TAM A320 crash at Congonhas, Brazil
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Oops, another non-believer.
Tyro, I understand you might be a bit aged to read the real meaing of my posts, but I said exactly what you said: On any Airbus, you KEEP! your hand on the T/L.
btw cookoos clock's are made in black forest, not in Switzerland. Another myth going down in fumes, isn't it? Hunter58 btw lives in Airbus City, that's also not in Switzerland.
Dani
Tyro, I understand you might be a bit aged to read the real meaing of my posts, but I said exactly what you said: On any Airbus, you KEEP! your hand on the T/L.
btw cookoos clock's are made in black forest, not in Switzerland. Another myth going down in fumes, isn't it? Hunter58 btw lives in Airbus City, that's also not in Switzerland.
Dani
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HotDog, where are you coming from? Inspite of your 18 000 hours, you don't know a lot outside of your own airlines.
I know quite a lot of airlines where the PF flies the aircraft, but after touchdown, he orders "Revers", which means PM (PNF for older folks) regulates the reversers.
This is been done in older aircraft where it was not so easy to keep a steady revers thrust, and where you could overboost or stall a reversed engine.
Dani
I know quite a lot of airlines where the PF flies the aircraft, but after touchdown, he orders "Revers", which means PM (PNF for older folks) regulates the reversers.
This is been done in older aircraft where it was not so easy to keep a steady revers thrust, and where you could overboost or stall a reversed engine.
Dani
The Reverend
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Dani, well it is true that in my 33 year of aviation I only worked for two companies. In both of them, PF handles reverse thrust after touchdown. This was Convair 880, B707, Lockheed L1011 and B747 SOP. Apart from that, you yourself operate the reversers in your bus. So I would still like to see the SOPs that say otherwise. Have you ever landed a 747 at Kai Tak in typhoon conditions with max crosswind? Good chance to have finished up in the harbour by handing over the thrust levers to the PNF.
Per Ardua ad Astraeus
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Before this thread spirals downwards into yet another pit of slanging/abuse, be advised that different companies have different SOPs. Some do, indeed, call for PNF to operate REVERSERS, some PF. Please can we stop bickering?
NB We do NOT know the TAM SOP
NB We do NOT know the TAM SOP
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Originally Posted by Dani
Quote:
At what stage of a landing would the PF remove his hand from the TLs?
Never!
At what stage of a landing would the PF remove his hand from the TLs?
Never!
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Originally Posted by TyroPicard
just to clarify some of the more ludicrous recent postings from the land of the cuckoo clock
Originally Posted by Dani
btw cookoos clock's are made in black forest, not in Switzerland
The crowing rooster on the Zytglogge on the main street of the Swiss capital city of Berne predates Black Forest clocks by some 240 years.
PBL
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Al Zimer,
Indeed, when the PF exclaims "Look this!" (18:48:33) right pedal inputs are "huge" (24ş), indicating he was looking out to the runway, he knew he had no ground spoilers (18:48:29), so what did he feel (with his right hand?) that made him exclaim "Look this"? I believe it was another "bad news", on top of the "spoiler nothing" call, and related to the TLs.
IMHO, when you don't know WHY something is happening (hell is breaking loose), you don't point to the probable cause and exclaim "Look this!!".
Indeed, when the PF exclaims "Look this!" (18:48:33) right pedal inputs are "huge" (24ş), indicating he was looking out to the runway, he knew he had no ground spoilers (18:48:29), so what did he feel (with his right hand?) that made him exclaim "Look this"? I believe it was another "bad news", on top of the "spoiler nothing" call, and related to the TLs.
IMHO, when you don't know WHY something is happening (hell is breaking loose), you don't point to the probable cause and exclaim "Look this!!".
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Rob21 asks
The little green man sitting on the quadrant with his toe in the right thrust lever. Cousin of the guy who was playing with matches in the CWT of TWA800. 
