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AF 447 Search to resume (part2)

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AF 447 Search to resume (part2)

Old 24th May 2011, 22:27
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syseng68k; Sad really, but it's surprising how much of that early work is still relevant today. The history of electronics and computing can be a rich source of ideas for modern day designs. For example, embedded systems with very limited resources. You probably know this, but if you want to be astounded, take the lid off an early electromechanical inertial nav system. It's doubtfull if there are many engineers left in the world now who have the multidisciplinary skill set to even start to design such a system... Modern work is dependent on all that early work, which is why it is still relevant but no longer taught. Pity how new engineers are poorly grounded in the broad aspects of their craft. It's like my business - recently trained practitioners can't make a diagnosis in the basis of conversing with a patient - they need the imaging technology. Cheers, K PS - I could probably still write a RTOS in 16K of machine code.
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Old 24th May 2011, 22:37
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AF447 latest info

Just received.

Black Boxes Point to Pilot Error

By ANDY PASZTOR And DANIEL MICHAELS

(WSJ) The pilots of an Air France jet that crashed into the Atlantic Ocean two years ago apparently became distracted with faulty airspeed indicators and failed to properly deal with other vital systems, including adjusting engine thrust, according to people familiar with preliminary findings from the plane's recorders.

The final moments inside the cockpit of the twin-engine Airbus A330, these people said, indicate the pilots seemingly were confused by alarms they received from various automated flight-control systems as the plane passed through some turbulence typical on the route from Rio de Janeiro to Paris. They also faced unexpectedly heavy icing at 35,000 feet. Such icing is renowned for making airspeed-indicators and other external sensors unreliable.

Ultimately, despite the fact that primary cockpit displays functioned normally, the crew failed to follow standard procedures to maintain or increase thrust and keep the aircraft's nose level, while trouble-shooting and waiting for the airspeed sensors and related functions to return to normal, according to these people.

Slated to be disclosed by investigators on Friday, the sequence of events captured on the recorders is expected to highlight that the jet slowed dangerously shortly after the autopilot disconnected. The pilots almost immediately faced the beginning of what became a series of automation failures or disconnects related to problems with the plane's airspeed sensors, these people said.

The crew methodically tried to respond to the warnings, according to people familiar with the probe, but apparently had difficulty sorting out the warning messages, chimes and other cues while also keeping close track of essential displays showing engine power and aircraft trajectory.

Spokesmen for Air France, a unit of Air France-KLM, and Airbus, a unit of European Aeronautic Defence & Space Co., have declined to comment on any details of the investigation. Airbus last week, however, issued a bulletin reassuring airlines that the preliminary readout of the recorders hasn't prompted any "immediate recommendation" regarding the safety of the global A330 fleet. French investigators, who gave the green light for that statement, also have said their preliminary findings don't highlight any major system failures or malfunctions that could have caused the fatal dive.

The Air France pilots were never trained to handle precisely such an emergency, according to safety experts and a previous report by France's Bureau d'Enquetes et d'Analyses, which is heading up the investigation. All 228 people aboard Flight 447 died in the accident.

The senior captain, Marc Dubois, appears to have been on a routine rest break in the cabin when the fatal chain of events started, according to safety experts familiar with the details, but the cockpit-voice recorder suggests he may have rushed back to the cockpit to join the other two Flight 447 pilots.

Though Friday's announcement won't provide final conclusions or specific causes, investigators believe Air France didn't train its pilots to cope with such automation problems in conjunction with a high-altitude aerodynamic stall, an emergency when the wings lose lift and the plane quickly becomes uncontrollable. Since the crash, Airbus and a number carriers, including Air France, have emphasized such training.

According to a report issued by French investigators in November 2009, Airbus identified 32 instances involving similar model jetliners between 2003 and 2009 in which external speed probes, known as pitot tubes, suffered ice buildup at high altitude and caused "erroneous air speed indications." Over the years, the same models also suffered numerous failures of external temperature-sensors because of icing. Both issues were known to Air France.

Most of the incidents with speed sensors involved probes similar to those on the A330 that crashed. Many were on Air France planes, according to the BEA report.

