TAM A320 crash at Congonhas, Brazil
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Flyingnewbie10:
The resolvers are the sole sensor inputs to the EECs (FADEC) regarding TLA.
The pots send their data to the flight control computers.
All in my post earlier here where I thought a more detailed explanation of the A320 thrust lever design might be helpful.
This is an interesting question and one I had wondered about - A/T on or off. One would assume that since thrust commands (TLA or A/T) and actual thrust levels (EPR/N1) are key data points that the resolvers should provide the data for the manual thrust command FDR traces.
In practice I would imagine that the FDR gets filtered ARINC data from the EECs and no direct data from the resolvers. In A/T mode, the FDR should also have an recorded ARINC data channel from the FMGS-EEC interface. Ideally the potentiometers or resolvers should also have a direct trace on the FDR to preclude computer errors from being incorrectly recorded as actual control movements.
All that said, the Airbus manual thrust control system is fairly robust and typically industry standard.
what feeds the TLA to the A/THR ? The resolvers or the potentiometers ?
The pots send their data to the flight control computers.
All in my post earlier here where I thought a more detailed explanation of the A320 thrust lever design might be helpful.
which system does the FDR read the TLA from when A/THR is on ?
The resolvers or the potentiometers ?
The resolvers or the potentiometers ?
In practice I would imagine that the FDR gets filtered ARINC data from the EECs and no direct data from the resolvers. In A/T mode, the FDR should also have an recorded ARINC data channel from the FMGS-EEC interface. Ideally the potentiometers or resolvers should also have a direct trace on the FDR to preclude computer errors from being incorrectly recorded as actual control movements.
All that said, the Airbus manual thrust control system is fairly robust and typically industry standard.
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Originally Posted by Sdruvss
That is where fault can emerge: Arbitration
Every system that has redundancy, on some point has arbitration. It's impossible to project a redundant system without arbitration. On some point, there is a decision beeing made by a circuit
Every system that has redundancy, on some point has arbitration. It's impossible to project a redundant system without arbitration. On some point, there is a decision beeing made by a circuit
If you want to know the chances of a metastability phenomenon happening in everyday use, there was a reasonable set of MIT lectures by Devadas on the topic, but they seem to have disappeared (even the topic "operating systems" seems to have disappeared from MIT's curriculum. They must know something we don't. Or maybe it's that Bill G was a Harvard student....).
But in two words: extremely rare. In a redundant system which was built to be sensitive to such failures, not in the expected lifetime of the system.
PBL
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go around attempt after T/R deployed
Thanks NIgel. And yet when I suggested some ways back in the thread that the A320 should be reprogrammed to accept that a Full Stop is the only recourse when T/R is deployed. And to allow the pilots access to GS and all other facilities to enable Full Stop to be quickly achieved and/or even to actuate max autobrake by itself once weight is on both main bogeys and T/R deployed. But some pilots said they preferred to have the option of taking off again even though T/R deployed .
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bsieker
I took the liberty to copy and correct your findings :
..."The bottom line is: A/THR disconnects when a thrust reverser is deployed.
It goes as follows:
- TLA readout corresponds to a certain EPR value
- TLA target EPR value is upper limit for autothrust
- A/THR working normally in speed mode, using engine #2 No. BOTH
- TL #1 set to idle. No problem, just limits thrust usable by A/THR to idle
for that engine.
- TLA EPR value for Eng #1 becomes 0.98 There is the first disconnect condition as in this case, TLA #1 EPR < FADEC target EPR - .2 (?)
- TL #1 set to reverse:
. TLA EPR becomes NCD ("no computed data")
. FMGC continues to use last valid value (0.98) No, the same 1.2 EPR needed to maintain the approach speed and which was applied to #2 engine after the deconnection.
. FADEC uses a value of 0.75 with engine in reverse (FADEC EPR target feedback is upper limited to EPR TLA, EPR IDLE is reduced by 0.2 when reverser is deployed more than 15% (0.98 - 0.2 makes 0.78, but I assume that's close enough))
. comparison of the two values (0.98 and 0.75) is greater than 0.15.
. if that condition persists for more than 1.8s, A/THR disconnects. 2nd disconnect condition"
I do not have the graphs handy at this time but the first condition should have applied.
RightwayUp
Thanks. I had forgotten that one !
