To elaborate on the last post there are two causes for this. First, sometimes after landing if you don't pull your hook up you will get thrown off the back, so I just land without the hook. Second, when on a CV if you have your flaps down, and are just a tad over idle on your throttle your plane will roll backwards slowly. This is actually really nice when you overshoot the hotpad and want to get back to it, or if you are taking off with a full fuel/ord load and want as much runway as possible. So just land without a hook, or pull it up right away, and make sure your throttle closed all the way after landing.