Tech Log The very best in practical technical discussion on the web

AF447

Old 26th Jun 2009, 18:09
  #2381 (permalink)  
 
Join Date: Jun 2009
Location: paradise,bc
Age: 78
Posts: 22
Water at subzero temps

Here's where the much earlier comment about supercooled water could come into play. As I understand it, the term refers to water that has not passed from the liquid to solid state despite being below the freezing point. This can happen when cooling takes place very quickly, and in the absence of both mechanical forces AND particulate matter such as dust, around which crystals would normally begin to form. I've long since forgotten the physics, maybe something to do with the expansion and subsequent contraction of the droplet which would normally happen during "graceful" cooling.

BAM, the supercooled droplet undergoes mechanical stress, upsetting the delicate supercooled state, and it solidifies upon contact with the AC.
From here, I get lost in the thermodynamics of sublimation, melting and
eventual equilibrium. It strikes me, however, that a relatively large mass
of supercooled water (now ice) forming VERY suddenly might take a few
or many seconds to clear, even with fairly powerful heaters - remembering that latent heat of fusion thing....
cribbagepeg is offline  
Old 26th Jun 2009, 18:09
  #2382 (permalink)  
 
Join Date: Jun 2009
Location: Colorado
Age: 70
Posts: 48
I agree PJ2, I've been involved in computing for the last 25 years and know full well that perfect software is unobtainable. I also understand the difference between good and good enough.

It looks like we're following man's usual stepping stones to progress; one disaster after another ...
EGMA is offline  
Old 26th Jun 2009, 18:09
  #2383 (permalink)  
 
Join Date: Jun 2009
Location: in a plasma cocoon
Age: 49
Posts: 244
to Squawk_ident: the press communique from the BEA of the 23th of June did not necessarily suggest that the information from "Le Monde" was erroneous, but rather maybe that in the absence of a positive identification of the signals having been picked up, the press release was deemed as prematured (the BEA said that any established fact will be made public).
Jeff
Hyperveloce is offline  
Old 26th Jun 2009, 18:14
  #2384 (permalink)  
 
Join Date: Jul 2008
Location: Milwaukee WI
Age: 68
Posts: 35
Redundancy/Alternate Law

Instrusion from SPL; disregard as desired.

The problem with redundancy is when there are common fault cases. For example if (hypothetically - not implying this happened with AF447) there is a certain environmental condition where a pitot sensor is susceptible to icing, this might apply to all three.
Reminiscent of the BA 747 losing all four engines from flying through a cloud of volcanic ash, or the L-1011 that lost two engines (and most of the thrust from the third) due to losing oil from not having the oil plugs replaced after a check of some kind.
With three failed pitot sensors, there ain't a whole bunch clever software can do. Even with two failures, you have a big problem - two incorrect sensors in agreement with each other, or possibly three all disagreeing
Garbage in, garbage out is the saying in the software business.

If indeed there is a pitot icing problem here, the problem is a mechanical/physical pitot/static sensor design problem NOT one in the software/automation.
Except that the software’s response to the issue could be better. Why not have the A/P go into attitude hold in this case, instead of simply disconnect? A given attitude and power setting will result in sufficient airspeed stability to at least assess the problem without having to wrestle with the airplane at the same time.

If they were on direct law, they were lucky, IMHO. In alternate law, if IAS goes to a (right or wrong) low figure one has to pull the stick to avoid nose down automatic command (and the contrary for high - right or wrong - IAS reading).
What’s the design justification for even having altenate law? Wouldn’t it be better for the pilot simply to know that the normal law envelope protections are gone, rather than have to remember which subset of them are still in effect? In some ways, partial envelope protection (if that’s what alternate law provides) is worse than none at all – especially if the transition occurs at a difficult moment, as seems to be inherently the case.
bratschewurst is offline  
Old 26th Jun 2009, 18:44
  #2385 (permalink)  
 
Join Date: Nov 2006
Location: SoCalif
Posts: 898
Delta/NW Confirmation

Just received this from friend, Rafael, appended to the NW pilot's email:

"Rafael, I just drove a Boeing 747-400 through this same area on the same day. We were circumnavigating a typhoon. The old timers at United taught us young kids to operate the radar in max gain at high altitude to avoid dry tops. I ended up at FL410 and due to strong down drafts we required max power to hold on to our airspeed. Lots of zig zagging, but not one drop of visible moisture. Fly fast, H."

