tommytoyz
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AF 447 - Sims Misleading?

Mon Apr 02, 2012 11:55 pm

http://www.aviationweek.com/aw/gener...dline=Upset%20Recovery%20in%20Sims


I will let this article speak for itself. Is there something addresses here that points to why the crew of AF447 reacted the way they did?
 
jollo
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RE: AF 447 - Sims Misleading?

Tue Apr 03, 2012 1:19 pm

I'll take the bait: the article says that a simulator's fidelity does not extend to the “edge of the envelope” maneuvers (and beyond) and that FFSs are therefore unfit for upset recovery training. AA 587 is brought as an example where sims were used not only for training, but also for "developing" incorrect upset recovery maneuvers.

Now, it's probably true that some sims will recover from "full stall" at any altitude just by holding back the stick and applying full throttle: that just proves that whoever programmed such a sim doesn't understand what a stall is (at the closed-form equations level nobody does, to be honest) and that the "Full" in the name "Full-Flight Simulator" is ultimately undeserved.

That's quite a long way from claiming that AF pilots are sim-trained to react the way AF447's PF did. The article doesn't. Do you?

[Edited 2012-04-03 06:29:59]

[Edited 2012-04-03 06:31:19]
 
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Jetlagged
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RE: AF 447 - Sims Misleading?

Tue Apr 03, 2012 2:50 pm

Quoting jollo (Reply 1):
Now, it's probably true that some sims will recover from "full stall" at any altitude just by holding back the stick and applying full throttle: that just proves that whoever programmed such a sim doesn't understand what a stall is (at the closed-form equations level nobody does, to be honest) and that the "Full" in the name "Full-Flight Simulator" is ultimately undeserved.

It's probably untrue. I don't think you'll find any qualified full flight sims that will recover from a full stall with full throttle and aft stick, assuming you can get one to enter and remain in a full stall in the first place. The people who design them aren't totally ignorant of aerodynamics. However most FFS aren't designed to simulate a full stall, just the entry to a stall. What happens in a sim in full stall is much more empirically derived as there's little valid data to go on. Engineers don't just make it up as the go along though. For example, Boeing provide a stall hysteresis model (which was originally developed by Rediffusion engineers) with their simulator data package. This attempts to model the way flow reattaches and the effect of this on longitudinal aero coefficients.

It's basic that sims should be used with caution near the edge of the data envelope in training, certainly not for developing recovery technique and the Aviation Week article is right to warn against it. Some airlines seem to think their multi-million dollar simulators are always correct when in fact at the edge of the envelope they are extrapolating data, nothing more.
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jollo
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RE: AF 447 - Sims Misleading?

Tue Apr 03, 2012 3:59 pm

Quoting Jetlagged (Reply 2):
What happens in a sim in full stall is much more empirically derived as there's little valid data to go on.
Quoting Jetlagged (Reply 2):
in fact at the edge of the envelope they are extrapolating data, nothing more

Correct. That's what I meant by "understanding" what a stall is in an engineering sense (that is, being able to write equations - hopefully in closed form, or real-time simulation becomes really hard - to predict to a required level of accuracy the outcome of a physical phenomenon).

The article quotes Larry Rockcliff, an Airbus captain and co-chair of the Upset Recovery Industry Team:

Quote:
“For example,” he continued, “in one simulator, recovery from a full stall condition could be achieved by holding the control column back and using power to fly out of it, which is absolutely incorrect.”

Which FFS? Mr. Rockcliff doesn't say. But that's beyond the point: nobody would ever dream of teaching recovery maneuvers for severe upsets just because they work out nicely in the sim. I hope.

[Edited 2012-04-03 09:04:50]

[Edited 2012-04-03 09:14:48]
 
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Jetlagged
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RE: AF 447 - Sims Misleading?

Tue Apr 03, 2012 4:16 pm

Quoting jollo (Reply 3):
The article quotes Larry Rockcliff, an Airbus captain and co-chair of the Upset Recovery Industry Team:

Quote:
“For example,” he continued, “in one simulator, recovery from a full stall condition could be achieved by holding the control column back and using power to fly out of it, which is absolutely incorrect.”

Which FFS? Mr. Rockcliff doesn't say. But that's beyond the point: nobody would ever dream of teaching recovery maneuvers for severe upsets just because they work out nicely in the sim. I hope.

To hold an FFS in anything like a fully stalled condition would of course require full aft stick. The sim isn't however fully stalled because the data doesn't go there, and its stability wants to pitch it forward, out of the stall. In my experience the only way to achieve the kind of AOA necessary for a full stall in an FFS is a very dynamic pull into the stall which of course is a transient condition. You can't maintain such high AOA, the model won't allow it. So given full thrust, more lift and less drag than you should have it's possible such a recovery could be flown. But it's not a recovery from a full stall.

[Edited 2012-04-03 09:19:54]
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David L
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RE: AF 447 - Sims Misleading?

Tue Apr 03, 2012 5:35 pm

Quoting jollo (Reply 1):
That's quite a long way from claiming that AF pilots are sim-trained to react the way AF447's PF did. The article doesn't.

   I thought the earlier discussions had established that airline crews are generally trained to avoid a full stall by recovering from the entry to a stall, i.e. by not getting there in the first place. I also thought there was general agreement that the crew of AF447 didn't seem to recognise, among other things, that they were fully stalled. In any case, the stick wasn't held fully back throughout. Though the inputs were mostly nose-up, the amount varied.
 
Mir
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RE: AF 447 - Sims Misleading?

Tue Apr 03, 2012 7:20 pm

Quoting jollo (Reply 1):
Now, it's probably true that some sims will recover from "full stall" at any altitude just by holding back the stick and applying full throttle

Not really. Try that at high altitude in a FFS and it's not going to work.

-Mir
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jollo
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RE: AF 447 - Sims Misleading?

Tue Apr 03, 2012 8:52 pm

Quoting Mir (Reply 6):
Not really. Try that at high altitude in a FFS and it's not going to work.
Quoting Jetlagged (Reply 4):
The sim isn't however fully stalled because the data doesn't go there...
You can't maintain such high AOA, the model won't allow it.

That's what I meant.

Besides, the OP asked a specific question: sim training could have been a factor in AF477? I believe not.
 
tommytoyz
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RE: AF 447 - Sims Misleading?

Wed Apr 04, 2012 12:26 am

Quoting jollo (Reply 1):
That's quite a long way from claiming that AF pilots are sim-trained to react the way AF447's PF did. The article doesn't. Do you?

I am not knowledgeable enough about how the A330 SIMS are to answer that. Which is why I asked.
 
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Jetlagged
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RE: AF 447 - Sims Misleading?

Wed Apr 04, 2012 2:09 pm

Quoting jollo (Reply 7):
That's what I meant.

OK, as long as you don't still think this is the case.

Quoting jollo (Reply 1):
that just proves that whoever programmed such a sim doesn't understand what a stall is

They understand perfectly well, but they are limited by the data.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
tommytoyz
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RE: AF 447 - Sims Misleading?

Wed Apr 04, 2012 7:52 pm

For those knowledgeable in what goes on with SIM training, I have 2 questions

1.Is stall recovery, especially at altitude, practiced regularly? By this I do not mean stall avoidance, but recovery from a stall after it has occurred.

2. Is use of the manual trim in upset conditions practiced?

In reading about the A320 crash in Perpignan and the AF447 particulars, it seems to me that in both cases the pilots did not pay attention to the elevator trim at all, even though it was going against them. In the A320 crash there was very little time, but shouldn't the pilots have known that in abnormal law, the trim freezes? And that it must be reset manually? The AF447 crew certainly had the time to check the elevator trim position in Alt Law, but there is no mention of them paying any attention to it.

The A320 crash in Perpignan six months prior to AF447, shows that for the A320, the combination of full up trim, full down stick input and full power, results in a nose up response and no stall recovery. If A330s are similar, then AF447 would not have been recoverable even with full down stick, so long as they applied full power and the trim remained were it was. I would not blame any pilot caught by surprise by this, if they did not know the elevator trim characteristics of AB in different laws, besides normal law.

Of course none of this explains the up stick inputs on AF447, but that is another topic altogether.
 
tommytoyz
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RE: AF 447 - Sims Misleading?

Thu Apr 05, 2012 1:45 am

Just came across this:


As we got little extra time in the sim today, we did experience a full stall from FL350.
Here is what I can report from the experience :
From the STALL warning we kept a light aft pressure on the sidestick
It was not long before we got a negative vertical speed of 15000ft/min
THS went to 12 deg UP under STALL warning
As we decided to exit the stall, full fwd pressure on the sidestick was applied
But we were unable to lower the nose
THS did not move
THS was then manually rolled fwd
Nose came down
Exit was then possible
I can't remember all the details, too much stuff to look at.
Thrust was kept at idle all the time.

I am surprised this is not trained regularly.

[Edited 2012-04-04 18:51:27]
 
tommytoyz
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RE: AF 447 - Sims Misleading?

Thu Apr 05, 2012 1:54 am

Another: It seesm to me that manually adjusting trim, especially at high altitudes is critical for recovery

With weights, CG, SAT mirroring AF447 and a bit of turbulence, following loss of airspeed (all 3 ADRs out), the sim was pitched up at FL350 and held in the climb until stalled, (THS reached 13.6deg). Shortly after the stall we returned the ADRs for use during the balance of the exercise, (to see the FPV during the stall).

Post-apogee (approx FL360), full forward stick was applied and held.

At FL330 the pitch was 8deg ND.

At FL310 the AoA (using FPV) was approx 40deg and the VSI was 18000fpm +. Pitch was about 14deg ND which was all the pitch that could be obtained.

Pitch slowly reduced to about 10degND still with full forward stick. As it was held the THS unwound and returned to normal settings.

We could watch the AoA reducing as the FPV slowly climbed "up" the PFD from past the red ND warning arrows below 30deg pitch marks.

Thirty seconds after the first Stall Warning passing through FL270 the AoA had reduced to 30deg, descent rate was 16000fpm.

Ten seconds later at FL255 the AoA was 12deg, CAS was 250kts, VSI was 7400fpm.

At FL245 the stall warning stopped 40 seconds after it began, the AoA was 10degND, M0.658, VSI 7000fpm down, CAS 278kts.

From an AoA of 40deg to 10deg took 24 seconds and about 6000ft. This exercise took about 22000ft; some were less.

Overspeed was never a problem nor was a secondary stall if one was gentle, (took about another 6000ft IIRC)
 
Nicoeddf
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RE: AF 447 - Sims Misleading?

Thu Apr 05, 2012 7:26 am

Quoting tommytoyz (Reply 10):
I would not blame any pilot caught by surprise by this, if they did not know the elevator trim characteristics of AB in different laws, besides normal law.

So you don't blame professional pilots for not knowing their aircrafts capabilities and limits?

Honestly, I do. Everybody has to know the limits and capabilites in their respective jobs, and not only in "normal law" but especially in the rare but crucial "alternate" situations.

Imho, of course...
 
tommytoyz
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RE: AF 447 - Sims Misleading?

Thu Apr 05, 2012 8:37 am

Quoting nicoeddf (Reply 13):
Everybody has to know the limits and capabilites in their respective jobs, and not only in "normal law"

This I agree with 100%. But knowledge and capabilities are also a function of training.

If training is sloppy or insufficient, it is only human nature to be caught by surprised when the untrained situation actually happens.

That is why I think the following should be trained:
- high altitude upset recovery (as opposed to avoidance).
- manual trim.
- manual flying proficiency.

To this last point:

Mentally it seems to me that the pilots panicked or froze. But why? I think it is because of a lack of comfort of hand flying, especially at altitude and in alt law to boot, imho.

There has been a major de-skilling of the airline pilot community by virtue of automation. The new guys coming up are very good in handling the automation and there are apparently an increasing number of them who when asked to hand fly an aircraft break out into a cold sweat. The environment makes it difficult to acquire and maintain essential hand flying skills. The periodic simulator training sessions are too infrequent to really maintain hand flying skills. Many of the formerly accomplished hand flyers have commented on their personal loss of the touch. There is no doubt that automation has permitted a high level of safety despite this apparent loss of skills, but when an aircraft loses critical systems and the automation is crippled, are these new pilots ready to take over and fly?

