Automation dependency stripped of political correctness.
In the A, once stalled, you could leave the stick alone and the auto will trim all the way to comfortably maintain the bird in a fully developed and pronounced stall.
Thread drift to an extent, but this is simply incorrect. Please take note of FDMII's well-considered posts and let's not mislead fellow professionals (and others) with stuff that's not based on fact!
CONF is correct.
OK465,
Bother, you got in first!
FDMII's analysis of AF447 seems to be error-free, but he doesn't mention that the Pitch-Alternate Law in operation (as opposed to Pitch-Direct, to which the FBW did not revert) is a C* law. That means the pilot's fore/aft movements of the sidestick are commands for changes in normal-acceleration (Nz) - not pitch. Because the PF continued to hold the stick aft of neutral for almost the whole sequence, the a/c eventually had full up-elevator in its attempt to deliver an (impossible) increase in Nz above 1g. Contrary to what donpizmeov writes, the autotrim kept trimming back until the THS reached full nose-up trim.
Having said that, the PF's apparent inattention to pitch - particularly during the departure from cruise alt and the unsustainable climb-sequence - would be unlikely in a pilot that had regularly practised flying the same a/c level at cruise altitude with the AP and FD (and preferably the ATHR) off.
Bother, you got in first!
FDMII's analysis of AF447 seems to be error-free, but he doesn't mention that the Pitch-Alternate Law in operation (as opposed to Pitch-Direct, to which the FBW did not revert) is a C* law. That means the pilot's fore/aft movements of the sidestick are commands for changes in normal-acceleration (Nz) - not pitch. Because the PF continued to hold the stick aft of neutral for almost the whole sequence, the a/c eventually had full up-elevator in its attempt to deliver an (impossible) increase in Nz above 1g. Contrary to what donpizmeov writes, the autotrim kept trimming back until the THS reached full nose-up trim.
Having said that, the PF's apparent inattention to pitch - particularly during the departure from cruise alt and the unsustainable climb-sequence - would be unlikely in a pilot that had regularly practised flying the same a/c level at cruise altitude with the AP and FD (and preferably the ATHR) off.
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ExV238, OK465, Chris Scott: yes, CONF iture's reference is being made to the movement of the THS as it follows-on the elevators' attempt to maintain the 1 G datum when the aircraft is not in Direct Law.
The opposite case also applies: with SS held fully-forward the THS would follow and return to normal cruise setting.
This thread diversion into what has been since 2009 and moreso since Perpignan and AirAsia a very complex series of arguments and important points, is valuable as it clarifies for many who may not have read the original AF447 threads and who are professional airmen, aircraft system behaviour in extremely rare circumstances, the point being, notwithstanding, automation has enhanced flight safety in the same way EGPWS, TCAS & ADS have. It is abundantly clear that automation is reliable to certification standards cited elsehwere in the thread, which, it is important to acknowledge, do not guarantee or contemplate 100% fault-free operation.
The opposite case also applies: with SS held fully-forward the THS would follow and return to normal cruise setting.
This thread diversion into what has been since 2009 and moreso since Perpignan and AirAsia a very complex series of arguments and important points, is valuable as it clarifies for many who may not have read the original AF447 threads and who are professional airmen, aircraft system behaviour in extremely rare circumstances, the point being, notwithstanding, automation has enhanced flight safety in the same way EGPWS, TCAS & ADS have. It is abundantly clear that automation is reliable to certification standards cited elsehwere in the thread, which, it is important to acknowledge, do not guarantee or contemplate 100% fault-free operation.
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Either way, if you hold the stick back you stay stalled. I'm glad you find the necessity to use both hands in the Boeing reassuring.
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Ladies & gentlemen: you are proving my point; the pilot was confused about the basics. In my days of simple Boeings you could ask any pilot a question about the systems & handling effects and get the same answer. Now it seems there is a variety of mis-understandings. So will some one answer my question and stop having a bar-room squabble about if it's apples or oranges.
This thread has now been alive for a month without a consensus.
