The Doak VZ-4 (or Doak Model 16) was an American prototype Vertical Takeoff and Landing (VTOL) aircraft built in the 1950s for service in the United States Army. Only a single prototype was built, and the U.S. Army withdrew it from active trials in 1963.

Edmund R. Doak, Jr., a self-taught engineer and vice president of Douglas Aircraft Company, founded Doak Aircraft Company in Torrance, California, in 1940. The company grew to 4,000 employees during World War II, with subcontracts from every major American aircraft manufacturer. These included molded plywood fuselages for trainers such as the AT-6 and Vultee BT-13, and doors, hatches and gun turrets for a multitude of aircraft.

Doak proposed a VTOL aircraft to the U.S. Army's Army Transportation and Research and Engineering Command at Fort Eustis in Newport News, Virginia, in 1950. He touted the aircraft as able to take off and land in a small area, hover and loiter over a target area, and fly backwards like a helicopter without the noise and vibration of a helicopter, while also having the horizontal cruising ability, high speed, wing-mounted weapons, and mission flexibility of a conventional fixed-wing fighter aircraft. Knowing that a Soviet attack on airbases would interdict takeoffs and landings by conventional aircraft, the Army found Doak's proposal attractive, and on 10 April 1956, it awarded Doak a contract to produce a single prototype for use as a research aircraft.

The aircraft, designated the Doak Model 16 by the Doak company and assigned the serial number 56-9642, was originally powered by an 840 shp (630 kW) Lycoming YT53 turboprop engine mounted in the fuselage, later replaced by a 1,000 shp (750 kW) Lycoming T53-L-1 turbine. The engine drove two wingtip-mounted fiberglass tilting ducted fan propellers through a "T" box on the engine that transmitted power to the propellers via a 4-inch (102-mm) aluminum tubular shaft and two smaller shafts. Each propeller was 48-inch (1.22-meter) in diameter and the duct outer diameter was 60-inches (1.52-meter)). The fans were positioned vertically for takeoff and landing – with a rotation speed of 4,800 rpm required for liftoff – and rotated to a horizontal orientation for horizontal flight, the first time this VTOL propulsion concept was tested successfully. The aircraft had metal wings and a metal tail. To save weight, the aircraft originally was constructed of uncovered welded steel tubing, but after it was found that the open frame interfered with forward-speed tests, molded fiberglass was installed over its nose section and thin aluminum sheeting over its aft fuselage. It accommodated a two-person crew, with a pilot and observer seated in tandem in the cockpit. The pilot used a standard stick and rudder to control the aircraft. Its landing gear were taken from a Cessna 182 Skylane, its seats from a North American P-51 Mustang, and its duct actuators from a Lockheed T-33 Shooting Star.

Flight testing began at Torrance Municipal Airport, and Doak completed several tests by 1958. The Model 16 hovered for the first time on 25 February 1958, and the first transition from vertical to horizontal flight (and back again) took place on 5 May 1958. Although the prototype generally was successful, its short takeoff and landing performance was less than hoped for and it displayed a tendency to nose up while making the transition from vertical to horizontal flight.

Doak's engineers believed that they could solve the prototype's problems, and after taxiing testing, 32 hours of flight testing in a test stand, and 18 hours of tethered hovering, the aircraft was transferred to Edwards Air Force Base, California, in October 1958. It underwent another 50 hours of testing, in which it proved capable with the turbine engine of achieving a maximum speed of 230 mph (370 km.hr), a cruise speed of 175 mph (282 km/hr), a range of 250 miles (403 km), an endurance of one hours, and a service ceiling of 12,000 feet (3,658 meters).

On 20 November 1953, shortly before the 50th anniversary of powered flight, Scott Crossfield piloted the Skyrocket to Mach 2, or more than 1,290 mph (2076 km/h), the first time an aircraft had exceeded twice the speed of sound.