When I was actively flying, such a loss of control as AF447 experienced for the reason it lost control would be unthinkable. The weakest pilot in my squadron could fly solid instruments by hand (Where we sometimes saw problems was in headwork.)

IMHO AF447 could well represent the "canary in the coal mine" warning us that the hand flying deterioration has begun to cripple not only the third world airlines but also the legacy carriers.

Any airline pilot should be able to fly cruise by hand, cold without a warmup. If he cannot do that simple task, then he really doesn't belong in the cockpit.


[Edited 2012-04-05 01:39:17]
 
jollo
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RE: AF 447 - Sims Misleading?

Thu Apr 05, 2012 10:31 am

Quoting Jetlagged (Reply 9):

They understand perfectly well, but they are limited by the data.

Setting up any computer simulation can roughly be broken down in two tasks:
1) writing the set of equations that govern the phenomenon to be simulated
2) calibrate the parameters that typically appear in such equations, based on data sets collected through an experimental campaign

To my knowledge (admittedly limited), simulation of an aircraft's dynamics in a "fully stalled" condition is difficult not only because test flights seldom stray that far out of the flight envelope (therefore there isn't sufficient data gathered for task 2), but also because the turbulent aerodynamic regime of a stalled wing (and control surfaces) doesn't lend itself well to a closed-form solution, and an accurate set of equations for task 1 isn't - yet - available and widely accepted.

Of course I could be mistaken and would be delighted to be pointed to a source. Of course, you could also argue that current approximations are sufficient for the task even if they aren't "accurate". That would still leave the lack of data to be solved (and *that* one would still be hard to solve: test flights do not cover stalls to 40° AOA for a reason).

Back to the topic: the sim "experiments" decribed by Tommytoyz (very interesting, thanks) seem to indicate that, accurate or not, the actions required to recover a high altitude full stall in a FFS are roughly "right": stick forward, trim down, reduce thrust. I take it as a further confirmation in my belief that it is very unlikely that the reactions of AF447's crew can be explained in any way by sim training.
 
tdscanuck
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RE: AF 447 - Sims Misleading?

Thu Apr 05, 2012 1:34 pm

Quoting tommytoyz (Reply 10):
In reading about the A320 crash in Perpignan and the AF447 particulars, it seems to me that in both cases the pilots did not pay attention to the elevator trim at all, even though it was going against them.

Do you mean elevator trim or do you mean horizontal stabilizer trim?

Quoting tommytoyz (Reply 11):
Here is what I can report from the experience :
From the STALL warning we kept a light aft pressure on the sidestick
...
I can't remember all the details, too much stuff to look at.
Thrust was kept at idle all the time.

I am surprised this is not trained regularly.

I'm not surprised; why would you want a pilot to even flirt with developing muscle memory that it's OK to hold aft pressure after the stall warning? The reaction at altitude must be stall warning leads to nose-down input.

Quoting tommytoyz (Reply 14):
That is why I think the following should be trained:
- high altitude upset recovery (as opposed to avoidance).

I assume you'd advocate for both to be trained, rather than just recovery, yes?

Quoting jollo (Reply 15):
To my knowledge (admittedly limited), simulation of an aircraft's dynamics in a "fully stalled" condition is difficult not only because test flights seldom stray that far out of the flight envelope

Flight test goes fully stalled all the time. There are generally three stall identification points: deterrent buffet, unarrestable nose-down pitching moment, or full aft column for x seconds. The later two can easily get all the way to a full stall.

What flight testing (at least of commercial airliners) does not do is go 54 seconds past the stall while holding full aft and go way (way way way) past full stall into 40+ AOA and 60 knots IAS. There is no safe way for even flight test to test all the possible ways the pilots can do the wrong thing.

Quoting jollo (Reply 15):
also because the turbulent aerodynamic regime of a stalled wing (and control surfaces) doesn't lend itself well to a closed-form solution, and an accurate set of equations for task 1 isn't - yet - available and widely accepted.

Turbulence isn't the problem; most airliners fly turbulent all the time and it's well modeled (empirically; there are still not great closed-form turbulence solutions). I think you mean separated flow; that is far less well modeled.

Tom.
 
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RE: AF 447 - Sims Misleading?

Thu Apr 05, 2012 3:20 pm

Quoting tdscanuck (Reply 16):
What flight testing (at least of commercial airliners) does not do is go 54 seconds past the stall while holding full aft and go way (way way way) past full stall into 40+ AOA and 60 knots IAS.

   That's what I meant by "... stray that far out of the envelope ...".

Quoting tdscanuck (Reply 16):
I think you mean separated flow; that is far less well modeled.

   Yes, that's what I meant. Sorreee...   
 
mandala499
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RE: AF 447 - Sims Misleading?

Thu Apr 05, 2012 5:54 pm

Quoting tommytoyz (Reply 10):
1.Is stall recovery, especially at altitude, practiced regularly? By this I do not mean stall avoidance, but recovery from a stall after it has occurred.

Prior to AF447? Some did practice "reaction to stall warning" at altitude, some don't. But no airline advocated "stall recovery at altitude"... stall recovery meaning you had entered the stall and then get out of it.

Quoting tommytoyz (Reply 10):
2. Is use of the manual trim in upset conditions practiced?

No. Stall avoidance technique SHOULD NOT require manual trim as a requirement. Too much workload. Point the nose down, then sort out the trim later.

Quoting tommytoyz (Reply 12):
Another: It seesm to me that manually adjusting trim, especially at high altitudes is critical for recovery

It is not. What you should question is, "is stall recovery (not stall avoidance) exercise warranted in the industry?" (industry: ie: not just for Airbus aircraft, but all aircraft)

Quoting tommytoyz (Reply 14):
That is why I think the following should be trained:
- high altitude upset recovery (as opposed to avoidance).
- manual trim.
- manual flying proficiency.

Manual flying proficiency is trained for... Basic High Altitude Upset Recovery, IS trained for, but one cannot simulate accurately upsets far from the normal envelope. The focus on upset recovery training in sims is on recognizing if you're upset nose up (requiring nose down inputs first before roll control) or nose down (requiring wings level first before pulling the nose back up)... using the instruments and not the motion senses... no training is done for "far from center of envelope" regimes.
Manual trim? Why? Boeing FBW and non-FBW I don't think has that trained.

Quoting tommytoyz (Reply 14):
Mentally it seems to me that the pilots panicked or froze. But why? I think it is because of a lack of comfort of hand flying, especially at altitude and in alt law to boot, imho.

This is not an AF447 problem, this, some say, is an industry problem.

However, the case of AF447 isn't the case of them not being able to get out of the stall, they were not aware they were in a stall, and if they did, it was too late! Throw in manual trim into the training if you want, but I don't think it would help if a situation arise where the crew did not realize they had entered the stall and continued to target a nose up pitch.

Note the following:
"Capt. Owens further warns, “When experiencing an actual LOC situation, the pilot’s response based upon full-flight simulation training may impact their ability to safely recover from the event while flying an aircraft.”"
This is why training in the sim focuses on recognizing impending flight controllability dangers (such as approaching a stall), and take the simulate-able action to avoid it.

Hence:

Quoting tdscanuck (Reply 16):
I'm not surprised; why would you want a pilot to even flirt with developing muscle memory that it's OK to hold aft pressure after the stall warning? The reaction at altitude must be stall warning leads to nose-down input.
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
tommytoyz
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RE: AF 447 - Sims Misleading?

Thu Apr 05, 2012 6:35 pm

Quoting tdscanuck (Reply 16):
Do you mean elevator trim or do you mean horizontal stabilizer trim?

Yes, stab trim....sorry.

Quoting tdscanuck (Reply 16):

I assume you'd advocate for both to be trained, rather than just recovery, yes?

Yes, 1) upset avoidance and 2) upset recovery

And in various laws for AB or similar aircraft.
 
tommytoyz
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RE: AF 447 - Sims Misleading?

Thu Apr 05, 2012 7:12 pm

Quoting mandala499 (Reply 18):
Quoting tommytoyz (Reply 12):
Another: It seesm to me that manually adjusting trim, especially at high altitudes is critical for recovery

It is not. What you should question is, "is stall recovery (not stall avoidance) exercise warranted in the industry?" (industry: ie: not just for Airbus aircraft, but all aircraft)

We will disagree on that. The A330 SIM experiences and the A320 crash report show the importance of manually adjusting trim on AB planes for upset recovery.

I am pretty sure that the answer to the question of should stall recovery be practiced, is a yes. In the SIM of course. Then again, that's just me.
 
tommytoyz
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RE: AF 447 - Sims Misleading?

Thu Apr 05, 2012 7:25 pm

Quoting mandala499 (Reply 18):
Hence:

Quoting tdscanuck (Reply 16):
I'm not surprised; why would you want a pilot to even flirt with developing muscle memory that it's OK to hold aft pressure after the stall warning? The reaction at altitude must be stall warning leads to nose-down input.


The SIM exercise was an attempt to replicate the AF447 LOC and then recover. It was not an endorsement of aft stick. They were just getting the plane into the same upset situation as AF447 - that's all.


Quoting mandala499 (Reply 18):
However, the case of AF447 isn't the case of them not being able to get out of the stall, they were not aware they were in a stall

I agree. Here in lie the limits of only practicing avoidance. 3 experiences pilots, similarly trained, did not recognize this, apparently IMHO.
 
mandala499
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RE: AF 447 - Sims Misleading?

Thu Apr 05, 2012 8:20 pm

Quoting tommytoyz (Reply 20):
We will disagree on that. The A330 SIM experiences and the A320 crash report show the importance of manually adjusting trim on AB planes for upset recovery.

You're advocating reactive safety for non-test pilots... a very dangerous path to go to.
Non-Test pilots are predominantly trained in preventive safety from items deemed to be too much to train for for non-test pilots.
What happened in D-AXLA was performing tests in a flight programme developed for crews trained for test flights, this lead to the crew dong checks without knowing the test-flight regime aims, and without adequate training with regards to the risks taken. Doing it at low altitude didn't help either (that check should be done at FL140... what altitude did they do it at? Much much lower!)

They were doing "low speed check in landing configuration" without mentioning the altitude and speeds outlined in the test document, and did not do the necessary checks prior to executing it (and deliberate omission was considered by a flight crew member)... and that the tests were required to be done in VMC (while they were in IMC) didn't help. They did not inform the air traffic controller they were doing the checks (which the controller had refused to allow them because the flight was not filed as a proper test flight)... since they didn't check the limit speeds prior to the test manoeuvre, they failed to realize that the limit speeds were lower than they should have been, this resulted in the THS position being in a position not suitable for stall warning recovery... They did not realize the aircraft had entered direct law (because at lower speed, a divergence due to lateral movements or roll can be enough to cause the various ADRs to diverge), which would have required manual trimming anyway as the aircraft picked up speed... this was what led to the irrecoverable stall at abnormal attitude. By the way, the aircraft did display "USE MAN PITCH TRIM", but the crew were so confused on how the airplane was reacting they didn't act upon it.

So you want non-test pilots to perform stuff that's normally reserved for test pilots, using an accident caused by non-test pilots doing test pilots stuff? How logical! What you are asking for is not improved safety, but for degraded safety!

But then, you're asking for this to be done in the sim, but then, can the sim provide accurate simulation of flight regimes so far off the normal envelope?

Quoting tommytoyz (Reply 21):
The SIM exercise was an attempt to replicate the AF447 LOC and then recover. It was not an endorsement of aft stick. They were just getting the plane into the same upset situation as AF447 - that's all.

Which was done by deliberately not doing the "stall warning recovery" and allowing the aircraft to stall. This, emphasizes on the need to make sure training modifications to ensure that non-test pilots react correctly. The AoA based stall warning should provide more than adequate reaction time as per certification requirements.

Quoting tommytoyz (Reply 21):
I agree. Here in lie the limits of only practicing avoidance. 3 experiences pilots, similarly trained, did not recognize this, apparently IMHO.

The problem was they did not act upon the 54 seconds stall warning correctly, instead of conducting "stall warning recovery at all other phases than lift-off", they did "stall warning recovery at lift-off".
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
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Jetlagged
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RE: AF 447 - Sims Misleading?

