PPRuNe Forums AF 447 Thread No. 9

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18th Jul 2012, 07:27   #521 (permalink)

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@ Clandestino,

Post #477
"From the CVR report:
02.06.54 the crew say "Minus forty-two we won’t use the anti ice that’s a plus."

There are very few TAT recordings reported.
However, please see the report published in July11, page 86.
Time 0hr.09min FL. 349.92 Static temperature (°C) -43.5
Time 2hr.10 FL 350.44 SAT -38.8"
Quote:
 by Clandestino Originally Posted by rudderrudderrat Time 0hr.09min FL. 34.992 Static temperature (°C) -43.5 Time 2hr.10 FL 35.044 SAT -38.8 (...) The SAT has warmed from -42°C to -38.8°C over a very short time. That "very short time" was two hours.
@ 02.06.54 the crew observe the SAT as -42°C
@ 02.10.00 (Interim report July11 page 86) SAT -38.8
By my maths, I make that 3 minutes and 6 seconds,
How do you make it two hours?

Edit.
Quote:
 However, from DFDR data it can be seen that aerodynamics were not enough to keep AF447 stalled; at about 2:11:45, THS is winding up and is 2-3 degrees shy of full nose up, elevators are fully nose up, as trust levers get retarded N1 goes down and nose drops from +15° to -10°.
The aircraft had 45° angle of attack.
Even if the nose was lowered by 25° I still make that 20° angle of attack.
Do you still think that that "aerodynamics were not enough to keep AF447 stalled"?

Last edited by rudderrudderrat; 18th Jul 2012 at 07:38.

18th Jul 2012, 08:02   #522 (permalink)

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Quote:
 @ 02.06.54 the crew observe the SAT as -42°C @ 02.10.00 (Interim report July11 page 86) SAT -38.8
Thanks for these times Rudder. So using these data points, TAT was increasing at the rate of 1 degree per minute. Similar to the rate of increase with routine descent. You would expect the climate control to cope with this without the cockpit becoming uncomfortably warm.

So why did PF note at 2.08.47 that "You can feel already that it’s a lot hotter"

And why did PNF agree at 2.09.20 that "It’s amazing how hot it is all of a sudden"

It certainly doesn't sound normal or routine.

In fact, the increased temp is pretty much the last thing that PF and PNF ever agreed on.

18th Jul 2012, 09:22   #523 (permalink)

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Quote:
 In fact, the increased temp is pretty much the last thing that PF and PNF ever agreed on.
I agree with you on their comments, but when viewing the FDR printout it is difficult to detect the change as the graphics have insufficient resolution. One possibility is not so much the temperature, but a sharp rise in the relative humidity which would have created the same feeling.

 18th Jul 2012, 09:23 #524 (permalink) Join Date: Aug 2011 Location: germany Posts: 21 captain. Ithink that pnf was hesitating to take over brcause he was not assigned pilot flying.and it feels like there had been personal issues that bonin was pf.Maybe we should no more about the personality of the captain.pnf had quite a lot experience,so why was he so eager that the captain comes back,instead of taking command and doing the right thing.
18th Jul 2012, 09:24   #525 (permalink)

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Hi gums,

Quote:
 Originally Posted by gums The normal law and the alternate laws are not "attitude" biased as one would expect in the old days of the autopilot "attitude hold" mode. The thing is programmed to hold a gee! In Normal, the pitch attitude is taken into account, so it does not try to hold one perfect gee if in a climb or descent, but whatever gee is required for the pitch attitude. So in some sense, it has an attitude function built in. Once outta Normal, it appears to be strictly a gee command with pitch rates blended. AoA seems absent to any large degree.
Would you be so kind as to elaborate on the bolded sentences? Source and so on?

Why do I ask? Two things:
- AFAIK, stick free the aircraft holds its path, not "1 g". It may be that the path gives 1g (often it is!) but the law is "g demand" (i.e. stick not free) not "g holding".
- I was unable to find any credible document indicating that the stick free longitudinal behavior is different in Alternate law versus Normal law.

