Civil Aviation Flight Safety

[KiranM]

Talking about Airbus, Deccan Herald carried a report that an Indian Airlines Airbus 321, carrying Kerala Chief Minister V.S. Achuthanandan as one of its passengers, developed engine trouble.

Added later: http://www.deccanherald.com/content/117 ... elops.html

[vina]

This is pure - and premature - speculation. But it is not speculative to observe that some vertical fins are weaker than they should be, and that this is because of the regulations that govern how airplanes are built. The FAA, together with its international counterparts, should amend certification requirements for future aircraft to restore to the maneuvering speed the safety status that pilots always believed it had. The rules that govern the structural integrity of airliners should not include asterisks.

That is something everyone can agree with and certainly, it seems Airbus has cut corners with the tail fin. It is the old criticism of relying on FBW as the magic wand for everything. If the electronics collapese, the plane becomes extremely dangerous to fly. You can get away with it in probably 99.9% of the time because the electronics is so reliable, but in the extremely long tail scenarios where the coumputers shut down, you are in extremely serious trouble.

What this author speculates could well have happened. The computers shut down and they "over control" the rudder and it snaps off like it did off LI !.

I do hope that at least Le Champagne was at the right temperature - or maybe Les Chimpanzees in the natty uniforms in the cabin had given away the last Veg. Meal to impress the nearest chick they wanted to impress, like they did instead of giving me my meal

Hmm. What is a good mallu like you doing by eating Veg meals like a Curd rice slurping Tam Brahm !. I thought you would be diggin into all the le plus haute cuisine they would be dishing out in Air France. No wonder, the natty mokeys thought on hitting on the nearest chic chick by giving away the verg ,meal to the nearest anorexic grass eater!

[Singha]

I happen to have some knowledge of how the makers do the FBW type sw and its quite good - I mean compared to airbus/boeing avionic sw, the commercial stuff out there is written and tested by the devil himself to fail at first opportunity

its the stock priced obsessed mkting and cxo types who bring bottomlines into the
equation and press engineering to cut corners. conscientious people from the trenches
would have objected but been roundly ignored or silenced...this is generally seen in
all orgs.

[enqyoob]

vina: I actually have nothing against the Hawai Frogistan flight crews. Even the Natty Chimp DID get me my veg meal (he tried "explaining" that they were "at 30,000 feet, no way to bring another meal on board" and I countered nicely that it wouldn't matter if they were at 10 feet, but since he messed up, he could fix the problem). They gave SHQ and me an upgrade to Le Class de Business the last transatlantic trip I took on H.F., but the rude idiot she-baboon at the ticket office that preceded that trip is another matter entirely. I think it was reaction to that experience that earned the upgrade.

Air France and Airbus seem to think that Gravity and the Atmosphere will believe their rude bureaucratic excuses which they deliver so much like Inspecteur Clouseau. But I still cannot believe what I read here - that they design airliners to a Load Factor of 2.5, and that their vertical tail snaps off if the rudder pedal is floored at speeds way down below the Maneuver Speed. That IS criminal - there should be mass-murder prosecution against the CEO and CTO of EADS, and against whatever fools certified such things for passenger transportation.

On the A380 project, the big delay came because the Frogistanis did not provide the updated CAD software to the Krautistanis, and so the electrical wire layouts done in Frogistan did not match what the production facility's computers showed. So when they tried to get all the cables through the structural cut-outs, it was like a Size 48 Pakjabi Mohterma trying to get into a Size 12 salwar.

At least that happened before the thing was flown. Wonder if the A-380 is designed to n=2.5 or n=1.3. Hope they fly only over the ocean so that the black boxes are safe from discovery.

Singha: I wonder what will happen to EADS stock price if the Black Boxes from AF447 and the Comoros crash show that the tail etc. fell off.

[vera_k]

For some Comorians, the Yemenia Airways crash is no surprise

'Trashy' planes for non-European flights?

Reads like the NWA folks who were plying older Boeings between AMS and BOM and newer Airbuses between US-AMS. Although the definition of a 'trashy plane' is suspect if an itinerary includes an older Boeing and a newer Airbus. I suppose its another reason to fly on Boeings in addition to doing so for supporting a local manufacturer.

[enqyoob]

newer Airbuses between US-AMS.

That's only because it's an ocean/polar route - small chance of black box being found.

[SriKumar]

conscientious people from the trenches would have objected but been roundly ignored or silenced...this is generally seen in all orgs.

Interesting points. On a related point, both the NASA shuttle accidents were affected by shades of this behavior. For Challenger accident, the problem with O-ring seals going brittle below freezing temperature was known and a concern was raised, but it did not 'reach the right people' prior to launch. For the Columbia accident, there was discussion about whether to photograph the foam-hit damage via space satellites but that was over-ruled by a NASA manager (Linda Ham). Bad decision, in hindsight. The following link describes how several requests by engineers were ignored/denied. http://en.wikipedia.org/wiki/Linda_Ham
See section titled: Columbia disaster and investigation report

[SriKumar]

that [EADS] design airliners to a Load Factor of 2.5, and that their vertical tail snaps off if the rudder pedal is floored at speeds way down below the Maneuver Speed. That IS criminal - there should be mass-murder prosecution against the CEO and CTO of EADS, and against whatever fools certified such things for passenger transportation.

