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AF 447 Search to resume (part2)

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AF 447 Search to resume (part2)

Old 25th May 2011, 07:25
  #2341 (permalink)  
 
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The impeccable reliability of safety-critical computing has most likely lulled people into a false sense of security. Many accidents just wouldn't happen if there were a sober acknowledgment and balanced processing of the general risks associated with flight.
This is an attempt to redirect the recent negative tone of this thread.

This statement is a very good one. Yes, automation has advanced aviation safety...on the flip side it also has created a false sense of security.

That is why this is a watershed event. It seems that AF447, with what we think we know at this point, is the "perfect storm" of the "human vs. automation" argument. So the point of conversation should not be whether you would rather have HAL flying you around, or a Sky God from the past flying by the seat of his pants! The point should be how do we move beyond this discomfort and meld man and machine. My guess is it may take more man power than originally assumed...which my cause some impediments on advancement.
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Old 25th May 2011, 07:58
  #2342 (permalink)  
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'keitei' makes an interesting point in #2335 .

May we put this 'AoA/FPV' etc discussion to bed here please? You can have a 'safe' AoA with a dangerous FPV and vice versa. AoA, as those who have used it know, is a great tool for approach and landing. Trying to 'peg' a value of 'AoA' or an 'FPV' in the middle of a storm area would, I suggest, defeat most 'sky gods'. The more info you put on a display, the more 'chimes/alerts/ECAM messages you insert, the more challenging it is to sort wheat from chaff when it all turns to crock - sensory overload cuts in big time, and I'm sure happened here, and the captain (reportedly) shouting commands at the pilots could have added to the distraction (Q - what is the first 'sense' to be lost under stress?).

The message is clear, if 'old-fashioned' and not 'software driven'. Maintaining the correct pitch and power will generally get you out of trouble, despite temporary 'excursions', even momentary stalls/high-speed excursions, if the weather is really rough. Overall you should get through it. Rely on what may be badly degraded bells and whistles or excessive clever and pretty CRT displayed info and you may well not.
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Old 25th May 2011, 08:30
  #2343 (permalink)  
 
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29 Bodies recovered

Source Vesseltracker
"Since May 21, another 29 bodies have been recovered from the wreck of the crashed Air France flight from the bottom of the Atlantic by the "Ile de Sein". The ship had returned to the crash site off the Brazilian coast on May 21 coming from Senegal with a replacement crew. Meanwhile a total of 82 human remains have been recovered of the 216 passengers and 12 crew members on board the AF 447 flight."

I think that the authorities are now focusing on bodies recovering rather than the wreckages by themselves.
I'm still wondering if the cockpit has been recovered and bring to the surface.
During the last BEA press conference, Mr Bouillard briefly spoke of the cockpit recovering and it was not clear, even for him, whether it had be lifted to the surface or would be "soon". I have not recorded the footage and I don't recall exactly what he said precisely.
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Old 25th May 2011, 08:43
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...and the embarrassment continues!
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Old 25th May 2011, 08:51
  #2345 (permalink)  
 
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Originally Posted by slats11 View Post
There are two problems with unreliable airspeed:
1. The unreliable airpeed per se.
2. The bigger problem is when the system (and the pilot) does not recognise that the airspeed is unreliable - and automation then insidiously takes the aircraft closer to the edge of the flight envelope.

Although the system obviously works most of the time, there is a weakness if the system uses 3 identical tubes to detect a problem. If the problem effects all 3 equally, then it can be missed. It will be unreliable, but not recognised as unreliable. Just as three 2nd graders can't together do 6th grade math, 3 problem tubes can't reliably determine airspeed (nor even the state of unreliable airspeed).

With pitot tubes, you are using air flow through the tube to create a pressure, which you then compensate for altitude by using static sensors, and then converting this compensated pressure back into flow (or airspeed). There are a lot of links in this chain. Even worse, a problem could generate either an over-speed (eg blocked pitot drain hole) or an under-speed (blocked tube).

When it is difficult to measure something important, an alternative that is easy to measure becomes important. And so it was 200-300 years ago - flow was difficult to measure, pressure was easy, and so we calculated flow from pressure.

Maybe the time has come for us to measure flow, and thus airspeed directly. Presumably that is the principle behind the [email protected] systems currently being developed.