PBL
Originally Posted by Rob21
so what did he feel (with his right hand?) that made him exclaim "Look this"
PBL
Last edited by PBL; 31st Aug 2007 at 07:10. Reason: Added a smiley to make it clearer that I was trying to be funny. Oh, well.
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bsieker and PBL both make very cogent arguments, which are well thought out. However I fully understand flat state space, "hierarchical decomposition", and the careful ordering of complex functions, modes and states into organized meaningful and useful sets. I also understand the difference between Raskin's ideal and the practical design needs of a human interface into complex systems. I'm not actually trying to argue in favor of a pure Raskin single mode approach across all systems. However I am trying to argue in favor of a single mode Raskin type design approach where primary flight controls and speed controls are concerned and I'll explain why.
Think about habits, think about how the mind narrows in an emergency, and think about how emergency controls are designed.
Regarding habits, they live somewhere else in the mind other than the conscious mind. We've all heard the expression "it's like riding a bicycle, you never forget". Once you know how to ride a bicycle or drive a car, you no longer have to think about how the controls work, you just know by habit. We've all experienced the situation where we've performed some task so long that we no longer think about how to perform it, and then when someone asks us how we perform the task, we have to watch ourselves do the task before we can explain the "how" to the person who asked. This is because the knowledge of how to do the task no longer lives in our conscious mind. I live in an urban area where it's a good idea to always lock your car, and I'm forever wondering if I've locked the car after I get out and walk away from it. The reason I wonder is because the act of locking the car does not pass through my conscious mind, I do it automatically out of habit, without thinking about it. Thus I don't remember if I did it or not.
Regarding how the mind narrows in an emergency, I explained this in my previous post that as fear rises, the mind moves more toward action oriented "fight or flight" type responses and away from thinking and reasoning type responses. In fear or an emergency, the mind tends to want to act rather than think and reason things out.
Regarding how emergency controls are designed, this is something all of us understand I believe. Why are fire extinguishers painted red? Why are they designed so that you only have to pull a pin and squeeze the handle to operate it? Why in a data center, is there a big red power button next to door, with a simple obvious sign that says "power off"? In an electrically fed fire in a data center, you want to cut the power as you're escaping, and this design makes this easy. Why are engine fire handles designed the way they are in a cockpit? Why are airliner door emergency handles designed the way they are? All are designed to accommodate the mind in an emergency, a mind that wants to act on an emergency instead of reasoning about it.
Now to primary flight controls. The primary controls change the attitude and direction of the aircraft and they speed it up or slow it down. Obviously these controls become emergency controls in an emergency. In an emergency, for the most part these are the controls the pilots will use when they act to try and resolve the emergency. Generally speaking, these controls (yoke or stick, brakes and rudder pedals, spoilers, throttles) in my opinion must be designed to accommodate the pilot's mind in an emergency, when he will tend to act on rather than reason out the emergency.
Bsieker stated the following:
He is very correct in what he says, especially when he says "I do not see at all why this would not be habituating." Whether FLX, TOGA or CLB, I would argue these are the more habituated positions of the thrust levers, since they spend most of their time there during operation of the aircraft. However this means that the mode or state of the throttle lever position DOES NOT equal engine power, is also the more habituated mode (or state), since again this is where most of the operating time is spent.
I'm running out of time this morning so I have to cut this short.
I would argue that it's very possible the pilot would NOT have left the ENG2 TL in the climb detent when ENG1 TL was pulled back, if this position were not the more habituated position for the TLs in the A320. In an all moving throttle lever system, I think it far less likely that an engine would have been left at such a high power setting at touchdown, especially since the auto thrust in such a system wouldn't have left the trottle at such a high power setting in the first place.
I think it substantially assists the pilot to have an unbroken habituated understanding below his conscious mind, that TL position ALWAYS equal engine power. I think this could have prevented leaving the ENG2 TL at a high power setting in the first place, and would have helped the pilot acting in an emergency to know (subconsciously know) to pull an advanced throttle lever back.
