Airbus crash/training flight
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You got that right. If they hit TOGA or what ever Airbus calls it, the game is over because you can't overide the pitchup with the underslung engines until they get pitch control.
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The aim was not to comment on 'avoiding the stall' nor on how to avoid 'roll reversal' (ie do not use aileron!) but merely an observation on what appeared to be a 'doubting' observation about a known aerodynamic fact that using aileron to pick up a fully stalled wing can put you on your back extremely quickly
- aileron on a fully stalled wing ALWAYS produces 'roll reversal' - I remain unconvinced that this lesson is correctly taught or understood - and I agree with Mountain Bear that introducing yet another magic computer programme loop to overcome this is fraught with even more danger.
The 'solution' to our problems lies in flying ability and less reliance on computers to get us out of the mess we have got ourselves into.
EDIT: Before I am jumped on by the theorists, could all please assume the word 'conventional' where 'wings' are mentioned?
showed possible roll reversal
The 'solution' to our problems lies in flying ability and less reliance on computers to get us out of the mess we have got ourselves into.
EDIT: Before I am jumped on by the theorists, could all please assume the word 'conventional' where 'wings' are mentioned?
Last edited by BOAC; 26th Oct 2010 at 07:40.
stall
Hi BOAC.
at the point of stall, or dependent on other factors at a point consistent with approach speed/1.3... the controls should not exhibit any abnormal responses. AoA can be achieved through 360 degrees... ( my rotor blades achieve various AoA's within 0.π to 2.π.... per rev dependent on radial velocity Ω, radius, r/R and translational speed of the rotor system in the airmass, ie inboard section of the span achieves 11/12.π at ψ=180) but the normal regime for a transport is around 0.π to π/12, a very limited sector of operations. From π/2 to 3/2.π the flow is full reversal. As far as adverse aileron roll is concerned there are boundaries of operation where the coefficient of lift v AoA, or "a" slope doesn't decrease with increasing AoA above stall. Equally, drag does not act in a linear manner at extreme AoA's either.
At an α>15 ( π/12) approx to α<30 ( π/6), ie a normal high α > Vs 1g stall α, then it is quite normal to get some control reversal due to the change of the a slope. Discounting the roll spoiler action, the change of section α for the L and R aileron acting differentially needs to be exceeded by the reduced a slope on the section with the downward deflected aileron. This can be avoided by good design of the section and the differential deflections.
With respect to adverse aileron yaw, it is rather moot with a mixed aileron/spoiler roll control, where the spoiler drag exceeds the drag of the aileron pretty much at any α from 0.π to 2.π, ie within a 360 degree rotation of a section.
The A320 accident merely shows a period of behavior within the certified envelope area where there may be some reversal occurring, which is of interest, particularly as an A-PC issue will undoubtedly be held over the pilots head.
To simplify the above, in an aerodynamic stall of a B737 or a B747, the ailerons remain effective at and around the point of break, with normal response, and no exceptional piloting skills needed. The B747 particularly is very nice. Don't do this at home The A320 on the other hand was never tested in this region and the behavior is interesting to this observer, who has examined A-PC issues with this type before. The MD11 ailerons work nicely through stall as well, (but a stall at other than low speed/1.0g will often result in severe damage to the elevators, including delamination of the skins and fracture of the elevator spar... again, don't do this at home...) Having said all the above, which probably amounts to little, the certification process of RPT aircraft is remarkably thorough, but on occasions events conspire to show room for improvement. I would think that the out of trim case for the AI aircraft, and some TBC products still could be improved as we pilots do get to occasionally operate in odd parts of the envelope.
(Probably the greatest control reversal event in recent times was a B737-400, of Adam Air KI 574, which well exceeded the design envelope of the aircraft, and achieved recorded data of roll in the opposite direction of the ailerons/spoilers due to aeroelastic deformation... then it broke up... being operated well beyond the design limits of the aircraft. Shades of Quill & DeHavilland etc...).