This thread has now been alive for a month without a consensus.
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Like all complex professions such as ours there are a dozen ways to skin a cat and each has his or her favourite.
Only ego prevents us from learning from others.
Wrinkles and gray hair no longer imply wisdom they just confirm age. I know this for a fact.
With all this in mind:
I think when aviation captures one, one applies oneself naturally, to supplement training regardless of whether it is rudimentary or, more fortunately, from instructors who really do know their stuff and know how to teach while retaining an abiding respect for the professionalism of their candidates. Aviation is a lifetime of self-teaching.
Wherever aviation has, by circumstance, inattention, reduced motivation or perhaps health reasons, become merely a means to an end or worse, has become just a job, there is reduced safety.
Now, the risk here is in falling into the blame discourse but that is certainly not the intent in these comments.
However, many such circumstances in the ebb and flow of life are at least partly within one's ability to affect. Rarely is one not the locus of all action. An induced comfort through many years of ordinary operations has twin effects upon capacity and even competencies, which is the goal of solid simulator and recurrent training and checking.
The notion of "failure" has changed dramatically over the past 3 decades as has the need to repeat a simulator session. While not the most pleasant of occurrences, a failed ride is always first a learning opportunity and an experience with the potential for rescuing one in one of those moments aviation has in store.
What I hear from colleagues who are still active is that asking questions and being curious is seen as "geeky" and not cool. What a disappointment! If that's even partly the case that's a huge shift from the environment in which the guys now retiring were just cutting their teeth. An incessant curiosity is necessary as are questions and listening; - it's a shame that it's seems to be old-fashioned. Giving in to technology is still voluntary even as it may not be a conscious decision.
I'm not a confirmed believer in consensus thinking, particularly at this stage of the thread and, more generally, regarding automated aircraft. But there are some truths which are becoming self-evident and this thread has touched on some of them.
This is one of many ways of responding to your questions.
Last edited by FDMII; 1st Feb 2016 at 23:32.
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When does any Pilot LOOK to see what the THS is doing in normal cruising flight ?
The fact that is only, or largely, in one direction MAY not be noticed, if as in this case the Pilots were trying to get the aircraft to behave.
Perhaps a slight finger pressure on a SS should have had a compensating pressure from the ball of the PF's right hand.
BUT this was possibly something which he had never done much, at cruising level.
Some have suggested that there should be a limit to the AUTOMATIC adjustment of the THS to, say, FIVE units. Others may know better.
(PS My employers had to record the B707 trim readings when sending data to Boeing for performance monitoring. in the 1970s.)
LT
The fact that is only, or largely, in one direction MAY not be noticed, if as in this case the Pilots were trying to get the aircraft to behave.
Perhaps a slight finger pressure on a SS should have had a compensating pressure from the ball of the PF's right hand.
BUT this was possibly something which he had never done much, at cruising level.
Some have suggested that there should be a limit to the AUTOMATIC adjustment of the THS to, say, FIVE units. Others may know better.
(PS My employers had to record the B707 trim readings when sending data to Boeing for performance monitoring. in the 1970s.)
LT
As the company does not like us stalling the aircraft, I can only comment on what the simulator does.
As the speed decreases into VLS, the speed brakes, if deployed, auto retract, and prior to Alpha Stall Warning, the auto trim stops. To continue speed decay, you need to hold pressure on the side stick to prevent the nose dropping. If the stick is released, the nose drops and speed increases.
To check and make sure the THS was not at the stop, I put the SIM into direct law, and trimed up. Was able to trim an extra 4+ units to what was shown on the flight control SD page for Stall. This was in the 380 sim. Tried the 330 SIM next door, same result. There is no trim wheel in the 380, only two rocker type switches.
As the speed decreases into VLS, the speed brakes, if deployed, auto retract, and prior to Alpha Stall Warning, the auto trim stops. To continue speed decay, you need to hold pressure on the side stick to prevent the nose dropping. If the stick is released, the nose drops and speed increases.
