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AF 447 Thread No. 7

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AF 447 Thread No. 7

Old 31st Mar 2012, 16:39
  #1121 (permalink)  
 
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I agree.
But I was trying to follow the Sim Stall and thinking " What if, at apogee PF HAD suddenly realised ( At Last ! ) we are stalling...Merde.... And PJ2's experience on the Sim might be..."
I should have been clearer.


OK465
The oil pressure instrument on my car is backed up by an oil pressure warning light which comes on if the usual pressure is missing.
Similarly the THS could have a warning when it exceeded certain a figure. This might have made it easier for any of the three pilots to notice and wonder why.

LT.
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Old 31st Mar 2012, 16:41
  #1122 (permalink)  
 
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Salute!

No problem, Doze. I need to express myself more clearly and referring to a post you made a year and a half ago.

- By "feel" and "touch" I am talking about vibrations, noises, thumps and bumps, and even the airframe shaking so badly that it's hard to read the instruments. Ask Retired about flying the F-4 at high AoA.

I am not talking about "artificial" feel in the controls. You know, springs, dampers, bobweights, etc.

Really good pilots will KNOW when something is not right. They might detect a different noise from the motors. They might feel a vibration that wasn't there a second ago. In other words, they are tuned to the aircraft, regardless of the flight control implementation. (On private, ask me about one day I "felt" something and saved the jet)

- The disregard of AoA by the 'bus system in some modes bugs me. I fully appreciate that at very low dynamic pressures, the AoA sensors are close to useless. But seems to me that the 'bus ignores the AoA when the "system" determines that airspeed is invalid, or speed too low. Sad, because the wings certainly know if they are stalled, so the sensors should still be valuable if the crew is in doubt.

So I was not clear about "override". You are correct. The system allowed the pilot to exceed the stall AoA and the pilot may have still thought that he couldn't stall the jet.

Interestingly, our first operational FBW jet ( over 4,000 built) even "protected" the pilot from overriding the system limits until AoA was over 30 degrees. Then we could manually control the horizontal tail and "rock" outta the deep stall by holding a switch with one hand and rocking with the other hand on the side stick.

++++++++++++

I fully agree with Doze and others ( last paragraph of his last post). Why the pilot pulled back and then held the stick back for so long is a mystery. My opinion is he was more concerned about overspeed initially, but after that......

Gums
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Old 31st Mar 2012, 17:02
  #1123 (permalink)  
 
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HazelNuts39

Howdy. Is there any possibility at all that RHS was following in his scan the V/S (SELECT) at 5000fpm descent at a/p loss, confused it with the Nose Down he saw at takeover, and imprinted it in his initial S/A? Therefore the NU?

Perhaps Farley can explain how difficult it is to hover the Harrier. A friend tells me its like doing jumping jacks on a bowling ball. I tend to use that thought when I envision a/p loss on 447. It was difficult.

Flight is a continuum, one takes a break from the flow at great risk. I try not to be too dismissive of how difficult it turned out to be.

As to the DFDR/CVR contents? To consider any part of it to be "off limits" to anyone with appropriate expertise is to deny the concept of a Democracy.

Especially at Court. The Plaintiff is denied access, whilst the defendant has a copy on the coffee table? Please, some perspective.

Hi Dozy.
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Old 31st Mar 2012, 17:03
  #1124 (permalink)  
 
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Originally Posted by gums View Post
Really good pilots will KNOW when something is not right. They might detect a different noise from the motors. They might feel a vibration that wasn't there a second ago. In other words, they are tuned to the aircraft, regardless of the flight control implementation.
Yeah, but you can't design airliner safety concepts around the assumption that the pilots will be "really good". Average ability must be assumed, alongside failsafes to catch pilots having a "below average" moment.

But seems to me that the 'bus ignores the AoA when the "system" determines that airspeed is invalid, or speed too low.
It doesn't "ignore" AoA during UAS, otherwise Stall Warning wouldn't work. It can't use AoA data for protections during UAS because the redundancy calculations are defeated. Low airspeed is a tough one. As was the case a while back, I'm prepared to bet that similar cut-off points are used on most modern airliners, not just Airbii.
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Old 31st Mar 2012, 17:05
  #1125 (permalink)  
 
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mm43;
The "high frequency component of an amplitude increasing to until about 0.1 g peak-to-peak,"(...) "vibrations that might correspond to buffeting" that BEA speaks about on pages 43-44 have a period of about 0.5 seconds.
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Old 31st Mar 2012, 17:14
  #1126 (permalink)  
 
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Doze.

