Vought XF5U, the “Flying Pancake” (1947)

When we talk about strange aircraft, it is impossible not to mention the Vought XF5U, a machine developed in the United States during World War II. Although a scale model demonstrated that this concept was viable and would have theoretical performance similar to the jets of that era, the authorities of that country cancelled the project. Despite never having flown, the Vought XF5U or “Flying Pancake” deserves a place in aviation history.

Aviation engineers - especially during great conflicts - have tried to find ways to improve the basic design used by almost all aircraft. While the “fuselage-wings-tail” scheme works, and very well, the industry has always strived to find some revolutionary design that would provide a strategic advantage, improved performance, or lower fuel consumption.

During World War II, the US Navy worked on the design of a very unorthodox aircraft model, in which the lifting surface - a task basically carried out by the wings - was the fuselage itself. The designer in charge was Charles H. Zimmerman, and the aircraft was officially known as the Vought XF5U “Flying Flapjack”, although not a few referred to it - inspired by its strange appearance - as “Flying Pancake”.

The body of this aircraft had the shape of a flattened disc, and served as a source of lift. While in a “conventional” aircraft, the wings are responsible for “holding it” in the air (thanks to the pressure differences that arise when air passes over and under them), in the Vought XF5U it was the fuselage that took care of this function. The design was based on an earlier prototype, the V-173, although the “flying pancake” was considerably larger and five times heavier. It was built entirely of metal, and obtained its thrust from two Pratt & Whitney R-2000 radial engines of 1,600 hp (1,193 kW) each.

At first glance, it seems that the XF5U could never take off, since its wings are not visible. But although it is true that aircraft designers use long wings for aerodynamic reasons - wings with a small aspect ratio between length and width have very poor performance due to the vortices created at the wide ends, causing drag - the scale model that was built demonstrated that the “Flying Pancake” was capable of flying. And very well!

Despite not having long, narrow wings, the XF5U avoided the vortex problem by canceling them with its propellers. Indeed, the propellers rotated in the opposite direction to the vortices generated by its flattened fuselage, maintaining high air pressure under the aircraft. This allowed it, even with a relatively small lifting surface, to have great maneuverability and structural strength.

The propellers could move their blades in the same way a helicopter does with its main rotor, varying their angle to assist the aircraft during maneuvers. The pilot's seat had an ejection system, specially adjusted to allow him to avoid hitting the propellers in case he had to abandon the aircraft during an emergency.

The only XF5U built had a machine gun and cannons installed under its nose. For many, the Vought XF5U was one of the greatest aviation disappointments known. Despite having the Navy's support, its strange (and revolutionary) design caused US authorities to stop supporting it. Zimmerman had to settle for the tests carried out on the scale model, equipped with smaller engines.

History has shown that many times those radical designs are effective. Looking at an F-117, for example, it also seems like a junker lacking aerodynamics and not very effective. But it flies. Northrop's flying wings, which were once discarded for the same reasons as the XF5U, have been vindicated in the B-2 stealth bomber. It is possible that if the person in charge of managing the money allocated to these projects had had a more open mind, the “Flying Flapjack” would have reached the assembly lines. Don't you think?