..."The bottom line is: A/THR disconnects when a thrust reverser is deployed.
It goes as follows:
- TLA readout corresponds to a certain EPR value
- TLA target EPR value is upper limit for autothrust
- A/THR working normally in speed mode, using engine #2 No. BOTH
- TL #1 set to idle. No problem, just limits thrust usable by A/THR to idle
for that engine.
- TLA EPR value for Eng #1 becomes 0.98 There is the first disconnect condition as in this case, TLA #1 EPR < FADEC target EPR - .2 (?)
- TL #1 set to reverse:
. TLA EPR becomes NCD ("no computed data")
. FMGC continues to use last valid value (0.98) No, the same 1.2 EPR needed to maintain the approach speed and which was applied to #2 engine after the deconnection.
. FADEC uses a value of 0.75 with engine in reverse (FADEC EPR target feedback is upper limited to EPR TLA, EPR IDLE is reduced by 0.2 when reverser is deployed more than 15% (0.98 - 0.2 makes 0.78, but I assume that's close enough))
. comparison of the two values (0.98 and 0.75) is greater than 0.15.
. if that condition persists for more than 1.8s, A/THR disconnects. 2nd disconnect condition"
This is consistent with the observed behaviour in the FDR graphs that A/THR disconnects about 2s after the thrust reverser was fully deployed on engine #1, at which time also EPR on engine #2 freezes.
RightwayUp
A quick look in my FCOM shows an ECAM of "AUTO FLT A/THR OFF" with a chime if autothrust is disconnected any way other than instinctive disconnect or BOTH thrust levers idle. However this message is inhibited between touchdown & 80 kts!
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Of course it has happened before!
I would like to know if one of the pilots here admits that could make the 'mistake' that caused this accident.
Last edited by paull; 13th Aug 2007 at 20:00. Reason: Added post number. Not proficient enough to link to it!
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Of mistakes
I would like to know if one of the pilots here admits that could make the “mistake” that caused this accident.
But there is NEVER a judgement of value (he screwed up...had a brain fart...was foolish...etc...) but a search for the conditions that allowed the mistake to be made.
As a group, we also know that when something goes wrong, it generally happens very fast. In this instance, they went from a routine landing with very little out of the ordinary into a major emergency in mere seconds. An emergency they couldn't walk away from.
In that respect, yes, as a group we accept that mistrakes can be made and the resultant conclusion that the public would start pointing fingers...
Does that prevent me from flying again to-morrow ?
In my opinion, the investigation will have a good look at the flight preparation.
I still wonder why, with all the Pireps that have been made in the past two days, plus the ATR skidding off the runway, they could have dispatched that airplane -with one locked-out T/R - into a runway that in all respects was contaminated.
I also wonder why the crew, while showing a real concern for the runway state, did not ask the - IMHO right - question about *braking action* or *braking coefficient*.
The rest is for HF specialists to respond to.
As a group, and bar the now-obscene B vs AB comments, we want these answers.
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@vapilot
One should always be very careful as to what one ASSUMES about FDR parameters.
As you say, you'd think that something like TLA would be a fundamental FDR-required parameter. But it isn't! Part 121, Appendix M only requires that "Throttle/power Lever position" be recorded "For airplanes with non-mechanically linked cockpit engine controls". (Item #42 in the table of parameters). So for aircraft like the accident aircraft here, which is a FADEC engined aircraft, TLA is required. For any hydro-mech controlled engine, there's no requirement to measure TLA (or equivalent) AT ALL.
One would assume that since thrust commands (TLA or A/T) and actual thrust levels (EPR/N1) are key data points that the resolvers should provide the data for the manual thrust command FDR traces.
As you say, you'd think that something like TLA would be a fundamental FDR-required parameter. But it isn't! Part 121, Appendix M only requires that "Throttle/power Lever position" be recorded "For airplanes with non-mechanically linked cockpit engine controls". (Item #42 in the table of parameters). So for aircraft like the accident aircraft here, which is a FADEC engined aircraft, TLA is required. For any hydro-mech controlled engine, there's no requirement to measure TLA (or equivalent) AT ALL.
