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AF 447 Thread No. 5

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AF 447 Thread No. 5

Old 11th Jul 2011, 07:32
  #61 (permalink)  
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Originally Posted by JD-EE
BOAC seems to still desipise the glass cockpit and FBW the glass cockpit and FBW the glass cockpit and FBW. Right or wrong it is not going to go away no matter how much he rails about it.
- I'm afraid, that like many other inputs from many 'experts' on this huge sequence of threads, that is a complete mis-representation. If you read the other thread (Safety forum) you will discover that it is the attitude to the implementation of "the glass cockpit and FBW" and its interface with the pink and fleshy bits that operate it that I "despise" - if that is your chosen approach.

Even PJ's 'Golden Rules' from Airbus (how concerning is it that this needed to be published? Where have we 'arrived'?) make no mention I could find of 'Direct Law' handling, merely 'manual flight' - ie 'protected'. It makes no mention of that fact that the 'protection' we 'sell you' with the aeroplane may not. The mindset that needs to be broken is that all this is going to 'look after you'. It will until it doesn't. That, if anything. must be the key message. BA tried hard a few years back (following a worrying spate of loss of 'SA' and common-sense induced by the mesmerising glass) with a far-seeing course for pilots called 'EOI' - 'Enhancing Operational Integrity'.

One further comment - I am concerned that these 'graphs' produced after hours of hard work by folk like MM and A33 will pass rapidly into the 'factual' world - as pseudo FDR traces - when in fact they are supposition - guess-work - based on extremely limited information. We just do not know enough at this time.
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Old 11th Jul 2011, 07:39
  #62 (permalink)  
 
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I'm no expert but I've been trying to follow the AF447 tech thread with the aid of the Flight Crew Operating Manual here..

http://www.mercadodaaviacao.com.br/a...t_controls.pdf

In the section on Alternate Law it says..

Quote:
Low speed stability
At low speed, a nose down demand is introduced in reference to IAS, instead of angle of attack and alternate law changes to direct law.
Won't going to Direct Law remove the nose down demand that it just tried to apply? It says in Direct Law all protections are inoperative.

Have I missunderstood?
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Old 11th Jul 2011, 07:40
  #63 (permalink)  
 
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Originally Posted by Machinbird
The problem with the trim is that it moved to a high aircraft nose up setting without crew awareness.
Any pilot flying an aircraft with autotrim should know that his trim will follow his stick imputs, shouldn't he?
Originally Posted by Machinbird
It appears that a FBW aircraft requires the pilot to know exactly what mode the aircraft is operating in or else the question arises, "What's it doing now?"
Isn't it one of the basic skill needed for one wanting to be rated for a specific type? What makes you think that many FBW pilots don't know exactly in what mode their aircraft is operating?
Originally Posted by Machinbird
In the case of the AF447 crew, they had no attention to spare to consider what the trim might be doing
Well, considering that the trim was doing what a type rated PF asked, and what it is always supposed to do in such a case, what would be the point to consider that it would take more "attention" than usually?
Originally Posted by Machinbird
thus the nose up demands caused the trim to run silently to a high setting
Hence, as usual when imputs ask for a lot of nose up, what is wrong with that?
Originally Posted by Machinbird
without the knowledge or anticipation of the crew.
What make you believe that a type rated crew would not anticipate it or lacked the knowledge that it will do exactly that? Do you think that it wasn't what they wanted, nose up?
Originally Posted by Machinbird
Once at a high setting, the trim acted to stabilize the aircraft in the deep stall that they eventually achieved.
Right, the PF achieved a full stall with the help of the side stick, thrust and THS trim. Hence, what's wrong with the side stick, the thrust lever and the THS trim?
Originally Posted by Machinbird
When the Captain arrived on the flight deck, he had to puzzle out what he was seeing. From the jump seat, the indications were essentially hidden by the wheels themselves.
Beside hindsight, what makes you believe that the Captain would have immediately recovered the situation with all the trim settings displayed under his nose? He wasn't there from the begining of the crisis and still possibly far behind the other pilots. He also might have seen the Flight Control page, where the THS trim setting is displayed, right in front of him...
Originally Posted by Machinbird
The THS autotrim system has virtually eliminated the problem of trim-runaway, but it has replaced that problem with a new set of problems.
I still can see the problem with the THS trim. If they had acknowlegded their stalled situation in time, they would have immediately applied full and sustained nose down imputs, hence, THS trim would very likely follow that. If, for whatever reason, THS trim would not follow those imputs, not enough elvators authority should have attracted PF attention about considering that trimming nose down could help him... at least, theoretically if his training level wasn't the issue.
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Old 11th Jul 2011, 07:48
  #64 (permalink)  
 