This is factual; I remember H. when he was a kid at our local airport. His Dad retired from UAL as Capt on the -400.

GB
Graybeard is offline  
Old 26th Jun 2009, 19:09
  #2386 (permalink)  
 
Join Date: Jan 2001
Location: France
Posts: 163
Hyperveloce

Of course the BEA is considering sacred all informations especially if it come only and solely filtered and originated from them. Now I don't see the French Navy and very likely other vessels from other Navy making circles around whales talking (someone - not on this forum - thought that he had to say that in case there might be some confusions). And now it is a fact that a signal is received because I can't think one second (might be wrong) that all the people on board these boats do not exactly know what noise or signal they are looking for.
Wait and see mais le temps passe...
Squawk_ident is offline  
Old 26th Jun 2009, 20:02
  #2387 (permalink)  
 
Join Date: Mar 2009
Location: S23W046
Age: 70
Posts: 57
Angry Downgraded Flt Ctrls

I want to strongly confirm that I am not 'anti-Airbus', BUT this is giving me goose bumps:

It is interesting that the report notes that the AIRPLANE OPERATING MANUAL states that when comparison between both ADR systems is impossible (ADR-DISAGREE) and the stby system isn't available either, as was the case here, the flight crew should act on their own discretion and experience.
Does that mean in a situation like this the pilots are left alone completely and supposed to find out how to overcome it? That is what I ment earlier with machine-human interface. I am not as naively as to think that one could take care of any thinkable problem, but leaving the user of a highly computerized system alone when it breaks down, without giving some advice how to safe the day, is simply unacceptably. Or does it arrogantly implicate that a situation like this never ever could exist? This on an a/c that 'anybody' could fly?

Quote:
If they were on direct law, they were lucky, IMHO. In alternate law, if IAS goes to a (right or wrong) low figure one has to pull the stick to avoid nose down automatic command (and the contrary for high - right or wrong - IAS reading).
What’s the design justification for even having altenate law? Wouldn’t it be better for the pilot simply to know that the normal law envelope protections are gone, rather than have to remember which subset of them are still in effect? In some ways, partial envelope protection (if that’s what alternate law provides) is worse than none at all – especially if the transition occurs at a difficult moment, as seems to be inherently the case.
Not only ONE 'Altn Law', there are TWO with slight differences protectionwise. So it is even more complicated.

Why do we as pilots accept something like this?

I am positively not against modernization, but I do have problems with accepting a system that rather cold calculates the 10^9 case and more or less pushes the pilot out of the loop. This is my oppinion, but as far as I remember, air law in any country holds us primarily responsible for the safety of persons on bord. Did we give up on this?
Flyinheavy is offline  
Old 26th Jun 2009, 20:25
  #2388 (permalink)  
 
Join Date: Apr 2009
Location: Petaluma
Posts: 330
YRP

I disagree fundamentally with your position. "It isn't the software/automation".
I proposed early on that the interface between Otto and flying pilots is weak and in an out of balance "command" way. It is too quick and too absolute, seemingly wonderful traits, but deadly under certain circumstances. Pilots are comfortable (too much so) when things go pear and the computers make command decisions that are precipitous, and leave the ultimate pilot out of "the loop".

Imagine flying along fat and happy, and in less time than one can belch, the box cascades decisions and reports to be assimilated immediately with the a/c and its contents at risk!! Dark, turbulent, seven miles up, and the box hands two people two folders of data, to be understood and acted upon whilst the seats under your primitive "cheeks gyro" are telling you you have one half second to input a control.

The previous reports of similar loss of data flow involved less than harrowing conditions, and were successfully escaped; conclusions about those incidents are being debated even now, and you are at ease with the highly possible loss of data, panel, as, etc. to be dumped unceremoniously on the pilots laps???

