pilot will override it when he panics and might damage the aircraft, thereby increasing the risk unneccesarily. Don't think aircraft are infinitly strong. Ask any aircraft engineer: aircraft have very definite G limits, and going aver them WILL brake them. Of course the 2,5Gs AI takes as the maximum are very conservative and not addapted to the current state of the aircraft. If you want to minimise risk you have to calculate risk, not guess it. Take for example sheduled performance: I've seen so many pilots taking their hands of the thrust levers before V1 because they think "the aircraft will never stop before the end of the runway". But 1: it has been calculated to do this, 2: it has been tested and physically proven to be able to do this and 3: how are you going to know by just looking? Defenitly if you've probably never done an abort from V1 in your life (like a lot of pilots never have.
The problem is that in an emergency you don't have time to calculate your performance manually so you need to have done it either on forehand or have a really fast computer calculate it for you in real time.
So you see flightsafety, in my system the "risk analasys" software IS the FBW software and does not consist if an extra separate layer to be overriden...

[This message has been edited by Frederic (edited 12 June 2001).]

[stator vane]

bunyip:

just noticed your statement about how an american will attack when criticized even when it is right and then you really go off the edge and put an airbus in the same sentence.

the fact that the individual you refered to happened to be an american, is not a proper basis for your statement in such general terms.

some americans will actually listen or read as the case may be.

but is it an "attack" to point out the fact that you may be a bit too general in your conclusion?

[Brad737]

frederic
Your post tags you as an extremely technically oriented person. You are well spoken. Your argument, however, is flawed.
I would take issue with your contention that this "direct law" button would lead to abuse. Professional Pilots rarely find themselves in such a position as to require the overuse of this button, we see to it that these situations do not occure with regularity. That's what experience is for.
Secondly, if I were to push this button, thus denying myself of "programed" protection, I can state with utmost certainty that I will not snap my aircraft in two in a 3G pullup or degrade my airspeed to a stall. Anyone likely to do so does not live long enough to occupy the pointy end of a commercial aircraft.
Your post illustrates what is wrong at AirBus headquarters. You think the pilot is something to protect the public from, not a highly skilled and experienced asset to be incorporated and trusted into the cockpit. I am not anti-FBW, I think it a fantastic development. I simply demand that in a situation that I deem prudent(software anomally, unforeseen event by programmer, etc) I have the ability to bring 10,000 hours of experience into play.

[beardy]

Brad737, you may have 10000hrs of experience, others don't. You may believe that this will lead you to being infallible, others wouldn't.

[Brad737]

beardy
If that's the message you got from my post then I should be faulted for it's tone, though not it's content.I was not bragging, I was simply holding myself up as the average airline pilot for use in my example.My many hours do not make me infallable but they do provide for superior adaptability and judgement in an infinitely fluid environment such as aviation. A programmer can only account for a finite number of possibilities. I see a disparity here.
AirBus' philosophy reminds me of a joke about the future cockpit containing a pilot and a dog. The pilot's job is to feed the dog. The dog's job is to bite the pilot if he touches anything.

[Haas_320]

From sim experience I have learned that emergency procedures need to be STRAIGHT FORWARD and SIMPLE. Other wise I GET IT WRONG, (let the one who consistantly get it right cast the first stone) It would be nigh impossible to teach the correct use of a non intuitive system like a direct law push button. Just having the take over push butten couses enough confusion.

[High Volt]

Airbus = too clever: I can't understand software nor do I think that I should be expected to. Give me a Boeing airplane, it knows its place.

[Flight Safety]

I guess my feelings are similar to Brad737's.

The autopilot has had a release button for decades. That button is needed for two reasons. One, the autopilot is a system that's not used all the time, so turning it off and on is normal for that sytem. But the second reason for the autopilot release button is because the autopilot can and does fail, and pilots are trained for this and it's practiced in the sim.

Why then should the FBW envelope protection system be without a release button? Granted this system is not cycled off and on the same way as an autopilot, but the system is subject to failure just as an autopilot is. I agree with others that FBW envelope protection is a great innovation and a great system, but why should this particular system be so "sacred" as to not allow the pilot to override it in an emergency? Why should this particular system have a different design philosphy towards possible failure and safety, compared to the autopilot?

Now what I'm about to say, I've withheld from saying for months on these forums looking for a right time to bring it up, and this appears to be the right time.

