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Yes, this is of course one of the most celebrated characteristics of the steep delta wing. Lippisch especially long preferred this form, though it appeared most famously in the Vulcan V-bomber.
Flying Flapjacks
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Yes, this is of course one of the most celebrated characteristics of the steep delta wing. Lippisch especially long preferred this form, though it appeared most famously in the Vulcan V-bomber.
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.
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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.
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.
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The complex internal ducting reminds us of Avrocar. AVRO of Canada sketched dozens of possible supersonic variants, but only built a couple of simple VZ-9 prototypes to demonstrate hover performance. They proved unstable in hover and the project was cancelled.
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Fly-by wire and 3D printed gas channels might allow a second chance. If a shuttle stack can launch without doing cartwheels-then modern tech could smooth out issues here. Remember-the very conventional F-16 may also have been beyond what Avro could do...and F-104 might have used fly-by-wire had it been available. I think people are put off from lenticular designs due to their retro looks-but that never stopped Musk.
If you were to revive it then surely you're talking a turbofan-based powerplant and electric puller-props that could gimball to give you active thrust-steering. But for what purpose? Flat designs would not be comfortable to ride in.
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Gimballing props is probably a bad idea. The Coriolis and related forces in moving an axis of rotation can be huge. You can get away with it on a small autogyro, but for higher-powered machines helicopter-style cyclic pitch control is the traditional route, and with careful design the actuators still require very little power.
But I am unclear what your turbofans are for; additional thrust, hybrid-power electricity generation, or what?
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Any thoughts must be speculative, but here's my two penn'orth:
Winglets could have helped a little, but only because they offered greater span to play around in. There are several standard things that can help:
- Higher speed. For example the inefficiencies of the F-104 Starfighter wing disappeared once it was flying supersonic.
- Greater span, whether achieved directly, or indirectly via winglets or outboard horizontal stabilizers (OHS). OHS may be seen on the Vought designs and on the short-span SpaceShips One, Two and Three.
- Tailoring the aerofoil across the span to achieve a bell-like lift distribution curve. This minimises the induced drag from tip vortices, and also minimises structural stresses, at the expense of slightly increased area. Typically the tips are washed-out with reduced, even slightly negative AoA, and the aerofoil is thinned down and/or given leading-edge droop. This is a classic solution even if you have a tail and is evident on many types, such as the Supermarine Spitfire.
- Introducing a cambered aerofoil in place of the symmetrical ones usually chosen for these flapjacks. This improves the efficiency of the whole wing, but impacts stability. The symmetrical type is stable (or neutral) in pitch, whereas a cambered aerofoil is unstable. The tailoring described above, especially tip washout, can restore any lost stability. This was Reimar Horten's approach. Another compromise is to adopt positive camber for the main area but negative camber for the rear section; this was favoured by GTR Hill, but for a flapjack it loses the advantages of spanwise tailoring.
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Perhaps a layered approach to lenticular designs. A standard, modernized Avrocar approach with one engine unit—-but a torus like intake feeding into a second jet once airborne. The exhaust terminates into something that looks a bit like a linear aero spike but with a ramjet “collar” faired in…with perhaps a vertical fin(s) to bite into the slipstream for thrust vectoring rudders.
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I suspect the Avrocar was such an unstable failure because it had a cambered cross-section and was therefore aerodynamically unstable in forward flight. Its hovering problems were also in large part down to the same ignorance and lack of a skirt that bedevilled Cockroft's first hovercraft. Combine the two issues with an utter lack of fly-by-wire tech and, once it began to pick up any kind of forward speed, whoops!
Its lift-cum-propulsion-cum-control system all round the rim was in some ways analogous to a helicopter, though with lower mass flow and hence lower efficiency - not that helicopters are exactly renowned for their efficiency anyway, while such ducted or blown systems have seldom in practice achieved the thrust levels obtained in the lab and usually proved to need such powerful, large and heavy engines as to defeat any other advantages.
It would be interesting to stick a truly symmetrical, zero-camber body around the lift fan from an F-35C, forget hovercraft and high-speed flight modes, and see if the rim system can at least offer helicopter-like performance and get one-up on the Moller Volantor. That might even offer useful applications, such as safe VTOL close to vertical surfaces like buildings, cliffs and sinkholes.
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To prevent Twilight Zone Movie tragedies. I would want a separate jet for forward flight.
Now, one of the things I saw was a drone on wheels that could “drive” up a wall…small thing though…I don’t know that if it can scale…
Now, one of the things I saw was a drone on wheels that could “drive” up a wall…small thing though…I don’t know that if it can scale…
Late in 1951 John Frost made a proposal for a proof-of-concept saucer-like flying vehicle. Early in 1952 the A.V. Roe Special Projects Group was formed to investigate the Frost ideas.