Stuff Happens, and the pilot has seconds to deal with it, whereas scientists have years to study it... Unfortunate turn of events led to the event occurring, but the recovery part hardly was a failure of the crew, perhaps I would feel differently if the aerodynamic package for the sims incorporated what we know about dynamics outside of the certified envelope, but at this time the majority of sims are of questionable value outside of the normal envelope, and on occasions negative training (MD11 sim, full aerodynamic stall, ROC 6000FPM for 2 minutes...., B737 stall with full rudder deflection, wings recovered by aileron... B777/B744 50knot Xwind full wrong aileron, wings level to rotate...).
(π= PI, btw.... )
FDR
PS: the problem here from a handling point is the out of trim situation, a bit of "rock and roll" would assist in stopping the attitude from getting higher still due to the out of trim condition.... roll is of interest from a certification point but is far less concern than the out of trim case, or the fact that the failure of AoA probes was not identified and annunciated as a failure to the crew when this condition occurred.
at the point of stall, or dependent on other factors at a point consistent with approach speed/1.3... the controls should not exhibit any abnormal responses. AoA can be achieved through 360 degrees... ( my rotor blades achieve various AoA's within 0.π to 2.π.... per rev dependent on radial velocity Ω, radius, r/R and translational speed of the rotor system in the airmass, ie inboard section of the span achieves 11/12.π at ψ=180) but the normal regime for a transport is around 0.π to π/12, a very limited sector of operations. From π/2 to 3/2.π the flow is full reversal. As far as adverse aileron roll is concerned there are boundaries of operation where the coefficient of lift v AoA, or "a" slope doesn't decrease with increasing AoA above stall. Equally, drag does not act in a linear manner at extreme AoA's either.
At an α>15 ( π/12) approx to α<30 ( π/6), ie a normal high α > Vs 1g stall α, then it is quite normal to get some control reversal due to the change of the a slope. Discounting the roll spoiler action, the change of section α for the L and R aileron acting differentially needs to be exceeded by the reduced a slope on the section with the downward deflected aileron. This can be avoided by good design of the section and the differential deflections.
With respect to adverse aileron yaw, it is rather moot with a mixed aileron/spoiler roll control, where the spoiler drag exceeds the drag of the aileron pretty much at any α from 0.π to 2.π, ie within a 360 degree rotation of a section.
The A320 accident merely shows a period of behavior within the certified envelope area where there may be some reversal occurring, which is of interest, particularly as an A-PC issue will undoubtedly be held over the pilots head.
To simplify the above, in an aerodynamic stall of a B737 or a B747, the ailerons remain effective at and around the point of break, with normal response, and no exceptional piloting skills needed. The B747 particularly is very nice. Don't do this at home The A320 on the other hand was never tested in this region and the behavior is interesting to this observer, who has examined A-PC issues with this type before. The MD11 ailerons work nicely through stall as well, (but a stall at other than low speed/1.0g will often result in severe damage to the elevators, including delamination of the skins and fracture of the elevator spar... again, don't do this at home...) Having said all the above, which probably amounts to little, the certification process of RPT aircraft is remarkably thorough, but on occasions events conspire to show room for improvement. I would think that the out of trim case for the AI aircraft, and some TBC products still could be improved as we pilots do get to occasionally operate in odd parts of the envelope.
(Probably the greatest control reversal event in recent times was a B737-400, of Adam Air KI 574, which well exceeded the design envelope of the aircraft, and achieved recorded data of roll in the opposite direction of the ailerons/spoilers due to aeroelastic deformation... then it broke up... being operated well beyond the design limits of the aircraft. Shades of Quill & DeHavilland etc...).
Stuff Happens, and the pilot has seconds to deal with it, whereas scientists have years to study it... Unfortunate turn of events led to the event occurring, but the recovery part hardly was a failure of the crew, perhaps I would feel differently if the aerodynamic package for the sims incorporated what we know about dynamics outside of the certified envelope, but at this time the majority of sims are of questionable value outside of the normal envelope, and on occasions negative training (MD11 sim, full aerodynamic stall, ROC 6000FPM for 2 minutes...., B737 stall with full rudder deflection, wings recovered by aileron... B777/B744 50knot Xwind full wrong aileron, wings level to rotate...).
(π= PI, btw.... )
FDR
PS: the problem here from a handling point is the out of trim situation, a bit of "rock and roll" would assist in stopping the attitude from getting higher still due to the out of trim condition.... roll is of interest from a certification point but is far less concern than the out of trim case, or the fact that the failure of AoA probes was not identified and annunciated as a failure to the crew when this condition occurred.
