The Vought XF5U-1 was a development of an earlier, smaller
aircraft - the V-173.
The V-173 first flew in 1942 and was designed to prove
the concept of a twin-propellor, blended wing circular
aircraft. The V-173 was a relatively basic prototype considering
the complexity of the overall design. It featured propellors
from the F4U-4 Corsair, two 80 horsepower engines, and
a fixed undercarriage. However it served its purpose and
showed that the design worked, therefore the green light
was given to develop a full-size version.
The XF5U-1, nicknamed the 'Flapjack' due to its peculiar
shape, was a considerably more advanced aircraft than
the V-173. Power came from two 1350 horsepower Pratt and
Whitney R-2000-7 radial engines, and the four bladed propellors
were custom built for the aircraft.
Additionally, whereas the V-173 had used a lightweight
but flimsy construction technique which primarily consisted
of a fabric covered wooden structure, the XF5U-1 featured
a largely metal construction method. Due to this fact
the XF5U-1 weighed an incredible five times the amount
of the prototype.
Two examples of the XF5U-1 were constructed and underwent
extensive ground tests, including a few short hopping
flights - but no full flights. From the outset the aircraft
suffered from vibration problems. Unfortunately, due to
the rapid advances in jet aircraft and more conventional
rotor aircraft the engineers never had the time to correct
the problem as the project was canceled in 1947 in favor
of more modern aircraft.
Both XF5U-1 prototypes were subsequently dismantled and
destroyed. Thankfully however the V-173 was rescued and
is now preserved by the Smithsonian.