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AF 447 report out

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AF 447 report out

Old 10th Jul 2012, 11:09
  #281 (permalink)  
 
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[Not a pilot] We learned over the Hudson that "my airplane," "your airplane" works well to establish change of control. Is there a similar convention for unexpected events? That is, if over Buffalo the pilot had said "tailplane stall," the copilot might have been able to say, "let's try increasing the speed first." At least the investigators would know what the pilot was thinking after the worst had happened. The same for the possibly suicidal pilot who seemed to be pushing while the co-pilot was pulling. Saying "nose dive" would only help the investigators, but if the pilot were not suicidal, he would have had the chance to offer his view of the situation.

In AF447, if someone had said, "classic stall," (and perhaps this was stated at one point) would there have been a better chance that the pilot in command would have thought to lower the nose?

This kind of summary would not seem to help in cases where the co-pilot was supposed to be calling out, e. g., air speed, but was not, but some kind of impromptu summary would seem helpful in rapidly developing events that do not have an established procedure or where the proper procedure is not immediately apparent.
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Old 10th Jul 2012, 13:24
  #282 (permalink)  
 
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Deep Stall

From an aerodynamics perspectiive a deep stall is not confined to T-tail aeroplanes. It applies where an aircraft is not recovered in good time from the initial symptoms (heavy buffet, nose drop (longitudinally stable machines), sink, possible wing drop). A deep stall can be quite stable as DP Davies explains and requires extremely persistent and large AoA reduction.

Yes of course the T tail has the disadvantage of loss of elevator authority due to the change in wake from the stalled wing but that is more a case of a "locked in" condition. And most pilots think deep stalls only apply to Javelins, DC9s etc...
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Old 10th Jul 2012, 14:34
  #283 (permalink)  
 
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The idea of a 'straight and level' 'fallback' autopilot function is a good one, except that as you will both doubtless know, once you start coding for this you will find there will probably be situations where that is not the best solution.
The code is basically a series of conditional statements: "if x is true then do y" so any situation that can be foreseen can be written into the code. In situations where that 'straight and level fallback' is not the best solution, other options could be in place, including reverting to the current logic (handing control to the pilot).

A lay pseudocode example of an obvious stall avoidance scenario:
"If altitude>35,000, if airspeed unreliable, if thrust idle, if TCAS not blaring, and if AOA >10% set pointNoseDownFast=true! otherwise do nothing"

Add some better thought-out version of the above logic to the flight computer and without affecting anything else you could avoid this accident.

My issue is more with the piecemeal approach to this automation, where pilots are not just pilots, they're computer operators interfacing with the software that actually does the flying. Either pilots should be rigorously trained in the software (including how it was written), and that software should be responsible for handling all possible scenarios (loss of airspeed being quite a common one) while providing intuitive feedback to the "computer operator", or it should be removed apart from the simplest functionality (more along Boeing lines).

Last edited by PanPanYourself; 10th Jul 2012 at 14:44.
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Old 10th Jul 2012, 14:52
  #284 (permalink)  
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Several points there, PPY. Firstly memory is not unlimited in the system. I am 'OK' with coding, but your 'lay' line is all 'ANDS'. Now write in options for unreliable altitude, AoA, thrust and attitude and any combination of these, and you will 'hand control back to the startled pilot', no doubt, at some point - now even more 'startled' because he expects HAL to cope with most things.

Your last phrase is the only viable one, since it is the only one that will cope with actual computer failure/malfunction.

Way back we discussed the 'big red button' option, which I am in favour of, where when pressed it does exactly the S&L function, based on last know valid parameters, but only when a conscious call is made, and not when 'IT' decides.

We need some more discussion, here, guys and girls. Is this a way forward?
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Old 10th Jul 2012, 15:16
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does the airbus have a PITCH HOLD mode(selectable by human pilot) for the autopilot?
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Old 10th Jul 2012, 15:30
  #286 (permalink)  

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AF 447 report out

Clandestino
Wrote on his Post 263
Quote:
Originally Posted by robertbarsch
1. Don't fly into a storm

"They never did".
If, in one of those many endless dark nights when the silence was broken only by the whistle of the engines and the air on the fuselage, and, gossips of flight engineer, I spent over the Atlantic since more than forty years ago, I had seen on my radar a chain of cumulus nimbus clouds (and I've never failed to detect one) like those in the images that ironbutt57 has kindly procured, I would not hesitate to deviate to the left 300 nm since INTOL.
If this had been done, now we would not be talking about this tragic accident.