Sounds a bit odd. Why would the FAA not have a say in this matter? If the European aircraft are being designed below par, its a safety issue for American public and therefore FAA's responsibility. Also, IF Boeing is designing to a higher safety factor, Boeing aircraft will be heavier and be at a competitive disadvantage. I have to believe FAA people would understand this and try to apply equal standards to all airframers.

[enqyoob]

Forget FAA. Less said the better about FAA's timeliness and situational awareness for the past decade. The Republican administrations totally gutted the ability of most Federal common-sense enforcement agencies, and FAA did not escape. I cannot understand why Boeing is passive on this either, except that maybe Boeing mgmt thinks they can also cut corners and increase profits by not objecting. Remember, the 787 is all about weight reduction and primary composite structure and FBW as well. Sad, but this is possible, since Boeing for the past decade or more, has not been led by engineers but increasingly by potato-chip executives, used car dealers etc.

But.. I simply was not aware of the 2.5 load factor thing (if it is true) - that is so outside what is taught in basic aircraft design that it boggles the imagination. I mean, try calculating what happens when you have to pull a 60-degree-banked coordinated turn at any decent speed and low altitude. And this thing where a critical primary structure actually BREAKS due to control input, so far below the maneuvering speed limits, on the excuse that it says so somewhere in the manual (but the limiters are in software, and the computer can fail!)

This goes against everything I imagined about the actual design practices implemented on these aircraft, and SHOULD destroy public faith, big-time.

The contrast between Boeing practice of separating redundant control linkages as far as possible - compared to old McDonnell-Douglas corner cutting where they put linkages along the same region - was real. I hope the New Boeing has not taken to imitating EADS there too.

[Singha]

Boeing is probably keeping silent because they follow the same practises on the tail.
the two have a vested interest in keeping silent about each other due to skeletons in
their cupboard which I am sure industrial espionage has created a fat dossier.

Embraer, Bombardier etc will keep quiet - they dont want to lose the EU/US market.

Russia could speak up but since they are bad russians nobody will believe them.

the first A320 just rolled off the tianjin line so PRC has no interest. neither they want
to ruffle boeing - orders to boeing are used to deflect US trade pressure on trade
imbalance.

in short, unless a pulitzer prize type gets on this story and congress starts a review board staffed by a panel of eminent aerospace engineers (maybe including a certain professor ) , nothing will come out.

[negi]

Well in times of D&G and many airline operators looking to cutting down costs and even delaying their expansion plans EADS fat cats might be chuckling in their chi chi offices ,i.e. unless what GD says happens for real this would be covered up pretty neatly only to be aired with complete footage and simulations a decade or two later in Discovery or Nat Geo .

[Dileep]

I have a stoopid doubt onlee. I was subjected to severe turbulence several times. Can the reactive force generated by a rudder deflection (especially at low speed) be more than what created by heavy turbulence? I doubt onlee.

I guess the attachment of the tail fin got terribly weak, causing the easy detachment.

A380's wing had failed load test, and some reports speculated that it was finally passed only marginally. Maybe they applied a coat of Camember mixed with Champagni. The testing of the landing gear was shown on discovery. The whole thing was supposed to drop down by gravity, but it failed the test. The smart guys applied some grease on the rubbing surface and it finally came down.

Yes, they shown that on TV, and the guy actually claimed (unless discovery deliberately screwed the voice over translation) that they got it passed by " adjusting the mounting, and applying grease". Then the camera ACTUALLY SHOWED the black grease on the white painted surface.

[Dileep]

Talking about Airbus, Deccan Herald carried a report that an Indian Airlines Airbus 321, carrying Kerala Chief Minister V.S. Achuthanandan as one of its passengers, developed engine trouble.

Added later: http://www.deccanherald.com/content/117 ... elops.html

A most unfortunate incident in fact

[Singha]

unless I am mistaken in most upright plane crashes the fuselage shears and breaks into two aft
of the wing root and the tail section sideslips away, relatively safer due to the lack of bad stuff like
engines and fuel. thats why I think tail passengers have higher % of survival.

I see lots of plane crashes the vertical tail is pretty intact.

unless the EU commission comes and says for sure that the bolts sheared off before it smashed into the water, its just one theory imho.

[enqyoob]

In this case the Fin Verticale had very clearly declared Liberte! on its own. No tail cone or aft pakistan attached. Some distance from where they found bodies and other wreckage. Of course, nothing can be expected to survive a near-sonic terminal dive to the surface. The claim that it hit belly-first (if true, which I doubt very very much) must have been purely fortuitous, the thing was probably fluttering down like a brick. If it did hit like that, how come the Fin Verticale was not vertically crushed and crumpled?

The Chief Inspecteur D'SURETE, M. Clouseau's hasty declaration:

Voila! L'Airbus he remained INTACT until it hit l'surface de l'Eau, and was RIGHT SIDE UP to the very end, it was just going 1000 km per heure DOWNWARDS instead of FORWARD, minor sensor/orientation error, what's 90 degrees after all! BUT we are very far from having any Cluoue why L'Airbus crashed .. it will take many many more bottles de'Champagne sitting in Le Brazil to complete l'investigacion..

sounds a bit Clouseu-esque in its self-contradiction, n'cest-pas?

How can he say this, when they admitted that the sensors reported sudden depressurization near cruising altitude just about when they reported loss of electrical systems? Did the champagne cork at the aft end pop out, I wonder...

