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Originally Posted by Lonewolf 50
Note: what has been discussed in this thread is that in some previous Unreliable Airspeed incidences, there were pitch up, but not in all.
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HN39:
I am not referring to the BEA report, but on the continuing series of threads on this crash. Some pages back, there was the A340/A330 incident where was discussed "a near miss" where one plane did a bit of a zoom climb. Also, when I went back to some of PJ2's older posts, I found something he'd dug out of another report. That is what I put in qoutes in the post where I address Takata and PJ2. EDIT: here is what caught my eye. The post was PJ2 responding to you: HN39; I was unable to locate "Appendix B". If the report has something to contribute to an understanding of the AFS especially the reconfiguration of flight laws from Nz to AlphaProt Law, I'm sure what there is in this report will be available and its relevance hopefully established. There are some primary differences in that event: For an AlphaProt Law response, the aircraft must be in Nz Law as the response (HIGH AoA and PITCH ATT) wouldn't be available in either Pitch Alternate law. As we are aware, the AD that was released on December 22, 2010 states, "However, in some cases, the autopilot orders may be inappropriate, such as possible abrupt pitch command. In order to prevent such event which may, under specific circumstances, constitute an unsafe condition, this AD requires an amendment of the Flight Manual to ensure that flight crews apply the appropriate operational procedure." The AD does not mention those "specific circumstances", nor do we know to what event(s) the characterization of "abrupt" refers, if any. Perhaps the dots are still too far apart to see viable connections but this event and the one to which I refer above concerning the UAS QRH Drill, are possible areas to focus upon along with weather. To be clear, PJ2 took the position during that element of the discussion that the aircraft was stable, (see the part of the post where he addressed takata before he addressed you). If you think I have misinterpreted this, or I am making too far of an intuitive leap, please advise. What I gathered from the 340/330 near miss was that an uncommanded pitch input was made, and the pilots got it sorted out in a few thousand feet, and returned to flying on altitude and airpseed, and arrived at destination. What made that interesting was that another aircraft saw it. As I understand it, the report was initially more concerned with the "near miss" than perhaps anomalies in flight control inputs. The other incidents discussed, which included uncommanded flight control inputs, altitude excursions, and various upsets that the pilots recovered from have been part and parcel to this discussion at various times. Air Carriebe and Qantas were two of them. If my synthesis is turning out a stew, instead of a cake, please advise. |
Lonewolf_50;
The discussion I had with PJ2 was about an A340 AIRPROX incident due to turbulence, which activated High-AoA protection. It was not an UAS incident, and it has afaik no connection to AF447. The BEA analysis of 13 UAS incidents does not contain any reference to an uncommanded pitch-up, nor does the table in app.7 . The report states: With regard to crew reactions, the following points are notable: The variations in altitude stayed within a range of more or less one thousand feet. Five cases of a voluntary descent were observed, of which one was of 3,500 feet. These descents followed a stall warning; |
Thank you, sorry for having crossed my own wires on that. :O
Appreciate your clearing that up. |
Lonewolf_50
The airprox report is summarized in this post http://www.pprune.org/tech-log/44963...ml#post6434021 and the UK AAIB report can now be found complete with appendices at Air Accidents Investigation: Airbus A330 C-GGWD and Airbus A340 TC-JDN |
Originally posted by takata ... Alerts are supposed to catch their attention only if their situation awareness is low because they are distracted by something else. |
mm43
Hi mm. I am not sure what you are saying here...... "...That will undoubtedly be the crux of the matter - the aviate, navigate and communicate chain became broken.http://images.ibsrv.net/ibsrv/res/sr...y_dog_eyes.gif" "ne comprends pas" means one thing, "ne...riens" another. This snippet, if accurate, says so much. It is a closure, a juncture of CRM. The flight is being re-set in the view of at least one pilot. I think the comment is within the boundaries of "Aviate," alone, not comms or Nav. No one would get to this point re: the mundane. Not even atrocious and frightening weather weather. The airplane is an unknown to him here, and shows a frustrated pilot partially into a situation with which he is greatly uncomfortable, and has no experience of. This moment is the initial onset of upset, or the immediate prelude. Again, if accurate, a year's worth of speculation coalesces into epiphane for all of us connected in any way with this tragedy. They are speaking to us. |
bearfoil
My oblique reference was related to matters discussed many thousands of posts ago, and I don't intend to elaborate further. |
respectfully, mm, no sir. takata's statement that you qouted is not correct, insofar as what the intention of an alert is, nor the context he claims.