Hi rudderrudderrat,
Quote:
Originally Posted by rudderrudderrat
Quote:
 Originally Posted by Clandestino However, from DFDR data it can be seen that aerodynamics were not enough to keep AF447 stalled; at about 2:11:45, THS is winding up and is 2-3 degrees shy of full nose up, elevators are fully nose up, as trust levers get retarded N1 goes down and nose drops from +15° to -10°.
The aircraft had 45° angle of attack.
Even if the nose was lowered by 25° I still make that 20° angle of attack.
Do you still think that that "aerodynamics were not enough to keep AF447 stalled"?
The aerodynamics alone: you don't know. What you may notice is that the THS & elevators, commanding nose up, might have slightly influenced clean aerodynamics at that point.
What you don't know is what AoA will have been reached with thrust idle + stick full nose down and maintained there as long as needed (meaning eventually the elevators and THS would have winded down).
It can't be proven until test flights take place, and we all know there won't be such tests and why. OTOH, all indications so far show the nose would have gone down, down down, and the AoA would have followed.
Therefore I too do think that aerodynamics were not enough to keep AF447 stalled, and that this PoV ('locked in stall') is irrelevant. And it also may be used to used to divert attention BTW (this is not for you, rudderrudderrat, I'm thinking about organisations that have an agenda, out there).

Cheers.

Last edited by AlphaZuluRomeo; 18th Jul 2012 at 09:24.

18th Jul 2012, 09:54   #526 (permalink)

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Quote:
 Originally Posted by slats11 So why did PF note at 2.08.47 that "You can feel already that it’s a lot hotter"
I wonder whether the heat exchangers in the air conditioning packs could be obstructed by ice particles.

18th Jul 2012, 10:25   #527 (permalink)

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Quote:
 Originally Posted by AZR I was unable to find any credible document indicating that the stick free longitudinal behavior is different in Alternate law versus Normal law.
FCOM 1.27.30 Reconfiguration control laws:
Quote:
 Alt 1/2; Pitch control, Flight mode: Flight law is a load factor demand law, similar to normal law, with limited pitch rate feedback and gains, ... Flare mode: Flare law is identical to normal flare law
As I read this, alternate law pitch control is not identical to normal law.

Last edited by HazelNuts39; 18th Jul 2012 at 10:27. Reason: typo

 18th Jul 2012, 10:43 #528 (permalink) Join Date: Aug 2011 Location: Grassy Valley Posts: 2,147 EMIT: "What she said is duly noted in the CVR transcription (at times as noted by previous posters) allo? oui allo? Then no word, but a sound similar to one putting the phone back in the cradle (word or group of words with no relevance to the conduct of the flight)? Then no words but a sound similar to the ending of the cabin interphone communication Needless to say that the pilots were to busy to pick up the phone." If the pilots did not pick up their phone, how did she end up on the Cockpit voice recorder? woodja51 "All the rest is academic , a bunch of folks died due to failure to fly the aircraft " that appears to be the case. However, failure to fly the a/c is a huge topic. Can you include some other evidence? Last edited by Lyman; 18th Jul 2012 at 11:06.
 18th Jul 2012, 11:01 #529 (permalink) Join Date: Mar 2006 Location: australia Age: 48 Posts: 197 Lots of theory! Lots of talk about lots of stuff... Facts: Unreliable airspeed , if aircraft flight Jeopardised , ap at fd off. No more no less Then Stall recovery( if you put it there)... Lower attitude End of event. Simple , problem solved no crash no dead people. All the rest is academic , a bunch of folks died due to failure to fly the aircraft And transit a temporary anomaly. I sympathise with the loss of life , but the race to the bottom in flight training must be to blame at the core of this and is due to airline, manufacturers race to the lowest flight training cost base possible to meet min regs only. It will only get worse with MPL.....but that is the future.
 18th Jul 2012, 11:03 #530 (permalink) Join Date: Aug 2011 Location: germany Posts: 21 There`s one fact in this whole scenario,which is for me the most unbelievable part in the crew-captain relation. we have 2 pilots in todays standard with a lot of experience(doing away for a moment the AF defiences in training we all konw about) flying ong haul for years no city hoppers.they were clueless,desperate,no solutions to solve their problems ,both (?) eagerly awaiting the captains return for relief. And when that moment arrived the cpt back n cp they both are not able to give a professional briefing,the last opportunity maybe to save their lifes.What di they expect from him ? guessing ? Can somebody pls explain that ? This can`t be explained by their mental state only.
 18th Jul 2012, 11:14 #531 (permalink) Join Date: Aug 2011 Location: Grassy Valley Posts: 2,147 I honestly think the actual cause for this accident is at hand. This thread has been three years analyzing incomplete and possibly inaccurate, if not fraudulent data. Stand by. "There`s one fact in this whole scenario,which is for me the most unbelievable part in the crew-captain relation. we have 2 pilots in todays standard with a lot of experience(doing away for a moment the AF defiences in training we all konw about) flying ong haul for years no city hoppers.they were clueless,desperate,no solutions to solve their problems ,both (?) eagerly awaiting the captains return for relief. And when that moment arrived the cpt back n cp they both are not able to give a professional briefing,the last opportunity maybe to save their lifes.What di they expect from him ? guessing ? Can somebody pls explain that ? This can`t be explained by their mental state only." More than one fact. For three years this crew has been allowed to seem consummately incompetent, crazy, or impaired. Would it take much to upset the apple cart? Remains to be seen. Last edited by Lyman; 18th Jul 2012 at 11:16.
 18th Jul 2012, 11:32 #532 (permalink) Join Date: Jul 2009 Location: USA Age: 51 Posts: 28 Capt.'s Return Philip2141 This has always bothered me. When the CVR first came out, some were quick to support PNF as having some concept of the situation but limited by authority and what PF was actually doing. BUT PNF is desperate to get the Capt. back to the flight deck and when the Capt. gets there all he offers is: "What’s happening? I don’t know I don’t know what’s happening" and "We lost all control of the aeroplane we don’t understand anything we’ve tried everything" IMHO, he was not calling the Capt. back due to command issues, which I believe was suggested earlier--he had no idea what was going on? Also, what had they tried? Switch to ATT?
18th Jul 2012, 12:22   #533 (permalink)

