Which brands have GS mini function ?
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From: Having a margarita on the beach
Only half a speed-brake
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From: Commuting not home
Let's agree words such as 'I grant you' be restricted to people who had seen the real thing unfold and work live no less than 2 years ago, bare own eyes.
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From: Wanderlust
6 out of 10 last post show insufficient understanding or failing memory of what GSmini is, how it works and what it does to the plane.
(Though I did not read AerocatS2A's contribution since I learned to agree with him on avatar value.)
The rest of you, please be gentle at each other, everyone is missing a bit.
E.g., no - upon arrival of front gust it does not add thrust.
(Though I did not read AerocatS2A's contribution since I learned to agree with him on avatar value.)
The rest of you, please be gentle at each other, everyone is missing a bit.
E.g., no - upon arrival of front gust it does not add thrust.
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From: Holding at DESDI
Let me try and explain this as simply as I can. The philosophy behind GSmini has nothing to do with transient gusts. It's about maintaining an acceptable kinetic energy level (ground speed) and potential energy level (remaining thrust available) AT TOUCHDOWN.
Picture this. You're at 1000ft and you have a headwind of 65kts. Tower reported wind is just 20kts headwind. The 65kt headwind stays until you're 250ft AGL. Then in a span of a few seconds, you suddenly lose 45kts headwind and consequently your IAS too.
Now you're uncomfortably close to your stalling speed, and the engines are almost at max thrust trying to make up for the lost airspeed. You don't have the airspeed to land safely, nor do you have the thrust to carry out a safe go-around so close to the ground.
GSmini mitigates this by adding extra speed when it anticipates such a condition by measuring the difference between current wind during the approach and wind entered in the MCDU
PS If you think I'm making up such wind conditions, I'm not. It's just a regular day at UGTB or OBBI
Picture this. You're at 1000ft and you have a headwind of 65kts. Tower reported wind is just 20kts headwind. The 65kt headwind stays until you're 250ft AGL. Then in a span of a few seconds, you suddenly lose 45kts headwind and consequently your IAS too.
Now you're uncomfortably close to your stalling speed, and the engines are almost at max thrust trying to make up for the lost airspeed. You don't have the airspeed to land safely, nor do you have the thrust to carry out a safe go-around so close to the ground.
GSmini mitigates this by adding extra speed when it anticipates such a condition by measuring the difference between current wind during the approach and wind entered in the MCDU
PS If you think I'm making up such wind conditions, I'm not. It's just a regular day at UGTB or OBBI
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From: UK
Now, was there really any need for that outburst, or would a careful explanation with diagrams perhaps have been more appropriate in Tech Log - where most of us like to expand our learning?
I never claim to know everything and I admit that I only have about 8,500 hours and 14 years on Airbus FBW, so have only observed GS mini a thousand times or so. But whatever.
As for the NEO; No, obviously nothing to do with the engines, but I thought someone said it has modified GS Mini laws?
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From: Wanderlust
Neo word drags your attention to engine away from aerodynamics. Neos have Sharklets and LIP Lift Improvement Package that has improved engine strakes and better slat seals improving lift and reducing drag.This when closer to ground makes it difficult to drop the excess speed of GSmini. That's why in Neos the GSmini uses only 33% of difference in experienced wind and reported surface wind which makes it manageable to reach Vapp. Only disadvantage is autothrust activity increases.
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From: Wiltshire
Oh my word. It’s an aircraft. It has thrust and drag, weight and lift. It has flying controls. You can pitch up and down, bank left and right, and control or use yaw. You can take fully manual control of the thrust, like you did in your PA28/C152. If you do those things you have no issue with the French electric jet trying to be too clever. You’re the boss, not some programmer in 1980s Toulouse.
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From: Between a rock and a hard place
It's almost funny. The B737 FCTM has the following two sentences about the scenario discussed, that GSmini is supposed to handle:
When using the autothrottle, position command speed to VREF+5 knots. Sufficient wind and gust protection is available with the autothrottle connected because the autothrottle is designed to adjust thrust rapidly when the airspeed drops below commanded speed while reducing thrust slowly when the airspeed exceeds commanded speed. In turbulence, the result is that average thrust is higher then necessary to maintain command speed. This results in an average speed exceeding command speed.
That's it folks, Vref+5
When using the autothrottle, position command speed to VREF+5 knots. Sufficient wind and gust protection is available with the autothrottle connected because the autothrottle is designed to adjust thrust rapidly when the airspeed drops below commanded speed while reducing thrust slowly when the airspeed exceeds commanded speed. In turbulence, the result is that average thrust is higher then necessary to maintain command speed. This results in an average speed exceeding command speed.