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Hi BOAC,
... it is the attitude to the implementation of "the glass cockpit and FBW" and its interface with the pink and fleshy bits that operate it that I "despise"..
I tend to agree with you. If you keep taking tactile feed back away from a pilot, then you reduce him/her to a visual clues only input processor. If the FBW computers couldn't cope without valid airspeed information, is it a bit too much to expect a human to do a better job without the benefit of a "conventional aircraft's elevator feel"?

Last edited by rudderrudderrat; 11th Jul 2011 at 12:31. Reason: statement turned to query & added "conventional"
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Old 11th Jul 2011, 08:21
  #65 (permalink)  
 
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Cool

Hi,

takata whrote
Quote:
Originally Posted by Machinbird
The problem with the trim is that it moved to a high aircraft nose up setting without crew awareness.

Any pilot flying an aircraft with autotrim should know that his trim will follow his stick imputs, shouldn't he?
Quote:
Originally Posted by Machinbird
It appears that a FBW aircraft requires the pilot to know exactly what mode the aircraft is operating in or else the question arises, "What's it doing now?"

Isn't it one of the basic skill needed for one wanting to be rated for a specific type? What makes you think that many FBW pilots don't know exactly in what mode their aircraft is operating?
Blah .. blah ...
So .. when read all this .. my feeling is:
The pilots were rated on type ... but nevertheless were not qualified for the situation of AF447 was
They had not knowledge of basic flying skills
They don't know how the Airbus systems work
So we can conclude that:
The formation and training of those pilots is very low
So Air France bear all the responsibility for this accident by not providing adequate training to their pilots or not detecting by exams (simulator) that those pilots were not qualified for fly a Airbus A330
At least and even if this above is not entirely true .. Air France stay bear the responsibility of this accident as the contract between Air France and their passengers was to transport them from A to B and they failed....
Are my feelings good ?
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Old 11th Jul 2011, 10:12
  #66 (permalink)  
 
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Machinbird re trim wheels - thank you for clarifying that. I must have missed that even though I make a point of reading PJ2's postings extra carefully. Alzheimers must be setting in.
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Old 11th Jul 2011, 10:17
  #67 (permalink)  
 
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jcjeant, the PF and PNF were brought up belted to their seats according to BEA press releases.

The releases declared:
* They pulled up two bodies.
* They pulled up the two pilots seats.
* They DNA identified the pilots.

Ergo, if the two bodies were not in the seats or very near them, who was and why were they dumped from the seats? (And if they were not in the seats I wonder how they came out considering how they are strapped in. It's not a passenger style seat belt. The pilots use full harnesses.)
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Old 11th Jul 2011, 10:23
  #68 (permalink)  
 
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BOAC, on the graphs I am in agreement with you. And I believe we are in agreement with gums about the word "protections." The word sets up the wrong mindset leading to people getting reckless and cavalier about deadly serious subjects.

Re FBW - you could have (and did) fool me. You seem dead set against AirBus despite its superior safety record. And as far as I know for transport aircraft though the A340 that AirBus has embraced the automation more than other airlines. So I drew the conclusion you rather disliked FBW and software anywhere on the plane, except perhaps in the inoperative laptops the SLF carried on board. You have been busy ripping software engineers a new set of orifices it seems.
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Old 11th Jul 2011, 10:56
  #69 (permalink)  
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Originally Posted by JD-EE
You have been busy ripping software engineers a new set of orifices it seems
- not quite sure w t f that means but it sounds like something my mum would not like me to do. I suspect we move in different social circles.