Given this obvious self-contradiction and hasty declaration, the only (premature, sure, but no more than L'Inspecteur's) conclusion is that the vertical tail broke off. Something is very very far wrong. The aft fuselage may have cracked open and sucked the passengers and Captain out the back, for all we know.

[SriKumar]

I guess the attachment of the tail fin got terribly weak, causing the easy detachment.

As a very general statement, not specific to any aircraft: Typically, metals do not simply 'weaken' over time. The only way this happens is via 'metal fatigue' (and if it goes beyond yield point), and again, typically, this is designed into consideration.

A380....... The testing of the landing gear was shown on discovery. The whole thing was supposed to drop down by gravity, but it failed the test. The smart guys applied some grease on the rubbing surface and it finally came down.

As a design approach, this is probably not a bad idea. In fact, it might be seen as a good idea, because you are letting nature do the job. If there is any equipment failure, then the natural tendency of the landing gear is to be in down position- which is safer than it being stuck and in an 'up' position. Of course, to achieve redundancy, one should have a separate (motorized) way of deploying landing gear - as failsafe. To rely 100% on just grease to release landing gear sounds odd to me.

On a different note, regarding load factors, I wonder how they come up with the numbers. Do they take the wost storm with the worst turbulence? If indeed the tail section being intact has any relevance to this investigation, it is deja vu all over again.

[shiv]

The only way this happens is via 'metal fatigue' .

Surely you mean le fatigue metallique?

[Rahul M]

In fact, it might be seen as a good idea, because you are letting nature do the job. If there is any equipment failure, then the natural tendency of the landing gear is to be in down position- which is safer than it being stuck and in an 'up' position.

AM Rajkumar makes the point that landing gears are the only things known to mankind which are beyond the purview of newton's laws of gravitation.

[enqyoob]

Investigators have heard a signal from the flight data recorders of the Yemenia Airways plane that crashed last week... "A signal was picked up from two acoustic transmitters from the plane's flight data recorders during a sea search to locate the data recorders this morning," the French air accident investigation agency, known as the BEA, said in a statement.

http://www.cnn.com/2009/WORLD/meast/07/ ... index.html

Design load factors are based on experience, AFAIK - 3.0 to 3.5 for civilian craft, but much higher for combat aircraft. The factor is equal to the max lift divided by the weight. For instance, if you pull a 60 degree-banked turn and insist on keeping the aircraft at the same altitude, and if L is the lift, then only LCos60 = 0.5L is available to counter gravity, which means L should be twice the weight. IOW, n=L/W = 2.0

If the design load factor is 2.5, that means that if you do the above at 67 degrees, and you have enough thrust and flaps to maintain altitude, then you are dead, because n > 2.5 if Le Clowns designed their plane to break the moment the limit load was exceeded.

Those are ze rules, M'sieur! You cannot disobey them!

OTOH, if the design load factor is 3, and they have designed things not to break until 3.5 or 4 like they are supposed to, then you can TRY maintaining altitude at 73 degrees bank - but few civil aircraft have the lifting mechanisms or engine thrust to have that much to spare, so you won't succeed in maintaining altitude at such a bank angle.

So here is moi's Le Speculacion sans Basis about AF447:
1. Hit updrafts and downdrafts around the storm.
2. Lightning strike temporarily zapped le famed "FCS".
3. First Officer tried to manually control wild yaw-bank motions.
4. Vertical tail snapped off, and the attachment to the aft fuselage tore off, making big hole in aft fuselage.
5. With explosive decompression in progress, the cockpit crew put the craft into a dive to reach below 20,000 feet before everyone passed out - the only thing they could do.
6. Maneuver speed was exceeded (or gust loads were much stronger than those used in calculating maneuver speed).
7. Weakened horizontal tail broke off along with part of aft fuselage: most of the bodies found may have been people who were sucked out of the tail.
8. With tail gone, there was little hope of recovering attitude, but the crew tried with some desperate jiggling of engine thrust, speed brakes and flaps to induce enough pitching moment on the wings.
9. As craft started leveling off, one engine fell off, and craft kept going down.
10. Craft SLOWLY started recovering attitude - pilots went to max thrust to maximize lift and level off.
12. Hit the ocean just as attitude was reaching level, though the craft was still moving down at a high sink rate - and moving forward at pretty high speed.
13. Front-heavy fuselage sank nose-down, straight to the bottom.


Trouble is, I think at least one Black Box is located at the tail, so how has it not been located?
****************************

Tres simple speculacion:

The Oiropeans designed the cockpit seat leg bolts also to the 2.5 load factor. When the craft hit turbulence and experienced sudden descent, the seats broke free of the floor and the pilots hit their heads on the electrical system Master Switch (which then turned off) and got knocked out or killed.

This would explain the subsequent events, but not the decompression. Unless they designed the roof to have the strength of Crepe Suzette?

[shaardula]

yep, I love all this "al-knowingness" exhibited by non-pilots on this thread as well. (FCS on A300 - anyone?)

Yup. Sorry. You are right, the A300 is not FBW. It starts with A320 . But N^3 point still holds. The structure that gave way in the A300 over LI was the composite mounting brackets. That is what he pointed out. It obviously wasnt designed for the kind of loads the plane experienced.

