Step turn wrote.
This to me is an open issue. Irrespective of the theories of physics purity in the moving parcel of air, my experience (in the aforementioned C150) has been that if you're planning a low speed turn toward downwind, allow for a period of lesser performance as the 'plane accelerates inertially, to catch back up to the moving parcel of air. Right or wrong, this has been taught and demonstrated to me, and I teach it onward as I mentor. Purists will tell me I'm wrong - perhaps so, but I'm wrong so as to remind pilots to be conservative and safe about performance in a changing and demanding regime of flight.
That about sums it up.
