Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

AF 447 Thread No. 10

Tech Log The very best in practical technical discussion on the web

AF 447 Thread No. 10

Old 25th Aug 2012, 05:13
  #101 (permalink)  
 
Join Date: Sep 2010
Location: earth
Posts: 1,342
Forgive my direct question but should not the PF maintained wings level pitch and power settings for unreliable a/s. Damn Airbus, seems like both pilots were more concerned with interpreting ECAM failures than flying the damn plane??????Don't think this would happen with analog pilots in an analog aircraft or simply an analog pilot reverting to simple piloting skills. Why would you even trust FD in this event?

I understand the panic in severe turb.

Having said that, I suspect the pitot's froze up due to insufficent heating, possibly as a result of insufficent pitot heat. Wiring, pitot elements.. I question?? Not enough lead in the pencil is my question as the pitot probes go..
grounded27 is offline  
Old 25th Aug 2012, 07:32
  #102 (permalink)  
 
Join Date: Aug 2009
Location: Germany
Age: 63
Posts: 1,809
BUSS requires the 3 ADR's be physically deselected.
This instrument (virtual BUSS) is present and works even when the 3 ADR's are activated
It handles all kinds of protections AOA of the Airbus (Alpha prot .. Alpha floor .. etc. ..) in normal law
This instrument is hidden .. pilots do not see him
The problem is that when the aircraft leaves the normal law ... this (virtual) instrument stops working

Last edited by jcjeant; 25th Aug 2012 at 07:34.
jcjeant is offline  
Old 25th Aug 2012, 10:23
  #103 (permalink)  
 
Join Date: Feb 2008
Location: Edinburgh, UK
Posts: 34
Originally Posted by grounded27
Damn Airbus, seems like both pilots were more concerned with interpreting ECAM failures than flying the damn plane??????Don't think this would happen with analog pilots in an analog aircraft or simply an analog pilot reverting to simple piloting skills.
Why Airbus in particular? Are modern flight decks on other types much different? Did "analogue" flightdecks provide better information in unreliable airspeed situations, for example?

I'm sure I'll be labelled an Airbus "fanboy" by some but, as someone outside the industry, I guess I'm just having difficulty understanding why an incident with a FBW Airbus prompts so many to crawl over the entire design to find fault while similar incidents involving other types (e.g. inappropriate reaction to stall warning, loss of air data) result in more focus on crew actions. Oh well, I'm here to learn.

Originally Posted by grounded27
Having said that, I suspect the pitot's froze up due to insufficent heating, possibly as a result of insufficent pitot heat. Wiring, pitot elements.. I question??
I can't vouch for this particular series of threads but elsewhere the discussions seem to indicate that the Thales pitots used on AF447 met certification standards but not by as much of a margin as the later Thales and the Goodrich pitots. It's also my understanding that there was no indication of any electrical fault.
DL-EDI is offline  
Old 25th Aug 2012, 11:32
  #104 (permalink)  
Moderator
Thread Starter
 
Join Date: Apr 2001
Location: various places .....
Posts: 6,514
Did "analogue" flightdecks provide better information in unreliable airspeed situations, for example?

You're missing the point or misunderstanding the problem a little, I think.

The older style aircraft (which happened to have analogue kit due to the available technology) generally were crewed by pilots who did a lot of hand flying - often raw data (ie without any "helpful" gadgets) - and didn't need autopilots, flight directors, and autothrottles to think for them.

Even with such gadgets, we tended to "look through" the flight director, for instance, and fly much the same as we would without one using the old-fashioned I/F scan processes - the flight director helped a bit by assisting the on-the-fly decision processes but was not followed blindly and without pilot thought.

Hence if an ASI problem arose, we just kept doing what we had been doing without the use of one of the usual set of information sources .. just meant we paid more emphasis to pitch attitude (on the AH or whatever term was used for that installation) and engine thrust settings .. and it all just sort of worked out fine.

However, maintenance of the skills required practise. The risk in modern aircraft is that these skills are lost.
john_tullamarine is offline  
Old 25th Aug 2012, 12:03
  #105 (permalink)  
 
Join Date: Feb 2008
Location: Edinburgh, UK
Posts: 34
Originally Posted by john_tullamarine
You're missing the point or misunderstanding the problem a little, I think.
Fair enough, but my main point of contention is: why "Damn Airbus" rather than "Damn modern flight decks"? Why "Damn Airbus" rather than "Damn modern training that apparently doesn't make appropriate use of pitch and power second nature to every crew in the absence of airspeed data"?
DL-EDI is offline  
Old 25th Aug 2012, 12:21
  #106 (permalink)  
Moderator
Thread Starter
 
