A/T: is it really helping you ?
Joined: Feb 2003
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From: Blue sky
You don’t count on it, you use the feedback from the yoke giving you trim requirements like any normal aircraft because you would see the nose pitching down unwanted. Very natural.
But you could calculate to have an idea...
But you could calculate to have an idea...
Joined: Sep 2016
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From: USA
It's as if we're discussing how the electrical system works, and how exactly the automatic cross tie behaves if one side power is lost... and the reply is "how could you possibly consider shutting off a generator in cruise, this is dangerous and irresponsible!"
Thread Starter
Joined: Apr 2022
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From: France
A friend of mine tried the maneuver in the B777 PMDG sim (general public, how reliable is it ?)
For a sufficient difference in speed, the behavior is exactly as described on the first post.
However, if the speed reduction less than 5 knots, the airplane will trim itself !! My friend displayed the trim reference speed on the PFD, and the TRS was moving by itself !
However, for a further reduction of 5 knots, the TRS stopped moving by itself and the plane descended as described.
So, we found out that Boeing 777 can trim itself, a little bit.
For a sufficient difference in speed, the behavior is exactly as described on the first post.
However, if the speed reduction less than 5 knots, the airplane will trim itself !! My friend displayed the trim reference speed on the PFD, and the TRS was moving by itself !
However, for a further reduction of 5 knots, the TRS stopped moving by itself and the plane descended as described.
So, we found out that Boeing 777 can trim itself, a little bit.
Joined: Mar 2009
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From: USA
Eastern 401 was not an A/T issue. A/T on the Tristar was for approach only, and in this case, a low altitude radar box pattern to troubleshoot the gear not down and locked indication. The “flaw” was no aural warning when the A/P went from Alt Hold to V/S after the captain bumped the yoke while fiddling with the nose gear light. A/T maintained speed as aircraft entered slight descent into the Everglades. Many CRM issue, but it was, I believe, 1970 or ‘71.
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From: Perpetually circling OCK for some reason
Eastern 401 was not an A/T issue. A/T on the Tristar was for approach only, and in this case, a low altitude radar box pattern to troubleshoot the gear not down and locked indication. The “flaw” was no aural warning when the A/P went from Alt Hold to V/S after the captain bumped the yoke while fiddling with the nose gear light. A/T maintained speed as aircraft entered slight descent into the Everglades. Many CRM issue, but it was, I believe, 1970 or ‘71.
Thread Starter
Joined: Apr 2022
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From: France
Eastern 401 was not an A/T issue. A/T on the Tristar was for approach only, and in this case, a low altitude radar box pattern to troubleshoot the gear not down and locked indication. The “flaw” was no aural warning when the A/P went from Alt Hold to V/S after the captain bumped the yoke while fiddling with the nose gear light. A/T maintained speed as aircraft entered slight descent into the Everglades. Many CRM issue, but it was, I believe, 1970 or ‘71.
However, it would also be true to point out that without automatics engaged, and with just a slight inadvertent push of the stick, Eastern401 would have entered a "level phugoid", that is, would have started to oscillate around its original altitude. And we wouldn't be talking about them.
Automatic flight has its catches.
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From: UK
Not really sure what the OP wants to know. Flying with manual thrust IS a matter of scanning. It makes the PF job more intense, since it requires very close scanning, over and above the manual flying.
In busy airspace, such as the London TMA, or JFK approach, or chaotic ATC such as Cairo, there can be a lot going on and it is not really a place to be manually flying, unless you have no choice owing to equipment failure. Both PF and PM need to be on top of their game; listening to RT calls, other aircraft, and making sure they are complying correctly, and building an overall picture of the airspace. If PF is manually flying, half or more of their brain is taken up with that task, leaving say, 1.3 brains dealing with ATC instructions and surrounding traffic instead of 2 brains.
With a conventional aircraft; changing thrust and or speed can/will change pitch, which has to be accommodated and re-trimmed for. An aircraft with a FBW pitch channel can automatically adjust for thrust changes, compensate for the pitch-power couple, and trim. This takes away a chunk of the PF task, allowing them to use more of their brain listening to ATC, which in turn makes the whole process less intense and easier.
I am type rated for and have flown both conventional and FBW aircraft on the line for many years. The Boeing Classic 300/400 has auto-throttle but no FBW, so when flying manually with auto-throttle, PF has to constantly adjust pitch and trim inputs when the auto-throttle changes, and they constantly have to react to these changes "without causing them". This is why auto-throttle is not recommended by Boeing when flying manually.