Is there any connection between the Airbus design philosophy of their FBW systems, and the non-US civil avaition authorities that allow low time pilots in the FOs position?

I'll try my best to articulate what I mean, and the joke about the dog and the pilot might apply here. We all know that some feel that the future of flying is pilotless aircraft. Some argue this future will be safer, and some argue is will be more cost effective.

Is it possible that both considerations (safety and cost) are at work in the Airbus design philosophy, at our current stage of technology development? FBW envelope protection has clear safety benefits, however lowering the requirements for pilot experience (thus lowing costs) does not. So is the design philosophy of Airbus FBW systems driven purely by safety considerations, or is there also an attempt to build in a requirement to allow lower standards of flying experience in the cockpit, creating what I would call a "mixed objective" design philosophy? Is there an attempt to design into the systems, various compensations for a lower standard of flight experience, including possible "safety" contraints that would prevent a less experienced pilot from making a mistake in judgement? Is this why the Airbus design philosophy "is the way it is"?

I know this is "reaching". You'd have to check out how Airbus markets their aircraft to the various airlines, and if pilot costs are a factor in that marketing. You'd also have to check out what kind of pressure Airbus, and maybe some of their airline customers, apply to the various civil aviation authorities to try and lower the pilot standards for experience.

All I know is that the FBW envelope protection system is subject to failure just like the autopilot is, and both should have a cutoff (or release) button if such an eventuality occurs, just as it did in the accident that started this thread.

------------------
Safe flying to you...

[This message has been edited by Flight Safety (edited 15 June 2001).]

[Frederic]

Flightsafety, Brad 737, I strongly disagree with your incorrect vision on the AI phylosophy. I do not see the pilot dissapearing from the cockpit at all in the future and I do certainly not feel or think it is Airbus' intention nor mine to do so. In fact, I think the Airbus FBW's lend themselves much better to manual flying. Actually, the current devellopement in avionics shows a willingness to make them more natural to use, and to allow the pilot more insight and so more imput into the situation. Stop seeing FBW as something that limits the pilot. I am a line pilot, and although maybe not being such a natural as Brad seems to be, I do believe strongly in the importance the pilot has in flying airliners. I think he should very much stay in control and I don't think FBW prevents him doing so. Ask any F-16 or Eurofighter pilot what they think about this... You are also forgetting that AI FBW IS overridable. You can switch of the FAC's or ELAC's or hold the trimwheel in position (you didn't hear me say that) to go into direct law and have a conventional aircraft in your hands. But it isn't designed to do so. This would be like having a car with an overridable antiskid. I can assure you that as an average driver, (not a superior one like Brad ;-) (only jokin' Brad, I know you didn't mean it that way) ) , the first thing you will do the day that kid jumps in front of your car and it LOOKS as if you're not going to make it, is push the "override button". The CHANCE of you hitting the kid because you disconnected the system will always be higher than if you didn't. Come on, Formula 1 drivers use active suspention and anti-skid braking. Are they inferior drivers, guys?? I bet my bottom dollar accidents WILL happen because of the electronics going wrong in one of these systems. What do you want to do? Do away with anti-skid??? I never doubted pilots are great decision makers, but they (I) do not have built in G and angle of attack meters. The final decision to roll the aircraft left or right or pull more or less G's should always be left with the pilot. But compare it with FADEC. The system is designed to give you the maximum it can get immediatly. And it does limit the pilot by giving him a limited amount of thrust. It will give you the maximum rated thrust of the engine, not what the engine might (???) be able to do. Why, Brad 737, would you know better how many G's you're pulling than how much EGT or N1 your engine has? Exactly, you need something to measure it with, then you need something to prevent you going over the limit because you know you will one day... The system never questions your decision making ability (you get max rated thrust when you ask for it), but it inevitably has the edge when providing you with max performance within the limits. One day there will be 1 (or God forbid) 2 FADECs going haywire and preventing a conventionally controlled aircraft from e.g. going around. That won't mean that FADEC is crap, or that the pilots should all of a sudden be allowed to get 1000C EGT from an engine that is rated to do 650 EGT. It does mean that a fault occured in the design of the system, wich is inevitable, no matter what kind of system you design. Be it hydraulic/direct, cable or FBW... Stop treating computers like ET's please. Computers are machines, they can and they will go wrong. And they don't posses some kind of personality or have a will of their own. They are systems that need to be develloped, just like all the other ones.