This interface is the 400 kg gorilla no one seems to be discussing.
Will Fraser is offline  
Old 26th Jun 2009, 20:40
  #2389 (permalink)  
 
Join Date: Aug 2005
Location: Devon, England
Posts: 249
Have we yet reached the point where the recorders are no longer functioning?
manrow is offline  
Old 26th Jun 2009, 20:51
  #2390 (permalink)  
 
Join Date: Jan 2008
Location: Esher, Surrey
Posts: 465
JD-EE

The NTSB were very tardy in adding this report to the index.
It is oh so simple today to find it.
Yesterday the lack of the index item was causing many to question if it was a a genuine report hence all the chat about it.
beamender99 is online now  
Old 26th Jun 2009, 21:25
  #2391 (permalink)  
 
Join Date: Jun 2009
Location: Germany
Age: 67
Posts: 782
Quote: bratchewurst

Except that the software’s response to the issue could be better. Why not have the A/P go into attitude hold in this case, instead of simply disconnect? A given attitude and power setting will result in sufficient airspeed stability to at least assess the problem without having to wrestle with the airplane at the same time.

isn´t that the real problem nowadays? Is the Crew in the cockpit for studying panels and manuals or are those Pilots there to act like pilots?

In my days the first item in any kind of emergency was

Maintain Aircraft Control

Reading Checklist items came after that.
The big difference probably being that we had to wrestle with the aircraft also without any kind of emergencies.

With this answer here i do not intend to blame the Crew of AF447 for acting wrong, there are no informations to that.
RetiredF4 is offline  
Old 26th Jun 2009, 21:33
  #2392 (permalink)  
I don't own this space under my name. I should have leased it while I still could
 
Join Date: Dec 2002
Location: Lincolnshire
Age: 77
Posts: 16,692
Originally Posted by manrow View Post
Have we yet reached the point where the recorders are no longer functioning?
Theoretically no.

There have been reports that the French Navy has heard something. Now I am wracking my brains to remember what is needed next.

For a single point detection you will have an approximate bearing and signal strength. Given the short maximum range the probable position will be quite small.

Detecting from a different position with then enable them to reduce the area of probability and so on.

An alternative and more accurate method would be simultaneous detection of a pulse from 3 hydrophones. The position could them be determined through hyperbolic reduction. You would get a position within 200-300 metres.
Pontius Navigator is online now  
Old 26th Jun 2009, 23:29
  #2393 (permalink)  
 
Join Date: Jun 2009
Location: Iowa
Posts: 9
What’s the design justification for even having altenate law? Wouldn’t it be better for the pilot simply to know that the normal law envelope protections are gone, rather than have to remember which subset of them are still in effect? In some ways, partial envelope protection (if that’s what alternate law provides) is worse than none at all – especially if the transition occurs at a difficult moment, as seems to be inherently the case.
This highlights what I have seen a lot on this forum: the lack of differentiation between automation, control systems and flight protection systems. Unless you have the autopilot on, the airplane is not making any flight decisions for you. The flight envelope protections LIMIT your control inputs but they do not make control inputs for you. These limits are calculated on the fly (haha) by the computers using the available flight data, according to some extremely complex models about the aircraft, and then padded a little bit for stability (as in, derated to be on the safe side). Other than that, the inputs made on the sidestick (or the yoke on a Boeing aircraft) are modified by a gain and then transmitted on.

The autopilot is another matter, being a feedback system that trys to keep a control variable at a given value. This system GENERATES flight control inputs. FEP limits flight control inputs, but does not generate them.

As for why you'd want alternate laws, not all the protections rely on every peice of sensor data. Why give up ALL protections if you only need to give up one? For whatever reason, the concepts of modes of operation are very common in many industries. The idea being that a person can associate a number of states with just a single name. I'd assume that Boeing would have a similar mechanism for degrading the flight protections but I can't find any verification for this right now.

As for the "interface", there is no real interface. Someone in this thread has mentioned this multiple times. The sidestick functions exactly the same in every law. The only difference with FEP is that if you slam the sidestick to one side then you won't crash the aircraft. The FEP system reduces pilot workload by making it so s/he doesn't have to concentrate strictly on keeping the airplane aloft, but on providing it a course.