@DozyWannabe
Yeah, but you can't design airliner safety concepts around the assumption that the pilots will be "really good". Average ability must be assumed, alongside failsafes to catch pilots having a "below average" moment.

That is precisely the beginning of the Hamster Wheel that will perpetuate these wrecks. The Spiral of "Better Automation", "Diminished Ability".

Do you see the connection?
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Old 31st Mar 2012, 17:35
  #1127 (permalink)  
 
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Originally Posted by Lyman View Post
Howdy. Is there any possibility at all that RHS was following in his scan the V/S (SELECT) at 5000fpm descent at a/p loss, confused it with the Nose Down he saw at takeover, and imprinted it in his initial S/A? Therefore the NU?
Not really, because you just cross-check with the altimeter, and as long as it's not unwinding drastically, you rationalise the V/S display as a turbulence-related blip.

Perhaps Farley can explain how difficult it is to hover the Harrier. A friend tells me its like doing jumping jacks on a bowling ball. I tend to use that thought when I envision a/p loss on 447. It was difficult.
Difficult, yes - but as difficult as hovering the Harrier? I don't think so. The Harrier is notoriously tricky to control in hover as it's not very stable and you're only about 50ft or so off the ground, whereas the A330 is *extremely* stable, and in this case was handed over at cruise altitude, with a reasonable speed setting. The AF447 PF could in all likelihood have kept his hands off the stick and nothing untoward would have happened.

As to the DFDR/CVR contents? To consider any part of it to be "off limits" to anyone with appropriate expertise is to deny the concept of a Democracy.
This isn't about denying content to those with appropriate expertise, it's about air accident investigation *needing* to be a special case to prevent possible further accidents between the time of the accident and the court case. I was accused of naivete on the other thread for saying that Airbus had to be given the FDR data for technical reasons and not for the benefit of their legal team. I'm sure their legal team have seen some of it, but until the final report is released and the trial begins, I don't think they'll have looked into anything the BEA consider non-relevant (and remember, the distinction of relevance is made by the BEA, *not* Airbus).

It's also interesting that you use "Plaintiff" and "Defendant" in that manner - strictly speaking, the crews' families, Airbus and AF are what Anglo law would consider co-defendants. With the evidence as it's laid out in the 3rd Interim Report, it seems that all three are likely to come in for a degree of censure - mishandling and poor CRM for the flight crew, failure to expedite replacement of the Thales pitot tubes for AF and Airbus, and poor management and training practices on the part of AF.

I've said my piece on automation elsewhere. Automation is a tool, nothing more - if that tool is being used to skimp on training and development of handflying, then it is the fault of those using automation for that end, bot automation itself.
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Old 31st Mar 2012, 17:55
  #1128 (permalink)  
 
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Cool

Hi,

Gums
Really good pilots will KNOW when something is not right. They might detect a different noise from the motors. They might feel a vibration that wasn't there a second ago. In other words, they are tuned to the aircraft, regardless of the flight control implementation
Indeed ... A good example is the pilot Hans-Joachim Marseille "The Star Of Africa"
He flew with gym shoes instead regulatory boots
He has said to Willy Messerschmitt:
I made ​​one with my plane .. I must do no more to focus on instruments .. all my concentration may well be on my target

It's also interesting that you use "Plaintiff" and "Defendant" in that manner - strictly speaking, the crews' families, Airbus and AF are what Anglo law would consider co-defendants
The court of justice in charge of the case is located in Françe and apply french laws .. not Anglo laws

Last edited by jcjeant; 31st Mar 2012 at 18:05.
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Old 31st Mar 2012, 17:59
  #1129 (permalink)  
 
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Re, "How do you train aoa instrumentation if it is never to be used unless in upset!"

Originally Posted by PJ2
Precisely.