The conclusion you drew from it at odds with what appears to have happened: things had boiled down to aviate alone, which became (for whatever reason) an overhelming task. Task saturation isn't a pretty sight. EDIT: never mind, I see what you were getting at. |
Well, I've been reading this for a while. It's been quite interesting, including the C vs. Ada fights and the veiled reference to flying the Skyraider.
That expert report table with the 36/43 incidents is pretty impressive, as is the note that nearly two-thirds of the events were reported after AF447 (although most of them occurred beforehand). Isn't the industry standard one catastrophic failure ever 30 or so incidents? One of the "take-aways" from this discussion could be that, regardless of whether FBW plays a role in this accident, what it does do is increase the criticality of a certain piece of equipment, and it did so based on underreported reliability data (even if the Thales AA was a particularly bad design, from this data every pitot tube should suffer from underreported failures). Or, in other terms: in-service reliability figures are scientifically worthless. The "responsibility/authority" distinction is at least superficially appealing. Another way to put it is that if a system design routinely drops a load in the operator's lap, the designers cannot expect more than 29 out of 30 operators to make the right decision. On the other side, at least 20 out of 30 operators are going to do everything they can not to be #30. And the Swiss cheese analogy has its charms too, if only because the next slice is more likely to have the same holes as the previous one than not. please carry on. |
As a result of the blocked static ports the basic flight instruments relayed false airspeed, altitude and vertical speed data. Because the failure was not in any of the instruments but rather in a common supporting system, thereby defeating redundancy, the altimeter also relayed the false altitude information to the Air Traffic Controller. Although the pilots were quite cognizant of the possibility that all of the flight instruments were providing inaccurate data, the correlation between the altitude data given by ATC and that on the altimeter likely further compounded the confusion. Also contributing to their difficulty were the numerous cockpit alarms that the computer system generated, which conflicted both with each other and with the instruments. This lack of situational awareness can be seen in the CVR transcript. The fact that the flight took place at night and over water thus not giving the pilots any visual references was also a major factor. Aeroperu 603 |
HN39, I knew I remember something about a pitchup ...
http://www.pprune.org/rumours-news/3...ml#post4966826 It was a guess by one of the posters here based on something in an A330 (not the A340 in the AIRPROX event) Another IRU fault resulting in sudden departure from controlled flight? Several months ago an A330 transiting across Australia suffered a transient electrical fault in IRU1. It caused AP1 to think the aircraft had pitched down ~40 degrees. Needless to say it pitched up in response. Fortunately they recovered and the aircraft landed safely after diverting. I wonder if this did similar, only in the opposite sense? http://images.ibsrv.net/ibsrv/res/sr...milies/eek.gif ECAM Actions. http://www.pprune.org/rumours-news/3...ml#post4967466 |
One thing I have noticed, or missed, is that with all these 'leaks' and speculations, there is no mention of why AF447 flew into the CBs, and appeared to make a last minute adjustment to their course. I wonder if that will be revealed tomorrow?
