Weird Wings - Chance Vought V-173 / XF5U 'Flying Flapjack'
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".
Zimmerman 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 filed.
Zimmerman 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.
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
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 static testing.
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 mockup 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 propellors, 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 propellor
having one pair of blades staggered agead of the other pair set at right angles.
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.
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 aircraft.
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 V-173 specs:
Two Continental A-80
engines of 80 hp each.
23 ft. 4 in.
26 ft 8 in.
12 ft 11 in.
16 ft 6 in.
|TAKEOFF DISTANCE (Calm):
200 ft. (0 ft. in a 25 kt. wind)
CLIMB to 5000 ft:
MAX. SPEED (sea level):
|CHANCE VOUGHT XF5U-1 specs:
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.
More V-173 / XF5U links:
Flying Flapjacks, V - 173 and XF5U - 1
Vought V-173 / XF5U-1 Flying Flapjack Info