Reducing thrust in cruise for overspeed
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Gretchenfrage
The reason I keep saying involve the manufacturer is because of FBW. A conventional response to an under or over speed may not take into account the aircraft behaviour due normal law protections. There have been incidents of AP disconnection due over speed and then subsequent engagement of alpha prot causing rapid climb resulting in near air miss. There have been low airspeed events without any failure but due to unusual environmental changes. We know that a pilot cannot expect survive by his own experiences alone. The manufacturer with his resources provides a better platform to tackle these events. Experience is not a name given to mistakes we committed and got away.
The reason I keep saying involve the manufacturer is because of FBW. A conventional response to an under or over speed may not take into account the aircraft behaviour due normal law protections. There have been incidents of AP disconnection due over speed and then subsequent engagement of alpha prot causing rapid climb resulting in near air miss. There have been low airspeed events without any failure but due to unusual environmental changes. We know that a pilot cannot expect survive by his own experiences alone. The manufacturer with his resources provides a better platform to tackle these events. Experience is not a name given to mistakes we committed and got away.
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vilas
Don’t get me wrong; I sure enough don’t dare excluding any manufacturer. With the complex aircraft we fly, as a pilot it would be preposterous to think we simply know better.
Experience however should keep us alert. FBW is not the wonderful saviour the industry likes us to believe. There are still traps involved and, worse, reluctance to correct them due to some engineer’s pride, but mostly due to the deplorable pack of wolves called litigation lawyers especially from the USA. Any change, even of the most obvious design flaw, would have them backtrack any former incident involving the design, ensuing an avalanche of lawsuits.
The thread starts with the question of thrust reduction in case of overspeed:
Is it ok to go to idle, or should we follow the manufacturer’s advice to only go halfway and use speedbrakes.
Some say follow strictly manufacturer’s FCOM/QRH/SOP, others are quite reluctant to extend any speedbrakes.
We can debate for hours, but here’s the problem:
1. Aerodynamically it makes basically no sense at high altitude to destroy something we are normally struggling for, namely lift.
2. Overspeed at high altitude has not caused an accident in recent times, low speed (or low lift) has.
So why would any manufacturer want lift destruction to counteract high speed??
One of them because his FBW would climb in case of massive overspeed and I hope we all agree that this is undesirable. Another one because he wants thrust levers only halfway back due to its engines unusual long spool-up time.
In both cases I raise the ominous “Gretchenfrage”, the core question:
Why does the manufacturor not cure the sickness and simply fights the symptom? I say:
Get the FBW or EEC logic right before you suggest manoevers that put us in a worse situation to counteract the flaw!
That is what I mean by not unconditionally trusting manufacturers, FCOM/QRH and SOPs. They have an agenda that is called profit. I have one that is called survival, in the economical and physical sense.
They do not always match!
Don’t get me wrong; I sure enough don’t dare excluding any manufacturer. With the complex aircraft we fly, as a pilot it would be preposterous to think we simply know better.
Experience however should keep us alert. FBW is not the wonderful saviour the industry likes us to believe. There are still traps involved and, worse, reluctance to correct them due to some engineer’s pride, but mostly due to the deplorable pack of wolves called litigation lawyers especially from the USA. Any change, even of the most obvious design flaw, would have them backtrack any former incident involving the design, ensuing an avalanche of lawsuits.
The thread starts with the question of thrust reduction in case of overspeed:
Is it ok to go to idle, or should we follow the manufacturer’s advice to only go halfway and use speedbrakes.
Some say follow strictly manufacturer’s FCOM/QRH/SOP, others are quite reluctant to extend any speedbrakes.
We can debate for hours, but here’s the problem:
1. Aerodynamically it makes basically no sense at high altitude to destroy something we are normally struggling for, namely lift.
2. Overspeed at high altitude has not caused an accident in recent times, low speed (or low lift) has.
So why would any manufacturer want lift destruction to counteract high speed??
One of them because his FBW would climb in case of massive overspeed and I hope we all agree that this is undesirable. Another one because he wants thrust levers only halfway back due to its engines unusual long spool-up time.
In both cases I raise the ominous “Gretchenfrage”, the core question:
Why does the manufacturor not cure the sickness and simply fights the symptom? I say:
Get the FBW or EEC logic right before you suggest manoevers that put us in a worse situation to counteract the flaw!