I don't understand why these concepts do not seem to stick.
jeremiahrex is offline  
Old 26th Jun 2009, 23:32
  #2394 (permalink)  
 
Join Date: Jan 2008
Location: Herts, UK
Posts: 743
Is that saying they have searched an area 'visually' corresponding to 350,000 km. sq. !

Britain has a surface area of 244,820 km. sq.

And 'electronically' searched an area of 2 million km. sq !

Last edited by HarryMann; 26th Jun 2009 at 23:44.
HarryMann is offline  
Old 26th Jun 2009, 23:48
  #2395 (permalink)  
 
Join Date: Sep 2005
Location: Horsham, UK
Posts: 1
Brazilian forces have stopped searches

Google translation:

:: FAB - Brazilian Air Force::

26/06/2009 - 19h02
Final Note - 26.06.09

TERMINATION OF THE SEARCHES OF AIR FRANCE FLIGHT 447

Command and the Navy Command of the Air report that at the end of today, June 26, was officially given by the end of the largest and most complex operation of Search and Rescue has already carried out by Brazilian armed forces in sea area, both in appearance duration as the magnitude of the means employed.

In these 26 days to search the passengers and crew of Air France flight 447, which disappeared when they flew on the route Rio de Janeiro (RJ) - Paris (France), on the night of May 31, 2009 were 51 bodies and rescued more than 600 parts and structural components of the aircraft, and several bags.

The technical reason that determined the end of the search is the impracticability of sights survivors or bodies, primary objective of the operation, already 26 days after the accident. The day on June 12th to 26th, a period of 15 days, only two bodies were recovered, and the last on 17. In the last nine days, no body has been sighted or prey.

The 51 recovered bodies were delivered to the Federal Police and the Department of Social Defense of Pernambuco to the work of identification. The wreckage of the aircraft and luggage collected were delivered to the Bureau d'Investigations et D'Analysis of I'Aviation Pour la Securite Civile (BEA). Research on the factors that contributed to the accident is also the responsibility of the BEA and has the support of the corresponding sector, the Brazilian Center for Research and Prevention of Aeronautical Accidents (CENIPA).

In 26 days of continuous operation under the responsibility of Brazil, in response to the international search and rescue, the Brazilian Air Force used 12 aircraft and had the support of aircraft from France, U.S. and Spain. The Brazilian Navy has served in rotation with 11 ships in the area of search, totaling about 35 thousand miles navigated, approximately eight times the size of the Brazilian coast.

Were flown around 1500 hours and was conducted visual searches in an area corresponding to 350 thousand square kilometers, more than three times the size of the state of Pernambuco. The R-99 aircraft, in turn, electronic search conducted in an area corresponding to two million square kilometers, eight times the size of the state.

Were directly involved in the 1344 military operation of the Brazilian Navy and 268 from FAB, totaling more than 1,600 professionals in the tasks of search, rescue and support these activities.

Remain in the area to search the resources dedicated to marine capture emissions data and voice boxes of rugged aircraft, coordinated by France.
All the search operation was under the direct responsibility of the Department of Control of the airspace (DECEA) by means of Recife SALVAERO saved in coordination with the Northeast and attended to the provisions of Annex 12 to the Chicago Convention, effective in 1950, which establishes the commitment of signatory countries to the search and rescue operations in their areas of jurisdiction.

Mindful of its mission, the crew and other members of the Navy Command of the Air Command and make your way to work that day just to offer reverence to the pain that mark Brazilian families and the international community.

MEDIA CENTER OF MARINE
MEDIA CENTER OF AERONAUTICS

Last edited by michaell; 26th Jun 2009 at 23:49. Reason: Typo correction
michaell is offline  
Old 26th Jun 2009, 23:56
  #2396 (permalink)  
 
Join Date: Apr 2009
Location: Petaluma
Posts: 330
To state 'there is no interface' is disingenuous. Since the beginning, tools are a characteristic of human existence. Learning to use a scythe develops an 'interface'. This attitude, I submit is what is wrong with at least some of the ABI philosophy. Instead of a 'tool' the automatics are proposed to be nothing less than a superior 'pilot', whose purpose is to 'protect' the airplane. Inherent in this language is an 'attitude' (a human one) of 'supremacy'.