Yes, in an FBW aircraft, you can limit the amount of control deflection via software to prevent overstressing of that part. However in a conventional plane, you dont have that luxury and you actually have to design that part for that kind of loads. A design failure surely

newbie disclaimer. but how can that be? wouldn't the actuators saturate? and wont the limits be unknown apriori?

[enqyoob]

The trouble with aerodynamic control surfaces is that the torque required to deflect them is small, but the change in (lift) force that occurs due to deflection, is very large. (Example: at small angle of attack, the pitching moment about the quarter-chord is zero, which means that it takes no torque to hold it at a given angle of attack, and very little torque to change the angle of attack from, say, -10 degrees to + 10 degrees, which means a very large change in lift loads).
So the actuators may not saturate. But with a very little expenditure of weight and money, hardware limiters can be built in, so that the surfaces are not deflected to conditions where the loads are high, or at least make sure that the pedal force required to achieve a given deflection, or rate of deflection, is beyond the capability of a human. Nonlinear "stick force" and "pedal force" mechanisms have been used for, say, 60 years at least. Ole' Prof. Balraman at the eye-eye-tee used to sketch those diagrams during the 3-hour classes where he brought in tea for all his students to wake them up after 1 hour, way before L'Airbus was invented and our expert "non-non-pilots" here memorized Le Manuals d'Airbus to parrot here with thought processes on L'Autopilot.

Much better than having the vertical tail break off, ne c'est pas? This is why if they designed with complete disregard for such elementary notions, it is criminal.

[p_saggu]

I am telling you all, N^3 first got everyone addicted to Pinglis in the BENIS thread, and by the time le'airbus is finally retrieved from under le'Atlantic, everyone will be speaking le'phrench.

[shaardula]

oh so this became unstable as i originally suspected? isn't that even more of a cardinal sin?
the bus becoming unstable unstable due to huge external distburbances that render control useless is one thing. but how can anybody allow controls that can make the system unstable?

i dont think so.

^^^ yeah sagguji, some of the posts were hilarious. especially those digs at elegant

[enqyoob]

It only becomes unstable if the horizontal tail breaks off - but that may indeed happen if they go into a desperate dive, - and don't know their speed - and the aft fuselage is already hanging by a few fibers or "Fabrique en France" bolts specified by people who can't tell the difference between pounds and Newtons. Usually in these things, the "Impossible!" happens because several "I am sure they are not THAT stupid"s combine.

The thing that bothers me is why there was decompression just because the plane flew into a storm at some 39000 feet - and why there was no SOS. But you already hear a long list of "I am SURE they NEVER fly like THAT!"s:

1. Pitot tube iced over - and no heater working to fix that immediately. Hello! Every little Cessna with a ceiling of 16,000 feet has that feature, and its operation is part of the routine pre-flight check.
2. Backup speed sensor non-existent- or what happened to it?
3. No GPS (differential or otherwise) because it would have cost the airline too much - remember that this is for an airliner that flies over the remote Atlantic out of radar reach, for hours. At least, the pilots should have had one good GPS between the 3 of them, or borrowed one from a passenger.
4. No radio communications ("trouble all night"). No emergency channel? How were the sensors so conveniently sending messages to Air France HQ for maintenance then?
5. Complete electrical system failure occurred. If it occurred before aircraft breakup, Why? No backup generators? Weren't the engines not turning?

OK, let's look at pre-flight routine:
6. No awareness of a huge storm in the flight path (hello! did it spring up THAT suddenly - just an hour or two after takeoff and 700 miles offshore, and if so why was there no precaution to warn of such storms? Is there no on-board radar that can detect huge clouds up ahead at 39000 feet, which can only be because of very very strong storms?)
7. What happened to the Weather Briefing before the flight? What happened to Satellite warning of such storms?
8. Usually the Weather Briefing contains a good warning about temperature and humidity and winds at altitude, so it didn't occur to these pilots that these were icing conditions and they should check the Pitot Tube heater? If they said: "Aha! Storm, what storm, we fly straight through it! Then they would surely have thought about icing and Pitot Heaters and radios and radar.
9. Captain was peacefully napping through such conditions when the plane was being shaken all over the place?

The above simply don't make sense, unless Hawai Frogistan operations are run by baboons. So the other alternative has to come to the top:

The explosive decompression was the first thing that happened, it happened totally without any warning, and it either took out all the communications and most of the controls, or it killed/incapacitated the cockpit crew instantly.

Ok, let's consider that. If they have found no sign of fire or explosives, and we can rule out Shoe Bombers (no sign of fire or explosive residue on bodies, but would there be if they haven't found the mid-section and the bodies were in the water for 2 weeks?) and Pakis shooting through the cockpit window and causing decompression (why was there no hijack code SOS?) then the aircraft hit something at 39000 feet. If no other plane or high-altitude balloon is reported missing (and small craft don't reach 39000 feet unless it's suicidal gliders, and those don't fly 700 miles out from land at night), then it was something coming DOWN from above - most likely a component of a spacecraft, or a rocket booster that had just sent a craft into orbit. So it would be good to look at the launch schedule from the French Guyana Ariane site. That would explain the official French silence and the rush to claim that there was no aircraft breakup until it hit the water.