That is what I mean by not unconditionally trusting manufacturers, FCOM/QRH and SOPs. They have an agenda that is called profit. I have one that is called survival, in the economical and physical sense.
They do not always match!
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Originally Posted by Gretchenfrage
Aerodynamically it makes basically no sense at high altitude to destroy something we are normally struggling for, namely lift.
(...)
So why would any manufacturer want lift destruction to counteract high speed??
One of them because his FBW would climb in case of massive overspeed and I hope we all agree that this is undesirable.
(...)
So why would any manufacturer want lift destruction to counteract high speed??
One of them because his FBW would climb in case of massive overspeed and I hope we all agree that this is undesirable.
AFAIK the recommendation to use speed brake has no relation to the functioning of the overspeed protection feature.
Another one because he wants thrust levers only halfway back due to its engines unusual long spool-up time.
(...)
Why does the manufacturor not cure the sickness and simply fights the symptom? I say:
Get the FBW or EEC logic right before you suggest manoevers that put us in a worse situation to counteract the flaw!
(...)
Why does the manufacturor not cure the sickness and simply fights the symptom? I say:
Get the FBW or EEC logic right before you suggest manoevers that put us in a worse situation to counteract the flaw!
Last edited by Gysbreght; 27th May 2014 at 10:54.
@vilas
The manufacturer has to cover liabilities, and keeps that in mind when writing procedures.
Certain things they just drag their heels on. Denying issues at first, and then when presented with irrefutable facts, just say "this will be sorted in a future release".
We have had issues that took years for them to sort, still one outstanding A/THR issue thats been known for 5 yrs plus that they just get on to.......
The manufacturer has to cover liabilities, and keeps that in mind when writing procedures.
Certain things they just drag their heels on. Denying issues at first, and then when presented with irrefutable facts, just say "this will be sorted in a future release".
We have had issues that took years for them to sort, still one outstanding A/THR issue thats been known for 5 yrs plus that they just get on to.......
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Gysbreght
I sincerely hope you are not a commercial pilot transporting SLF in "thin air"!
At least your statement made me stop reading your contribution any further .....
Aerodynamically speedbrake extension creates drag to slow down the airplane. There is no lift destruction
At least your statement made me stop reading your contribution any further .....
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Gretchenfrage @OSCAR YANKEE
Since you went back to the original thread if you read the posts you will realise that those are not all from Airbus pilots. It is a mix bag neither all are of them are from their own experience either. Somebody says good idea somebody say bad idea another says it's settled. I quoted A320 official document and before it went in there Airbus gave elaborate presentation about the issue. I don't think anybody carefully read what it say. It just says to leave everything as it is and select lower speed. This what busav8r, Oscar Yankee said and you support it and yet you disagree because Airbus procedure says same thing. Your opposition is perhaps to use of speed brake. That comes when things have gotten worse and recovery procedure is required. We are faceless entities can say anything to each other doesn't prove a thing so don't so condescendingly include yourself in a threatened specie no grant would be forthcoming for your conservation.
Since you went back to the original thread if you read the posts you will realise that those are not all from Airbus pilots. It is a mix bag neither all are of them are from their own experience either. Somebody says good idea somebody say bad idea another says it's settled. I quoted A320 official document and before it went in there Airbus gave elaborate presentation about the issue. I don't think anybody carefully read what it say. It just says to leave everything as it is and select lower speed. This what busav8r, Oscar Yankee said and you support it and yet you disagree because Airbus procedure says same thing. Your opposition is perhaps to use of speed brake. That comes when things have gotten worse and recovery procedure is required. We are faceless entities can say anything to each other doesn't prove a thing so don't so condescendingly include yourself in a threatened specie no grant would be forthcoming for your conservation.
Last edited by vilas; 27th May 2014 at 15:09.
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Since you went back to the original thread if you read the posts you will realise that those are not all from Airbus pilots. It is a mix bag neither all are of them are from their own experience either. Somebody says good idea somebody say bad idea another says it's settled. I quoted A320 official document and before it went in there Airbus gave elaborate presentation about the issue. I don't think anybody carefully read what it say. It just says to leave everything as it is and select lower speed. This what busav8r, Oscar Yankee said and you support it and yet you disagree because Airbus procedure says same thing. Your opposition is perhaps to use of speed brake. That comes when things have gotten worse and recovery procedure is required. We are faceless entities can say anything to each other doesn't prove a thing so don't so condescendingly include yourself in a threatened specie no grant would be forthcoming for your conservation.
no need to get personal ...