I noticed in the FDR data that during the rollout, the pilots disarmed and rearmed the spoilers, hoping the cycling would cause the spoilers to deploy. How wonderful a manual spoiler deploy lever would have been in those moments, but this emergency control was simply not there. AB crew know they have to become essentially system analysts when they learn to fly the AB (and to be fair Boeing pilots do as well). However who can be a fully functioning systems analyst and a diagnostic technician in a difficult landing situation and in an emergency?
Thus I'll close with this statement. A Raskin type single mode approach to HM design of primary flight controls and speed controls, that become emergency controls in an emergency, is a very good idea.
The other major airframe maker managed to create a single mode throttle system, in the sense that throttle position always equals engine power, and was not inhibited by the complexity of the system and flat state space constraints from doing so.
Someone said that cruise control on more recent cars do not move the gas pedal. True enough, but I would think the equivalent mode to the AB throttle system would be to press the gas pedal down about 3/4 full, then engage the cruise control, then the gas pedal would be left there while the cruise control remained engaged. Later when the cruise control was disengaged, the gas pedal would still be at 3/4 full. In the Boeing, the "gas pedal" would also be left where is was at when A/THR was disengaged, but at least you'd know where the engine power was before, and it wouldn't change after disengagement.
Please understand, I'm not trying to make a B vs AB argument, I'm making design choice arguments and using B and AB systems to illustrate.
I gotta go.
Think about habits, think about how the mind narrows in an emergency, and think about how emergency controls are designed.
Regarding habits, they live somewhere else in the mind other than the conscious mind. We've all heard the expression "it's like riding a bicycle, you never forget". Once you know how to ride a bicycle or drive a car, you no longer have to think about how the controls work, you just know by habit. We've all experienced the situation where we've performed some task so long that we no longer think about how to perform it, and then when someone asks us how we perform the task, we have to watch ourselves do the task before we can explain the "how" to the person who asked. This is because the knowledge of how to do the task no longer lives in our conscious mind. I live in an urban area where it's a good idea to always lock your car, and I'm forever wondering if I've locked the car after I get out and walk away from it. The reason I wonder is because the act of locking the car does not pass through my conscious mind, I do it automatically out of habit, without thinking about it. Thus I don't remember if I did it or not.
Regarding how the mind narrows in an emergency, I explained this in my previous post that as fear rises, the mind moves more toward action oriented "fight or flight" type responses and away from thinking and reasoning type responses. In fear or an emergency, the mind tends to want to act rather than think and reason things out.
Regarding how emergency controls are designed, this is something all of us understand I believe. Why are fire extinguishers painted red? Why are they designed so that you only have to pull a pin and squeeze the handle to operate it? Why in a data center, is there a big red power button next to door, with a simple obvious sign that says "power off"? In an electrically fed fire in a data center, you want to cut the power as you're escaping, and this design makes this easy. Why are engine fire handles designed the way they are in a cockpit? Why are airliner door emergency handles designed the way they are? All are designed to accommodate the mind in an emergency, a mind that wants to act on an emergency instead of reasoning about it.
Now to primary flight controls. The primary controls change the attitude and direction of the aircraft and they speed it up or slow it down. Obviously these controls become emergency controls in an emergency. In an emergency, for the most part these are the controls the pilots will use when they act to try and resolve the emergency. Generally speaking, these controls (yoke or stick, brakes and rudder pedals, spoilers, throttles) in my opinion must be designed to accommodate the pilot's mind in an emergency, when he will tend to act on rather than reason out the emergency.
Bsieker stated the following:
As to the workings of the thrust levers: it is really terribly simple, and a confusion very unlikely:
In a normal flighth you really only need three positions. This flight was no different:
- FLX/MCT (or possibly TOGA in certain conditions) from takeoff to thrust reduction. This gives flexible (or maximum) take-off power and arms autothrust.
- CL throughout the entire flight from thrust reduction to flare. This activates autothrust, previously armed by setting (flexible or maximum) takeoff power.
- IDLE during flare.