Also with all the past accidents involving pitot tube, gung-ho pilots, flying into storms, computer failures, isn't it time for manufacturers to produce aircraft and softwares that can prevent the constant repetition of these accidents? |
Originally Posted by Porker1
(Post 6475016)
- yes the pitots iced up, the flight computers gave up and passed the control to the pilots;
- yes the a/c stalled but (as you'd expect!) the crew then correctly applied the textbook approach to deal with the stall but this did not work; - yes the captain had briefly left the cockpit but was back in the cockpit for the critical part of the incident. To me the most interesting thing is not what it says, but that it appears to completely contradict the earlier leaks. If the crew did everything by the book and still ended up in irrecoverable stall, then (IMHO) it can't possibly be true that the aircraft is exonerated and the crew at fault. At least one set of leaks is therefore wrong - and always possibly both. Roll on tomorrow. |
Lonewolf_50;
If the reference is to QF72; it pitched down uncommanded approx 10 degrees (from +2.5 to - 8), then during recovery in response to pilot sidestick command 7 deg up to approx -1 degree. Regards, HN39 |
CogSim, the last line of your recognizing icing posting prompted an "Oh goodie!" from me - in a very sarcastic tone.
"Under some icing conditions, even a 3-minute exposure can substantially affect the handling of the aircraft." Riiiiight - and who knows what the handling feels like when the computer has been flying? And then the computer, where all this handling data lived as bits and bytes, flips the pilot the bird and says he has the stick. No WONDER pilots get confused when things pickle. They don't have critical data and there may be no good way to transfer that critical data to the pilot in time. If pilots are going to be expected to take over when things get tough they should be far more involved in the routine flight of the plane so they have this feel. That phrase proves this to me. {o.o} |
sensor_validation, I get the impression that one of the best improvements for a pitot would be some form of airflow measurement out of the drain hole. If either the probe or the hole ices the airflow through will diminish. With a moniker like yours that's a design challenge for you. Measure the existence of airflow without increasing the chances of the probe icing.
{^_^} |
From about two years ago, from poster snaproll3480
According to the QRH and based on a weight around 210t: (speeds are approximate) Green Dot (minimum clean speed): 245 kts Turbulence penetration speed: 260 kts Vls w/ 0.3g buffett margin: 235 kts Speeds are all indicated so no ISA deviation necessary. Thanks for the detail, HazelNuts, yet again I doff my cap. In re the pitch down versus pitch up. With the above airspeed limits in mind, how benign do you think an unexpected ten degree nose down pitch is while on IMC, and possibly in turbulent air, with those limits considered? NOTE: this is not a declaration nor an assertion that such is what happened with AF 447, but an inquiry regarding, as a pilot, your tolerance for a sudden ten degree nose down event. The closest thing like it from my own experience was a runaway nose trim event (which was a bugger, but manageable) but that was not on a FBW aircraft, so my personal points of reference are vague at best. I will refer to AMF's comments on upset response from about the time AF 447 went down, which sentiment seems to not be confined to him.
Originally Posted by AMF
The fact is, most pilots train for unusual attitude recovery where the recovery is accomplished in benign conditions with all flight controls working normally, a full panel, not to mention the engines running and outside visual reference. Many places don't even give "jet upset" training...i.e. loss of aerodynamic control at high altitude.
And a real-world jet upset, let alone sever or extreme turbulence involving all the forces, cannot be rendered or trained well in a simulator because the test pilots during certification don't even put the aircraft through those paces. Regards LW50 |
JD-EE
I get the impression that one of the best improvements for a pitot would be some form of airflow measurement out of the drain hole. Properly designed, that measurement could be done with a hot wire anemometer. Basically, if there is flow, it is likely to be a valid measurement. No flow, and the measurement is invalid. We still have the problem of what to do when the reading is invalid on multiple sensors. |
If pilots are going to be expected to take over when things get tough they should be far more involved in the routine flight of the plane so they have this feel. Anyway, enough. With the air crackling and pregnant in anticipation of the next report, let's not forget what the whole exercise is about: Finding the truth, whatever colour it may turn out to be... Regards, Chris |
"ne comprends pas" means one thing, "ne...riens" another. This snippet, if accurate, says so much. It is a closure, a juncture of CRM. The flight is being re-set in the view of at least one pilot. I think the comment is within the boundaries of "Aviate," alone, not comms or Nav. No one would get to this point re: the mundane. Not even atrocious and frightening weather weather. The airplane is an unknown to him here, and shows a frustrated pilot partially into a situation with which he is greatly uncomfortable, and has no experience of. This moment is the initial onset of upset, or the immediate prelude. Again, if accurate, a year's worth of speculation coalesces into epiphane for all of us connected in any way with this tragedy. They are speaking to us. |
> We still have the problem of what to do when the reading is invalid on multiple sensors.