Fri Apr 06, 2012 12:46 am

Quoting jollo (Reply 15):
Setting up any computer simulation can roughly be broken down in two tasks:
1) writing the set of equations that govern the phenomenon to be simulated
2) calibrate the parameters that typically appear in such equations, based on data sets collected through an experimental campaign

To my knowledge (admittedly limited), simulation of an aircraft's dynamics in a "fully stalled" condition is difficult not only because test flights seldom stray that far out of the flight envelope (therefore there isn't sufficient data gathered for task 2), but also because the turbulent aerodynamic regime of a stalled wing (and control surfaces) doesn't lend itself well to a closed-form solution, and an accurate set of equations for task 1 isn't - yet - available and widely accepted.

The primary issue is that airliner flight tests aren't conducted in steady-state high AOA regimes. Boeing, and presumably Airbus, do fully stall test aircraft and those flight test results have to be matched as part of simulator qualification. But no attempt is made to hold the aircraft in the stall, so once the nose pitches down at the g break the test pilot executes a normal recovery manoeuvre. No "holding the aircraft fully stalled with aft stick". It's simply not safe to do this in an airliner.

Given good high AOA data to begin with you could generate empirical data to model the results of the turbulent airflow reasonably well. This model would be adjusted iteratively to suit test pilot feedback until a satisfactory solution was arrived at. Such post-stall modelling effort has to come from data providers, it can't be left to simulator manufacturers to create their own versions of post-stall aerodynamic models. The CAE model might differ considerably from the Thales model for example leading to training issues.

The question now arises how reliable is any post-stall model for training unusual attitude recovery if it can't be validated by flight tests. It's a "best guess" approximation at best, and the risk of negative training remains (just as it does presently with improper stall recovery techniques derived from simulators at the edge of the data envelope).

My basic point was that the problem does not exist because simulator design engineers don't understand stalling sufficiently, it's that the flight test data isn't there to support that. I trust you will now acknowledge this.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
Pihero
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RE: AF 447 - Sims Misleading?

Fri Apr 06, 2012 9:13 am

Funny, after hundreds of posts, we still have to come back to this subject.
Thje OP manages to pose a lot of "questionable" questions in one post :
- elevator trim
- use of the elevator trim in stall situations
- elevator authority
- simulation fidelity
- training beyond stall onset

Of course the implication is about the dangers of the 'Bus (all models are apparently lumped together, a 320 accident is used to explain how bad 330 training is...   
Let's look at the OP's propositions :

Quoting tommytoyz (Reply 10):

1.Is stall recovery, especially at altitude, practiced regularly?

(answered tens of times) No, a simulator that could reproduce post-stall aerodynamics doesn't exist.

Quoting tommytoyz (Reply 10):

2. Is use of the manual trim in upset conditions practiced?

It's more in Tom's ballpark but as a general rule, an airplane, to be certified should not need out-of-the-ordinary pilot qualities with the use of the primary flight controls.
The BEA prelim and Mandala499's Excel table show, without any doubt that each time they applied nose-down command, they had full authority, regardless of the full-up THS position and at one time the applied GA thrust.
For those who still wonder, the surface of that stabiliser is comparable to a DC-4 wing and on "mechanical back-up" training, a tenth of a degree of movement is quite an aggressive correction.
(That also shows how bizarre the sim reaction to nose-down command - stop at - 14° - is : so it's possible to pitch down from 40° NU to 14°ND, but not farther ? )
By the way, I for one would love to have the ref of that account.

Quoting tommytoyz (Reply 19):
Quoting tdscanuck (Reply 16):
Do you mean elevator trim or do you mean horizontal stabilizer trim?

Yes, stab trim....sorry.

Not wanting to be pedantic but it is called THS, for TrimmABLE horizontal Stabilizer, the inference being that one [i}could[/i] use it but normally will never have to ("normally" is also an operative word).

Quoting tommytoyz (Reply 21):
Here in lie the limits of only practicing avoidance. 3 experiences pilots, similarly trained, did not recognize this, apparently IMHO.

In an ideal world, very few people would disagree, but it means changing the very curriculum of every airline pilot, in order to include advanced aerobatics... that's an area to be thinking of before we had simulators that could be really called "Full Flight"...
The problem goes a lot further with modern FBW (for want of a more accurate description) aircraft : On the 'Bus in particular, flight control authority goes into very low speeds domain : If one looks at the regulatory definition of a stall, as any or a combination of :
1/ Buffeting : the acceleration graph doesn't show any
2/- Lack of pitch authority : as I said earlier, confirmed by Mandala499 and the BEA, they never lost it.
3/- Lack of roll control : ditto
4/- Inability to arrest descent rate : Aaaaaah ! we have that ! Problem is this is the leastt known criterium and its validity was - in all probability - rejected by PF.... And we're back to the HF involved in this accident.
Puts the piloting characteristics into another perspective, doesn't it ?

[Edited 2012-04-06 02:49:49]
Contrail designer
 
tdscanuck
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RE: AF 447 - Sims Misleading?

Fri Apr 06, 2012 2:19 pm

Quoting Pihero (Reply 24):
a simulator that could reproduce post-stall aerodynamics doesn't exist.

It's more accurate to say that a sim that reproduces post-stall aerodynamics *doesn't* exist. There's no reason the sim can't simulate it but it needs the aerodynamic coefficients from somewhere and (for some good reasons) those don't yet exist for most airliners. The tests to get them wouldn't be terribly hard to do but it's hard to see how to justify the risk against the reward. Some serious investment in CFD would do it but it would be a mammoth undertaking (see the recent G650 accident investigation for a good case of relevant CFD analysis of a stall).

Quoting Pihero (Reply 24):
Quoting tommytoyz (Reply 10):
2. Is use of the manual trim in upset conditions practiced?

It's more in Tom's ballpark but as a general rule, an airplane, to be certified should not need out-of-the-ordinary pilot qualities with the use of the primary flight controls.

That is the general rule. There's no requirement that it apply as far outside the flight envelope as AF447 got, though. I don't see anything in the available data, so far, that indicates that the aircraft didn't meet the regulatory pitch control requirements.

However, I feel like this is an artificial case. I get that tommytoyz intentionally did the wrong thing in the sim in order to setup conditions similar to the accident event; however, absent accidentally or intentionally doing the wrong thing vis a vis the stall warning, how could you get the airplane into a situation where you had to apply trim? I struggle with the idea that we need to train to recover from a situation that you can only get into by not applying your training.

Quoting Pihero (Reply 24):
The BEA prelim and Mandala499's Excel table show, without any doubt that each time they applied nose-down command, they had full authority, regardless of the full-up THS position and at one time the applied GA thrust.

This is absolutely key; this is why all the noise about THS position and locked trim and all the other stuff is not part of the accident. They had nose-down pitch authority the whole time. They demonstrated this several times all the way down to the water. The airplane was capable of nosing over and recovering from the stall at any time.

Having the stab stick at the worst possible position (in either direction) within the flight envelope is a certification case and the A330, like everyone else, would have had to demonstrate adequate pitch control (both up and down) in that situation. The only way that I can see to even get the aircraft into a situation where the trim is causing you trouble is to intentionally stick the stabilizer in place (alternate mode) and then intentionally go outside the flight envelope; that's what tommytoyz did in the sim, and it's a very interesting case, but it's hard to see how that's a realistic scenario that should be trained for by line pilots.

Test pilots (the A320 accident) is an entirely different case. They're trained quite differently for good reason.

Tom.
 
jollo
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RE: AF 447 - Sims Misleading?

Fri Apr 06, 2012 2:23 pm

Quoting Jetlagged (Reply 23):
I trust you will now acknowledge this.

I do, and I already did - in a way - by saying that, even if we had general models for separated flow regimes,

Quoting jollo (Reply 15):
That would still leave the lack of data to be solved (and *that* one would still be hard to solve: test flights do not cover stalls to 40° AOA for a reason).

Thanks for the very clear explanation.
 
tommytoyz
Topic Author
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RE: AF 447 - Sims Misleading?

Fri Apr 06, 2012 6:53 pm

While it might not be possible to reliably replicate all LOC situations in SIMS, a wings level stall certainly is possible, because all airliners are stalled by their manufacturers and that data is clearly available - within limits.

Interesting in the A330 stall recovery in the SIM, is that is took between 18-22,000feet to recover from high altitude stall, in several attempts, using proper recovery techniques without delay. With Boeing it's probably not much different, IMHO, especially if the CG location is further aft, as in modern planes these days in cruise, where fuel is pumped around to keep it aft.

Another SIM experiment in an A320 SIM, showed that a high altitude stall can easily result in a 15,000ft/min vertical speed.

The manual pitch requirement is certainly necessary for the A320 in abnormal law for stall recovery. I don't know if the A330 is different. But as Pihero says, if actual recovery from stall is never practices in the SIM, the pilots would never encounter this situation where manual trim is life or death for recovery, except in real life, which is not when the pilots should be encountering this for the 1st time, IMHO. It argues for practicing stall recovery in abnormal law in the A320.

In general, if just training avoidance were enough to prevent LOC, then LOC would never occur. But it does and can occur for many reasons, including the fault of junior pilots. AF447 is actually a good example of this. The captain walks into a situation where LOC has already occurred, but he has never been trained in recovery, as Pihero says.

For all we know the PF might have thought the "good air" was a few thousand feet higher and was trying to climb out of the air causing the problem, only to lose control and untrained in recovery.

Quoting Pihero (Reply 24):
Of course the implication is about the dangers of the 'Bus (all models are apparently lumped together, a 320 accident is used to explain how bad 330 training is...

Let's get on thing clear here. This is not about AB - OK? Period. I really don't understand your defensive stance.

And of course there is a training problem. The 2nd BEA report (P. 51 onwards) knows of 13 Unreliable Airspeed Incidents, where they also knew what the crew did. Of the 13 UAS events where the BEA had sufficient detail to know what the crew did / did not do:

"Four crews did not identify an unreliable airspeed"

And none followed the SOP 100% for UAS, none.

Manual flying
Manual flying skills are clearly atrophied to the point of being dangerous. I've read several posts by pilots who are of the same opinion, with many real examples, to the point where they feel uncomfortable or at the very least , startled when they have to take over manually.

I have always loved automation because it is indeed a tremendous innovation which makes aviation much safer. But it is not the third pilot, unless one treats automation in the same way one uses CRM with one's crew members. One ought to be able to "look through" what the autoflight system is doing and disconnect and hand-fly if one doesnt' like it. But I had crew members who would refuse to hand-fly and weren't confident in disconnecting the autothrust. I thought it was a sad thing to admit.

If anyone doubts how bad it can get, I suggest you read the Ethiopian 737-800 crash in all it's glory, were the captain hand flew his plane into the Mediterranean, after repeatedly stalling and repeatedly losing control, one too many times.

http://flightsafety.org/aerosafety-w...ld-magazine/march-2012/spiral-dive
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: AF 447 - Sims Misleading?

Sat Apr 07, 2012 1:36 am

Quoting tommytoyz (Reply 27):
Interesting in the A330 stall recovery in the SIM, is that is took between 18-22,000feet to recover from high altitude stall, in several attempts, using proper recovery techniques without delay.

I need some clarification here...by "proper recovery techniques without delay" do you mean that, with nose-down input as soon as the stall warning sounded, it took 18000-22000 feet to recover? If you're pulling all the way through the stall warning into fully developed stall that is not "without delay". Recovery from stall warning should only take about 5000 feet.

Quoting tommytoyz (Reply 27):
With Boeing it's probably not much different, IMHO, especially if the CG location is further aft, as in modern planes these days in cruise, where fuel is pumped around to keep it aft.

No current generation Boeing pumps fuel around to shift the CG aft.

Quoting tommytoyz (Reply 27):
It argues for practicing stall recovery in abnormal law in the A320.

I'm still confused about what you're trying to practice for. As far as I can tell, the only way we've figured out to get into a stall like this in an A320 (or A330) is to deliberately ignore the stall warning (i.e. do the opposite of what you're trained to do). Why would we train people in how to recover from a situation caused by not following your training?

