HN 39:

It represents the component of velocity along the aircraft longitudinal axis only. I don't know if it is significant.

But intuitively it would seem to indicate the possibility of some air molecules being ingested directly down the pitot opening. Other air molecules maybe not so lucky. The 107 groundspeed is a given.

Intuitively, I've been wrong before.

(BTW, people may be mis reading the previous ILS example. The ILS beams are effectively inertially stabilized. Wind will affect aero AOA on a fixed inertial FPA, if holding a constant pitch attitude, horizontal speed & vertical speed. I understand the conditions portrayed in MM43's graphic. Start postulating winds and see what you get for the same exact geometry.)

t54: "In the info released so far there is no mention of what the PF did after that stall warning caused by his nose down inputs. It's just surmise that he stopped nose down inputs at that point."

You seem to be laboring under a misconception. The nose down simply reduced AoA. The pitot tube subsequently unblocked. That made the airspeed indication valid again and too low for the indicated AoA. That led to the stall warning.

From the end of the 2 h 10 min 05 interval:

Note the return if a valid (appearing) airspeed.

From the 2 h 10 min 51 interval:

Where were the pilots sitting?
 

Pleased end this discussion!

It makes no difference where they were sitting or who they were. All pilots in the cockpit or on the plane were qualified or they wouldn't be there.

The numbers of hours and types of acft flown is immaterial.

When a pilot is released to fly he/she is qualified. Period.

engine-eer

From a predictably solid post by lomapaseo.


"Once the actual failure rate becomes obvious in the historical useage of the system (they iced up more often than expected) then the system interaction with the ability to continue safe flight and landing needs to be examined. From my read so far, that includes the crew actions and their failure rate (to take appropriate action). I really don't know how this was taken into account (presumably it was at least considered)."



From engine-eer

"I am not questioning the current airworthiness, I understand the issue has been addressed. I don't think that the system was airworthy at the time. What I am saying is, if they were known to be junk Airbus had an obligation to have an AD issued to insure they were changed out and they didn't do it until after this crash.



I don't think it had an acronym until after 447 went in. "Unreliable Air Speed, UAS." The term gives me the willies. From the 38 logged incidents, and the asymmetrical "Recoveries" from this challenging and surprising fault, no one was ready to AD these tubes?

There was no mystery, no "Weird Fuel", the problem was patent, and challenging. People don't like surprises, eg, sudden descent, roll, and Pitch changes.

"What was that, Captain?" Oh, that was Unreliable airspeed. "How does one recover from it?". Well, it's a bit different each time, no worries".

Airbus does not write or ennable regulations, that would be the regulator's job.
If Airbus was left to write AD's, well......

It doesn't, that component is 151 kt * Cos 61 = 73 knots.

HN 39:

I stand corrected.

bearfoil/ lomapaseo and others
 

Devils advocate, historically do we know that the tubes in question (Thales?) were statistically significantly more liable to failure than the pitot tubes that were going to replace them and/or the pitots used on similar designs (e.g.777).

( Background: I've bashed around in military jets and the likes of the 747 and the 777 for over 15 k hours and never, ever had pitot icing - so what gives with the A330, is it really that fragile)?

Excuse me. Just a quick answer requested. Would anyone have any idea of the turbulence category experienced prior to the upset?

wiggy

After 38 actual episodes, the statistics are in dire need of revamp.

I am not content with the seeming "sureness" of most that Pitot ICE was in play, we'll find out. I think it is likely, but who knows?

you say:

"Devils advocate, historically do we know that the tubes in question (Thales?) were statistically significantly more liable to failure than the pitot tubes that were going to replace them and/or the pitots used on similar designs (e.g.777).

( Background: I've bashed around in military jets and the likes of the 747 and the 777 for over 15 k hours and never, ever had pitot icing - so what gives with the A330, is it really that fragile)?"



After rollbacks by TRENT7's, it took a hull loss and some very lucky people to get the Heat exchangers modded.
I am here to tell you that the "Mystery Fuel" was a propagandistic device.

So, beware of those who want us to stare like automatons at the "Certs".

All the proper people were aware of the UAS episodes, as they were of TRENT Fuel Plumbing issues. It took 228 living breathing souls to sacrifice themselves for the bottom lines of the ones who are guilty of inaction.

