I have only tested with the MH-9 and AH-9, but it seems to be unaffected by gravity, since you can easily fly it upside down without drastically losing altitude.
Also the controls for choppers seem to be to arcade and less responsive than what they were in Arma 2/OA or ACE2
Take a littlebird, get some speed going and go upside down and try flying like that
Please take in mind that the Arma 3 is currently in alpha and still heavily work in progress so this is currently not a final state of Littlebird.
Issue closed as obsolete. If you encounter this problem again, please create another ticket. Thank you.