If the aircraft does have a FBW pitch channel, auto-thrust can be compensated for and trimmed automatically, so the pitch-power couple effectively disappears, and PF can fly manually with auto-thrust active, making this a much easier task.
With the B777, even though it has FBW you, (I think), have to repeatedly push the trim pickle switches to stay in trim ?, which seems like a waste of the FBW, (it didn't work at all for me during a recent SIM test, so I must have been doing something wrong), but the Airbus FBW and auto-thrust system is very well designed, integrated and implemented.
Basically, in my hands-on experience, Airbus have done a fantastic job of designing and creating a properly integrated FBW and auto-thrust system, which works extremely well.
In busy airspace, such as the London TMA, or JFK approach, or chaotic ATC such as Cairo, there can be a lot going on and it is not really a place to be manually flying, unless you have no choice owing to equipment failure. Both PF and PM need to be on top of their game; listening to RT calls, other aircraft, and making sure they are complying correctly, and building an overall picture of the airspace. If PF is manually flying, half or more of their brain is taken up with that task, leaving say, 1.3 brains dealing with ATC instructions and surrounding traffic instead of 2 brains.
With a conventional aircraft; changing thrust and or speed can/will change pitch, which has to be accommodated and re-trimmed for. An aircraft with a FBW pitch channel can automatically adjust for thrust changes, compensate for the pitch-power couple, and trim. This takes away a chunk of the PF task, allowing them to use more of their brain listening to ATC, which in turn makes the whole process less intense and easier.
I am type rated for and have flown both conventional and FBW aircraft on the line for many years. The Boeing Classic 300/400 has auto-throttle but no FBW, so when flying manually with auto-throttle, PF has to constantly adjust pitch and trim inputs when the auto-throttle changes, and they constantly have to react to these changes "without causing them". This is why auto-throttle is not recommended by Boeing when flying manually.
If the aircraft does have a FBW pitch channel, auto-thrust can be compensated for and trimmed automatically, so the pitch-power couple effectively disappears, and PF can fly manually with auto-thrust active, making this a much easier task.
With the B777, even though it has FBW you, (I think), have to repeatedly push the trim pickle switches to stay in trim ?, which seems like a waste of the FBW, (it didn't work at all for me during a recent SIM test, so I must have been doing something wrong), but the Airbus FBW and auto-thrust system is very well designed, integrated and implemented.
Basically, in my hands-on experience, Airbus have done a fantastic job of designing and creating a properly integrated FBW and auto-thrust system, which works extremely well.
Joined: Jun 2007
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From: Wanderlust
The difference in FBW of Airbus and Boeing has commercial aspect as well. Boeing was introducing FBW for existing large customer base of 737, 767, 757. They wouldn't appreciate a new Boeing radically different. So whether stab was really trimmed by pilot or by FBW they kept the concept traditional. Airbus had no market presence. They were trying to create a new customer base so they went with different philosophy based on high level of automation with pilot mostly monitoring and over the years they have proved right.
Thread Starter
Joined: Apr 2022
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From: France
Not really sure what the OP wants to know. Flying with manual thrust IS a matter of scanning. It makes the PF job more intense, since it requires very close scanning, over and above the manual flying.
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With the B777, even though it has FBW you, (I think), have to repeatedly push the trim pickle switches to stay in trim ?, which seems like a waste of the FBW, (it didn't work at all for me during a recent SIM test, so I must have been doing something wrong), but the Airbus FBW and auto-thrust system is very well designed, integrated and implemented.
Basically, in my hands-on experience, Airbus have done a fantastic job of designing and creating a properly integrated FBW and auto-thrust system, which works extremely well.
.
With the B777, even though it has FBW you, (I think), have to repeatedly push the trim pickle switches to stay in trim ?, which seems like a waste of the FBW, (it didn't work at all for me during a recent SIM test, so I must have been doing something wrong), but the Airbus FBW and auto-thrust system is very well designed, integrated and implemented.
Basically, in my hands-on experience, Airbus have done a fantastic job of designing and creating a properly integrated FBW and auto-thrust system, which works extremely well.
If you want to follow your ILS, just know your power preset, and display it. Trim the airplane properly (that's only for boeing) Then your airplane will have a trajectory that cannot diverge quickly from the intended flight path. It just cannot.
If you have the A/T on, the airplane can diverge from the intended trajectory, for example if your nose is slightly low or high. It's easier to display a power preset to a tenth of a percent (it's displayed like so) than to display a pitch preset (the pitch indicator is more than 1° large and the scale is precise to 2.5°..) Also I noticed that, at least in the sim, the vertical speed has a half second/one second delay that can generate PIO if you try to fly the glide with vertical speed rather than pitch. Contrarily to airbus.
