Chance Vought Flying Flapjack projects - V-162 V-173 V-173 VS-315 XF5U

[mboeller]

I read somewhere, I don't recall where, a modern technical assessment of the XF5U.

Did you mean this PDF:

http://www.eaach1.org/Design/DGIIcom3.pdf

 

[taildragger]

No, I haven't seen that before, but the article makes it clear that vibration was a major problem encountered during ground testing. The account I remember was more of an engineering analysis and speculated that the program would have run into vibration problems that were beyond the current state of knowledge had it progressed to flight testing. It sounds like Vought actually got a pretty good taste of these and that they may have been a major reason for the project's termination.

 

[robunos]

There's a rather good article about the V-173 and XF5U-1, in the November and December 1975 issues of 'Aeroplane Monthly', written by Art Schoeni.
I wont post the whole article, obviously, but here are some pertinent quotes and images :-


"In a design competition at NACA in 1933
he [Zimmerman] designed a circular-wing aeroplane
that was to fly at high speed and yet
hover like a helicopter.
His design won the competition with its
aerodynamic excellence and sound engineering.
However, NACA rejected the idea for further
development because it was "too advanced".


As originally planned, the little aircraft was to
carry three passengers lying prone to promote
streamlining, changing to upright position in flight.
The idea was incorporated in a US patent
procured by Zimmerman in 1938,
but he had abandoned it before
then as being marginal in comfort.

The design called for the ultimate
lighter to have large props with
helicopter-like flapping blades that
would support it in hovering flight.
Thus there was talk of an
aeroplane that could take off vertically
and fly forward at 500 m.p.h.

Before Guyton made the V-l75’s
first flight, full-scale wind tunnel tests
at Langley Field indicated that the
high induced drag of the low aspect
ratio wing would be partially com-
pensated for by the interaction of the
large props rotating in opposite direc-
tions ahead of the wing. Wing tip
vortices which cause loss of lift on
conventional wings were nullified by
having each propeller rotating counter
to the vortices.

vibration in the cockpit was a per-
sistent problem. This was caused by
resonant frequency between the pro·
pellers and the nacelle structure,
which Zimmerman greatly alleviated
by installing vibration dampers on
the propellers. The problem was not
met in the heavily constructed XF5U-1,
but it led to development of articu-
lated propeller blades in the fighter
to avoid the non-symmetrical airflow
at high angles of attack.

"Being a former naval carrier pilot,
I was keen for the idea of vertically
landing a 500 m.p.h. fighter to a hook
installation on a cruiser or battleship."
[Boone T. Guyton, V-173 test pilot.]

Full-scale wind tunnel tests of the
Pancake were run in September 1941,
at NACA’s Langley Field, Virginia.
Following successful completion of
these, the Navy asked Vought to
design and build two military versions
of the VS-515, which were designated
the XF5U-1. One would be a flight test
aircraft and the other for static testing
in the laboratories.

completed June 7. 1943. By November
it was decided that the interim propellers
on the XFSU-1 would not do,
and that propellers with articulated
or "flapping" blades would be
required.

Gear box problems in the big right-
angle. drive shafts to each propeller
had negated the chance to fly the
XF5U-1 safely from any airfield other
than Muroc. The quarter-million dollar
price tag on a test programme also
was a factor—the Navy preferred to
spend the money on jet aircraft. The
complicated shafting and gear boxes
developed by Vought engineers
presented problems that might. have
hampered the project anyway. Other
turboprop projects of that era also
were having gearbox trouble.

The original propellers installed on
the XF5U-1 lighter were conventional
Hamilton Standard Hydromatics,
similar to those on the F4U-4 Corsair.
When it was discovered that flapping
blades would be required to avoid
vibrration by unsymrnetrical airflow
and to resist heavy loads when flying
at high angles of attack, Zimmerman
had a problem.
The new props were de-signed by
Zimmerman with Vought engineers’
help and built by Vought. "For a time
it appeared the project would have
to be abandoned," Zimmerman said,
"but after a desperate weekend of
work I came up with a design using
two pairs of teetering blades, similar
to the Bell helicopter rotor, one pair
mounted ahead of the other to form
a four-bladed propeller"

Vought's machine was expected to
achieve a speed range from 40 to 425 m.p.h
with the original engines, 20 to 460
m.p.h. with water injection engines,
and 0-550 m.p.h. with gas turbine
powerplants.

