Designed around the new Pratt Whitney 2,000HP radial engine and tuning the largest propeller ever attached to a fighter plane, the Vought F4U Corsair became a legend in its own time. The F4U-1 was the first production version of the Corsair. It had an inverted gull wing and a production version of the Corsair. It had an inverted gull wing and a framed canopy with a flat top. However may problems were found soon. For example, the port wing stall often gave the Corsair unstable landing. Anther problem was poor visibility because of its long nose and framed canopy. Therefore F4U-1A: the cockpit was raised about seven inches, the framed canopy was replaced with a semi-bubble design canopy, and the taller tail wheel strut was equipped; was introduced. F4U-1D with clear vision canopy on frameless was introduced later for more visibility.