Flying an airbus manually requires very little scanning if you know your figures. Just display the power setting, set the proper pitch, monitor speed. You're all set. It will work the same with unstable winds. The airplane won't develop an instable behavior such as the idle descent that Boeing can do.
Also, the A/T (both of them) can fall in the "windshear trick". Reducing the thrust to idle when a headwind increases, only to find itself woefully unprepared when the windshear turns to tailwind, while thrust is at near idle.
At least, Boeing allows to see this phenomenon more easily.
Indeed, the airbus system is very well designed. Personnally, I don't see the point of having to trim an airliner. I don't see it as so major since I started real flights, because the airplane is actually much softer on the controls. The out of trim efforts are much smaller, actually very similar to that of a light aircraft, I felt.
In my opinion, the ideal system would be a small mix between airbus and boeing. Airbus laws, but with more emphasis on what trim is doing.
So, a small feedback of where the trim is by moving the neutral stick position (which boeing 777 doesn't have either), both sidesticks moving together when manually flying, and some improvements of the airbus laws regarding not allowing the airplane to use the entire trim range.
Joined: Jul 2006
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From: Somewhere over the rainbow
Even tho I agree the Airbus A/THR works very well and reduces the workload; I find the landing with A/THR off to be easier and more consistent especially in area where the wind can varies a lot in short final. But saying this, landing with A/THR still work like a charm most of the times.
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From: UK
Ever since starting to fly, I have always thought that pitch trimming for speed, and a pitch-power couple, is something that should be designed-out if it can be. It couldn't be done originally, until technology and electronics provided a solution. And Airbus did exactly that - and more - with their revolutionary FBW system, which is an order of magnitude better than what came before. (I have flown many conventional types). Not having to pitch trim manually during hand flying is an advantage to me, not a problem. And the Airbus auto-thrust most definitely does help me.
I think that pilots who have got into trouble with it have been mishandling the aircraft in some way, e.g. AF 447, or through misunderstandings of how the FBW, or the Airbus Ground Speed Mini system works; and the subsequent auto-thrust behaviour.
But I am being a bit dim and still don't really understand your criticism, CVividasku. Without being too technical, what is it that an Airbus FBW aircraft does or does not do during a gusty ILS that you don't like or gives you a problem ?
I think that pilots who have got into trouble with it have been mishandling the aircraft in some way, e.g. AF 447, or through misunderstandings of how the FBW, or the Airbus Ground Speed Mini system works; and the subsequent auto-thrust behaviour.
But I am being a bit dim and still don't really understand your criticism, CVividasku. Without being too technical, what is it that an Airbus FBW aircraft does or does not do during a gusty ILS that you don't like or gives you a problem ?
Thread Starter
Joined: Apr 2022
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From: France
Oh no, on the contrary, I like the Airbus FBW a lot.
The only thing I don't like so much is the ATHR, but not for the same reason. Like pineteam said, landing without it is easier.
Also, I like to manage the airplane energy by myself. I might want to reduce speed with a bit of power left, to slow down slower, or to be able to spool up the engines quicker.
The only thing I would change about it :
What I said above + trim indicator, and why not an emergency trim neutral button for upset recovery.
The only thing I don't like so much is the ATHR, but not for the same reason. Like pineteam said, landing without it is easier.
Also, I like to manage the airplane energy by myself. I might want to reduce speed with a bit of power left, to slow down slower, or to be able to spool up the engines quicker.
The only thing I would change about it :
What I said above + trim indicator, and why not an emergency trim neutral button for upset recovery.
Joined: Jul 2013
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From: Everett, WA
All I know is that - when we were getting ready for the first flight of the 747-8, the chief test pilot was very adamant that the autothrottle needed to be functional, or he wouldn't accept the aircraft was being ready.
Hence we spent a lot of time testing the FADEC/FMC/Autothrottle interface prior to first flight to make sure there would be no surprises...
Hence we spent a lot of time testing the FADEC/FMC/Autothrottle interface prior to first flight to make sure there would be no surprises...
Joined: Nov 1999
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From: UK
(CV), Is it the auto-thrust or actually the Ground Speed Mini rapidly changing the speed bug on turbulent finals that you don't like ?
I ask this because I have flown with pilots who think that Ground Speed Mini doesn't work or think it "gets it wrong", or they think it "is slow to react", so they prefer to take out the auto-thrust, and "do the job properly".