I see you have not contributed to my thread at all so I suspect the Alzheimers has prevented you from reading the opening post too, or maybe you forgot you read it?
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Old 11th Jul 2011, 11:33
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This video on the loss of the X31 back in the nineties - it was suggested a disconnected probe (and ice) was the fault!

It too went straight up!!


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Old 11th Jul 2011, 12:44
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Originally Posted by JD-EE
AirBus superior safety record
I am not aware of anything like it ... ?
The pilots use full harnesses
Anywhere below 10000 feet but rarely at cruise level.


Originally Posted by takata
Right, the PF achieved a full stall with the help of the side stick, thrust and THS trim. Hence, what's wrong with the side stick, the thrust lever and the THS trim?
Takata, if you are asked to fully stall your aircraft for exercice, would you still trim up past the early signal of the approaching stall ?
Why automation has been doing something you would not ever do yourself ?
IF ... the pilots were confused enough to maitain NU inputs, was it necessary for the automation to help them in their confusion ?
Leave on their shoulders that kind of initiative.


Originally Posted by PJ2
As I have said, this wasn't an emergency such as a depressurization, an engine failure or fire or a GPWS event which requires timely, immediate action but it did have two memory components to the drill, (as shown in the BEA Interim Report #1), before the UAS QRH Checklist was to be called for. I have discussed this memorized drill and checklist a number of times on previous threads.
PJ2, I am unconfortable with your view here.
You have not adressed my concerns.


Originally Posted by DozyWannabe
If you hate the Airbus FBW flightdeck so much ...
You are WAY out DW, and should know better ...
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Old 11th Jul 2011, 13:15
  #72 (permalink)  
 
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TE plots

mm43;

Thanks for your superb graphics work enhancing the crude EXCEL graphs I posted here, and for posting your graph on this thread.

Originally Posted by BOAC
One further comment - I am concerned that these 'graphs' produced after hours of hard work by folk like MM and A33 will pass rapidly into the 'factual' world - as pseudo FDR traces - when in fact they are supposition - guess-work - based on extremely limited information. We just do not know enough at this time.
Of course you are quite right. My 'pseudo FDR traces' are to some extent 'supposition - guesswork', but I don't understand your concern. I thought that, while we're waiting for the publication of the real FDR traces and many posters discuss AoA's, pitch angles, airspeeds etc., this was better than nothing.

Perhaps it would help to explain in some detail how the data shown on these graphs have been derived. In this 'computer simulation' (an EXCEL spreadsheet) the airplane manoeuvre is driven entirely by an assumed variation of acceleration (az/g) along the earth vertical that is shown here. At first, that driver function is just a wild guess. But then the resulting v/s, altitude, airspeeds, AoA, etc., is compared to the data in the BEA Update, including the time line, and the input function is 'massaged' to improve the goodness of fit, and the same process is repeated. After a large number of iterations I felt that 'version 4' is as good as it will ever get until we get the real data.

The calculated parameters are derived from the 'driver' function az/g by strict application of flight mechanics (i.e. Newton's laws) and A330 aero data published by Airbus (where available(*)). (**). The calculation then goes as follows: V/S is calculated from (by integration of) az/g. Altitude is then calculated similarly from V/S. Subtracting altitude from total energy yields kinetic energy and hence TAS, CAS and Mach. V/S and TAS together yield FPA. Next lift coefficient CL is calculated from weight, normal load factor n, Mach and altitude. CL and Mach yield AoA from the aerodynamic data (*). Finally, pitch angle is calculated as the sum of AoA and FPA.

For what it's worth, until we get the real FDR traces ...