On February 7, 1952, the Group distributed an internal document titled ‘Description and Thoughts on the Turbo Disc’ (a simple gas turbine halfway between a ram-jet engine and centrifugal engine), Frost also submitted the design to the engineering department of McGill University.
The radial-flow turbojet designed by the Frost team had twenty feet of diameter, 42,000 lbf minimum thrust at low pressure and an outstanding power-to-weight ratio of 1.73 to 1.
The horizontal Pelton-wheel turbine had a large multi-stage centrifugal compressor with the rotor blades mounted on the inner disc ring and the stator blades in the outer disc ring. The separate combustion system consisted of several combustion chambers with individual burners and nozzle guide vanes distributed in a radial pattern between the ribs of the vehicle.
This work led to the first design named Omega project, with elliptical planform, 36 ft wingspan, 40 ft overall length and 1 to 7 aspect ratio. It was proposed to control the vehicle by altering the direction of thrust forces.
The vehicle had twenty air-intake slots mounted in the nose, the new pancake engine was designed as an integral part of the airframe and the jet thrust exited from around the entire rim of the engine.
About three-fifths of the jet exhaust flow through a multiple jet-pipe assembly that direct the flow of gases in a rearward direction from the sides of the airframe for propulsion and the remainder is ejected from the trailing edge through ten deflector vanes comprising elevons and trimmers providing control in yaw, roll and pitch.
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On April 2, 1955, the USAF signed Avro contract Nº AF33 (600) 30161 for the Project 1794. The contract specified analytical investigations to determine the performance capabilities of a flat VTOL all-wing aircraft of circular planform employing jet control. The areas for analysis were defined as:
Air Cushion Effect
Stability of multi-engine configuration
Air intake and gas exhaust system test
Aircraft performance, stability, and control
Radial-flow engine feasibility
Aerodynamic tests with 1/6 and 1/40 scale models were conducted at Wright-Patterson and M.I.T. wind tunnel facilities. Tests of speed, transition control, pitch control, jet thrust, intake flow, ground position and angle of attack were completed on June 14, 1956.
An attempt was made to theoretically calculate the Ground Effect, but theory does not explain observations sufficiently accurately and no tests of radial-flow engine feasibility have been carried at the end of the program.
A low-speed research vehicle was proposed to investigate stability, control systems and Air Cushion Effect, before development of a supersonic operational aircraft.
This planned prototype had 21 ft 6 in (6.55 m) of diameter, 4 ft (1.2 m) height and was powered by eight radially mounted Armstrong-Siddeley Viper A.S.V. 8 turbojets, with 4,188 lbs. thrust each, radial diffuser ducts and Coanda peripheral ring.
The final development aircraft had a turbo-ramjet propulsion system with one Lundström compressor/turbine powered by three Viper A.S.V. 5 turbojets, a single-stage axial impeller and 144 flame tubes. The planned aircraft had 35.3 ft (10.75 m) of diameter, 5.35 ft (1.63 m) height, Mach 3.0 top speed and 94,000 ft ceiling.
On November 4, 1955, Avro Canada proposed the PV.704 project to develop the radial-flow engine to eliminate any delays in the development of the Project 1794 propulsion system.
In the PV.704 power plant the incoming air sucked through the upper and lower intakes was fed into the hollow cylinder of Lundström turbo-rotor, pressurized by means of the four-stage upper and lower impellers and directed towards the peripheral air intakes of six radially mounted Viper A.S.V. 8 turbojets. Partial flow of compressed air proceeds radially to 24 peripheral combustion chambers and finally expelled through 96 flight control shutters.
On September 26, 1957, the U.S. Army approached Avro with a request for an Air Cushion Effect ‘flying jeep’, by March 1958 the Special Projects Group designed a modest subsonic circular aircraft called Avrocar.
Thrust of their three turbojets were used for turning the Turborotor, a 124 blades fan with 5 ft of diameter, to provide vertical lift. Partial thrust was ducted to periphery flaps and exhaust nozzles which provided stability and control.
In May 1958, USAF signed contract AF33 (600) 37496 for the construction of the mock-up and one proof-of-concept demonstrator. A second prototype was commissioned in March 1959.
On October 7, 1959 tethered flight tests of the noisy prototype VZ-9AV (59-4975) indicated that one-third of the thrust was being lost to exhaust inefficiencies. This meant the aircraft would be incapable of hovering out the Ground Effect.
With enough power even a brick can fly, but the Avrocar never had the power to do so. Thrust losses required a complete re-design, a costly decision that crippled the entire program.