But G/S Mini is none of these things; they are thinking about conventional constant IAS systems, whereas G/S Mini works the opposite way round - it will increase thrust when the headwind increases.
But when going manual thrust in an Airbus FBW these pilots often do not obey the G/S Mini speed demands, and this appears to them to make the flight smoother and less hectic on turbulent days because the engines are not hosing up and down so much. But it actually reduces their safety margins, and reduces the aircraft energy, which is potentially dangerous.
I should also have mentioned earlier that the excellent Airbus auto-thrust works very well because it is so well integrated with the FBW pitch channel. And its engagement and operational logic is so much more intuitive and reliable than other older auto-throttle systems I have flown.
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I ask this because I have flown with pilots who think that Ground Speed Mini doesn't work or think it "gets it wrong", or they think it "is slow to react", so they prefer to take out the auto-thrust, and "do the job properly".
But G/S Mini is none of these things; they are thinking about conventional constant IAS systems, whereas G/S Mini works the opposite way round - it will increase thrust when the headwind increases.
But when going manual thrust in an Airbus FBW these pilots often do not obey the G/S Mini speed demands, and this appears to them to make the flight smoother and less hectic on turbulent days because the engines are not hosing up and down so much. But it actually reduces their safety margins, and reduces the aircraft energy, which is potentially dangerous.
I should also have mentioned earlier that the excellent Airbus auto-thrust works very well because it is so well integrated with the FBW pitch channel. And its engagement and operational logic is so much more intuitive and reliable than other older auto-throttle systems I have flown.
.
Last edited by Uplinker; 10th June 2024 at 09:42.
Thread Starter
Joined: Apr 2022
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From: France
I tried the maneuver described here in the FFS. I tried an out of trim condition of only 3 knots, we were at 7000 feet. In less than time than necessary to explain what I expected to see to my two colleagues (pilot and instructor), or in other words, in less than the time you just took to read this sentence, the airplane was already in a full blown idle descent.
So between a small jolt on one of the two speed references, during stable flight and idle descent, there was less than 15 seconds.
More importantly, between the first noticeable effects of the descent and the full blown descent, there was maybe only 5 seconds.
With a speed difference of only 3 knots.
With a larger out of trim condition it would be even quicker.
This may be remotely related to this incident :
https://www.flightradar24.com/blog/s...escent-hawaii/
No, I think the A/T does a pretty good job with ground speed mini, it accepts speed variations, if I remember correctly, which is what I expect of it.
What I didn't like was, in order of importance :
- Especially during flare, there was a risk that the plane would add thrust and cause a long landing if you were a tiny bit late to retard. Also, it means that you cannot really keep your power at 50% for longer if you need to (for example, on the 318, you need to)
- Not being able to control my overall energy. With the correct power setting, the overall energy of the airplane will evolve in a predictable way. With A/T on, a half degree of pitch is nearly invisible on the PFD (I'll let you guess how many milimeters that is), but cumulated over some distance will give very noticeable altitude errors.
- Not being able to keep some power if I wanted to. 40% minimum to keep a very quick reaction time if needed. Or 40% to slow down in a softer manner.
I don't recognize what you write about GS mini. Airbus is the only brand to implement it. So, other airplane manufacturers make unsafe airplanes ?
In my memory, GS mini function, on the contrary, leads to very little variation of thrust during the approach (except if the wind has extreme gusts, which I don't recall having). Because when the airspeed increases due to a wind gust, the airplane's higher drag doesn't have time to slow down the plane back to its original speed before the wind gust dies down. So in my memory, following GS mini consisted mainly in keeping the thrust constant, or almost constant.
So between a small jolt on one of the two speed references, during stable flight and idle descent, there was less than 15 seconds.
More importantly, between the first noticeable effects of the descent and the full blown descent, there was maybe only 5 seconds.
With a speed difference of only 3 knots.
With a larger out of trim condition it would be even quicker.
This may be remotely related to this incident :
https://www.flightradar24.com/blog/s...escent-hawaii/
(CV), Is it the auto-thrust or actually the Ground Speed Mini rapidly changing the speed bug on turbulent finals that you don't like ?
I ask this because I have flown with pilots who think that Ground Speed Mini doesn't work or think it "gets it wrong", or they think it "is slow to react", so they prefer to take out the auto-thrust, and "do the job properly".
But G/S Mini is none of these things; they are thinking about conventional constant IAS systems, whereas G/S Mini works the opposite way round - it will increase thrust when the headwind increases.