I may be the only person on Earth who sees it this way. I couldn't care less.

If not Pitots, then Training. Lack of follow through by Airbus on training syllabus for pilots not up to speed on the vagaries of Automatic Controls in LOC? Automatic controls in Loss of Control? Can we spell Oxymoron?

HN39, it helps to view the image in message 1340. The velocity of the plane at an angle of 45 degrees (ignoring wind) is about 151-152 knots. The fuselage is at a 61 degree angle to the flight path. Take the cosine of 61 degrees and multiply it by the velocity and you get something on the order of 73 knots. Now it's easier to entertain the notion the 132 knot velocity component across the inlet to the pitot would have it reading "somewhat" low.

The image in 1172 has a misfeature. It implies you can take the cosine of 61 degrees and multiply it by the horizontal velocity component and get something meaningful. Note that the vertical velocity rotated to the plane's reference gives a rearward velocity that subtracts from what you computed.

It's, of course, all quibbling to show that poor pitot had ample reason to read incorrectly.

You're not the only one......however living within a stone's throw of Toulouse can effect one's objectivity............

One could also presume that after 5 years of engineering school a former student is fully qualified to build a full inertial/gps/airdata based navigation system. In my experience that is not the case.

With most junior engineers they spend some time really learning portions of their trade the college never had time to teach. All junior engineers are not qualified to take on really large systems until they can tackle the smaller tasks with aplomb.

I suspect there is not much difference between engineers fresh out of college with their BS degree and pilots fresh out of pilot training. (Certainly if the 9/11 terrorists could even be accepted to a flight training program an engineering degree with some serious coverage of aviation is not needed.)

I also note that a doctor right out of college isn't ready. He spends time as a resident. Then he continues to gain skill as he ages and indulges in extra training.

If pilots don't learn as they gain experience, I am not sure I want to fly anymore. That would say something terribly frightening about the attitude and intelligence of pilots. Fortunately reading this list make it obvious pilots do gain skills with experience.

jd ee
I'm talking about when they were on the way down - not the warning at the start of the stall.
The report tells of nose down inputs and (consequent?) stall warnings sounding. Possibly the pitot readings had been invalid due to the large angle of attack - and nose-down validated them and so the stall warning sounded?

bearfoil, I have a favorite homily about foolproofing. "No matter how well you foolproof a system God will provide you a better fool." (Some idiot is going to put his hand in the toaster.) Fixing the pitots by getting better pitots is simply going to lead to the discovery of even more obscure means for the pitots to fail transiently or permanently.

So you must presume they are going to fail. Then you look at the next step in the over-all failure chain and see if you can at least partially mitigate it. You recurse as far as you can into this process.

Please don't advocate simply changing the pitot tubes as the grand solution. It is very obvious there were several serious failures in the chain of events that led AF447 with 228 people aboard to a watery grave. ALL of these items should be addressed and mitigated as much as feasible. (And I am sure that mitigation process will include some brutal cost calculations. These companies are in business to make money. We, the people, should demand these calculations be made public - for ALL airlines and aircraft companies. Then we can make our decisions about flying or not, which airline, and how often. I suspect the pilots would like to know their personal risks, too. And with the A330 line it seems that risk is uncommonly low already.)

I absolutely concur with that statement.

IF Airbus, and/or, the regulator, and/or THALES knew... that the pitots were not performing to specs... due diligence would require them to cause all the aircraft so equipped, to be declared un-airworthy. ....as that is the definition of airworthiness: "meets the standards".

Greybeard, #1337

Ok, dropped myself right into it there :-), but not enough data to do
it. Someone else mentions later a doc that describes what's available in
the various laws, but not enough info on the conditions or inputs, that
lead to them.

Will keep digging...

quoth bearfoil, "After 38 actual episodes, the statistics are in dire need of revamp."

Just what ARE the statistics you cite? The probability of a probe icing incident at altitude is how many per million flights? Is it something to panic about or is it something to fix when a fix appears? Is it going to make flying measurably safer?

Give us the numbers to go with your sense of urgency, please.

AVLNative, #1339

That looks pretty good, but still not enough info on how it gets to each law.

Perhaps I should google "Flight Control Logic", or similar http://images.ibsrv.net/ibsrv/res/sr...s/confused.gif...