Friday's update follows sniping between senior officials of Air France and Airbus, usually close corporate allies, who in this case have tried to shift the blame for the accident to each other.

Air France began addressing problems with its pitot tubes almost a year before the crash. Amid several incidents in which air crews lost speed indication at high altitude during 2008, Air France reported the icing problems to Airbus. The two companies discussed solutions and Airbus talked to its supplier.

In April 2009, roughly 45 days before the crash, Airbus proposed that Air France swap out its pitot tubes for a different model believed to be less prone to icing, according to the BEA report. Air France began the work on April 27, 2009, and it received the first batch of new pitot tubes six days before the crash. The plane that crashed hadn't yet received the new equipment.

According to the 2009 report published by investigators after the crash, experts examined 13 other incidents of airspeed-sensor malfunctions on Airbus widebody jets at cruise altitudes. During most of those global incidents-none of which resulted in a crash-both the autopilots and automated engine-thrust systems disconnected on their own, and it took many of the flight crews up to a minute to manually adjust engine thrust.

The earlier report found that pilots in nine of those 13 events received warnings of an impending stall. And in a finding that may have particular relevance to the upcoming update, accident investigators in 2009 also concluded that when airspeed-sensor malfunctions kick off automated thrust controls, "the absence of appropriate manual adjustments" to engines "can present a risk" of a mismatch between power settings and the jet's orientation in the air.

Investigators began focusing on pitot problems from the start, because Flight 447's automated maintenance system broadcast 21 separate messages related to such malfunctions during roughly the last four minutes of the fatal flight. But the final report, which may not be released until 2012, also is expected to delve deeper into how European air-safety regulators dealt with persistent reports of pitot-tube icing prior to the crash.

The previous interim report indicated that in late March 2009, less than three months before the crash, European aviation regulators decided that the string of pitot-icing problems on widebody Airbus models wasn't serious enough to require mandatory replacement of pitot tubes
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Old 24th May 2011, 22:53
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I wonder if the WSJ author's have just watched the year old BBC/Nova documentary?

No mention of a control system protection triggered zoom-climb for a while?
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Old 24th May 2011, 22:58
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Smilin Ed quoting slats "If these systems fail, then control is thrown back to the pilots...."

As Self Loading Freight I find the thought that the automation flies the plane almost exclusively when things are going well and then when things get tough toss it into the laps of pilots who might otherwise get fired if they try to actually fly the plane rather than babysit some automation to be rather troublesome.

Something must be done so that the pilots, even if they are sitting there yawning with nothing to do, are intimately aware of the feel of the plane as a plane at all times. That way when things get tough the transition is not quite such a hostile appearing event.

The current situation might even be made nicer of a row of buttons appears on a touch screen display with options like, recover stall, slow down, TOGA thrust, AOA, and so forth so that the pilot can assist the automation in picking the strategy to deal with data that confuses the automation. The automation can probably react quicker. But the meatware can probably solve the problem quicker - today. (Yeah, I gotta add that proviso. I've seen some amazing "stuff" in the software world. One begins to feel redundant.)
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Old 24th May 2011, 23:01
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Originally Posted by CogSim
OTOH the post is about mission critical software. I don't see why, say, the inflight entertainment system code needs to be "ultrareliable". If someone in the know can comment on the control logic code metrics in modern a/c, it will be enlightening for the pilot types on the forum.
As SLF who is old enough to remember such comedy routines as "Grace L. Furgesun Airline and Storm Door Company" or Bob Newhart's gems I surely can... surely can... surely can... surely can...

(Is it time to panic yet?)
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Old 24th May 2011, 23:06
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Originally Posted by RR_NDB View Post
Hi,

Systemically speaking it is possible ("easily" today) to use two Pitot probes from different mfrs. (Fr and US) as LH and RH (main) sensors?
I recall that after the initial advice (following 447) to replace the dodgy Thales probes, there were not enough Goodrich ones to go round, so it was suggested to use a mixture. I don't have a reference to hand though and not sure if it was AB recommendation or regulator or both. Also, it may only have been allowable as temporary measure.

