Thank's Nike.
Of course I know the QRH note. I also know the FCTM explanation Low Fuel in 8.24.
Of course "In some situations, at the captain’s discretion, deviation from a checklist may be needed".
As I said it is not a matter of in-flight management. It is a matter of regulations interpretation. The whole point is to check a RLD based on the planned conditions. You're entering wind and contaminated Rwy condition although you're not sure you'll face these conditions once airborne if diverting to this alternate or even to another airport...
Regulations call for RLD check with expected conditions that you'll enter in the OPT.
Landing with 30 mins in the tanks at the alternate is a normal condition for regulations.
It is obviously a "non normal" condition for Boeing since it will trigger a "non normal" C/L!
Whatever is the explanation for the NNC, there will still be a NNC that you may disregard, or not, based on captain's discretion.
Usually captain's discretion applies when it will improve safety. May I say that one could consider that choosing a better alternate or making sure RLD provisions are met with Flaps 20, providing you have the tools, might more improve safety than deciding to disregard a NNC at planning stage?
Is it normal to plan on landing with a NNC, to only check a Flaps 30 RLD at planning stage and to already decide to disregard the NNC requirements? It comes down to considering this non normal C/L as normal and to systematically disregard the call for FLAPS 20.
I'm not sure it is intellectually satisfying.
Based on Long Haul post, it looks like it is not that normal since his legacy airline is calling for additional fuel based on the result of "inflight" FLAPS 20 LDA calculations...
I would also prefer the answer to be as simple and practical as saying captain's good judgment. I'm not sure that good judgment is standardised and I don't think regulations point in that direction.
Thank's for the input anyway since it comes close to what we are doing, although is it entirely satisfying?