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Armchair
Thanks NIgel. And yet when I suggested some ways back in the thread that the A320 should be reprogrammed to accept that a Full Stop is the only recourse when T/R is deployed. And to allow the pilots access to GS and all other facilities to enable Full Stop to be quickly achieved and/or even to actuate max autobrake by itself once weight is on both main bogeys and T/R deployed. But some pilots said they preferred to have the option of taking off again even though T/R deployed .
Read my post again, I did not say I would never GA after T/Rs deployed. I just said it goes against all the instincts / planning. However, who knows what I may come across tomorrow with my colleague? People criticse the AB for being "too clever", however, if between you and it you get into a "hole" there is invariably a "quick way out" to achieve what you want. What you are proposing is a system that makes these options unavailable.
Take the conjecture of CGH as an example. Throughout the whole landing roll, one single action could have either started the stopping process (#2 TL => Idle) or GA (#1 T/L => TOGA) i.e. the pilots were "in control" of the situation. It is unfortunate that they maybe were confused / led down the garden path / aware too late of what was happening. Training / SOPs and maybe some logic amendments may help prevent this again...
Compare this to your suggestions. They are second guessing the pilots, making their future decisions for them, and removing "options". Say they touched down, just selected Rev, and saw an aircraft crossing in front of them...? Your suggestions force them into trying to stop... Even the Airbus currently gives them an option, even against all I said above
Think static v dynamic / current situation versus future etc...
NoD
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Lemurian, thanks for your reply. Please bear with me some more ...
You seem to have a better understanding of the thrust control system's terms, I'd greatly appreciate it if you could read p148 of the incident report of the Taipei-Sungshan-Overrun (http://www.asc.gov.tw/acd_files/189-c1contupload.pdf), and tell me what I understood wrong.
Hm, yes, obviously.
[QUOTE]
- TL #1 set to idle. No problem, just limits thrust usable by A/THR to idle
for that engine.
- TLA EPR value for Eng #1 becomes 0.98
TL#1 is pulled to idle at around 18:48:22, A/THR only disconnects at 18:48:29. So it seems this was not the case.
FMGC uses 0.98 (last valid) as TLA EPR value. The report again:
It also says,
According to Airbus, this condition was the one triggering the disconnect in Taipei-Sungshan. Doesn't mean it has to be, here, but the timing implies it.
You seem to have a better understanding of the thrust control system's terms, I'd greatly appreciate it if you could read p148 of the incident report of the Taipei-Sungshan-Overrun (http://www.asc.gov.tw/acd_files/189-c1contupload.pdf), and tell me what I understood wrong.
- A/THR working normally in speed mode, using engine #2
No. BOTH
[QUOTE]
- TL #1 set to idle. No problem, just limits thrust usable by A/THR to idle
for that engine.
- TLA EPR value for Eng #1 becomes 0.98
There is the first disconnect condition as in this case, TLA #1 EPR < FADEC target EPR - .2 (?)
- TL #1 set to reverse:
. TLA EPR becomes NCD ("no computed data")
. FMGC continues to use last valid value (0.98)
. TLA EPR becomes NCD ("no computed data")
. FMGC continues to use last valid value (0.98)
No, the same 1.2 EPR needed to maintain the approach speed and which was applied to #2 engine after the deconnection.
the FMGC ARINC acquisition behaviour (per design) in case of NCD is to keep the last EPR TLA valid value.
the condition triggers when the "THR TARGET feedback of one FADEC is different by 0.15 from the ATHR EPR TARGET limited to the corresponding EPR TLA.
. FADEC uses a value of 0.75 with engine in reverse (FADEC EPR target feedback is upper limited to EPR TLA, EPR IDLE is reduced by 0.2 when reverser is deployed more than 15% (0.98 - 0.2 makes 0.78, but I assume that's close enough))
. comparison of the two values (0.98 and 0.75) is greater than 0.15.
. if that condition persists for more than 1.8s, A/THR disconnects.
. comparison of the two values (0.98 and 0.75) is greater than 0.15.
. if that condition persists for more than 1.8s, A/THR disconnects.
2nd disconnect condition"
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The logic required as far as the pilot is concerned is quite simple. The pilot tells the aircraft to stop by retarding the thrust levers and once that is accomplished, the aircraft will provide as much assistance to the pilot to stop as is desired.