I would have a general concern (maybe you share) that different probe types with slightly different calibration & response might lead to more (spurious) unreliable airspeed events. Now, if the problem is all probes failing in same way pushing the a/c out of the envelope before the unreliable airspeed reported, then maybe this is good... but if the problem is pilots mishandling reported unreliable airspeed, then maybe this makes things worse.
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Old 24th May 2011, 23:20
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wozzo, if that WSJ quote resembles what actually happened I do not figure that is pilot error. I take that as a system design failure, which falls into the AirBus lap.
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Old 24th May 2011, 23:34
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ion berkeley, I'm glad I am not the only one here who might defend Ada. I have seen it work very well to produce military grade software under budget and with far fewer bugs than normal for the size of program involved. They performed to spec and that's what made the company money. If the spec was wrong, that's the DoD's problem (and, sadly, the soldier's problem.)

Ada works very well because you cannot write software with it without very clear "premeditation" for what you are doing. (Yes, I know, a real hairy chested programmer can write FORTRAN in any language. Trust me, it's harder in Ada than in most languages.)

It is also current. The latest release of the Ada specification is a preview of the scheduled 2012 version.

For commercial stuff Ada doesn't work very well because commercial software is seldom thoroughly defined and then developed without massive changes in direction. It is a very capable language. It is rather inflexible, resistant to changes and errors.
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Old 24th May 2011, 23:41
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I would have a general concern (maybe you share) that different probe types with slightly different calibration & response might lead to more (spurious) unreliable airspeed events

Probably not something to worry about.

Caveat - the following is generic, not AB specific.

The pitot tube basically is a bit of water pipe facing forward into the wind (it can tolerate modest out of into wind alignment) and with the other end hooked up to the aircraft's innards. One bit of tin pipe is going to be much the same as another. The only fancy bit is some heating to avoid the thing's icing up.

Generally, system errors (providing the pipe hole is not blocked) are not due to the pitot - but may well be due to static port problems. Apart from icing and like physical obstruction, pitot installations are remarkably reliable.

Mixing up the OEM pitots provides some interim redundancy for icing considerations pending the supply chain's catching up with demand for OEM changeover.
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Old 24th May 2011, 23:43
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Originally Posted by JD-EE View Post
wozzo, if that WSJ quote resembles what actually happened I do not figure that is pilot error. I take that as a system design failure, which falls into the AirBus lap.
A more pressing question is: whose conclusion is it at this point? 1) BEA's, 2) the paper's sources (which I would presume is somebody at or close to NTSB) or 3) the journalist's (as a conclusion of his gathered information)?

At least in respect to 1) we will know more Friday.
 
Old 24th May 2011, 23:44
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Wall Street Journal Report

There is something rather obvious in the WSJ story, i.e. there is absolutely nothing new, and furthermore the unnamed source(s) would appear to be "pick ups" from European papers. The authors IMO have created a story to fill a void, and in doing so have joined the likes of the News of the World etc..

There are better stories on this thread, though not everyone agrees.
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Old 24th May 2011, 23:59
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Cool

Hi,

There is something rather obvious in the WSJ story, i.e. there is absolutely nothing new, and furthermore the unnamed source(s) would appear to be "pick ups" from European papers. The authors IMO have created a story to fill a void, and in doing so have joined the likes of the News of the World etc..

There are better stories on this thread, though not everyone agrees
From the day one of the first leak (printed in Le Figaro and coming from ?) it's nothing new ..
Just parrots who repeats at length of articles:
The pilots made mistakes and the Airbus A330 is not an issue
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Old 25th May 2011, 00:02
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Originally Posted by JD-EE View Post
For commercial stuff Ada doesn't work very well because commercial software is seldom thoroughly defined and then developed without massive changes in direction.
It's a long time ago that I worked on military stuff, but "thoroughly defined" and "developed without massive changes in direction." are not really characterisitcs I'd associate with it ! "Sufficiently ill-defined that the contractor can absolutely guarnatee to claw back overruns (and under-quotes) in change control," and "subject to random changes in direction so often that by the time you go live no one can remember what the original threat was" would be more like it. Maybe I'm too cynical though.