Guyton and William Millar, another
company test pilot later killed in an
F7U-1 Cutlass crash, made numerous
taxi tests in the XF5U-1. On one
occasion it lifted briefly off the runway,
a common occurrence on early
test runs."




In the PDF posted by mboeller, above, it's stated that the XF5U-1 was scrapped at Edwards, whereas Schoeni says that the XF5U-1 never went to Muroc, as it then was, instead being scrapped at the Vought plant.
Likewise the PDF says that the V-173 originally flew with a prone pilot arrangement, however Schoeni makes no mention of this, and I've not seen any images of the V-173 with a prone cockpit, other than the one from the 'Aeroplanes Vought' book, (available online at http://celticowboy.com/AV2/index.htm) posted below.


cheers,
Robin.

 

[Johnbr]

Here is a cutaway.

 

[AeroFranz]

Robunos,


thanks for taking the time to post parts of the article. I have been trying to figure out if there is actually truth to the widely reported statements of reduced induced drag thanks to counter-rotation of the props. In the book "Radical wind tunnels" the assertion is made that wind tunnel tests showed little or no difference with models having either sense of rotation. I need to find the relevant NACA paper on NTRS...

 

[Sundog]

Robunos,


thanks for taking the time to post parts of the article. I have been trying to figure out if there is actually truth to the widely reported statements of reduced induced drag thanks to counter-rotation of the props. In the book "Radical wind tunnels" the assertion is made that wind tunnel tests showed little or no difference with models having either sense of rotation. I need to find the relevant NACA paper on NTRS...

It would seem considering the the size of the propellers to the wing, they would dominate the flowfield, regardless of rotation. I think I would be more concerned with their effect on alpha, more so than induced drag.

However, they may have reduced induced drag at higher alpha simply be energizing the airflow at higher angles of attack. Or to put it another way, at higher angles of attack, propulsive lift relieves the wing of having to lift as much, thereby reducing induced drag.

Which gets into what I would like to know. Did the propellers flow field effectively make the lift curve of the wing itself flatter but at a higher coefficent of lift than an equivalent planform without being in a propellers flow field? let me know if you run across any lift curve slopes for the models in powered flight. I would also like to know how it was effected based on power/prop pitch settings.

 

[robunos]

This any help?...


"LANGLEY FULL-SCALE TUNNEL INVESTIGATION OF A 1/3-SCALE MODEL OF THE CHANCE VOUGHT XF5U -1 AIRPLANE"




http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20050019375_2005009856.pdf



"The results of investigation of a 1/3-scale model of the
Chance Vought XF5U-l airplane in the Langley full-scale tunnel are
presented in this report. The maximum lift and stalling characteristics
of several model configurations, the longitudinal stability
characteristics of the model, and the effectiveness of the control
surfaces were determined with the propellers removed. The propulsive
characteristics, the effect of propeller operation on the
lift, and the static thrust of the model propellers were determined
at several propeller-blade angles."


"The peak propulsive efficiencies for f3 = 200 and f3 = 300
were increased 7 percent at CL 0.67 and 20 percent at CL 0.74,
respectively, with the propellers rotating upward in the center than
with the propellers rotating downward in the center."


cheers,
Robin.

 

[Sundog]

Excellent! Thanks Robunos.

 

[robunos]

I have to say, it's my opinion that any reduction in induced drag/increase in propulsive efficiency was only a bonus of this configuration, and that the main reason for it's use was to allow the use of large diameter proprotor type propellers, to enable hovering and thereby VTOL...


cheers,
Robin.

 

[fightingirish]

Here is a short clip of Stu talking about his involvement in the restoration of the V-173 Pancake.

http://youtu.be/G4svtWctNb4

http://youtu.be/G4svtWctNb4

 

[XP67_Moonbat]

Brief write-up on the XF5U.
http://www.jitterbuzz.com/MAN_1947_01.HTML


And here's a PDF of Modern Mechanix's May '47 piece on Vought's Flying Pancake projects. Love the cutaway graphics! You gotta love these old-school scientific articles! Especially when you can appreciate that no computers were used for the illustrations back then. Those cutaway graphics were done by hand. No CG.
http://www.jitterbuzz.com/manreal/flying_flapjack_mechanix_05_1947.pdf

 

[cluttonfred]

Thanks for the PDF, a wonderful find including the drawings by the great Douglas Rolfe!