(*) The available data cover the operating envelope between Mmo and buffet boundary. There are no data close to the stall and beyond. For these conditions I have assumed a pitch angle of between 15 - 16 degrees and calculated AoA from Pitch-FPA. Whenever I quote a stall-AoA, it is based on what I think is a reasonable extrapolation of the available data.

(**) This means that, if the airplane is subject to the assumed az/g, then it must follow the derived data shown on these graphs. In other words, the data shown are mutually consistent.

Last edited by HazelNuts39; 11th Jul 2011 at 13:30. Reason: Footnote (**)
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Old 11th Jul 2011, 13:45
  #73 (permalink)  
 
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Originally Posted by Chris Scott
Are you sure the sidesticks are not visible from the P3 seat, even if you lean forwards? They are on the A320.
You are correct Chris, but you still need favorable conditions :
  • P3 not in the usual aft position
  • Tray table stowed
  • Adequate luminosity





What I'd like to emphasize on is the following :
IMO, fully visible control columns are a natural and easy Gold mine of valuable information. That free information is lost with the sidestick philosophy as implemented by Airbus.

People here pretend that one sidestick was maintained full NU for 30 seconds ... Were the PM and Captain aware of that situation ?
Never with fully visible control columns, such critical information could have been missed.


Originally Posted by A33Zab
Disagree, the THS indication will be covered by the trim wheels from P3 seat.
...
Sorry Chris, still not convinced, maybe (for A330) if you ask P1 or P2 to move to the side and lean forward L or R from P3 seat?
As stated by Chris Scott and PJ2, I can confirm that it is possible to get that information from P3, and so without P1 or P2 concourse :





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Old 11th Jul 2011, 14:04
  #74 (permalink)  
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[quote+HN]but I don't understand your concern.[/quote] - I obviously did not express my 'concerns' simply enough. I have no issue with the hours of work folk have done on these images and they are 'interesting'. My concern is that they will inevitably become 'fact' and we will be again be plastered in posts similar to those resulting from the Meteosat images '"See - they flew straight in to a big red thunderstorm"etc etc. As long as everyone remembers that these 'graphs' are NOT from the FDR we will be ok.

However, it won't be long before we see- "since they had xxxx at 02:xx:xx (from the FDR trace) then surely yyy"

mmciau - interesting clip I had not seen before - secondary cause of accident - ?
"pilot ignorance of an option to override computer control". No, I mustn't.
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Old 11th Jul 2011, 14:05
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@ Machinbird,

Thanks for the post and page correction on The Shadow's post. I guess a couple of posts were removed after I made a note of it, leading to my error.

Last edited by Turbine D; 11th Jul 2011 at 14:07. Reason: Spelling correction
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Old 11th Jul 2011, 14:16
  #76 (permalink)  
 
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Hi BOAC,

"pilot ignorance of an option to override computer control". No, I mustn't.
I just wish AB had fitted such a switch.
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Old 11th Jul 2011, 14:19
  #77 (permalink)  
 
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Originally postted by Confiture :
would you still trim up past the early signal of the approaching stall ?
Why automation has been doing something you would not ever do yourself ?
IF ... the pilots were confused enough to maitain NU inputs, was it necessary for the automation to help them in their confusion ?
+1

1) how on earth can a "system" allow the THS to go to full 13 up in cruise at 35.000' ?

