Wearing wings and double jumping makes you fly like you would in creative or when wearing the angel ring. is this intended?

Just personal opinion, I tested on stable forge(version 2768) and failed to reproduce this bug.
There is a possibility that
a) there is a problem regarding modpack setup, or
b) some other thing in your inventory give you that ability to fly, or
c) someone enabled fly mode for you either using a mod or server plugins