Quoting tommytoyz (Reply 27):
In general, if just training avoidance were enough to prevent LOC, then LOC would never occur.

LOC of this type would never to line pilots if they applied the avoidance training. Shouldn't the focus be on getting the avoidance training to work to avoid the problem in the first place?

Tom.
 
mandala499
Posts: 6460
Joined: Wed Aug 29, 2001 8:47 pm

RE: AF 447 - Sims Misleading?

Sat Apr 07, 2012 4:32 am

Quoting tommytoyz (Reply 27):
And of course there is a training problem. The 2nd BEA report (P. 51 onwards) knows of 13 Unreliable Airspeed Incidents, where they also knew what the crew did. Of the 13 UAS events where the BEA had sufficient detail to know what the crew did / did not do:

"Four crews did not identify an unreliable airspeed"

And none followed the SOP 100% for UAS, none.

Therefore, I say again, the focus should be on improving crew awareness of unreliable airspeed. What the report highlighted are 13 examples of unreliable airspeed where the crew did not do the SOP. What the report did not say was how many unreliable airspeed occurences has happened. If I remember correctly, as Zeke pointed out in past topics on AF447, one airline alone has had more than 13 examples of it, and in that airline, all 13 did the right SOPs, and all lived to tell the tale as an Air Safety Report, and not an Incident/Accident report.

Quoting tommytoyz (Reply 27):
Interesting in the A330 stall recovery in the SIM, is that is took between 18-22,000feet to recover from high altitude stall, in several attempts, using proper recovery techniques without delay. With Boeing it's probably not much different, IMHO, especially if the CG location is further aft, as in modern planes these days in cruise, where fuel is pumped around to keep it aft.

Note that the exercise involved DELIBERATE entry into stall. I know of one person who deliberately stalled a 737-300 for post maintenance check flight, and yes, it takes about 3000-5000ft to get out of the stall upon immediate recovery at stall onset (one wing low and unarrestable nose down movement), and someone asked him, "would you keep the aircraft in stall for any longer?" His answer was, "Are you nuts?"

Certification requirements call for warnings to alert the crew of an impending stall, with reasonable buffer for the reasonable crew to conduct stall avoidance. There are no certification requirements for Part 25 aircraft on how the non-test-crew should deliberately hold the aircraft into a stall, go through the stall onset, and then recover from it.

Quoting tdscanuck (Reply 28):
I'm still confused about what you're trying to practice for. As far as I can tell, the only way we've figured out to get into a stall like this in an A320 (or A330) is to deliberately ignore the stall warning (i.e. do the opposite of what you're trained to do). Why would we train people in how to recover from a situation caused by not following your training?

And if he said this is not an AvsB issue, perhaps he should look into what happened to other (non-Airbus) transport category aircraft aircraft when non-test crew ignores the stall warning and not change the energy trajectory of the aircraft... oh hang on... they're all dead right?

Quoting tommytoyz (Reply 27):
If anyone doubts how bad it can get, I suggest you read the Ethiopian 737-800 crash in all it's glory, were the captain hand flew his plane into the Mediterranean, after repeatedly stalling and repeatedly losing control, one too many times.

It is not an automation issue. Please read the following paragraph from that article:
The report said that the captain’s performance likely had been affected by spatial disorientation, loss of situational awareness and subtle incapacitation that resulted from the high stress and workload induced by the late-night departure in a relatively unfamiliar aircraft and from an unfamiliar airport flanked by high terrain on one side and thunderstorms on the other, with a junior first officer, and possible indigestion and fatigue from the meal that had affected the quality of his sleep.
I suggest you read into spatial disorientation. It's not about manual/autoflight... Spatial Disorientation have caused crew disengaging the automation because they did not trust the aircraft (when they were fooled by their own bodies themselves), and manually flying it into doom, or get close to it and back! (here's one: http://en.wikipedia.org/wiki/China_Airlines_Flight_006 )
Flight Safety Foundation has also another article:
http://flightsafety.org/aerosafety-w...2011-january-2012/curbing-a-killer

I very much disagreee with your proposition on providing "reactive safety" training of which the extent require the discipline of a test-pilot... ie: for your "get into the stall then get out of it" training idea. All those stall problems ie: entry into it and lack of capability to recover, are caused by spatial disorientation.

More manual flying in IMC means either you allow pilots to practice in a spatially disorientation challenging situation, or you open the door for more accidents/incidents/mishaps due to spatial disorientation. I encourage more handflying in VMC, but in IMC, more handflying can go either way!

If you want more hand flying in all conditions, perhaps we should also look into replacing our flawed sensory inputs with aviation grade IRS and wire it into our brain.
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
tommytoyz
Topic Author
Posts: 1195
Joined: Thu Jan 18, 2007 9:08 am

RE: AF 447 - Sims Misleading?

Sat Apr 07, 2012 6:28 am

Quoting tdscanuck (Reply 28):
I need some clarification here...by "proper recovery techniques without delay" do you mean

I mean recovery from a stall. Not the approach of a stall.

Quoting tdscanuck (Reply 28):
As far as I can tell, the only way we've figured out to get into a stall like this in an A320 (or A330) is to deliberately ignore the stall warning

The A320 crash analysis, points to just one way in which you can stall without ignoring the stall warning - AoA not indicating properly - AoA indicators can malfunction and freeze like anything else, like in this case. In none of the reports I've read on that crash, did it say the pilots failed to react to the stall warning, as it was already stalled when it sounded. In direct law the trim freezes and manual retrim is mandatory if the trim was nose up, or you will not recover no matter what else you do.

Another way is a power on stall or dynamic stall. This is similar to what AF447 did. The stall warning will sound of course, but the AoA changes so rapidly that measured in time, there is basically no warning and no time to avoid the stall. One the stall warning sounds, it's too late.

Basic airmanship can not be left at the door and allowed to atophy.

Quoting tdscanuck (Reply 28):
Shouldn't the focus be on getting the avoidance training to work to avoid the problem in the first place?

Yes, I agree. But sometimes trouble finds you anyway.

Quoting mandala499 (Reply 29):
one airline alone has had more than 13 examples of it, and in that airline, all 13 did the right SOPs,

It is not really known beyond what they reported, what they actually did. The other 13 are highlighted, because their actions are known.

Quoting mandala499 (Reply 29):
it takes about 3000-5000ft to get out of the stall upon immediate recovery at stall onset

Stall onset altitude requirements, wow - Even that amount is impressive to me. I am sure it increase with altitude as well.Yet, from a fully developed stall, occurring at high altitude, it becomes clear that enormous amounts of altitude are needed to recover - especially if secondary stalls occur, which are not uncommon.

Quoting mandala499 (Reply 29):
Spatial Disorientation have caused crew disengaging the automation because they did not trust the aircraft

This was the opposite. He was confused and wanted the AP to take over from his manual flying. There is no reason for him to have been disoriented. He didn't even trim the aircraft. Basic airmanship was gone. If a pilot, much less a captain can't do a basic departure manually, he shouldn't be flying or needs to practice manual flying in the SIM until he can do at least that. At that low threshold of ability, pray nothing malfunctions...

This is not about B or AB. I am talking about airmanship and training. A professional airman should never feel nervous about manually flying the aircraft at any time and should be able to demonstrate that ability.
 
tdscanuck
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RE: AF 447 - Sims Misleading?

Sat Apr 07, 2012 7:03 am

Quoting tommytoyz (Reply 30):
Another way is a power on stall or dynamic stall. This is similar to what AF447 did. The stall warning will sound of course, but the AoA changes so rapidly that measured in time, there is basically no warning and no time to avoid the stall. One the stall warning sounds, it's too late.

If that's actually true, the aircraft does not comply with the FAR's and the type certificate should be pulled. If the stall warning system doesn't provide sufficient warning to avoid a stall that requires unusual pilot action and skill to recover it's un-compliant on its face.

Power-on and dynamic stalls are a certification requirement; there's no way this could have passed stall certification without a documented deviation or alternate method of compliance.

Tom.
 
tommytoyz
Topic Author
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RE: AF 447 - Sims Misleading?

Sat Apr 07, 2012 8:33 am

Quoting tdscanuck (Reply 31):
If that's actually true, the aircraft does not comply with the FAR's

It is true, any aircraft can do a dynamic stalls. I see you like to quote regs and rules. So please quote for me the EXACT FAA rule you are referring to....thank you so much, so that I can read up on it and we can all discuss it here.
Thank you
 
mandala499
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RE: AF 447 - Sims Misleading?

Sat Apr 07, 2012 10:20 am

Quoting tommytoyz (Reply 30):
I mean recovery from a stall. Not the approach of a stall.

I'd stop insuring airlines that asks crew to recover from stalls (not approach to stall) in a jetliner!

Quoting tdscanuck (Reply 31):
If that's actually true, the aircraft does not comply with the FAR's and the type certificate should be pulled. If the stall warning system doesn't provide sufficient warning to avoid a stall that requires unusual pilot action and skill to recover it's un-compliant on its face.

He missed out on why the AoA vanes failed to provide a timely warning...
He also missed out that the crew of D-AXLA missed out on performing limit speed checks which would have indicated something was wrong with the aircraft and therefore unsuitable to perform the Low Speed Flight check.
He also missed out that the crew were supposed to perform the check at FL140 (as per manufacturer test/check flight guidelines/instructions) and not 3000ft! (as per what the BEA pointed out on).

Quoting tommytoyz (Reply 32):
It is true, any aircraft can do a dynamic stalls. I see you like to quote regs and rules. So please quote for me the EXACT FAA rule you are referring to....thank you so much, so that I can read up on it and we can all discuss it here.

Looks like we're degrading the discussion into who knows more than the other?
Anyways, the regs? Go to: http://t.co/nuFbSeQe
Enjoy 25.201 until 25.207
From 25.201:
(d) The airplane is considered stalled when the behavior of the airplane gives the pilot a clear and distinctive indication of an acceptable nature that the airplane is stalled. Acceptable indications of a stall, occurring either individually or in combination, are—
(1) A nose-down pitch that cannot be readily arrested;
(2) Buffeting, of a magnitude and severity that is a strong and effective deterrent to further speed reduction; or
(3) The pitch control reaches the aft stop and no further increase in pitch attitude occurs when the control is held full aft for a short time before recovery is initiated.

One of the three meets the stall demonstration requirements (reserved for test pilots)

From 25.203:
(a) It must be possible to produce and to correct roll and yaw by unreversed use of the aileron and rudder controls, up to the time the airplane is stalled. No abnormal nose-up pitching may occur. The longitudinal control force must be positive up to and throughout the stall. In addition, it must be possible to promptly prevent stalling and to recover from a stall by normal use of the controls.
Aircraft must maintain positive longitudinal control up to and throughout the stall, to enable prompt preventive action to avoid a stall, and also also to (not promptly) recover from the stall using normal controls. AF447 FDR and the 330 sim tests, and also the D-AXLA shows that the aircraft can recover... except that D-AXLA did not have sufficient altitude to recover (tests for the A320 Low Speed Flight check should have been done at FL140, and not 3000ft.

From 25.207:
(a) Stall warning with sufficient margin to prevent inadvertent stalling with the flaps and landing gear in any normal position must be clear and distinctive to the pilot in straight and turning flight.
Note: SUFFICIENT margin!

(f) The stall warning margin must be sufficient in both non-icing and icing conditions to allow the pilot to prevent stalling when the pilot starts a recovery maneuver not less than one second after the onset of stall warning in slow-down turns with at least 1.5 g load factor normal to the flight path and airspeed deceleration rates of at least 2 knots per second. When demonstrating compliance with this paragraph for icing conditions, the pilot must perform the recovery maneuver in the same way as for the airplane in non-icing conditions. Compliance with this requirement must be demonstrated in flight with—
(1) The flaps and landing gear in any normal position;
(2) The airplane trimmed for straight flight at a speed of 1.3 VSR; and
(3) The power or thrust necessary to maintain level flight at 1.3 VSR.

Note: Sufficient margin to act upon to get out of the stall, using the standard recovery maneuver.

