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AF 447 Search to resume (part2)

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AF 447 Search to resume (part2)

Old 19th May 2011, 18:11
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Cool

Hi,

All this discussion of what the Airbus FMCs do is interesting, but irrelevant - when humans are confronted by a computer that is either not working, or working in a regime they are not intimately familiar with, they freeze - they go into brain lock. This happens with all kinds of systems, from text editors to banking systems, and I'm sure it happens with aircraft FMCs. If you are going to design airplanes that fly on the edge of control with the help of computers to constantly trim them, then you'd better make sure that the airplane still manually flies like an airplane at the drop of a hat, one that a pilot can control *instinctively*, despite his brain lock! This is a criticism neither of pilots, nor of computer systems - it's the truth of human/computer interaction. It will never matter how well designed are Airbus' or Boeing's FMCs - if they are not purposely designed to make the airplane act like an airplane under pilot input, then they are not only wrong-headed, they are dangerous!
I agree .. that make sens
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Old 19th May 2011, 18:27
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when humans are confronted by a computer that is either not working, or working in a regime they are not intimately familiar with, they freeze - they go into brain lock.
I believe you are referring to untrained non-professionals, no?


a pilot can control *instinctively*
Abandoning your training and following your instinct is usually the quickest path to the scene of an accident.


if they are not purposely designed to make the airplane act like an airplane under pilot input
Be assured -- they are.


then they are not only wrong-headed, they are dangerous!
Uh, no.
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Old 19th May 2011, 18:39
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Securite

In the dim and distant past when I was a very junior AATC in the RAF and "Preston Airways" was alive and well at Northern Radar I remember the demise of the third level of emergency call below that of of "Mayday" & "Pan" this third level call was "Securite"
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Old 19th May 2011, 18:42
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Securite

Sorry, I should have addressed this to lonewolf 50 and others in relation to the word Securite
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Old 19th May 2011, 18:43
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In my view, the whole case for what the computers can do with regard to stability is overstated. Even computers can't make rocks fly. The aerodynamic form of the a/c no matter how inefficient demands that it keep flying. As long as the integrity of the structure is preserved, it takes some effort (either on the part of the computers or the pilots or both) to keep the a/c from flying. This is the context in which we should look at direct law. It simply takes the computers out and lets the aerodynamics do its thing. The question is will the pilots be prepared to start flying stick and rudder at the drop of a hat?
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Old 19th May 2011, 18:50
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Take the point about NR headsets, which I used from the early 1990s. Being short-haul, we had our headsets on nearly all the time. What I can tell you is that, when the cabin crew entered the cockpit, we had little difficulty hearing them and conversing. Admittedly, we often slid one earpiece off, but I'm not sure that was necessary. My understanding and experience was that it was steady "noise" that was almost eliminated: e.g., the 400Hz hum from the AC electrics, the airframe noise, and the engine noise.

I'd be surprised if "hot mikes" were phased out on UK-registered aircraft as a result of noise-reduction headsets.
There are two entirely different animals at play in commercial aviation boomsets and we need to careful that the features are not mixed up...

Active Noise Reducing (ANR) headsets (i..e. Bose Aviation X, Telex 850, etc) that include an electronic circuit to reduce noise heard when wearing the headset - what this system does is exactly as you describe - elimination of steady "noise" by comparing the noise signature outside of the earcups and generating an anti-phase version of the same noise within the earcup, resulting on cancellation of the external steady noise. This is an output system...

Noise cancelling microphones (or more accurately 'directional microphones') affect only the input signal (so heard in your transmissions, primarily to reduce noise in what 'you' send to others).

As for "hot mic" recording, I think there is a specific CVR configuration that allows hot mic continuous recording, but it does not seem to be standard.
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Old 19th May 2011, 18:58
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No Mechaca, I am not referring to non-trained professionals - I've seen 20 year IT people with A+ skills go completely blank and stare hopelessly at the same text for minutes on end, when confronted by strange issues. I've seen physicists try to make physical sense of manifest nonsense, because "the computer must be right - it's my fault". It's the nature of all humans to assume they are wrong, that they are doing something that's not in the manual, and to start pushing buttons hoping to regain control, not just of the computer system, but of themselves. If computers are going to fly airplanes, then they must do so under complete command of the crew, and in a sudden control emergency, it is senseless to lack an instant "GIMME" switch, that turns the airplane into a very big stick-and-rudder platform. I have no doubt that in the end, we'll find out that the crew lost precious time trying to figure out what to do with the FMC, or even as someone suggested earlier, put the AP back in charge when that was sure to lead to disaster.

