Chance Vought Flying Flapjack
The XF5U discoidal
aircraft was an invention of Charles H. Zimmerman, who conceived the
design in the early 1930s. He won a 1933 National Advisory Committee
for Aeronautics (NACA) design competition with a disc-shaped concept
capable of flying at high speeds or hovering; NACA rejected further
development because they thought the design was "too advanced".
was not discouraged and in his spare time built a number of test
models, including a rubber-band powered flying version. His original
plan was an aircraft which carried three crew, in a prone position to
allow maximum streamlining. The idea was subject to a 1938 patent he
joined Chance Vought Aircraft in 1937, and there was able to produce an
electric powered model of his design, designated V-162, flown by remote
control in test situations, tethered in a hangar. The rear fuselage was
hinged to act as an elevator.
Zimmerman provided an original blueprint to the US Navy (featuring no
horizontal stabilisers) in March 1939. A month later, the Navy asked
NACA (which later became NASA) to investigate the proposal. In October
1939 manufacture by Chance Vought of a small scale model for wind
tunnel testing was approved. The design was referred to as V-173.
This revealed problems with the trailing edge "ailevator" design, and
horizontal "flying tail" stabilisers were introduced. After full-scale
wind tunnel tests in September 1941 at Langley Field, Va., the Navy
asked Vought to build two military versions of the aircraft, to be
designated XF5U-1. One would be for flight testing and the other for
The first flight took place of a V-173 on 23rd November, 1942. Soon
after takeoff, Boone T. Guyton, Vought's chief test pilot, found the
controls sluggish, and had to struggle to make a wide turn back to
base. Otherwise the design was a promising one, and a wooden mock-up
XFU5-1 was completed the following June.
Flight tests progressed slowly but satisfactorily. On July 15, 1944, a
development contract consolidated the V-173 and XF5U-1 programs.
By the end of the V-173 flight tests convinced Boone Guyton and
designer Zimmerman that the design had potential. They had faced
financial and technical problems but had persisted. One major problem
was the propellers, initially the same as those used on the F4U-4
Corsair. These had to be replaced with flapping blades to avoid
vibration; a four-bladed design was finally produced, each propeller
having one pair of blades staggered ahead of the other pair set at
The twin 1,350 hp Pratt & Whitney engines gave the XF5U-1 an excellent
speed range of 40 mph to 425 mph, much better than the usual 1 to 4
ratio of landing speed to top speed of other good designs. Water
injected engines gave a 20-460 mph range, and gas turbines allowed
0-550 mph. The ship carried 261 gal. of internal fuel, and six 20 mm
cannons, three stacked vertically in each "wing root".
In June 1947, Boone T. Guyton flew the V-173 to Floyd Bennett NAS for a
Navy Day display. As he neared the base, bathers on the Long Island
Sound beaches saw a silver and yellow disc moving slowly overhead and
rushed to report a "flying saucer". Guyton participated in the display
then returned to the Vought factory at Stratford, Conn. This was the
final performance of the Flying Flapjack.
On March 17, 1947 the Navy had cancelled the XF5U-1 development,
preferring to go with jet aircraft. The static test aircraft had
already been demolished during laboratory tests, and the Navy ordered
destruction of the flying version. Its engines, instruments and other
salvageable items were removed and the airframe placed under the steel
ball of a demolition crane. The first few drops failed to dent the
After careful measurements the ball was dropped between the main beams
and spars, and the aircraft was eventually reduced to crumpled
wreckage. The V-173 was approved for display at the Smithsonian.
CHANCE VOUGHT XF5U-1
Two Pratt & Whitney
R-200-7 engines, each 1,350 hp.
32 ft 6 in.
28 ft 7½ in.
14 ft 9 1n.
NORMAL LOADED WEIGHT:
TAKEOFF DISTANCE, no wind:
RATE OF CLIMB:
3,000 ft / min. at sea level
388 mph at 20,000 feet.
6x .50 cal. or
4x 20 mm machine guns,
2x 1000 lb. bombs.