RE: Wingtip Changes/ideas. Neep Help!!
I've notice upswept tips on all the newer commercial jets. When they were first used on smaller aircraft they were called splates. Intention was to keep that part of the airflow that goes around the tips instead of over and under directly on the tips for better lateral control. The Robertson tips used by Cessna turn down rather than up. I don't understand the reasoning behind it but I'm not an aeronautical engineer. The reasoning for squared off tips on P-51 types is essentially the same. Airflow tends to go around the tips not over a small portion of the wing. Splates are supposed to counteract that.