(h) For flight in icing conditions before the ice protection system has been activated and is performing its intended function, with the ice accretion defined in appendix C, part II(e) of this part, the stall warning margin in straight and turning flight must be sufficient to allow the pilot to prevent stalling without encountering any adverse flight characteristics when:
(1) The speed is reduced at rates not exceeding one knot per second;
(2) The pilot performs the recovery maneuver in the same way as for flight in non-icing conditions; and
(3) The recovery maneuver is started no earlier than:
(i) One second after the onset of stall warning if stall warning is provided by the same means as for flight in non-icing conditions; or
(ii) Three seconds after the onset of stall warning if stall warning is provided by a different means than for flight in non-icing conditions.
(i) In showing compliance with paragraph (h) of this section, if stall warning is provided by a different means in icing conditions than for non-icing conditions, compliance with §25.203 must be shown using the accretion defined in appendix C, part II(e) of this part. Compliance with this requirement must be shown using the demonstration prescribed by §25.201, except that the deceleration rates of §25.201(c)(2) need not be demonstrated.

So, the stall warning must be enough for the pilot to recover by initiating the recovery within 1 second (if identical method for non-icing condition), or 3 seconds (if non-identical means of warning than in non-icing condition).

In the case of AF447, stall warning from 2:10:51, onset of stall at 2:11:31, a full 40 seconds. Had they conducted the correct stall recovery procedure of reducing pitch and adding power in the prescribed time required by certification requirement, they could have survived, as THS position was still at less than 4 degrees nose up. Even if they conducted it late, even as late as the onset of stall, they could have recovered. The aircraft maintained positive longitudinal control towards recovery throughout, even at 13.6 nose up THS position. The certification does not specify how much of an altitude loss it should take to recover (as per 25.203(a)).

If you don't like the FAR25, then write to the FAA and ask for a rewriting of the rules. The A320, and A330, and other aircraft that has had type certification passed, comply with the FAR25 or similar requirement to the level deemed adequate by the certificate issuing authority (and also to the FAA as the 320 and 330 type certificate must be endorsed by the FAA for use on N-reg aircraft (by deciding that the foreign type certificate meets FAR25 requirements, or get it's own FAA type certificate as per FAR25).

Now if as you said:

Quoting tommytoyz (Reply 30):
The stall warning will sound of course, but the AoA changes so rapidly that measured in time, there is basically no warning and no time to avoid the stall. One the stall warning sounds, it's too late.

Then what Tdscanuck said that the type certificate should be revoked, or operational approval of the aircraft type on US soil should be immediately suspended until further notice (ie: recertification required).
That hasn't happened yet has it? If you, Tommytoyz, think that what you said is true, then please, write to the FAA and ask for a review or revocation of the type certification of the aircraft you suspect cannot recover due to "lack of adequate margin for stall warnings" or due to "AoA changing rapidly that there is no time to avoid the stall"...
Again, please read on why D-AXLA's stall warning screwed up... you seem to have missed that and branded the aircraft as "AoA not indicating properly - AoA indicators can malfunction and freeze like anything else"... the airworthiness of the aircraft was violated prior to the departure due to improper rinsing of the aircraft 3 days beforehand, and no one saw the implications beforehand!
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
mandala499
Posts: 6460
Joined: Wed Aug 29, 2001 8:47 pm

RE: AF 447 - Sims Misleading?

Sat Apr 07, 2012 10:56 am

Quoting tommytoyz (Reply 30):
This was the opposite. He was confused and wanted the AP to take over from his manual flying. There is no reason for him to have been disoriented.

This shows exactly that you do not understand spatial disorientation. He was confused, ie: he was spatially disorientated.
From the very same article you mentioned:
"The report said that the captain%u2019s performance likely had been affected by spatial disorientation, loss of situational awareness and subtle incapacitation that resulted from the high stress and workload induced by the late-night departure in a relatively unfamiliar aircraft and from an unfamiliar airport flanked by high terrain on one side and thunderstorms on the other, with a junior first officer, and possible indigestion and fatigue from the meal that had affected the quality of his sleep."
Note that spatial disorientation was put before loss of situational awareness (effect of spatial disorientation) and subtle incapacitation (to which spatial disorientation further incapacitates the captain from making sound judgement/action).

Your mindset is on reactive safety, which the aviation industry from long ago have accepted, is more dangerous than proactive/preventive safety. Reactive safety action is the domain of conventional decision making process (which is deadly if applied in the cockpit), reactive safety in the cockpit is only for non-preventative reactions (eg: unforeseen), for what is foreseen, or trending towards an occurence requiring action, preventive action is what is needed. Preventive action in the cockpit is a key ingredient in aviation decision making process.

Quoting tommytoyz (Reply 30):
The A320 crash analysis, points to just one way in which you can stall without ignoring the stall warning - AoA not indicating properly - AoA indicators can malfunction and freeze like anything else, like in this case. In none of the reports I've read on that crash, did it say the pilots failed to react to the stall warning, as it was already stalled when it sounded. In direct law the trim freezes and manual retrim is mandatory if the trim was nose up, or you will not recover no matter what else you do.

Where does it say that manual retrim is mandatory if the trim was nose up?
What the BEA recommended was:
That EASA undertake a safety study with a view to improving the certification standards of warning systems for crews during reconfigurations of flight control systems or the training of crews in identifying these reconfigurations and determining the immediate operational consequences.
and:
In addition, the manual use of pitch trim, which is not included as a reminder in the approach-to-stall procedures, only occurs very rarely in operation and occasionally in training. Several investigations undertaken following accidents and incidents (including that mentioned in 2.4) tend to call into question the procedures relating to approach-to-stall techniques for all types of modern aeroplane. Studies are currently under way with a view to improving these procedures.
Consequently, the BEA takes into account these elements and also recommends:
"That EASA, in cooperation with manufacturers, improve training exercises and techniques relating to approach-to-stall to ensure control of the aeroplane in the pitch axis."

Note: Improve training exercises and techniques relating to approach-to-stall.
Training exercises as far as I know has included improvements (and including changes to power application during approach-to-stall recovery, but the reference document is locked under non-disclosure clauses on my end), but does not include manual trimming.

Now back to your "ranting" (if I may say it as such):
What you missed the point on the 320 crash analysis is a LOT! D-AXLA is a case where lack of preventive/cautionary measures were not taken.
Where should I start?
1. D-AXLA pilots did not perform adequate checks prior to the Low Speed Flight check, as mentioned on pages 17, 32, 48, 86, 92, and 96 of the report.
2. Checking the limit speed prior to the Low Speed Flight check was a requirement.
3. Aircraft showed much lower limit speeds because the crew ignored the CHECK GW message on the FMGC MCDU, this warning is generated when the gross weight calculated by the FAC differs with the FMGC by an amount greater than 7 (seven) tonnes (page: 32, 48, 92), the consequence of this is that a lower limit speed was generated b the FAC than what would be adequate.
4. By not taking the necessary preventive action stated in #1 & #2, solely depending on reactive action, proved to be inadequate. An example where the right preventive action was taken on another aircraft and crew on a check flight in August 2002 was shown on page 80 of D-AXLA's report, where upon seeing the CHECK GW message, the crew decided not to continue the check flight... and lived.
The FAC calculates the GW based on the AoA and the particular flight regime. Ignoring the CHECK GW message and then doing a test relying on the AoA vane, is not a smart idea.
5. The reason why the FAC miscalculated the limit speeds, was due to the AoA vanes' movement blocked by icing caused by moisture stuck within the sensor and plates inside. This is because during a previous rinsing of the aircraft, the AoA vanes were not protected as it should have been (page 55, 89). Therefore the Stall Warning, when activated, was not adequate. The aircraft's airworthiness had effectively been violated without anyone realizing it. The last two safety mechanism from disaster was ignored (CHECK GW on FMGC MCDU, and limit speed checks prior to the Low Speed Flight check maneuver).
6. They did the check manoeuver at a much lower altitude than was prescribed in the test/check flight documentation (FL140, but did it at 3000ft).

So, preventive action was not taken, leading to the catastrophe.

In the case of D-AXLA, the stall warning activated later than it should, therefore, the aircraft tried to recover later than it normally would, and obviously, it couldn't given the low height it was at.

Failing to check the limit speeds prior to the Low Speed Flight test in D-AXLA's case had other unforeseen consequences. The erroneous FAC limit speeds were not cross checked, it gave a very low value, which opened the aircraft to ADR disagreement risks arising from asymmetrical airflow at low speed due to roll/yaw movements that can occur at stall onsets. In this case, the diverging speeds was great enough to cause ADR1 and ADR2 to disagree (and the FBW doesn't know if ADR 1&3 or ADR2 that was providing the correct input), leading to degradation to Alternate Law, but since the aircraft had it's landing gear down, it reverted to Direct Law. Had they checked the limit speed as they should have prior to the test, the accident would have been prevented.

The abnormal law should have latched back on to Alternate once the aircraft recovered, but the aircraft latched to direct law, due to the ADR disagreeing and landing gear down. (this is why Low Speed Flight Check should be done at weights that would reduce risk of latching to direct law due to ADR disagreeing, and at FL140, which should have allowed for recovery given the situation).

As poor as the crew prepared for the final check manoevre, the mishap would have been prevented had the correct rinsing procedure be done several days before the accident.

To do this test at 3000ft when it should be done at FL140, is not wise, and proved fatal. Had they done it at FL140, they could have recovered. If you're worried about stalls on approaches, well, crew are supposed to check their approach speeds prior to normal approach and also lookout for FMGC calculated speed anomalies.

Quoting tommytoyz (Reply 30):
Stall onset altitude requirements, wow - Even that amount is impressive to me. I am sure it increase with altitude as well.

That guy who did the stalls on the 733 was not qualified to do so, and that post maintenance checks only require for stick shaker activation at the correct point and then perform the recovery. What he did was blatant disregard of safety and been told not to do it again (he hasn't done it again in that company) and he has left that company prior to reprimand from the safety department.
So, you got documentation on stall onset recovery altitude-consumption requirement?

Quoting tommytoyz (Reply 30):
Basic airmanship can not be left at the door and allowed to atophy.

So, where was the failure in basic airmanship in the case of D-AXLA? Not the inability to recover, but in the preset to it, which is not bothering to check the limit speed prior to the check (which was a requirement), and doing it at such a low level!

Basic airmanship include preventive actions, something that they did not do in this accident. (ref: checking the limit speeds prior to doing the checks)

Quoting tommytoyz (Reply 30):
A professional airman should never feel nervous about manually flying the aircraft at any time and should be able to demonstrate that ability.

A professional airman should also perform the required check prior to doing a maneuver where a check is required. A professional airman should also not go against a manufacturer's recommendation for a particular check/manoeuvre, such as doing the Low Speed Flight check at 3000ft when he was supposed to do it at FL140, and not even file the flight as a test flight to the ATC!
Tommytoyz, you're chasing the wrong airmanship problem here!

Quoting tommytoyz (Reply 30):
It is not really known beyond what they reported, what they actually did. The other 13 are highlighted, because their actions are known.

I see, you want to play that game again?   
OK, since you said:

Quoting tommytoyz (Reply 32):
So please quote for me the EXACT FAA rule you are referring to....thank you so much

And that I had fulfilled your request so that you can read up on it and we can all discuss it here, therefore I ask you for the following:

Quoting tommytoyz (Reply 30):
In direct law the trim freezes and manual retrim is mandatory if the trim was nose up,

Please find me or quote me the exact documentation wording from an Airbus FBW aircraft FCOM/QRH/FCTM or a regulatory rule (not accident report recommendation) you are referring to, so that we can read it up and discuss it here.

Mandala499
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
tommytoyz
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RE: AF 447 - Sims Misleading?

Sat Apr 07, 2012 1:33 pm

Quoting mandala499 (Reply 33):
He missed out on why the AoA vanes failed

The "why" doesn't matter in this illustration. The point is that it can happen.

Every single airplane can do a dynamic stall, did you not know that? So how can it then be against any certification requirement, since they are all already certified? Do you want to revoke the certificates? Man it makes no sense what you guys are saying.

In addition, this thread is about SIMS. Please stay on topic or start your own.

Have a nice Easter Celebration.
 
tdscanuck
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RE: AF 447 - Sims Misleading?