I am dissing the "pilot exceeded design load" claims precisely because they are preposterous, and they conveniently brush off questions by blaming the dead, not because I believe that EADS designed so poorly (though they can't be faulted for not trying to convince me, given the other reports of Airbus design). Of course the Long Island crash should have led to a grounding of all Airbuses until that fin attachment was beefed up by a factor of 4, as I argued based on the peak loads. It should be designed so that the rudder can fall off, maybe, but not the fin.

[vina]

It only becomes unstable if the horizontal tail breaks off - but that may indeed happen if they go into a desperate dive

Cube saar. While that is true for pitch stability, if the tail fin breaks off clean like what happened off LI, the yaw stability goes out of the window!. It will be extremely difficult to fly it in a straight line or any non random path. I doubt differential thrust will cut it. You can possibly do it if you lose the rudder, but the vertical tail stays. The plane is still stable in yaw. However if you lose the vertical fin, I seriously doubt that anyone can humanly manipulate the throttles and jet engines have such fine grained throttle response to be able to fly the plane Flying such a plane through even a half way decent cross wind will be ultra tricky, and if you are flying it through a storm like in Brazil, good luck!.

I think the sequence of events in the Brazil incident started with the FCS shutting down /degrading (there were messages to that effect werent there) and then the chain of events cascading from there (starting with tail fin ripping out whole).

[enqyoob]

vina:
1. A fully loaded airliner not long after takeoff, will have a high dihedral, hey?
2. Also, these Airbuses have large wingtip winglets, don't they? ok, the winglets may be too close to the C.G. to any good for yaw, but see this design. (Actually you can see the dihedral there too). I would be surprised if the plane is still terribly unstable in yaw with all these vertical (or projected vertical) surfaces plus
3. the airplane fuselage itself, and
4. the very high yaw inertia of the engines sitting far out on the wings,
but I don't know for sure.

Isn't the vertical tail sized to allow yaw stability in the one-engine failure? If it were not for that, the vertical tail could be a lot smaller, IIRC. Storm conditions will cause a lot of yaw/roll fluctuations, but I doubt that it will be totally unstable (but I am not sure).

It comes back to this - if what you suspect is the case, they should ground these planes NOW. You are basically saying that the FCS on very new Airbus airliners can fail suddenly, in a way that leads straight to catastrophy in a way that two expert pilots just an hour and a half into a flight can do nothing to recover, and not even have time to hit the MayDay button.

[SriKumar]

Some pictures of the recovered tail+ rudder. How it looks when intact (model to scale, I suspect):
http://www.brazmodels.com/Airbus/A330-2 ... 20post.JPG

Air France 447 tail during recovery:
http://www.abc.net.au/reslib/200906/r382502_1783134.jpg

http://www.cctv.com/program/worldwidewa ... 4147_r.jpg
Above is a grainy picture of the tail with rudder, but one thing does stand out. There is more damage to the base of the rudder than the tail itself. The rudder base is a free/moving surface and should not see any damage, unless it hit something (water, aircraft debris or something else). Clearly, a fair portion of the bottom end of the rudder has broken off.

This BBC link shows a very clear video of the base of the tail and rudder.
http://news.bbc.co.uk/2/hi/americas/8099940.stm

From 00:20 to 00:23 secs shows a close-up of the rudder and tail.


The AA 587 flight NTSB investigation pictures are here. The tail looks different and much thicker at the base. The failures seem to be different but it is difficult to make out.

http://www.ntsb.gov/events/2001/AA587/tailcomp.htm


N^3: Consider a plane from the side-view and assume a cross-wind is blowing from the side, at 90 degrees to flight vector. If the total surface area of an intact aircraft is such that it is in equilibrium- with the tail in place, then that equilibrium would be lost if the tail falls off..... since the area presented to the side of an aircraft, i.e. to the cross-wind, will be less behind the aircraft C.G. compared to the area front of the C.G. In this situation, any cross-wind should cause a yaw after loosing surface area, is my (pure) guess. If this is correct, in a storm, that would lead to a rapid loss of yaw control.

[vera_k]

Airbus could be asked to ground all long-range airliners

The fate of Flight 447 would probably have remained an eternal mystery had the aircraft not automatically transmitted data back to the Air France maintenance base.

In the final four minutes, they told a story that was familiar to the airline. Ice particles or water had blocked the three pitot tubes. This upset the air data computers which in turn caused the automatic pilot to disconnect. The pilots would have had to fly manually in near-impossible conditions.

[enqyoob]

This iced Pitot Tube business is really becoming stranger than most UFO stories. I tell you, it is bogus. Airbus aircraft fly under icing conditions routinely - remember that at La Paris in winter, ice and snow are routine, and at most times of the year, icing is possible at higher altitudes over most of the planet. Every plane has a probe heater for precisely that reason.

SURELY, flight control software for an airliner is not written to "disengage" just because one Pitot tube encountered ice, or an insect got stuck in the tube? Surely some airline engineer or pilot would have asked this question long ago, even if all the Oracle Operators blindly followed such stupid directions?

Also, the idea that at 39000 feet, a modern airliner was "impossible to fly" manually, just because there is a storm outside, is preposterous. No one becomes an airline pilot ( I HOPE!) unless they can deal with total whiteout / blizzard conditions outside without panicking. Even newbies who can barely solo under VFR will have have been trained how to react to that, let alone people with Instrument Ratings. If the FCS disengaged and the speed made no sense, the pilots would have immediately put on full power and started climbing as fast as they could to get above the storm, and they would have succeeded in short order. There must have been some radio working, and they would use radio beacons from somewhere to figure out their speed. And, Srikumar, At 580 mph, it takes a gust of 580 mph to give even a 45 degree angle, let alone a 90 degree angle. Nothing like that ever happens in the atmosphere of Earth.

