AF 447 Thread No. 6
stalls and "deep" stalls, yet agin
Yep, Ventus, we've all heard about the "deep stall", and went thru the litany a thousand posts ago.
I even posted a graphic of the pitch moments of the Viper to show the problem, and no T-tail or downwash on the HS or....
We have looked at some unofficial charts of the Airbus and it does not appear to to have the classic deep stall combinations of downwash or lack of nose down pitch moments due to c.g. as with the Viper In other words, it appears that if the crew had applied nose down stick and maybe nose down trim that the jet would have "flown out" of the stall.
This is not unusual for many military fighters built since the late 60's. The hornet can duplicate the AF447 profile quite easily. To recover? let go of the back pressure and push the stick forward, just like a Cessna 150. Duhhhh?
Problem is recognition of the stall and the approach to stall on a well-designed, modern jet. Buffet can be confused with mach problems. No horrendous yaw excursions or abrupt pitch changes. The sucker will settle into a decent stall and not spin due to great yaw control laws and such. May have some roll tendencies, but not like +/- 20 or 30 degrees back and forth.
Apparently, the crew couldn't hear or disregarded the aural stall warning sounds. So I would think a simple stick "vibrator" could get the pilot's attention to look at the "new, improved" AoA indicator that should be installed. No timy bar graph, but something as big as speed and such. Red at top, yellow in middle and green at bottom. Pull and get into red, push and get into green. Real simple, and the Navy pilots have used the equivalent for 50 years when landing on the rolling deck of a carrier.
I even posted a graphic of the pitch moments of the Viper to show the problem, and no T-tail or downwash on the HS or....
We have looked at some unofficial charts of the Airbus and it does not appear to to have the classic deep stall combinations of downwash or lack of nose down pitch moments due to c.g. as with the Viper In other words, it appears that if the crew had applied nose down stick and maybe nose down trim that the jet would have "flown out" of the stall.
This is not unusual for many military fighters built since the late 60's. The hornet can duplicate the AF447 profile quite easily. To recover? let go of the back pressure and push the stick forward, just like a Cessna 150. Duhhhh?
Problem is recognition of the stall and the approach to stall on a well-designed, modern jet. Buffet can be confused with mach problems. No horrendous yaw excursions or abrupt pitch changes. The sucker will settle into a decent stall and not spin due to great yaw control laws and such. May have some roll tendencies, but not like +/- 20 or 30 degrees back and forth.
Apparently, the crew couldn't hear or disregarded the aural stall warning sounds. So I would think a simple stick "vibrator" could get the pilot's attention to look at the "new, improved" AoA indicator that should be installed. No timy bar graph, but something as big as speed and such. Red at top, yellow in middle and green at bottom. Pull and get into red, push and get into green. Real simple, and the Navy pilots have used the equivalent for 50 years when landing on the rolling deck of a carrier.
Join Date: Jul 2002
Location: UK
Posts: 3,093
Likes: 0
Received 0 Likes
on
0 Posts
What this boils down to is that in night-time IMC, the human pilots have less of an advantage over the computers than they do in daylight hours in terms of perception, but again, the human ability to problem solve "on the fly" is still better than that of any computer system of the vintage used in modern airliners - as a reminder :
Code:
Aircraft Computer Chip H/W Development S/W Development
-------- -------- ----- --------------- ---------------
A320: ELAC Motorola Thompson-CSF Thompson-CSF
68000
SEC Intel SFENA Aerospatiale
80186 Atelier Logiciel
A3[3/4]0: FCPC Intel Aerospatiale Aerospatiale
80386 ADL Atelier Logiciel
FCSC Intel Sextant Aerospatiale
80186 Avionique Atelier Logiciel
Fundamentally, while I understand your desire to engineer a way out of this situation, I think following that path is well-intentioned, but misguided. History has shown that nature (and the human psyche in particular) can outwit the best efforts of engineers almost every time.
