Air France plane missing?

[Evan]

The European Aviation Safety Agency has ordered that some Airbus jets stop using the type of speed sensor installed on the Air France aircraft that crashed in the Atlantic in May.


http://www.cbc.ca/world/story/2009/0...r-easa852.html

I'm always amazed when something gets past the bureaucracy. Acceptable-rate-of-fatality camp, you lose. The media won this one. Bravo.

[Leightman]

mfeldt: "The (secret) report now states that the problem was not due to the strong winds and careless pilots alone, but also caused by the computer having limited the rudder travel after switching to "ground mode" because a wheel had touched ground before. The limited rudder travel apparently didn't allow to stop the strong roll of the aircraft and thus caused the wing tip to touch the ground."

Evan, AF447 obviously didn't touch a wheel, so in a strict sense you are correct that the incident may be unrelated. But the fact that Airbus manuals did not foresee that particular ramification of their computer system is suggestive that AB didn't see other possibilities, especially in the event of other system components malfunctioning. (The effect of the landing gear touching ground was to EXACTLY as designed.) The cascade of warnings and apparent shutdowns of essential flight data systems on AF447 MAY all have resulted from iced pitots, but the cascade is either very broad for that one (3) sensor failure, or AB didn't think wide enough in system design.

I am thinking here in (roughly) insurance terms: how might we end up apportioning blame? X percent here, Y percent there, Z per cent somewhere else. At this point while I am ready to admit pitots cxould get a high percentage, there are other percentages at work that represent system weaknesses. Replacing pitots with better ones will bandaid the public mind but won't do anything to solve contributing factors.

No, I am not down in Airbus at all. But I am highly suspicious of overcomplexity (no matter the manufacturer) and sympathetic toward pilots placed in a situation where there's not enough time to think through things that should have been thought through long ago on the ground.

[Highkeas]

Airbus' Computers caused near-crash in March 2008 in Hamburg

An article from the German news magazine der Spiegel writes about another incident with an A320 - which might not be related to AF447 directly, but highlights the stress that Airbus' sophisticated computer control can cause pilots:

In that incident on March 1 2008, a Lufthansa A320 touched the runway with its wing tip while trying to land in a severe storm in Hamburg. The (secret) report now states that the problem was not due to the strong winds and careless pilots alone, but also caused by the computer having limited the rudder travel after switching to "ground mode" because a wheel had touched ground before. The limited rudder travel apparently didn't allow to stop the strong roll of the aircraft and thus caused the wing tip to touch the ground. Apparently it took the pilots 3 seconds to wrestle back the command from the computer and initiate a go-around. Pilots are criticizing Airbus because such a possibility is not mentioned in any handbook, and the accident report is still not publicly available.

m.

I read a comprehensive report on this a while back but can't find it again. So it was not so secret. Maybe the final report is still being prepared.

But in looking for that report I did find this document from Germany relating to pitots icing up.

http://www.bfu-web.de/cln_007/nn_226422/EN/Publications/Investigation_20Report/1998/Report__98__5X002-0__Frankfurt__A320,templateId=raw,property=publicationFile.pdf/Report_98_5X002-0_Frankfurt_A320.pdf

[EconomyClass]

Computer Related Problems

Read this in an account of the nose-gear problems on Airbus planes:

The landing gear on the nose of the A320, also known as the nose wheel, is a big, bulky system controlled by a computer. The computer gives commands to an electrical system, which in turn operates the hydraulics that move the gear up and down, moving the wheels into proper position for both landing and storage.

The problem that caused the wheel on Flight 292 to lock in the wrong position could have been caused by the electrical system, the hydraulics or some other part of the assembly, Plagens said.

I'm considering a future flight to San Francisco, and practically all flight TO there from here are on A319 or A320. So I was wondering if these planes have any ills of their own.

But the paragraphs caught my attention because they cite environmental things like the electrical system, hydraulics or unspecified other.

And I'm wondering if AF447 swooned due to something in the "other" category, even if triggered by icing on the pitot tubes. Many times lately I've read the phrase "cascading failures", so maybe if the pitot tubes had been the only problem the emergency wouldn't have been fatal.