But when going manual thrust in an Airbus FBW these pilots often do not obey the G/S Mini speed demands, and this appears to them to make the flight smoother and less hectic on turbulent days because the engines are not hosing up and down so much. But it actually reduces their safety margins, and reduces the aircraft energy, which is potentially dangerous.
I should also have mentioned earlier that the excellent Airbus auto-thrust works very well because it is so well integrated with the FBW pitch channel. And its engagement and operational logic is so much more intuitive and reliable than other older auto-throttle systems I have flown.
.
I ask this because I have flown with pilots who think that Ground Speed Mini doesn't work or think it "gets it wrong", or they think it "is slow to react", so they prefer to take out the auto-thrust, and "do the job properly".
But G/S Mini is none of these things; they are thinking about conventional constant IAS systems, whereas G/S Mini works the opposite way round - it will increase thrust when the headwind increases.
But when going manual thrust in an Airbus FBW these pilots often do not obey the G/S Mini speed demands, and this appears to them to make the flight smoother and less hectic on turbulent days because the engines are not hosing up and down so much. But it actually reduces their safety margins, and reduces the aircraft energy, which is potentially dangerous.
I should also have mentioned earlier that the excellent Airbus auto-thrust works very well because it is so well integrated with the FBW pitch channel. And its engagement and operational logic is so much more intuitive and reliable than other older auto-throttle systems I have flown.
.
What I didn't like was, in order of importance :
- Especially during flare, there was a risk that the plane would add thrust and cause a long landing if you were a tiny bit late to retard. Also, it means that you cannot really keep your power at 50% for longer if you need to (for example, on the 318, you need to)
- Not being able to control my overall energy. With the correct power setting, the overall energy of the airplane will evolve in a predictable way. With A/T on, a half degree of pitch is nearly invisible on the PFD (I'll let you guess how many milimeters that is), but cumulated over some distance will give very noticeable altitude errors.
- Not being able to keep some power if I wanted to. 40% minimum to keep a very quick reaction time if needed. Or 40% to slow down in a softer manner.
I don't recognize what you write about GS mini. Airbus is the only brand to implement it. So, other airplane manufacturers make unsafe airplanes ?
In my memory, GS mini function, on the contrary, leads to very little variation of thrust during the approach (except if the wind has extreme gusts, which I don't recall having). Because when the airspeed increases due to a wind gust, the airplane's higher drag doesn't have time to slow down the plane back to its original speed before the wind gust dies down. So in my memory, following GS mini consisted mainly in keeping the thrust constant, or almost constant.
Last edited by CVividasku; 17th June 2024 at 23:00.
Joined: Feb 2003
Posts: 541
Likes: 336
From: Blue sky
If you have the A/T on, the airplane can diverge from the intended trajectory, for example if your nose is slightly low or high. It's easier to display a power preset to a tenth of a percent (it's displayed like so) than to display a pitch preset (the pitch indicator is more than 1° large and the scale is precise to 2.5°..) Also I noticed that, at least in the sim, the vertical speed has a half second/one second delay that can generate PIO if you try to fly the glide with vertical speed rather than pitch. Contrarily to airbus.
It is almost impossible in reality because the atmosphere is not like a simulator.
To get back to the original point: You fly data and think the world is like this sterile unchangeable data. It is not. Pilots are trained to set data as a starting point but continuously adapt to the reality which is not simulatorlike but full of little outside disturbances.
Your original question turns out to be a quest for confirmation that A/T is making our life more difficult. It is the opposite. Because reality is not a simulator using datapoints. Reality is everything from subtle to big sudden changes, where you need to have a hand on the throttle and a hand on the stick and use the feedback provided. Your ’stability problem’ is small compared to the real world disturbances but you don’t seem to understand that as you’ve never been at the controls of a calm wind ILS, let alone a gusty one. Your problem literally disappears into the wind if I may say so. With all due respect, so would your speed if you decided to disconnect the A/T because you think it is easier. The A/T does a fantastic job at it. It doesn’t even need additional wind corrections which makes life over the threshold a lot easier...
If you can’t accept that reality the solution for you is easy: wait for the first A350 that can takeoff with the autopilot and land without a single disconnect. Problem solved.
Last edited by BraceBrace; 17th June 2024 at 23:55.
Joined: Sep 2016
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From: USA
I mean yeah pilots are supposed to make corrective inputs, duh. But even with that, aircraft are still supposed to be stable, other than some super specialty application like NASA's Flying Bedstead or whatever.
Joined: Mar 2002
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From: Seat 1A
This may be remotely related to this incident :
https://www.flightradar24.com/blog/s...escent-hawaii/
https://www.flightradar24.com/blog/s...escent-hawaii/