Join Date: Apr 2001
Location: various places .....
Posts: 6,514
Oh, indeed .. and you are absolutely correct.
john_tullamarine is offline  
Old 25th Aug 2012, 12:56
  #107 (permalink)  
 
Join Date: Jun 2011
Location: Devonshire
Age: 92
Posts: 300
Mandatory RVSM with its potential lowering of the bottom cruising level makes it difficult for pilots to manually handle their aircraft at cruising levels. It ought to be possible for Air Traffic Control to release aircraft from this requirement for a finite period when and where ATC can allow. Not all airspace is always busy throughout the 24 hours. ( A simple example is the Aeropostal night flights from Paris, when and where much of the area is virtually empty. )
Not all flights are from busy areas or at times when they are busy.
( On another thread someone mentioned that their airline arranged that their pilots did two sessions of manual flying as well as a further couple of sessions in the sim doing all the mandatory stuff, annually.)
Some of the " analog" aircraft tended to have higher weather minima ( when these were laid down, I think, in the 1950s). One Captain used to say that he would overshoot when he saw his F/O "BRACE"... But he may have been joking !

In 1975 when most Jet cruising levels were 2000ft apart, in discussion with the UK Authorities, I was told that they were considering reducing this to 1500ft to allow more flights to cruise nearer their own optimum levels.
Linktrained is offline  
Old 25th Aug 2012, 14:30
  #108 (permalink)  
 
Join Date: Sep 2010
Location: earth
Posts: 1,342
DL-EDI

Not my intent (Damn Airbus) that is. Damn ECAM should have been the statement, it seems like it did more harm than good in this situation. I do feel though that the Airbus ECAM system is like the nagging wife who won't just STFU. It is the pilot's responsibility to fly the aircraft, it seems obvious to me that the PF as John and I had stated was not able to revert to simple pitch and power flight. Disconnect the automation, ignore the flight director.

As for the pitot tubes, I have my doubts. I do know that AB is big on using the smallest gauge wire possible for weight savings. A good heater draws current. Just a suspicion of mine. I will post on eng and tech as I do not have access to A330 WDM's myself. I have been curious what gauge wire the heaters use.
grounded27 is offline  
Old 25th Aug 2012, 14:53
  #109 (permalink)  
 
Join Date: Jan 2005
Location: W of 30W
Posts: 1,939
Originally Posted by HN39
I don't think that I am evading any point of substance. I do have the feeling that, having clarified the facts, our discussion has reached the point were remaining differences are matters of opinion. Regarding matters of opinion, I am always reminding myself that I am an engineer participating in a pilot's forum. If there is a technical point to discuss, please be more specific.
"Do you really believe the PF would have felt the difference in his erratic movements of the sidestick?"

As elevator deflection is proportional to stick deflection, any erratic movements of that stick tend naturally to disappear especially when speed is still high or a price has to be paid on the human body.
Direct law allows the pilot to be more aware of the consequences of his inputs on the stick.

THS at 13 deg instead of 3 deg is an elephant in the room.
Direct law would not have allowed its presence.

Any release of the stick, not to talk about push command, would have provoked an immediate ND change in the attitude.
Direct law would not have allowed to go that easily to the stall and would have favorized an exit from that stall.

"Regarding the captain, the stall warning is loud enough to be heard through a closed cockpit door. The captain must have heard it when he entered the cockpit."

There is no doubt the captain has heard the stall warning, but more than anything there is no doubt the captain has heard the stall warning STOPPING which played enormously in his inadequate evaluation of the situation.
Direct law would have prevented that warning to erroneously quit.

Last point but not the least, the sidestick concept did hide to the PNF initially, and then to the captain + PNF what the PF inputs were and how those were inappropriate at times.


All those points had to be thouroughly developed by the BEA, and not only superficially for some and completely ignored for others.
As written earlier, that law that trim that stall warning logic and that sidestick concept worked against that crew that night.
CONF iture is offline  
Old 25th Aug 2012, 14:57
  #110 (permalink)  
 
Join Date: Jan 2005
Location: W of 30W
Posts: 1,939
Originally Posted by TTex600
Maybe your sim instructor know tricks mine does not, but an Airbus MIA A320 Simulator with only one ELAC/SEC/FAC on handles like a truck with malfunctioning power steering and broken dampers.
The only way my instructor could force Dir Law left us with no roll control spoilers, slow ailerons, and resulted in an extremely unresponsive airplane.
I canít tell for the 320, but for the 330, according to the flight control architecture, PRIM 1 or 2 maintain one pair of ailerons + 1 pair of spoilers for roll control + both elevators.
I have no memory of sluggish control, but would have probably to experiment it again.
Direct Law, in the manner some desire, would offer full control of all control surfaces, as its name implies, directly.
That would be a great thing, one simple guarded switch to force direct law. But I donít see that in the Airbus philosophy where the airplane is supposed to take care of the pilot, not the pilot to dare doubting the technology Ö
CONF iture is offline  
Old 25th Aug 2012, 15:19
  #111 (permalink)  
 
Join Date: May 2011
Location: BOQ
Age: 75
Posts: 484
Max roll rates of 25 degrees/s in Direct versus 15 degrees/s in Normal would seem to indicate the 330, at least, is more responsive in Direct.