[P3_Super_Bee]

And I'm wondering if AF447 swooned due to something in the "other" category, even if triggered by icing on the pitot tubes. Many times lately I've read the phrase "cascading failures", so maybe if the pitot tubes had been the only problem the emergency wouldn't have been fatal.

Replacing pitots with better ones will bandaid the public mind but won't do anything to solve contributing factors.

Nothing but a token maintenance effort to shut up the public and press. Anyone with half a brain would have known the "new" ba pitots wasn't a real fix... The reason for the "re-design" of the -BA was do to icing during take-off/landing phase, NOT cruise. Big waste of time and money.

But the fact that Airbus manuals did not foresee that particular ramification of their computer system is suggestive that AB didn't see other possibilities, especially in the event of other system components malfunctioning. (The effect of the landing gear touching ground was to EXACTLY as designed.) The cascade of warnings and apparent shutdowns of essential flight data systems on AF447 MAY all have resulted from iced pitots, but the cascade is either very broad for that one (3) sensor failure, or AB didn't think wide enough in system design.

No, I am not down in Airbus at all. But I am highly suspicious of overcomplexity (no matter the manufacturer) and sympathetic toward pilots placed in a situation where there's not enough time to think through things that should have been thought through long ago on the ground.

Computer/Electrical problems.... This particular aircraft, the AF447 aircraft sat on the ground for a week back in March do to Computer/Electrical Problems. Changing out a box here and there doesn't always "fix" the problem. Sometimes just masks it for a time being.

Bangalore Aviation dot com ARTICLE

[Leightman]

P3: "This particular aircraft, the AF447 aircraft sat on the ground for a week back in Marc"

Why has it taken two months for this to come out?

[Leightman]

AF447 not the one grounded

Wait, maybe not true. Two of the comments on the article P3 cited said otherwise. Here's one:

"I think you are referring the wrong post. F-GZCB was the aircraft grounded at Bangalore. F-GZCP was the aircraft that was operating AF447 between Rio and Paris."

[Drizzt]

But I am highly suspicious of overcomplexity (no matter the manufacturer) and sympathetic toward pilots placed in a situation where there's not enough time to think through things that should have been thought through long ago on the ground.

Let me thank you for these true words.
As many people I'm puzzled by this crash I still wonder and wonder how all this has come.
@@++

[BangaloreAviation]

Aircraft at Bangalore was not AF447

Computer/Electrical problems.... This particular aircraft, the AF447 aircraft sat on the ground for a week back in March do to Computer/Electrical Problems. Changing out a box here and there doesn't always "fix" the problem. Sometimes just masks it for a time being.

Bangalore Aviation dot com ARTICLE

P3, the aircraft in the picture (which I took) is F-GZCB. AF447 was F-GZCP. However this is a bit of trivia that Air France India is not happy about releasing. F-GZCP performed AF191/192 CDG-BLR-CDG before performing to Rio. The return trip was incomplete. God bless and protect the unfortunate souls.

[Evan]

The cascade of warnings and apparent shutdowns of essential flight data systems on AF447 MAY all have resulted from iced pitots, but the cascade is either very broad for that one (3) sensor failure, or AB didn't think wide enough in system design.

How could Airbus think wider in system design? If the sensors fail, the system fails and I defy you to describe a FBW system that can operate independent of airspeed data.

It only shows how both Airbus and the platoon of regulatory officials that originally certified the FBW program failed to identify the greatest point of weakness, the exposed sensors. Not enough importance was placed on their ability to outperform the elements. Not enough concern was directed towards the ramifications of sensor failure. Probes should have been overbuilt and extensively tested in both known and theoretical environments. From the research I've done, they seem to be treated as an afterthought (burr obstruction?!).

I am thinking here in (roughly) insurance terms: how might we end up apportioning blame? X percent here, Y percent there, Z per cent somewhere else. At this point while I am ready to admit pitots cxould get a high percentage, there are other percentages at work that represent system weaknesses. Replacing pitots with better ones will bandaid the public mind but won't do anything to solve contributing factors.

