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nr1chris
5th May 2023, 08:50
Hello to everyone,

why should I disconnect the A/THR in the overweight landing case to follow vls reduction as surfaces extend? What is the reason behind it? The lowest selectable speed is vls? Isnít it? Is it better thrust control to avoid to undershoot vls?

Thanks for any hint
Kind regards

8314
5th May 2023, 09:17
If you’re really heavy VFE CONF1 is below VLS and your thrust won’t let you fly to flaps 1 speeds.

JABBARA
5th May 2023, 22:10
LANDING WITH SLATS OR FLAPS JAMMED
......If VLS is greater than VFE NEXT (overweight landing case), the FLAPS lever can be set in
the required next position while the speed is reduced to follow VLS reduction as surfaces
extend. The VFE warning threshold should not be triggered. In this case, disconnect the
A/THR. A/THR can be reengaged when the landing configuration is established.
For A 330-300s which I know WV, Structural MTOW is 233t, and always Vls was <VFE NEXT, that is in normal flap/slat extension
However when one of those fail to extend normally, Vls (for actual configuration) may be greater than VFE NEXT,
In this case, even on PFD shows Vls > VFE NEXT, you can extend available configuration because VFE NEXT assumes normal extension and in this case it is incorrect. Therefore, although Vfe (barber pole) will show immediately on PFD for selected lever position and actual speed will be above Vfe, OVERSPEED Warning will not be triggered immediately; this is because OVERSPEED Warning only starts when configuration is physically extended. Besides, OVERSPEED triggering speed will change depending on failed part vs. extended part combination. During this time gap if selected speed is reduced as following dropping Vls (which relies on actual configuration) by A/T, there is no problem, no need to disconnect A/T. However if A/T remains sluggish to follow dropping Vls, this may cause OVERSPEED warning and in this case it is advised to disconnect A/T and handle thrust manually till the configuration is established

nr1chris
7th May 2023, 12:40
Thank you Jabbara. Thatís a really good explanation. I really appreciate.

JABBARA
7th May 2023, 19:56
nr1chris (https://www.pprune.org/members/279509-nr1chris) I do thank you,
Sometimes I consider my non-native English may not be so clear to explain what I want to say
Take care, happy landings

Jabbara