That's it folks, Vref+5
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From: Wanderlust
It's almost funny. The B737 FCTM has the following two sentences about the scenario discussed, that GSmini is supposed to handle:
When using the autothrottle, position command speed to VREF+5 knots. Sufficient wind and gust protection is available with the autothrottle connected because the autothrottle is designed to adjust thrust rapidly when the airspeed drops below commanded speed while reducing thrust slowly when the airspeed exceeds commanded speed. In turbulence, the result is that average thrust is higher then necessary to maintain command speed. This results in an average speed exceeding command speed.
That's it folks, Vref+5
When using the autothrottle, position command speed to VREF+5 knots. Sufficient wind and gust protection is available with the autothrottle connected because the autothrottle is designed to adjust thrust rapidly when the airspeed drops below commanded speed while reducing thrust slowly when the airspeed exceeds commanded speed. In turbulence, the result is that average thrust is higher then necessary to maintain command speed. This results in an average speed exceeding command speed.
That's it folks, Vref+5
Last edited by vilas; 4th August 2023 at 10:03.
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From: Between a rock and a hard place
True, A/T off requures a bit more thinking.
Vref + 10-15 knots works pretty well too if it's windy. To be bled off whenever your gut tells you to. Usually by starting retarding when RA comes alive at 50 ft.
Vref + 10-15 knots works pretty well too if it's windy. To be bled off whenever your gut tells you to. Usually by starting retarding when RA comes alive at 50 ft.
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From: UK
Oh my word. It’s an aircraft. It has thrust and drag, weight and lift. It has flying controls. You can pitch up and down, bank left and right, and control or use yaw. You can take fully manual control of the thrust, like you did in your PA28/C152. If you do those things you have no issue with the French electric jet trying to be too clever. You’re the boss, not some programmer in 1980s Toulouse.
Those designers, engineers and test pilots in Toulouse are far, far cleverer than you or I, and they have done a fantastic job with the Airbus FBW. An order of magnitude better than Boeing, with their MCAS, for example. (And even their supposedly FBW B777 still has pitch trim pickle switches).
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From: USA
So far there's speculation over...
- if there's a reason the wind additive might be different than another manufacturer specifies
- whether good airmanship implies you can select Vapp
- design engineers being smarter than line pilots
- maybe some other things I missed
... but still no word on simply whether SOP allows for selecting Vapp. I'd have thought a matter like this would be very straightforward... pretty much yes/no with a manual reference?
As an aside,
FBW doesn't necessarily mean FBW with the control law that Airbus uses.
- if there's a reason the wind additive might be different than another manufacturer specifies
- whether good airmanship implies you can select Vapp
- design engineers being smarter than line pilots
- maybe some other things I missed
... but still no word on simply whether SOP allows for selecting Vapp. I'd have thought a matter like this would be very straightforward... pretty much yes/no with a manual reference?
As an aside,
FBW doesn't necessarily mean FBW with the control law that Airbus uses.
Last edited by Vessbot; 6th August 2023 at 20:25.
Thread Starter
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From: France
As long as there isn't anything preventing you from flying Vapp, I don't see why you would be forced to used managed speed.
My mind has now moved on to something else. The use of reversers (thrust lever management) in case of inoperative reversers (all inop)
The FCTM is very very unclear about this. I will let whoever wants to read it and be surprised (or not)
My mind has now moved on to something else. The use of reversers (thrust lever management) in case of inoperative reversers (all inop)
The FCTM is very very unclear about this. I will let whoever wants to read it and be surprised (or not)
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From: Wiltshire
See? This is exactly what worries me: People who do not understand how GS Mini works, but nevertheless think they can override it and fly more safely by ignoring it.
Those designers, engineers and test pilots in Toulouse are far, far cleverer than you or I, and they have done a fantastic job with the Airbus FBW. An order of magnitude better than Boeing, with their MCAS, for example. (And even their supposedly FBW B777 still has pitch trim pickle switches).
Those designers, engineers and test pilots in Toulouse are far, far cleverer than you or I, and they have done a fantastic job with the Airbus FBW. An order of magnitude better than Boeing, with their MCAS, for example. (And even their supposedly FBW B777 still has pitch trim pickle switches).
Joined: Mar 2012
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From: Having a margarita on the beach
As long as there isn't anything preventing you from flying Vapp, I don't see why you would be forced to used managed speed.