Mechanically would it be possible to have 2 on a turntable, one always inside (warmer) and if the hot wire on the outer one indicated a block, the turntable rotates the outer one in. I realize this is a mechanical mess and adds all the unfavorables (cost/weight/complexity) but if it could be done, it would certainly get you a fresh ice free pitot for a little bit. |
Factual
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We still have the problem of what to do when the reading is invalid on multiple sensors. In the words of Sir Isaac Newton, If the apple doesn't fall, go shake the tree! |
JD-EE,
CogSim, the last line of your recognizing icing posting prompted an "Oh goodie!" from me - in a very sarcastic tone. "Under some icing conditions, even a 3-minute exposure can substantially affect the handling of the aircraft." |
Originally Posted by Lonewolf50
With the above airspeed limits in mind, how benign do you think an unexpected ten degree nose down pitch is while on IMC, and possibly in turbulent air, with those limits considered?
NOTE: this is not a declaration nor an assertion that such is what happened with AF 447, but an inquiry regarding, as a pilot, your tolerance for a sudden ten degree nose down event. The speeds you mention are not 'limits', but recommendations designed to minimize the risk of exceeding structural and controllability limits. Although I fully agree that unusual flight control system behaviour such as occurred in QF72 and in the A340 Airprox incident should be kept in mind, there are at present no indications that these occurrences have any relevance to AF447. |
Machinbird, "We still have the problem of what to do when the reading is invalid on multiple sensors."
At least the scope of the problem is reduced if until that report the plane was flying nominally. It's not going to accelerate or decelerate very suddenly if the attitude is kept constant, throttles kept constant, and the bad spot is simply waited out. "Don't just do something, sit there!" wins again? |
Thinking of that last statement of mine, it may make even more sense when you dig into it. The pilots are given control of a plane the computers cannot handle. (Ran out of program memory or design knowledge base?) That would imply to me that the computer has already tried to apply "conventional wisdom and procedure" to at least some small degree. So the trick is to sit there and think of what the computer may not have seen.
Of course, that requires almost line by line understanding of the software. <sigh> |
CogSim, in other words he experienced what is known in the vernacular as a WTF event only in politer and more professional words. (And that may well indicate either upbringing or more likely the fact that he was not panicked yet. He was still working logically.)
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From BEA's Interim #2:
-40 °C is the commonly accepted value below which no more supercooled water exists and thus the risk of ice accretion on the aircraft airframe. |
From BEA's Interim #2: Quote: -40 °C is the commonly accepted value below which no more supercooled water exists and thus the risk of ice accretion on the aircraft airframe. A number of recent posts fail to appreciate the difference between the icing conditions that produce ice accretions on (unprotected) parts of the airframe and the conditions that are suspected to cause blockage of heated pitots. |
Of course, if we now take it as a given that a mostly uncontrolled and rapid descent form FL350 to sea level occurred, there is almost certainly going to be one of the flight crew offering an expletive or two, indeed, 'I don't get it' (none of this adds up) would be expected earlier rather than later.
Let us brace ourselves if much at all of the CVR is published... this is going to be heartbreaking of course :sad: It is that subsequent (apparent) instability and lack of response, not the sudden pitch up itself, that is worrying me. And let us remember that adjacent to highly unstable air masses, substantial increments of airspeed can be added or subtracted over very short timespans. |
I'm trying to think of KISS aircraft attitude instruments that would not be affected by electrical (hardware or software) failures, physical properties of aircraft ambient air, initial calibration concerns and attention distraction by synthesized sounds. Spirit suspended turn-and-bank indicators and magnetic compasses come to mind. Pitch and roll only dependent on gravity and yaw only dependent on the earth's magnetic field. Unfortunately you can't patent any of that so there's no money to be made pursuing development and lawyers still can't find a loophole in the law of gravity to bill for.
