ModelArt - XF5U-1 Flying Pancake, Model kartonowy - ModelArt
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BRIEF HISTORY OF CHANCE VOUGHT XF5U-1 FLYING PANCAKE
There are many descriptions used for XF5U-1 - the "Flying Pancake", "Flying Saucer", "Flying Flapjack" or "Zimmer's
Skimmer" were all names of the Charles Zimmermann's unorthodox brainchild. If XF5U-1 was ever flown, definitely it
would be described also as the world's fastest and slowest aircraft, and the world's first VTOL. Unfortunately, this
strange-looking aircraft was never given the chance to be taken off the ground.
The designer of "Flying Pancakes" Charles Zimmermann is well known specialist of aeronautics, despite he graduated the
University of Kansas with a degree in electrical engineering. Zimmermann made a name being a NACA employee by first
solving the problem of free-spinning wind tunnel.
He started his works in the field of unusual-shaped aircraft in the early 30-s, entering NACA design competition for a
civilian lightplane. In 1933 he designed a circular-wing airplane capable to fly at high speed and yet to hover like a
helicopter. Due to its aerodynamic soundness his design won the competition, but NACA rejected the idea as "too
advanced".
NACA rejected the idea, but Zimmermann did not. With the help of his colleagues Richard Noyes and John McKeller he
worked on the concept further. In 1938 he even made an attempt to obtain a US patent for his design of small airplane in
which three passengers lying prone to promote streamlining, but because of its marginal comfort the idea had been
abandoned soon.
In October 1938 Zimmermann attempted to interest the Army in a short-range observation aircraft, designated V-170 and
based on the same circular-wing scheme. The Army declined and then Zimmermann constructed an electric powered
model V-162 and piloted remotely by two pilots. The tethered aircraft flying extremely so well during hangar tests that the
Navy became interested and gave research funds.
With Navy financing the design and aerodynamic studies of the prototype V-173 were underway in 1939. As it was a full-
scale test model, it was covered with standard wing fabric overall to save weight and money. Initially V-173 had no
horizontal stabilizers, but after the model tests these were added. The aircraft was equipped with fixed landing gear, which
gave it a heron appearance in flight. The wing platform was basically the same as in XF5U-1.The V-173 took off in the air
for the firs time from Stratford, Connecticut on 23 November 1942 with Vought's Chief test pilot Boone T. Guyton on the
controls. During the tests V-173 was flown a total of 131 hours by Guyton and other Navy pilots and even by the famous
Charles Lindbergh. Today this test aircraft that paved the way for the XF5U-1 is preserved (with its vertical fins and
"flying tail" removed) in Smithsonian Institution's Air Museum storage warehouse in Silver Hill, Maryland.
In September 1941 according to the Navy request, Vought started to build two VS-315 prototypes. This designation of the
military version of V-173 was later changed to XF5U-1. One prototype was intended to static tests, and another was
supposed to be a flight test aircraft. The contract for XF5U-1 was officially issued on 15 July 1944. Gearbox problems in
the right-angle propeller driving shafts forced Vought to ask the Navy permission to shift the tests of this secret aircraft to
Muroc Dry Lake in California (today Edwards AFB) - the only airfield in the United States from which XF5U-1 had a
chance to fly safely. This and some other design problems, combined with the high costs of the project (estimated at a
quarter-million dollars) and the arrival of jet engines, were the reasons for the cancellation of the contract on 17 March
1947, after the XF5U-1 had made a number of successful taxiing trials, but it never had a chance to fly.
The original propellers of XF5U-1 were Hamilton Standard Hydromatics, used also on F4U-4 Corsair. Probably these
were used only for engine and gear shaft tests, but it is possible that the speculations for taxi tests with these propellers are
true. XF5U-1 drive system is based on counter-rotating propellers. Hamilton Standards had not left-hand and right-hand
rotation options, but on the pictures it is clearly visible that the port propeller has reversed blades (the Hamilton Standard
insignia is on the backside). However, later wooden propellers were mounted for taxi tests.
The XF5U-1 was powered by two Pratt & Whitney R-2000-7 engines of 1350 h.p. each. The calculated speed range of the
aircraft was amazing - usually the landing speed-to top speed ratio is not better than 1:4, but XF5U-1 was expected to
have a range from 40 to 425 m.p.h. with normal power, 20 to 460 m.p.h. with water injection and 0 to 550 m.p.h. with gas
turbines. With 261 gal. of fuel in internal tanks the expected range was of 1000 miles.