Join Date: Oct 2009
Location: berlin
Posts: 152
Likes: 0
Received 0 Likes
on
0 Posts
gums So I would think a simple stick "vibrator" could get the pilot's attention to look at the "new, improved" AoA indicator that should be installed. No timy bar graph, but something as big as speed and such. Red at top, yellow in middle and green at bottom. Pull and get into red, push and get into green. Real simple, and the Navy pilots have used the equivalent for 50 years when landing on the rolling deck of a carrier.
http://www.dg-flugzeugbau.de/uploads...aden-4.jpg.jpg
yaw and AoA indicators
Yeah, Grity, if you could see the AoA string sucker, then you might/could use it! Night could be a problem.
We had a "yaw string" on the T-33, and that sucker worked up to 400 knots or so. Couldn't see it at night, but in daylight it helped one to learn to coordinate rudder with aileron.
A thorough training curriculum seems best recommendation from the accident board at this time, IMHO. Real planes at real conditions and with an experienced instructor. More value than with any simulator ever built.
I also want to take exploit this post to challenge one contributor that asserts the best way to stop on a slick runway is to watch the speed indications on the gauges. Beam me up! If I hit the brakes and I don't "feel" some effect, but "feel" I am actually going faster, then I don't need to look at some steenkeeeng gauge. I know that I am sliding on the ice or water. If anti-skid is working, I'll see some effect, and feel it as well. I'll guarantee most pilots here can sense the lack of decelleration faster than the airspeed/groundspeed gauge can reflect. The same applies to when a good crosswind is present when rolling out on a slick runway. Ain't no gauge invented except a HUD with a good flight path vector that is still working with weight-on-wheels that shows you that you are sliding off the runway. You look out the windshield and feel your skid. Simply holding a heading won't help.
On the other hand, relying too much, if at all, on your human senses while in bad weather most often leads to disaster. Gotta trust the instruments ( except 'bus airspeed in icing conditions). Our human sensors are great for detecting initial body rates, but degrade very quickly after a few seconds. Our human gee sensing is fairly close to what a machine sensor would detect, but that is not good for survival after the initial pitch input on the controls. It simply lets you know that the plane is reacting to your initial input. After that you had better trust the instruments.
We had a "yaw string" on the T-33, and that sucker worked up to 400 knots or so. Couldn't see it at night, but in daylight it helped one to learn to coordinate rudder with aileron.
A thorough training curriculum seems best recommendation from the accident board at this time, IMHO. Real planes at real conditions and with an experienced instructor. More value than with any simulator ever built.
I also want to take exploit this post to challenge one contributor that asserts the best way to stop on a slick runway is to watch the speed indications on the gauges. Beam me up! If I hit the brakes and I don't "feel" some effect, but "feel" I am actually going faster, then I don't need to look at some steenkeeeng gauge. I know that I am sliding on the ice or water. If anti-skid is working, I'll see some effect, and feel it as well. I'll guarantee most pilots here can sense the lack of decelleration faster than the airspeed/groundspeed gauge can reflect. The same applies to when a good crosswind is present when rolling out on a slick runway. Ain't no gauge invented except a HUD with a good flight path vector that is still working with weight-on-wheels that shows you that you are sliding off the runway. You look out the windshield and feel your skid. Simply holding a heading won't help.
On the other hand, relying too much, if at all, on your human senses while in bad weather most often leads to disaster. Gotta trust the instruments ( except 'bus airspeed in icing conditions). Our human sensors are great for detecting initial body rates, but degrade very quickly after a few seconds. Our human gee sensing is fairly close to what a machine sensor would detect, but that is not good for survival after the initial pitch input on the controls. It simply lets you know that the plane is reacting to your initial input. After that you had better trust the instruments.
Join Date: Aug 2011
Location: USA
Posts: 1
Likes: 0
Received 0 Likes
on
0 Posts
Interested non-pilot observer here. I've read much of the AF447 threads here and on airliners.net, and was fascinated by this accident when it first occurred.
One thing struck me though in the last thread here. In post 1346 in thread 5, "xcitation" brought up airbus manual specs stating that during high speed protection the flight computer adds "positive nose up g demand to the sidestick order." I would like to know, definitively: would such a computer-added input be included in the input traces sent to the FDR? If so, it seems possible there was a logic error that caused added nose up g demand during an UAS situation, and that nose up was included in the recorded data from the sidestick. In that case, the PF may not have been actually holding stick back input, and there would be no way to tell from the ADR traces.