Who protects the a/c from the 'box'??? A 'cleaning lady' can fly this a/c!!!

"What's it doing now?"

For anyone to state 'there is no interface' merely underscores the root of the problem and his/her own lack of understanding. IMHO. I think too, that a loss of sensors as is demonstrable prior to if not a part of this accident, presents an arguably suitable example of the differences involved in manual flight and a litany of pre-programmed failures that cascade from a manageable defect into a very dangerous reluctance of the computers to perform at even a very basic level of expectation.

Will
Will Fraser is offline  
Old 27th Jun 2009, 00:00
  #2397 (permalink)  
 
Join Date: May 2009
Location: China (CGO)
Age: 72
Posts: 164
Associated Press

An AP item posted two hours ago on the French version of Yahoo cites USAF Col. Willie Berges, in charge of US forces participating in the search, as saying operations would continue for "at least another 16 days" and "we'll have a better picture on July 1st." He added the Brazilians and French would make the final call on when to terminate operations.
ArthurBorges is offline  
Old 27th Jun 2009, 00:15
  #2398 (permalink)  
 
Join Date: Jun 2009
Location: Vancouver
Posts: 3
Computers Probed in Crash Doomed Air France Jet Suffered Cascading System Failure, In

Air investigators, running out of time to find the "black boxes" with key information on the crash of Air France Flight 447, suspect a rapid chain of computer and equipment malfunctions stripped the crew of automation today's pilots typically rely on to control a big jetliner.
An international team of experts is building a scenario in which it believes a cascade of system failures, seemingly beginning with malfunctioning airspeed sensors, rapidly progressed to what appeared to be sweeping computer outages, according to people familiar with the probe. The Airbus A330, en route from Rio de Janeiro to Paris, crashed into the Atlantic Ocean during a storm 26 days ago, killing all 228 aboard.


Based on an analysis of the sketchy information from automatic maintenance messages sent by the aircraft, these people said, the plane bucked through heavy turbulence created by a thunderstorm without the full protection of its flight-control systems -- safeguards that experts say pilots now often take for granted.


Relying on backup instruments, the Air France pilots apparently struggled to restart flight-management computers even as their plane may have begun breaking up from excessive speed, according to theories developed by investigators.
The investigators stress it is too early to pinpoint specific causes. But whatever the eventual findings, the crash already is prompting questions about how thoroughly aviators are trained to cope with widespread computer glitches midflight.
If such emergencies do occur on today's increasingly automated jetliners, many industry safety experts wonder how proficient the average crew may be in trying to rely on less-sophisticated backup systems.
"The difficulty is, they're rare enough that pilots can be unprepared, but likely enough to pose a real threat," according to Bill Voss, president of the Flight Safety Foundation, an industry-supported group based in Alexandria, Va. "We need to examine how to deal with automation anomalies."
Unlike jetliners built in previous decades -- which required pilots to frequently manipulate controls and often manually fly the planes for long stretches -- newer computer-centric aircraft such as the A330 and Boeing's 777 are designed to operate almost entirely on automated systems. From choosing engine settings and routes to smoothing out the ride during turbulence and landing in low visibility, pilots essentially monitor instruments and seldom interfere with computerized commands. So when those electronic brains begin to act weirdly at 35,000 feet, the latest crop of aviators may be less comfortable stepping in and grabbing control of the airplane.



