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

AF447 wreckage found

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

AF447 wreckage found

Old 17th Jul 2011, 20:54
  #2061 (permalink)  
 
Join Date: Mar 2009
Location: Inside
Posts: 285
Likes: 0
Received 0 Likes on 0 Posts
RWA,

I do realize that as a professional pilot I have become outnumbered here by instant experts who can tell us 'how it is' by watching youtube videos and quoting wikipedia and what not. I note that you also think you should 'give me the idea' of what I do for a living. Should I say thank you or just laugh?

What slipped past your eagle eye is that the A320 in your video is level in cruise with AP and ATS engaged and under control. It is a video of set piece like a free kick at the edge of the penalty box. It tells you nothing about how to get the ball there in the first place or even how to play at all.

I think I will stick with nonsense, thank you very much.
One Outsider is offline  
Old 19th Jul 2011, 01:53
  #2062 (permalink)  
 
Join Date: Jun 2009
Location: Belfast
Age: 46
Posts: 21
Likes: 0
Received 0 Likes on 0 Posts
Hi One Outsider,

As a non-professional pilot, and therefore one of the multitude who now out-number you, there is still one burning question in my mind. I'm not being cheeky towards your post, it's just the most recent one I can reply.

Why the zoom?

I have flown before, in fact I trained in the Aussie Air Force. Ultimately I was unsuccessful on that course because I incorrectly applied good 'airmanship' on several occassions. Those fo-pars that ultimately failed my endeavours were far less serious than failing to apply known procedures to a system failure.

I've said it before, and I'll keep saying it, unless there was some monumental failure of things we haven't heard about yet, the pilots appear ill-trained / equipped to deal with what should be a simple emergency.
Poit is offline  
Old 19th Jul 2011, 05:05
  #2063 (permalink)  
 
Join Date: May 2000
Location: Phuket
Posts: 297
Likes: 0
Received 0 Likes on 0 Posts
So, general anti FBW ranting aside, at which point do you suppose the FCS overrode the pilot's input, causing or contributing to the accident?
Is it actually is possible (is it? I really do not know) for the system to have the last word? Be honest please, think, is it possible for the system with A particular set of circumstances to override the pilots? I know it is like asking what if a wing falls off so please humor me with this seemingly naive question. I am just a old DC8/9 guy and the only glass I have flown is on a helicopter.
before landing check list is offline  
Old 19th Jul 2011, 05:55
  #2064 (permalink)  
 
Join Date: May 2011
Location: venice, ca
Posts: 61
Likes: 0
Received 0 Likes on 0 Posts
Thunderstorms - speculation

Lomapaseo

All the other aircraft in the area deviated. Why not this one?

Two posts in a row state as facts about the aircraft flight into a defined thunderstorm without deviation.

I challenge those facts

Where's the investigative data that so states?

To continually speculate for a simple explanation does nothing to furthur the understanding of a complex accident.

lomapaseo

Check out " Air France Flt 447: A meteorological analysis "

Not speculation!!
wallybird7 is offline  
Old 19th Jul 2011, 06:23
  #2065 (permalink)  
 
Join Date: May 2011
Location: venice, ca
Posts: 61
Likes: 0
Received 0 Likes on 0 Posts
BEFORE LANDING CHECK LIST

I'm not fully aware of the A330 specifics -- but it's not so much having the last word, as it is -- doing something the pilots were not aware of.

And my take is with the A/P and A/T clicked off, and in turbulence, without airspeed guidance, and the pilots not allowed to hand-fly an airplane at altitude, and a overly sensitive control system -- it seems to me to be very easy to over control and not be aware of it and also unaware of the side stick inputs they are putting in.

Otherwise why a unusually high pitch attitude? The trim just did what it was told to do.
wallybird7 is offline  
Old 19th Jul 2011, 08:06
  #2066 (permalink)  
 
Join Date: May 2000
Location: Phuket
Posts: 297
Likes: 0
Received 0 Likes on 0 Posts
The trim just did what it was told to do.
So... the big question I was leading up to; WHO (Man or machine) told it to do what and why?
before landing check list is offline  
Old 19th Jul 2011, 08:27
  #2067 (permalink)  
 
Join Date: May 2011
Location: here
Posts: 131
Likes: 0
Received 0 Likes on 0 Posts
before landing checklist,
I think the point is - wouldn't you have been just as dead when applying the same inputs to a DC-8?
If anything, the bus gave them a bigger shovel (autotrim), but it was their decision to start digging. How they'd arrived at that decision seems to be the interesting part.
Zorin_75 is offline  
Old 19th Jul 2011, 10:34
  #2068 (permalink)  
 
Join Date: Mar 2001
Location: us
Posts: 694
Likes: 0
Received 0 Likes on 0 Posts
wallybird7, you are suggesting that they deliberately flew into a defined thunderstorm? Defined by who? and when?