Also, I think those that think Ada has dropped out of use just don't appreciate mil-spec project timescales. I've used Coral 66 (predates Ada by a lot of years) and the last time I was offered work in it (by idiots who just keyword search CVs without reading them) was not many years ago - I suspect it is still in use today...
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Old 25th May 2011, 00:08
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Something must be done so that the pilots, even if they are sitting there yawning with nothing to do, are intimately aware of the feel of the plane as a plane at all times. That way when things get tough the transition is not quite such a hostile appearing event.
Having throttles move via actuator to show current thrust level and trending, like Boeing does, would be a start.

Watching throttles physically retard during cruise might have been helpful to this crew in keeping SA.
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Old 25th May 2011, 00:12
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The Problematic Surface Currents - some answers?
Originally posted by NWR ...

Anyone interested in the detailed analysis used to refine the search area should see:

Search for AF447: Complimentary Studies
Thanks for posting the link to this well presented Ifremer summary (in French) of the surface current research they have undertaken.

Additionally, detailed research by the University of Massachusetts' FVCOM group based at Dartmouth, MA, supported by the Woods Hole Oceanographic Institution at Cape Cod, MA, has resulted in methodology that is now capable of making sense of the surface currents in what was a poorly understood area of circulation in the equatorial latitudes of the North Atlantic.

The currents and resulting drift patterns in this area are irregular and the drift tracks so found also provide some answers as to why the aerial and surface searches failed to find debris and bodies in the first 5/6 days of searching.

Both UMass Dartmouth and WHOI were represented on the BEA's Drift Group, and in the intervening period since then have continued their research, which I am advised will be made public in due course.
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Old 25th May 2011, 00:17
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Originally Posted by RR_NDB
We could pinpoint the moment the AS started to change in respect to "ground speed" (supposing AS sensors LYING and presenting the "identical" info.) BEA is doing all necessary correlations.
That would be the moment the aircraft instruments are turned on. Air moves independently (more or less) of the ground below. Planes go through fronts. The trick is to isolate a set of "signatures" for pitots freezing up. Then you pray that set is exhaustive while knowing in your heart it's not even close.
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Old 25th May 2011, 00:41
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KMD - 16k seems to be a very fancy advanced RTOS to me. The OM-55 Navy SatCom modem used 32k for the entire program and had 16k, with spare space, for RAM. This involved a full multi-tasking (time sliced) operating system - on an 8080. (They cost $100 a pop when it was designed.) The kernel portion was under 1k. The IO routines were small. The rest involved maintaining the DSCS satellite communications protocols running, demodulating the data, and feeding it all to the output while running the modest control panel.


edit: By the way Philbrick is in my engineering DNA. I started designing professionally in about '65 - as in getting real pay for it. And the first job or two involved operational amplifiers with these new fangled RA-909's.
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Old 25th May 2011, 00:46
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Originally Posted by Khashoggi View Post
Having throttles move via actuator to show current thrust level and trending, like Boeing does, would be a start.
Unfortunately, a number of people already died in a field near Schipol to disprove that.

If it's handled properly, unreliable airspeed in cruise in a Bus is not fatal - long list of previous incidents show that. Something else happened to 447 - either something else went wrong with the a/c, or the crew; we don't know what yet (whatever the press says).
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Old 25th May 2011, 00:48
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Yankee Whiskey, that report certainly looks fully as self-serving for "certain parties" as the other "leaks" I've seen. I am betting these are "leaks" from various interested parties rather than from inside BEA. If they are from people privy to the BEA deliberations I bet the data being released is very carefully selected and given a proper propagandistic spin. It's becoming somewhat of an embarrassment to the whole industry.
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Old 25th May 2011, 00:57
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infrequentflyer789, the proper way to handle changes like that is to charge what it costs and profit margin to recode and KNOW what that cost is. With Ada that is expensive. It tends to get the military to better define the problem.

(It helped that this was on the DSCS satellite and that Magnavox (in Torrance Ca) was the major ground systems developer. We understood the machines. And we understood how to use then in networks. The military provided the controls they wanted and we provided the rest. We came in under budget even after the changes requested. Two other projects not so intimately related to the company's hardware work also came in under budget on Ada. They all worked very well going through formal acceptance tests without failures.)
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