I might have gotten a little personal if i read complete nonsense, sorry for that, but it is after all a pp forum..
Pretending that speedbrakes do not destroy lift is such nonsense. Why on earth would the red/black tape jump up when you deploy them, if not for loss of lift and by the way, we call these devices spoiler as well. They spoil what exactly?
vilas
Condescending or not, its the recipient who decides. Anyway, it is by far not only an Airbus matter, some experienced contributors here include Boeing as well, as their speedbrake logic is not beyond doubt, especially for such manoevers we discuss. But keep on adopting everything that is in the books, that makes you just the same faceless entity and no grant would be forthcoming for anyone who religiously follows sop into an incident, believe me.
Never stop expecting the unexpected
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OSKAR YANKEE
Thanks for the article. The action of the pilot in this are in between what you said in post 91 and mine 46 and 51.You wanted to just observe till things sort themselves out and AB procedure said keeping AP and ATHR on just reduce speed and speed brakes as required. He did this but it was his judgment at that point that it wasn't working and he disconnected all automation and that complicated it further. I cannot question his judgment but I think having followed the recommended procedure he could have waited to see the results before disconnecting the AP because it appears that the speed trend and not actual speed triggered further actions. But if selecting lower speed and speed brakes were not enough then doing absolutely nothing and leaving things as they are may have been worse.
Thanks for the article. The action of the pilot in this are in between what you said in post 91 and mine 46 and 51.You wanted to just observe till things sort themselves out and AB procedure said keeping AP and ATHR on just reduce speed and speed brakes as required. He did this but it was his judgment at that point that it wasn't working and he disconnected all automation and that complicated it further. I cannot question his judgment but I think having followed the recommended procedure he could have waited to see the results before disconnecting the AP because it appears that the speed trend and not actual speed triggered further actions. But if selecting lower speed and speed brakes were not enough then doing absolutely nothing and leaving things as they are may have been worse.
The only thing to do in this scenario (high rate of climb at high alt, and increasing speed) -which an experienced airbus pilot will tell you - is to press VS0, and select a lower speed eg. .76.
This will arrest the climb and level off the A/C. (You might have to press VS0 a few times, if the a/c is already in ALT* (or ALT aquire in Boeing lingo.)
Then when the a/c has regained its composure you select V/S climb with a low rate eg. 500 fpm and monitor it closely as it creeps up to level.
(The rate of course depends of the weight and thrust rating of the A/C).
This way you avoid the drama of a high workload situation involving speed brakes, closure of thrust levers etc.
As a note. These comments are not intended to put down the individual involved in the situation.
He/she found himself in an unfamiliar situation that developed rapidly, and tried to cope as best as possible.
The rest of us can take note and learn....
This will arrest the climb and level off the A/C. (You might have to press VS0 a few times, if the a/c is already in ALT* (or ALT aquire in Boeing lingo.)
Then when the a/c has regained its composure you select V/S climb with a low rate eg. 500 fpm and monitor it closely as it creeps up to level.
(The rate of course depends of the weight and thrust rating of the A/C).
This way you avoid the drama of a high workload situation involving speed brakes, closure of thrust levers etc.
As a note. These comments are not intended to put down the individual involved in the situation.
He/she found himself in an unfamiliar situation that developed rapidly, and tried to cope as best as possible.
The rest of us can take note and learn....
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OSCAR
Let's examine your suggestion. The aircraft was in ALTCRZ in which it is linked to Altitude in Alt window and when disturbed from it will try to get back to it by climbing or descending while VS0 is not linked to any altitude but V/S zero. If disturbed by updraft as was the case AC will deviate and try to maintain VS0 where ever it stabilises. So it is less aggressive. But in the present situation when the ALT mode is unable to prevent climb or descend changing to VS mode will cause larger deviations. Yes it may give you better ride because it accepts deviations. I don't see any magic solution in VS0. The pilot applied the correct procedure but may be he could have left the AP on till it disconnected on its own. It may have handled it better but not VS0.