Airlines typically use simulators to train cockpit crews for such events, but a pilot may only hone skills to deal with major computer problems every few years. Pilots hardly ever experience multiple computer failures in real-world conditions.
Crews commanding a flotilla of specially-equipped vessels are still trolling an area with a radius of at least 50 miles for the black boxes -- the digital recorders containing detailed flight data and cockpit conversations from the flight. The sea floor beneath where debris was found floating is mountainous and up to 15,000 feet deep. The recorders are designed to have enough battery power to last for at least 30 days. That deadline runs out Wednesday, though investigators and safety experts believe that signals may last for at least a couple more weeks.
Because the A330 is one of the most widely used planes in commercial aviation, crash sleuths "aren't likely to easily stick with an undetermined cause," according to John Cox, a former Airbus pilot who now works as an industry consultant. Instead, investigators "will exhaust every possibility" to pinpoint probable reasons and contributing factors, Mr. Cox said, even without the black boxes, though they may have to be cautious about a definitive assessment.
In place of that data, they would use computer simulations to try to lay out the possible sequence of events, and then work backwards, eliminating as many potential causes as possible.
A progress report from French officials leading the probe could come as early as next week. At this point, the bulk of the information made public about the Air France tragedy deals with suspected problems with external speed sensors, or so-called pitot tubes, which have a history of icing up and malfunctioning on different Airbus models.
On Thursday, U.S. investigators disclosed two recent incidents in which they believe Airbus A330 jets suffered air-speed sensor malfunctions that led to more sweeping system failures. Both of those planes landed safely.
A Northwest Airlines A330 flying from Hong Kong to Tokyo earlier this week, for example, ran into a situation which investigators believe may be a similar to what took place on the flight deck of the Air France jet.
The Northwest crew reported entering a storm in daylight and running into turbulence; in less than a minute their primary and standby airspeed indicators showed the plane had slowed dramatically. Other systems that automatically maintain speed and altitude also disengaged. Things didn't return to normal for three minutes as the captain flew the aircraft out of the rain, according to information gathered by U.S. safety officials.
The scene inside Air France Flight 447 may have been more ominous from the beginning. The crew was flying at night and the storm they tried to traverse may have been more violent.
After the initial speed warnings, the Air France pilots are believed to have quickly lost the autopilot and automated throttle-controls, which are designed to instantly disengage when speed readings are suspect. Soon after, according to people familiar with the investigation, cockpit instruments showed a series of warnings about various other equipment failures and the crew apparently shut down or tried to reboot their primary and secondary computer systems.
It's not clear what happened next. But the pilots, perhaps distracted by wildly fluctuating airspeed indications, along with the cacophony of other cockpit warnings, could have allowed the jetliner to gain excessive speed that possibly tore off sections of the plane.
The aircraft could have accelerated and run into danger because faulty instruments convinced the Air France crew the twin-engine jet was traveling so slowly that it was close to stalling. That may have prompted them to rev up the engines or point the nose down to go faster.
One difficult question is whether all three air-speed sensors located on the lower curve of A330's nose -- including a backup device -- failed. If so, investigators are trying to understand whether the pilots followed procedures that call for maintaining engine power and whether they took other steps to ride out the emergency. Planes can -- and occasionally do -- fly safely without pitot probes functioning properly. That's why industry and government investigators believe some other important factor, which hasn't been identified yet, likely contributed to the crash.
Airlines are likely to pay more attention to helping pilots better understand the ripple effect that can occur when computerized flight controls, altitude indicators and other systems go haywire. There are detailed check lists for each chain of events, but to save on training time and cost, typically airlines limit simulator time for pilots to experience the full range of things that can go wrong.
"Such issues are talked about regularly during training," according to John Goglia, a former member of the National Transportation Safety Board, but "pilots only occasionally have the chance to practice" reverting to backup cockpit instruments and flying without the usual computerized systems.
Callas is offline  
Old 27th Jun 2009, 00:26
  #2399 (permalink)  
 
Join Date: Jan 2008
Location: Los Angeles
Posts: 27
The only difference with FEP is that if you slam the sidestick to one side then you won't crash the aircraft.
The corollory to that is if you haven't got enough control authority to crash the aircraft you probably haven't enough authority to recover it from a major upset either.

Your "padding" of the FEP limits may be the difference between recovery and disintegration and under current control laws this part of the envelope can't be entered. Despite stress predictions, ultimate load tests, failure path analysis and all the other good stuff, airframes do not necessarily break apart when overstressed as has been proven many times.

When it all goes pear shaped you want to be able to control the aircraft by whatever means necessary, not negotiate with it.

Rgds.

24V
24victor is offline  
Old 27th Jun 2009, 00:37
  #2400 (permalink)  
 
Join Date: Jun 2009
Location: I am where I am and that's all where I am.
Posts: 660
Callas, without the attribution for your long message it's not worth the time it took to post it.

JD-EE
JD-EE is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.