PS: without wanting to sound patronising, but can you please first READ my postings before criticising them?

[metrodriver]

FS, non-us airlines have been putting low time fo's in airplanes even before somebody thought of putting color-tv's in the panel of big jets, no link there with the airbus, btw, us-airlines are doing it too as long as you're not a white male

[AhhhVC813]

Anyhow, it is vitally important to have the ability to pull more than +30 deg & -15 deg in pitch, oh and 67 deg in roll (particularly for a barrel roll), oh yes and +2.5g/-1g (clean). It is also a requisite to be able to stall it, especially if you wish to enter a spin, plus a myriad of other exceptional manoeuvres that are utilised every day........

[Flight Safety]

Metrodriver, what I was referring to is the FAA requirement for a minimum of 1500 hours to even get an ATPL. Not so under most other civil aviation authorities. I'm talking about 400 hour FOs, not the minimum 1500 hour FOs in US airliners.

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Safe flying to you...

[Burger Thing]

A couple of years ago I saw a video of Amexxxxx Airlines. I believe it was the Chiefpilot that times who was making an interesting statement about investigations of accidents/incidents reports. He said, that especially pilots from Overseas (e.g. Europe) tend to rely in case of an emergency or system malfunction on automatic systems, rather than on flying skills. Maybe caused by a in general very uncritical attitude towards automatism.

That was not ment as a judgement, it was rather an observation. It is interesting to see, that it is even reflected here in this particular forum. I am from Europe, too...

And to Frederic and AhhhVC813: there have been cases, where pilots saved the day, by going beyond design limitations. I heard of a starlifter, which lost 2 engines while manouvering in the mountains of ex-yugoslavia. He overboosted the remaining engines. After landing he replied to the question, why he firewalled (and so ruined) 2 good engines, with '...because I couldn't forward them even further !' He obviously needed more than the maximum rated thrust of the engine, and the engine was able to do so - and saved his butt !

Another case was a TriStar, which had a stucked stabilizer, causing the ac going into a normally uncontrollable nose-up attitude. The pilot recovered by constantly banking the ac heavily to one side to another, to lower the lift component, until the situation was under control.

About Formula 1... Ask Coulthard and Hakkinen what they thought about their electronics when they were stucked on the grid-line a couple of times.....

[Frederic]

Burger thing, thanks for reading my previous postings. Of course there are situations where going over the limits will save your butt. But 1: he would (might, I don't know?) have made it if he wouldn't have overtemped his engines. 2: If he would have pushed the engines further, at some point, he would have destroyed them. The fact that he COULDN'T push the engines any further saved his butt as much as the fact that MIGHT not have made it if he wouldn't have pushed them further than their rated limit...
BTW: ask Coulthart and Hakinnen what they would think of removing all the electronics and limit protections from their cars! Them being stuck at the start every now and then does not weigh of against the edge it provides them with when they do work. But I'm straying out of my field. The F1 was mearly an example to make a point. To all: Thanks for replying. Discussions like this stay fun if people (me included) are willing to open their minds and talk on a reasonable tone. Thanks again for making me think about stuff. Have to get on with my life now. CU

[Haas_320]

Fbw acft do not crash les or more, they just crash for diffrent reasons, Reasons that in my view scare us pilots more.

[Burger Thing]

Yes Frederic, I agree. I am also enjoying good discussions, it widens our horizon and sometimes we can even learn something. That is the way it should be.

[TowerDog]

Since I have never flown anything but Boeing and Douglas airliners, I am most interested in this discussion:
One side thinks the computerized airplane will save the pilot and the other side thinks the pilot will save the computerized airplane
given an overide button.

Hmm, interesting topic.
My first thought would be: If this A-320 plane is so smart, and have all this "laws" coupled with the EGPWS and all that other magic, I am having a hard time understanding, why did all these accidents happened:
Gulf Air, Indian Airlines, Air France etc?

Most of my experience is on the B-747-100/200
with Pratts and without any engine limiters built in. Therefore: If you got caught in a windshear situation, you can firewall the motors and gain enough power to
equal a fifth engine.
Yes, you would have to explain to the boss why you did it, as it cost him 4 hot section inspections and perhaps engine replacements, but ah, there has never been a B-747 lost to a windshear accicent yet.