As far as I can tell from this thread, pre-Taipei the instruction with 1 reverser inop was to pull *both* the thrust levers to idle and then select reverse on the lever with the functioning reverser. For whatever HF reason this led on rare occasions to the pilot pulling only 1 lever to idle, causing these long landings and unfortunately, this crash.
No doubt the investigators will be poring over this incident for a long time to come, but if the lever was left considerably forward of idle this is not a shortfall in the design of the system, the logic or the programming.
There are many different breeds of pilot and the A320 system, and its progeny have by now been around long enough for some pilots to prefer that methodology. These pilots would kick up just as much of a a stink if they were forced back to the yoke as the more traditionalist pilots kick up over the sidestick.
As far as I can tell from this thread, pre-Taipei the instruction with 1 reverser inop was to pull *both* the thrust levers to idle and then select reverse on the lever with the functioning reverser. For whatever HF reason this led on rare occasions to the pilot pulling only 1 lever to idle, causing these long landings and unfortunately, this crash.
No doubt the investigators will be poring over this incident for a long time to come, but if the lever was left considerably forward of idle this is not a shortfall in the design of the system, the logic or the programming.
There are many different breeds of pilot and the A320 system, and its progeny have by now been around long enough for some pilots to prefer that methodology. These pilots would kick up just as much of a a stink if they were forced back to the yoke as the more traditionalist pilots kick up over the sidestick.
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This may have been covered somewhere in here, so apologies, but I'm confused with this whole thing, surely even if you've got an inoperable thrust reverser on one engine it would feel completely unnatural to leave a thrust lever in the CLB detent on landing and not at least bring the thrust lever back to at least idle, surely common sense would make you do that anyway. The crew must have known the ground spoilers wouldn't have deployed if the TL was left in CLB? This is a very wierd accident, was fatigue to play does anyone think?
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sinbin makes a good point. it would be natural to bring both throttles back...and if not into reverse, at least to idle ala pre taipei.
sdruvss: I don't think the pilots are likely to have made this mistake.
Impossible? no. Improbable, yes.
dozy: you've said something that make me really think<<<The pilot tells the aircraft to stop by retarding the thrust levers >>>
that is not how you fly airplanes...you tell the engines what to do with the thrust levers...they are not STOP LEVERS. IF you power to idle in flight, the plane doesn't stop. It may lose speed if you hold altitude. You will keep speed if you lose altitude...but the plane doesn't STOP( while inflight)
You are speaking as if you really know computers and you have my respect...but with this LOGIC, you forget what thrust levers/throttles were when these men first learned to fly.
Now, I do know that you can trigger a multitude of events by doing certain things. And that rejected takeoffs can be facilitated by certain automatic functions triggered by throttle/thrust lever movements. We all know that automatic spoilers can improve stopping performance and they are nice to have. But to think of throttles/thrust levers as stop levers leaves a gap on the human side.
It is time to rethink the LOGIC.
sdruvss: I don't think the pilots are likely to have made this mistake.
Impossible? no. Improbable, yes.
dozy: you've said something that make me really think<<<The pilot tells the aircraft to stop by retarding the thrust levers >>>
that is not how you fly airplanes...you tell the engines what to do with the thrust levers...they are not STOP LEVERS. IF you power to idle in flight, the plane doesn't stop. It may lose speed if you hold altitude. You will keep speed if you lose altitude...but the plane doesn't STOP( while inflight)
You are speaking as if you really know computers and you have my respect...but with this LOGIC, you forget what thrust levers/throttles were when these men first learned to fly.
Now, I do know that you can trigger a multitude of events by doing certain things. And that rejected takeoffs can be facilitated by certain automatic functions triggered by throttle/thrust lever movements. We all know that automatic spoilers can improve stopping performance and they are nice to have. But to think of throttles/thrust levers as stop levers leaves a gap on the human side.
It is time to rethink the LOGIC.
Mach 3
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Sdruvss
Let me recount another story of mine....
The very first time I ever flew the 737 with my wife, on departure from a Southern Spanish airfield, where we rarely followed the SID, (which involved a turn to the right, to come back overhead the airfield), and instead normally got a left turn direct towards a certain waypoint, I was instructed to turn right.
Guess which way I turned, until she pointed out the error of my ways....
Never say never in this business.
PS: I still suffering the consequences of this mistake today....
It's the same as one driver wishing to turn left, turns right. This don't happen.