It is not known if similar events (simultaneous multiple pitot icing) ever happened on other than recent Airbus types. These incidents are not always reported by operators but perhaps someone started compiling statistics after june 2009. Yet the probes used by other manufacturers cannot be so different and were designed under the same certification requirements.

Could it be that this problem has more to do with the way they are installed than with the probes themselves (e.g. typical position on the fuselage)?

and probably the best comment and question so far.

very unusual...as if the pitot heaters go faulty for some reason

DJ77

I think UAS was tracked well before 447 went in.

In the perhaps futile effort to get anyone to entertain other than "ICED PITOTS" I suggest that Unreliable airspeed does not mean "Reliable ICE"

It means that a system has become unreliable, and is being subtracted from a reliable scan, imho.

I submit that losing an engine should be orders of magnitude more dangerous than loss of a/s reads. Yet this failure has everyone's jock in a knot, and scattering to the books.

Steady. If Pitots have discrepant reads, or only one, and thus two of three samples are duff, what DJ77 intimates here is more interesting than Ice, and I submit, more likely.

It may be a wind tunnel snafu, a lack of extensive failure analysis, or simply the Bus' personality in "Severe Turbulences".

If she was behaving badly enough to elicit recovery inputs from our PF, and showed a tendency to roll ("Twitchy Ailerons"), plus an a/p trim that is thus far unknown, well, what is this obsession with ICE?

For all we know, she lost a radome into the F/O's Pitot. If one spends enough time with Vasquez' product, ICE is unlikely.

I See It That Way
 

You're not.

thanks

From the outset, The principals were playing an immature game of "He did it".

One needn't be fluent in French to assimilate all the bs from those who we looked to for info. Airbus reissued a dog-eared "Mind how you go, Pilots". Air France started with "Our crew were perhaps unlucky with the radars" (read: incompetent). Then it was "lightnings". Then "Turbulences Forte".

ACARS was "LEAKED" boys and girls, and Monsieur leaker got no Pie.

This two year long exercise in Marketing, ass covering, and damage control hasn't affected my outlook one bit.

Kick ass, and take names.

I would step on a 777 with TRENTS tomorrow, in fact, next week I actually will. Mystery Fuel? No, it never happened. The actual problem was addressed, the TRENT got some mittens, although the bs flew for John and Jane Public, I warrant.

bearfoil wrote:
For instance ... here (IMO, released 2009, sept.)

Quite irrelevant
 

Weather radar showing a wind of 316km/h today, down here in Brazil as a cold front arrives in full force

yfrog Photo : http://yfrog.com/cabt5j Shared by cristianonoro

gums: TOGA actions by the system?

It depends on the flap lever position.
If the lever is in the zero (up) position it will command thrust only, TOGA, max thrust setting.
Should the flap lever be in “one” or more, it will command the Flight Director bar, and A/P, if engaged, to Go Around. Pitch channel will go to Speed Reference System.
As you know, above a certain altitude, climb, MCT and TOGA are the same, as far as EPR or N1 are concerned.

It is known, and the answer is that yes it does happen on other types and with other pitot types on the buses. It probably isn't always reported, but when it is, the reports are there to find. Certification requirements might vary - in the sense that Airbus is known to require wider range of operating environment testing than the regulations, and other mfrs may well do the same, but not exactly the same...

Could be, but there are many other variables to eliminate, and also the issue that on the same airframe, and same mount points, other pitot tubes have a much lower failure rate. Maybe, for whatever reason, the "bad" thales model tended to end up on 330s.

