Which brands have GS mini function ?
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I will try to explain my reasoning.
Trimming is of course required owing to the lift equation, where changes in air speed results in changes of lift, and which therefore require changes in the THS or elevators to maintain level flight. Since the very beginning, this has always bugged me - as an engineer - as to why pitch trimming had not been designed-out. Along came Airbus, and they did just that - brilliant !
Trimming is of course required owing to the lift equation, where changes in air speed results in changes of lift, and which therefore require changes in the THS or elevators to maintain level flight. Since the very beginning, this has always bugged me - as an engineer - as to why pitch trimming had not been designed-out. Along came Airbus, and they did just that - brilliant !
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I think the discussion is not taking all factors in consideration together. GSmini is Airbus way of handling change/variation of wind speed on approach. It deals with real time gust. It requires two things, activation to approach phase and managed speed. First is always done. Second has a possibility of going select speed but without GSmini. Now let's say you were flying a Boeing or A310 VLS 135kt and surface wind 20kt gusting to 30kt. So you will be flying Vapp of 155kts(10+10). You can' only accept speed restriction to fly beyond 155kts. It doesn't deal with actual gust on approach but at surface. So if you don't want to use GS mini then 155kts is minimum you can fly and not below. With the non Airbus way you could be flying the high Vapp correction even without aircraft facing that gust aloft. If at threshold the gust is not there then touchdown will be at higher speed because gust correction needs to be maintained. While GSmini will try to reduce the speed to Vapp on it's own. Yes! Conventional method is still used but can not be considered smarter. GSmini is new realistic way of dealing with actual winds faced all the way down. Since Neos deceleration is less so they only use 33% of wind experienced to arrive at the threshold at lesser speed.
My apologies for not being aware of the K factor for GS Mini, (= 1 for A320 classic and A330, that I fly, but only 0.33 for the Neo). I am now
Hi, 172: I am sure that you will love the Airbus FBW ! At least, I hope you will. I went onto it from BAe 146, and took to it like a duck to water. After about 12 years, I flew the B737 Classic for a year, and - sorry, no offence - but I hated it compared to the Airbus, ! (I found the B737 easy to fly, although I found its automation a bit patchy and random)
Apart from the table (!), the Airbus FBW has an unobstructed view of the instruments, and everything, including the overhead panel, is much more logically laid out, just to mention a couple of advantages.
FWIW; it took a while to get through my skull that the Airbus FBW will "stay where you put it", i.e. after you return the side-stick to neutral, it holds the last attitude you commanded, (within reason, certain rules, and weather allowing - and without any trimming by you. It is fantastic ! ). When I realised this, I stopped over-controlling and my manual flying improved a lot.
Hi, 172: I am sure that you will love the Airbus FBW ! At least, I hope you will. I went onto it from BAe 146, and took to it like a duck to water. After about 12 years, I flew the B737 Classic for a year, and - sorry, no offence - but I hated it compared to the Airbus, ! (I found the B737 easy to fly, although I found its automation a bit patchy and random)
Apart from the table (!), the Airbus FBW has an unobstructed view of the instruments, and everything, including the overhead panel, is much more logically laid out, just to mention a couple of advantages.
FWIW; it took a while to get through my skull that the Airbus FBW will "stay where you put it", i.e. after you return the side-stick to neutral, it holds the last attitude you commanded, (within reason, certain rules, and weather allowing - and without any trimming by you. It is fantastic ! ). When I realised this, I stopped over-controlling and my manual flying improved a lot.
Last edited by Uplinker; 11th Aug 2023 at 14:02.
GS mini is not for gusts. It does what the name says: ground speed minimal. Simplified: It takes your current headwind component, checks it against the head wind component for the runway based on the wind on the perf page, and adds the difference to Vapp. If the difference is negative, it doesn't subtract, to not go below Vapp. This will keep your ground speed and kinetic energy relatively constant.
Suppose the ground winds are calm, the headwind on the approach is 30kts until 200', Final approach speed is 140kts. In product B, you would be flying 140kts IAS, and have 110kts GS. Passing 200' you would still have 110 kts GS, and your airspeed would be decreasing towards 80kts IAS, with a huge power increase required. Not a good situation, so Airbus decided to introduce GS mini. Difference between headwinds aloft on the approach and on the ground is 30kts, Vapp is 140 kts, so bug at 170 kts (yeah, on the 320, can be pretty close to 177, I have seen that). As you pass through the change in wind, GS stays 140, the IAS changes from 170 to 140, no huge power increase required, and everything is great.