During rollout you additionally may use REVERSE IDLE and MAX REVERSE.
I do not see at all why this would not be habituating.
In a normal flighth you really only need three positions. This flight was no different:
- FLX/MCT (or possibly TOGA in certain conditions) from takeoff to thrust reduction. This gives flexible (or maximum) take-off power and arms autothrust.
- CL throughout the entire flight from thrust reduction to flare. This activates autothrust, previously armed by setting (flexible or maximum) takeoff power.
- IDLE during flare.
During rollout you additionally may use REVERSE IDLE and MAX REVERSE.
I do not see at all why this would not be habituating.
I'm running out of time this morning so I have to cut this short.
I would argue that it's very possible the pilot would NOT have left the ENG2 TL in the climb detent when ENG1 TL was pulled back, if this position were not the more habituated position for the TLs in the A320. In an all moving throttle lever system, I think it far less likely that an engine would have been left at such a high power setting at touchdown, especially since the auto thrust in such a system wouldn't have left the trottle at such a high power setting in the first place.
I think it substantially assists the pilot to have an unbroken habituated understanding below his conscious mind, that TL position ALWAYS equal engine power. I think this could have prevented leaving the ENG2 TL at a high power setting in the first place, and would have helped the pilot acting in an emergency to know (subconsciously know) to pull an advanced throttle lever back.
I noticed in the FDR data that during the rollout, the pilots disarmed and rearmed the spoilers, hoping the cycling would cause the spoilers to deploy. How wonderful a manual spoiler deploy lever would have been in those moments, but this emergency control was simply not there. AB crew know they have to become essentially system analysts when they learn to fly the AB (and to be fair Boeing pilots do as well). However who can be a fully functioning systems analyst and a diagnostic technician in a difficult landing situation and in an emergency?
Thus I'll close with this statement. A Raskin type single mode approach to HM design of primary flight controls and speed controls, that become emergency controls in an emergency, is a very good idea.
The other major airframe maker managed to create a single mode throttle system, in the sense that throttle position always equals engine power, and was not inhibited by the complexity of the system and flat state space constraints from doing so.
Someone said that cruise control on more recent cars do not move the gas pedal. True enough, but I would think the equivalent mode to the AB throttle system would be to press the gas pedal down about 3/4 full, then engage the cruise control, then the gas pedal would be left there while the cruise control remained engaged. Later when the cruise control was disengaged, the gas pedal would still be at 3/4 full. In the Boeing, the "gas pedal" would also be left where is was at when A/THR was disengaged, but at least you'd know where the engine power was before, and it wouldn't change after disengagement.
Please understand, I'm not trying to make a B vs AB argument, I'm making design choice arguments and using B and AB systems to illustrate.
I gotta go.
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Flight Safety,
thank you for your detailed explanations. I don't find a problem with what you say about emergency systems, like fire exinguishers, emergency circuit breakers, etc. ...
But this does not seem to have anything to do with this accident. Failure modes in airliners are so complex and manifold, that no simple emergency "handle" or "button" will do.
Since your conclusion again seems to be "moving thrust levers are better", because they better reflect what the aircraft does, I have to argue that Airbus thrust levers always directly relate to flight phase:
Start: push forward
Flight: Leave in the middle
Stop: Pull back.
Extremely simple, extraordinarily intuitive and habituating.
[edit]
Some more detailed remarks:
According to your reasoning, the throttles control the speed. What could be more instinctive then, in order to slow down, to pull back that what's making speed, i. e. the thrust levers.
I also wonder how you determine any generalised "pilot's mind in an emergency."
As has been repeated many times in this thread, the autothrust did not leave the engine "at [...] a high power setting", but roughly at the power needed to maintain approach speed.
Exactly the same power setting at which a moving lever-system would have remained. No difference here.
This was not a normal disconnect, in which the thrust rises to meet the lever position, but a so-called "involuntary disconnect", in which the thrust is frozen.
The action to pull back all thrust levers during flare is also exactly the same on either type of thrust control system design.