My mind has now moved on to something else. The use of reversers (thrust lever management) in case of inoperative reversers (all inop)
The FCTM is very very unclear about this. I will let whoever wants to read it and be surprised (or not)
My mind has now moved on to something else. The use of reversers (thrust lever management) in case of inoperative reversers (all inop)
The FCTM is very very unclear about this. I will let whoever wants to read it and be surprised (or not)
INITIAL APPROACH:
(…) MANAGED SPEED....................................................... ......................CHECK ▏ PF
If ATC requires a particular speed, use selected speed. When the ATC speed constraint no longer applies, return to managed speed.
Q2.
AT LEAST ONE REVERSER OPERATIVE
If at least one reverser is operative, the general recommendation is to select the reverser thrust on both engines during rejected takeoff (RTO) and at landing, as per normal procedures.
NO REVERSERS OPERATIVE
If no reversers are operative, the general recommendation is to not select the reverser thrust during RTO and at landing. However, the PF still sets both thrust levers to the IDLE detent, as per normal procedures.
TAM 3054 accident.
After this accident the procedure changed and so did the wording as highlighted above.
From the report:
The FDR transcript shows that immediately after the warning, the flight computer recorded the left thrust lever being retarded to the rear-most position, activating the thrust reverser on the left engine, while the right thrust lever (controlling the engine with the disabled thrust reverser) remained in the CL position.
So all Airbus is trying to tell you is: do not forget to close the thrust levers when you land. It may sound obvious to 99.9% of the pilots but as there was an accident involved, lawyers got in the way.
With both reverser inoperative if you do select IDLE REVERSE the FADEC will command an increased N1 which will adversely affect your landing distance as there will be no reverse deployment.
With 1 REV INOP, same will happen on the Inoperative reverser but the operative one will compensate and the loss in performance is negligible. That’s why you can handle your reverse as you would normally do with no failures/MEL.
p.s. Do not confuse IDLE DETENT with IDLE REVERSE.
Last edited by sonicbum; 7th August 2023 at 09:03.
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From: Between a rock and a hard place
See? This is exactly what worries me: People who do not understand how GS Mini works, but nevertheless think they can override it and fly more safely by ignoring it.
Those designers, engineers and test pilots in Toulouse are far, far cleverer than you or I, and they have done a fantastic job with the Airbus FBW. An order of magnitude better than Boeing, with their MCAS, for example. (And even their supposedly FBW B777 still has pitch trim pickle switches).
Those designers, engineers and test pilots in Toulouse are far, far cleverer than you or I, and they have done a fantastic job with the Airbus FBW. An order of magnitude better than Boeing, with their MCAS, for example. (And even their supposedly FBW B777 still has pitch trim pickle switches).
I know this thread is about GSmini, but I couldn't help myself responding to your glorification of Airbus designers and engineers. Granted, they're top line in what they're doing. Doesn't necessarily mean their system is the only way that works. I am more worried about the disconnect between pilots and the air, come future.
Thread Starter
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From: France
The FADEC will increase N1, but only for a very short time, as it will detect the reverser doors not open and go back to normal idle.
Still a bad idea to have this transient increase in thrust.
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From: UK
and in turn, THIS is what worries me, alongside the compete faith Toulouse has in their competence. Need I list all the famous FBW crashes, all the expert critique of the weaknesses designed into the HMI, all the near-misses, all the major errors with Airbus signatures at the bottom line, the famous letter saying there was no need to train FBW airliner pilots in unusual attitude recoveries, etc etc? I could go on. I know exactly how GS MINI is meant to work; I also know that unquestioning trust in technology dooms us to failure. If you need something like that to keep from crashing, you really need to be looking deeper.
I am not really sure what you're getting at here. Manual speed additives have been used for a century soon and as far as I know no aircraft has ever stalled on approach due to inappropriate speed additives? You put a lot of faith in software developers. Now I am an airline pilot, but I also develop software and work closely with developers far better than me, their mindset is very different from that of a pilot (as I know 'pilots'). In software features are added because they're <em>cool,</em> not because they're necessarily asked for or needed by the end user. Now this is my opinion, but modern planes are killing the skill of being a pilot. I am talking fundamental skills. Do modern pilots understand they need added back pressure on the yoke/stick when entering a bank? Do they understand you need to trim in the aircraft in pitch whenever speed changes?
I know this thread is about GSmini, but I couldn't help myself responding to your glorification of Airbus designers and engineers. Granted, they're top line in what they're doing. Doesn't necessarily mean their system is the only way that works. I am more worried about the disconnect between pilots and the air, come future.
I know this thread is about GSmini, but I couldn't help myself responding to your glorification of Airbus designers and engineers. Granted, they're top line in what they're doing. Doesn't necessarily mean their system is the only way that works. I am more worried about the disconnect between pilots and the air, come future.
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).