 

[hesham]

Hi,


here is the early patent which led to develop the V-173,and and anther patent of 1947 ?.


Lotnictwo 8-2015

 

[Stargazer]

The 1938 patent could be related to the built (but not flown) 1935 prototype, though there are a few notable differences:

 

[hesham]

Thank you for Info Skyblazer.

 

[John Frazer]

Verified, from the book "Radical Wings" that the props did nothing much for it. Slight improvement in drag, at low-speed high-A flight, but that high drag was not present in normal flight. As in most discussions, it haphazardly mixes discussion of cruise and low speed which were two distinct and very different realms, contradicting itself.
The book first talks about the Arup S-2 which impressed them with it's good speed 84 kts on a 37HP engine. It does not go into way they persisted in thinking it needed the props rotating down-at-the-tips as if to counter wing-tip wash-around. It just matter-of-fact states that's what the Navy contracted him and Vought to build, ignoring everything previously established about the Arup having good speed (= good efficiency in the air), while having the silly slow landing speed.
After plainly stating that there was little effect to the down-at-the-tip or flapping-prop configuration, it then matter-of-fact states that's what Vought sought to do with the XF5U -apparently for no good reason.
It did not need the outward-rotating props.

 

[Firefinder]

Found this while digging around for some imagines of the XF5U weapons hardpoints.
Tuft Studies of Chance Vought XF5U-1 Airplane Model

View: https://www.youtube.com/watch?v=5Gj_eFnFzpw&feature=emb_err_woyt

 

[FXXII]

And the roundel is positioned 90 degrees wrongly.

 

[Justo Miranda]

Chance Vought V-173

 

[blackkite]

Hi!

View: https://www.youtube.com/watch?v=vEJQCIJYdK0

 

[Justo Miranda]

Chance Vought XF5U-1

 

[Justo Miranda]

Chance Vought V-173

 

[Justo Miranda]

American Flying Saucers

​

Between 1932 and 1935 the aerodynamicist Charles H. Zimmerman tested several types of low aspect ratio wings (with semicircular wingtips and Clark Y airfoils) in the NACA-Langley wind-tunnel, searching a solution to the Air Flivver problem of stall/spin accidents.

The development of a controlled vortex flow allows the low aspect ratio wing to avoid stalling at exceedingly high angle-of-attack and low speed. Zimmerman progressively reduced the center section in the wing of some scale models until it reached zero, with the wingtips forming a circular planform wing.

Their NACA report nº 539: Aerodynamic Characteristics of Several Airfoils of Low Aspect Ratio (1935) became the basis for the V-173 Zimmer Skimmer design of 1939, with U.S. Navy financing and Chance Vought Aircraft Division-Stratford workmanship.

The prototype Bu Aer no. 02978 was constructed with wood framework, plywood/fabric covering and powered by two 80 hp. Continental C-75 engines driving 16 foot 6 in three-bladed, variable pitch propellers, rotating in the opposite direction. These large propellers demanded a long fixed landing gear gave the V-173 a 22.15 degrees nose-high ground angle. Most of the airframe was the wing, which had an aspect ratio of 1:275, with semi-elliptical leading edge and trailing edge joined at a straight quarter-chord line.

The plane was test flown at Stratford on November 23, 1942 performing a take-off run of only 200 ft. at 29 mph, controlled flight at a 45 degrees angle-of-attack and landing in 20 ft. and 15 mph. The propellers were fitted in the wingtips, retaining the high-pressure air below the wing, actively cancelling the drag tip vortex, and providing uniform airflow over the entire wing, for exceptional ‘parachute lift’ effect.

Engine power was delivered to the propellers via a complex set of shafts with right angle gear drives, and a power cross shaft with over-running clutches, that ran behind the cockpit, connecting the engines gearboxes to ensure both propellers turned in a single engine scenario.

Each horizontal stabilizer acted as both aileron and elevator (ailevator).

Originally the pilot was lying in prone position, to promote streamlining, with glazed panels in the lower leading edge but this was changed to an upright seat because of his marginal comfort.

Chance Vought V-173 technical data

Wingspan: 23 ft. 4 in. (7.11 m), ailevators span: 34 ft. 9 in. (10.6 m), length: 26 ft. 8 in. (8.13 m), height: 12 ft. 11 in. (3.94 m), wing area: 427 sq. ft (39.67 sq. m) max weight: 3,050 lb., max speed: 138 mph, power plant: two 80 hp Continental C-75 fan-cooled engines driving three-bladed airscrews via extension shaft.