The very first time I ever flew the 737 with my wife, on departure from a Southern Spanish airfield, where we rarely followed the SID, (which involved a turn to the right, to come back overhead the airfield), and instead normally got a left turn direct towards a certain waypoint, I was instructed to turn right.
Guess which way I turned, until she pointed out the error of my ways....
Never say never in this business.
PS: I still suffering the consequences of this mistake today....
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to Nigel:
Currently the A320 does not allow you to use GS if one of the TL is not in idle. But it will allow EPR to match the lever that is not in idle. This is a case of a plane thats holding back some vital controls from the pilot and yet allowing (if not pushing) him to fall into a very big hole.
Which means it is a very unforgiving plane as far as errors are concerned. Or at least in this particular instance, where everything is dandy UNLESS you leave one TL out of idle. In which case God help you , because the plane surely wont !
The intermediate swimmers are usually the ones to drown. They know enough to get themselves into deep trouble and yet not enough to get out safely.
The A320 has enough automation and "logic" to get you into a deep deep hole (or allow you to) unless you play carefully by ITS rules. Do it or die as it were !
Give the pilot full command of the planes vital controls, dont deny anything is what it SHOULD do.
Currently the A320 does not allow you to use GS if one of the TL is not in idle. But it will allow EPR to match the lever that is not in idle. This is a case of a plane thats holding back some vital controls from the pilot and yet allowing (if not pushing) him to fall into a very big hole.
Which means it is a very unforgiving plane as far as errors are concerned. Or at least in this particular instance, where everything is dandy UNLESS you leave one TL out of idle. In which case God help you , because the plane surely wont !
The intermediate swimmers are usually the ones to drown. They know enough to get themselves into deep trouble and yet not enough to get out safely.
The A320 has enough automation and "logic" to get you into a deep deep hole (or allow you to) unless you play carefully by ITS rules. Do it or die as it were !
Give the pilot full command of the planes vital controls, dont deny anything is what it SHOULD do.
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About computer logic, allow me some simplistic observations:
1. We, humans, are capable of doing ALL complex calculations that computers do. The difference is we are a billion times slower (or more)...
2. We, humans, TELL computers what we want them to do.
3. Since they "obey" so well, and so fast, one can imagine computers can almost "think".
4. We forget the only thing a computer can do, is fast calculations. And we leave them in charge of tasks we don't like (or we are not good at) and even allow them to make simple "decisions". I remember how nice it was to "engage" my first Auto Pilot. Then Auto Throttle, wow!
5. We've got to a point where modern aircraft need computers to help pilots fly them. Simple decisions, like IF THIS - GO TO THAT, we (pilots) don't mind if computers do so.
6. We, humans, are underestimating computers, they are capable of taking care of incredible amount of tasks, and yes, they can make important decisions based on their fast and multiple calculations. We only have to imagine, and computers will execute with perfection.
Let's only imagine that the computer on-board TAM A-320 could have done a bit of more "thinking", like: "OK, we have engine 1 on reverse, and eng 2 on accelerate command. WoW, fine, but the pilot didn't make-up his mind yet, so I won't give him spoilers nor A/B. Oops, he went to manual brakes. Well, maybe he just touched the toe brakes, his intention was to move rudder only. No, I won't give him spoilers (I can forget about A/B, he is in charge of wheel brakes). After all, eng 2 TL is still at the same position.
But wait!! He has one engine in reverse for quite a while now, and he is still on the brakes. Know what? I'm going to give this guy all he needs for a full stop. I will shut down engine #2, deploy spoilers and help him with the brakes. I don't think he will be mad at me for doing this without asking. After all, if he wants to continue flying, he can still do it later. Just a TL off position alone does not mean the pilot wants to continue flying. And with one engine on reverse and one accelerating he (we) won't fly anyways. I've heard from an old and wise computer of a pen that got stuck on the TL's tray and the pilot couldn't move it (yes, we, computers can divagate - we think fast, remember?) But if I don't help him stop NOW, he (we) won't fly again later... I'm going to emergency stop mode!"
Sorry if I got carried away. I am learning a lot from many of you and would like to continue enjoying your company.
Rob
1. We, humans, are capable of doing ALL complex calculations that computers do. The difference is we are a billion times slower (or more)...