Is it perfect? No, but is a lot better than not having it. The higher approach speed means higher power, and as you enter the shift to less headwind that can lead to the speed increasing before the AT reacts, so probably less than 100% HC would be enough.......
Suppose the ground winds are calm, the headwind on the approach is 30kts until 200', Final approach speed is 140kts. In product B, you would be flying 140kts IAS, and have 110kts GS. Passing 200' you would still have 110 kts GS, and your airspeed would be decreasing towards 80kts IAS, with a huge power increase required. Not a good situation, so Airbus decided to introduce GS mini. Difference between headwinds aloft on the approach and on the ground is 30kts, Vapp is 140 kts, so bug at 170 kts (yeah, on the 320, can be pretty close to 177, I have seen that). As you pass through the change in wind, GS stays 140, the IAS changes from 170 to 140, no huge power increase required, and everything is great.
Is it perfect? No, but is a lot better than not having it. The higher approach speed means higher power, and as you enter the shift to less headwind that can lead to the speed increasing before the AT reacts, so probably less than 100% HC would be enough.......
I will try to explain my reasoning.
Firstly, my flying CV includes single and multi engine piston; Manual very basic turbo-props. Semi-automatic turbo-props, basic manual jets, semi-automatic Jets, and Airbus FBW.
Trimming is of course required owing to the lift equation, where changes in air speed results in changes of lift, and which therefore require changes in the THS or elevators to maintain level flight. Since the very beginning, this has always bugged me - as an engineer - as to why pitch trimming had not been designed-out. Along came Airbus, and they did just that - brilliant !
It is obvious to me that Airbus in their early days must have purchased a B737 and flown and evaluated it. After extensive flight testing, they must have said, "this is very good, but with modern technology and electronics, we can improve it further" which they did.
Many 'conventional' pilots in my experience, do not understand the Airbus FBW, and some pilots have difficulty with the FBW - hence some horrendous crashes. I have witnessed pilots in the other seat shouting "don't fight me", when the FBW was actually assisting them, if they would only relax and let it help them. I have had to explain - with diagrams - to former Boeing pilots how the Airbus GS Mini system works, (opposite to the Boeing system).
Firstly, my flying CV includes single and multi engine piston; Manual very basic turbo-props. Semi-automatic turbo-props, basic manual jets, semi-automatic Jets, and Airbus FBW.
Trimming is of course required owing to the lift equation, where changes in air speed results in changes of lift, and which therefore require changes in the THS or elevators to maintain level flight. Since the very beginning, this has always bugged me - as an engineer - as to why pitch trimming had not been designed-out. Along came Airbus, and they did just that - brilliant !
It is obvious to me that Airbus in their early days must have purchased a B737 and flown and evaluated it. After extensive flight testing, they must have said, "this is very good, but with modern technology and electronics, we can improve it further" which they did.
Many 'conventional' pilots in my experience, do not understand the Airbus FBW, and some pilots have difficulty with the FBW - hence some horrendous crashes. I have witnessed pilots in the other seat shouting "don't fight me", when the FBW was actually assisting them, if they would only relax and let it help them. I have had to explain - with diagrams - to former Boeing pilots how the Airbus GS Mini system works, (opposite to the Boeing system).
With the rudder they could have taken the same approach as with the THS: after a consistent input of the pilot, start to trim it out.
With the THS, after I put in the M/B data in the FMS, it could set the THS for me (It resets to 0 automatically after landing after all).
I am not saying they were wrong, I just haven't found the answer to why...
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Finally..
GS mini is not for gusts. It does what the name says: ground speed minimal. Simplified: It takes your current headwind component, checks it against the head wind component for the runway based on the wind on the perf page, and adds the difference to Vapp. If the difference is negative, it doesn't subtract, to not go below Vapp. This will keep your ground speed and kinetic energy relatively constant.
Suppose the ground winds are calm, the headwind on the approach is 30kts until 200', Final approach speed is 140kts. In product B, you would be flying 140kts IAS, and have 110kts GS. Passing 200' you would still have 110 kts GS, and your airspeed would be decreasing towards 80kts IAS, with a huge power increase required. Not a good situation, so Airbus decided to introduce GS mini. Difference between headwinds aloft on the approach and on the ground is 30kts, Vapp is 140 kts, so bug at 170 kts (yeah, on the 320, can be pretty close to 177, I have seen that). As you pass through the change in wind, GS stays 140, the IAS changes from 170 to 140, no huge power increase required, and everything is great.