I would like assurance that the input data traces from the FDR are raw inputs, and are never altered at all by the computer, in any situation. If they can be altered, then the PF's input traces are useless, because it could be PF error, or it could be computer error that is indistinguishable from PF error.
One thing struck me though in the last thread here. In post 1346 in thread 5, "xcitation" brought up airbus manual specs stating that during high speed protection the flight computer adds "positive nose up g demand to the sidestick order." I would like to know, definitively: would such a computer-added input be included in the input traces sent to the FDR? If so, it seems possible there was a logic error that caused added nose up g demand during an UAS situation, and that nose up was included in the recorded data from the sidestick. In that case, the PF may not have been actually holding stick back input, and there would be no way to tell from the ADR traces.
I would like assurance that the input data traces from the FDR are raw inputs, and are never altered at all by the computer, in any situation. If they can be altered, then the PF's input traces are useless, because it could be PF error, or it could be computer error that is indistinguishable from PF error.
loxosceles;
The parameter for side stick position reports the side stick position, unmodified by any other inputs.
A slight confusion may occur if one considers that, for example, an aileron parameter will indicate the position of that surface, as controlled by the FCPCs [flight control primary computers] which are controlled in turn either by the side stick in manual flight or the EFCS [electronic flight control system] in autoflight. But the parameter still indicates actual "position" of the control surface.
Aircraft system, aircraft state and environmental parameters' design and mode of operating are thoroughly understood such that any untoward behaviours of a system are almost certainly going to be known. This was evident in the QF72 pitch incident.
I would like assurance that the input data traces from the FDR are raw inputs, and are never altered at all by the computer, in any situation. If they can be altered, then the PF's input traces are useless, because it could be PF error, or it could be computer error that is indistinguishable from PF error.
A slight confusion may occur if one considers that, for example, an aileron parameter will indicate the position of that surface, as controlled by the FCPCs [flight control primary computers] which are controlled in turn either by the side stick in manual flight or the EFCS [electronic flight control system] in autoflight. But the parameter still indicates actual "position" of the control surface.
Aircraft system, aircraft state and environmental parameters' design and mode of operating are thoroughly understood such that any untoward behaviours of a system are almost certainly going to be known. This was evident in the QF72 pitch incident.
Fine posts, gums, thank you.
IIRC there is the opinion that the aircraft could have been recovered from the stall, but opinions have varied regarding the altitude from which recovery could have been made. From what has been said, the elevators remained effective throughout the descent.
We have looked at some unofficial charts of the Airbus and it does not appear to to have the classic deep stall combinations of downwash or lack of nose down pitch moments due to c.g. as with the Viper In other words, it appears that if the crew had applied nose down stick and maybe nose down trim that the jet would have "flown out" of the stall.
If someone who knows has the time and patience, could they explain what actions would be necessary for the crew to get the AP back and what dynamic state the a/c must be in for the AP to capture control ? Reason for asking is that before the 'details' became known I rather expected to find the crew heads-down dealing with the computers but this seems not to have been any sort of factor.
Join Date: Jun 2009
Location: I am where I am and that's all where I am.
Posts: 660
Likes: 0
Received 0 Likes
on
0 Posts
Chu Chu, with a wry grin I note that in this case the meatware proved faulty, probably for the same reason, faulty or incomplete programming, as the software might fail. I think that's an interesting if off beat way to look at the problem.
Per Ardua ad Astraeus
Join Date: Mar 2000
Location: UK
Posts: 18,579
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by gums
I am disturbed by some here that believe you can handle an emergency situation or an "upset" ( love that term, and cracks me up and guess it really means "WTF?, over") by following rote, memorized procedures for more than a few seconds.
