Complex sentence: The second FB-1 was modified to investigate a tip-jet driven rotor with propulsion provided by propellers mounted at the tip of each stub wing-this became known as the Jet Gyrodyne, which despite its name, was a compound autogyro.
Split into simpler sentences: The second FB-1 was modified to investigate a tip-jet driven rotor with propulsion provided by propellers mounted at the tip of each stub wing. This was renamed Jet Gyrodyne, which despite its name, was a compound autogyro.