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Quote:
 Quote: Clandestino Well... no. Aerodynamically it is stable yet with FBW intervention in ALT2 law, where low and high speed stability are lost (as is expected when there is no reliable speed measurement), it does not become neutral but unstable.
Quote:
 Quote: Gums Wrong. Aero is aero, and the FBW system can only do so much. I do not believe that the jet becomes unstable, only that there is an AoA and cee gee combo that enables it to reach a stable, stalled condition that we did not realize was possible. All the data I have seen shows that the 'bus does not have an AoA/cee gee combination that makes the jet unstable. The intervention by FBW laws, limits, protections can only do so much. In my case, we were actually unstable until about 0.95M. So HAL took care of us, but enabled fabulous pitch rates, sustained turn rates, sustained gee and such that had never been seen.

Well, i´m not sure what you both are getting there, therefore i try to summarize the issue about stability in my own understanding (feel free to correct).

The airframe itself is, no, must be natural positive stable, otherwise it would not be flyable in direct law.

In Nz-Law, which applies in all Laws except Direct Law Ground Law and Flare Law (did i forget one?) the flight control system creates an artificial neutral stability by use of elevators and THS trim, leading to a stable flightpath without SS input. Not the SS drives the elevators, but the flight control system using present flightpath and the demanded change from that flightpath.

Protections are there to keep this flight path stable airframe within the flight envelope, in simple terms to deviate from this ordered stable flightpath when set parameters are exceeded. There are other tasks to be fullfilled by those protections as well, but not of relevance what i try to get at.

When those protections are degraded or lost, we still have an airframe with artificial neutral stability, as the flightcontrol system still works along the demands of Nz Law, but the protections to keep the aircraft within the flight envelope are gone and have to be replaced by the skill of the crew.

In the case discussed here once on the way up to the apogee the Flight Control System was trying to maintain the flightpath with elevator deflection and THS trim blind to the fact (protections lost) that it would run out of airspeed in doing so, will finally stall, as it did. The crew, who should have compensated for those lost protections was most probably unaware of that fact too, otherwise they wouldn´t have continued to apply NU SS. This NU SS had not much influence after the stall happened, as the flight control system was beyond it´s capability to maintain the flightpath (descending already instead of continueing on the ordered climbing trajectory). The SS movement between NU and Level had no effect and showed no reaction to the aircrew, thus it might have contributed to the confusion.
Neutral SS wouldn´t have cured the problem, only ND SS would have changed the trajectory.

What BEA was getting at with the cited paragraph few posts before is imho, to show the reason for this behaviour without getting too much into details.

@ gums my friend in arms, if i remeber correct the F16 airframe was naturally unstable and a diferent beast. Your comment to blend the Nz-Law with the present (and available) AOA value for a backup in ALT laws with normal protections lost seems a reasonable consideration.

Last edited by RetiredF4; 18th Jul 2012 at 12:57.