There is far more to this suggestion than just installing the guage.
The natural place to be using AOA is on approach. That is where to begin training to use it. Once the indication is worked into your scan, you can begin to use it elsewhere in the flight envelope.
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Old 31st Mar 2012, 18:13
  #1130 (permalink)  
 
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Originally Posted by jcjeant View Post
The court of justice in charge of the case is located in Françe and apply french laws .. not Anglo laws
I'm well aware of that, I was just making the point that Lyman's insinuation that the non-release of raw FDR data to the public and/or the crew/family lawyers was equivalent to the prosecution withholding evidence from the defence in a criminal trial was false.
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Old 31st Mar 2012, 18:32
  #1131 (permalink)  
 
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Learning curve

Hi,

PJ2:

There is far more to this suggestion than just installing the guage.

Due it's importance (to the wing "function") i think it "self teaches". And (perhaps) should be used in training.

I admit, it collides with Airbus SAS philosophy of "stall prevention" through "protections".

But (may play an important role) can be vital in (rare) extreme cases.

Mac

(Controversial, )
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Old 31st Mar 2012, 18:42
  #1132 (permalink)  
 
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Trend?

Hi,

Bear:

Important point!

Mac

PS

Is training capable to "prepare" when applying this approach (to the limits)?
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Old 31st Mar 2012, 18:50
  #1133 (permalink)  
 
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@DW

QUOTE
I'm well aware of that, I was just making the point that Lyman's insinuation that the non-release of raw FDR data to the public and/or the crew/family lawyers was equivalent to the prosecution withholding evidence from the defence in a criminal trial was false.UNQUOTE

[B]NO[B] In juris civile, Plaintiff and Defendant are no less adversarial. Perhaps more so. "NON RELEASE". That means what, like "Withheld?"

Witholding evidence can be charged in itself as a felony. Even a jurist can be recalled for indiscriminate actions.

Let me ask a non threatening question, Doze. Say you are in Upset, and you see your Pitch as 7 degrees. You have no idea your AoA, it is at 40 degrees. You ok with that? Any problem? You cannot suss anything of help, and your g is around "1". Still ok? Right, AoA is ok in the computer quiver, but not in the Pilots'?

You seem to have forgotten that at the time of this UAS, Pilots were told to Disregard the STALL WARN. Also, the a/p was not yet accused of "Uncommanded climb".


Also @DOZEWANNABE:
(FBW) "It doesn't "ignore" AoA during UAS, otherwise Stall Warning wouldn't work."

Can you say that the SW did work? Evidently not, and for the same reason the pilots could not Suss the STALL. The AoA was not available. Could one explanation be that the pilots did not even acknowledge the WARNING because they all tacitly took it to be bogus? You have a better question than "How could they ignore the STALL WARN?"

Last edited by Lyman; 31st Mar 2012 at 19:01.
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Old 31st Mar 2012, 18:58
  #1134 (permalink)  
 
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Lyman,

Read my post in the other AF447 thread regarding release of information...

TD
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Old 31st Mar 2012, 18:59
  #1135 (permalink)  
 
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Originally Posted by Lyman
HazelNuts39: Howdy. Is there any possibility at all that RHS was following in his scan the V/S (SELECT) at 5000fpm descent at a/p loss, confused it with the Nose Down he saw at takeover, and imprinted it in his initial S/A? Therefore the NU?
Maybe you should ask a pilot which I'm not. The trace of V/S Selected on page 111 prior to A/P disconnect shows 0 fpm with regular 'spikes' to -5000 fpm (the much debated 'zipper'). After A/P disconnect the spikes disappear and the trace shows 0 fpm for about 15 seconds and then starts jumping up and down to +5000, -5000, +5000, 0, +11000 where it remains for about 20 seconds.

The FD was not available immediately after AP disconnect, but briefly reappeared about 10 seconds later.

I'm afraid I don't understand your question.
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Old 31st Mar 2012, 19:03
  #1136 (permalink)  
 
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Thanks TD I have. Both you and Dozy are absolutely correct. Save one: At its completion, the Final Report is not given to the Judge, it is provided EASA, isn't it? Thence to parties deemed important by the authority. BEA has no power, they are "Party to" ?

HazelNuts39. Sorry, I just wanted to know your opinion re: its availibility to PF, not his reaction to it. Your response is perfect. From it, I conclude the zipper may have held his attention as to V/S and influenced his inputs, perhaps well into the "climb". My opinion only.