You still haven't made a convincing point, other than gut feeling, why pilots would be more likely to pull back moving thrust levers than non-moving ones.
[/edit]
Bernd
thank you for your detailed explanations. I don't find a problem with what you say about emergency systems, like fire exinguishers, emergency circuit breakers, etc. ...
But this does not seem to have anything to do with this accident. Failure modes in airliners are so complex and manifold, that no simple emergency "handle" or "button" will do.
Since your conclusion again seems to be "moving thrust levers are better", because they better reflect what the aircraft does, I have to argue that Airbus thrust levers always directly relate to flight phase:
Start: push forward
Flight: Leave in the middle
Stop: Pull back.
Extremely simple, extraordinarily intuitive and habituating.
[edit]
Some more detailed remarks:
[...] throttles) in my opinion must be designed to accommodate the pilot's mind in an emergency, when he will tend to act on rather than reason out the emergency
I also wonder how you determine any generalised "pilot's mind in an emergency."
I think it far less likely that an engine would have been left at such a high power setting at touchdown, especially since the auto thrust in such a system wouldn't have left the trottle at such a high power setting in the first place.
Exactly the same power setting at which a moving lever-system would have remained. No difference here.
This was not a normal disconnect, in which the thrust rises to meet the lever position, but a so-called "involuntary disconnect", in which the thrust is frozen.
I think [...] [moving thrust levers] could have prevented leaving the ENG2 TL at a high power setting in the first place, and would have helped the pilot acting in an emergency to know (subconsciously know) to pull an advanced throttle lever back.
You still haven't made a convincing point, other than gut feeling, why pilots would be more likely to pull back moving thrust levers than non-moving ones.
[/edit]
Bernd
Last edited by bsieker; 30th Aug 2007 at 19:48. Reason: removed non-pertinent material, added even more detailed commecnts.
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Correct me if I'm wrong, but would it not be the case that the only reasons earlier generations of aircraft with autothrust had moving thrust levers was because there was a direct, physical connection between the levers and the engines, so the autothrust system would control the levers, and the levers would control the engines?
If that was the case then would that make the 'moving thrust levers' design a limitation of the technology of the time, a side effect rather than an actual design feature?
If that was the case then would that make the 'moving thrust levers' design a limitation of the technology of the time, a side effect rather than an actual design feature?
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Originally Posted by DozyWannabe
Correct me if I'm wrong, but would it not be the case that the only reasons earlier generations of aircraft with autothrust had moving thrust levers was because there was a direct, physical connection between the levers and the engines, so the autothrust system would control the levers, and the levers would control the engines?
If that was the case then would that make the 'moving thrust levers' design a limitation of the technology of the time, a side effect rather than an actual design feature?
If that was the case then would that make the 'moving thrust levers' design a limitation of the technology of the time, a side effect rather than an actual design feature?
Sun worshipper
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to Daniel Franco Vallado
For one of the posters who have been accusing others to be paid by AI, to hide the truth, in short been accused of conspiracy, you seem to have a very thin skin.
Quite a few people have given you enough respect to discuss your theories, which, if I remember correctly, have not been discarded but considered the least likely, the least you could do is to try and consider their reasoning.
That's respect for you.
As I understand it, you have very little experience of reading accident reports and only joined Pprune in order to be allowed to discuss this very accident and an air collision over Brasil. May I suggest you took a look at -for instance - the report of the Air Inter A320 near Strasbourg in order to have a feel for the brainstorming the research of the likely causes of an accident would generate, especially when human / system interface is considered ?
What was said with humour above is that there is a point where we're leaving the realm of serious discussion to start delving into phantasies like IRQs and little green men...X files, this forum ain't !
Enough said.
On the same vein, I'd like to apologise to Dani, Hunter58, BOAC, Hand Solo...I'm sure there are others I forgot...for ignoring yet another item of SOP. I've worked for 7 airlines and flew jumpseats with another ten or so and I've never seen reversers handled by NHP...must be interesting when an airplane begins a slow waltz in Sheremetievo, for instance, in winter, or in Bombay during the Monsoon.