Why is the French government willing to have the whole EADS company go under (quite probable if all Airbus airliners are grounded, worldwide, for such an asinine error), just to cover up the real reason?

[enqyoob]

It IS getting that bad, apparently: From the link posted above:

It is believed that the accident bureau will report that stormy weather was a factor but faulty speed data and electronics were the main problem in the disaster that killed 228 people.

The European Aviation Safety Agency (EASA) is likely to be asked why it had never taken action to remedy trouble that was well known with the Airbus 330 and 340 series. Nearly 1,000 of the aircraft are flying and until AF447, no passenger had been killed in one.

“EASA has a legal and moral obligation to get to the bottom of this problem now. If there is a defective system and the aircraft is unsafe then it should be grounded,” said James Healy-Pratt of Stewarts Law in London. The firm, which specialises in aviation, is representing the families of 20 of the victims of flight 447.

Only 11 bodies of the 50 recovered from the Atlantic have been identified. They include Captain Marc Dubois, 58, who is believed to have been resting when his two co-pilots lost control ....

Suspicion over the air data systems on the Airbus 330 and 340 series has increased after the disclosure that the aircraft had experienced 36 episodes similar to the one that brought Flight 447 down as it flew from Rio de Janeiro to Paris.

Airbus first reported problems with the speed sensors — known as pitot tubes — in 1994, it emerged this week. The company advised remedies, but no mandatory action was taken.

Last weekend, the US National Transportation Safety Board, began looking into two incidents in which Airbus A330s flying from the US suffered critical episodes apparently similar to that of AF447.

This raises the prospect of a possible US order on modifications to the Airbus.

The first US incident occurred on May 21 when a TAM Airlines flight from Miami to Sao Paulo, Brazil, lost primary speed and altitude information while in cruise flight. The other was on a Northwest Airlines flight, on June 23, from Hong Kong to Tokyo.

Accounts on the internet {Hello... can we find this?} from the pilots report a desperate struggle to keep the jet in the air.

The fate of Flight 447 would probably have remained an eternal mystery had the aircraft not automatically transmitted data back to the Air France maintenance base.

In the final four minutes, they told a story that was familiar to the airline. Ice particles or water had blocked the three pitot tubes. {NO HEATERS?} This upset the air data computers which in turn caused the automatic pilot to disconnect. The pilots would have had to fly manually in near-impossible conditions.

{I maintain that this is bogus. You don't need to see the airspeed, you just need to see other stuff like Artificial Horizon to know which way is up, and if you also have the altimeter with rate of climb/descent showing, then it's all you need. The speed is automatically computed accurately enough in your head if you know approximate altitude and the thrust setting of the engines, and you can tell from the vibrations whether you are pushing any limits or getting close to stall. So this still does not make sense.

But... WHY THE DECOMPRESSION? They are still silent on that one. Let's see tomorrow.}

[enqyoob]

Apparently the decompression was one of the final messages.

The last verbal contact with the plane came at 1.33am GMT when the flight deck reported that it was 350 miles off the north east coast of Brazil, at an altitude of 35,000ft and flying at 537mph. It would soon be entering Senegalese-controlled airspace.

At 1.33am GMT, someone on the flight deck sent an electronic message saying that AF 447 was flying into a storm.

Then, in a four-minute period from 2.10am GMT, 24 automatic electronic messages — known as ACARS — were sent from the plane’s computer to its maintenance facility at Le Bourget in France.
(So there was some form of radio contact possible - i.e., atmospheric conditions did not prevent that).

Five reported systemic failures, while the other 19 were warnings. Together, in such a short space of time — 14 were apparently despatched simultaneously — they spelt out sudden catastrophe.

Among the first ACARS was a signal that the auto-pilot had disengaged. This appeared on the Le Bourget computer screen as ‘221002006AUTO FLT AP OFF’.

One of the final messages was a ‘cabin vertical speed warning’, which suggested that cabin pressure had been lost, probably as the plane broke up and plunged towards the Atlantic.

According to reports, the first autopsies to be carried out on recovered victims suggest that they had fallen from the plane at altitude {consistent with breakup or being sucked out by decompression}, rather than being trapped onboard as it crashed.

The fact that bodies have been found in two tranches, 50 miles apart, supports the theory that the plane disintegrated high above the ocean, scattering debris and passengers as it fell.

Recovered crew seats were also folded — suggesting the crew were moving around the cabin at the time of the crash, which in turn suggests that there was no time for emergency procedures. There is no evidence of fire or explosion. {This tends to blow out the "storm" and "turbulence" theories - if there was sustained turbulence for a couple of minutes, the cabin crew would have strapped themselves down in their seats. Given the 1:33AM message about flying into the storm, this sounds extremely suspicious - it sounds like the plane had FINISHED TRANSITING THE STORM!}

Two factors remain central to the possible crash causes. The first is the possibility of poor weather. The second is that the plane’s airspeed indication equipment, known as Pitot tubes, could have been faulty.