I have no idea why some professional aviators are so adamant, to the point of irrationality, in their defense of flight computers. Perhaps it is the human need to feel "on top of the curve" and "up to snuff" with modernity. No one is arguing that FMCs are not a great idea for normal flight - but when it becomes an end in itself, something has gone off the rails.
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Old 19th May 2011, 19:02
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CogSim - that's exactly right, and it's the point I'm trying to make. It's not enough to just be able to turn off the FMC - there has to be a designed-in envelope of stability that is familiar to crew and instantly available, and that will stimulate their natural instincts, not present them with puzzlers that eat into their situational awareness.
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Old 19th May 2011, 19:08
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The A332 schedules fuel into the tail during refuelling for a load above 34.5t and it schedules up to about 2500kg until the selected quantity is above 71.788t. This is also the figure when the centretank starts to fill. The trim is full with a fuel aboard at 105.2t
The standard practice for my company A332 is to put all the bags in holds 3 and 4 to achieve a rearward cg for fuel economy but ours are in a two class fit and are generally full throughout.
Fuel is loaded into the trim for fuel economy and on the A300-600 for flight envelope purposes at mtow. During my time on the A332 I do not remember ever loading more than 80t with 10 hour sectors and high zfw and for most of our flights the centre tank was empty. I also only can think of one crew who ever filled one up with fuel and this is only possible when the aircraft is empty.
Does anybody have a copy of the flight plan with the flight time and an idea of the zfw? I could then give a rough guess as to the likely fuel aboard at push back.i could also do a rough calculation of where the cg was but I am guessing at around 37%
As to hot mics all of our UK registered aircraft have this and they are all anr equipped.
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Old 19th May 2011, 19:14
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Man-Machine Interface

"To err is human, to really foul things up requires a computer"
(Murphy's law?)
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Old 19th May 2011, 19:14
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If it wasn't so poignant, it would be funny
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Old 19th May 2011, 19:24
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there has to be a designed-in envelope of stability that is familiar to crew and instantly available, and that will stimulate their natural instincts, not present them with puzzlers that eat into their situational awareness.
I have no idea why some professional aviators are so adamant, to the point of irrationality, in their defense of flight computers. Perhaps it is the human need to feel "on top of the curve" and "up to snuff" with modernity.
Correct, you have no idea. I respectfully suggest you haven't the slightest clue about the design, engineering, testing, and production of modern transport category aircraft and their systems. Your keyhole view makes it appear irrational to you.

Those professionals who in fact do, ARE on top of the curve and up to snuff. And to staggeringly profound levels.

Respect what you don't comprehend, and debate it when you have an informed argument to bring.
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Old 19th May 2011, 19:39
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tubby, from the first interim report

The aircraft left the gate with a calculated weight of 233,257 kg. The estimated takeoff weight was 232,757 kg, for a maximum authorised takeoff weight of 233 t. This takeoff weight broke down as follows:

• empty weight in operating condition: 126,010 kg,
• passenger weight: 17,615 kg (126 men, 82 women, 7 children and one baby),
• weight in cargo compartment (freight and luggage): 18,732 kg,
• fuel weight: 70,400 kg.

The on-board fuel weight corresponded to forecast trip fuel of 63,900 kg, route factor fuel of 1,460 kg, final reserve of 2,200 kg, fuel to alternate airport reserve of 1,900 kg and 940 kg additional fuel. An LMC corrected the definitive load sheet to take into account one passenger fewer without baggage.

The balance corresponding to the aircraft’s takeoff weight and given on the definitive load sheet (after LMC) was 23.3% of the MAC, for a forward limit of 22.7% and an aft limit of 36.2% at takeoff.

On the basis of the operational flight plan, it is possible to estimate the trip fuel at 27.8 t after a flying time of 3 h 41 min, the aircraft would then have had an estimated weight of 205 t and balance comprised between 37.3% and 37.8 %, which is within the limits of the operating envelope.

Routing and wapoints
ATLANTICO (SBAO) 1 h 33 INTOL BRAZIL
OCEANIC DAKAR (GOOO) 2 h 20 TASIL SENEGAL
OCEANIC SAL (GVSC) 3 h 43 POMAT CAPE VERDE
CANARIAS (GCCC) 4 h 37 IPERA SPAIN
CASABLANCA (GMMM) 6 h 2 SAMAR MOROCCO
LISBOA (LPCC) 6 h 47 BAROK PORTUGAL
MADRID (LECM) 7 h 22 BABOV SPAIN
BREST (LFRR) 8 h 1 DELOG FRANCE
PARIS (LFFF) 8 h 35 NORMI FRANCE
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Old 19th May 2011, 19:44
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CogSim
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If it wasn't so poignant, it would be funny


I do not agree with what you say. I think that tubby linton should change his location to something less distasteful, as his present one has no connecton to his actual location. A bit out of order IMO for this thread.
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Old 19th May 2011, 20:02
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But his "location" applies to him no matter which thread he posts in. I seriously doubt he's making light of AF447.