Further, the display of V/S select, appearing (post a/p loss) "erratic", may actually have been accurate, but further confused the pilot as to his "climb".

I only suggest that the "zipper" can't just be discarded as irrelevant.....
Had he not judged his V/S accurately, how was he to suss his actual ROA?
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Old 31st Mar 2012, 19:11
  #1137 (permalink)  
 
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Key points

Hi,

PJ2:

Therefore, a "practically impossible" stall recovery, given the "environment" they were in and their "possibilities" to tackle the task.

"Why the initial pitch-up?", and "Why wasn't the stall warning heeded post-apogee?"
You are assuming this will be only "understood / explained" by HF study results?

Mac
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Old 31st Mar 2012, 19:16
  #1138 (permalink)  
 
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Back to AoA one mo' time

Salute!

@ Doze:

Redundancy is required, no problem with that. OTOH, graceful degradation is also required. So why throw out the one sensor that actually indicates the ability of the wing to provide lift or lack thereof? By the time the AoA sensors are invalid I can guarantee that the plane's wings aren't providing useable lift doofers.

'bird has it right. Start off using the AoA for approaches, as it inherently compensates for weight and such to provide the best aid in the cockpit.

Being a USAF jock, we used a baseline speed and added knots for fuel weight and such. The U.S. Nasal Radiators used the AoA indexer lights and such. So I was impressed once flying the A-7D, which was a Navy design which the USAF adopted and improved. Gotta tellya that an approach was much safer and easier than what I had been used to.

Sure, a good crew will compare the speed based upon weight with the AoA, but once close, AoA was the primary aid for an approach.

Once gear up, our Viper AoA "bracket" went away. Due to our operational requirements and design of the FBW system, pulling full back gave you the best AoA for the gee you were commanding. By the time you reached the max AoA you were in one Gee flight ( we hit 9 gees at 15 degrees).

For the 'bus, I can see an AoA indication in cruise configuration that is small and basically unimportant. But when the system starts to revert to backup modes, then the thing might be the best friend you have, especially for a pitot-static problem. And then there's the flight path marker (FPM) produced by the inertial system, which show exactly where the jet is going without regard for any aerodynamic sensors.

I can not imagine seeing the FPM at the bottom of the indicator or HUD and not thinking about being fully stalled while holding back stick, can you?

Gums
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Old 31st Mar 2012, 19:18
  #1139 (permalink)  
 
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Originally Posted by Lyman View Post
From it, I conclude the zipper may have held his attention as to V/S and influenced his inputs, perhaps well into the "climb". My opinion only.
...
I only suggest that that the "zipper" can't just be discarded as irrelevant.....
Had he not judged his V/S accurately, how was he to suss his actual ROA?
Having now spent time in an A320 simulator, I can tell you that in MANAGED mode, the corrections applied by the autopilot are displayed in that window. "-5000" appears, but only for a fraction of a second as the slight corrections are applied. I'd be very surprised if that interrupted his instrument scan (of which the FCU display should only be an occasional part) and led him to conclude they were descending for two main reasons.

1. They are a regular occurrence in MANAGED mode, and lots of corrections are expected in this scenario. He may have been relatively low-hours for an airline pilot, but this is one scenario where spending a lot of time with the automatics in would have led him to discount that as anything to worry about.

2. He did not start climbing until the automatics disengaged, at which point (as you'd expect), the "zipper" stops.
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Old 31st Mar 2012, 19:26
  #1140 (permalink)  
 
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Why the initial pitch-up?

Hi,

Considering we fly near the "corner" i ask:

Why not to implement (ASAP) a "resource" to indicate Stall type.

The system (IMHO) is able to process and inform reliably on low speed or overmach stalls.

Thiells 727 man machine interface mislead 3 crew. (Redundant misleading of Climb and Alt)

Current Systems, it seems can indicate precisely Stall type:


Why the pilots (sometimes near the corner) should only guess?

Mac

This "guessing" (wrong) probably was the most important factor in AF447 loss.

Last edited by RR_NDB; 31st Mar 2012 at 23:49. Reason: Add gums comment in subsequent post
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