To check and make sure the THS was not at the stop, I put the SIM into direct law, and trimed up. Was able to trim an extra 4+ units to what was shown on the flight control SD page for Stall. This was in the 380 sim. Tried the 330 SIM next door, same result. There is no trim wheel in the 380, only two rocker type switches.
Hi donpizmeov, quote (my emphasis):
"As the company does not like us stalling the aircraft, I can only comment on what the simulator does.
As the speed decreases into VLS, the speed brakes, if deployed, auto retract, and prior to Alpha Stall Warning, the auto trim stops."
I presume this was in Pitch-Alternate law? If you are responding to my post, I was recalling the THS behaviour on AF447. If your A330 sim is representative, and in Pitch-Alternate, I can only suggest the system characteristics may have been modified since 2009. Perhaps others can comment?
"As the company does not like us stalling the aircraft, I can only comment on what the simulator does.
As the speed decreases into VLS, the speed brakes, if deployed, auto retract, and prior to Alpha Stall Warning, the auto trim stops."
I presume this was in Pitch-Alternate law? If you are responding to my post, I was recalling the THS behaviour on AF447. If your A330 sim is representative, and in Pitch-Alternate, I can only suggest the system characteristics may have been modified since 2009. Perhaps others can comment?
I think the major point from both accidents is being lost in the technical argument.
The major point is "Fly the Aircraft" Its very nice to know the various control law logic of the Airbus FBW system, just as it is with modern Boeings. However, when the Sh*t hits the fan, fly the plane. If you sit with full back stick in, you're in trouble! In any aircraft, not just modern ones. If you don't know what the biggest control surface on the aircraft is doing then, again, you're in trouble! All this is very easy to say sat behind a computer on a bright sunny day however.
As for fully automated aircraft, show me a computer that can think on its feet in rapidly changing and dynamic situations. A computer that can control multiple failures, passenger problems, ATC issues, weather, failures of unmonitored systems (e.g. tailpipe fire, galley fires). When you can show me that, I will gladly hand in my licence. I will also never step foot on an aircraft again.
Is automation dependancy an issue? Yes, it most certainly is. However, more training is required, not to get rid of the pilots all together.
I will leave you with one final thought. Could we ever design a computer to match the performance of Sullenberger and his crew? I don't mean the landing itself, but could we design a computer that would weigh up all the odds and then make that decision to land in the Hudson? A decision the undoubtedly saved the lives of all 155 people on board that aircraft. My answer would be probably, one day. But not in my lifetime, and probably not for many lifetimes to come.
The major point is "Fly the Aircraft" Its very nice to know the various control law logic of the Airbus FBW system, just as it is with modern Boeings. However, when the Sh*t hits the fan, fly the plane. If you sit with full back stick in, you're in trouble! In any aircraft, not just modern ones. If you don't know what the biggest control surface on the aircraft is doing then, again, you're in trouble! All this is very easy to say sat behind a computer on a bright sunny day however.
As for fully automated aircraft, show me a computer that can think on its feet in rapidly changing and dynamic situations. A computer that can control multiple failures, passenger problems, ATC issues, weather, failures of unmonitored systems (e.g. tailpipe fire, galley fires). When you can show me that, I will gladly hand in my licence. I will also never step foot on an aircraft again.
Is automation dependancy an issue? Yes, it most certainly is. However, more training is required, not to get rid of the pilots all together.
I will leave you with one final thought. Could we ever design a computer to match the performance of Sullenberger and his crew? I don't mean the landing itself, but could we design a computer that would weigh up all the odds and then make that decision to land in the Hudson? A decision the undoubtedly saved the lives of all 155 people on board that aircraft. My answer would be probably, one day. But not in my lifetime, and probably not for many lifetimes to come.
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I will leave you with one final thought. Could we ever design a computer to match the performance of Sullenberger and his crew? I don't mean the landing itself, but could we design a computer that would weigh up all the odds and then make that decision to land in the Hudson? A decision the undoubtedly saved the lives of all 155 people on board that aircraft. My answer would be probably, one day. But not in my lifetime, and probably not for many lifetimes to come.