Bear,

Your post:
You are not obviously an engineer and IMHO, you are over the top here. First, Thales does not make junk, neither does Goodrich. Fact is, pitot tubes do ice when encountering abnormal amounts of ice crystals, ice crystals+super cooled water, or supercooled water. This leads to the dreaded observed speed, either high or low. To claim that Thales makes junk, e.g. have a bunch of stupid engineers working there, while Goodrich makes the 100% perfect product is absolutely ludicrous. You should think about how many aircraft, Boeing, Airbus, MD, etc., are flying at this moment. They basically all fly a combination of either Thales or Goodrich pitot tubes. What you think you know, you don't know. That is, a complete story on pitot tube icing, unreliable air speeds across all operators, all makes of tubes, and all types of high flying commercial aircraft. It would seem that Thales pitot tubes on the A-330/340 aircraft do not perform as good when encountering ice crystals at high altitudes compared to Goodrich pitot tubes, but not by much. Goodrich tubes also ice over on A-330/A-340 and Boeings and other aircraft, why? It is because the design as being 99.99% foolproof only is true for those conditions that are, in reality, measureable and tested against. Both Thales and Goodrich tube met this criteria. Perhaps Airbus aircraft are more susceptible to pitot tube icing than Boeing or others, but that can only be supported by actual data of the entire flying base that isn't apparent at the moment. What is not measureable, is pitot tube behavior at high altitudes, high mach numbers flying through ice crystals, ice crystals+supercooled water or supercooled water. Until such time someone develops a test cell to create an air speed of mach 0.83-0.86, identifies the geometric makeup and size of ice crystals at 30K-40K altitudes along with the ability to inject supercooled water into the equation, we will not have the "eutopia" you seemingly are looking for in terms of pitot tube 99.99% reliability.

Face the facts, other aircraft have had erroneous airspeeds occur as the result of iced pitot tubes and they recovered and went on. The question for AF447 is why did they not recover and go on, don'tcha think?

Also, don't relate it to the BA Trent/777 incident. That is like comparing apples to pumpkins.

I am an engineer and engineers in the aerospace business do not develop "junk" as you suggest as in the case with Thales. Your just P***ing into the wind.

TurbineD

I am surprised. I know you are an engineer, so I am surprised. What I call the Thales is irrelevant, and for purposes of pragmatic discussion, the Pitots fit to this a/c were in fact junk. Insufficient performance? Eccentric behaviour in some frequently encountered flight envelopes that crashed autoflight in commercial carriage? That is somehow excusable? A legacy carrier is faced with a mutiny when critical personnel refuse to fly with it attached to their a/c?

I am over the top? A very low Top, I would say. At no time have I advocated for a competitor of Thales, ever, nor would I. The salient discussion involves equipment that could not perform that may have directly caused the deaths of many people?

Now this may not be true, and the marketplace is a brutal arena where rumor can kill a product. However, the shortcomings of this device were known, PATENT, and disregarded.

BA038 is precisely the example I wish to portray. It frames the nonsense involved in the drama of manicuring a platform for continued suitability (and profitability) in the market.

you said:

"...Until such time someone develops a test cell to create an air speed of mach 0.83-0.86, identifies the geometric makeup and size of ice crystals at 30K-40K altitudes along with the ability to inject supercooled water into the equation, we will not have the "eutopia" you seemingly are looking for in terms of pitot tube 99.99% reliability..." This is exactly what Boeing and Rolls did in Renton re: BA038. Apples and Pumpkins?

Air France R&Red the Thales, and the pilots kept flying. I vote with the Pilots, here; the engineers lost their voice?

While we're at it, let's look at the Laws between Normal and Direct. They are all some step children of Normal, and require pilots to adopt a computer like mode of problem solving, instead of trained in and immediately available skill sets. If any time until the day I die, I hear the horn, or feel the shaker, I could be fast asleep, I will push. THIS fbw does not respect the ultimate failure, it gives itself a built in excuse, "It did everything it was supposed to do".

Except butt out?

much respect, TD

"We have no valid indications"
 

Having finally caught up to real time on this thread, I would like to bring up something that occurred to me on first reading of the (English translation) of the BEA Update of 27 May, but which does not seem to have been discussed on this thread. The Update states that Assuming these statements by the pilots have been translated accurately, I believe they were seeing far more inconsistencies on their cockpit displays than just UAS. I would not expect a pilot who doubted just the validity of his airspeed or just the stall warnings to refer to the situation as "no valid indications." It seems to me that either most of the information on their PFDs was non-sensical, or by 2:12:02 their loss of situational awareness was so severe that they were no longer trusting any of the instruments even thought some may have been valid.

I wonder whether their inability to recognize the stall was the result of incorrect, absent, or non-trusted attitude information? Even though the IR portions of their ADIRUs were functioning properly, might the system-detected invalidity of air data and/or AoA information have affected the display of what should be purely-inertial information? (Later on the same page the BEA makes reference to "angle of attack, when it was valid ..." which suggests they have DFDR evidence of invalid AoA readings.)