2. We, humans, TELL computers what we want them to do.
3. Since they "obey" so well, and so fast, one can imagine computers can almost "think".
4. We forget the only thing a computer can do, is fast calculations. And we leave them in charge of tasks we don't like (or we are not good at) and even allow them to make simple "decisions". I remember how nice it was to "engage" my first Auto Pilot. Then Auto Throttle, wow!
5. We've got to a point where modern aircraft need computers to help pilots fly them. Simple decisions, like IF THIS - GO TO THAT, we (pilots) don't mind if computers do so.
6. We, humans, are underestimating computers, they are capable of taking care of incredible amount of tasks, and yes, they can make important decisions based on their fast and multiple calculations. We only have to imagine, and computers will execute with perfection.
Let's only imagine that the computer on-board TAM A-320 could have done a bit of more "thinking", like: "OK, we have engine 1 on reverse, and eng 2 on accelerate command. WoW, fine, but the pilot didn't make-up his mind yet, so I won't give him spoilers nor A/B. Oops, he went to manual brakes. Well, maybe he just touched the toe brakes, his intention was to move rudder only. No, I won't give him spoilers (I can forget about A/B, he is in charge of wheel brakes). After all, eng 2 TL is still at the same position.
But wait!! He has one engine in reverse for quite a while now, and he is still on the brakes. Know what? I'm going to give this guy all he needs for a full stop. I will shut down engine #2, deploy spoilers and help him with the brakes. I don't think he will be mad at me for doing this without asking. After all, if he wants to continue flying, he can still do it later. Just a TL off position alone does not mean the pilot wants to continue flying. And with one engine on reverse and one accelerating he (we) won't fly anyways. I've heard from an old and wise computer of a pen that got stuck on the TL's tray and the pilot couldn't move it (yes, we, computers can divagate - we think fast, remember?) But if I don't help him stop NOW, he (we) won't fly again later... I'm going to emergency stop mode!"
Sorry if I got carried away. I am learning a lot from many of you and would like to continue enjoying your company.
Rob
Last edited by Rob21; 14th Aug 2007 at 01:44. Reason: typo
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Sdruvss
SR71 corrects the notion and I can confirm that more than once in the car I have found myself stopping at green traffic lights when distracted by 'more important' matters. One of which I recall vividly was ferrying a top Head Office boss from a meeting at our branch office to an important meeting elsewhere and I was concentrating on leaving him with a favorable impression of my conversational abilities and general wit!
I have never found out what happens when I have unconsciously reached a red traffic light ... I think I would be kidding myself if I assumed I had a kind of built-in failsafe logic that has been dealing with that successfully.
I also agree with bomarc to the extent that TLs are not STOP levers. Brake pedals are STOP levers and in an automatic car that has long since been good enough ... I don't mean to trivialise here ...
That means I guess I disagree with PBL on the same basis when he reminded us that the A320 braking system obviously can't ever have been compared to bicycle brakes at any level of analysis.
I guess I was aged about 3 when I started computing speed and began to learn how brake levers led to the antidote on my first trike. Consequently I believe I would have been hardwired like that before JFK got shot.
Ten years later, my first drive in a real car on the farm was in an old minivan which had a throttle fault which meant it was stuck open at maybe 2000rpm. I had already driven tractors which had thumping great independent brake pedals that could stop a wheel dead and turn the thing on a sixpence. Yet in that little minivan I almost crashed because I was completely surprised by the superiority of continuing uncalled for power versus much less powerful brakes.
Thankfully I already knew how to disengage the power train.
At about the same time astronauts were driving the moon buggy in 1/6th earth Gravity. I wonder if that stopped on the TLs or good old Brake Levers?
Well the NASA website has popped my bubble ... the Moon-buggy (LRV) did have mechanical brakes, but a T-shaped hand controller situated between the two seats controlled the four drive motors, two steering motors and brakes. Moving the stick forward powered the LRV forward, left and right turned the vehicle left or right, pulling backwards activated the brakes. Activating a switch on the handle before pulling back would put the LRV into reverse. Pulling the handle all the way back activated a parking brake.
So I guess I must bow to greater precedent ...
Amazing, this thread has me dredging up experience from decades ago which I know are still hardwired...but then my spacial awareness never was good enough to fly any simulator of the Lunar Excursion Module - guess I was never cut out to be the Right Stuff like those guys.
