Habsheim
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Originally Posted by RRR - extract from FCOM
However, the angle-of-attack will not exceed αMAX, even if the pilot gently pulls the sidestick all the way back.
- the airplane will rapidly reach alpha max
- temporary excursions over alpha max may happen, and so without stalling or crashing
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Originally Posted by HN39
Yes, with a pilot who knows his airplane inside and out and how to best demonstrate its capabilities.
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when I pull the sidestick following a GPWS warning, my simulator is also rapidly to alpha max
In the investigation of the Hudson ditching, the NTSB accepted Airbus' explanation of the phugoid damping. In the Habsheim accident the airplane was decelerating more rapidly and the pitch attitude increasing more rapidly than in the Hudson ditching. The effectivity of the phugoid damping was convincingly demonstrated in the A340 level-bust incident.
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Hi HazelNuts39,
The behaviour of Alpha Max protection demonstrated in the video around time 10:50 shows an AoA of between 16° (me) to 17° (CONF iture) which is very close to the theoretical Alpha Max attempted to be demonstrated at Habsheim.
The complex system behaviour is described in FCOM in just one short paragraph, so I'm not surprised we interpret what it is trying to say differently.
You and I must be reading this differently:
The complex system behaviour is described in FCOM in just one short paragraph, so I'm not surprised we interpret what it is trying to say differently.
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Originally Posted by RudderRudderErrat
The complex system behaviour is described in FCOM in just one short paragraph, so I'm not surprised we interpret what it is trying to say differently.
other exemple Airbus doesn't stall
Last edited by roulishollandais; 6th Jan 2014 at 10:45. Reason: bbcode
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Originally Posted by RRR
The complex system behaviour is described in FCOM in just one short paragraph, so I'm not surprised we interpret what it is trying to say differently.
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Originally Posted by HN39
Would you be decelerating with increasing pitch attitude when you pull the sidestick?
Whatever the weight, configuration, and circumstances ... Airbus has one single procedure to be applied : PULL UP TOGA
Did any of them refused to deliver alpha max ? Not that I can remember.
Did any of them was under severe deceleration or pitch attitude increase ? To be honest I could not tell but I would be glad to experiment and report if only I had free access to a simulator.
In the investigation of the Hudson ditching, the NTSB accepted Airbus' explanation of the phugoid damping. In the Habsheim accident the airplane was decelerating more rapidly and the pitch attitude increasing more rapidly than in the Hudson ditching. The effectivity of the phugoid damping was convincingly demonstrated in the A340 level-bust incident.
Why not ?
But where has been the BEA on it ?
Why the NTSB or the investigators from Spain can detail how the elevators can refuse the pilot's orders, but the BEA is mute ... ?
What strikes me is how in Habsheim, New-York or Bilbao, the pitch authority has been compromised by features built into the system, whenever the aerodynamic had still more to deliver.
Originally Posted by CONFiture
Any scenario is possible.
Methinks it was Einstein who observed that thought experiments are always successful.
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C'ture… surely at Habsheim there was no speed to trade for height? And no power to allow a climb… The option to fly a Pugachev Cobra over the trees was not available.
Could a pair of A320 test pilots have wrestled it closer to stalling, missing the trees, if handed the accident aircraft without its fly by wire protections five seconds away from the tree line? I'm skeptical. How many tries would typically be required in a simulator to miss the obstacle once full power was requested?
The hardware and software seemed to have done a fairly good job of giving the crew the chance to save the day from a bad position.
Did the throttle refuse to comply with their demands? I'm not convinced. The conspiracy-inclined documentaries I've seen seem to be a bit light on discussions of sound travel time and speed reconstruction from the video frames. I've seen no reason to doubt the official report.
Did the elevators refuse to allow them to pitch up into a stall? I would contend that the answer is yes… as designed.
I think a fairer question is whether the fly-by-wire 320 and its competitor are been lost in accidents at a different rate. A320s are at about 24:10,000, while 737NGs are at about 9:3500. It's about equal, although A320s have rather longer in service to compare. FBW is clearly doing no great harm across the spectrum.
