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Old 30th Mar 2012, 07:11   #1081 (permalink)
 
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Thanks, Old Carthusian, fully concur.

Quote:
For example, Colgan overrode his stick pusher! Maybe what is needed is not more force, but something that is harder to ignore.
Seemingly the stall warnings in both Colgan and AF447 cases were not ignored but the reactions to them were terminally wrong. We are not necessarily looking at perception but rather cognition malfunction.

Quote:
Is this knowledge well known among crews in general?
It is. trick is knowing it so well it could be remembered easily at 4 am.
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Old 30th Mar 2012, 07:39   #1082 (permalink)
 
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Hi Clandestino,

Quote:
Whose FCTM is this?
A320%20321%20FCTM%20Flight%20Crew%20Training%20Manual.pdf OP-020. P 15/16 FCTM 08 JUL 08

It appears to Airbus themselves who made the statement.
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Old 30th Mar 2012, 07:53   #1083 (permalink)
 
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JAR 25

Quote:
Selected Items, Part 25—airworthiness standards: Transport category airplanes
Granted the A330 was not certified initially under US guidelines, but I thought it interesting to see how well it met US standards. As the title says, this is selected information by me.
The A330 was certificated to JAR 25 Change 13, which should have been virtually identical to FAR 25 as written at that time (1980s?) I'm not sure how the FAR 25 you quote (2012?) relates to that earlier standard.

Anyway, the differences seem to be: [The emphasis and selections are mine]

Quote:
JAR 25.181 Dynamic stability

contains another requirement....

(b) Any combined lateral-directional oscillations (Dutch roll) occurring between stalling speed and maximum allowable speed appropriate to the configuration of the aeroplane must be positively damped with controls free, and must be controllable with normal use of the primary controls without requiring exceptional pilot skill
Maybe marginal, but the A330 seems to meet this requirement also

Quote:
JAR 25. 201 Stall demonstration has the following

(c) The following procedures must be used to show compliance with JAR 25.203
.....
(2) As soon as the aeroplane is stalled, recover by normal recovery techniques
Quote:
JAR 25.205 Stall warning

(b) The warning may be furnished ......

.....

(c) ...... Stall warning must continue throughout the demonstration, until the angle of attack is reduced to approximately that at which stall warning is initiated.
Since the demonstration is supposed to be ended as soon as the aeroplane is stalled the designers would not have been expected to maintain the warning throughout 54 seconds of stall. With hindsight this requirement should be up for review.

PS. On checking, the current CS25 has removed the reference to the demonstration, which fits the bill:

Quote:
Once initiated, stall warning must continue until the angle of attack is reduced to approximately that at which stall warning began.

Last edited by Owain Glyndwr; 30th Mar 2012 at 09:26. Reason: additional comment
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Old 30th Mar 2012, 08:14   #1084 (permalink)
 
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Quote:
Originally Posted by Machinbird
#2 Buffeting apparently was not a strong and effective deterrent to the crew of AF447 and the Captain back in the cabin apparently did not recognize it either.
The AF447 pilots probably mistook it for an indication of overspeed. At high altitude there isn't any appreciable difference between high-speed and low-speed buffet as both are caused by the same aerodynamic phenomenon (an oscillatory interaction between local shock waves and airflow separation).

The certification pilots probably considered the buffeting to be "a strong and effective deterrent to further speed reduction". BEA says as much in a note on page 54 of IR#2: "The stall manifests itself particularly through vibrations." (I take it that "vibrations" is franglais for "buffet").

In the video of a TV emission that was posted a little while ago on the other thread, the AB Chief Test Pilot also seems to talk about "deterrent buffet" (at 34:50), but my understanding of spoken french is not good enough to understand what he says. Maybe one of our french contributors could help?

Last edited by HazelNuts39; 30th Mar 2012 at 09:18. Reason: link to video and time 34:50 added
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Old 30th Mar 2012, 08:57   #1085 (permalink)
 
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Quote:
It appears to Airbus themselves who made the statement.
What you posted is First Choice Airways Flight training manual.

It is possible "Airbus themselves" made the statement, which was then copypasted into the FTM, yet it is equally possible someone at FCA was the source of the (mis)statement.

While I think Airbus pilots have to be trained to deal with unusual attitudes and approach to stall recovery in laws other than normal, this has no bearing on AF447 accident. Failure to recover did not result from lack of skills but inability to understand what is going on and consequently apply the correct procedure.
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Old 30th Mar 2012, 11:08   #1086 (permalink)
 
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Hi Clandestino,

Thanks for the decode of FCA. I only noticed the Airbus logo on the top of the page, however my airline's FCTM has exactly the same words so I conclude they are Airbus recommendations.

Quote:
Failure to recover did not result from lack of skills but inability to understand what is going on and consequently apply the correct procedure.
I agree.