By flying on instincts, do some of you mean "flying based on trained and learned habit patterns and experiences?"

I am not sure how you mean "instinct" in this sense, which is why I am asking.

For Machaca:

Be assured -- they are.
"They are" based on what assumptions?

This may be a dated reference (mid 1990's) but there was an aircrew in Japan whose Captain had the plane not respond to his control inputs. That crash would not reassure me, but I've flown on commercial air transport since, so my risk assessment is that such bugs are not frequent enough to stop me from traveling. (The industry itself, on the other hand ... )

Granted, there has been ample opportunity since then to mitigate some of the bugs in the system, with the sytsem being the human/machine interface.

The various incidents where oddball AP inputs, and uncommanded control inputs, force the pilots to overcome the robot are reassuring only in that it demonstrates how important the Human element is in the human/machine interface. As with non-FBW aircraft, "how well do you know your aircraft" is a question pilots confront daily.

Last edited by Lonewolf_50; 19th May 2011 at 20:13.
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Old 19th May 2011, 20:31
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location

I know I've been lost under the sea trying to get answers about how such a tragedy could have happened. At least that's the way I took it. YMMV.

When I read instinct, I'm reminded of what Wolfgang Langewiesche calls "seat of the pants" flying. I think it is largely accepted to be irrelevant in modern day piloting.
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Old 19th May 2011, 20:38
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"seat of the pants" flying. I think it is largely accepted to be irrelevant in modern day piloting.
Is that why some pilots are losing perfectly flyable airplanes? I'd suggest, that if you are right, that could answer many questions.
Until computers are perfect, there most certainly will always be situations where the pilot had better know how to fly an airplane, as opposed to a computer.
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Old 19th May 2011, 21:01
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Until computers are perfect, there most certainly will always be situations where the pilot had better know how to fly an airplane, as opposed to a computer.
I agree. However, the reliance on training and instrumentation comes from the realization that your "instincts" can fool you, and do so surreptitiously.

If you are interested,

"Appendix D. Human Factors" of the final report on PK-KKW makes for a sobering read.

http://www.dephub.go.id/knkt/ntsc_av...KW_Release.pdf
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Old 19th May 2011, 21:10
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Thanks for the link CogSim. I'm downloading it now... I'm not familiar with the reg, but I hope it's not one of those times when the pilots "instinct" was to pull up, as his stalled aircraft plummeted earthward. ....you see, I'd call that a layman's instinct, not a pilot's. Any "pilot" worthy of carrying hapless folks in his machine had better instinctively KNOW how to get out of a stall. (in truth, he should know how to avoid getting there in the first place, but that's certainly not "instinctive".)
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Old 19th May 2011, 21:26
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Just to add some fuel to the discussion; some interesting quotes from NASA's initiative on Integrated Resilient Aircraft Control (IRAC) -“Stability, Maneuverability, and Safe Landing in the Presence of Adverse Conditions”

2009 Paper: http://www.aeronautics.nasa.gov/nra_...ch_plan_c1.pdf

Slide: http://www.eng.morgan.edu/~cibac/eve...%20(Totah).pdf

The application focus of this technology is for current and next generation subsonic civil transports. However, a majority of the challenges addressed by the IRAC project are general in nature, and therefore, the solutions will apply to a large class of aviation vehicles.
Simulation and/or flight validation of controller performance during an adverse event poses several challenges. Current state-of-the-art in aircraft modeling cannot accurately predict aerodynamic and/or flight dynamic characteristics under departed and loss-of-control conditions.
cmt: On that basis, simple extrapolations in FFS may have to remain the norm for a while longer

Problem Statement:
Previous research has shown that even though pilots may be able to regain "control" of a damaged or degraded aircraft, they may still not be able to achieve a safe runway landing. Oftentimes the vehicle's responsiveness under damaged or degraded conditions may become too slow for the pilot to achieve runway alignment without the assistance of automation. However conventional autopilots and flight directors are not designed to handle off-nominal conditions. Furthermore, Flight Management Systems have only been pre-programmed for a small number of "reasonably probable" [FAA FAR term] emergencies such as having an
"engine out." The goal of "Integrated adaptive mission management tools for safe flight" is to provide a suite of tools to assist the pilot in achieving a safe landing under adverse conditions.
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