Let's examine your suggestion. The aircraft was in ALTCRZ in which it is linked to Altitude in Alt window and when disturbed from it will try to get back to it by climbing or descending while VS0 is not linked to any altitude but V/S zero. If disturbed by updraft as was the case AC will deviate and try to maintain VS0 where ever it stabilises. So it is less aggressive. But in the present situation when the ALT mode is unable to prevent climb or descend changing to VS mode will cause larger deviations. Yes it may give you better ride because it accepts deviations. I don't see any magic solution in VS0. The pilot applied the correct procedure but may be he could have left the AP on till it disconnected on its own. It may have handled it better but not VS0.
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Villas
If you read the article, the aircraft was in OPEN CLIMB.
"The aircraft climbed through FL373 when the first officer noticed the speed had increased to 0.81 mach and had engaged in a 3000 fpm climb, the speed trend indicator suggesting the aircraft would accelerate beyond the maximum mach number operating (MMO) of 0.82 mach."
In open climb, the aircraft attempts to maintain speed by adjusting pitch to change the V/S. 3,000 fpm with only 700 feet to go is excessive. Pushing V/S zero will change the auto thrust to speed control. Once the aircraft is under control again, a gentle climb rate of say 500 fpm using V/S would be sensible.
Why do you not like using V/S 0?
The aircraft was in ALTCRZ in which it is linked to Altitude in Alt window and when disturbed from it will try to get back to it by climbing or descending while VS0 is not linked to any altitude but V/S zero.
"The aircraft climbed through FL373 when the first officer noticed the speed had increased to 0.81 mach and had engaged in a 3000 fpm climb, the speed trend indicator suggesting the aircraft would accelerate beyond the maximum mach number operating (MMO) of 0.82 mach."
In open climb, the aircraft attempts to maintain speed by adjusting pitch to change the V/S. 3,000 fpm with only 700 feet to go is excessive. Pushing V/S zero will change the auto thrust to speed control. Once the aircraft is under control again, a gentle climb rate of say 500 fpm using V/S would be sensible.
Why do you not like using V/S 0?
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Goldenrivett
The initial part of the news seemed to suggest aircraft was at ALT. However you are right the AC was in OP CLB. My comments were for ALT mode. I don't have anything against VS0 mode rather in RVSM I thought everybody uses it in last few thousand feet to reduce ROC to avoid nuisance TA/RA. Just to recap the event the AC was climbing through FL373 to FL380 when he noticed the speed .81M and ROC 3000 and went to select Mach of .76. It is not clear if ALT* was engaged. If it was not the ROC would further increase to bring the speed back. Anyway with only 700 feet to go the SPEED ALT* should have engaged. At this point he disconnected the ATHR by bringing it to idle and also applied speed brakes. So by now he had done everything that should have been done. By selecting VS0 nothing more would have been achieved because the thrust was idle and FG in ALT capture mode. If the AP was kept engaged the problem should have settled. The workload increase was due to AP disconnection. If speed brake was in full position with AP ON the disconnection of the AP could cause the speed brakes to extend full from half. This would increase the VLS and the drag leading to alpha floor.
The initial part of the news seemed to suggest aircraft was at ALT. However you are right the AC was in OP CLB. My comments were for ALT mode. I don't have anything against VS0 mode rather in RVSM I thought everybody uses it in last few thousand feet to reduce ROC to avoid nuisance TA/RA. Just to recap the event the AC was climbing through FL373 to FL380 when he noticed the speed .81M and ROC 3000 and went to select Mach of .76. It is not clear if ALT* was engaged. If it was not the ROC would further increase to bring the speed back. Anyway with only 700 feet to go the SPEED ALT* should have engaged. At this point he disconnected the ATHR by bringing it to idle and also applied speed brakes. So by now he had done everything that should have been done. By selecting VS0 nothing more would have been achieved because the thrust was idle and FG in ALT capture mode. If the AP was kept engaged the problem should have settled. The workload increase was due to AP disconnection. If speed brake was in full position with AP ON the disconnection of the AP could cause the speed brakes to extend full from half. This would increase the VLS and the drag leading to alpha floor.
Last edited by vilas; 20th Jun 2014 at 05:33.
@vilas.
You're not paying attention mate.
Does not matter whether a/c was in ALT* or not, by hitting VS0, you "break" the ALT* mode.