On previous type conversion courses, we stalled the simulator to the nose drop and then recovered. When we had stopped using the manual pitch trim, the elevator feel was incredibly heavy, buffet could be mistaken for turbulence, controls became sloppy. It was impossible to prevent the nose dropping below the horizon using elevator control alone.

I've never stalled the A320 sim. I've flown at Alpha max & seen TOGA Lock, and heard "Stall Stall" briefly. etc.

The AF447 crew presumably had never been exposed to a full stall in the sim and hence they failed to recognise the symptoms.
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Old 30th Mar 2012, 14:07   #1087 (permalink)
 
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Hi

@ rudderrudderrat & Clandestino, re:
Quote:
The effectiveness of fly-by-wire architecture, and the existence of control laws, eliminate the need for upset recovery maneuvers to be trained on protected Airbus aircraft.
(my bold)
In Alternate (or Direct) law, an A320 (or other FBW Airbus) is no more a protected aircraft.

I admit this is a bit far fetched... and would prefer this sentence to be removed or, at last, better explained.

AFAIK, no such sentence is in the A330/A340 FCTMs
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Old 30th Mar 2012, 14:12   #1088 (permalink)
 
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Is there a consensus yet as to the altitude needed to effect a recovery by a typical crew (ie not the optimum with hindsight type of recovery), say from the dynamics AF447 had at 30k ft ? I believe the law they were in retained over-g protection but with no visible horizon or AoA meter would recovery rely on watching speed and pitching up to the stall warner when flying again ?
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Old 30th Mar 2012, 14:40   #1089 (permalink)
 
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Quote:
Originally Posted by Clandestino
Quote:Machinbird
For example, Colgan overrode his stick pusher! Maybe what is needed is not more force, but something that is harder to ignore.

Seemingly the stall warnings in both Colgan and AF447 cases were not ignored but the reactions to them were terminally wrong. We are not necessarily looking at perception but rather cognition malfunction.
As I recall, the Colgan crew had just been discussing tail stall which may have primed them for their wrong reactions.

When you are the one flying and something grabs your stick, it is a natural human tendency to fight back. What we need is something that leads us to the correct action.(Even at 4:00 AM )

Does anyone have any thoughts along that line? Perhaps a Sim routine combined with a standardized stall warning device that creates an almost Pavlovian response.

I say almost Pavlovian, because I remember the Abidjan A-310 accident where dropping the nose in the face of a false stall warning on takeoff caused an accident. Obviously the stall warning reaction has to be tempered with some common sense.

Last edited by Machinbird; 30th Mar 2012 at 14:54.
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Old 30th Mar 2012, 14:51   #1090 (permalink)
 
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Quote:
Originally Posted by Mr. Optimistic
Is there a consensus yet as to the altitude needed to effect a recovery by a typical crew (ie not the optimum with hindsight type of recovery), say from the dynamics AF447 had at 30k ft ? I believe the law they were in retained over-g protection but with no visible horizon or AoA meter would recovery rely on watching speed and pitching up to the stall warner when flying again ?
Before the hamster wheel started turning, it was becoming clear that the actual pull out of the resulting dive would create less altitude loss than the recovery from the stall.

It seems that the Basic Fighter Maneuvering (BFM) turn strategy was relevant to the pullout altitude loss.
From Hazelnuts last cut at the problem, it seems that the pullout could benefit still more from a little more power during the recovery to level flight. Maximum structural g was not being reached (probably due to induced drag at the higher AOA recovery).
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Old 30th Mar 2012, 16:25   #1091 (permalink)
 
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Quote:
It seems that the Basic Fighter Maneuvering (BFM) turn strategy was relevant to the pullout altitude loss.
Quote:
...it seems that the pullout could benefit still more from a little more power during the recovery to level flight.
Mach:

I'd be real careful with advocating this.

You're not looking for a sustained QTT (quickest tightest turn) here.

Just something approaching a minimum radius maneuver. Turn rate is irrelevant.
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Old 30th Mar 2012, 16:52   #1092 (permalink)
 
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Quote:
Originally Posted by OK465
Turn rate is irrelevant.

I'd be real careful with advocating this.
Thanks for the caution OK465.
In that turn rate is pointing your velocity vector away from the down direction, it isn't irrelevant.

I'm actually interested in identifying some generic simple to use guidelines that pilots could use. Obviously you will not want to be adding power above your cornering velocity, but the concept of adding power while having your nose pointed down to improve your pull out is a bit counter-intuitive to most pilots.

It looks like cornering velocity for a particular aircraft might be a good thing to know. No one plans on having to recover from a dive, so no one seems to be teaching it.