What EXACTLY do you propose a pilot should do for those 'few seconds' when all is 'WTF' confusion? What do you suggest that stall recovery should be? 'By rote' reduce AoA or some other gums method involving what process? Nose high, speed falling - 'by rote' lower the nose, use power with care and bank if necessary or 'by gums' - let's see, I have 25deg nose up and 4000fpm up and speed decreasing through Vstall+20, so out with the spin-wheel/QRH and I need......................?
I'm afraid I cannot see your point, sir. Indeed, on the many occasions when I was, like you, 'outside the envelope' in my miltary days it was the 'by rote' that saved me..
Join Date: Jun 2009
Location: I am where I am and that's all where I am.
Posts: 660
Likes: 0
Received 0 Likes
on
0 Posts
HN 39 asks, "Which computer?"
At the very least the wee little computer that drives the FDR surely knows. If it knows then its source can also route that data where ever else it is needed.
At the very least the wee little computer that drives the FDR surely knows. If it knows then its source can also route that data where ever else it is needed.
I guess the general idea is that the pilots are as smart as the programmers/procedure writers, and therefore can fill in any holes on the spot. I'm sure that hasn't actually been the case since the Wright Brothers. But maybe the AF 447 pilots could have filled in the particular hole here if they'd been better equipped.
plan A, then B, then C, then...
Sorry, BOAC, I worded my concern poorly.
You are spot on as far as the initial procedure and then "plan B" and so forth. That process has certainly saved many of us here. Lest anyone here think otherwise, I fully support your position.
I was trying to point out to some folks that simply executing the tried and proven procedures/techniques may not be enough to recover from some "upsets" or cope with unusual system malfunctions. In other words, there are a very few conditions that are not covered by the known procedures. The two incidents that strike home are Sully's ditch and the Sioux City DC-10 landing attempt. After their initial actions, and not getting results, both crews went on to new territory and did not sit there for 3 minutes doing the same thing.
Hope that makes my position clear.
You are spot on as far as the initial procedure and then "plan B" and so forth. That process has certainly saved many of us here. Lest anyone here think otherwise, I fully support your position.
I was trying to point out to some folks that simply executing the tried and proven procedures/techniques may not be enough to recover from some "upsets" or cope with unusual system malfunctions. In other words, there are a very few conditions that are not covered by the known procedures. The two incidents that strike home are Sully's ditch and the Sioux City DC-10 landing attempt. After their initial actions, and not getting results, both crews went on to new territory and did not sit there for 3 minutes doing the same thing.
Hope that makes my position clear.
Join Date: Aug 2011
Location: Grassy Valley
Posts: 2,074
Likes: 0
Received 0 Likes
on
0 Posts
I first used "ROTE" as a pejorative; and to expand, 'rote' (the word) is not in and of itself unhelpful. As JD-EE eloquently puts it, 'the meatware had a software glitch'.
In America, 'rote learning' is seen as dispassionate, and insensate. Unfortunately, in a cultural setting, a word frequently conjurs all manner of misunderstanding, here, what confuses is the unsaid.
The "clipped" sense of 'rote' means more or less, "Instead of using your thinker".
Common usage is, well, common.
Rote.
In this misunderstanding here, perhaps an opportunity to close the consensus gap.
ROTE is 'bitchin'. ROTE is 'sick'. ROTE is 'memory items', for purposes here?
Language, so boring w/o it. 'Fly'.
gums. that is it, in suede. It is the 'Between' SOPS, and (UAS Drill), and Sully's test flight (w/o the brief), that the solution lies.
It is a no-man's land, a Maginot Line of suspicion, ignorance, and Pride, with globs of ego in there as well.
Take one of our engineer friends for a hop in your family model, and see if they grok what it can be like, flying with one's hair on fire.
Time is GOD's way of making certain everything does not happen at once.
'Transition' is what we do, or DIE. "I have the Controls' hmmm.......
really? because........
In America, 'rote learning' is seen as dispassionate, and insensate. Unfortunately, in a cultural setting, a word frequently conjurs all manner of misunderstanding, here, what confuses is the unsaid.
The "clipped" sense of 'rote' means more or less, "Instead of using your thinker".
Common usage is, well, common.
Rote.
In this misunderstanding here, perhaps an opportunity to close the consensus gap.