Armament for the XF5U-1 was to be six .50 cal. machine guns or four 20mm cannons in the wings between the engines
and the cockpit with capability for two 1000lb bombs or drop tanks on external pylons under the wing. No armament was
ever installed on the XF5U-1 prototype.
The airframe construction was of usual spar-and-longerons type and was covered with metal-and-balsa sandwich skin,
called Metalite. Its strength was outstanding. When the end came, Navy ordered the test flight prototype to be destroyed.
After the engines and all instruments and salvageable items were removed, the aircraft was placed under the crane to be
destroyed with a huge steel ball. The first drops failed to destroy the strong framework and it was necessary to make
measurements to determine the exact place on which the ball must to be dropped. After a few drops between the main
beams and spars the aircraft became a pile of twisted metal. Sad end for the fifteen years dreams of Charles
Zimmermann...
Chance Vought XF5U-1 Specification
POWERPLANT (proposed)
Two Pratt & Whitney R-2000-2(D) Twin Wasp supercharged 14-
cylinder two-row radial air cooled engines
Engine power rate
1,600 h.p. max (take-off and war emergency) each
Airscrew
16 ft (4,88 m) four-bladed, articulated, wooden
Fuel capacity
internal - 280 US gal (1,060 l)
provisional - two drop tanks 150 US gal (568 l) each
ARMAMENT (proposed)
Six .5 in (12,7 mm) Browning MG 53-2 machine guns with 400
rounds each
PERFORMANCE (estimated at 16,802 lb/7,620 kg)
Max speed at military rated power
363 mph (584 km/h) at sea level
401 mph (645 km/h) at 10,000 ft (3,048 m)
418 mph (673 km/h) at 15,000 ft (4,572 m)
435 mph (645 km/h) at 20,000 ft (6,096 m)
456 mph (734 km/h) at 25,000 ft (7,620 m)
482 mph (775 km/h) at 30,700 ft (9,357 m)
Max speed at war emergency power
394 mph (634 km/h) at sea level
431 mph (694 km/h) at 10,000 ft (3,048 m)
451 mph (726 km/h) at 15,000 ft (4,572 m)
472 mph (759 km/h) at 20,000 ft (6,096 m)
492 mph (792 km/h) at 25,000 ft (7,620 m)
504 mph (811 km/h) at 30,700 ft (9,357 m)
Climb rate
2,200 ft/min (11,18 m/sec) at normal rated power
3,070 ft/min (15,60 m/sec) at military rated power
3,950 ft/min (20,06 m/sec) at war emergency power
Climb time
4,9 min to 10,000 ft (3,048 m)
11,1 min to 20,000 ft (6,096 m)
Service ceiling
32,000 ft (9,754 m)
Endurance at 1,000 ft/305 m
1,04 hr at max speed
1,81 hr at 90% max speed
3,44 hr at 75% max speed
4,26 hr at 60% max speed
Max range at 1,000 ft/305 m
910 mls (1,465 km) at 236 mph (380 km/h) average speed
Take-off run
930 ft/283 m (calm)
680 ft/207 m (15 kn/28 km/h wind)
520 ft/158 m (25 kn/48 km/h wind)
Stalling speed
105 mph/169 km/h (full load without power)
46 mph/74 km/h (full load with military rated power)
Weights
16,802 lb (7,620 kg) normal loaded
18,917 (8,581 kg) max overload
15,542 lb (7,050 kg) landing weight
DIMENSIONS
Overall width
13 ft 6 in (9,90 m) across tailplane
31 ft 9 in (9,68 m) across airscrews (diagonal)
36 ft 5 in (11,10 m) square
Length
28 ft 7ď in (8,72 m)
Height
14 ft 9 in (4,50 m)
Information from "Naval Fighters # 21 - Chance Vought V-173 and XF5U-1 Flying Pancakes", Steve Ginter Books, 1992.
Transparent canopy
Detailed interior
Rotatable propellers
CHANCE VOUGHT XF5U-1
FLYING
PANCAKE
The real thing...
And the model
C 2001 E. ZARKOV
MADE IN BULGARIA BY REQUEST OF MOSHE LEMER, ISRAEL
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