Is it perfect? No, but is a lot better than not having it. The higher approach speed means higher power, and as you enter the shift to less headwind that can lead to the speed increasing before the AT reacts, so probably less than 100% HC would be enough.......
Suppose the ground winds are calm, the headwind on the approach is 30kts until 200', Final approach speed is 140kts. In product B, you would be flying 140kts IAS, and have 110kts GS. Passing 200' you would still have 110 kts GS, and your airspeed would be decreasing towards 80kts IAS, with a huge power increase required. Not a good situation, so Airbus decided to introduce GS mini. Difference between headwinds aloft on the approach and on the ground is 30kts, Vapp is 140 kts, so bug at 170 kts (yeah, on the 320, can be pretty close to 177, I have seen that). As you pass through the change in wind, GS stays 140, the IAS changes from 170 to 140, no huge power increase required, and everything is great.
Is it perfect? No, but is a lot better than not having it. The higher approach speed means higher power, and as you enter the shift to less headwind that can lead to the speed increasing before the AT reacts, so probably less than 100% HC would be enough.......
nothing to do with transient gusts.
My copy of 'Airbus Industrie A320 Family Instructor support' 2001 states on page 68:
(all punctuation and bold is Airbus').
Then there follows an explanitory diagram, and the text below that states:
And finally a diagram showing the PFD speed scale annotated with:
(Airbus' bold again, but all quotes hand typed by me)
The GS mini guidance has 3 major benefits:
1. It allows an efficient management of the thrust in gusts or longitudinal shears. Thrust varies in the right sense but in a smaller range(+/- 15% N1) in gusty situations which explains why it is recommended in such situations.
2. It provides additional but rational safety margins in shears.
3. It allows pilots "to understand what is going on" in perturbed approaches by monitoring the target speed magenta bugs: when it goes up = head wind gust.
1. It allows an efficient management of the thrust in gusts or longitudinal shears. Thrust varies in the right sense but in a smaller range(+/- 15% N1) in gusty situations which explains why it is recommended in such situations.
2. It provides additional but rational safety margins in shears.
3. It allows pilots "to understand what is going on" in perturbed approaches by monitoring the target speed magenta bugs: when it goes up = head wind gust.
Then there follows an explanitory diagram, and the text below that states:
........We can notice that in between a) and b) we have a front [20 kt] gust. We shall see on the PFD speed scale the target speed going up from 137 kts to 157 kts, while simultaneously the speed trend arrow and the IAS will go up for obvious aerodynamic consequences; the thrust will increase, but not excessively because of the speed trend already experienced.
Head wind gust
IAS and speed trend arrow go up, target speed goes up and N1 smoothly increases
IAS and speed trend arrow go up, target speed goes up and N1 smoothly increases
I would post a photo of the page, but I don't think that would be allowed for copyright reasons?
Thread Starter
What baffles me is the decision to not have any aileron trim, rudder trim in manual flight only, and pitch trim setting required to do manual before take off, but not used in flight (emergencies excluded).
With the rudder they could have taken the same approach as with the THS: after a consistent input of the pilot, start to trim it out.
With the THS, after I put in the M/B data in the FMS, it could set the THS for me (It resets to 0 automatically after landing after all).
I am not saying they were wrong, I just haven't found the answer to why...
With the rudder they could have taken the same approach as with the THS: after a consistent input of the pilot, start to trim it out.
With the THS, after I put in the M/B data in the FMS, it could set the THS for me (It resets to 0 automatically after landing after all).
I am not saying they were wrong, I just haven't found the answer to why...
Which only shows that the same idea on the longitudinal axis is debatable to say the least.
Could you clarify what part of what I posted would be bad. Because that is exactly what both boeing and airbus do currently. And I have flown with aircraft that do that in the longitudinal axis.
Last edited by hans brinker; 12th Aug 2023 at 20:10.
My copy of 'Airbus Industrie A320 Family Instructor support' 2001 states on page 68:
Quote:
The GS mini guidance has 3 major benefits:
1. It allows an efficient management of the thrust in gusts or longitudinal shears. Thrust varies in the right sense but in a smaller range(+/- 15% N1) in gusty situations which explains why it is recommended in such situations.
