A320, flying knowledge, SOP, clarifications
Joined: Sep 2011
Posts: 350
Likes: 147
From: FL390
Crikey. Tell me you don't have a clue about a feature without telling me you don't have a clue about a feature.
As long as it’s not routine I can’t see the problem with adding a couple of knots. My operator went down the “trust the load sheet” line, but it’s pretty obvious when the calculated approach speed is a little too low.
The aircraft (especially the A321) tends to wallow around and is very quick to decelerate further but reluctant to accelerate, even with a large thrust input. None of the Airbus series are happy about you entering the flare a few knots slow as I can vouch for from personal experience.
Joined: Jun 2007
Posts: 3,443
Likes: 39
From: Wanderlust
What was entered as ZFW shouldn't matter once Approach is activated because after that Vapp is not estimated but calculated. Following was a bulletin from Airbus.
GW and CG values are computed from entered ZFW and ZFWCG corrected for the predicted FOB and CG variation. When the Approach phase is activated, the characteristic speeds are recomputed using the actual weight and CG.The performance model used to compute the characteristic speeds, is accurate enough to provide speed errors of less than ± 2 kt from the certified speeds.
GW and CG values are computed from entered ZFW and ZFWCG corrected for the predicted FOB and CG variation. When the Approach phase is activated, the characteristic speeds are recomputed using the actual weight and CG.The performance model used to compute the characteristic speeds, is accurate enough to provide speed errors of less than ± 2 kt from the certified speeds.
Joined: Sep 2011
Posts: 350
Likes: 147
From: FL390
GW and CG values are computed from entered ZFW and ZFWCG corrected for the predicted FOB and CG variation. When the Approach phase is activated, the characteristic speeds are recomputed using the actual weight and CG.The performance model used to compute the characteristic speeds, is accurate enough to provide speed errors of less than ± 2 kt from the certified speeds.
Airbus have to cover themselves from a regulatory point of view and their guidance is just that, guidance. On a 3000m runway there is little risk in increasing Vapp by 2 knots, provided it's taken into account in the performance. Doing it routinely because your landing technique is wrong is a different matter.
Joined: Apr 2022
Posts: 287
Likes: 45
From: Italy
What was entered as ZFW shouldn't matter once Approach is activated because after that Vapp is not estimated but calculated. Following was a bulletin from Airbus.
GW and CG values are computed from entered ZFW and ZFWCG corrected for the predicted FOB and CG variation. When the Approach phase is activated, the characteristic speeds are recomputed using the actual weight and CG.The performance model used to compute the characteristic speeds, is accurate enough to provide speed errors of less than ± 2 kt from the certified speeds.
GW and CG values are computed from entered ZFW and ZFWCG corrected for the predicted FOB and CG variation. When the Approach phase is activated, the characteristic speeds are recomputed using the actual weight and CG.The performance model used to compute the characteristic speeds, is accurate enough to provide speed errors of less than ± 2 kt from the certified speeds.
I made part of my approach prep routine to compare GW with GW FK in the AIDS page and add 1 note for every tonne of difference up to 3-4 kts.
Last edited by enzino; 5th March 2023 at 11:08.
Joined: Jun 2007
Posts: 3,443
Likes: 39
From: Wanderlust
Last edited by vilas; 5th March 2023 at 14:27.
Joined: Jun 2006
Posts: 240
Likes: 8
From: B.F.E.
Airbus allows the flight crew to manually adjust Vapp to compensate for wind effects that GS mini is not well-tuned to capture. GS mini works best in steady wind gradients and normal gusts, but sometimes gets a little behind phase in sudden shears. This is really going to be environmental based on conditions or local knowledge, and as previously stated not to adjust a faulty landing technique on a calm day. To quote Airbus:
“In some situations (e.g. gusty conditions or strong crosswind), the flight crew may choose a higher VAPP than the AFS computation as good airmanship”.
https://safetyfirst.airbus.com/contr...h-and-landing/
“In some situations (e.g. gusty conditions or strong crosswind), the flight crew may choose a higher VAPP than the AFS computation as good airmanship”.
https://safetyfirst.airbus.com/contr...h-and-landing/
Joined: Jun 2007
Posts: 3,443
Likes: 39
From: Wanderlust
There was never any doubt that pilots can increase upto 15kts in gusty conditions. We were talking about nitpicking a few knots for the heck of it.
Firsty ferret and enzino see below:
FCOM 22_20-40-10 OPTIMISATION
The FMGC uses the performance model and either the predicted landing weight or the current gross weight at transition to the approach phase to compute approach speeds (VLS, VAPP, F, S, Green Dot).
Firsty ferret and enzino see below:
FCOM 22_20-40-10 OPTIMISATION
The FMGC uses the performance model and either the predicted landing weight or the current gross weight at transition to the approach phase to compute approach speeds (VLS, VAPP, F, S, Green Dot).
Joined: Jun 2007
Posts: 3,443
Likes: 39
From: Wanderlust
If you increase the ZFW value inserted in Init B in flight, you will see the VLS going up.