Could a pair of A320 test pilots have wrestled it closer to stalling, missing the trees, if handed the accident aircraft without its fly by wire protections five seconds away from the tree line? I'm skeptical. How many tries would typically be required in a simulator to miss the obstacle once full power was requested?
The hardware and software seemed to have done a fairly good job of giving the crew the chance to save the day from a bad position.
Did the throttle refuse to comply with their demands? I'm not convinced. The conspiracy-inclined documentaries I've seen seem to be a bit light on discussions of sound travel time and speed reconstruction from the video frames. I've seen no reason to doubt the official report.
Did the elevators refuse to allow them to pitch up into a stall? I would contend that the answer is yes… as designed.
I think a fairer question is whether the fly-by-wire 320 and its competitor are been lost in accidents at a different rate. A320s are at about 24:10,000, while 737NGs are at about 9:3500. It's about equal, although A320s have rather longer in service to compare. FBW is clearly doing no great harm across the spectrum.
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You don't know that - you're just assuming it based on this theory you've made from whole cloth based on your interpretation of Alpha Max as 17.5 degrees dead, when in the real world the laws of physics will cause variance.
Thread Starter
Having returned from three days' absence, and now catching up, I've got brief questions for a couple of you guys:
Confit,
1) You didn't pick up on my query of your alpha-max figure for Flaps/Config FULL (15 deg). Where did you find that? Why 2.5 deg lower than Flaps 3, and why would the alpha-max be only 0.5 deg above alpha-floor (14.5 deg) in the Flaps FULL case, instead of the apparent 2.5 deg margin with Flaps 3 (17.5 deg and 15 deg respectively)?
Remember, this was an A320-100 in 1988.
2) By the way, what config do you think was set in the Gordon Corps video?
rudrudrat,
What is the source of info for your assertion that the stall test for certification was done in Pitch Alternate Law?
Confit,
1) You didn't pick up on my query of your alpha-max figure for Flaps/Config FULL (15 deg). Where did you find that? Why 2.5 deg lower than Flaps 3, and why would the alpha-max be only 0.5 deg above alpha-floor (14.5 deg) in the Flaps FULL case, instead of the apparent 2.5 deg margin with Flaps 3 (17.5 deg and 15 deg respectively)?
Remember, this was an A320-100 in 1988.
2) By the way, what config do you think was set in the Gordon Corps video?
rudrudrat,
What is the source of info for your assertion that the stall test for certification was done in Pitch Alternate Law?
Last edited by Chris Scott; 6th Jan 2014 at 21:50. Reason: Question expanded
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Originally Posted by Chris Scott
You didn't pick up on my query of your alpha-max figure for Flaps/Config FULL (15 deg).
Also valid for your second question.
Why 2.5 deg lower than Flaps 3, and why would the alpha-max be only 0.5 deg above alpha-floor (14.5 deg) in the Flaps FULL case, instead of the apparent 2.5 deg margin with Flaps 3 (17.5 deg and 15 deg respectively)?
My guess would be that, as CONF FULL is the normal configuration for landing, Airbus was not too excited to allow 17.5 deg of AoA that close from the ground with a higher risk for catastrophic tail strike ...
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One question for OK465 maybe, as you seem to give some simulator training.
What is the capacity for a modern flight simulator to register a variety of data such as the AoA, attitude, flight command inputs, flight control movements ... something similar to a FDR or QAR ?
What is the capacity for a modern flight simulator to register a variety of data such as the AoA, attitude, flight command inputs, flight control movements ... something similar to a FDR or QAR ?
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Why 2.5 deg lower than Flaps 3, and why would the alpha-max be only 0.5 deg above alpha-floor (14.5 deg) in the Flaps FULL case, instead of the apparent 2.5 deg margin with Flaps 3 (17.5 deg and 15 deg respectively)?
Then, there's higher slat deflection for Conf Full, which should increase the stall AoA, but maybe the flaps effect offsets the slat effect?
Last edited by C_Star; 7th Jan 2014 at 07:36.
Thread Starter
Quote from me, addressed to CONF_iture:
You didn't pick up on my query of your alpha-max figure for Flaps/Config FULL (15 deg). Where did you find that?
CONF_iture's reply:
Actually I did here.