(Hence my comment "that you might have to press VS0 a few times because it will inevitably go into ALT* again with 3000ft/min ROC and 700' to go.)
No need for speed brake, or A/THR disconnection, if you just go VS0 and select speed .76.
And as for the comments of reducing ROC before level off, it is only rarely necessary above FL350,
and I think you will struggle to find any operator recommending the routine use of V/S mode at those levels irrespective of aircraft type....
You're not paying attention mate.
Does not matter whether a/c was in ALT* or not, by hitting VS0, you "break" the ALT* mode.
(Hence my comment "that you might have to press VS0 a few times because it will inevitably go into ALT* again with 3000ft/min ROC and 700' to go.)
No need for speed brake, or A/THR disconnection, if you just go VS0 and select speed .76.
And as for the comments of reducing ROC before level off, it is only rarely necessary above FL350,
and I think you will struggle to find any operator recommending the routine use of V/S mode at those levels irrespective of aircraft type....
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Hi OSCAR YANKEE
SKYbrary - Rate of climb within last 1000 ft before cleared level
"many operators have standard operating procedures requiring the pilots to reduce rate of climb/descent to less than 1500 ft/min when in RVSM airspace or within the last 1000 ft before cleared level;"
You'll be one of those giving me the heart attack as I wonder if you'll ever level off approaching me! The automatics always do stupid things - they can't think, so please reduce your rate of closure.
I think you will struggle to find any operator recommending the routine use of V/S mode at those levels irrespective of aircraft type....
"many operators have standard operating procedures requiring the pilots to reduce rate of climb/descent to less than 1500 ft/min when in RVSM airspace or within the last 1000 ft before cleared level;"
You'll be one of those giving me the heart attack as I wonder if you'll ever level off approaching me! The automatics always do stupid things - they can't think, so please reduce your rate of closure.
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OSCAR YANKEE
Oscar I am paying full attention. ALT* surely matters because ATHR would go to speed mode and in this situation it should go idle. He had already selected .76M and without ALT* that would have only increased the ROC to reduce speed. Coming to your point why do you want VS0 is to get ATHR in speed mode to bring the speed back and stop climb but when the guy has brought the thrust to idle with speed brakes and still the aircraft tends to over speed how VS0 would have helped? However had he left the AP on aircraft should have levelled out and he would have had more time to pay attention to adjust thrust manually or put it in auto. He followed the correct procedure except that there was no need to disconnect AP because had the over speed continued the AP would have tripped by HSP activation and then in any case you take over manually but at least give it a chance.
Oscar I am paying full attention. ALT* surely matters because ATHR would go to speed mode and in this situation it should go idle. He had already selected .76M and without ALT* that would have only increased the ROC to reduce speed. Coming to your point why do you want VS0 is to get ATHR in speed mode to bring the speed back and stop climb but when the guy has brought the thrust to idle with speed brakes and still the aircraft tends to over speed how VS0 would have helped? However had he left the AP on aircraft should have levelled out and he would have had more time to pay attention to adjust thrust manually or put it in auto. He followed the correct procedure except that there was no need to disconnect AP because had the over speed continued the AP would have tripped by HSP activation and then in any case you take over manually but at least give it a chance.
You'll be one of those giving me the heart attack as I wonder if you'll ever level off approaching me! The automatics always do stupid things - they can't think, so please reduce your rate of closure.
I wrote:
And as for the comments of reducing ROC before level off, it is only rarely necessary above FL350,
and I think you will struggle to find any operator recommending the routine use of V/S mode at those levels irrespective of aircraft type....
and I think you will struggle to find any operator recommending the routine use of V/S mode at those levels irrespective of aircraft type....
Maybe the A/C I have flown have been underpowered, I dont know.......
As the example above - high ROC above FL350, will "normally" only happen in empty A/C or if you get a WS type scenario.
@Vilas.
All im trying to say is no A/C can defy the laws of physics, no matter how advanced the A/P. Sometimes it needs a bit of help.....
And as I said in my first post.
I have had the good fortune of reading quite a few safety reports (incl. FDR read outs) similar to the one above from Avherald - and my personal opinion remains - you are better off leaving the A/THR + A/P in and take a minor overspeed, than ending up in the mess as described above.
Follow the official procedure, and you might end up one day with the "Successfull operation - but the patient died"-scenario......