Was the Vought XF5U the Cause of UFO Sightings?

The Vought XF5U, known as the “Flying Flapjack,” was an ambitious project that emerged during a time of extensive aircraft development in World War II.

This period saw innovations like turbojet propulsion, flying wings, and ten-engine bombers. However, unlike many successful efforts from this era, the XF5U was an abject failure.

XF5U Was Not Like Other Aircraft

The concept for the XF5U was initiated in mid-1939 by Charles H. Zimmerman, a designer known for his experimental designs and a career largely spent with the National Advisory Committee for Aeronautics (NACA) and its successor, NASA.

Zimmerman’s design philosophy for the XF5U centred on maintaining uniform airflow over the entire wingspan, or “pancake” fuselage.



This design was thought to enable the aircraft to take off and land at exceptionally low speeds while maintaining high-speed performance, making it potentially ideal for Navy fighter aircraft operating from aircraft carriers.

The aircraft’s design was quite unconventional, featuring a flat, disc-shaped wing/fuselage that doubled as the lifting surface.



The propulsion system was equally unusual, with two piston engines buried within the body on either side of the cockpit, powering propellers at the leading edge of the pancake.

This configuration promised both high and low flight speeds and high-angle attitudes for landing, takeoff, and other manoeuvres.

The Flying Pancake was like nothing else people had seen previously.

Disc Shaped Aircraft?

Among the benefits, the most significant was its potential for extremely short takeoff and landing distances, making it suitable for aircraft carrier operations. The uniform airflow over its entire body was expected to allow the XF5U to achieve low-speed stability and control, which is crucial for carrier-based aircraft.

Additionally, the design promised a wide range of operational speeds, with the possibility of reaching from as low as 40 mph up to 460 mph with enhanced engines and water injection. Such versatility would have been a considerable advantage in various combat scenarios.

However, the XF5U’s design also had significant drawbacks. The complexity of its design posed substantial engineering challenges.

The unconventional placement and operation of its engines and propellers required a complex gearbox system, which proved to be problematic. Issues such as vibrations and difficulties with the propeller mechanisms were persistent during its development.

A mockup of the XF5U. The glass floor can be seen on the underside of the cockpit.

Another drawback was the aircraft’s visibility challenges. The pilot’s forward visibility was limited due to the high angle of the aircraft when on the ground, a problem partially mitigated by transparent panels for downward vision, but this was a less-than-ideal solution.

Technological advancements also worked against the XF5U. By the time the aircraft was nearing readiness, World War II had ended, and there was a shift in focus towards jet-powered aircraft. The propeller-driven XF5U, despite its innovative design, was becoming obsolete in the face of rapidly advancing aviation technology

A prototype under construction.

V-173 Flying Pancake

Before the XF5U, there was the V-173, a quarter-scale development aircraft that first flew in November 1942. Despite being underpowered, the V-173 completed 131 hours of successful flight tests, piloted by notable aviators, including Charles Lindbergh and several Navy pilots.

The V-173’s design featured a tall undercarriage for an angled ground position, which limited forward visibility until the tail lifted off the runway.

Despite its unconventional design, the V-173 proved to be quite successful in its test flights. It demonstrated excellent low-speed handling characteristics and could take off and land in very short distances. The aircraft’s tall undercarriage was designed to give it a ground angle of 22.25 degrees, aiding in its short takeoff capability.

While the V-173 never progressed beyond the experimental stage, its flight tests provided valuable data that contributed to the development of the XF5U.

Work on the enlarged XF5U-1 designated VS-315, began in mid-1942, with the Navy expressing interest in procuring two of these planes in September 1942.

Zimmerman envisioned the XF5U achieving phenomenal speed ranges, potentially reaching 460 miles per hour with improved engines and water injection.

The engine arrangement was one of the most significant challenges in the development of the XF5U. The aircraft’s propellers rotated in opposite directions and were attached to shafts enclosed by circular nacelles extending forward from the fuselage. Special attention was required for the design of the fuel and oil systems to ensure operation at high angles of attack.

Tail draggers are known to be difficult to see out of on the runway. Imagine what it is like in this!

The XF5U in Combat

As a combat aircraft, the XF5U-1 was to be heavily armed, with three .50-caliber machine guns on each side of the cockpit and provisions for replacing four of these guns with 20-mm cannons. It was also intended to carry two 1,000-pound bombs under the fuselage.

Despite these ambitious plans, the XF5U program faced numerous challenges. A wooden mockup was ready by June 1943, with a contract for two aircraft signed in July 1944.

The first XF5U-1 rolled out for ground testing in late June 1945, but flight tests were delayed due to issues with the articulated propellers and problems like vibration and gearbox complications.

The gearbox design was complicated, to say the least.

The end of the Second World War in August 1945 led the Navy to review its aircraft development and procurement efforts, with the XF5U becoming a prime target for cancellation. The program was ultimately cancelled in March 1947, and the two aircraft were scrapped the following year.

The XF5U’s legacy lies in its innovative approach and the potential it demonstrated, albeit unrealised. This aircraft was a product of its time, reflecting the innovative spirit and experimental approach to aviation technology during World War II.

Was the Flying Pancake the Cause of UFO Sightings?

It’s plausible that the Vought V-173, with its unusual and distinctive design, could have contributed to some UFO sightings during its testing period. Its design was unlike any traditional aircraft of the time, featuring a circular fuselage and leading-edge propeller engines, which could have appeared strange and unfamiliar to the general public.

Could this unusual shape of caused UFO sightings?

During its test flights, the V-173’s appearance in the sky, particularly at a distance or under certain lighting conditions, could easily have been mistaken for something otherworldly.

The concept of unidentified flying objects (UFOs) often involves sightings of aerial phenomena that don’t fit conventional aircraft descriptions, and the V-173 certainly fits that criterion.

Moreover, during the 1940s, public awareness and interest in “flying saucers” and extraterrestrial life were growing, partly fueled by the famous Roswell incident and similar reports. In such a context, the sight of an aircraft as unconventional as the V-173 could easily have led to speculations and reports of UFO sightings.

However, it’s important to note that while the V-173 might have contributed to some UFO reports, it certainly wouldn’t account for all such sightings, especially those occurring in different periods or locations where the V-173 wasn’t operational or tested.