I disagree. I think reliable airspeed data sensors will prevent a reoccurrence of AF447. Whatever other contributing factors were involved, I believe it was the loss of air data and subsequent loss of flight systems dependent on air data that pushed this from a manageable situation to a fatal one (loss of situational awareness in the dark during a period of exceptional turbulence). Based on the information we have, going to Goodrich -HL probes will be a de-facto solution to the problem of unreliable airspeed at cruise altitude.

I am now hoping a thorough investigation is being done on the performance history of the Goodrich -HL probes. If they are as reliable as reported history indicates, then what makes them superior? That information must be shared throughout the industry, and further improvements must be continuously explored (including a dissimilar back-up design that might incorporate active protections against extreme conditions).

[Leightman]

Bangalore, thank you for that ID confirmation on GCZB.

Evan: "How could Airbus think wider in system design? If the sensors fail, the system fails and I defy you to describe a FBW system that can operate independent of airspeed data.
...Not enough concern was directed towards the ramifications of sensor failure...."

Your last phrase was the point I was making: how will the system act if this or that gizmo fails? Is the resulting situation within pilot capability? Does standard pilot training allow a sufficient measure of reserve mental space to deal with other things? What will this mean to pilots if conditions are less than perfect during this failure? Flying straight and level, waiting (hoping) for the thing to fix itself is not a cure and obviously insufficient if you are invertred at the time (hyperbole).

You and I are focusing on different things. You say reliable airspeed sensors would have solved the problem, and would for all such future instances. I won't disagree that reliable airspeed sensors would be on my short list of necessary things to take on a flight, that suspect ones should be dumped ASAP, and that good ones might have saved AF447.

But I am also saying that someday a rock-solid gizmo that had a 100% reliability record for a gazillion miles will fail and I don't want one sensor (or two) to totally befuddle the info system and cause it to shut down and leave the pilot alone in the dark. FBW may be an improvement but it requires a certain amount of perfection or it will kill people, just like imperfect airframe design or piloting. Some imperfection is to be expected and but it can't be allowed to rapidly cascade to a fatal situation. You don't want the whole info system disintegrating for the lack of a sensor (or in this case, perhaps two). A banana peel or a shower of noodles from a noodle-stand munching tornado miles away, falling from the heavens should not bring down an airliner. But apparently if one sticks a noodle or two in a couple of Airbus's three pitots, and fly at night and in turbulence, both of which there is quite a lot of on Earth, you run a much heightened risk that Airbus's FBW system will quit, or, worse yet, continue to work feeding bad info.

I am in COMPLETE agreement with you that pitot systems should incorporate dissimilar pitot types, and that a solid backup airspeed system independent of the primary display system should be present. One thing that comes to mind is that, in the case of airspeed disagreement, if the pilots simply had a switch to turn on displays of the three airspeed sensors (or this was automatic with the loss of agreement), that the pilots brain would be a better calculator of what the real airspeed was than the flight data system.

[Evan]

Bangalore, thank you for that ID confirmation on GCZB.

Evan: "How could Airbus think wider in system design? If the sensors fail, the system fails and I defy you to describe a FBW system that can operate independent of airspeed data.
...Not enough concern was directed towards the ramifications of sensor failure...."

Your last phrase was the point I was making: how will the system act if this or that gizmo fails? Is the resulting situation within pilot capability? Does standard pilot training allow a sufficient measure of reserve mental space to deal with other things? What will this mean to pilots if conditions are less than perfect during this failure? Flying straight and level, waiting (hoping) for the thing to fix itself is not a cure and obviously insufficient if you are invertred at the time (hyperbole).

You and I are focusing on different things. You say reliable airspeed sensors would have solved the problem, and would for all such future instances. I won't disagree that reliable airspeed sensors would be on my short list of necessary things to take on a flight, that suspect ones should be dumped ASAP, and that good ones might have saved AF447.