Following the defeat in the Battle of Britain, the Germans increased his offensive against the shipping convoys in the North Atlantic. The Luftwaffe used long-range bombers Focke-Wulf Fw 200 C-1 of the I./KG40 based on Bordeaux-Merignac, these aircraft operated out of the range of the shore-based RAF Beaufighters. As a result of enemy air action, the Allies lost 32 merchant ships for the last quarter of 1940 and 88 ships for the first quarter of 1941.

With the loss of the HMS Glorious and the HMS Courageous, the Royal Navy did not have enough aircraft carriers to escort all the convoys and Winston Churchill pressed for an interim solution. In spring 1941, thirty-five merchant ships were to be converted to ‘Catapult Aircraft Merchantman’ (CAM Ships) with the installation of a rocket catapult de 70 ft in the forward deck, to launch surplus Hurricanes. These Hurricat /Catafighters were standard Mk. I fighters, modified with catapult gear as Sea Hurricane Mk.IA.

From November 1941 to July 1943, only eight catapult launches were made from CAM Ships, with six enemy aircraft shot down and the loss of one pilot.

The major drawback of the Hurricat system was that, once the interception was completed, the fighter had to be ditched and the pilot would be picked up by the mother ship or by the nearest escort vessel. The average time to pick him up was between four and six minutes. For artic operations, the survivability was improved with the fitment of one Type K single-man dinghy. The CAM system was dropped when some merchant ships were converted in small escort carriers (MAC ships) and a new type of fighter, fitted with catapult spools and arrester hook, was developed as Sea Hurricane Mk.IB, for MAC operation.

By the end of October 1941 the British Admiralty decided to reinforce the defenses of Singapore by sending to the Indian Ocean the powerful Force Z formed by the aircraft carrier HMS Indomitable, the 44,500 tons battleship HMS Prince of Wales, the 38,000 tons battlecruise HMS Repulse and four destroyers. Unfortunately, the Indomitable was damaged in Kingston-Jamaica and the Royal Navy decided not to replace it with the HMS Hermes based at Ceylon because its speed was only 25 knots and the objective of the Force Z was the destruction of the Japanese battlecruisers that exceeded the speed of 30 knots, using the advantage of radar during night battles.

On December 10, the British vessels were steaming off Malaya in an attempt to intercept the Japanese invasion fleet heading for Patani, Kota Bharu and Kuantang on the east coast of Malaya. Near 130 nautical miles at the north of Singapore the Force Z was attacked during 140 minutes by 112 airplanes of the Imperial Japanese Navy based at Saigon: 34 Mitsubishi G3M Model 21 bombers of the 753rd Kokutai, 52 G3M Model 22 torpedo planes of the 701st Kokutai and 26 Mitsubishi G4M torpedo planes of the 751st Kokutai managed to sink the two capital ships before the fighters Brewster B-339E of the 453 Sqn RAAF based at Sembawang-Singapore arrived over the battle area. The story would have been different if the 25 aircraft of the HMS Hermes could have intervened.

By the end of 1941, the U.S. Navy had just entered a war in which the German and Japanese bombers had demonstrated great efficiency in destroying all kinds of Allied ships. It was necessary to protect the few warships that had survived the Pearl Harbor disaster against airstrikes, but the Pacific Fleet only had three aircraft carriers and the MAC ships were too slow to be used in combat operations.

The battleships and battlecruisers used to transport small reconnaissance floatplanes Curtiss SOC-3 and Vought OS2U-1 that were launched from steam catapults and could be recovered after each mission, but a fighter fitted with floats would have been an easy prey for the Mitsubishi Zero-Sen.

The U.S. Navy needed an air-superiority fighter with extreme short-take-off-and-landing (STOL) capabilities, slow-flight performance, and hovering ability, able to operate from the rear decks of the warships, but this airplane did not exist until the BAE Sea Harrier entered service in April 1980.

On January 19, 1942 Vought-Sikorsky submitted to the U.S. Navy the VS-315 proposal for a 425 mph STOL fighter. In February, the Navy requested a 1/3 scale wind-tunnel model, the VS-315 receiving the official designation XF5U-1 on September 10, 1942 and the wooden mock-up VS-313 was finished in June 1943.