During the first free flight conducted in May 1959 the Avrocar never exceeded one meter off the ground, but the lack of control flight was its undoing.
It was discovered that the prototype was inherently unstable in forward flight, with rapid and unpredictable swings in pitch and roll axes, a control problem called ‘hub capping’.
The development contract was completed in December 1961 and the project was discontinued.
VZ-9AV technical data
Diameter: 18 ft (5.49 m), thickness: 3.6 ft (1.1 m), height: 7.7 ft (2.34 m), wing surface: 254 sq. ft, estimated top speed: 300 mph (482 kph), estimated ceiling: 9,840 ft (3,000 m), empty weight: 2,992 lb. (1,360 kg), max weight: 5,639 lb. (2,563 kg), power plant: three Continental J69-T-9 turbojets with 927 lb. static thrust each, estimated range: 25 miles with ten-minutes hovering capability.
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I think "planned" is a little over-optimistic. "Dreamed-of" would be more accurate. We should not forget Pye Wacket, the US project for a Mach 3+ lenticular air-to-air missile, contracted to Convair:
Wikipedia says that the lenticular design was expected to have good control characteristics at extreme AoA, a suggestion which baffles me and I must wonder whether the mistake is theirs or the USA's; perhaps it was just less appalling than a wedge at higher AoA than the taper angle, and NASA knew of none better at that time. Of course it didn't, nor at any other speed.
I seem to recall once seeing some photos on the NASA web site or similar, of later wind tunnel models which had grown a stabilising twin-boom tail (which would also have been unhappy at extreme AoA), but I can't find them now, so maybe my memory is failing me.
I suppose the main difference between the dreamed-of Avrocar and Pye Wacket was whether the payload was a pilot or a nuke. That and the Avrocar's rim drive.
Later NASA developed some rather more practical lifting bodies, which helped pave the way for the Shuttle.
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Yes and no. I recall it as just a conventional fixed pair of booms with a stabilizer across the middle. The outboard horizontal stabilizers (OHS) of SpaceShips One/Two/Three are a bit different, though both designs are variations on the same fundamental solution to aerodynamic stability, when you have a rocket exhaust where you wanted to put the tail support structure.
But as I said, don't trust my memory on Pye Wacket
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Bono briefly studied a lenticular spaceplane. There's a note and illustration at http://www.astronautix.com/b/bonosaucer.html
I don't know whether it launched vertically, but presumably it landed horizontally and so qualifies as a "flying flapjack", at least during re-entry and landing. Whatever its flight regime, it turned out less efficient than a conventional space rocket.
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Outstanding images.
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From Aviation magazine 1974.
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That photo looks as if it might be a scale model test aircraft. The profiling of the nose and "canopy" seem a bit crude.
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From Aviation magazine 1975.
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This was the B.Ae P.1214, effecively a design study for the P.1216. Mike Pryce includes some info on it in his book on the latter (published by our Blue Envoy). It is not really a flapjack so much as a forward-swept wing with twin tailbooms and a deep centre section. In the drawing Mike reproduces, the trailing edge is moved further forward to reduce problems of rear jet efflux in the vertical/transition modes.
Here's the Popular Mechanics edition with the article: https://ia601302.us.archive.org/9/items/PopularMechanics1984/Popular_Mechanics_06_1984.pdf
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I think every aviation enthusiast goes through three phases of the P.1214:
- That can't be real!
- Wow, it actually was real!
- ...maybe it shouldn't have been real.
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From Aeroplane 1946.
Attachments
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Attachments
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That link is broken. Try this one:
Last edited:
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Nik
ACCESS: Top Secret
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Could any 'Flying Flapjack' STOL have been crafted in time for the Atlantic convoys' protection instead of those near-kamikase 'HurriCats' ? So before the 'escort carriers' finally came off slip-ways ??
If STOLs only needed two tennis-courts and an anti-skid net to 'land-on', they'd change the paradigm...
Yes, the 'What-If' of such 'Flying Saucers' briskly beating up startled Condors and strafing U-Boots appeals...
FWIW, an uncle tended RADAR aboard a sub-hunter working out of Liverpool. As depth-charging and/or ramming would reliably derange the oft-cantankerous [REDACTEDS], they logged no kills, but many 'assists'...
If STOLs only needed two tennis-courts and an anti-skid net to 'land-on', they'd change the paradigm...
Yes, the 'What-If' of such 'Flying Saucers' briskly beating up startled Condors and strafing U-Boots appeals...
FWIW, an uncle tended RADAR aboard a sub-hunter working out of Liverpool. As depth-charging and/or ramming would reliably derange the oft-cantankerous [REDACTEDS], they logged no kills, but many 'assists'...
John Frazer
I really should change my personal text
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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.
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.
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