ROTE is 'bitchin'. ROTE is 'sick'. ROTE is 'memory items', for purposes here?
Language, so boring w/o it. 'Fly'.
gums. that is it, in suede. It is the 'Between' SOPS, and (UAS Drill), and Sully's test flight (w/o the brief), that the solution lies.
It is a no-man's land, a Maginot Line of suspicion, ignorance, and Pride, with globs of ego in there as well.
Take one of our engineer friends for a hop in your family model, and see if they grok what it can be like, flying with one's hair on fire.
Time is GOD's way of making certain everything does not happen at once.
'Transition' is what we do, or DIE. "I have the Controls' hmmm.......
really? because........
Join Date: Jan 2005
Location: France
Posts: 2,315
Likes: 0
Received 0 Likes
on
0 Posts
It's barely a 'computer'... the French term 'ordinateur' would be better.
It doesn't 'know' anything, and it doesn't 'think', it just converts and formats the multiple original AC and DC signals and digital info to a single formatted digital data stream (ARINC 717) which is then recorded by the FDR.
The link below is litle more than advertising, but may give you a few hints.
Teledyne FDIU
Join Date: Aug 2011
Location: Grassy Valley
Posts: 2,074
Likes: 0
Received 0 Likes
on
0 Posts
PJ2 this is in re: your following POST (don't ask me).......
(your #553)
Nothing personal, and certain to be flamed as PARSE.
They did not ADAPT, they CREATED. Adapt means to conform, and I am sure that is not what one meant, because in that sense it is remarkably disrespectful to some extremely talented people.
Creation is what is at stake here. Mostly Man destroys, the rest ADAPT, and the brilliant CREATE.
That is the essence of thus entire kerfuffle. Shall we CREATE, OR ADAPT?
ADAPTATION is the default, To create is to control. Automation is the ultimate adaptation, and clearly, there is a point of view at work here.
(your #553)
Nothing personal, and certain to be flamed as PARSE.
They did not ADAPT, they CREATED. Adapt means to conform, and I am sure that is not what one meant, because in that sense it is remarkably disrespectful to some extremely talented people.
Creation is what is at stake here. Mostly Man destroys, the rest ADAPT, and the brilliant CREATE.
That is the essence of thus entire kerfuffle. Shall we CREATE, OR ADAPT?
ADAPTATION is the default, To create is to control. Automation is the ultimate adaptation, and clearly, there is a point of view at work here.
gums;
...and the British Airways B747 Flight 9 encounter with volcanic ash at Jakarta. Your point is well taken. In other words, these crews knew their aircraft and flew it. If something didn't work, they adapted through knowledge and experience.
The two incidents that strike home are Sully's ditch and the Sioux City DC-10 landing attempt. After their initial actions, and not getting results, both crews went on to new territory and did not sit there for 3 minutes doing the same thing.
Join Date: Aug 2011
Location: Grassy Valley
Posts: 2,074
Likes: 0
Received 0 Likes
on
0 Posts
Sorry if I seem to bracket one.
Automation is an adaptive environment, by definition. The upside is that man created the environment, for once. Then he fell immediately into what is demeaning, an adaptive posture.
On the one hand brilliantly creating his own environment, "Can you imagine?". Then, dumbly acquiescing into its power.
One has suggested Human Factors is the proper venue for this discussion, there you go.
Automation is an adaptive environment, by definition. The upside is that man created the environment, for once. Then he fell immediately into what is demeaning, an adaptive posture.
On the one hand brilliantly creating his own environment, "Can you imagine?". Then, dumbly acquiescing into its power.
One has suggested Human Factors is the proper venue for this discussion, there you go.
Join Date: Oct 2009
Location: berlin
Posts: 152
Likes: 0
Received 0 Likes
on
0 Posts
gums We had a "yaw string" on the T-33, and that sucker worked up to 400 knots or so. Couldn't see it at night, but in daylight it helped one to learn to coordinate rudder with aileron.
but the side window yaw string is not for the side slide he is a good AoA indicator!, and I am shure it is easy possible to enlight it at night..... just open the window like nico and hang it out ....