No: you didn't! Your post merely restates the figures. Please state a specific reference for the Flaps FULL figure, if you have one.
Quote from C_Star:
I seem to remember from aerodynamics classes that higher flap settings yield lower critical AoA (but of course higher CL values) - that could explain why Conf Full has lower alphamax than Conf3.
Then, there's higher slat deflection for Conf Full, which should increase the stall AoA, but maybe the flaps effect offsets the slat effect?
That seems to be born out to some extent by the figures of alpha-floor in my BCAL/BA Tech Manual of 17FEB1988, which I quoted in a previous post four days ago:
"Alpha-floor is activated when:
- alpha > alpha-floor (9.5 deg in conf 0; 15 deg in conf 1, 2, 3; 14.5 deg in conf FULL, or [...]"
But, as you see, the difference is only half a degree. Confit's figure suggests:
(1) the difference is 2.5 deg;
(2) alpha-max with Flaps FULL was only 0.5 deg above alpha-floor, which also seems improbable.
Unlike the Airbus FCOM extracts I quoted in the same post, those figures from the BCAL/BA Technical Manual (Ch 09 Section 10) - 17FEB1988 revision - were still current at the A320's entry into service in April 1988, so may be the most reliable information available (so far) for the Habsheim a/c. They appear at the foot of the familiar curve of Cz-versus-alpha.
The equivalent page on the preceding version, dated 25AUG1987, is a duplicate of the Airbus FCOM Flight Controls chapter (1.09.10 P8, REV 03, SEQ 001) that I also quoted in that post. As you can see, there are no specific values of alpha for alpha-floor or the other two protection levels. The figures provided define each of the 3 protection levels simply as the alphas associated with factors of Vs in any weight/configuration at low Mach, but neglect to define Vs itself. It may be that, with certification still pending, the definition of Vs was still under discussion. (The A320 was type-certificated in February 1988.)
You didn't pick up on my query of your alpha-max figure for Flaps/Config FULL (15 deg). Where did you find that?
CONF_iture's reply:
Actually I did here.
No: you didn't! Your post merely restates the figures. Please state a specific reference for the Flaps FULL figure, if you have one.
Quote from C_Star:
I seem to remember from aerodynamics classes that higher flap settings yield lower critical AoA (but of course higher CL values) - that could explain why Conf Full has lower alphamax than Conf3.
Then, there's higher slat deflection for Conf Full, which should increase the stall AoA, but maybe the flaps effect offsets the slat effect?
That seems to be born out to some extent by the figures of alpha-floor in my BCAL/BA Tech Manual of 17FEB1988, which I quoted in a previous post four days ago:
"Alpha-floor is activated when:
- alpha > alpha-floor (9.5 deg in conf 0; 15 deg in conf 1, 2, 3; 14.5 deg in conf FULL, or [...]"
But, as you see, the difference is only half a degree. Confit's figure suggests:
(1) the difference is 2.5 deg;
(2) alpha-max with Flaps FULL was only 0.5 deg above alpha-floor, which also seems improbable.
Unlike the Airbus FCOM extracts I quoted in the same post, those figures from the BCAL/BA Technical Manual (Ch 09 Section 10) - 17FEB1988 revision - were still current at the A320's entry into service in April 1988, so may be the most reliable information available (so far) for the Habsheim a/c. They appear at the foot of the familiar curve of Cz-versus-alpha.
The equivalent page on the preceding version, dated 25AUG1987, is a duplicate of the Airbus FCOM Flight Controls chapter (1.09.10 P8, REV 03, SEQ 001) that I also quoted in that post. As you can see, there are no specific values of alpha for alpha-floor or the other two protection levels. The figures provided define each of the 3 protection levels simply as the alphas associated with factors of Vs in any weight/configuration at low Mach, but neglect to define Vs itself. It may be that, with certification still pending, the definition of Vs was still under discussion. (The A320 was type-certificated in February 1988.)
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Originally Posted by Chris Scott
No: you didn't! Your post merely restates the figures. Please state a specific reference for the Flaps FULL figure, if you have one.
"We're close to 15 deg AoA which is the maximum for this configuration"
I take it as a specific reference, why should I doubt such statement from a guy who seems pretty aware on what's going on ... ?