The other thing to think about is that the "not in my lifetime" argument is not very clever.
I know a lady who is 101 years old.
Imagine what anybody's answer to future tech questions would have been when she was 20?
The pace of technological change is accelerating, not linear.
We went from dope and cloth to Concorde/Space Shuttle in half a lifetime.
Guesses are just that/
Quote from Jonty:
"I think the major point from both accidents is being lost in the technical argument."
Not by me:
"Having said that, the PF's apparent inattention to pitch - particularly during the departure from cruise alt and the unsustainable climb-sequence - would be unlikely in a pilot that had regularly practised flying the same a/c level at cruise altitude with the AP and FD (and preferably the ATHR) off."
Quote from Tourist:
"If you had made the tiny effort to read previous posts/links etc you would have found that we have all the required capabilities in aircraft already."
Well, fancy that! And presumably you have the links at your fingertips? So, unless you want to alienate newcomers who have too much of a life to wade through 250-plus posts (a high proportion of which you wrote), perhaps you would be so kind as to provide the ones relevant to your latest put-down?
"I think the major point from both accidents is being lost in the technical argument."
Not by me:
"Having said that, the PF's apparent inattention to pitch - particularly during the departure from cruise alt and the unsustainable climb-sequence - would be unlikely in a pilot that had regularly practised flying the same a/c level at cruise altitude with the AP and FD (and preferably the ATHR) off."
Quote from Tourist:
"If you had made the tiny effort to read previous posts/links etc you would have found that we have all the required capabilities in aircraft already."
Well, fancy that! And presumably you have the links at your fingertips? So, unless you want to alienate newcomers who have too much of a life to wade through 250-plus posts (a high proportion of which you wrote), perhaps you would be so kind as to provide the ones relevant to your latest put-down?
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As you point out, I have indeed made more than my fair share of the posts. Perhaps others who want to contribute could make a similar effort to research before posting?
Last edited by Tourist; 2nd Feb 2016 at 14:24. Reason: Recovered my good mood.
Yes, Tourist, I've only got about half-way so far, but it's evident that you've been a tour-de-force. Admirable, although your hard work is no doubt encouraged by your pursuit of an interesting agenda; one that is not, however, instantly popular in a forum for professional pilots.
Unfortunately, you cannot expect everyone else to apply themselves with comparable enthusiasm. And remember: right or wrong you are the heretic here, and therefore the burden of proof lies with you; even if that involves boring and patient repetition of your arguments, and the evidence that you use to support them.
Most readers coming to this thread could be forgiven for assuming that the main subject under discussion will be the effects of CURRENT automation on the handling and management skills of the existing pilot force, and how they might be mitigated right now.
Your advocacy of the fully-autonomous airliner at some time in the near or more-distant future is no doubt worthy of a thread all of its own.
Chris
Unfortunately, you cannot expect everyone else to apply themselves with comparable enthusiasm. And remember: right or wrong you are the heretic here, and therefore the burden of proof lies with you; even if that involves boring and patient repetition of your arguments, and the evidence that you use to support them.
Most readers coming to this thread could be forgiven for assuming that the main subject under discussion will be the effects of CURRENT automation on the handling and management skills of the existing pilot force, and how they might be mitigated right now.
Your advocacy of the fully-autonomous airliner at some time in the near or more-distant future is no doubt worthy of a thread all of its own.
Chris
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donpizmeov, Tourist, Chris Scott
There is no stall in normal law and in alternate law there is no alpha prot or alpha Max but only Vsw. So in alternate law the speed brakes don't go in automatically. Also in alternate 2 if aircraft is pitched with insufficient thrust even with stick neutral aircraft will keep trimming back to maintain 1G till it stalls. If SS is kept full back it can drive THS to full.
In these accidents the starting point is unnecessary, extreme and bizarre application of flight control in longitudinal axis. If pilots had the knowledge that at those altitudes in alternate law full back stick is fatal they needn't have to know much more about laws.