THS 13 versus 3:

During specified sim stall QTG's (Direct, fixed THS), with SS full aft, AOA's run about 15-20 degrees less than the FDR values from the report.

As might be expected very similar to, for example, 727 or 737 AOA values. FPV if selected never leaves the PFD display FOV at these values.
OK465 is offline  
Old 25th Aug 2012, 15:28
  #112 (permalink)  
 
Join Date: Aug 2011
Location: Grassy Valley
Posts: 2,123
PJ2....thank you sir, for your kind and weighty response. I am giving it the time it deserves, and the state of my brain allows. Your patient responses are waypoints on a voluminous journey.

TTex600.. INRE: Poor technique, "Mayonnaise", and "bump and suss". I think it may be more prevalent than we think? It looks suspiciously like an evolved and ad hoc response to Airbus flight controls....

It resembles "Pilot induced turbulence". Over controlling to goad the aircraft into giving up some feel, as it were. Or to make "minor" corrections in flight path?
As per FCTM? Unusual it has received little attention here. In other aircraft it would not make it past first flight in type?

You have seen it? Could you enlarge on your experience with it? It seems horrendously out of touch with such a sophisticated airplane and her philosophy?

Similarly, it presents as reactive and defensive....no one would fly a Boeing in similar fashion.
Lyman is offline  
Old 25th Aug 2012, 16:20
  #113 (permalink)  
 
Join Date: Jul 2009
Location: DFW
Age: 57
Posts: 246
Originally Posted by DL-EDI
Fair enough, but my main point of contention is: why "Damn Airbus" rather than "Damn modern flight decks"? Why "Damn Airbus" rather than "Damn modern training that apparently doesn't make appropriate use of pitch and power second nature to every crew in the absence of airspeed data"?
Agreed, with the addition that the AirBus integrated FlightDirector/AutoThrust system REQUIRES one to follow the FD's otherwise the AutoThrust becomes confused. This characteristic, that is Airbus specific I believe, forces the pilot to concentrate largely on the FD. That FD "focus" requires that Airbus training is largely void of pitch/power reliance. In that sense, the airplane is at least part of the problem.

My fix is simple, if you turn one automated system off, get ready to turn ALL of them off. A/P OFF, A/T OFF, FD's OFF. Works quite well.
TTex600 is offline  
Old 25th Aug 2012, 16:23
  #114 (permalink)  
 
Join Date: Jul 2009
Location: France - mostly
Age: 80
Posts: 1,689
Confiture,

Just to defeat the notion of 'evasion':

As elevator deflection is proportional to stick deflection, any erratic movements of that stick tend naturally to disappear especially when speed is still high or a price has to be paid on the human body.
Considering the inertia of the airplane, I'm not so sure of that. Perhaps you should try it in your next simulator opportunity.

THS at 13 deg instead of 3 deg is an elephant in the room.
Direct law would not have allowed its presence.
I suppose you mean that there is no autotrim and that you assume that the PF would not have trimmed manually. At 02:11:35 he seemed pretty desperate to keep the nose up, and in direct law "USE MAN PITCH TRIM" is displayed on the PFD.

Any release of the stick, not to talk about push command, would have provoked an immediate ND change in the attitude.
Direct law would not have allowed to go that easily to the stall and would have favorized an exit from that stall.
In the two instances that the PF released the stick, the elevator responded and the airplane promptly pitched ND.


There is no doubt the captain has heard the stall warning, but more than anything there is no doubt the captain has heard the stall warning STOPPING which played enormously in his inadequate evaluation of the situation.
Direct law would have prevented that warning to erroneously quit.
While it is probable that the stall warning would have been uninterrupted in direct law, that is not certain.

Last point but not the least, the sidestick concept did hide to the PNF initially, and then to the captain + PNF what the PF inputs were and how those were inappropriate at times.
I have earlier expressed my opinion on the visibility of the sidestick. Seeing the control pulled to the back stop might have added another clue that might have pointed the PNF and particularly the captain towards a correct diagnosis of the situation.