In meteorological terms, the area in which AF 447 was lost is an ‘intertropical convergence zone’. This is where two trade wind systems meet, forcing air up into the atmosphere in icy gusts of up to 100mph.

Analysis of the flightpath weather at the time of the disappearance suggests there were cumulonimbus clouds towering almost to 60,000ft, with plenty of turbulence and
thunderstorm activity for about 75 miles, or 12 minutes of flight time.

Another phenomenon known as ‘wind shear’ must also be considered. The term describes sudden bursts of intense windborn energy, almost like a physical blow to an aircraft, which could cause sudden loss of control or significant damage.

And yet there is no evidence that the meteorological conditions in the area were any worse than had been previously encountered by other aircraft.

[vina]

vina:
1. A fully loaded airliner not long after takeoff, will have a high dihedral, hey?
2. Also, these Airbuses have large wingtip winglets, don't they? ok, the winglets may be too close to the C.G. to any good for yaw, but see this design. (Actually you can see the dihedral there too). I would be surprised if the plane is still terribly unstable in yaw with all these vertical (or projected vertical) surfaces plus
3. the airplane fuselage itself, and
4. the very high yaw inertia of the engines sitting far out on the wings,
but I don't know for sure.

Isn't the vertical tail sized to allow yaw stability in the one-engine failure? If it were not for that, the vertical tail could be a lot smaller, IIRC. Storm conditions will cause a lot of yaw/roll fluctuations, but I doubt that it will be totally unstable (but I am not sure)

Cube saar. Dihedral /Anhedral and wing sweep have effect on ROLL stability. Sweep back increases roll stability, so for low winged aeroplanes, a small positive dihedral is given to bring it back to neutral stability.

What you could use in case of rudder failure is the wing spoilers, they will create differential drag over the wing (with some roll of course) and you could turn the plane.

Yes, the reason why you need a large tail plane is that there is more area in the front , while the rear has much less area and is more rounded as well.In a cross wind, the tail of the plane is not "anchored" and tends to wander. So you need a flat plat (aka vertical tail), that will shed tip vortices (and increase resistance /damping sideways to any movement.. the Kutta condition for singularity at the edge of the vertical tail). Lose the tail and the plane's musharraf is not seated anymore and tends to wander all over the place, like it got whacked.

[negi]

From the link ; Analysis of the flightpath weather at the time of the disappearance suggests there were cumulonimbus clouds towering almost to 60,000ft, with plenty of turbulence and thunderstorm activity for about 75 miles, or 12 minutes of flight time.

60kfeet sounds like in the class of 'Cumulonimbus incus ' ,which is very much capable of forming a 'supercell' i.e. result into a thunderstorm . Having said that I have no idea as to whether a 'wind shear' can actually rip apart an entire 'tail assembly' of an Airbus 320 series and above.

Problem is when it comes to thunderstorms or other natural phenomenon we can only guess as to how severe the conditions at the ground zero might be ; now whether a civilian aircraft is designed to withstand say 'xyz' level of thunderstorm is for the concerned fraternity to answer.

However I do agree that in this age of real time access to the meteorological data the ill fated flight should have been warned and asked to take necessary action.From my personal experience International flights I clearly remember the Captain does inform the passengers in advance in case he forsee's a turbulence ahead ; I am sure that given the huge doppler signature of a thunderstorm brewing in the vicinity he/she would come to know of it in advance (at least the ground based ATC must be updating the aircraft ) and AC could be re-routed as required.

[negi]

Btw it is getting scary, N^3 saar is right....check out this guy's blog he has listed all the Airbus 3XX series crashes and guess what the sheared vertical stabilizer is the common cause.

The World According To Bob

[vina]

btw it is getting scary, N^3 saar is right....check out this guy's blog he has listed all the Airbus 3XX series crashes and guess what the sheared vertical stabilizer is the common cause.

The World According To Bob

EGAD!. That guy has hit the lulu right on the button!. The Secret to Airbus success was always this. All it's twin aisle airliners (A300, 310,330 and 340) have the exact same cabin cross section. That manufacturing "synergy" (sorry for YumBeeYea speak) gave them massive economies of scale ( the diff between the A330 and A340 is 340 has 4 engines, and longer range and usually higher MTOW, that is all, but structurally largely same and A330 & 340's cabin is exact same as 300/310 , just extended, with newer wings and TFTA FBW). The idea is by varying the length of the fuselage and putting on different kind of wings, they can have a single family of aircraft that can cater to different markets (short haul, medium haul and long haul)!. Add to that the FBW controls, where the handling across Airbus family is made similar, so that a pilot can be easily qualified across A320, 330, 340 and even 380, rather seemlessly, giving huge operational flexibility for the airline in rostering and staffing pilots and not having dedicated pool of pilots trained exclusively to one single aircraft!.

All this would have not been possible without FBW. Very impressive Karporate Stratejee onree. Airbus sure has some extremely good YumBeeYeas and Corp Planners in the product planning depts and very YumBeeYea tainted Chankian Yingineers onree. The down side, is any bug across any single product is carried across to it's entire portfolio. It is like a wall street black swan (like all good YumBeeYea designs onree no ? )

God save Airbus if the structural design of the tail fin is carried across to its other "family" aircraft, namely A330 and A340. The yellow matter will hit the fan and massive losses to airlines if they have to ground the fleet. And if they have similar design "pill-o-soppy" on the A320 as well in terms of tail fin design (dunno, doesn't seem so, coz no instances of A320 tail separating in all these years), the yellow matter will hit the stratosphere.