It may be that pitot tubes today are dinosaurs looking for a tar pit.
Pitot tube measure airspeed via dynamic pressure, this is also what the wings use to generate lift. Measuring air molecule approach speed (laser?) will still need air density from static pressure and temperature from temperature probe. Pitot tubes are simple and have well known failure modes - how long will it take to develop alternatives to the same level of maturity?

What is not clear is why these simple devices seem to have increased number of incidents in cruise - in conditions that are uncertain and do not form part of any current certification requirements. Is it subtle changes to planned flightpaths or "Climate Change". I have no doubt if a reliable test of the "alleged supercooled liquid" or my preferred explanation of "particle size distribution of micro-fine ice crystals" can be generated - pitot tube heating can be redesigned to prevent blockage - but don't hold your breath waiting to get them introduced any time soon.

The now preferred Goodrich probe has also already suffered icing, but my understanding is that it is less likely for the drain hole to block, so blockage of the ram port should give a more obviously failed low reading, for example:-

Investigation: AO-2009-065 - Unreliable airspeed indication - 710 km south of Guam, 28 October 2009, VH-EBA, Airbus A330 202

Originally Posted by keitaidenwa View Post
..
To get back to AF447, the Air France beancounters were reluctant to upgrade pitot tubes to safer ones. I have no idea what the price of the pitot upgrade was, but probably it was not cheap, since it got beancounters on their toes. Blame beancounters? Well, the other side of the coin is that Airbus/Thales was making a profit on what was essentially a safety fix...
To be fair there was (and still is) a technical debate as to whether the alternate probes are significantly better for high altitude icing. The change was not a mandatory safety requirement, there was just a logistical supply issue and biggest cost would have been taking planes out of revenue generating service for unscheduled service.
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Old 25th May 2011, 10:31
  #2346 (permalink)  
 
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Some great reading and food for thought here. I especially find myself siding with desitter. Aside from the pros and cons of automation I think that EU OPS (JAR OPS) and regulators as a whole have a part to play in the short comings of this accident. Whilst EU OPS has improved the training depts output in low end airlines, their rule-making may have had the opposite effect on the bean-counter led airlines training depts. The bean counters are constantly putting pressure on training dept heads to cut costs and slim down. The, 'we train to proficiency' (no more no less) mentality is now showing the fruits of it's labour. Personally I don't remember any really challenging training scenarios for many years now, actually since 1997. The usual LPC items have been covered and the training day is the usual rushed affair with trainers who have less and less to give, or are allowed to give. Very prescriptive, sterile packages. Very few 'old boys' that put you through the ring with scenarios that are multi dimensional. God forbid that we give our pilots multiple failures, they might fail! That would cost money and that's not an option.
It's time to train hard again, it's time the regulators got real with training, it's time that pilots with 'heavy training files' were given the extra mile, and it's time that PC took a backseat and allowed the truth to be told. A few egos may be bruised but a few lives may be saved.
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Old 25th May 2011, 11:40
  #2347 (permalink)  
 
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Razoray said "So the point of conversation should not be whether you would rather have HAL flying you around, or a Sky God from the past flying by the seat of his pants!"

That's right, and it's not. It's about over-reliance on automation in all aspects of our modern existence, not just in the air. I can't begin to tell you the damage this has done to my own specialty, physics, where people are starting to take models as reality, and to actually believe that the model is giving them direct information about the world. This has gone so far as to cause people to imagine that they've got reality licked down to the first nanoseconds of existence, and that up to 95 percent of the universe is unobservable, and all this within 100 years of discovering its most basic rules. In this toxic and neurotic environment, it's almost impossible to have a reasoned discussion - the digital universe has acquired a life of its own, and a strange religious fervor has settled over what should be the most rational and sane of investigative bodies. One fantastic whopper after another emerges from the dark vortex of neurosis that has ingested academic physics.

There is no earthly reason to have an airplane whose crew are mere stewards to some cheap pile of circuits somewhere in its chin. There is nothing wrong with using computers to help control an airplane, but from reading all this catechism of modes and laws of the FMC, I'm strongly reminded of the irreal universe of modern physics. The same deadly neurosis is sweeping over aviation under the pretense of cost savings. There is something utterly disturbing about the idea of a perfectly good, flyable airplane falling from the sky because its crew are sitting there staring at screens and processing idiotically coded error reports generated by some pimply digeratus with a belly full of fast food and soda in some tacky office who knows where? I've seen IT/software engineering/whatever buzzword you wish to use from the inside and it's ugly, and whether it's a pile of milspec engineers or a crowd of H1B slaves makes no difference.
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Old 25th May 2011, 11:45
  #2348 (permalink)  
 
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Originally Posted by deSitter View Post
...some pimply digeratus with a belly full of fast food and soda in some tacky office who knows where?
Jebus - that's some serious bile you have there. Ever tried counselling?