The projected naval fighter had a lightweight aluminum structure with Metalite (balsa/aluminum sandwich) skin, 20 times as much power that the V-173 and increased top speed/landing speed ratio from a typical 4:1 to 10:1. Using two Pratt & Whitney R-2800-7 radial engines, rated at 1,350 hp. each, was expected a landing speed of 40 mph, a top speed of 425 mph. and a zero-roll take-off with a 25-knot headwind.

Powered by two 1,600 hp. P&W R-2000-2(D) turbo-supercharged engines with water injection, it was expected to reach 20 to 460 mph and 0 to 550 mph using two General Electric T31-GE-3 turboprops with 2,300 shp+600 lbf residual thrust and greater power-to-weight ratio. The proposed turbine-powered model was designated VS-341. With sufficient power, both rotors could generate more lift than weight for vertical take-off and landing operation, just keeping up with the warship forward speed. Powered by two turboprops, the airplane would hover motionless hanging under its rotors like a helicopter.

On July 15, 1944, the Navy signed a contract for two prototypes: one for static testing (Bu Aer nº 33959) and one (Bu Aer nº 33958) for flight evaluation. The XF5U-1 was completed on June 25, 1945 with retractable landing gear, catapult bridle hooks and arresting hook for carrier operation. Their R-2000-7 engines were buried into the wing, two circular air intakes with cooling fans were placed in the wing leading edge and four air exit flaps were opened on both upper and lower wing surfaces.

A pair of Hamilton Standard Hydromatic propellers from two F4U-4 Corsair fighters were installed, but the vibration tests performed on June 29, 1945 showed excessive mechanical vibration between the engine-propeller shafting, gear boxes, and airframe structure.

It was necessary to develop a new type of propellers, with articulated blades, like those used on helicopters. Each rotor consisted of two pair of wooden blades, one mounted ahead the other, that could flap fore and aft to alleviate the vibration at a high angle-of-attack, but the articulated rotors were not available until 1947.

The airplane was taxi tested on February 3, 1947 at Stratford, Connecticut, but, again, showed destructive cyclic forces and heavy loads that had not been acceptable with conventional rigid airscrews. Full flight tests were scheduled for December 1948 at Edwards AFB, but the development of the two-speed gearboxes delayed the program and the U.S. Navy suddenly cancelled the contract on March 17, 1947, with orders to destroy the prototype.

Chance Vought XF5U-1 technical data

Ailevators span: 32.5 ft. (9.9 m), width at the prop tips: 36.3 ft. (11.06 m), length: 28.6 ft. (8.7 m), height: 14.8 ft. (4.5 m), wing area: 475 sq. ft (42.7 sq. m) max weight: 18,917 lb. (8,569 kg), estimated max speed: 504 mph (811 kph), estimated range: 910 miles (1,464 km), estimated initial climb rate: 3,950 ft/min (1,204 m/min), estimated service ceiling: 32,000 ft. (9,756 m), estimated take-off run: 710 ft (216 m), nose-high ground angle: 18.7 degrees, proposed armament: six 0.50 cal Colt-Browning heavy machine guns of four 20 mm cannons.

The Dark Side​

The official explanation of the Navy was that they could already operate jet fighters from its 98 aircraft carriers. But the irrational decision to destroy all traces of the XF5U is only comparable to the destruction of all Northrop's flying wings produced and, in both cases, there were powerful political reasons.

Year 1947 was incredibly special. Just five days before the cancellation of the program, the doctrine to contain the Soviet expansion was announced to Congress by President Harry S. Truman.

The Cold War had started.

In May 22, the President signed an Act of Congress that implement the Truman Doctrine.

On June 4, the first Mogul balloon was launched, five days later the U.S. attaché in Moscow informed the War Department that the Soviets had begun the serial construction of the Horten Ho VIII flying wing bomber.

In June 26, the U.S. newspapers first began using the term flying saucer.

The Roswell incident occurred on July 8.

In July 26, the President signed the National Security Act (NSA 47) creating the Central Intelligence Agency (CIA) and the National Security Council (NSC).

The first North American F-86 swept wing fighter was flown on October 1, thirteen days later the Bell X-1 experimental rocket plane flew faster than the speed of sound, but it was a record that was kept secret.

In December 30, the Soviet swept wing fighter MiG-15 makes its first flight.