2. It provides additional but rational safety margins in shears.
3. It allows pilots "to understand what is going on" in perturbed approaches by monitoring the target speed magenta bugs: when it goes up = head wind gust.
(all punctuation and bold is Airbus').
Then there follows an explanitory diagram, and the text below that states:
Quote:
........We can notice that in between a) and b) we have a front [20 kt] gust. We shall see on the PFD speed scale the target speed going up from 137 kts to 157 kts, while simultaneously the speed trend arrow and the IAS will go up for obvious aerodynamic consequences; the thrust will increase, but not excessively because of the speed trend already experienced.
And finally a diagram showing the PFD speed scale annotated with:
Quote:
Head wind gust
IAS and speed trend arrow go up, target speed goes up and N1 smoothly increases
(Airbus' bold again, but all quotes hand typed by me)
Quote:
The GS mini guidance has 3 major benefits:
1. It allows an efficient management of the thrust in gusts or longitudinal shears. Thrust varies in the right sense but in a smaller range(+/- 15% N1) in gusty situations which explains why it is recommended in such situations.
2. It provides additional but rational safety margins in shears.
3. It allows pilots "to understand what is going on" in perturbed approaches by monitoring the target speed magenta bugs: when it goes up = head wind gust.
(all punctuation and bold is Airbus').
Then there follows an explanitory diagram, and the text below that states:
Quote:
........We can notice that in between a) and b) we have a front [20 kt] gust. We shall see on the PFD speed scale the target speed going up from 137 kts to 157 kts, while simultaneously the speed trend arrow and the IAS will go up for obvious aerodynamic consequences; the thrust will increase, but not excessively because of the speed trend already experienced.
And finally a diagram showing the PFD speed scale annotated with:
Quote:
Head wind gust
IAS and speed trend arrow go up, target speed goes up and N1 smoothly increases
(Airbus' bold again, but all quotes hand typed by me)
And that doesn't really contradict what I said/meant. I was talking about GSmini not being designed for gusts conditions in the flare. Your manual is talking about gusts and shears encountered while on the approach, the same position as I was talking about when I said headwind component while on the approach.
Thread Starter
So why would that be a bad idea? And why isn't it a bad idea to do the exact same thing with elevator trim?
I guess you think in case of an engine failure people use the rudder input to see what engine failed. But there have been plenty of engine failures where the pilots shut down the wrong engine. And the pilot not flying should always confirm what engine is failed. Guess what he uses....
The Cessna CJ uses bleed differential to add rudder bias for an engine failure, so when you have an engine failure you step deeper into the pedal on the working engine side. Takes 10 minutes in the SIM to get used to, and same to get unused to.
I guess you think in case of an engine failure people use the rudder input to see what engine failed. But there have been plenty of engine failures where the pilots shut down the wrong engine. And the pilot not flying should always confirm what engine is failed. Guess what he uses....
The Cessna CJ uses bleed differential to add rudder bias for an engine failure, so when you have an engine failure you step deeper into the pedal on the working engine side. Takes 10 minutes in the SIM to get used to, and same to get unused to.
Last edited by hans brinker; 13th Aug 2023 at 16:34.
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What baffles me is the decision to not have any aileron trim, rudder trim in manual flight only, and pitch trim setting required to do manual before take off, but not used in flight (emergencies excluded).
With the rudder they could have taken the same approach as with the THS: after a consistent input of the pilot, start to trim it out.
With the THS, after I put in the M/B data in the FMS, it could set the THS for me (It resets to 0 automatically after landing after all).
I am not saying they were wrong, I just haven't found the answer to why...
With the rudder they could have taken the same approach as with the THS: after a consistent input of the pilot, start to trim it out.
With the THS, after I put in the M/B data in the FMS, it could set the THS for me (It resets to 0 automatically after landing after all).
I am not saying they were wrong, I just haven't found the answer to why...
Why would you need aileron trim? Why would you need the rudder trim with AP ON?
As for the engine failure, the PM will announce “Engine Failure” without specifying the engine; this in order not to confuse the PF and induce errors. The good old “kick the ball” always works, the “ball” is blue and is called the Beta Target. That’s all you need really.
Airbus Industrie:
The GS mini guidance has 3 major benefits:
1. It allows an efficient management of the thrust in gusts or longitudinal shears. Thrust varies in the right sense but in a smaller range(+/- 15% N1) in gusty situations which explains why it is recommended in such situations.........