I've seen IT/software engineering/whatever buzzword you wish to use from the inside and it's ugly, and whether it's a pile of milspec engineers or a crowd of H1B slaves makes no difference.
Then as a physicist - a man of science and reason - you of all people should be aware of the dangers of confusing a single anecdote with data.
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Old 25th May 2011, 11:45
  #2349 (permalink)  
 
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de sitter. That is probably the truest statement in ........... the history of the universe.
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Old 25th May 2011, 12:11
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squawk ident, thank you for the update.

That would seem to be a very fast recovery rate, given the time it takes to get to the bottom and then back up.

It may be that the Ile de Sein's crew change was to bring aboard more members of the National Gendarmerie.

The Head of the GTA’s Investigation Unit further indicated that the recovery of bodies is an especially difficult operation whose success in uncertain. Should it succeed, all the necessary arrangements will be made on board by IRCGN* experts whose team will be strengthened. The identification procedure will later be performed in France in accordance with international
protocols.
http://www.diplomatie.gouv.fr/fr/IMG...fo_anglais.pdf

* National Gendarmerie’s Criminal Research Institute (IRCGN)

Speculation, but this recovery phase may be concentrating only on recovery of the bodies, and once that is completed, the Ile de Sein would again swap crews if any other parts of the plane are to be retrieved in the future.
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Old 25th May 2011, 12:24
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DozyWan, anyone who appreciates the ugly reality of pseudo-engineering cannot help but be galled.
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Old 25th May 2011, 12:29
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Originally Posted by deSitter View Post
DozyWan, anyone who appreciates the ugly reality of pseudo-engineering cannot help but be galled.
Trust me, if you'd actually studied Software Engineering at even an undergraduate level, you'd quickly realise it's a discipline that shares the same reliance on repetition, models and a*se-achingly dry textbooks filled with complex graphs and barely-comprehensible formulae as engineering of any other stripe. Are you stating that as far as you're concerned the only "real" engineering exists in the physical realm?

Some Computer Science degrees these days tends to effectively be BSc Java Programming, however a Software Engineering degree is a very different beast that happens to share the same underpinnings.
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Old 25th May 2011, 12:38
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Angel Mr. Pitot's tube(s)

One or more Pitot tubes have been fitted to most aircraft that have ever flownn and a better system of finding one's airspeed has yet to become general aviation practice - or even perhaps, invented.
This, basically, for those who find to their horror, that all aircraft, ancient of modern, have a "single point of failure".
Mr. Pitot's invention has served aviation well, worldwide, and throughout the ages, so calm down people ... !!
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Old 25th May 2011, 12:46
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Originally Posted by 25th May 2011, 01:10 oldchina
More automation = more dangerous, is that your point?
Strawman, and a misreading of deSitter's theme. His point is behavioral and systemic, which is over-reliance on automation, which leads to an imbalance in the man-machine interface.
Take a look at page 21 of this Boeing document, then please shut up.

One would expect that, over the time frame given, and the amount of time and effort expended, that causal factors would be identified and solutions proposed. The accident rate would be expected to go down, due to a cultural imperative that it do so. It has been reduced thanks to the flying community communicating to, educating, and training pilots, crews, and all ground staff on accident prevention. Likewise the technical fixes/advancements that have come along. (IFF? TCAS? ILS? GPS? Wind Shear detection?)


That said, each tool has its limits, and traps.


What has also happened in the last sixty years, oldchina, is that we now fly successfully in conditions that we could not at the start point of that graph. So we do. In the year 2011, passenger aircraft are able to risk departing from and landing in more dangerous conditions than when I was born. You could say we are collectively trying to get to the very edge of the danger zone on a routine basis. So the risk profile (and the need for greater mitigation) is much higher now.


The man-machine interface is at the heart of modern machine accidents.

The most effective mitigation for that is training and profieincy in use, as well as awareness of the machine's limitations. As true of my car, or lawn mower, as of any aircraft I ever flew.