From a few pages back in this thread, mm43's corrected image:


IMO, neither the Lufthansa nor the Iberia flights deviated enough to take them out of the bright green. (I concede I am using a static image to describe a dynamic situation, but the BEA has chosen not to release the precise path of the deviations by those two flights so one can't map against different satellite imagery.) AF459 deviated enough to the right to possibly avoid the bright green.
_______________

Do you have knowledge of the crew of AF447 adjusting the tilt and gain of their radar as AF 459 did, and still proceeding on the track?
SaturnV is offline  
Old 19th Jul 2011, 13:30
  #2069 (permalink)  
 
Join Date: Aug 2009
Location: Texas
Age: 65
Posts: 7,358
Received 544 Likes on 343 Posts
wally:
wallybird: Two posts in a row state as facts about the aircraft flight into a defined thunderstorm without deviation.
A course deviation of 12 degrees was recorded before this upset event. It's in the BEA report. Was the deviation big enough? Different question.

I'll echo Saturn V's other point: defined thunderstorm conclusion is based upon what criterion? That they knew they were flying into unstable air seems to be confirmed by the brief CVS discussions released to date, and the apparent decision to reduce speed to turbulent air penetration speed before they hit what they expected to be a patch of the rough stuff.
Lonewolf_50 is offline  
Old 19th Jul 2011, 23:07
  #2070 (permalink)  
 
Join Date: Jun 2009
Location: California
Age: 55
Posts: 203
Likes: 0
Received 0 Likes on 0 Posts
Pre-flight briefing of AF447 will shed light on whether the storm cluster was expected and to what extent.
Keep in mind that the image above does not use the same color coding as the one we see in on radar. So the AF447 radar could have seen anything from nothing to a wall of red. From what I have read here the use of the gain adjust is critical when traversing the ITCZ.
xcitation is offline  
Old 20th Jul 2011, 00:49
  #2071 (permalink)  
 
Join Date: Aug 2005
Location: fl
Posts: 2,525
Likes: 0
Received 0 Likes on 0 Posts
In all my years I have never done a preflight briefing of weather enroute. We look at what is shown and take off knowing what to expect. They must have encountered some icing and their pitot tubes froze up. That alone apparently took the airplane down for some reason. There is no evidence of their deviation 12 miles left of course not being adequate.

Using the fact they crashed is silly. If they iced up 40 miles off course probably wouldn't have made any difference. Hopefully the final report will clarify everything but right now we have zilch info.
bubbers44 is offline  
Old 20th Jul 2011, 01:57
  #2072 (permalink)  
bearfoil
Guest
 
Posts: n/a
Assume UAS. Without Airdata, the a/c cannot be autoflown. A new Flight Law is entered, and the PF is the only way to get home (if but temporarily).

Fine. This aircraft has a reputation for being docile, easy fly, and hand flying no problemo. So why no auto flight? Again, no reliable Airdata.

So on the one hand, UAS is not a 'big' deal, but big enough that the a/c cannot do it. Just fly Pitch and Power, one hears.

Fine. Isn't Pitch and Power the easiest (basic) way to fly? So why no auto P/P?

At altitude, in those conditions, PJ2's post describes the hazards of flight re: control damping and authority.

Fine. With turbulence, the a/p has the same airmass to deal with as the Pilots, subject to overcontrol, sensitivity, g and PITCH. So the a/p can do these, but not something so simple as PnP? PnP is what it has been doing since ORARO, with flourishes, and a nice ride?

It is the fundamental duty of autoflight to keep the a/c stable and consistent. What about the challenge of UAS has nothing to do with what an a/p needs to do every day, all day long?

Yet the PF has no access to the accelerometers (except by display), and has to deal with natural conditions that don't affect the a/p one bit?
IE Dark, no constant updata, distraction, and ECAMs?

For once and all, can someone address why it is impossible to consider that the autoflight couldn't (keep up) even with reliable a/s, and UAS may have been the result of insufficient response in the auto regime? (turbulent air mass, discrepant instant baddata?)

someone, splain.
 
Old 20th Jul 2011, 09:52
  #2073 (permalink)  
 
Join Date: Apr 2010
Location: Poland
Age: 49
Posts: 15
Likes: 0
Received 0 Likes on 0 Posts
UAS vs autopilot

Assume UAS. Without Airdata, the a/c cannot be autoflown. A new Flight Law is entered, and the PF is the only way to get home (if but temporarily).

Fine. This aircraft has a reputation for being docile, easy fly, and hand flying no problemo. So why no auto flight? Again, no reliable Airdata.

So on the one hand, UAS is not a 'big' deal, but big enough that the a/c cannot do it. Just fly Pitch and Power, one hears.

Fine. Isn't Pitch and Power the easiest (basic) way to fly? So why no auto P/P?