The "-2" in the aircraft's designation referred to the fact that the Skyrocket was the phase-two version of what had originally been conceived as a three-phase program. The phase-one aircraft, the D-558-1, was jet powered and had straight wings. The third phase, which never came to fruition, would have involved constructing a mock-up of a combat type aircraft embodying the results from the testing of the phase one and two aircraft. The eventual D-558-3 design, which was never built, was for a hypersonic aircraft similar to the North American X-15.

When it became obvious that the D558-1 fuselage could not be modified to accommodate both rocket and jet power, the D558-2 was conceived as an entirely different aircraft. A contract change order was issued on 27 January 1947 to formally drop the final three D558-1 aircraft and substitute three new D558-2 aircraft instead.

The Skyrocket featured wings with a 35-degree sweep and horizontal stabilizers with 40-degree sweep. The wings and empennage were fabricated from aluminum and the large fuselage was of primarily magnesium construction. The Skyrocket was powered by a Westinghouse J34-40 turbojet engine fed through side intakes in the forward fuselage. This engine was intended for takeoff, climb and landing. For high speed flight, a four-chamber Reaction Motors LR8-RM-6 engine (the Navy designation for the Air Force's XLR11 used in the Bell X-1), was fitted. This engine was rated at 6,000 lbf (27 kN) static thrust at sea level. A total of 250 US gallons (950 L) of aviation fuel, 195 US gallons (740 L) of alcohol, and 180 US gallons (680 L) of liquid oxygen were carried in fuselage tanks.

The Skyrocket was configured with a flush cockpit canopy, but visibility from the cockpit was poor, so it was re-configured with a raised cockpit with conventional angled windows. This resulted in a greater profile area at the front of the aircraft, which was balanced by an additional 14 inches (36 cm) of height added to the vertical stabilizer. Like its predecessor, the D558-1, the D558-2 was designed so that the forward fuselage, including cockpit, could be separated from the rest of the aircraft in an emergency. Once the forward fuselage had decelerated sufficiently, the pilot would then be able to escape from the cockpit by parachute.

For the operational history of the Skyrocket program, click here.

Its primary mission was to investigate the design features of an aircraft suitable for sustained supersonic speeds, which included the first use of titanium in major airframe components. Douglas designed the X-3 with the goal of a maximum speed of approximately 2,000 m.p.h, but it was, however, seriously underpowered for this purpose and could not even exceed Mach 1 in level flight. Although the research aircraft was a disappointment, Lockheed designers used data from the X-3 tests for the Lockheed F-104 Starfighter which used a similar trapezoidal wing design in a successful Mach 2 fighter.

The Douglas X-3 Stiletto was the sleekest of the early experimental aircraft, but its research accomplishments were not those originally planned. It was originally intended for advanced Mach 2 turbojet propulsion testing, but it fell largely into the category of configuration explorers, as its performance (due to inadequate engines) never met its original performance goals.[4] The goal of the aircraft was ambitious—it was to take off from the ground under its own power, climb to high altitude, maintain a sustained cruise speed of Mach 2, then land under its own power. The aircraft was also to test the feasibility of low-aspect-ratio wings, and the large-scale use of titanium in aircraft structures.

Two aircraft were ordered, but only one was built, completing 51 test flights.

The XB-43 was a development of the XB-42 Mixmaster, replacing the piston engines of the XB-42 with two General Electric J35 engines of 4,000 lbf (17.8 kN) thrust each. Despite being the first American jet bomber to fly, it suffered stability issues and the design did not enter production.

United States Army Air Forces (USAAF) leaders in the Air Materiel Command began to consider the possibilities of jet-propelled bombers as far back as October 1943. At that time, Douglas Aircraft was just beginning to design a promising twin-engine bomber designated the XB-42. Reciprocating engines powered this aircraft but they were buried in the fuselage, leaving the laminar flow-airfoil wing clean of any drag-inducing pylon mounts or engine cowlings. The airframe appeared ideally suited to test turbojet propulsion. Douglas confirmed the feasibility of the concept and the USAAF amended the XB-42 contract in March 1944 to include the development of two turbojet-powered XB-43 prototypes, reduced from an initial order of 13 test aircraft.