Last edited by DOVES; 10th Jul 2012 at 16:48.
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Old 10th Jul 2012, 15:37
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In normal law the aircraft maintains attitude selected by last stick I put, within certain boundaries...sort of like permanent CWS for you Boeing folks
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Old 10th Jul 2012, 15:52
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The key counter measure (from my very limited understanding) was removing the AOA protection and handing the elevator control over to the PF
Why was the AOA protection shut off? The computer continued to receive valid AOA info (which is not available to the pilot btw).

Last edited by vovachan; 10th Jul 2012 at 20:31.
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Old 10th Jul 2012, 17:21
  #289 (permalink)  
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Originally Posted by Doves
I had seen on my radar a chain of cumulus nimbus clouds (and I've never failed to detect one) like those in the images that ironbutt57 has kindly procured, I would not hesitate to deviate to the left 300 nm since INTOL.
If this had been done, now we would not be talking about this tragic accident.
- don't forget that those images were not what you would have seen on your shufti-scope - the colours are synthetically produced based on temperature I believe and we just do not know what would have been seen on their radars.

We are definitely seeing the Oozlum bird circling around now - we've had an outbreak of 'deep stall' again, a few 'they flew into a thunderstorms' (as above) and we are now well overdue for another outbreak of 'coffin corneritis'.
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Old 10th Jul 2012, 17:49
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AF 447 report out

BOAC
Can I humbly reveal a secret?
Once upon those time my radar scope had only one color (with various shades): GREEN
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Old 10th Jul 2012, 18:11
  #291 (permalink)  
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Yes, my secret - I've used green ones too. This did confuse me though

"and I've never failed to detect one) like those in the images that ironbutt57 has kindly procured,"

I assume you didn't really mean that? Was that another 'secret'?

For those who do not seem to grasp it

THERE IS NO EVIDENCE THEY FLEW INTO A CB

Last edited by BOAC; 10th Jul 2012 at 18:11.
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Old 10th Jul 2012, 18:46
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THERE IS NO EVIDENCE THEY FLEW INTO A CB
As I said on the last page: They flew right into the middle of one of the most intense storms seen in that region in the past 6 years. Numerous different platforms - not just those using temperature - detected heavy rain (near the upper limit of their capability), extreme convective activity (again, near the limits of their capabilities) and very cold clouds that exhibited large differences with height (indicative of an intense storm).

Based on those the Wx conditions the radar on AF447 should have had no problems picking up the storm. Radar systems similar to aircraft Wx radar (but space-based) detected the conditions with ease and as far as I remember from the report other aircraft changed course to avoid the same cloud formations - so they must've seen the problem.
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Old 10th Jul 2012, 19:17
  #293 (permalink)  

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AF 447 report out

BOAC
My other two secrets:
-I've never seen near the equator a cb with a top lower than 38,000 to 42,000feet (and I swear that I would never even overfly them with any separation).
-And by the way among ‘..those … images that ironbutt57 has kindly procured’ there is Figure 10. Cross-section of Air France 447 flight track through thunderstorm cluster, which depicts extension and altitude of clouds in scrutiny.
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Old 10th Jul 2012, 19:33
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Having read through the cvr I was struck by the apparent lack of clarity in the pre-incident chatter and also by the apparent frequent ellipses during the incident. Surprising to have so much non-relevant chatter given the circumstances ..........

Last edited by Mr Optimistic; 10th Jul 2012 at 19:34.
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Old 10th Jul 2012, 19:54
  #295 (permalink)  
 
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Nemrytter, a rather thorough analysis of the g-data from the FDR shows that no significant turbulence was encountered that would have hampered handling. They DID in fact encounter the icing problem, and if we do a very tight root cause analysis, we discover that without iced-up pitot tubes NONE of the rest follows.

The point a lot of people have made, pilots and others, is that UAS from frozen up pitots is a known malfunction for which there are some effective procedures. Likewise, if the FD goes wrong, or if UAS is the general problem, you turn the FD's off and take some other concrete actions, work through the procedures step-by-step, and get yourself back into the flying condition you desire.