2) how on earth can a stall warning be disabaled below 60 Kts to just kick in again when control is being regained (and completely confuse the poor crew) ?
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Old 11th Jul 2011, 14:28
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A couple of comments that call for a rejoinder.
The problem with the trim is that it moved to a high aircraft nose up setting without crew awareness.
Crew awareness of nose attitude begins, in instrument conditions, with the artificial horizon/attitude indicator. If that was working as advertised (no data to date suggests it was not) then the primay scan instrument should have given PF and PNF (and later Captain) indications of where the nose was relative to "level flight." Instrument Flying 101.
It appears that a FBW aircraft requires the pilot to know exactly what mode the aircraft is operating in or else the question arises, "What's it doing now?"
True of most modern aircraft (to include modern helicopters that aren't FBW, but do have a lot of redundant and overlapping flight control systems and related degraded modes)
Example is the SH-60 Seahawk:
From all things (and A/P such as it is) on (AFCS on) you go to AFCS off, then Trim Off, then SAS off (SAS 1 and / or SAS 2) then Boost off. You are still flying, but in each case you can do some things, and can't do others. The aircraft also gets a bit more "touchy" to handle, and pilot workload goes up. The last puzzle piece (which means you are having a very bad day) would be if your Boost was off and you then got a horizontal stab miscompare, which forces you into manual control of the stab. When working in fully functional mode, it is that aircraft's sole FBW control surface.
Graceful degradation? I guess so.

The Control Laws of A330 may or may not be as graceful in degradation, but the aircraft itself is a bit more complex, not the least due to the requirement to manage fuel and CG via various fuel transfer protocols.
Also there are more A/P functions and, more FBW involved. I have once again walked my way through the degraded modes. They make sense.

I guess that they make sense to A330 pilots, particularly if you get to practice them in suitable training environment. Nothing like some practice and a few "hell sessions" in a sim to get you to know your systems.

Regardless of which bird you fly, you really have to know your systems.

The more systems, and the more they interact, the more you have to know. Enter your company, and the manufacturer, and their training material, and the training programs.

Those last are critical elements in how well any crew understands their aircraft.
In the case of the AF447 crew, they had no attention to spare to consider what the trim might be doing, thus the nose up demands caused the trim to run silently to a high setting without the knowledge or anticipation of the crew.
Crew awareness of nose attitude begins, in instrument conditions, with the artificial horizon/attitude indicator. If that was working as advertised (no data to date suggests it was not) then the primay scan instrument should have given PF and PNF (and later Captain) indications of where the nose was. Instrument Flying 101.

jcjeant:
So Air France bear all the responsibility for this accident by not providing adequate training to their pilots or not detecting by exams (simulator) that those pilots were not qualified for fly a Airbus A330
All? Outside of the cockpit, there are three non trivial and overlapping bodies who influence how well prepared a crew is for their missions.
The airline
The aircraft manufacturer
Regulating bodies

The rule sets and information each of these bodies issues to guide, restrict, limit or otherwise influence expected pilot behavior is subject to omission or error. AF has a share of responsibility, but for you to say "all" is an overstatement.
At least and even if this above is not entirely true .. Air France stay bear the responsibility of this accident as the contract between Air France and their passengers was to transport them from A to B and they failed.... Are my feelings good
I suppose that from a "strict liability" point of view, that's one way to look at the accident: breach of contract to carry from point A to point B.

Looking at it that way doesn't get one any closer to addressing the sysetmic issues that are under the conginzance of

The airline
The aircraft manufacturer
Regulating bodies

Therein lies the remedy to avoiding such a mishap in the future.

Last edited by Lonewolf_50; 11th Jul 2011 at 14:41.
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Old 11th Jul 2011, 14:35
  #79 (permalink)  
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TD good morning,

More than shifting the (at the time) fascination with sea bottom debris arrangement to AD disagree precursors, Shadow's post is illuminating. Airdata that became discrepant is assumed to be the cause of the accident, how did it come about? He introduces the concept that this phenomenon may have an actual beginning, and it may not be the "So, we have lost the Speeds"...

It has been addressed before, but not to the extent that people may include it in their concept of the progression of failures that brought 447 down. The direct cause of ICE in Pitots is considered to be microcrystalline particles. If in the area of some well distributed solid particles, it is reasonable to conclude the tubes may ingest these at some conforming rate. The Three tubes were "identical" in nature, differing perhaps in the degree of corrosion the drain holes had experienced in service. Dependent on the concentration and rate of uptake, it is logical to assume the Air Pressure differential migrated lower over time, indicating an airspeed that was progressively lower than actual value.