Sat Apr 07, 2012 5:27 pm

Quoting tommytoyz (Reply 32):

Quoting tdscanuck (Reply 31):
If that's actually true, the aircraft does not comply with the FAR's

It is true, any aircraft can do a dynamic stalls.

You selectively clipped what I said; all aircraft can do dynamic stalls. It's a certification requirement that that they do dynamic stalls *and be recoverable with normal controls*. It's the latter part you dropped out. If the airplane can only be recovered from a dynamic power-on stall with *non-normal* control input, like doing manual trim in the middle of a stall recover, then it doesn't comply with 25.203, among others. mandala499 proved an excellent discussion in answer to your request and you seem to be ignoring it.

Quoting tommytoyz (Reply 32):
I see you like to quote regs and rules. So please quote for me the EXACT FAA rule you are referring to....

See mandala499's post. The specific one I was thinking of 25.203 but they're all relevant.

Quoting tommytoyz (Reply 35):
Every single airplane can do a dynamic stall, did you not know that?

Yes, I know that. In fact, I said that. You *have* to do a dynamic stall to get certified. Did you not know that the FAR's require that you be able to recover from a dynamic stall using only normal control inputs? Because you flat out stated that, at least in the sim, you can't.

Quoting tommytoyz (Reply 35):
So how can it then be against any certification requirement, since they are all already certified?

That was the point; you're stated that an A320/A330 can't get out of power-on stall without manual stab trim. That's a clear non-compliance. However, since the airplane is certified, Airbus must have demonstrated that the plane doesn't require non-normal control inputs to recover, therefore your assessment that manual trim is required must be incorrect.

Quoting tommytoyz (Reply 35):
Do you want to revoke the certificates?

No, because I don't think it's non-compliant. You have claimed it's non compliant yet, so far, have not explained why the regulators would continue to let such an obviously non-compliant aircraft fly.

The most likely explanation is that your sim experiment (since this is a sim discussion) went outside the data validity of the sim. Airbus already proved that this is not what happens in actual flight.

Tom.
 
tommytoyz
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RE: AF 447 - Sims Misleading?

Sat Apr 07, 2012 9:25 pm

Quoting tdscanuck (Reply 31):
Quoting tommytoyz (Reply 30):
Another way is a power on stall or dynamic stall. This is similar to what AF447 did. The stall warning will sound of course, but the AoA changes so rapidly that measured in time, there is basically no warning and no time to avoid the stall. One the stall warning sounds, it's too late.

If that's actually true, the aircraft does not comply with the FAR's and the type certificate should be pulled. If the stall warning system doesn't provide sufficient warning to avoid a stall that requires unusual pilot action and skill to recover it's un-compliant on its face.

I am very clearly talking about the stall warning here. You are talking about the stall recovery requirements. We actually both agree. Maybe the problem is because you think I said things I actually never have. See below:

Quoting tdscanuck (Reply 36):
Did you not know that the FAR's require that you be able to recover from a dynamic stall using only normal control inputs? Because you flat out stated that, at least in the sim, you can't.

I never said that. Please retract your statement and stop doing this. Thank you. Putting words into people's mouths is very low.

Quoting tdscanuck (Reply 36):
you're stated that an A320/A330 can't get out of power-on stall without manual stab trim.

No, that's not what I said either. Your are conflating several things I said. Please retract this statement as well.

Perhaps you are confused on what I said about the A320. It was not a dynamic stall, if that is what you mean. The very narrow condition the A320 crew found themselves in (not A330), does require manually retrim to recover and I said so very specifically what those narrow conditions are. Go back an reread the very specific conditions I stated were recovery isn't possible without manual retrim, wihout leaving anything out please, thank you.

In that situation I described, the A320 actually displayed “Use Man Pitch Trim” in amber on the primary flight displays - and the crew ignored it. So even the plane was telling the the crew the urgent requirement to manually reset trim. I said nothing about replicating this in the SIM. It really happened and so did the crash.

Quoting tdscanuck (Reply 36):
You have claimed it's non compliant yet, so far, have not explained why the regulators would continue to let such an obviously non-compliant aircraft fly.

I have made no such claim, so there is nothing to explain. You are arguing against a ghost. Please retract this statement and stop putting words in my mouth.

Quoting tdscanuck (Reply 36):
The most likely explanation is that your sim experiment (since this is a sim discussion) went outside the data validity of the sim. Airbus already proved that this is not what happens in actual flight.

That is true and goes to the question how valid or how good are the SIMS. Can they mislead? This is a very good and important topic to continuously examine and improve, IMHO. It will remain challenging because neither AB nor anyone else can possibly get their aircraft into every conceivable situation in real life. So the SIM developers have to make assumptions. Tricky is you ask me and not always done well as the original article states.

I think I made my point that relying solely on AoA warnings to avoid stalls is only as reliable as the AoA data itself, it and doesn't help in dynamic stalls anyway.

IMHO. there is no substitute for basic airmanship and recovery training from stalls and LOC, especially at high altitudes. That's were the SIMS come in. You would rather just train avoidance - fine. We can agree to disagree.

I try to remain professional, but it is hard when false statements are continuously attributed to me. Please stop doing that and we'll be fine.

[Edited 2012-04-07 14:28:49]

[Edited 2012-04-07 14:29:42]
 
Daysleeper
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RE: AF 447 - Sims Misleading?

Sat Apr 07, 2012 11:50 pm

Quoting tommytoyz (Reply 37):
Perhaps you are confused on what I said about the A320. It was not a dynamic stall, if that is what you mean. The very narrow condition the A320 crew found themselves in (not A330), does require manually retrim to recover and I said so very specifically what those narrow conditions are. Go back an reread the very specific conditions I stated were recovery isn't possible without manual retrim, wihout leaving anything out please, thank you.

Just a quick question in regards to this, but I was under the impression that one of the major contributing factors to this accident was a malfunction with the AoA sensor/s. This being the case then how can you draw any meaningful conclusions from it?

Surely you should assume a fully functional aircraft when testing stall systems, otherwise in order to be a stall where manual re-trim is required for recovery then you also have to assume that the AoA sensor has malfunctioned.
 
tommytoyz
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RE: AF 447 - Sims Misleading?

Sat Apr 07, 2012 11:55 pm

Quoting mandala499 (Reply 34):
Please find me or quote me the exact documentation wording from an Airbus FBW aircraft FCOM/QRH/FCTM or a regulatory rule (not accident report recommendation) you are referring to, so that we can read it up and discuss it here.
http://www.bea.aero/en/enquetes/perpignan/perpignan.php

The aeroplane stalled again, this time irrecoverably, bearing in mind the aeroplane’s altitude
and without any crew inputs on the trim wheel and the thrust levers.
.........

The loss of control was thus caused by a thrust increase performed with a
full pitch-up horizontal stabilizer position.
.......

This seems to indicate that none of them were aware that the automatic trim system, which relieves the pilot of any actions to trim the aeroplane, was no longer available.

..........

Since the systems’ responses in the course of the flight were consistent with constant local angle
of attack values,it is possible to limit the origin of the malfunction to the
following hypotheses:
- A simultaneous failure in the acquisition chain for each of the local angle
of attack values;
- A physical and quasi-simultaneous blockage of the two angle of attack
sensor vanes.


Good enough for me.
 
tommytoyz
Topic Author
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RE: AF 447 - Sims Misleading?

Sun Apr 08, 2012 12:20 am

Quoting Daysleeper (Reply 38):
Just a quick question in regards to this, but I was under the impression that one of the major contributing factors to this accident was a malfunction with the AoA sensor/s. This being the case then how can you draw any meaningful conclusions from it?

Different people will draw different conclusions, I am sure. For me - better training in general and especially in stall recovery as well as avoidance, rather than just avoidance. And better training in general on basic airmanship, manual flying, flying manually in direct law, etc....

By retrimming manually after the 1st stall they would have survived. But they didn't do that, so they couldn't recover from the second one. Basic airmanship would have avoided the 1st stall, and better training would have reminded them of the need to trim manually in direct law on the 2nd stall, IMHO.

From the report:

Under the combined effect of the thrust
increase , the increasing speed and the horizontal stabilizer still at the pitch-up
stop, the aeroplane was subject to pitch-up moment that the Captain could
not manage to counter, even with the sidestick at the nose-down stop. The
exchanges between the pilots at this time show that they did not understand
the behaviour of the aeroplane. In particular, the aeroplane’s lack of reaction
to the nose-down control input did not draw their attention to the position of
the horizontal stabilizer and the loss of the auto-trim function.


[Edited 2012-04-07 17:22:22]
 
tdscanuck
Posts: 8572
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RE: AF 447 - Sims Misleading?

Sun Apr 08, 2012 1:10 am

Quoting tommytoyz (Reply 37):
I am very clearly talking about the stall warning here.

In that case, the stall warning system isn't compliant with 25.1301.

Quoting tommytoyz (Reply 37):
Quoting tdscanuck (Reply 36):
Did you not know that the FAR's require that you be able to recover from a dynamic stall using only normal control inputs? Because you flat out stated that, at least in the sim, you can't.

I never said that.

You said, quoted in full:

Quoting tommytoyz (Reply 20):
The A330 SIM experiences and the A320 crash report show the importance of manually adjusting trim on AB planes for upset recovery.
Quoting tommytoyz (Reply 27):
The manual pitch requirement is certainly necessary for the A320 in abnormal law for stall recovery.

If that does *not* mean that manual trim adjustment is necessary to stall recovery, then I'm extremely confused.

Quoting tommytoyz (Reply 37):
The very narrow condition the A320 crew found themselves in (not A330), does require manually retrim to recover and I said so very specifically what those narrow conditions are.

Exactly. And if you require manual trim to recover from inside the flight envelope, then it's not compliant with the FARs. If they're outside the flight envelope then I'm not really sure what the overall point is; there are zero guarantees of what the airplane will do any more than a little bit outside the flight envelope.

Quoting tommytoyz (Reply 37):
In that situation I described, the A320 actually displayed “Use Man Pitch Trim” in amber on the primary flight displays - and the crew ignored it. So even the plane was telling the the crew the urgent requirement to manually reset trim.

The plane wasn't telling the crew that they had to reset the trim wheel to recover; it was telling them that *it* wouldn't reset the trim and, *if* the crew wanted to trim, they'd have to do it themselves. If trim were actually required to recover from a stall warning, it wouldn't be certifiable.

Tom.
 
tommytoyz
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RE: AF 447 - Sims Misleading?

Sun Apr 08, 2012 3:58 am

Quoting tdscanuck (Reply 41):
And if you require manual trim to recover from inside the flight envelope, then it's not compliant with the FARs.

Well tell that to the FAA. On the A320:

1. If the trim freezes full up in direct law - which it can, but not necessarily, and
2. If you add power as per SOP on stall warning at the time
3. Then, given these circumstances, manual trim MUST be adjust to recover from the stall, or you will not recover.
4. An Amber message on an A320 means - Action required. The message in this crash, which was ignored, was in amber, instructing them to adjust trim manually. It does not mean please monitor or be aware, etc...it means action is required.

Quoting tdscanuck (Reply 41):
If they're outside the flight envelope then I'm not really sure what the overall point is; there are zero guarantees of what the airplane will do any more than a little bit outside the flight envelope.

You'll have to define what you mean by inside and outside the envelope. Are you saying AB doesn't know how their aircraft will behave in a stalls? Or that they have no recovery procedures?

Just because some airlines choose not to train recovery but only train avoidance does not mean that upsets and LOC are impossible or outside the manufacturer's "envelope" or that there is no recovery procedure. Stalling is well within any airliners "envelope". It will not fall apart, disintegrate or crash because of a stall. It will only do that if the crew don't know how to recover from one and follow the proper established recovery procedure.
 
tdscanuck
Posts: 8572
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RE: AF 447 - Sims Misleading?

Sun Apr 08, 2012 4:18 am

Quoting tommytoyz (Reply 42):
You'll have to define what you mean by inside and outside the envelope.

Operations within the limitations defined in the AFM is "inside the envelope." Beyond the limits is "outside."