I don't think those numbers tell you what you were asserting in your demand that deSitter shut up.
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Old 25th May 2011, 12:47
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Jig Peter's right. The Space Shuttle has ................... pitot tubes.

NASA Media Item
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Old 25th May 2011, 12:53
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Agreed, Jig Peter. There are thousands of planes relying on pitot at this instant. Icing seems to be a rare event, and even more rare in non-Airbus.

Thanks to Sensor Validation for the OZ link, from which I quote.
On 28 October 2009, an Airbus A330-202 (A330) aircraft, registered VH-EBA (EBA), was being operated as Jetstar flight 12 on a scheduled passenger service from Narita, Japan to Coolangatta, Australia. Soon after entering cloud at 39,000 ft, there was a brief period of disagreement between the aircraft's three sources of airspeed information. The autopilot, autothrust and flight directors disconnected, a NAV ADR DISAGREE caution message occurred, and the flight control system reverted to alternate law, which meant that some flight envelope protections were no longer available. There was no effect on the aircraft's flight path, and the flight crew followed the operator's documented procedures. The airspeed disagreement was due to a temporary obstruction of the captain's and standby pitot probes, probably due to ice crystals. A similar event occurred on the same aircraft on 15 March 2009.


The rate of unreliable airspeed events involving the make of pitot probes fitted to EBA (Goodrich 0851HL) was substantially lower than for other probes previously approved for fitment to A330/A340 aircraft. However, both of the events involving EBA occurred in environmental conditions outside those specified in the certification requirements for the pitot probes. The French Bureau d'Enquêtes et d'Analyses pour la sécurité de l'aviation civile (BEA) has recommended the European Aviation Safety Agency (EASA) to review the certification criteria for pitot probes in icing environments.
Are they building the best pitot they can, or just building to (inadequate) requirements?

Last edited by Jetdriver; 25th May 2011 at 23:15.
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Old 25th May 2011, 13:43
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Originally Posted by Jig Peter
a better system of finding one's airspeed has yet to become general aviation practice
I'd suggest there is a high probability that the reason that is so, is because "general aviation practice" has commonly been to follow the axiom: If it ain't broke, don't fix it.

As these UAS incidents have been on the increase, and probably already "contributed"* to major loss of life, perhaps it's time to consider Mr. Pitot's tubes "broke"? There are plenty of other ways to measure airspeed... Surely one less disturbed by ice crystals could be adopted for back-up at altitudes where they're encountered?

* Though the statement UAS "is not cause for Loss of Control" is undoubtedly correct, I think it is likely to be a significant link in a chain of causal events.

Last edited by 3holelover; 26th May 2011 at 17:04.
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Old 25th May 2011, 13:47
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Mr. Pitot's invention has served aviation well, worldwide, and throughout the ages, so calm down people ... !!
Very true. But maybe their time is drawing to a close Its not that the pitot tube has suddenly become inadequate. The issue is that the rest of the system has moved on over 200 years - to the point that the system the pitot inputs to now may not adequately cope with the occasional pitot malfunction.GIGO.

Pitot tubes must have been suffering from occasional episodes of icing for many years. The problem is not so much that the tube generates a false airspeed. The problem is that the technology may not be able to reliably pick an UAS state, makes changes assuming the false airspeed to be true, and the pilot is increasingly out of the loop with degraded SA.

I would like to see more emphasis on pilot training and simulation as suggested by others. I really would. Not to turn back the clock and throw out the automation. But to help improve the pilot:system interface, which is something I suspect has been neglected somewhat. For many reasons, I am doubtful that is going to happen however - a new generation less critical of technology, economics, start-up airlines in developing countries (with some very poor track records), existing airlines facing increased competition, reducing hours requirements.......

Its not just aviation. Its every aspect of our lives. Less understanding, but more acceptance of technology (? blind faith) despite this decreased understanding.
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Old 25th May 2011, 13:51
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Pitot tubes must have been suffering from occasional episodes of icing for many years.
Would it help if the heating elements were beefed up? Too low tech?
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Old 25th May 2011, 14:16
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On an emergent path to DIRECT LAW, the automatics degrade, losing protections. From 'Monitor' to PIC, the pilot gains SA and acquires command as the Computed Flight Path disappears. I submit that in any "Loss" of acuity, whether Man or Machine, one be selected immediately to Fly the airplane.

BOAC wrote some scholarly papers on this. Can we see the links?
 

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