The Human Factors in this are mind-boggling.
It's the same as one driver wishing to turn left, turns right. This don't happen.
I have never found out what happens when I have unconsciously reached a red traffic light ... I think I would be kidding myself if I assumed I had a kind of built-in failsafe logic that has been dealing with that successfully.
I also agree with bomarc to the extent that TLs are not STOP levers. Brake pedals are STOP levers and in an automatic car that has long since been good enough ... I don't mean to trivialise here ...
That means I guess I disagree with PBL on the same basis when he reminded us that the A320 braking system obviously can't ever have been compared to bicycle brakes at any level of analysis.
I guess I was aged about 3 when I started computing speed and began to learn how brake levers led to the antidote on my first trike. Consequently I believe I would have been hardwired like that before JFK got shot.
Ten years later, my first drive in a real car on the farm was in an old minivan which had a throttle fault which meant it was stuck open at maybe 2000rpm. I had already driven tractors which had thumping great independent brake pedals that could stop a wheel dead and turn the thing on a sixpence. Yet in that little minivan I almost crashed because I was completely surprised by the superiority of continuing uncalled for power versus much less powerful brakes.
Thankfully I already knew how to disengage the power train.
At about the same time astronauts were driving the moon buggy in 1/6th earth Gravity. I wonder if that stopped on the TLs or good old Brake Levers?
Well the NASA website has popped my bubble ... the Moon-buggy (LRV) did have mechanical brakes, but a T-shaped hand controller situated between the two seats controlled the four drive motors, two steering motors and brakes. Moving the stick forward powered the LRV forward, left and right turned the vehicle left or right, pulling backwards activated the brakes. Activating a switch on the handle before pulling back would put the LRV into reverse. Pulling the handle all the way back activated a parking brake.
So I guess I must bow to greater precedent ...
Amazing, this thread has me dredging up experience from decades ago which I know are still hardwired...but then my spacial awareness never was good enough to fly any simulator of the Lunar Excursion Module - guess I was never cut out to be the Right Stuff like those guys.
The Human Factors in this are mind-boggling.
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bomarc brings up a very good point. Thrust levers from the time we learned to fly control the thrust of the engines and at idle can be used to reverse the thrust by pulling the reverser levers back. They were never considered stop levers.
Then we build airplanes with technology that only let you get GS and auto brakes if you have the throttles in idle first. Also if you miss one TL and leave it above idle with no throttle movement you go to a high fwd thrust trying to land with one TR inop. Your only clue is the sound of the engine spooling up before touchdown but no throttle movement. The computer may have gotten wrong data about the TLA and done this even in the unlikely possiblity the TL was at idle but it didn't sense it. I have never flown an aircraft with this type of logic so do not understand the loyalty so many posters here have to giving this kind of control to a computer and accepting what ever it gives you as better than what a pilot could do if allowed to override the logic.
Then we build airplanes with technology that only let you get GS and auto brakes if you have the throttles in idle first. Also if you miss one TL and leave it above idle with no throttle movement you go to a high fwd thrust trying to land with one TR inop. Your only clue is the sound of the engine spooling up before touchdown but no throttle movement. The computer may have gotten wrong data about the TLA and done this even in the unlikely possiblity the TL was at idle but it didn't sense it. I have never flown an aircraft with this type of logic so do not understand the loyalty so many posters here have to giving this kind of control to a computer and accepting what ever it gives you as better than what a pilot could do if allowed to override the logic.
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You're parsing semantics - I didn't say thrust levers were STOP levers, I said that the pilot retards them (as part of the sequence of actions he performs - guess I should have made that explicit) when he wishes the aircraft to stop.
I deliberately rendered the action in a very simple way to demonstrate that you don't need to know about complex real-time systems, logic trees and all the other gubbins that the anti-AB brigade claim you do to fly the thing.
bubbers44: How long ago did you learn to fly though? Many younger pilots got their first job on the A320 fleet. You can't put the genie back in the bottle.
I deliberately rendered the action in a very simple way to demonstrate that you don't need to know about complex real-time systems, logic trees and all the other gubbins that the anti-AB brigade claim you do to fly the thing.
bubbers44: How long ago did you learn to fly though? Many younger pilots got their first job on the A320 fleet. You can't put the genie back in the bottle.