GS-Mini, Auto-thrust, and Short Runways – Airbus A320/330/340
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Greetings NSF and congrats on a great explanation of the much misunderstood Airbus system. I have just a couple of comments to help others understand it:
1. The title says all - Groundspeed minimum ie the Fmgc works out, as NSF has explained, the minimum G/s it will maintain all the way down and it merely fiddles the Vapp to maintain it.
2.In situations of huge differences in wind,G/s mini limits Vapp to Vfe Config Full -5kts.
3.To clarify the thinking, consider an occasion where the wind at 1000ft and also down the R/w is 100kts - unlikely I know - G/s Mini will not add anything to Vapp.
4. Where the guys sometimes go wrong is by putting in the ATIS/Volmet wind and then not updating it on finals. G/s mini is only as good as the Twr wind you insert so make sure it is accurate. Get into the habit of glancing at the Perf App Page wind as the guy in front is cleared to land to make sure you have good data - remembering Data Lock!
1. The title says all - Groundspeed minimum ie the Fmgc works out, as NSF has explained, the minimum G/s it will maintain all the way down and it merely fiddles the Vapp to maintain it.
2.In situations of huge differences in wind,G/s mini limits Vapp to Vfe Config Full -5kts.
3.To clarify the thinking, consider an occasion where the wind at 1000ft and also down the R/w is 100kts - unlikely I know - G/s Mini will not add anything to Vapp.
4. Where the guys sometimes go wrong is by putting in the ATIS/Volmet wind and then not updating it on finals. G/s mini is only as good as the Twr wind you insert so make sure it is accurate. Get into the habit of glancing at the Perf App Page wind as the guy in front is cleared to land to make sure you have good data - remembering Data Lock!
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Originally Posted by upspeed
My airline uses the stabilized approach technique for all A-320 operations and has recentely defined that crews should insert on the F-PLAN page, the VAPP on the final fix of the procedure. My question is: does this inhibit the GS Mini function of the A/THR? I've searched the FCOM and the FCTM, and PPRUNE, but without results...anyone care to shed a light on this?
But usually VAPP insertion at the FAF is only recommended for non precision approaches ...
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On the technical side, I am ready to take your word TyroPicard.
You must be correct, at least I have not seen anything implying the contrary and I don't remember to have personally tested such thing.
On the practical side, accelerating 20 knots if necessary after passing a possible 4 DME final does not seem to be the best criteria to "stabilize an approach". To not insert any speed constraint at the FAF would be more logical ... in my view.
You must be correct, at least I have not seen anything implying the contrary and I don't remember to have personally tested such thing.
On the practical side, accelerating 20 knots if necessary after passing a possible 4 DME final does not seem to be the best criteria to "stabilize an approach". To not insert any speed constraint at the FAF would be more logical ... in my view.
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Originally Posted by upspeed
My airline uses the stabilized approach technique for all A-320 operations and has recentely defined that crews should insert on the F-PLAN page, the VAPP on the final fix of the procedure. My question is: does this inhibit the GS Mini function of the A/THR? I've searched the FCOM and the FCTM, and PPRUNE, but without results...anyone care to shed a light on this?
"Insertion of Vapp as a constraint at FAF will have NO effect on GS mini after the FAF" and also before the FAF as well.
Actually, one effect of VAPP insertion at the FAF is to slightly advance the automatic deceleration point position.
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change after Warsaw accident?
Have been told - even by an Airbus test pilot who confirmed with a second one - that any pilot input for wind (tower wind) on performance page internally starts being phased out from 400ft to landing, where value always is taken "Zero".
I can live with this if true as it means GS should become greater thus safer in case of headwind.
Unfortunately when observing GS during approach I never saw GS increasing below 400ft even with speed target still well over vls so I ask myself anyway is the statement really true.
Should it be true I still see problems: When GS is increased between 400ft and landing this might mean autothrust could go to unwanted "idle" when new GS is reached so to add to the confusion I do believe now entering wind 0/0 could then be the safest action...
I can live with this if true as it means GS should become greater thus safer in case of headwind.
Unfortunately when observing GS during approach I never saw GS increasing below 400ft even with speed target still well over vls so I ask myself anyway is the statement really true.
Should it be true I still see problems: When GS is increased between 400ft and landing this might mean autothrust could go to unwanted "idle" when new GS is reached so to add to the confusion I do believe now entering wind 0/0 could then be the safest action...
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green dot speed
guys,
need a quick one:
on 320/330/340 can we fly(selected) below the green dot speed on approach,with clean config?
is it legal?
safe?
any airbus documents that prevents you from flying below green dot with clean config on app?
need a quick one:
on 320/330/340 can we fly(selected) below the green dot speed on approach,with clean config?
is it legal?
safe?
any airbus documents that prevents you from flying below green dot with clean config on app?
NSF, Thanks for the great explaination of GS-mini. I flew the Bus for 10 years or so and am too lazy to go into the detail you did, but I always assumed it worked about like you said. That is why I usually used AT and managed speed. Even the new Boeings just use speed additives and hope for the best. One of the reasons I always really liked GS mini is that back in the dark ages flying the KC135 in the USAF we used a thing called reference ground speed where you flew your planned approach speed on the ground speed indicator instead of using IAS in really windy conditions. I have never heard of any other Boeing operator doing anything like that.
