Which brands have GS mini function ?
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Wouldn't allowing the automation to do its thing be the best in this situation? If you were in a conventional airplane, and your Vapp turned out to be Vref+20, would you fly a slower speed just for spacing?
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I would ignore managed speed in very strong headwinds when it takes me too close to the bricks. 5 knot buffer isn’t enough sometimes. I might select speed if ATC want something specific and I’m happy that the selected speed puts us comfortably in the middle of the envelope. Mostly I let GS mini do it’s thing, I think it’s great.
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Since it is expected to let GSmini do it's thing the formula for specific select speed is not given but why should it be different than say 737? Half wind+full gust that's what should be flown.
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The FMS will display Vref and Vref+5. GSmini works on top of that. SOP is to use it, and you can’t really turn it off. Think of the way your ECON speed changes as conditions change. GSmini is like flying an approach in ECON.
Just once the condition that’s making use selected speed has gone. I don’t fly to places with much ATC speed control so I’ve never had to use selected because managed was too fast, that’s a hypothetical example of when I’d use it. As for getting close to the bricks, I’ve had occasion when a strong wind at 2000’ has had GS mini giving a high speed target. In this case I’d go back to managed once out of the worst of the wind. That said, the function is there for good reason, it protects against a dramatic loss of energy when moving through shear layers, so I very rarely use selected for long.
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Being only copilot I can only suggest the idea to captains, but I don't see a problem in overriding GS mini in the conditions that we flew through.
Steady, well established 30kt wind at altitude, gradually and nicely decreasing to a fixed value between 10 - 15kt on ground, I don't see any problem with a Vls+5 approach speed. (VLS+8 actually including the vpilot)
As long as there isn't anything forbidding it in the OM A or B, nobody has a say apart from the captain.
If it can avoid a third go around in less than 6 flights into this particular airport, we will do it.
GS mini does a nice job in harsh turbulence, or light windshear conditions. This was not the case. It was increasing speed for the sake of it, with no added benefit.
Also my reports went through our airline services, they may come back with an answer.
Steady, well established 30kt wind at altitude, gradually and nicely decreasing to a fixed value between 10 - 15kt on ground, I don't see any problem with a Vls+5 approach speed. (VLS+8 actually including the vpilot)
As long as there isn't anything forbidding it in the OM A or B, nobody has a say apart from the captain.
If it can avoid a third go around in less than 6 flights into this particular airport, we will do it.
GS mini does a nice job in harsh turbulence, or light windshear conditions. This was not the case. It was increasing speed for the sake of it, with no added benefit.
Also my reports went through our airline services, they may come back with an answer.
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It was increasing speed for the sake of it, with no added benefit.
Interesting discussion. The Airbus FBW and Boeing Vapp logic work in opposite directions in varying winds; With an increased HW gust, Airbus will increase thrust and IAS, (to maintain ground speed), Boeing will decrease thrust and IAS, (to maintain airspeed).
So given a gust, the Airbus will maintain its "place" on approach; whereas the Boeing will "move back" with a HW gust and "forwards" for a TW gust.
Always nervous when folk talk about overriding Airbus GS Mini, which could reduce safety margin in the event of an unexpected gust or wind drop. Some think the Airbus does the wrong thing or gets "out of phase", because it increases thrust and IAS with increased HW gust, (and vice versa). which is the opposite way round to "conventional" aircraft
So given a gust, the Airbus will maintain its "place" on approach; whereas the Boeing will "move back" with a HW gust and "forwards" for a TW gust.
Always nervous when folk talk about overriding Airbus GS Mini, which could reduce safety margin in the event of an unexpected gust or wind drop. Some think the Airbus does the wrong thing or gets "out of phase", because it increases thrust and IAS with increased HW gust, (and vice versa). which is the opposite way round to "conventional" aircraft
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I was unclear. You can’t turn it off in the sense that it’s always operating in the background, calculating what your speed should be. You can always fly the speed you want by selecting it, or disconnecting the autothrust.