Well, I learn everyday.
Cheers
Quite a few people have given you enough respect to discuss your theories, which, if I remember correctly, have not been discarded but considered the least likely, the least you could do is to try and consider their reasoning.
That's respect for you.
As I understand it, you have very little experience of reading accident reports and only joined Pprune in order to be allowed to discuss this very accident and an air collision over Brasil. May I suggest you took a look at -for instance - the report of the Air Inter A320 near Strasbourg in order to have a feel for the brainstorming the research of the likely causes of an accident would generate, especially when human / system interface is considered ?
What was said with humour above is that there is a point where we're leaving the realm of serious discussion to start delving into phantasies like IRQs and little green men...X files, this forum ain't !
Enough said.
On the same vein, I'd like to apologise to Dani, Hunter58, BOAC, Hand Solo...I'm sure there are others I forgot...for ignoring yet another item of SOP. I've worked for 7 airlines and flew jumpseats with another ten or so and I've never seen reversers handled by NHP...must be interesting when an airplane begins a slow waltz in Sheremetievo, for instance, in winter, or in Bombay during the Monsoon.
Well, I learn everyday.
Cheers
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Let me frame my question...
Let me ask this question a little modified...
If this is the third accident with A320s where the pilots landing with one reverser locked up left the two TLs in opposite positions (forward and reverse), should we simply say that it was a human error?
Human error, three times, with professional pilots?...
Shouldn´t we look at how come these six pilots in three occasions committed this mistake?... And perhaps try to prevent this from happening by changing something in the machine?
Thanks to you all.
If this is the third accident with A320s where the pilots landing with one reverser locked up left the two TLs in opposite positions (forward and reverse), should we simply say that it was a human error?
Human error, three times, with professional pilots?...
Shouldn´t we look at how come these six pilots in three occasions committed this mistake?... And perhaps try to prevent this from happening by changing something in the machine?
Thanks to you all.
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Boeing a monopoly? When pray tell was that? Boeing had to fight hard to compete with McDonnell Douglas and Lockheed, and before that Douglas and deHavilland and Convair and Martin too. Airbus came along in the very late 60s. Today, among the full-size airliner makers in the west, only A and B survive. But Boeing NEVER had a monopoly. Get your facts straight. 
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So they are four?
marcio vp
you are forgeting the Phoenix/USA accident
you are forgeting the Phoenix/USA accident
So, we are talking about four accidents and eight well trained and experienced pilots.
Don´t you think I have a good question?
Let me ask this question a little modified...
If this is the third accident with A320s where the pilots landing with one reverser locked up left the two TLs in opposite positions (forward and reverse), should we simply say that it was a human error?
Human error, three times, with professional pilots?...
Shouldn´t we look at how come these six pilots in three occasions committed this mistake?... And perhaps try to prevent this from happening by changing something in the machine?
Thanks to you all.
If this is the third accident with A320s where the pilots landing with one reverser locked up left the two TLs in opposite positions (forward and reverse), should we simply say that it was a human error?
Human error, three times, with professional pilots?...
Shouldn´t we look at how come these six pilots in three occasions committed this mistake?... And perhaps try to prevent this from happening by changing something in the machine?
Thanks to you all.
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On the same vein, I'd like to apologise to Dani, Hunter58, BOAC, Hand Solo...I'm sure there are others I forgot...for ignoring yet another item of SOP. I've worked for 7 airlines and flew jumpseats with another ten or so and I've never seen reversers handled by NHP...must be interesting when an airplane begins a slow waltz in Sheremetievo, for instance, in winter, or in Bombay during the Monsoon
Well, I learn everyday.
(cant seem to get Lemurins quote above to go blue)
I have worked for a few airlines in which the NHP/PM operate the thrust levers to initiate reverse, British Airways for one. After all you don't steer the A/C using reverse thrust. If it is causing problems you call to cancel and maybe re-apply. Didnt seem to cause problems even on a windy day at Kai Tak.
