B737 flap question
 

I wonder if you select flaps 40 a few knots below placard speed, will they immediately come out, or will they delay until passing 153 (-300/500)?. If this is the case, it is somewhat similar to the logic that retracts them at 158, and re-extend at 153.

thnx

As far as I remember (some years now), they will come out immediately. I believe the flaps need to be set at 40 for the Flap Load Relief function to be armed.

They will come out ! Though on the 300/500 you won't be using F40 too often... (Unless it's CAT 3 or very slippery/icy out there or if you have a significant tailwind of course...) I wouldn't worry about the flap load relief too much on the 300/500 mainly because with the landing weights and corresponding Vref's it shouldn't mean a problem. At least I have never experienced it anyway.