As the speeds declined, the ship would accommodate the "loss" of speed by increasing power, since energy needs to be added and altitude needs to remain the same, but as the a/c climbed anyway, (the energy was actually just right, the computer found it to be low because of ICE), the Nose would be lowered. This might continue until the a/c was zipping along at its assigned cruise level carrying too much power and actual velocity. Depending again on the rate of uptake, this false trimming would last until the a/c autopilot checked out, unable to control the Nose "hunting for a satisfactory Pitch". (AutoPhugoid?)

That is merely a hypothesis, BEA have not addressed through their data any such thing. Neither have they favored ICE as the reason for UAS, to my knowledge.

Autotrim. Takata is correct, of course. Except for one thing. The THS is a very large surface and can control Pitch without as much steady pressure as required by elevators alone. For this, the a/c pays a price in Response.
The Horizontal surface is powerful because it is large. Large things move more slowly than smaller things. To think that it is desirable that when a pilot needs response, he is awarded Power instead, and that lagging the possible cycles of deflection necessary, misses the point. By the time TRIM has "helped" it is not needed, and it becomes a handicap in the ability to maneuver. (AutoPhugoid?) At a/p loss, was it dropped because the Pitch oscillations were too great? Did the PF "chase" the THS all the way up to STALL, trying to get the nose down while still in the aft area of the BackStick? Unable to see THS deflection, would he be able to sense the lack of ND he wanted, thinking that at "neutral" stick, it was no such thing, just a steady increase NU? Who wants to chase TRIM all the way up to ballistic? Bottom line. Why Autotrim in dire circumstances. Obviously available, even mandatory, who needs it?

Needless to say, given the size of the THS, quick movement puts large mechanical demands on the surface, and the jackscrew that accomplishes the deflection. For the pilot to have considered that the THS was "AutoHelping" he would also need to determine that it was also a hindrance. Operating an airbus with the certain knowledge that the a/c was creating a problem is not perhaps in the cerebral databank of its operator. Likewise, the Manual Trim as safety device. The airbus needs a safety device? This may be too subtle for normal flight, but in the tall weeds it may have been a factor.

At the risk of parsing too closely, In the audio where the pilots are noticing "No indications", is it surprise one senses? Or Betrayal?

Last edited by bearfoil; 11th Jul 2011 at 14:48.
 
Old 11th Jul 2011, 14:58
  #80 (permalink)  
 
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Originally Posted by bearfoil
Dependent on the concentration and rate of uptake, it is logical to assume the Air Pressure differential migrated lower over time, indicating an airspeed that was progressively lower than actual value.

As the speeds declined, the ship would accommodate the "loss" of speed by increasing power, since energy needs to be added and altitude needs to remain the same, but as the a/c climbed anyway, (the energy was actually just right, the computer found it to be low because of ICE), the Nose would be lowered. This might continue until the a/c was zipping along at its assigned cruise level carrying too much power and actual velocity. Depending again on the rate of uptake, this false trimming would last until the a/c autopilot checked out, unable to control the Nose "hunting for a satisfactory Pitch".
One hopes that some more research (NASA still working on this?) will shed light on the degradation rate, or mode. (Then again, there are those Goodrich probes ... )

Bear, in a curious way, the elevator and THS work together like Charlie Kaman's servo flap/rotor blade lashup in the old SH-2, and the current KMAX, helicopter. What you end up doing is using a small airfoil to change the pitch of a larger airfoil until equilibrium is reached.
Take a look at this picture.
http://upload.wikimedia.org/wikipedi...0px-N267KA.JPG

That little tab near the end of the rotor blade is the servo flap. The pilot's inputs via cyclic (stick/sidestick analogue) moves the servo flap, which changes camber of airfoil (blade) which aerodynamic forces then resolve into a new pitch angle. (The difference in actual function, and where the two are not the same, is in the moveable THS in an airliner being internally adjusted (motors and hydraulics) to a new position to reach the new stabilized position based on the change induced by elevator movement, rather than how the KMAX does its thing by harnessing fluid flow effects).
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