Quoting tommytoyz (Reply 42):
Are you saying AB doesn't know how their aircraft will behave in a stalls?

No.

Quoting tommytoyz (Reply 42):
Or that they have no recovery procedures?

No.

I'm saying that there is no point in training crews for recovery from operation outside the flight envelope, which is where AF447 ended up, because there is no data to tell you what the airplane will do outside the flight envelope. You need to train to keep the aircraft in the envelope. There is a very small fudge factor because the OEM has to go slightly outside the envelope to make sure that the plane is OK at the boundaries but that doesn't help when you blow right past the boundary headed for 40degrees AOA.

The same procedure that works at one flight condition could kill you in another and the line can be very thin between the two. You could have total control reversal if you get far enough outside the envelope (several current designs have this in pitch at high g), in which case your recovery procedures have to be backwards but you have no way to know that until you run into the problem.

Quoting tommytoyz (Reply 42):
Just because some airlines choose not to train recovery but only train avoidance does not mean that upsets and LOC are impossible or outside the manufacturer's "envelope" or that there is no recovery procedure.

Agreed, although it's *extremely* difficult (though not impossible) to get outside the flight envelope without doing something wrong first.

Quoting tommytoyz (Reply 42):
Stalling is well within any airliners "envelope".

Yes, which is why there is a stall warning system and why you have to react to the stall warning system; not ignore it until you fully stall the airplane.

Quoting tommytoyz (Reply 42):
It will not fall apart, disintegrate or crash because of a stall. It will only do that if the crew don't know how to recover from one and follow the proper established recovery procedure.

And, in order to even need the recovery procedure at all, the crew has to screw up the avoidance procedure. Hence my original question: why would you train people to recover from a situation that you can only get into by ignoring your training?

Quoting tommytoyz (Reply 42):
On the A320:
1. If the trim freezes full up in direct law - which it can, but not necessarily, and
2. If you add power as per SOP on stall warning at the time
3. Then, given these circumstances, manual trim MUST be adjust to recover from the stall, or you will not recover.

I defer to the Airbus drivers on this, but this implies that the aircraft has no nose-down elevator authority in the specified condition; I'm very intrigued how the regulators bought off on that.

Quoting tommytoyz (Reply 42):
4. An Amber message on an A320 means - Action required. The message in this crash, which was ignored, was in amber, instructing them to adjust trim manually. It does not mean please monitor or be aware, etc...it means action is required.

Straight from the A320 manuals:
"AMBER: The flight crew should be aware of the configuration or failure, but need not take immediate action."

Tom.
 
tommytoyz
Topic Author
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RE: AF 447 - Sims Misleading?

Sun Apr 08, 2012 7:31 am

Quoting tdscanuck (Reply 43):
Agreed, although it's *extremely* difficult (though not impossible) to get outside the flight envelope without doing something wrong first.

But possible, and has happened many times and will happen in the future, IMHO.

Quoting tdscanuck (Reply 43):
Yes, which is why there is a stall warning system and why you have to react to the stall warning system; not ignore it until you fully stall the airplane.

And if the stall warning system fails, as in the Perpignan accident?

Quoting tdscanuck (Reply 43):
And, in order to even need the recovery procedure at all, the crew has to screw up the avoidance procedure.

No. If the stall warning fails or any number of things, the crew need not have screwed up. Even if one of the crew members did, shouldn't the others be able to recover?

Quoting tdscanuck (Reply 43):
Straight from the A320 manuals:
"AMBER: The flight crew should be aware of the configuration or failure, but need not take immediate action."

Not immediate, but action required = yes. I've not said anything to the contrary. There are higher priorities, but amber says this must be done.
 
mandala499
Posts: 6460
Joined: Wed Aug 29, 2001 8:47 pm

RE: AF 447 - Sims Misleading?

Sun Apr 08, 2012 8:51 am

Quoting tommytoyz (Reply 39):
Good enough for me.

Not good enough for me! I asked you:

Quoting mandala499 (Reply 34):
And that I had fulfilled your request so that you can read up on it and we can all discuss it here, therefore I ask you for the following:

Quoting tommytoyz (Reply 30):
In direct law the trim freezes and manual retrim is mandatory if the trim was nose up,

Please find me or quote me the exact documentation wording from an Airbus FBW aircraft FCOM/QRH/FCTM or a regulatory rule (not accident report recommendation) you are referring to, so that we can read it up and discuss it here.

What you quoted in reply 39 does not represent "manual retrim is mandatory if the trim was nose up".
No, I am not putting words in your mouth. You are doing it to yourself.
And I thought you said:

Quoting tommytoyz (Reply 35):
In addition, this thread is about SIMS. Please stay on topic or start your own.

So, why are you continuing non sim discussions in this topic? In your very own words: "please stay on topic or start your own", Oh hang on... I get it... you're just up to stirr people!   

Quoting tommytoyz (Reply 40):
By retrimming manually after the 1st stall they would have survived. But they didn't do that, so they couldn't recover from the second one. Basic airmanship would have avoided the 1st stall, and better training would have reminded them of the need to trim manually in direct law on the 2nd stall, IMHO.

Question:
Had they done the Low Speed Flight Test as per prescribed in the documentation at FL140, and had checked the limit speeds, do you think the accident would have happened?
Question:
You talk about "airmanship", do you not think that performing Low Speed Flight Test at an altitude 11,000ft lower than prescribed in the flight check test document, and not checking the limit speeds as per the procedure requirement is good airmanship?

Quoting tdscanuck (Reply 43):
I defer to the Airbus drivers on this, but this implies that the aircraft has no nose-down elevator authority in the specified condition; I'm very intrigued how the regulators bought off on that.

Basically, the crew allowed the situation to be put so far off the edge beyond what certification could foresee...
1. Low speed flight check should have been done at FL140, to allow for recovery in case of screw ups. D-AXLA did it at 3,0000ft.
2. Low speed flight check required that the crew check the limit speeds for protection and warnings activations, this was not done, therefore they failed to notice that the aircraft FAC was generating limit speeds much lower than it should have been.
3. The crew failed to pick up on FMGC MCDU message "CHECK GW" which was displayed for about 30mins prior to the accident, and act upon it. (such message indicate difference from AoA calculated gross weight by the FAC differing more than 7 tons from the FMGC).

Where was Vaprot and Vamax, and where should they have been?
For a normal functioning A320, for their weight, Vamax should have been at 107kcas. This is calculated using the FACs, comparing AoA and gross weight. Vaprot should have kicked in at about 110-112kcas.
The stuck AoA resulted in erroneous Vaprot and Vamax calculated by FAC (plus that CHECK GW message generated).
When aircraft was at 140kcas, FAC displayed an erroneous 90kcas Vamax, and at the time of the stall warning it was 64kcas.
VMCA is 104kcas for any weights on CONF 3... this would have been another warning if one remembers "familiar numbers"... but that's a different story.
Hence, when the stall warning was generated, the speed was well below adequate margin, and even below Vamax for the given condition.

Where was the THS?
FDR data shows that at 110kcas THS was 9deg NU, and at 99kcas, it was 11.5deg NU. Well, it was going to be difficult to recover with 2.5deg extra NU THS position even with 14,000ft of air below you.

The Boeing equivalent is for an AoA vane to be locked in position on ice (due to an improper "rinsing" with no protection to air data sensors), approach a stall while continuing to retrim the aircraft towards full nose up, then get a stick shaker acting at a few knots above VMCA... (and be at 3000ft when it all happened).

As far as I know, certification doesn't cover upset recovery outside the certification envelope (to which this case is!)

Quoting tdscanuck (Reply 41):
If that does *not* mean that manual trim adjustment is necessary to stall recovery, then I'm extremely confused.

a. Manual trim adjustment provided the stall warning protection hasn't been tampered with (by incorrect human action, which in effect, it was in the case of D-AXLA), is not required. Otherwise the aircraft wouldn't be certified.
b. Manual trim adjustment provided one does the recovery procedure correctly (and "a" above doesn't happen beforehand), is not required. Otherwise the aircraft wouldn't be certified.

Quoting tdscanuck (Reply 41):
Exactly. And if you require manual trim to recover from inside the flight envelope, then it's not compliant with the FARs. If they're outside the flight envelope then I'm not really sure what the overall point is; there are zero guarantees of what the airplane will do any more than a little bit outside the flight envelope.

The AoA protection relies on the vanes. AOA1 and AOA2 were stuck, AOA3 was functioning. Therefore as the aircraft slowed down, the voting mechanism of the FBW system, rejected AOA3 data. The stall warning was generated (even under normal law) under a last resort stall protection mechanism, that is, when an AoA vane reaches 23deg in Normal Law (even if the ADR was rejected), will generate the warning. This 23deg, is always below Vs1g. Hence, the aircraft had gone outside the certification envelope.

Quoting tdscanuck (Reply 41):
The plane wasn't telling the crew that they had to reset the trim wheel to recover; it was telling them that *it* wouldn't reset the trim and, *if* the crew wanted to trim, they'd have to do it themselves. If trim were actually required to recover from a stall warning, it wouldn't be certifiable.

Correct. The aircraft effectively has been tampered with (by humans) incorrectly prior to the flight, therefore such things occur.

Quoting tommytoyz (Reply 42):
1. If the trim freezes full up in direct law - which it can, but not necessarily, and
2. If you add power as per SOP on stall warning at the time
3. Then, given these circumstances, manual trim MUST be adjust to recover from the stall, or you will not recover.
4. An Amber message on an A320 means - Action required. The message in this crash, which was ignored, was in amber, instructing them to adjust trim manually. It does not mean please monitor or be aware, etc...it means action is required.

Provided the aircraft and its airworthiness hadn't been tampered/violated with (as per D-AXLA)... aircraft under normal law would have the protections active, negating the need for manual trimming. Aircraft under alternate and direct laws, would have stall warnings activated with adequate margin. Once the airworthiness has been tampered with (intentionally or unintentionally, by human intervention), even test pilots might have second thoughts. The problem is addressing the "tampering".

One cannot argue "well it happened" without understanding the reasons why. The case of AeroPeru in Lima is also a case where effectively, the airworthiness of the aircraft had been tampered with... why treat D-AXLA differently?

In the case of AF447, no, one does not need manual trimming to perform a correct recovery. AF447 was a case where the crew did not want to recover because they did not know they had to recover from a stall.

Quoting tommytoyz (Reply 42):
Are you saying AB doesn't know how their aircraft will behave in a stalls? Or that they have no recovery procedures?

AB knows, and the recovery procedures has been mentioned numerous times in various topics related to AF447. However, the case of D-AXLA, the stall warning came at a speed lower than Vs1g, which is outside certification.

Quoting tommytoyz (Reply 42):
Stalling is well within any airliners "envelope". It will not fall apart, disintegrate or crash because of a stall.

Yes, provided the aircraft is airworthy, and the crew does not take reckless action ignoring required checks and ignoring maneuver guidelines (case of D-AXLA), and provided crew takes the correct recovery action (AF447, to which they did not).

Quoting tommytoyz (Reply 42):
It will only do that if the crew don't know how to recover from one and follow the proper established recovery procedure.

Yes, as is the case of AF447, and not D-AXLA.
---

Quoting tdscanuck (Reply 43):
You need to train to keep the aircraft in the envelope. There is a very small fudge factor because the OEM has to go slightly outside the envelope to make sure that the plane is OK at the boundaries but that doesn't help when you blow right past the boundary headed for 40degrees AOA.

Agree. This is why crew train to do checklists and follow QRH, so that their "superior skills" are not required to save the day. 40deg AOA, goes outside the realm of an "average airline pilot" as per certification requirement.

Quoting tdscanuck (Reply 43):
Agreed, although it's *extremely* difficult (though not impossible) to get outside the flight envelope without doing something wrong first.

Enough cases of this...

Quoting tdscanuck (Reply 43):
Yes, which is why there is a stall warning system and why you have to react to the stall warning system; not ignore it until you fully stall the airplane.

Yes, I wonder that Tommytoyz has to say with the cases of BEA BAe Trident at Staines, or that 727 that maintained pitch all the way throughout the stall and crashed...