[Dileep]

A380....... The testing of the landing gear was shown on discovery. The whole thing was supposed to drop down by gravity, but it failed the test. The smart guys applied some grease on the rubbing surface and it finally came down.

As a design approach, this is probably not a bad idea. In fact, it might be seen as a good idea, because you are letting nature do the job. If there is any equipment failure, then the natural tendency of the landing gear is to be in down position- which is safer than it being stuck and in an 'up' position. Of course, to achieve redundancy, one should have a separate (motorized) way of deploying landing gear - as failsafe. To rely 100% on just grease to release landing gear sounds odd to me.

The landing gear is expected to fall down and lock itself under gravity. That includes pushing open the doors. The doors are then closed by hydraulics. There is also one actuator that drives the gear down.

The test was to verify the "gravity alone" action, in the absence of hydraulic power. The wheel assembly pushed the door open, but when it opened half way, the friction on the door element became too much, and it stopped. They fixed it by applying grease on the door assembly, so that the wheel assembly encountered less friction at the sliding element that pushed the door open.

The question is, is "grease the door surface" going to be a standard daily maintenance procedure? What will happen if the plane has to land under hydraulic failure? Would it have to land with gear up?

I am questioning l'attitude of using le grease, and even the audacity to say that on international TV.

[vina]

It only becomes unstable if the horizontal tail breaks off

Ah , mon ami. I am not sure. With all the FBW, I think l'Airbus compaignee has done very smart things indeed. One way of reducing drag is to reduce stability margin (not really unstable mind you, but reduced stability margin than normal) . You reduce the size of the horizontal stabilizer (it needs to generate much less force and moment over the wings because of lower margin) and the main wing can be smaller, because it needs to generate that much less lift because of the smaller stabilizers in the tail. Very smart , innit ?.

Problem is FCS goes kaput (like it seems to have) in Brazil , how can un human possibly do what le computeur do ?. Would it possibly be able to fly the plane manually at all, with FCS dead?. Remember, cases where Airbus aircraft glided back after engines died etc dont count. The FCS was still active with emergency power . Question is can the aircraft fly safely with FCS out ?.

Kweschun to les Pilots dans cette forume . Il faut possible ? Is it possible ?. Do you have sessions in the Airbus simulator where the FCS dies (not just degrades ) and you have to fly the plane ? Merci beaucoup.

[Dileep]

Another le question stupide:

Are there mechanical backups to the FBW system? I don't think so. The flimsy sidesticks doesn't look like either it can take the forces needed, or the pilot can exert it on the side. Are there linear analog backups?

The A380 use redundant sets of electrical actuators that could be powered by the aux power, or RAT. IT doesn't look like it has any manual/analog backup though.

[enqyoob]

Mon Dieu! vina, merci beaucoup for l'education, I was fast zzzzzzzzzzzzz in Prof. T's classes on Stability beyond the part where the c.g. has to be ahead of (or was it aft of?) the c.p. But pls see my point about the winglets - are they far enough from c.g. on these airliners, since the wing is swept and c.g. should be ahead of the c.p., to help the yaw stability?

Interesting point on the Les Airbooses all having les cross-sectionnes identicals. Very smart manufacturing ploy, no doubt, and should have made it pretty easy for les chimps to figure out where seat XX"A" is in relation to seat XX"B" b4 giving away veg meal for said seat "A".

But Le Fin Vertical should be different on all these, hey, except for Le Pill-o-Sophie of design? Looks like they allowed La Rive Gauche to do le Design instead of leaving it to les nerds.

negi: point about the thunderstorm: See above. If you believe that report, someone on the flight deck radioed that the plane was about to enter a storm. At 1.33AM. That's usually no more than 5 minutes ahead of the storm. They would have stopped cabin service and allowed the attendants to tie up the carts and strap themselves in their crew seats and glare contemptuously at les Passagers Miserables d'Classes Economique (sorry, shouldn't poke fun at people who had to leave us in the prime of their lives). So let's say they reached the storm boundaries no later than 1:38.

It took 12 minutes to transit the storm. That makes it 1:50 and they were out of it.

The breakup calls came at 2:12AM. By my madarssa / Rive Gauche arithmetic, that makes it TWENTY MINUTES AFTER THEY LEFT THE STORM. 20 minutes at roughly 9 miles a minute, is ~ 180 miles.

Why would the electrical failure occur 20 minutes / 180 miles after getting OUT of the storm? Did Le Fin Vertical suffer irreversible damage de fatigue composite, as Docteur shiv pointed out, and only break away 20 minutes later? Seems like there would have been some indications if this was so, and the pilots would have radioed, and started emergency procedures, woken up themselves and Le Capitaine, in which case they would all have been on high alert (able to get off a message to Le Bourget and back to Brazil, or Dakar, and everyone would have been strapped down again - unless the attendants were racing down the cabin trying to make sure everyone was secured.

From the reports, the best guess is that whatever it was, hit them when they were not expecting anything at all.

[vera_k]

Story from 2001.

United finds defect in tail of one of its Airbus jets

United mechanics found the flaw, a tiny separation in the composite material, in the area where the vertical tail fin connects to the fuselage.

But a visual test cannot detect defects within composite material.