Last edited by fdr; 26th Oct 2010 at 09:37.
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then it is quite normal to get some control reversal due to the change of the a slope
The airbus was nowhere near 'the point of the stall' nor was it 'within the certified envelope are' nor 'around the point of break'.
yup, but:
“the roll occurring between the stall and the completion of the recovery may not exceed approximately 20 degrees” for level wing stalls. In level wing stalls the bank angle may exceed 20 degrees occasionally, provided that lateral control is effective during recovery.
just playing devils advocate....
this was a wings level entry... it as an approach to stall event.... and it did get to a stall (oops) and the roll exceeded 20 degrees on various occasions in both directions, not completely due to the pilots roll and yaw inputs....
anyway...
“the roll occurring between the stall and the completion of the recovery may not exceed approximately 20 degrees” for level wing stalls. In level wing stalls the bank angle may exceed 20 degrees occasionally, provided that lateral control is effective during recovery.
just playing devils advocate....
this was a wings level entry... it as an approach to stall event.... and it did get to a stall (oops) and the roll exceeded 20 degrees on various occasions in both directions, not completely due to the pilots roll and yaw inputs....
anyway...
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No, what the crew did didn't work. What was suggested might have worked, if they had tried it.
The BEA clearly considers that current stall training may be at fault:
"recovery should be possible by first not overusing thrust"
They used TOGA"and using elevator and stab trim to get the nose down again."
and they didn't touch the trim either.The BEA clearly considers that current stall training may be at fault:
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.
exercises and techniques relating to approach-to-stall to ensure
control of the aeroplane in the pitch axis.
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Hi,
But as reminder .. the word of AI (in the past 
)
"Specific training on upsets is not necessary"
Among the recommendations of BEA ago this: that the AESA, in cooperation with manufacturers, the evolve do training exercises and procedures relating to technical approach of dropping to ensure control of the airplane in pitch.
)"Specific training on upsets is not necessary"
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jcj - I am not familiar with that quote, but if it is in fact from the 'software junkie' factory it merely amplifies my call for a return to emphasis on basic flying skills and less reliance on automation to save us. If true, a terrifying indictment of the state of mind there.
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Stall characteristics
Originally Posted by fdr
this was a wings level entry... it as an approach to stall event.... and it did get to a stall (oops) and the roll exceeded 20 degrees
- As soon as the aeroplane is stalled, recover by normal recovery techniques. (25.201(c)(3))
and with -
- The aeroplane trimmed for straight flight at a speed selected by the applicant, but not less than 1.13 VSR and not greater than 1.3 VSR. (25.103(b)(6))
regards,
HN39
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Hi,
That's not the first time that FBW and automation are questioned and it will be not the last .....
John T. Halliday: Air France 447: A Cockpit China Syndrome
and less reliance on automation to save us
John T. Halliday: Air France 447: A Cockpit China Syndrome
"Training can not and should not be a fix for a lousy design." -- Drs. Kathy Mosier and Linda Skitka
"I have documented hundreds of aerospace software failure cases. There are serious risks in reliance on software in safety-critical applications. A innocuous addition to software could have disastrous effects not discovered in testing. Never trust anyone who says such failures can never happen." -- Computer scientist Peter Neuman
It seems to me that everyone has become baffled by bulldust and lost sight of the basics. The FACTS are that this crew decided to fly a large jet transport at a relatively low altitude and slow speed. This poor decision was compounded by the pilot flying trimming for a very slow speed. Now, call me a bluff old traditionalist, but could these FACTS just possibly be why the aforementioned large jet transport subsequently crashed.....
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Flying at this low airspeed to test their computerized airplane would have probably worked fine at that low altitude but somebody let TOGA take over and put it out of control for the trim setting they had. Boeings I flew never had that problem. You could actually use airmanship to salvage the stall situation. I chose to not ever fly an airbus for this reason. Less money at our airline but better chance of retiring. I retired 7 years ago. Go Boeing!
p51, it wasn’t TOGA (thrust) which was at the root of the handling problem, it was trim.
Thud brings us back to the reality of the accident; it wasn’t the system or the pilot trimming / failing to trim, it was the crew’s understanding of the system / situation which contributed to the accident. This aggravated the poor planning / understanding of what was being attempted.