But if you do override GS Mini and select a fixed speed, or use manual thrust and ignore the IAS bug increases; remember that you could get dangerously close to the stall in gusty conditions, unless you add an additional safety factor to the speed you select.
Then of course, you will have to check your landing distance calculations for the additional speed you have added.
Then of course, you will have to check your landing distance calculations for the additional speed you have added.
Only half a speed-brake
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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FWIW, I was LHR based for the vast majority of my career before retirement, and flew the A320 family for over 4 years, the rest of my career being on Boeings 737 and 747..
I recall being very happy in the LHR regime of 210, 180 and then 160 to 4dme on all types I flew.
The only times it caused concern was on the A320 in very strong headwinds when reaching 4dme at 160 and pressing managed speed resulted in a speed increase on occasion to 170+,
I learned from that and whenever another aircraft was close ahead - usually, used selected speed inside of 4d at an appropriate value - you won't fall out of the sky!
I recall being very happy in the LHR regime of 210, 180 and then 160 to 4dme on all types I flew.
The only times it caused concern was on the A320 in very strong headwinds when reaching 4dme at 160 and pressing managed speed resulted in a speed increase on occasion to 170+,
I learned from that and whenever another aircraft was close ahead - usually, used selected speed inside of 4d at an appropriate value - you won't fall out of the sky!
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It is allowed to fly VLS even in gusty conditions (not advisable, however, the conditions on the two said days were not gusty at all)
I recall being very happy in the LHR regime of 210, 180 and then 160 to 4dme on all types I flew.
E.g., no - upon arrival of front gust it does not add thrust.
From Airbus A320/321 FCOM:
GROUND SPEED MINI FUNCTION PRINCIPLEThe objective of the Ground Speed Mini function is to take advantage of the aircraft inertia, when the wind varies during the approach. This objective is achieved by providing the adequate indicated speed target (i.e. the managed speed target represented by the magenta triangle). When the aircraft flies this indicated air speed target, the energy of the aircraft is maintained above a minimum level ensuring aerodynamic margins versus stall.
During the approach, the FG continuously computes the managed speed target in order to take into account the gusts or wind changes.
During the approach, the FG continuously computes the managed speed target in order to take into account the gusts or wind changes.
I might be missing something, but am struggling to understand how the aircraft would follow an increased managed speed target from GS Mini, without increasing the thrust?
Or maybe my semantics are in question? With a gust, the FG computes a new managed speed target, which the auto-thrust follows, (if it is engaged). i.e. GS Mini itself does not add thrust, but it dynamically changes the managed speed bug, which then causes the auto-thrust to add thrust if required.
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The calculated GS mini will increase, but with a gust the thrust usually does not increase as the gust will be the cause of an increased speed anyway. Once the gust is over the GS mini target will decrease, as will the indicated airspeed. Now, as always, things are not perfect, so there will be some play on thrust, but actually not all that much.
It helps to fly a few approaches in gusty weather using GS mini on manual thrust. It is surprising how little thrust changes there are.
It helps to fly a few approaches in gusty weather using GS mini on manual thrust. It is surprising how little thrust changes there are.
??? Sorry, I don't get you at all. HW gust needs increased thrust to follow the increased GS Mini IAS demand to maintain the groundspeed.
I grant you, the system can seem a bit lively in gusty conditions, which alarms some pilots.
I grant you, the system can seem a bit lively in gusty conditions, which alarms some pilots.
Initially the thrust does not need to increase to follow the speed target because the gust itself has caused the aircraft to follow the speed target. Whether the thrust comes up subsequently depends on how transient the gusts are. The gustier conditions would tend to result in less auto thrust activity while descending through different strengths of relatively steady wind will result in the speed target remaining elevated for prolonged periods and the thrust will need to adjust to maintain it. There’s also the fact that GS mini has been nerfed somewhat in the NEO aircraft so the system is less “active” in those.
Ah. I don't know about the NEO, sadly.