Any power setting above endurance RPM might keep you airborne or climb, all be it say 100fpm. Time to make gentle turn back to circuit or alternate runway. Had to do it a few times because of cracked cylinders. I had a dropped valve, put that one down in a field. Another partial power from 5000 feet managed to get back to airfield on 2100 rpm maximum i could get..that was a carb. flooding fault.