These issues are not solved by ‘more manual’ flight – basic flying skills. Crews need higher order thinking skills, some of which can be developed and exercised with appropriate manual flight; others require knowledge, application, and preparation – thinking ahead.
Automation might relieve muscular skills and workload, but it is not an excuse to stop thinking.
“Its not pilots hands which get them into trouble, it’s their heads.” (J. Reason)
Thud brings us back to the reality of the accident; it wasn’t the system or the pilot trimming / failing to trim, it was the crew’s understanding of the system / situation which contributed to the accident. This aggravated the poor planning / understanding of what was being attempted.
These issues are not solved by ‘more manual’ flight – basic flying skills. Crews need higher order thinking skills, some of which can be developed and exercised with appropriate manual flight; others require knowledge, application, and preparation – thinking ahead.
Automation might relieve muscular skills and workload, but it is not an excuse to stop thinking.
“Its not pilots hands which get them into trouble, it’s their heads.” (J. Reason)
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“Its not pilots hands which get them into trouble, it’s their heads.” (J. Reason)
You have a computer system, which can only done what it is programmed to do.
You have a pilot, who can only fly as well as human capacities allow.
You have the interface between the two.
What's the name of that movie..ah yes, "There Will Be Blood." Sooner or later. It's unavoidable.
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Hi,
You can think how much you want (and even be Capt Einstein) if the third pilot (the computer) counteract (for any reasons) your thoughtful actions you'll always lose
Indeed .. basic flying skill can't help ....
Automation might relieve muscular skills and workload, but it is not an excuse to stop thinking.
“Its not pilots hands which get them into trouble, it’s their heads.” (J. Reason)
“Its not pilots hands which get them into trouble, it’s their heads.” (J. Reason)
Indeed .. basic flying skill can't help ....
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jcjeant
A big element of truth here. Might well be what happened to AF447.
But on the Perpignan A320, if the crew had been mentally prepared for such wild behavior, I think they could have survived.
Unfortunately, in the context of present Airbus crew training, the phrase "unusual attitude" is supposed to be an oxymoron.
You can think how much you want (and even be Capt Einstein) if the third pilot (the computer) counteract (for any reasons) your thoughtful actions you'll always lose
Indeed .. basic flying skill can't help ....
Indeed .. basic flying skill can't help ....
But on the Perpignan A320, if the crew had been mentally prepared for such wild behavior, I think they could have survived.
Unfortunately, in the context of present Airbus crew training, the phrase "unusual attitude" is supposed to be an oxymoron.
Thnank you PEI for understanding what I was trying to say. Essentially, I was refering to the old adage about a superior pilot using his superior judgement to avoid having to demonstrate his superior skill. P51guy would you deliberately stall (or even fly very slow) a large swept wing jet transport of any type low down? If so, why? It proves nothing (except just how dangerous it is). The truly great Captain Robert Buck said it so much more eloquently than I ever could. While being checked out on the (I think) Constellation by an FAA Check Airman, he was downwind on a blustery day with one engine out when the FAA guy pulled back the power on another engine. Buck knew that things were now getting unnecesarily dangerous, and that being so close to the ground the safety margins were being eroded. He brought the power on the 2nd 'failed' engine back up. When the FAA guy said "you have to do this, it's part of the check" Buck replied "well, looks like I've failed. Let's go home." Buck WAS a Captain. (Incidentally, as he was at the time one of TWA's senior pilots the FAA guy backed down, and they did something else!)
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Thrust, trim control attitude, airmanship, lack of airmanship, recognizing the failures etc.
All valid points, but it comes to knowing what they were doing and what to expect, if they had ONLY calculated the minimum speed for the conditions of the test like the Airbus Test Pilots do and NEVER go below it, they would have never needed any of that.
They were not prepared and more important, they were not familiar with the test and how to avoid trouble if the test was not successful.
G
All valid points, but it comes to knowing what they were doing and what to expect, if they had ONLY calculated the minimum speed for the conditions of the test like the Airbus Test Pilots do and NEVER go below it, they would have never needed any of that.
They were not prepared and more important, they were not familiar with the test and how to avoid trouble if the test was not successful.
G