XF5U Flying PancakeXF5U Flying Pancake airplane model. One of the most unusual aircraft ever designed for the U. S. Navy was the Chance Vought V 173, also known as the Zimmerman "Flying Pancake". It was a prototype "proof of concept" aircraft that lacked wings, instead relying on its flat circular body to provide the lifting surface. This multi million dollar project nearly became the first V STOL (vertical takeoff and landing) fighter. The V 173 blueprints were shown