If however the bean counters and the engineers had installed their limiters to "save" the engines from pilots, the tally may
have been different.



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Men, this is no drill...

[411A]

TowerDog--
Now you should know why many companies do not allow their employees to travel on FBW Airbus equipment, on company business. Airline pilots generally do not know what the travel policies are at large corporations that are not airlines. Interestingly enough, one US military contractor that I know about, which manufactures FBW military aircraft, absolutely avoids travel on A320,330,340 equipment but has no such restriction with the B777. The French had the opportunity do do it right but dropped the ball, big time.

[Haas_320]

While writing this post another was added to the thread. Just to keep evrything clear I agree with tower dog's statement about firewalling engines.


I have to agree. I like the 320 but I can not understand why the pilot can not "firewall" the engines.But then again this is impossible on any fadec powered acft. For all those bringing up the "but you cannot stall the acft so initialy you can use more of your kinetic energy" argument don't because it is not tru normal laws of aerodynamics aply to fly out of Windshear or a gpws situation only power will save your but in the long term. :mad:



[This message has been edited by Haas_320 (edited 17 June 2001).]

[DISCOKID]

411A - It is not really surprising that a US military contractor does not like its staff flying on Airbus but is happy for them to use Boeing. This has nothing to do with Airbus FBW but is the usual petty policy similiar to the policy that US government employees are only allowed to fly on US airlines.

I work for a firm that has one of the largest annual corporate air travel spends in the world - large corporations are only concerned with choosing top airlines and the discount they receive.

Provide the name of a company with a no Airbus policy who is not connected to Boeing and your argument will have more strength!!

[mcdude]

This thread is slowly turning to s....

High volt - Granted, this accident seems to be a software problem (however applicable only to some 320 - not 319/321) I fly the A320, but I have no knowledge or any requirement to know about the software it uses.

411a - Sorry mate, I think most airline pilots couldn't care less about the travel policies at large corporations except their own.... If your new "freight & pax airline" (sic) opts for FBW aircraft (unlikely I know), I'm sure you will operate it like any other aircraft type you have flown ie with common sense, airmanship etc - the Airbus responds well to these basics!

So far the A319/320/321 safety record aint perfect but it aint bad. Nearly 1500 in service, four fatals (in airline service) in 13 years.

This accident is no doubt an unfortunate and near tragic way to correct or perfect a system. Something that has happened to many types in the past, and likely in the future too.

[chrisN]

Towerdog, you mention beancounters (and engineers) as if perhaps they are all the same: "If however the bean counters and the engineers had installed their limiters to "save" the engines from pilots, the tally may have been different."

As a former beancounter (car industry, not aviation, but there are parallels) and even longer ago an engineer, I have to agree that there are some poor beancounters who don't do things right, and maybe some poor engineers, too, but please don't class them (us?) as being all the same - maybe you didn't mean to anyway.

FWIW, I never stood in the way of a sound safety policy,nor did any of my beancounting colleagues AFAIK. One of the things a good beancounter takes into account is the incalculable cost of lost customer goodwill as well as the sometimes costable (though emotive to some) issues of insurance claims, "value of a human life", and legal liability.

To class us all as tarred with the same brush would be as bad as suggesting that if some professional pilots fall short of particular standard (not that that ever happens . . . ) then all do. I don't think that of your profession, and I hope you don't think that of mine.

Chris N.

[TowerDog]

chrisN:

Well, no I don't put beancounters and engineers in the same basket, but, uh, here is the situation:
You are out there in a dark and stormy night: You are trying your best to survive, hungry and tired you are, say on an approach to Bombay in the Monsoon season, with numerous squaks in the logbook, rain and lightening all around you, low on fuel, then you get a warm and fuzzy feeling thinking about a bunch of engineers sitting in their cozy offices trying to figure out the next clever step to outsmart the stupid pilot who may need max performance out of his plane an any given moment?
Protect the idiot pilots against themselves.

Beancounters would like you to fly around with minimum fuel as that is most cost effective. Also minimum days off for the overpayed and underworked pilots.
Heck, let the F/As fly the airplanes for peanuts. Valuejet tried that for a while.
The pieces are still in the Everglades, but the business plan looked good: Let's hire pilots that can not get a job anywhere else, then let them pay for their own training, and
screw common sense and safety.

Beancounters tend to confuse fast food joints and airlines.