18th Jul 2012, 12:35   #534 (permalink)

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Quote:
 Originally Posted by Lyman If the pilots did not pick up their phone, how did she end up on the Cockpit voice recorder?
2:10:53,5 A first cabin crew or flight rest facility call (high-low chime) was heard
2:10:55 A noise on track 1 of the CVR, which may be the impact of the microphone striking a panel
2:10:55,9 Track 1: allo?
2:10:59,4 oui
2:11:02,3 allo?
2:11:08,3 noise of someone trying to park cabin interphone handset
2:11:09,8 - 2:11:27 Five call signals to the crew rest facility

18th Jul 2012, 13:14   #535 (permalink)

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Hi HazelNuts39

Quote:
 Originally Posted by HazelNuts39 FCOM 1.27.30 Reconfiguration control laws: As I read this, alternate law pitch control is not identical to normal law.
Thanks, I maybe should have precised that I've read that too ; "limited pitch rate feedback and gains" apply to a manoeuver, i.e. when the crew commands something via the stick.
My question was about the stick free longitudinal behavior. It remains unanswered.

18th Jul 2012, 13:18   #536 (permalink)

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Quote:
 captain. Ithink that pnf was hesitating to take over brcause he was not assigned pilot flying.and it feels like there had been personal issues that bonin was pf.Maybe we should no more about the personality of the captain.pnf had quite a lot experience,so why was he so eager that the captain comes back,instead of taking command and doing the right thing.
Maybe it's because AF culture .......
Quote:
 Extrait du manuel A330/340 d’AF en vigueur à la date du crash : 4.1. MANOEUVRE D’URGENCE Elle est systématiquement effectuée de mémoire selon une répartition des tâches spécifique. Face à une situation qui nécessite de la part de l’équipage une réaction immédiate, le contrôle mutuel devient secondaire sauf dans le cas d’un pompage réacteur qui conduit à une réduction de poussée. C’est toujours le CDB qu’il soit PF ou PNF qui appelle la réalisation d’une manoeuvre d’urgence en annonçant son titre : exemple : “WINDSHEAR TOGA”. Extract from manual AF A330/340 in force at the time of the crash: 4.1. EMERGENCY OPERATION It is systematically carried out according to a memory allocation of specific tasks. Faced with a situation that requires on the part of the crew an immediate response, mutual control is secondary except in the case of a pumping engine which leads to a reduction of thrust. It is always the captain it is PF or PNF called the realization of an emergency maneuver by announcing its title: Example: "Windshear TOGA".

Last edited by jcjeant; 18th Jul 2012 at 13:21.

18th Jul 2012, 13:28   #537 (permalink)

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Quote:
 Originally Posted by AZR My question was about the stick free longitudinal behavior.
As I understand the C* control law:
C* = q + a*nz, where q = pitch rate, nz = incremental loadfactor, and a determines the 'blend' between nz and q feedback.
For side stick neutral C* = 0, hence q = -a*nz

 18th Jul 2012, 13:33 #538 (permalink) Join Date: Aug 2011 Location: Grassy Valley Posts: 2,147 Hi HazelNuts... From EMIT: "Relevant What she said is duly noted in the CVR transcription (at times as noted by previous posters)" What I said: "How can her voice appear on the CVR?" The "allo,Oui,allo" is from Pilot Bonin....
 18th Jul 2012, 13:49 #539 (permalink) Join Date: Aug 2011 Location: Grassy Valley Posts: 2,147 Thermalsniffer... I do not mistrust PNF comment, and I believe he is correct: they tried everything to regain the flightpath. Their problem started at autoflight disable, and flight control disable. Pitch control was unavailable, navigation had been lost, and other problems emanating from a problem in the cockpit area were cascading. Neither pilot understood the scope and hopelessness of their issues. After Captain re-entered the cockpit, he immediately understood the crew were doing what they could, but him taking the controls would be not advisable, what control they had might well be lost if a transfer to him was accomplished. PNF was reluctant to take control, that is why there was no permanent change. There is no chance they didn't have the experience of STALL, and know exactly what was happening...To this extent: They were in trouble, and they had no control over the aircraft...the stick traces were not Bonin's. They belonged to the aircraft. Robert took the stick back as Captain returned, his input had no effect, as Bonin's controls hadn't either...in the climb, Bonin's confusion is not confusion, the a/c is not responding to his inputs. Shortly after 447 was lost, another a/c, a 340, also lost Pitch control... Last edited by Lyman; 18th Jul 2012 at 14:01.

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