There is no stall in normal law and in alternate law there is no alpha prot or alpha Max but only Vsw. So in alternate law the speed brakes don't go in automatically. Also in alternate 2 if aircraft is pitched with insufficient thrust even with stick neutral aircraft will keep trimming back to maintain 1G till it stalls. If SS is kept full back it can drive THS to full.
In these accidents the starting point is unnecessary, extreme and bizarre application of flight control in longitudinal axis. If pilots had the knowledge that at those altitudes in alternate law full back stick is fatal they needn't have to know much more about laws.
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villas
All this discussion of Airbus flight controls entirely misses the point.
If you hold the controls fully back in a Boeing and indeed almost any other aircraft, you will stall. If you keep them fully back you will stay stalled. This is also true in an Airbus in direct law.
The fact that an Airbus sometimes/usually saves you from yourself and when in direct law does not is hardly an indictment of the entire system.
The starting point of these accidents is pilot incompetence not flight control laws. The reasons for the pilot incompetence are a bigger question, however the aircraft would not have crashed if the pilots had just done nothing.
All this discussion of Airbus flight controls entirely misses the point.
If you hold the controls fully back in a Boeing and indeed almost any other aircraft, you will stall. If you keep them fully back you will stay stalled. This is also true in an Airbus in direct law.
The fact that an Airbus sometimes/usually saves you from yourself and when in direct law does not is hardly an indictment of the entire system.
The starting point of these accidents is pilot incompetence not flight control laws. The reasons for the pilot incompetence are a bigger question, however the aircraft would not have crashed if the pilots had just done nothing.
Villas,
Stall warning comes from angle of attack, not airspeed. This is why it still works with unreliable airspeed. Your V sw is really alpha SW.
The spoilers do auto retract, and the THS does stop trimming. Been on the BUS since 2003, it's always been the same. The THS trim stops and makes you have to apply pressure on the stick to maintain attitude to warn you of the low speed. If you keep pulling on the stick you then hear Stall Stall. If you Release the pressure, the attitude lowers and you accelerate. Hmmm...Think this was done on purpose? Have you ever wondered why stowing the speed brake comes so far down the stall recovery items?
I have never flown a mini bus, perhaps they behave a little differently.
Stall warning comes from angle of attack, not airspeed. This is why it still works with unreliable airspeed. Your V sw is really alpha SW.
The spoilers do auto retract, and the THS does stop trimming. Been on the BUS since 2003, it's always been the same. The THS trim stops and makes you have to apply pressure on the stick to maintain attitude to warn you of the low speed. If you keep pulling on the stick you then hear Stall Stall. If you Release the pressure, the attitude lowers and you accelerate. Hmmm...Think this was done on purpose? Have you ever wondered why stowing the speed brake comes so far down the stall recovery items?
I have never flown a mini bus, perhaps they behave a little differently.
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Tourist I have been in agreement with you all along and changes to flight control laws because of blunders of pilots is like throwing the baby out with bath water.
donpizmeov
I am aware that not only Vsw in alternate law but Valpha prot and Valpha Max also are AOA from ADRs averaged and shown as speed. However when in Alt2 when low speed stability is lost as in case of two ADR fail the pitch down will not occur. But when it is available it happens as quoted below from A330 manual. In Alternate law Speed brakes won't retract in A320.
LOW SPEED STABILITY
At low speed, a nose down demand is introduced in reference to IAS, instead of angle of attack, and alternate law changes to direct law
donpizmeov
I am aware that not only Vsw in alternate law but Valpha prot and Valpha Max also are AOA from ADRs averaged and shown as speed. However when in Alt2 when low speed stability is lost as in case of two ADR fail the pitch down will not occur. But when it is available it happens as quoted below from A330 manual. In Alternate law Speed brakes won't retract in A320.
LOW SPEED STABILITY
At low speed, a nose down demand is introduced in reference to IAS, instead of angle of attack, and alternate law changes to direct law