Quoting tdscanuck (Reply 43):
And, in order to even need the recovery procedure at all, the crew has to screw up the avoidance procedure. Hence my original question: why would you train people to recover from a situation that you can only get into by ignoring your training?

I'm equally baffled!
---

Quoting tommytoyz (Reply 44):
And if the stall warning system fails, as in the Perpignan accident?

Why did it fail? That is the problem that should be addressed, not the "superior skills requirement to save the aircraft".
The first thing you do is to prevent the failure in systems required for the crew to maintain safe conduct of flight (ie: critical systems). In this case, the failure is caused by? Someone deciding to rinse the aircraft with high pressure hoses and not protect the AoA vanes as per manufacturer guidelines/common sense.

And just because the stall warning system failed, it doesn't mean one should forget performing the necessary checks to perform a maneuver requiring the safety net to be present at the correct positions...
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
Daysleeper
Posts: 565
Joined: Sun Dec 20, 2009 3:33 pm

RE: AF 447 - Sims Misleading?

Sun Apr 08, 2012 5:20 pm

Quoting tommytoyz (Reply 40):
Different people will draw different conclusions, I am sure. For me - better training in general and especially in stall recovery as well as avoidance, rather than just avoidance. And better training in general on basic airmanship, manual flying, flying manually in direct law, etc....

This doesn’t really answer what I asked, in order for the aircraft to be in a full stall and for a re-trim to be required to recover from it are you having to assume that there is a malfunction with the AoA sensor/s ?

In other words, in a fully functional aircraft is it even possible to get into this situation?
 
tommytoyz
Topic Author
Posts: 1195
Joined: Thu Jan 18, 2007 9:08 am

RE: AF 447 - Sims Misleading?

Sun Apr 08, 2012 8:59 pm

Quoting mandala499 (Reply 45):
Not good enough for me! I asked you:

Sorry that you just can't get it, that in the situation that the A320 crew was in, manual retrim was required. I've quoted, explained, etc....So if you choose to continue to argue the point, we'll just disagree and move on as there is no point in it for me or anyone else, IMHO.

Quoting mandala499 (Reply 45):
Question:
You talk about "airmanship", do you not think that performing Low Speed Flight Test at an altitude 11,000ft lower than prescribed in the flight check test document, and not checking the limit speeds as per the procedure requirement is good airmanship?

No it's not good airmanship. Another example of why that needs to be practiced more. Good point. Relying exclusively on AoA based systems and abdicating basic airmanship can be fatal.

Quoting mandala499 (Reply 45):
Once the airworthiness has been tampered with (intentionally or unintentionally, by human intervention), even test pilots might have second thoughts. The problem is addressing the "tampering".

That may be true, but malfunctions and the possibility of malfunctions can never be eliminated. To assume perfection is to assure death. The crew must then be able to deal with malfunctions, even if it's the other pilot. It should be trained as well as possible, IMHO.

Quoting mandala499 (Reply 45):

AB knows, and the recovery procedures has been mentioned numerous times in various topics related to AF447. However, the case of D-AXLA, the stall warning came at a speed lower than Vs1g, which is outside certification.

In AF447, stall recovery was not done properly and was not trained. That is why I maintain stall recovery should be trained along with manual flying in general. Maybe then AF447 crew would have been aware of their stall or even avoided it altogether and maybe D-AXLA would have followed correct procedure to avoid the second stall and adjusted the trim as required. They actually did recover from the 1st stall. What they didn't do is avoid the 2nd stall by ignoring manual trim.

Even by your "stall avoidance" philosophy, perhaps this crash shows more training is needed.

Quoting mandala499 (Reply 45):
why would you train people to recover from a situation that you can only get into by ignoring your training?

I'm equally baffled!

Did the AF447 captain, who got back to the cockpit as the plane was already stalled, do anything outside his training to get into the stall? No he did not. But he was as confused as the others anyway. That shows the level of their training, IMHO. Why you argue against recovery training, is what baffles me. It's basic airmanship.

Quoting mandala499 (Reply 45):
Quoting tommytoyz (Reply 44):
And if the stall warning system fails, as in the Perpignan accident?

Why did it fail? That is the problem that should be addressed, not the "superior skills requirement to save the aircraft".

To me, this kind of thinking is baffling. It does not address the problem in the eye. It does not take superior skills to recover from a stall. Every student pilot does stall recovery training - at least when I went through. It is a basic piloting skill. If we have gotten to the point were the airline industry considers stall recovery to be a "superior skill" - then IMHO, we are accepting sub par basic flying skills inside airliners.

Quoting Daysleeper (Reply 46):
This doesn’t really answer what I asked, in order for the aircraft to be in a full stall and for a re-trim to be required to recover from it are you having to assume that there is a malfunction with the AoA sensor/s ?

In other words, in a fully functional aircraft is it even possible to get into this situation?

I have no idea. I am not an A320 expert.

The necessity to trim the aeroplane manually can occur in a situation that
is already degraded, as was the case during the accident.
.....
It should also be noted that the technique for approach to stall does not remind crews of the
possible need to have recourse to the trim wheel in direct law

http://www.bea.aero/en/enquetes/perpignan/perpignan.php
Page 93 of the final report

[Edited 2012-04-08 14:21:50]
 
Pihero
Posts: 4239
Joined: Mon Jan 31, 2005 5:11 am

RE: AF 447 - Sims Misleading?

Sun Apr 08, 2012 11:29 pm

If, and it's a big "IF", we kept on the initial premises of the OP, this thread is just an impossible discussion between aviation engineers and pilots and someone whose agenda is difficult to understand.
The main problem revolves around some "stall recovery training " and AF is of course being accused of failing to properly train its pilots.
Problem is how .
1/- There is no simulator that can reproduce the airplane post-stall behaviour and any attempt to "simulate" a full stall is akin to believing in Mickey Mouse's sainthood. And the reports on how some hardy soul managed to get out of the situation AF447 crew found themselves in is absolute bullshit.
Someone says every private pilot knows how to get out of a stall. That's bull, the exercise is over as soon as the nose drops... the spin exit exercise we used to practice for has disappeared from most of the countries I know.
Any airline who'd claim that he / she could have done better than these pilots (of AF447 and D-AXLA ) is at the very least full of arrogance. Any non-professional could be excused ("My Lord, forgive them for they know not ..." )
............................................................................................................................................................................
Comments on AF447 :
Tom and Gerry insist on the fact that the crew never went into attempting a stall exit... because they did not know they were in one : They had no buffet, they had flight control authority in all axes and they weren't trusting their instruments ; at night and without any seat of the pants information as the descent was in a steady rate ( acceleration nil ) and they were past information overload.
............................................................................................................................................................................

2/- So the only way would be doing it for real... Well that implies first that the authorities would have approved such a scheme, the insurers to be reasonable with the extra danger premium they're bound to demand, the instructors had followed courses drawn by the OEM flight ops, and finally, just let's have a look at a fleet perpective.
Let's take AirFrance as they are in fact over the fire : some 4,800 pilots, all needing the training in order to regain their clients'trust ; let's take the recency at 2 years and let's define the training as low altitude (FL 150 and below   ) and high altitude (FL 350 and above)... taking all the airspace restrictions and the exercise preparation, let's put that training aat taking 2 hours. So every year, 2,400 pilots will use 4,800 hours of airplane... that's more than another 330 in the fleet.
Talk about expensive joy-riding !

Secondly, one has repeatedly talked about training for airmanship : Thirty one years of instructorship... and I'm still looking for it... so how could I train for it ? Does one train for tenderness, for tolerance or understanding ?... and does someone who does some gliding from time to time when the weather is unlimited wide blue know better than a test engineer, an aeronautical engineer on this site and the countless pilots - tests and training - who are spending days of research and meetings to formulate to-morrows airline training environment ?
I'm curious
As it happens, I completely in agreement with the likes of tdscanuck and Mandala499 on this subject.
Contrail designer
 
tommytoyz
Topic Author
Posts: 1195
Joined: Thu Jan 18, 2007 9:08 am

RE: AF 447 - Sims Misleading?

Mon Apr 09, 2012 5:18 am

Quoting Pihero (Reply 48):
If, and it's a big "IF", we kept on the initial premises of the OP, this thread is just an impossible discussion between aviation engineers and pilots and someone whose agenda is difficult to understand.
Quoting Pihero (Reply 48):
does someone who does some gliding from time to time when the weather is unlimited wide blue know better than a test engineer, an aeronautical engineer on this site and the countless pilots - tests and training - who are spending days of research and meetings to formulate to-morrows airline training environment ?
I'm curious

The facts are what count. My motivations are easily seen in my question in the OP, no more no less. I am not anti AB as you have claimed I was, etc...I don't understand why I can't ask a simple question here and discuss it, without the holier than thou attitude. Which is sad in light of the many errors said in that tone.

You and your friends have tried to impress here by rolling off of credentials before. If you guys would just admit to mistakes and accept facts as a normal person would, things wouldn't get so testy. IMHO. Just one quick example is falsely describing that manual retrim was not required in the D-AXLA crash, for instance, and there are many more where that came from:

Quoting tdscanuck (Reply 41):
And if you require manual trim to recover from inside the flight envelope, then it's not compliant with the FARs.
Quoting tdscanuck (Reply 41):
The plane wasn't telling the crew that they had to reset the trim wheel to recover; it was telling them that *it* wouldn't reset the trim and, *if* the crew wanted to trim, they'd have to do it themselves.

Instead you guys testily jump all over me for pointing them out, rather than making any corrections. That's not professional.

Quoting Pihero (Reply 48):
Problem is how .

Exactly. This is what is important and why I started the OP.

What I don't understand is to excuse the mistakes of the airmen in the D-AXLA crash because of the way the aircraft was washed.

The D-AXLA crash in particular shows that even stall avoidance procedures is not going to save you if you don't do it correctly. Why did those 3 pilots make the same mistake? Manual retrim would have been required to avoid stalling a second time in that crash, regardless of what your very knowledgeable professional friends insist to the contrary.

Both AF447 and D-XLA cases involve avoidable stalls, and it wasn't the plane's fault. The malfunctions experienced in both cases did not make stalls inevitable nor recovery impossible. So what's left? You tell me, you're the professional.

Quoting Pihero (Reply 48):
Tom and Gerry insist on the fact that the crew never went into attempting a stall exit... because they did not know they were in one

Certainly possible.

Quoting Pihero (Reply 48):
There is no simulator that can reproduce the airplane post-stall behaviour and any attempt to "simulate" a full stall is akin to believing in Mickey Mouse's sainthood. And the reports on how some hardy soul managed to get out of the situation AF447 crew found themselves in is absolute bullshit.

That is the question I asked in the OP. Can some level of fidelity be programed into simulators to train upset recovery with SIMS or not? Currently it seems not. But maybe in the future:

- Dr. Sunjoo Advani, president of International Development of Technology based in The Netherlands, is also chairman of the International Committee for Aviation Training in Extended Envelopes (Icatee).

The reason simulator aerodynamics don’t go beyond that point is because, he said, “manufacturers didn’t want to take responsibility,” and it was assumed that well designed flight controls would help properly trained pilots avoid stalls and prevent accidents. “Well, it just so happens that the accidents are occurring in that region,” he said.

Icatee is working on research that will supply ICAO (and thus the regulators in countries that are ICAO members) guidance on not only how UPRT could be delivered effectively but also on how simulators could be modified to teach real stall training. “We have a simulator standards document that will define the technology standards that will be used in future simulators.

“We’re not going to force all simulators to be able to spin upside down and to start centrifuging their pilots,” he said. “What we want to do is to create better scenarios in simulators that teach upset prevention and recovery training. We want to create a more rigorous training environment with the use of simulators. And in later phases of the project, what we expect from simulators is better buffet simulation and a representative model of the stall.”


The question then, if future simulators are able to simulate LOC conditions, should recovery techniques be trained on them?

Quoting Pihero (Reply 48):
Secondly, one has repeatedly talked about training for airmanship

Ability to proficiently fly manually with the side stick and no auto throttle, as opposed to just pushing buttons and twisting dials. Because when the plane hands you the plane without advanced notice, you better be proficient and able to fly it that way. That's what I mean by airmanship.

[Edited 2012-04-08 22:35:42]

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