The GS mini guidance has 3 major benefits:
1. It allows an efficient management of the thrust in gusts or longitudinal shears. Thrust varies in the right sense but in a smaller range(+/- 15% N1) in gusty situations which explains why it is recommended in such situations.........
(my bold this time).
I am not really having a go; just couldn't resist
I have never really understood the desire to retain manual trimming. If it can be designed-out, why would you still want to trim manually?
It is like if motorists said they wanted to keep manual chokes, rather than have the car engine management control unit do it automatically. Or preferring the early gas turbine engines without ECUs or FADECS, which needed a flight engineer to look after them.
I flew many manually trimmed aircraft before Airbus FBW, (and flew them well enough, though I say so myself), but the Airbus auto-trim was a revelation. It just stays in the attitude you put it, (within certain limitations and caveats). Brilliant.
I cannot remember where I got my copy of The A320 Instructor Support manual. Airbus Industrie, ref: UGH01041, dated 2001.
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So why would that be a bad idea? And why isn't it a bad idea to do the exact same thing with elevator trim?
I guess you think in case of an engine failure people use the rudder input to see what engine failed. But there have been plenty of engine failures where the pilots shut down the wrong engine. And the pilot not flying should always confirm what engine is failed. Guess what he uses....
The Cessna CJ uses bleed differential to add rudder bias for an engine failure, so when you have an engine failure you step deeper into the pedal on the working engine slide. Takes 10 minutes in the SIM to get used to, and same to get unused to.
I guess you think in case of an engine failure people use the rudder input to see what engine failed. But there have been plenty of engine failures where the pilots shut down the wrong engine. And the pilot not flying should always confirm what engine is failed. Guess what he uses....
The Cessna CJ uses bleed differential to add rudder bias for an engine failure, so when you have an engine failure you step deeper into the pedal on the working engine slide. Takes 10 minutes in the SIM to get used to, and same to get unused to.
Airbus doesn't have manual aileron trim because in normal law, it does it automatically (to some extent) when an engine fails
From the A330 onwards the THS is automatically set after start when all hydraulics are available.
Why would you need aileron trim? Why would you need the rudder trim with AP ON?
As for the engine failure, the PM will announce “Engine Failure” without specifying the engine; this in order not to confuse the PF and induce errors. The good old “kick the ball” always works, the “ball” is blue and is called the Beta Target. That’s all you need really.
Why would you need aileron trim? Why would you need the rudder trim with AP ON?
As for the engine failure, the PM will announce “Engine Failure” without specifying the engine; this in order not to confuse the PF and induce errors. The good old “kick the ball” always works, the “ball” is blue and is called the Beta Target. That’s all you need really.
And thank you for the A330 THS info, did not know that. Will probably appear on the 320 at some point, but could have been there from the start.
And I know the how to fly the 320, and how the Beta target works. My question is, if the plane knows exactly where the rudder should be to center the Beta target, why doesn't it set the rudder there? The whole airbus philosophy of manual flight is that if you don't touch anything nothing will happen/change. Having to stand on the rudder to go straight and manually trim the force out in normal law really contradicts that philosophy IMO. The least they should have done was to have the rudder trim the force out automatically as the pilots keeps the Beta target centered, and the real Airbus way would be that the rudder would be trimmed towards Beta target centered even without rudder input by the pilot, just like it does AP ON. It handles aileron and THS that way, both AP ON or OFF, why not the rudder? Just my opinion.
Last edited by hans brinker; 13th Aug 2023 at 16:32.
. And yes, I know why A doesn't have aileron trim, I just feel we shouldn't need rudder trim in normal law either.
I am not really having a go; just couldn't resist
I have never really understood the desire to retain manual trimming. If it can be designed-out, why would you still want to trim manually?
It is like if motorists said they wanted to keep manual chokes, rather than have the car engine management control unit do it automatically. Or preferring the early gas turbine engines without ECUs or FADECS, which needed a flight engineer to look after them.
I flew many manually trimmed aircraft before Airbus FBW, (and flew them well enough, though I say so myself), but the Airbus auto-trim was a revelation. It just stays in the attitude you put it, (within certain limitations and caveats). Brilliant.
I cannot remember where I got my copy of The A320 Instructor Support manual. Airbus Industrie, ref: UGH01041, dated 2001.
LOL on the gust reference
. Technically correct!! A320 is my 5th type, and I love the plane, just always somethings could be better....And I think I found your manual online, will definitely read it!