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Originally Posted by CoqSim
Is it possible to have conditions that on the one hand overcome pitot heat to clog them up, but OTOH, don't accrete ice anywhere else?
I sometimes cannot help thinking, doesn't anybody posting ideas on on this thread about the 'stupidity' of airplane and equipment manufacturers, and regulators, think about the difficulty of finding out what happens. How on earth do you establish in these incidents what ice is accreted elsewhere, what happens inside the pitot tube, why it happens, while so many airplanes fly through the same clouds of ice particles every day without incident, why one type of pitot probe is more resistant (but still not immune) than others? |
Originally Posted by Svarin
(Post 6474359)
Then why the aircraft that can be flown by "concierges" ? If not to recruit, train, pay, and respect pilots like "concierges" ? Remember the late eighties. Refusing to see an intent there is naive.
Originally Posted by rudderrudderrat
(Post 6473856)
I wish AI had fitted a big red switch to turn off the Flight Control computers and place it into Direct Law. I am led to believe that B777 has one fitted?
I've already said three times on this thread that the Airbus FBW design had input from pilots central to the requirements-gathering stage (and have provided supporting evidence from my late professor that this was indeed the case). Some pilots may resent the technological intrusion, and this is something that has been true going all the way back to the first hydro-mechanical stick-pusher devices (hat-tip D.P. Davies). This is not something that has its roots in the move to FBW.
Originally Posted by Svarin
(Post 6474244)
What is specific to FBW aircraft is the changing of Flight Controls Computers, through successive software versions. This is done very discreetly. Some mistakes get corrected before they have a chance to do damage. Some are corrected after a fact (or not). But more than that, the very multiplicity of successive versions of such a critically critical piece of software and equipment will introduce a whole new set of potential problems. Specialists call these Byzantine faults, in reference to an ancient war involving traitorous generals.
Originally Posted by Svarin
(Post 6474391)
IBut I will not accept to play scapegoat for a system that claims to be safer than I am when it is easy, and that evades responsibility when things go wrong.
In all seriousness - as a software engineer, albeit of a grade significantly lower than those who specified and built the systems we're talking about, I've patiently tried to explain exactly why all the old rubbish about concierges, pilotless airliners, and preventing pilots from doing what is necessary to rescue the aircraft is - indeed - rubbish, and I've tried to explain that the engineering disciplines behind the systems that are there, which are designed to assist the pilots - and nothing more - are every bit as stringent, if not more so, than the mechanical and hydraulic engineering disciplines that made the previous generation of jet aircraft possible. But it feels like I'm talking to a brick wall in this case, because none of the posters who keep pushing the software failure theory appear to be taking a blind bit of notice of what I'm saying. If I was to take the same attitude against the pilots on here, it would be considered the height of rudeness, and I'd probably be banned toute-suite. However as this is a pilot's forum I have to accept this as my lot, and I'm fine with that. As a software engineer - one who takes my discipline seriously - I'm fully aware of what can go wrong with software, and yet I'm perfectly sanguine about getting on a FBW airliner, much as I am any other. If I had to pick a bone with Airbus, I'd worry more about the continued use of Kapton wiring insulation that I ever would be about the possibility of a Byzantine software failure causing an accident. In the late '90s, I had to be sanguine about getting on 737s, despite the knowledge that the rudder hardover problem had not been satisfactorily solved. I've had to be sanguine about getting on an old 747 jumbo in the summer, despite no movement on inerting systems being fitted to the central fuel tank. I've had to get on a Fokker F-28 in foul weather, knowing that if deicing wasn't done properly we'd be in significant trouble. Hell, I've sat in an RAF Chipmunk knowing that the cables are right underneath my feet and the engine design dates from a time before my grandmother was born! I boarded these aircraft in the certain knowledge than almost none of my fellow passengers were as aware of the specific potential dangers as I was, and yet at no point did I feel the need to