At altitude, in those conditions, PJ2's post describes the hazards of flight re: control damping and authority.

Fine. With turbulence, the a/p has the same airmass to deal with as the Pilots, subject to overcontrol, sensitivity, g and PITCH. So the a/p can do these, but not something so simple as PnP? PnP is what it has been doing since ORARO, with flourishes, and a nice ride?

It is the fundamental duty of autoflight to keep the a/c stable and consistent. What about the challenge of UAS has nothing to do with what an a/p needs to do every day, all day long?
Because, in foreseeble future AP must be kept simple. AP and similar software (it's now software thing) is, compared to many other software systems, quite simple. And if it's going to be certified to fly 400+ pax in crowded skies over densely populated areas it must be kept simple. The key feature of such life critical systems (like AP, FBW controls, dangerous industrial processing controls, like chemical or atomic) is traceability. I.E. each action of the hardware must be clearly traceable to particular instructions in software source code. Then the thing must be proven (often formally, mathematically) that it faightfully represents it's specification.

You want P'n'P of that software, but now how to solve such things like P'n'P while climbing, while descending, while keeping altitude (esp. in reduced vertical separation space), etc. Then if there is UAS AP must be sure it is isolated and is not a sign of some other bigger problem. The human interface would also get more complicated and hard to grasp.


And there is one thing to all that -- the software is deterministic (and in transport planes it will for some significant time into the future). It's meant to always behave the same given the same situation. It has no second thoughts. It has no thoughts at all to begin with. It is preprogrammed for particular behaviours in particular situtations. If situation is not fully understood beforehand the best action is to disconnect the thing. Otherwise it could turn into garbage in - garbage out and you don't want garbage out while moving at Mach 0.8 at FL350.
But there are those two guys (or gals) in front. They're not there to just monitor all that machinery -- with current technology they could better monitor it from some warm place on the ground (as it happens with spacecraft, for example). They're there to handle all the situations which could develop.

Yet the PF has no access to the accelerometers (except by display), and has to deal with natural conditions that don't affect the a/p one bit?
IE Dark, no constant updata, distraction, and ECAMs?
Yes, because those guys and gals are not preprogrammed. AP has no thoughts no understanding. None, nada, nil. All additional conditions like ECAMs etc would add exponentially to complexity of preprogrammed AP.


For once and all, can someone address why it is impossible to consider that the autoflight couldn't (keep up) even with reliable a/s, and UAS may have been the result of insufficient response in the auto regime? (turbulent air mass, discrepant instant baddata?)
UAS could not have been the result of insufficient response. Air which would be 60kts on one side and 180 on the other would simple tear airplane apart. UAS was due to pitot fail not due to turbulence causing reliable but discrepant measurements.
sebaska is offline  
Old 20th Jul 2011, 13:09
  #2074 (permalink)  
 
Join Date: Nov 2008
Location: Crew lounge
Posts: 87
Likes: 0
Received 0 Likes on 0 Posts
Originally posted by Bubbers44 :
In all my years I have never done a preflight briefing of weather enroute. We look at what is shown and take off knowing what to expect. They must have encountered some icing and their pitot tubes froze up. That alone apparently took the airplane down for some reason. There is no evidence of their deviation 12 miles left of course not being adequate.

Using the fact they crashed is silly. If they iced up 40 miles off course probably wouldn't have made any difference. Hopefully the final report will clarify everything but right now we have zilch info.
Congratulations "Bubbers", at last one sensible post on this subject :
1) I can't, either, remember of one pre-flight route modification due to en-route weather ;
2) as far as we know, the cause of the crash is not "flying straight into an active cb" but pitot icing.
Icing conditions can be found anywhere : in, near or far away from convective cells.
GerardC is offline  
Old 20th Jul 2011, 14:50
  #2075 (permalink)  
bearfoil
Guest
 
Posts: n/a
Thanks. I see your point(s). You have focused on the crux. Obviously, autoflight is well-equipped to fly the a/c. It does so virtually all the time.

How well equipped is the Pilot(s)? The irony is that the auto is sensitive, sophisticated, and connected directly to sensors that are processed instantly, allowing for smooth flight. Hand flying cannot produce the ride in most circumstances that auto can.

Two circumstances:

1. The autoPilot cannot keep up, drops out, and Normal Law remains.

2. Due UAS, the autoPilot drops out, and a/c reverts to Alternate Law.

Both conditions require hand flight immediately ("I have the controls").

It would seem to me that under condition (1), the a/c would revert to Alternate Law, the a/c is having control issues.

It would also seem to me that under condition (2), nothing has changed except an instrument is U/A. An important one, but one that hasn't to do with control, at least initially.

So Condition '1' wants (needs) immediate hands, and condition '2' is recommended "patience", monitor, do nothing, don't maneuver.