I am not advocating anything but a look to see if we could do a better job in performing dive recovery should the need arise. How/when/what to teach would raise a host of other issues that would probably be premature to discuss.
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Old 30th Mar 2012, 16:54   #1093 (permalink)
 
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Man machine interface (Pavlov approach)

Hi,

Machinbird:

For example:

A "vibrating (modulated, AM and FM)" pilots seat special cushion (integrated or stand alone as a retrofit).



PS

Differentiating CLEARLY low speed and overmach by "sophisticated (and reliable) "multiple input parameters data processing".

Something like "seat of the pants" Mk II
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Old 30th Mar 2012, 17:03   #1094 (permalink)
 
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Thanks. I recall Hazelnut's post and the relatively limited loss of altitude (well to my non-pilot eyes) anyway. A really interesting recent post mentioned 20k feet(thanks Dozy great post !) perhaps based on sim. Figured there must have been other attempts so wondered what the consensus was and what the best strategy is. knowing how much nu can be attempted when time is really pressing doesn't look that obvious when in an unusual attitude.
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Old 30th Mar 2012, 17:31   #1095 (permalink)
 
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Quote:
Originally Posted by Machinbird
I'm actually interested in identifying some generic simple to use guidelines that pilots could use.
It depends. When you have plenty of altitude you would play it safe to avoid secondary stalls.

When the ground is approaching fast, my strategy as a non-pilot engineer would be (I've been shot down earlier mentioning this): Push the sidestick fully forward until the stall warning stops. Then immediately SS to neutral, slowly start pulling, carefully increasing the pull force until stall warning is encountered, then immediately SS to neutral until stall warning stops, then start pulling again, etc.

For the reasons you mentioned I wouldn't add power.

P.S.
Depending on how fast autotrim moves the THS, manual trim should be considered.

Last edited by HazelNuts39; 30th Mar 2012 at 17:55. Reason: P.S.
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Old 30th Mar 2012, 19:33   #1096 (permalink)
 
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Quote:
Originally Posted by HazelNuts39 View Post
Depending on how fast autotrim moves the THS, manual trim should be considered.
In the A320 sim it was actually relatively speedy. You could probably physically move the wheel faster manually, but I suspect the servos moving the THS would take roughly the same amount of time in any case.
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Old 30th Mar 2012, 19:54   #1097 (permalink)
 
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Hazelnut, will potential recovery options be part of the accident investigation and reported eventually ?
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Old 30th Mar 2012, 21:31   #1098 (permalink)
 
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Quote:
Originally Posted by Mr Optimistic
will potential recovery options be part of the accident investigation and reported eventually ?
No, I don't expect that will be the case. We are engaging in an academic discussion that is only remotely relevant to AF447 whose pilots apparently never realized they were in a stalled situation.

The first priority is and should remain staying out of a stall. In that spirit BEA has made a number of recommendations, for example "that EASA and the FAA evaluate the relevance of requiring the presence of an angle of attack indicator directly accessible to pilots on board airplanes."
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Old 30th Mar 2012, 22:24   #1099 (permalink)
 
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To further this academic discussion I would venture this in general...

(edit: in response to the use of the esoteric term 'corner velocity' )

IIRC 'Va' for a 330 varies from around 320k at around 28,000 down to around 260 at sea level. This encompasses quite a wide range of TAS, all 'limited' to 2.5 g.

From a practical standpoint, I'm not sure how likely it is that anyone who put themselves, or was put into a dive situation would be able to deftly modulate thrust to maintain a speed (let alone mental concentration on it), whose value was varying nearly as rapidly as the requirement to modulate the T-levers, on the way down.

Dive recoveries have been taught in every heavy I checked out in. The recovery procedures are recommended by the manufacturer and worked fine in all the aircraft I'm familiar with.

In this same vein, as CONF says, the manufacturer established stall procedures that involve extending the slats (Flaps 1) below 20,000 if clean. Were one to have a chance to practice this, one might see the decidedly positive benefits of following the manufacturer's guidance.

One first has to recognize that the guidance is applicable.

Last edited by OK465; 30th Mar 2012 at 22:58.
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Old 30th Mar 2012, 22:48   #1100 (permalink)
 
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Quote:
Originally Posted by OK465 View Post
IIRC 'Va' for a 330 varies from around 320k at around 28,000 down to around 260 at sea level. This encompasses quite a wide range of TAS, all 'limited' to 2.5 g.
That G limitation only applies in Normal Law however. Once you're in Alternate, roll is direct and the calculations can no longer be applied to limit the maneouvre.

@HN39

While you're right that preventing a stall in the first place must remain a priority, I believe that Airbus and Boeing collaborated on providing proper stall recovery training for airliner crews. What bothers me about the AoA indicator is that while it would certainly be a help in a situation where the pilot knows how to use it, we're dealing with a situation here where at least one pilot was unable to use the basic panel to diagnose and recover from a stall.
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