jump up and declare "Hey, this aircraft is known to have a major safety issue! If I were you I'd get off this 'plane and maybe sue the airline and manufacturer for ever suggesting you would be safe getting on it!". I'd have documented evidence proving that the statement was categorically true, but I wouldn't be helping anyone because the chances of such a thing happening on that particular flight were infinitessimally small. So why is it that it's considered OK to bash FBW Airbus designs on here with absolutely no evidence that software had anything to do with the accident? Why is it OK to keep rehashing ill-advised remarks made by a single Airbus employee twenty-three years ago to claim that Airbus are somehow complicit in the "dumbing-down" of pilot training, when it's clear that if and when it does happen it is clearly the fault of the airlines who abuse the presence of automation in this way? Why is it that some are quick to blame the Airbus computers for handing control back to the pilots, when this is something that has affected many airframes from many manufacturers over the years? And why is it treated as a certainty that pilots would have been able to recover from this particular pitot-static failure incident (if indeed that does turn out to be a major factor), when prior evidence suggests that pilots are no more capable of diagnosing pitot-static failures at night over water and providing the correct remedial action than the computers are (re: Birgenair, Aeroperu)? |
.. and hot-wire anemometry has been around a long time, (was playing with such in 1973), initially for turbulence (good bandwidth) and useful for boundary layer work.
I'd imagine that if hot wire (more likely hot film) techniques were up to the environment and didn't degrade, they'd be used in 'some' capacity or other (robustness/longeveity problems in i.c.engine AFMs are not unknown) KISS may well be relevant to the persistance of the pitot-static solution because it is so easy to read dynamic head (Q) directly, giving IAS without further ado |
Early warning for (entire) System Graceful Degradation
Hi,
The goal has got to be a graceful degradation of the system if pitot ice happens Very probably we could introduce a "band-aid" to alert when the "error" between the sensors "start to increase". And this may help in providing an early warning in dealing with the "product limitation" of current available sensors. I am assuming the Pitotīs are not "transformed in "altimeters", etc.":} immediately. The events are gradual, i guess. And we need testing to understand how the sensors "freeze" (temperature. and valid signal:)) This is an "analog world" with the "richness of mother nature". From an Engineering point of view i consider an absurd what we are facing. We need (the aviation industry) to do ASAP R&D on the issue. And we need "analog field" Engineers with Henri Pitot like expertise. The "bitīs engineers" need "better data" for their Redundant Systems. The system being the a/c (Systems + Crew) I think we may say the aviation industry is facing a "product limitation" (specs, cert, design, etc.) and not a "technology barrier" |
Hi,
So why is it that it's considered OK to bash FBW Airbus designs on here with absolutely no evidence that software had anything to do with the accident? If you take the time to read this primary report from the group of judiciary experts (prčs du tribunal de grande instance de Paris) .. they point responsabilities to Air France and Airbus (and some others) for many reasons but not for softwares problems. It's seem they also exonerate pilot errors so far .. This is not tabloîd blah blah ...... (this the third official document I read about AF447 .. the 2 formers were the primary reports of BEA) rapport d'expertise Rio-Paris |
What good would that do? Captain Sullenberger is universally regarded as a pilot's pilot and yet he chose to start the APU - in part to keep the protections online as a backstop if things got hairy - which is precisely what they were designed to do. If the Airbus systems were as unreliable as some on here are trying to claim, why didn't he just sod the APU and wait for the RAT to drop (which would have given him standby instruments and Direct Law)? DozyWannabe, your are in Love, but the APU should deserve a bit more consideration. Beside that, Sullenberger would have been better served by direct law in his attempt to flare as he wanted to ... |
CONF, with the utmost respect - you're sounding like a broken record. I have yet to see any assertion supporting your statement claiming the pilots were unhappy with how the aircraft responded. In fact I haven't ever seen anyone other than yourself bring it up.
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