During the invasion of Japan ‘Operation Olympic’, planned for May 1946, the Allies expected to suffer a high number of causalities by the suicide jet bombers of second generation Kawanishi Baika (740 kph-460 mph) and Kugisho Ohka 43 (596 kph-370 mph).

The U.S. Navy needed fast interceptors to protect the invasion fleet, but the high fuel consumption, low power at take-off and poor reliability of early jet engines did not make them attractive for use in carrier-borne planes.

On May 28, 1945, the Navy approved a production contract for 100 North American FJ-1 Fury jet fighters. The XFJ-1 prototype was flown on September 11, 1946 powered by one General Electric GE-2 (TG-180) axial flow turbojet rated at 1,730 kgp (3,820 lbf) thrust. The first production FJ-1, with 4,000 lbf Allison J-35 axial flow turbojet, was delivered in October 1947 but only 30 airplanes were built.

On March 10, 1948 one FJ-1 made the first carrier landing in the U.S.S Boxer (CV-21). Five months later the Fury entered service with the VF-5A (VF-51) naval squadron for a jet familiarization program. In May 1949, the VF-51 started an operational training trip aboard the U.S.S. Princeton (CV-37), the results were not good, one of the aircraft was destroyed and the rest were damaged.

The disastrous evaluation led to a quick retirement from active service by July 1949. The Essex-class carrier deck was 862 feet long and the Fury had a take-off run of 840 ft.

The U.S. Navy concluded that slower acceleration by jets during the take-off was not recommended and catapult departures became standard practice.

Vought also offered its VS-340 model in the fall 1944 competition; the design proposal was accepted, and the Navy ordered three prototypes under the denomination XF6U-1 Pirate. The first prototype was flown on October 2, 1946, underpowered by one Westinghouse 24C axial turbojet with 3,000 lbf static thrust, and 30 production aircraft were ordered in February 1947.

The Pirate development was slow, the first production airplane was flown on July 29, 1949 powered by one J 34-WE-30 axial turbojet, rated at 4,224 lbf, with afterburner and excessive fuel consumption rate. The aircraft was entirely inadequate for carrier operation, because its low performance and 0.3:1 thrust-to-weight ratio.

The introduction to squadron service of the McDonnell FH-1 Phantom on August 11, 1947 could have solved the problem. The FH-1 was a very safe airplane, powered by two J 34-WE-30 turbojets, with 370 ft take-off run and 360 ft took-off run. The Phantom could fly at low speed for carrier operation but had a top speed of 485 mph only, against the 647 mph of the MiG-15 Soviet fighter. All the 62 airplanes produced were taken out of service in 1949.

The Soviet Union started the first major crisis of the Cold War with the Berlin Blockade on June 24, 1948.

Confronted with the Chinese revolution, the 1948 presidential election and the end of American atomic monopoly in 1949, the Truman administration moved to escalate its containment doctrine and quadrupled its spending on defense.

On July 29, 1948, the President approved construction of five supercarriers, with 68,250-ton displacement and 1,090 ft (330 m) length, able to carry a group of large nuclear bombers, the most effective weapon of the day, and a new type of swept wing fighters of the F-86 class.

The construction of the USS United States (CVA-58) started on April 19, 1949 with an estimated cost of US $ 189 million, but the USAAF managed to cancel the entire program in favor of the B-36 intercontinental bomber, at the cost of US $ 5.76 million for each plane.

With this operation, the Strategic Air Command kept its monopoly on nuclear weapons delivery until the approval by the Congress of the new USS Forrestal (CVA-59) in April 1950.

During that time, the US Navy was forced to operate with the Essex and Midway-class carriers, straight wing fighters and Lockheed P2V-3C Neptune medium bombers.

After the failure of the Pirate and trying to keep alive its 15 years of work project, Zimmerman proposed to Vought an increased performance version of the XF5U, (labelled as Jet Skimmer in the specialized literature) powered by two Allison J33-A-23 turbojets, rated at 5,400 lbf with water injection. Those huge centrifugal engines, with 50.5 in (128.3 cm) of diameter could not be installed in any naval fighter in service, but they could be buried into the wing/body of the XF5U.

Doubling the power of the F-80C Shooting Star fighter and flying without the extra drag and weight of rotors and gearing, the new plane might have been a 20 per cent faster than the XF5U, but still inferior to the MiG-15 top speed, because the drag penalty induced by their wingtip vortex.

