as Lusche mentioned, when you launch/deploy to the runway in Medium/Heavy bombers you will normally launch with flaps deployed ...........it is recommended to get airborne and let speed get up to say 140 IAS ( IAS = indicated air speed ie.... the white needle ) once speed has picked up, raise flaps, until you get use to it, raise them 1 notch.let speed pick up a bit more, then bring in the other notch...
if you raise them all before taking off, it will take longer and more speed to get the bomber to lift off when heavy ( when loaded down with bombs ).if you have them down and get airborne, but raise them all suddenly the bomber may drop out from under you because you are not fast enough to generate enough lift .......
practice, practice, practice....
good luck