Protections would be better retained in condition 2, yes? Especially so since the a/s is not reliable, and ham handedness is more likely?

Protections also for condition 1, since the a/p has indicated control challenges for the PF at handoff?
 
Old 20th Jul 2011, 16:59
  #2076 (permalink)  
 
Join Date: Jun 2009
Location: Paris
Posts: 691
Likes: 0
Received 0 Likes on 0 Posts
1. The autoPilot cannot keep up, drops out, and Normal Law remains.
This should be rephrased as: if Normal Law remains, auto pilot CAN keep up, there is no reason it drops out (none, zero, zlich, nada, rien, niente, whalou).
Consequently, only your case 2. seems true.
Beside, very good post from Sebaska (above).
takata is offline  
Old 20th Jul 2011, 17:30
  #2077 (permalink)  
 
Join Date: Feb 2005
Location: UK
Age: 85
Posts: 697
Likes: 0
Received 0 Likes on 0 Posts
As an SEP can I please ask you very experienced pilots a question?
If you are flying an (any) aircraft with no outside vis. and suspect instruments and your body and altimeter gave every indication that you were hurtling downwards at a high ft/sec. would it not be a 'normal' reaction to pull back on the stick irrespective of any flight instrumentation. Could this therefore be a case where old fashioned 'seat of pants' reactions were the wrong ones and less 'flying' training and more 'flight' training might, in this case, have yielded a better outcome.
funfly is offline  
Old 20th Jul 2011, 18:36
  #2078 (permalink)  
bearfoil
Guest
 
Posts: n/a
takata noted.

funfly At 10kfpm down, ND creates even more fpm down. Counterintuitive to want to speed up. It also increases the 'g' when one pulls "out" of the ensuing dive (I think 'g' protections won't let him pull out anyway).. PF has surpassed all his flight training when the a/c STALLS. A guessing game for him, and instruments that, even if accurate, would be hard to suss?
 
Old 20th Jul 2011, 19:05
  #2079 (permalink)  
 
Join Date: Jan 2008
Location: uk
Posts: 857
Likes: 0
Received 0 Likes on 0 Posts

2. Due UAS, the autoPilot drops out, and a/c reverts to Alternate Law.
[..]

Protections would be better retained in condition 2, yes? Especially so since the a/s is not reliable, and ham handedness is more likely?
Protections or automatics ?

Protections, I'd say definitely not. bad things can (and have) happen when protections kick in on bad data (or on good data with design rules that turn out to be not so good). To engage protections based on known bad data would be poor design.

The protections are a line of defense at the edge of the envelope where you (auto or real pilot) shouldn't be going in normal flight anyway. It shouldn't matter if they aren't there if the plane is flown properly. Yes, that might be more of a problem with UAS + IMC + Turb etc., but it will be a lot more of a problem if the plane starts protecting you based on invalid data. Some UAS events have reported more or less simultaneous stall and overspeed warnings...


On the other hand, having a degraded A/P that held pitch and power (correct for altitude - assuming that's not dud data as well) and probably wings-level might actually be useful in some situations.
infrequentflyer789 is offline  
Old 20th Jul 2011, 19:10
  #2080 (permalink)  
 
Join Date: Aug 2009
Location: Texas
Age: 65
Posts: 7,358
Received 544 Likes on 343 Posts
Bear: g limits are +2.5, so you can assume that 2.5g is the limit for a pull out maneuver.

HN39 posted a modest 1.5 g pull out estimate a few pages back, and offered a conservative altitude loss estimate. (I think he's optomistic ...)

2.5 g is a firm pull out, but you won't typically get a gray out. Consider that 60deg AOB in level flight is a 2 G maneuver, and you may see what the "feel" is in the aircraft under such an acceleration.

2.5 g is within the aircraft's structural limits. It is (per the info I have access to) the limit of flight control accel limits (caveat: if you put on that much G while the airspeed is too slow, you may experience an accelerated stall, which can lead to a violent departure ... but there is no evidence that this is what happened.

Your comment that aircraft won't let you do that appears unfounded. (There was a neat thread elsewhere about CFIT and Proximity to Ground Warnings, and 'save it' manuvers. IIRC we also discussed this in the Air Blue at Islamabad crash thread ...)

As I understand the way the flight control system works, the pilots could pull for, or try to demand demand, more than a 2.5 g, and only get 2. 5 g. If you postulate that the pull out is initiated at altitude (somewhere beween 15-20k I guess, to allow time for the aircraft to react and for acceleration to flying speed and a fudge factor) you'd likely have brown trousers, and a flying aircraft with some margin at the bottom of the pull out as you add power and start getting your aircraft back up to a more comfortable airspeed and altitude.

Or not, and the aircraft impacts the ocean in a different condition than it did.
Lonewolf_50 is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.