@Gringobr, Impressive windspeed indeed... It has nothing to do with this accident though, but points at an interesting detail:

The question is not *why* the pitots froze (in a FL550 TOPS CB, *any* pitot will freeze!), it's *what* on earth they were doing there!

Several people have noted the 61° AoA of the mainplane and the 45° angle of decent, and agreed that the mainplane was therefore fully stalled.

With a nose-up up-trim of 13° the HS had an AoA of about 48° and was therefore also fully stalled, also with an angle of decent of 45°.

Although the mainplane and HS both had airfoil geometries, they seem to me to have been acting more like two drag-parachutes lowering the aircraft towards the sea.

In fact this arrangement was the answer to the problem that Burt Rutan had to solve it getting his Spaceship 1 safely back from supersonic speeds in space to low sub-sonic speeds in the lower atmosphere.

http://pickyperkins.home.infionline.net/spaceship-1.jpg

Spaceship 1 was a variable geometry air/spacecraft in which the tail could be trimmed to a nose-up of about 45°, which was enough to guarantee that both the mainplane and the tail would be fully stalled and act as drag-parachutes, bringing the aircraft back to a low altitude at a safe speed, without any other pilot action.

Once at a safe altitude Spaceship 1 could be trimmed back to normal, and safely transitioned into a glide back to the ground.

Gums Post #771 5th May 2011, 23:45 contains a description of a deep stall in an F-16:


That sounds to me as quiet as a parachute drop.

I wonder if that is what it seemed like on AF447?

Maybe a Spaceship 1 pilot (or passenger) could tell us on this thread what a Spaceship 1 re-entry feels like?

Je ne comprends rien.
 

In addition to "We have no valid indications", a couple articles I saw say that the last thing one of the pilots said near the end of the sequence was, "Je ne comprends rien" which means "I don't understand anything."


When automation kicks out (essentially fails) because of conditions, at the least what is left should benefit the pilots dealing with the situation and not confuse it further. What I'm saying is, it seems that some of the bells and whistles sounding once auto pilot kicks out, are remnants from earlier development (older systems) which are a residue which need to be reconsidered, not from the point of view of each individual signal, but the over all effect and usefulness at extreme moments.
Can't there be a redesign of support for extreme moments?

As DozyWannabe said, "The fact is that when you have pitot/static failure, all bets are off when it comes to warnings/indications and the crew must concentrate extremely hard to work out what's going on."

PP not even spaceship1 uses this configuration to create a auto-stable decent, a lot of free flown modells uses this as save thermal-brake since a long time
http://img.webme.com/pic/f/flugmodel...h/dsc_6584.jpg(1967)

released with a glimm-rope or a smal timer the horizontal stabilisator moved up after some minutes, and the following flight path is very stable with not to much downspeed,
the model sinks faster than the updraft thermik may be and landed without high-speed-chrash on earth........

http://t3.gstatic.com/images?q=tbn:A...kLXWwD5RbhZOkQ

if a trim +13deg for an a330 seems very stable for 45° angle of decent....

can it be that today some pilot did not know (learn) the trim value for a stable glide with 3° or 4° angle of decent? is the understanding of the aerodynamic mechanism of an auto-stable flow (glide) no longer notable fore every pilot?

trim, position of CG.....is today every basic thing out of mind?



every pilot has to build and flow free flow models before he learn to control computers

Still a very interesting thread over here !

I couldn't find the info in the A330 FCOM but maybe some of you have the answer:

It seems that the PF struggled with lateral stability issues.

In normal law operation, not only the ailerons but spoilers except #1 might be extended depending on air-speed to increase the rate of turn.

How would the spoilers respond in alternate law when full-lateral-stick deflection is applied and speed is missing/incorrect ?

Gums, that was a very interesting publication you linked to, thanks.

This passage jumped out to me:

syseng - if you dig out the PGF Airbus accident thread you will find some good flow charts of software logic there (I think from PJ2).

I am now reeling in a state of shock to find that there are not just 2 'Alternate Law' programmes but at least 5 (Post #1311) and I am wondering how on earth a human is supposed to work out wtf is going on - or perhaps he/she isn't?

I suggest that if the 'finding' is 'pilot error' it may well be quite 'excusable'.

It seems that a number 1 priority is that AB recognise that their aircraft can stall and sort out the stall warning logic so that mere humans can see what is actually happening.