But I am also saying that someday a rock-solid gizmo that had a 100% reliability record for a gazillion miles will fail and I don't want one sensor (or two) to totally befuddle the info system and cause it to shut down and leave the pilot alone in the dark. FBW may be an improvement but it requires a certain amount of perfection or it will kill people, just like imperfect airframe design or piloting. Some imperfection is to be expected and but it can't be allowed to rapidly cascade to a fatal situation. You don't want the whole info system disintegrating for the lack of a sensor (or in this case, perhaps two). A banana peel or a shower of noodles from a noodle-stand munching tornado miles away, falling from the heavens should not bring down an airliner. But apparently if one sticks a noodle or two in a couple of Airbus's three pitots, and fly at night and in turbulence, both of which there is quite a lot of on Earth, you run a much heightened risk that Airbus's FBW system will quit, or, worse yet, continue to work feeding bad info.

I am in COMPLETE agreement with you that pitot systems should incorporate dissimilar pitot types, and that a solid backup airspeed system independent of the primary display system should be present. One thing that comes to mind is that, in the case of airspeed disagreement, if the pilots simply had a switch to turn on displays of the three airspeed sensors (or this was automatic with the loss of agreement), that the pilots brain would be a better calculator of what the real airspeed was than the flight data system.

Agreed. Three things need to be better addressed: the sensors, the system ramifications and the piloting procedures. Situational awareness needs to be maintained.

I don't know exactly how the ADIRU's for example, can serve the PRIM computer without airspeed data. Once this is lost, the automated decisions have to be stopped and provisions for manual flight must remain. Inertial guidance from the gyros can still provide the computer some reference, but without the necessary factor of airspeed, that information is of limited use. What I mean is that it would be interesting to know what aspects of autoflight systems can still be of use without airspeed data. The cascade of failures is there to prevent erratic computer decisions from interfering with the pilots at that point. Is there a more functional sequence to the cascade?

One provision I keep bringing up is the BUSS system that is currently optional on the A330/A340 (but standard on the A380). In the event of pitot failure, it replaces the speed tape with a simple red/green speed scale calculated from AOA data. The pilots therefore have a quick reference and one they can read during extreme turbulence. It seems to make so much sense. Why isn't it a standard safety item?

[EconomyClass]

Superbus: Good or bad idea

I wonder if there's anybody at all out there who looks at the total loss of an A330 with all its passengers and crew and then thinks "And airlines want to buy a plane from Airbus that carries even MORE passengers". I'm wondering how air travel will get better if they can lose even bigger planes and larger numbers of passengers. Plus, my eyes start to cross when I think of so many people jammed into one vessel. For some reason, what comes to mind is Titanic. I guess I have a visceral reaction AGAINST massive conveyances carrying 3,4,500 people. Just loading so many people gives me the creeps. Safer or not, I want to go places on 737's instead. I'd even pay more money just so that airlines don't march lockstep into a future with inevitably headlines that say "Plane lost at sea. All 500 die".

[Leightman]

We are on the same page Evan.

[HalcyonDays]

I wonder if there's anybody at all out there who looks at the total loss of an A330 with all its passengers and crew and then thinks "And airlines want to buy a plane from Airbus that carries even MORE passengers". I'm wondering how air travel will get better if they can lose even bigger planes and larger numbers of passengers. Plus, my eyes start to cross when I think of so many people jammed into one vessel. For some reason, what comes to mind is Titanic. I guess I have a visceral reaction AGAINST massive conveyances carrying 3,4,500 people. Just loading so many people gives me the creeps. Safer or not, I want to go places on 737's instead. I'd even pay more money just so that airlines don't march lockstep into a future with inevitably headlines that say "Plane lost at sea. All 500 die".

Keep up - we've already had two aviation accidents where the death toll was over 500 - the first as much as 32 years ago, the second 24 years ago. In reality, the real historical shocker was the THY DC-10 crash in 1974 where 360 or so died - that was a real paradigm shift which those who recall that crash found to be a major event.

By the way, I believe the largest number of souls on a piece of moving transportation was on the Queen Mary in WW2 : approximately 15,000 people on a trooping mission across the Atlantic. It was unaccompanied and not in the convoy system - its high speed was considered its own protection.