The Douglas design team convinced the Army that modifying the XB-42 static test airframe into the first XB-43 was a relatively straightforward process that would save time and money compared to developing a brand new design. Douglas replaced the two Allison V-1710 engines with a pair of General Electric (GE) J35 turbojets (the first American axial-flow jet engines ever used), then cut two air intakes into each side of the fuselage, aft of the pressurized cockpit. Removing the propellers and drive shafts freed enough space for two long jet exhaust ducts. Without any propellers present, there was no chance of striking the blade tips on the runway, so the entire ventral fin/rudder unit of the earlier XB-42's full four-surface cruciform tail was omitted. Douglas compensated for the loss of yaw stability by enlarging the dorsal fin/rudder unit.

Douglas Aircraft was keen to mass-produce the new bomber and the USAAF considered ordering 50. The company was poised to roll out as many as 200 B-43s per month in two versions: a bomber equipped with a clear plastic nose for the bombardier, and an attack aircraft without the clear nose and bombing station but carrying 16 forward-firing .50 in (12.7 mm) machine guns and 36 5 in (127 mm) rockets. Nothing came of these plans. The USAAF was already moving ahead with a new bomber, the XB-45 Tornado, designed from the outset for turbojet power and promising major improvement in every category of performance.

For further information, click here.

XB-42 Mixmaster. Note co-axial propellers.

XB-43 Jetmaster Prototype 1 - glass nose

Twin bubble canopies and glass nose

XB-43 Prototype 2 solid nosecone

The Optica has a loiter speed of 130 km/h (70 kn; 81 mph) and a stall speed of 108 km/h (58 kn; 67 mph).

The Optica project began in 1974 with a company, Edgley Aircraft Limited, formed by John Edgley who, with a small team, designed and built the original prototype. In 1982, institutional investors bought into the project and set up a production line at Old Sarum Airfield in Wiltshire. Over the next three years, the company was built up to full manufacturing capability, the aircraft received UK certification, and the first customer aircraft was delivered. Despite this success, the additional investment necessary for the final phase of full production was not forthcoming, the business went into receivership, and John Edgley was forced out. With new owners, aircraft on the production line were completed, and the Optica entered service.

The aircraft has an unusual configuration with a fully glazed forward cabin, reminiscent of an Alouette helicopter, that provides 270° panoramic vision and almost vertical downward vision for the pilot and two passengers. The aircraft has twin booms with twin rudders and a high-mounted tailplane. It is powered by a Lycoming flat-six normally-aspirated engine situated behind the cabin and driving a fixed pitch ducted fan. Due to the ducted fan, the aircraft is exceptionally quiet. The aircraft has a fixed tricycle undercarriage with the nosewheel offset to the left. The wings are unswept and untapered. The aircraft is of fairly standard all-metal construction, with stressed skin of aluminium.

The aircraft's distinctive appearance has led to it being known as the "bug-eye" in some popular reports.

For the operational history of the Optica, click here.

It was developed from the company's C-119 Flying Boxcar, and was unique in the unconventional use of removable cargo pods that were attached below the fuselage, instead of possessing an internal cargo compartment.

The XC-120 Packplane began as a C-119B fuselage (48-330, c/n 10312) with a point just below the flight deck cut off to create the space for the detachable cargo pod.. The wings were angled upwards between the engines and the fuselage, raising the fuselage by several feet and giving the plane an inverted gull-wing appearance. Smaller diameter "twinned" wheels were installed forward of each of the main landing gear struts to serve as nosewheels, while the main struts were extended backwards.