All those points had to be thouroughly developed by the BEA, and not only superficially for some and completely ignored for others.
Perhaps you would care to justify that opinion considering that BEA's investigations "are conducted with the sole objective of improving aviation safety and are not intended to apportion blame or liability."

Last edited by HazelNuts39; 25th Aug 2012 at 20:30. Reason: reference to "use man pitch trim" on PFD
HazelNuts39 is offline  
Old 25th Aug 2012, 16:25
  #115 (permalink)  
 
Join Date: Jul 2009
Location: DFW
Age: 57
Posts: 246
Originally Posted by OK465
Max roll rates of 25 degrees/s in Direct versus 15 degrees/s in Normal would seem to indicate the 330, at least, is more responsive in Direct.
That would depend on how the airplane arrived at Direct Law. If it goes direct because of compounded flight control computer failure, you are left with reduced control surfaces and the aircraft response will be reduced. If it goes direct because of something other than computer failure, it might retain full control surface complement and be quite responsive.
TTex600 is offline  
Old 25th Aug 2012, 16:37
  #116 (permalink)  
 
Join Date: Jul 2009
Location: DFW
Age: 57
Posts: 246
Originally Posted by Lyman
TTex600.. INRE: Poor technique, "Mayonnaise", and "bump and suss". I think it may be more prevalent than we think? It looks suspiciously like an evolved and ad hoc response to Airbus flight controls....

It resembles "Pilot induced turbulence". Over controlling to goad the aircraft into giving up some feel, as it were. Or to make "minor" corrections in flight path?
As per FCTM? Unusual it has received little attention here. In other aircraft it would not make it past first flight in type?

You have seen it? Could you enlarge on your experience with it? It seems horrendously out of touch with such a sophisticated airplane and her philosophy?
I've slept at least once since writing about poor technique, and I'm in a bit of a hurry at present. With that said, "Mayonnaise" differs from the "slap the stick" method to which I refer. Mayo would be akin to full scale deflections and opposite full scale deflections in the opposite direction (made in my opinion due to the lack of a link from stick to controls. Sometimes one wants more roll and ends up at full SS deflection which then requires full opposite stick and back and forth) where slapping the stick is minor corrections made somewhat like a 16 point roll performed by a world class aerobatic pilot.

I brought that up as an example of something the FCTM should discourage vs encouraging.

But for now, I've got to get back to planting my fall garden.

Last edited by TTex600; 25th Aug 2012 at 16:38.
TTex600 is offline  
Old 25th Aug 2012, 17:16
  #117 (permalink)  
 
Join Date: Jun 2011
Location: Devonshire
Age: 92
Posts: 300
A very much earlier comment, from a couple of thousand years ago, was:
" Do not let your left hand know what your right hand is doing."
Whilst this was related to giving, charity, in aviation terms it could mean information from one pilot to another.
PF was, presumably, using his right hand. PNF was able to comment on stirring the Mayonnaise, scarcely on the use / abuse of NU.
They had a couple of minutes to "Permutate the Possibilities", as a Royal Flying Corps pilot would have put it.

Last edited by Jetdriver; 25th Aug 2012 at 18:40.
Linktrained is offline  
Old 25th Aug 2012, 17:38
  #118 (permalink)  
 
Join Date: Dec 2010
Location: Middle America
Age: 79
Posts: 1,146
Lyman,

Here are a couple of clips of hand flying a Boeing 737 near landing at lower speeds. In the second clip, the PF is in the left hand seat but you can see the yoke movement over the shoulder of the PNF in the right hand seat . There are no clips of hand flying at altitude or high speeds as the AP does that. I would imagine at higher speeds and thinner air, manual flying (hand movements) of either the stick or yoke would need to be highly finessed (light touch) just as maneuvering at high speed in your car would require so as not to experience LOC. I threw in one Airbus clip just for example to go with the Boeings. Note in the Airbus, you can observe the trim wheels turning as you do in the Boeings.
Cheers!
Turbine D is offline  
Old 25th Aug 2012, 18:33
  #119 (permalink)  
 
Join Date: May 2011
Location: BOQ
Age: 75
Posts: 484
That would depend on how the airplane arrived at Direct Law.
TTex: Point taken, I'll do a little research...

(There certainly is a lot of RED on the right ND in that NG video. )
OK465 is offline  
Old 26th Aug 2012, 01:22
  #120 (permalink)  
 
Join Date: Aug 2009
Location: Germany
Age: 63
Posts: 1,809
Sorry if already posted (consider as a reminder .. )
Aero 12 - Angle of Attack
jcjeant is offline  

Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.