(Many have tried: Peoples Express wanted pilots to sell tickets/ticket agents to be pilots. When UPS started their own airline, they wanted their truck drivers to get a flying licence.
Made sense to the beancounters)

Uh, what was the question again?
Don't confuse the two groups?

I won't, but you walk in my shoes for a week or two and you will hopefully see the situation from a pilot's point of view.

Yeah, flying is easy, just keep the dirty side down, fly low and slow and survive the engineers and beancounters.




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Men, this is no drill...

[moggie]

Sorry folks - but am I missing something? Bilbao is infamous for it's windshear (and does not have a good overall safety reputation) so when you encounter a massive updraught and increasing IAS near decision altitude, should you not go around then? Stuffing the nose down, reducing power and losing energy is suicide as you are then unable to cope with the downdraught/IAS reduction when it inevitably happens - as was the case here. Once you get into the big downdraught at 200' you are stuffed - there is no way to recover.

This one smacks of a poor decision/press-on-itis rather than a problem of FBW (and I am no big fan of FBW, may I say). I believe that the actions of the crew would have lead to the same result in any aeroplane.

And by the way, do those people who ban their employees from flying with Airbus know that the 777 is a FBW aeroplane, too?

[Frederic]

Moggie,
AI has decided to implement a software modification concerning its' angle of attack protection system. So although you are making a good point, I do think there must have been something preventing this aircraft reaching its' angle of attack limit. My guess is that there was not enough allowance for overshoot built into the system and that the reation time was not right. Having said that, I am a big fan of FBW...

[stickyb]

I think there are 2 separate discussions going on here, and there is some confusion and crossover between them.

The argument that a lot of you seem to be getting into is the classic computer vs human argument. Airbus have designed to software to do a particular job. You either like or not, hence a lot of the arguments about being able to over ride or cut out the computer when you want to.

To my way of thinking that is a separate arguement from the thing that started this thread off. In this case there was a clear case of the software having a plain and simple bug, that is not working to specification, and it was that that caused the problem. If there was no bug, then there would be no need for a change to the sofware.
So the real question for me is "Does a pilot know when the sofware is not performing to spec?" If he does, then there is a clear case for some form of over ride or shutoff.
As long as the software works according to spec, and as long as the pilots know what the spec is, then everyone's happy. But if either of those statements become false, then a disaster lurks.

I say this not as a flying professional, but as a software professional.
Cheers

[L337]

Going slightly off thread, How many of you good A320/321/319 drivers have run out of aileron in the flare in a strong gusty crosswind? I have on at least three occasions, and did not enjoy the experience. The 737 seemed to settle just above the runway on a windy day. The Airbus is all over the sky, all the time. Flap three helps things, but the autothrottle, the FBW, and my pushing and pulling contrive to make things very sporting!

:)

[Diesel8]

L337,

I have flown the Airbus for four years and consider it easy to land in a crosswind, even approaching max recommended. Certainly easier than the DC-8.

In other news, the FAA issues an AD limiting the speed at which speedbrakes and flaps can be used on the 737-800.

I'll take the bus!

[Flight Safety]

I'm with stickb.

Not only can the FBW software sometimes fail, but FBW computer hardware can sometimes fail as well. I know there are hardware redundancies built in, but any number of things could go wrong with the FBW and envelope protection systems. Again it's the same as with the autopilot.

I have no objection to the automation of FBW or envelope protection, nor do I object to the automation of an autopilot. All of these systems are great to have. But all 3 systems put a potentially fallable flight control automation system between the pilot and the flight controls. If one of these system fails for whatever reason, then the pilot needs an immediate reversion to direct operation of the flight controls, especially during a critical phase of flight.

As stated previously, the autopilot has had a cutoff switch for decades, so why not make the same method of immediate pilot reversion to direct control of the flight controls, available to the pilots for these new more modern systems? Does it make any sense not to provide this immediate reversion capability? Have autopilot failures been the cause of accidents in the past? Have FBW and envelope protection failures been the cause of any accidents?

Please forgive me if the failure override similarity between these two types of systems seems too direct and simple to my way of thinking.

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Safe flying to you...

[This message has been edited by Flight Safety (edited 23 June 2001).]

[Amos]

Changing the subject slightly, but still on the A320, what do you 320 drivers think of the fact that the a/c has a LOC selection but not VOR/LOC on the MCP? For a super advanced airplane an oversight surely!