All four landing gear units, in matching "nose" and "main" sets, could be raised and lowered in a scissorlike fashion to lower the aircraft and facilitate the removal of a planned variety of wheeled pods which would be attached below the fuselage for the transport of cargo. The goal was to allow cargo to be preloaded into the pods; it was claimed that such an arrangement would speed up loading and unloading cargo.

Production aircraft were to be designated C-128. Only one aicraft was built, Though the aircraft was tested extensively and made numerous airshow appearances in the early 1950s the project went no further. It was tested by the Air Proving Ground Command at Eglin Air Force Base, Florida, in 1951, before the project was abandoned in 1952. The prototype was eventually scrapped. The heading photo is a composite of two photos of the one aircraft.

The Fulton FA-2 Airphibian is an American roadable aircraft manufactured in 1946.

Designed by Robert Edison Fulton Jr., it was an aluminum-bodied car, built with independent suspension, aircraft-sized wheels, and a six-cylinder 165 hp engine. The fabric wings were easily attached to the fuselage, converting the car into a plane. Four prototypes were built.

In December 1950, the Civil Aeronautics Administration (CAA) (later to become the FAA) certified one of the prototypes and gave it an 1A11 Aircraft Specification, N74104. Lou Achitoff, was the CAA test pilot. The N74154 is the aircraft that is today in the main building of the National Air and Space Museum in Washington, DC, having previously been on display in the Steven F. Udvar-Hazy Center.

The craft made its debut in November 1946 at Danbury, Connecticut. Financial concerns forced Fulton to sell to a company that never developed it. Only four aircraft had been completed.

The Airphibian took the approach of converting from an aircraft to a roadable vehicle by a conversion process that left aircraft sections behind during road use. The process consisted of removing a three-bladed propeller and placing it on a hook on the side of the fuselage, cranking down support casters, and disengaging lock levers connecting the flight unit to the road unit. The wing and aft fuselage are detached for road use.

In the mid-1990s, one of the surviving Airphibians was restored by Fulton III, along with David Dumas and Deborah Hanson. Later, it was put on display for several years at the Canada Aviation Museum in Ottawa, Ontario, Canada in their main display hall, but in 2009 it moved to the Steven F. Udvar-Hazy Center (annex of the National Air and Space Museum).[6] Since 2022 it has been on display in the National Air and Space Museum in Washington, DC.

In March 1948, following a series of meetings between members of the British Ministry of Supply and the Australian Department of Supply and Development, a specification was issued to cover the design and manufacture of a small high-speed pilotless aircraft for use in the guided weapon development program. This eventually culminated in the Jindivik.

Initially six pilotless and two piloted aircraft were to be built, to be fitted with the Armstrong Siddeley Adder ASA.1 gas turbine engine which provided 1,050 lbst. This engine was a pure-jet development of the Armstrong Siddeley Mamba propeller turbine which powered the Fairey Gannet carrier-borne anti-submarine aircraft.

Design work began at the Government Aircraft Factory (GAF) at Fishermen’s Bend, VIC, in the middle of 1948. The piloted machines became known as the Pika, an Aboriginal word meaning ‘flier’, and two were built. A mock-up of the aircraft was built and was placed on show at the Department of Supply stand at the Exhibition Building in Melbourne, VIC in about 1951.

The manually piloted prototype had side air intakes (to make room for the cockpit) and retractable undercarriage operated from a pneumatic reservoir. The remotely-piloted version, the Jindivik, followed the same basic form except that it had a single skid instead of an undercarriage and a dorsal air intake located where the Pika's cockpit was. 

The Jindivik Mk.1 was powered by an Armstrong Siddeley Adder (ASA.1) turbojet, which had been developed as a disposable engine for the project. Only 14 Mk.1s were ever made. The Mk.2 was powered by a 7.3 kilonewtons (1,640 lbf) Armstrong Siddeley Viper engine. The Viper was also intended for a short lifespan – about 10 hours, but a "long life" version was also produced for conventional aircraft.