The earlier query about misleading attitude information is a good one - we have 'accepted' that because of the ACARS stream the ADIRUs were delivering correct information - but this could be wrong, of course.

Looks to me as if an Airbus pilot needs more skills and training than average.

What about A330 Mr. Joye?

Power application is NOT stall recovery
 

"This shows that increasing the thrust at the SW in order to increase the speed and hence to decrease the AOA is not the proper reaction in many cases"

Sadly both FAA and JAR approved schools are training pilots in a flawed manner by the insistence on a minimum height loss instead of getting the wings flying again. How does a glider recover from a stall?

JAR 25 / FAR25 Test Pilots always pitch to reduce AoA long before adding power to recover from stall.

Reducing the Angle of Attack (AoA)/Aircraft Attitude to unload the wing and reattach the airflow is the key BEFORE applying power once speed is about 20% above stall speed.

Most Commercial Pilots are taught to operate safely and effectively within a flight regime of up to +/- 60 deg Angle of Bank and +/- 30 deg pitch. However, the majority of Flight schools on both sides of the Atlantic seem to teach Full Power as part of a Standard Stall Recovery (SSR). The Royal Air Force's Central Flying School also teaches SSR but the emphasis is on reducing AoA to remove buffet whilst simultaneously adding power - not holding the pitch attitude as suggested. Holding the pitch attitude whilst applying full power is a Low Level Windshear/Terrain avoidance manoeuvre not a stall recovery technique! The emphasis on minimum height loss at the stall by some Flight/Simulator examiners on check rides has exacerbated the issue.

Propellor Aircraft:

The idea that this technique worked for stall recovery on 1950s piston powered aircraft is inaccurate. As Sean Roberts of the National Test Pilot's School explained at the Bombardier Safety Standdown, all aeroplanes with tractor propellors will pitch up with application of power due to propellor normal forces. This is as true for WW2 fighters as for 2011 Turbo Prop Twins.

At high AoA, the propellor slipstream is deflected downwards. By Newton's laws, the opposite reaction is the propellor normal force which causes the nose to pitch up as full power is applied. At the same time, the local angle attack of the wing immediately behind the slipstream will be very slightly reduced (increased local dynamic pressure) but the rest of the wing will stall from the wing tips inwards. Without an increase in CLmax (eg: flaps), the stalling speed will not change significantly but the effect of power will increase the pitch attitude at which the stall occurs.

Asymmetric Blade Effect:

We now have a high nose attitude senario with further buffet onset and a greater likelihood of un-demanded roll or yaw. The latter caused by a combination of one wing tip stalling before the other and asymmetric propellor blade effect. Test Pilot, Sean Roberts, uses the helicopter rotor as an example (c.f. 90 deg AoA on propellor blade). Unless you are flying a machine with counter rotating propellors, the difference between the advancing and retreating blades creates asymmetric propellor disc loading which will yaw the aeroplane (For conventional US engined aircraft, Clockwise rotation to Pilot, will yaw left). What started as a basic stall recovery is now a more serious aircraft upset made worse by the pilot applying power at high AoA.

Buffet (stall) + un-demanded roll or yaw = SPIN !

Modern Jets:

Underslung engines on A320/B737/EMB175 all pitch up with power application without automatics in play. Rear Mounted Engined aircraft like the MD80/Citation XLS/Gulfstream VI are far less susceptible to power on pitch up unless the airflow has already separated from the wing and turbulent flow is ingested into the engines creating compressor stall /rollback.

Swept wings complicate stalling matters further. The downwash effect of trailing vorticity on a swept wing is quite different to a straight one. The overall result is less downwash at the wing tips than inboard. On a tapered swept wing there can even be upwash at the wing tips. This means a swept wing will stall at the tips first leading to a nose up pitching moment as the centre of lift moves forward thus increasing the stall in a runaway manner. Better wing design (wing fences, vortex generators, slat operation, etc), and advances in Control Systems have largely overcome these issues but a forewarned pilot is a safer one.

In summary, at the first symptom of a wing stall, reduce AoA (unload) and accelerate to 1.1 Vs before applying power. Better still (prevention being better than cure) stop the stall happening in the first place by monitoring flight path (AoA, lift vector, energy management) and the automatics. Prioritise by setting appropriate aircraft AoA/attitude and Power in the unlikely (but possible) even the computers do drop out.