[northern boy]

You can do a managed non precision approach by selecting the relevant approach on the MCDU then activating APPR on the FCU.The FMA displays APPR NAV for the lateral bit then FINAL APPR when it intercepts the vertical profile.Hence no need for a separate VOR button.In my company however we are not cleared for managed non precision approaches as the CAA won't allow it.Providing nav accuracy is high however you can transition from managed nav to the localiser.
Hope that answers your question.

[Amos]

Thanks for that northern boy...I accept what you say. Many companies restrict the managed non precision approach,which is why I pose the question of no VOR switch? Instead of piddling around with the heading selector,ad nauseam, to maintain the radial on a selected approach a VOR capture ala the 737 would do it for us.

Or am I just getting too lazy ?

[Diesel8]

Amos,

No need to fiddle with the heading, you can just use TRACK/FPA. The aircraft will then maintain a desired track across the ground, which is of course what a VOR radial is.

[Max Angle]

The lack of a VOR radial capture is a bit strange on an a/c as advanced as the 'bus. The track/fpa funtion is quite good but in real life does not work as well as it does in the sim. I find that I have to adjust the track during the approach sometimes and that together with monitoring the vertical profile increases the workload. Much better for the a/c to track the radial and leave the pilot free to work on the vertical bit. Roll on fully managed nav.

[Flight Safety]

It sounds like the track/fpa function relies on an INS reference (or GPS reference) for ground track information instead of flying a beacon. Is that why managed non-precision approaches are restricted?

[This message has been edited by Flight Safety (edited 24 June 2001).]

[Diesel8]

I think restrictions on managed non precision approaches has to do with individual company SOP's. The company I fly for allows managed nav approaches, as long as accuracy is high.

[Pontius' Pilot]

Our company received the following from Honeywell. (Not verbatim) Coding of certain non-precision approach (NPA) procedures within the A340 FM navigation database could result in an unanticipated vertical profile construction. Specifically NPA's with the MAP beyond the runway could result in the constructed FM vertical profile passing the FAF BELOW the Jeppesen published FAF altitude.

Known NPA procedures which are affected are HSSS VOR 18, VABB VOR 27, YMML VOR 34, FMEE VOR 30. Because 3 of the four are destinations in our airline, and the remaining one an enroute alternate our company has also made it SOP to do all NPA's in selected mode. Guess they are erring on the safe side.

The A340 FCOM 3 also has background info which elaborates a little more on the subject. FCOM 3: BULLETIN #12/1 dated OCT/00.

Personally I have had no problem with the use of the TRACK/FPA during these procedures even in high varying cross wind conditions. Admittedly it does increase pilot workload.

[Frederic]

In my company there is a list of airports and approaches where APP NAV managed approaches are allowed. It seems strange to me that some companies ban them altogether. I think they're much better than conventional non precisions. Oh yeah, Max Angle: In Track/FPA the aircraft flies the selected track. So if there is a xwind gust, although the aircraft will try to maintain the track, there is always a delay in it doing so. So although your track will return to the selected value, you will fly a parrallel track after a gust. Very much the same thing happens in roll and FPA: the FBW does not try to keep the aircrafts wing LEVEL. Instead it tries to keep the rollrate at 0 (stick-free). So if there is gust pushing one of the wings up, the FBW will counter the rollrate with aileron/spoilers untill it is 0. But by the time it has done that the aircraft will already have banked by a couple of degrees. Same thing in pitch The FBW will try to maintain 1G, but by the time it has done that after e.g. a gust, it will already have reached a different FPA.

PS: Stickyb: very good point you're making, but in this case I do not believe there was a software fault as such. There are, in each Flight Control Computer in AI aircraft, two channels using two different programmes written in two different languages. The COM and the MON channels both calculate the same thing and compare the result of their demand through feedback from the flight controls position. If they dissagree I think the computer gets a fault and disconnects from the system. So if there is a software fault that demands a rediculous control position, it will be declared "mad", and will be disregarded. In this case, however my guess is that the overshoot and reaction time values for angle of attack protection weren't right in the whole system. So I don't think there ever was a software "fault" as such. But then I'm not on the investigation board and I'm not an aeronautical engineer, so I don't really know. Nodody really knows untill AI gives us some more info...

[This message has been edited by Frederic (edited 24 June 2001).]