The Jet Skimmer would have retained some of the STOL of the XF5U capability thanks to the special design of its exceptionally low aspect ratio wing. Fitted with the original landing gear and tail hook equipment it might have been able to operate from any escort carrier, but Vought preferred to continue with the development of the V-346 Cutlass, a decision that the Navy would soon regret after the loss of 78 airplanes in accidents.

 

[steelpillow]

Thank you Justo for your wonderful history.
It occurs to me that the Douglas F-4D Skyray is almost a swept-wing version of these planes, having a large area packed inside a span not much greater than its root chord, and rounded broad-chord tips. Its origins lie in the Lippisch delta work that I mentioned above, but it morphed into a kind of halfway house. It is thus an excellent example of the common design principles which apply to both planforms.
It set a world speed record, was capable of supersonic speeds in level flight, had excellent manoeuvrability and was considered outstanding.
But, other than being carrier-based and hence an appropriately adequate STOL performer, I have no information on its STOL and low-speed/stall characteristics. The low wing loading would certainly have helped, but I'd love to know more about the aerodynamics of this almost-flapjack.

 

[hesham]

From Interavia 1959.

 

[hesham]

From Ailes 6/1946,

here is a hypothetical drawing to a Vought Flapjack.

From Aeroplane 1946.

 

[hesham]

From NASA;

https://ntrs.nasa.gov/api/citations/downloads/20200002436.pdf

 

[hesham]

From Air Classics 2022/6.

 

[Dick]

omg I didn't know Dark Skies did a video of this plane. I love this plane an Zimmerman's work on low aspect wings

 

[foiling]

Chance Vought V-173

Superb art.

 

[hesham]

I don't remember the source.

 

[hesham]

From this Russian magazine.

 

[John Frazer]

It appears to be a myth, not founded in experience or substantiated by anything from NACA or from Zimmerman, that the "swirl" imparted by the outward & down at the tip rotation of the props aided it in any way.
It's certainly not true that it was responsible or helpful in any way for it's super-slow performance: Any theory that says so, must then account for the very much experience from very many other very-low aspect-ratio planes that had stall-proof, super-slow performance without that extra complexity. Usually, those saying that the overly complex situation with the props was necessary, have never heard of the Arups, the Nemeth, the Eshelman, the Farman 1020, the Little Bird, the Facetmobile.
It got it's super-slow, stall proof performance solely from the very-low aspect-ratio planform.
The flappy oversized props did _not_ counter the wing-tip vortices while flying very slowly with his "A" since it flew very well using the "parachute lift" effect from the huge wing-tip vortices.

It's also not true that the situation with the props helped with efficiency at cruise. It's unlikely that it can do both, help very low speed and help at cruise, and very many others of the very-low aspect-ratio type have been sleek and quick on available power without those props. It didn't seem to help either at low speed or at cruise & higher speeds. The oversized props probably hindered its speed, compared to more normal 80 hp props, and the extra complexity of the interconnection required by the wing-tip location of the props effectively killed it.
It's not true at all that it couldn't have flown well with jets. It's not true that it needed the wing-tip location of the props to "counter" the vortices.

 

[GTX]

View: https://www.youtube.com/watch?v=p9eSogiYNJ8

 

[Stargazer]

Development of Charles Zimmerman's original "Flying Pancake" (from Air Trails, March 1952):

 

[NEST OF DRAGONS]

I saw in a video that the Skyrocket, a twin-engined pre-WW2-airplane where the props passed very close to each other, had difficulties when the props turned towards each other. It lost the efficiency of the mid-section of the wing. When they made the props turn away from each other, the problem was solved.

I think to recall that the V-173 had also tests of the props turning to each other and away from each other. Any info known about the difference in performance for the V-173?

 

[Scott Kenny]

I saw in a video that the Skyrocket, a twin-engined pre-WW2-airplane where the props passed very close to each other, had difficulties when the props turned towards each other. It lost the efficiency of the mid-section of the wing. When they made the props turn away from each other, the problem was solved.

That also happened to the P-82 Twin Mustang. The props coming down onto the center wing completely negated the lift of the center wing!

I think to recall that the V-173 had also tests of the props turning to each other and away from each other. Any info known about the difference in performance for the V-173?

Not that I've seen, but I also haven't done any deep dives for it.

 

[Маска]

NACA V-173.

 

[Маска]

V-173

 

[Маска]

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