Well, I learn everyday.
(cant seem to get Lemurins quote above to go blue)
I have worked for a few airlines in which the NHP/PM operate the thrust levers to initiate reverse, British Airways for one. After all you don't steer the A/C using reverse thrust. If it is causing problems you call to cancel and maybe re-apply. Didnt seem to cause problems even on a windy day at Kai Tak.
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The deepest ROOT cause.
The deepest root cause of this accident may well be, the extremely slow acceleration of the engines from idle.
Follow me.
(General info: FCOM does inform us of the increased idle when using reverse, but it does not state why. Common sense would explain that the core engine needs increased idle to survive the slight airflow disturbances caused by reverse).
1. (fact) The A-320's IAE engines accelerate very slowly from idle.
2. (fact) Idle must be increased when reverse thrust is applied.
3. (hypothesis) Because idle response of the engines is so slow, decision has been made to give the engines a headstart on the operation of the reverse sleeves. (fact) Idle is increased as thrust levers are placed in the reverse range, not when reverse sleeves are in the reverse position.
4. (fact) Because of 3, there is a slight stopping performance penalty in putting the thrust lever in reverse range, when reverser is (known to be) not operational.
5. (fact) Because of 4, operational procedures are written, which prescribe how to handle in case of deactivated reverser(s).
6. (hypothesis) Changed insights (fact) have lead to changed procedures.
7. (hypothesis) Points 4, 5, 6 together into one brain may be a setup for confusion.
8. (hypothesis) On approach to a wet and not so long runway, the conscious mind may have made a (proper) choice to *not* pull the thrust lever of the deactivated reverser into the reverse range.
Point 7 manifested itself in the millisecond that the brain fired its' action pulse to the thrust lever hand - instead of leaving the one thrust lever behind at the idle detent, this leaving behind was done half a second too early, at the CLB detent.
9. (fact) Results are known all too well and are presently being investigated.
================================
All the discussion so far has been about points 8 and 9. Very interesting by themselves, but only scratching the surface.
In the discussion about point 8, I want to state clearly, but at this moment I have no time to elaborate on it further - the autothrust system with non-moving thrust levers is well thought out and logical, but it is NOT NATURAL!
Follow me.
(General info: FCOM does inform us of the increased idle when using reverse, but it does not state why. Common sense would explain that the core engine needs increased idle to survive the slight airflow disturbances caused by reverse).
1. (fact) The A-320's IAE engines accelerate very slowly from idle.
2. (fact) Idle must be increased when reverse thrust is applied.
3. (hypothesis) Because idle response of the engines is so slow, decision has been made to give the engines a headstart on the operation of the reverse sleeves. (fact) Idle is increased as thrust levers are placed in the reverse range, not when reverse sleeves are in the reverse position.
4. (fact) Because of 3, there is a slight stopping performance penalty in putting the thrust lever in reverse range, when reverser is (known to be) not operational.
5. (fact) Because of 4, operational procedures are written, which prescribe how to handle in case of deactivated reverser(s).
6. (hypothesis) Changed insights (fact) have lead to changed procedures.
7. (hypothesis) Points 4, 5, 6 together into one brain may be a setup for confusion.
8. (hypothesis) On approach to a wet and not so long runway, the conscious mind may have made a (proper) choice to *not* pull the thrust lever of the deactivated reverser into the reverse range.
Point 7 manifested itself in the millisecond that the brain fired its' action pulse to the thrust lever hand - instead of leaving the one thrust lever behind at the idle detent, this leaving behind was done half a second too early, at the CLB detent.
9. (fact) Results are known all too well and are presently being investigated.
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All the discussion so far has been about points 8 and 9. Very interesting by themselves, but only scratching the surface.
In the discussion about point 8, I want to state clearly, but at this moment I have no time to elaborate on it further - the autothrust system with non-moving thrust levers is well thought out and logical, but it is NOT NATURAL!