Also of note, the data show that the UAS itself was intermittent, which to me means that the pitot's being rendered INOP sort of cleared itself up, but apparently not all at once. Trouble is, that wasn't necessarily obvious to the pilots, but a UAS procedure was available to deal with the fact that the airspeed input was acting up.

I appreciate your point on Wx avoidance, and also Robert's resetting the radar to a more suitable mode, which I concur let to the (late?) heading correction made (12 deg IIRC) to at least partly avoid what he diagnosed as Wx he'd rather not hit.

That leaves the crew with a malfunction which, had it been handled one way, we'd never have known about unless it was added to the other 36 UAS events that have been discussed at some length on the Tech Log forums.

The response instead included a possible misdiagnosis, and what appears to have been a low-alt tailored response to a high alt UAS event ... and it all ended in tears. (Points on training, recency, and currency apply here in the human factors facets of this event).

It isn't as simple as Wx penetration being the cause.
There was still plenty of room NOT to end in tears, even with entering a bit of rougher weather than they intended to.

To make a rough analogy of a different way to die while hauling pax from place to place ...

I can make a turn in the wrong direction in bad weather near an airport. (perhaps on the way into Islamabad in rainy weather somewhat recently???)
If I notice my mistake (or hear from ATC that I am off course?) and make the proper correction to that error, I don't hit the mountain. If I instead keep my error in, and then do something that isn't correcting my heading error, I hit the mountain and it ends in tears.

The Wx didn't cause that, but poor Wx contributed to it -- right?

Last edited by Lonewolf_50; 10th Jul 2012 at 20:04.
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Old 10th Jul 2012, 20:12
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Nemrytter, a rather thorough analysis of the g-data from the FDR shows that no significant turbulence was encountered that would have hampered handling. They DID in fact encounter the icing problem, and if we do a very tight root cause analysis, we discover that without iced-up pitot tubes NONE of the rest follows.
...
It isn't as simple as Wx penetration being the cause.
I never said that it was, I was correcting the guy who said that they never encountered intense weather. As I figure you know bad weather doesn't necessarily mean turbulence (+vice-versa) but it can cause other problems - like the icing you mention. Convection can raise warm air to altitude and that can cause the icing problems. Whilst the cloud tops were very cold it looks (based on the data I have) that the temperature at lower altitudes (i.e: ~FL350-400) were quite a bit warmer than normal. This matches the BEA report. What's clear is that it was a rather rare set of circumstances.

To be clear: The Wx was an important factor in the crash, acting as a trigger perhaps, but far from a singular cause. The only reason I posted was to correct the other chap and I definitely didn't mean for it to dominate the discussion.

(edit)
The Wx didn't cause that, but poor Wx contributed to it -- right?
Yes, agreed!

Last edited by Nemrytter; 10th Jul 2012 at 20:13.
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Old 10th Jul 2012, 20:26
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nemrytter:
We have an accord.

Apologies if I took your remarks out of context. Oops.
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Old 10th Jul 2012, 20:27
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Stall warning logic

I don't understand the stall warning logic of the A330. If you have an indicated airspeed of less than 60kts, and there is no weight on wheels (i.e. the airplane knows it's airborne), aren't you stalled?

Why the arbitrary cutoff of the aural stall warning at 60kts? I understand the AOA won't be reliable at that speed, but who cares, if you're airborne at less than 60kts IAS in an A330, you're stalled.

Last edited by Flight Safety; 10th Jul 2012 at 20:28.
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Old 10th Jul 2012, 20:54
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Originally Posted by Lonewolf_50
This opens the question: was the PF using FD as a reference, or a primary reference for his instrument scan, even though it was not being reliably sourced by the data it is usually fed?
I found an article which expands on this theory that the PF was following the Flight Director and that this might explain his pitch-up inputs.

Final AF447 Report Suggests Pilot Slavishly Followed Flight Director Pitch-Up Commands | Aviation International News

After the autopilot and autothrottle disengaged, as the flight control law switched from normal to alternate, the flight director’s crossbars disappeared. But they then reappeared several times. Every time they were visible, they prompted pitch-up inputs by the PF, investigators determined.
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Old 10th Jul 2012, 21:03
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I don't know for certain [] but I think it may come down to the certification requirements of primary flight instruments viz reliability modus of wow sensors...
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