The first prototype Pika after completion was assembled and had its engine run in October 1950 before being disassembled and conveyed by Bristol 170 Freighter on the 23rd to the Long Range Weapons Establishment (LRWE) at Woomera, SA where it was re-assembled and commenced taxiing trials.

Known as Project C, trials commenced on 29 October 1950 with GAF test pilot John Miles, and a brief lift-off was planned for 31 October but the aircraft could not get airborne. An attempt was made with flaps and it lifted off at 185 km/h (115 mph) and flew 1,067 m (3,500 ft). A second flight was made but on 15 November, when another flight was made, undercarriage problems caused a wheels-up landing. Damage was not serious and the aircraft was quickly rebuilt.

The prototype initially carried the serial C-1, and later A93-1. The second, C2 and later A93-2, followed some time later. Further flights were made without incident from 5 December 1950.

The Gloster E.28/39, (also referred to as the Gloster Whittle, Gloster Pioneer, or Gloster G.40) was the first British jet-engined aircraft and first flew in 1941. It was the fourth jet to fly, after the German Heinkel He 178 (1939), the Italian Caproni Campini N.1 motorjet (1940), and the German Heinkel He 280 (1941).

The E.28/39 was the product of a specification which had been issued by the Air Ministry for a suitable aircraft to test the novel jet propulsion designs that Frank Whittle had been developing during the 1930s. Gloster and the company's chief designer, George Carter, worked with Whittle to develop an otherwise conventional aircraft fitted with a Power Jets W.1 turbojet engine. Flying for the first time on 15 May 1941, two E.28/39 aircraft were produced for the flight test programme. Following initial satisfactory reports, these aircraft continued to be flown to test increasingly refined engine designs and new aerodynamic features. Despite the loss of the second prototype, due to improper maintenance causing a critical aileron failure, the E.28/39 was considered to be a success.

The E.28/39 contributed valuable initial experience with the new type of propulsion and led to the development of the Gloster Meteor, the first operational jet fighter to enter service with the Allies. The first prototype continued test flying until 1944, after which it was withdrawn from service; in 1946, it was transferred to the Science Museum in London, where it has been on static display ever since; full-scale replicas have been created.

The development of the turbojet-powered E.28/39 was the product of a collaboration between the Gloster Aircraft Company and Sir Frank Whittle's firm, Power Jets Ltd. Whittle formed Power Jets Ltd in March 1936 to develop his ideas of jet propulsion, Whittle himself serving as the company's chief engineer. For several years, attracting financial backers and aviation firms prepared to take on Whittle's radical ideas was difficult; in 1931, Armstrong-Siddeley had evaluated and rejected Whittle's proposal, finding it to be technically sound but at the limits of engineering capability. Securing funding was a persistently worrying issue throughout the early development of the engine. The first Whittle prototype jet engine, the Power Jets WU, began running trials in early 1937; shortly afterwards, both Sir Henry Tizard, chairman of the Aeronautical Research Committee, and the Air Ministry gave the project their support.

The E.28/39 was a low-wing monoplane designed around the new jet engine. It was described as possessing a slightly tubby appearance as a result of a round fuselage. Due to the elimination of any risk that would have been posed by propeller tips striking the ground, the E.28/39 had an unusually short undercarriage for the era. It had a retractable undercarriage which was actuated by a hydraulic accumulator, with a manually-operated hand-pump to serve as a backup. Emergency actuation used compressed air. The flaps were also hydraulically-actuated, using the hand-pump. Unusually, the nose wheel was steerable, using the rudder control, which aided in ground manoeuvring.

For more details of this historic aircraft, click here.

The Goodyear Inflatoplane was an inflatable experimental aircraft made by the Goodyear Aircraft Company, a subsidiary of Goodyear Tire and Rubber Company, well known for the Goodyear blimp. Although it seemed an improbable project, the finished aircraft proved to be capable of meeting its design objectives, although orders were never forthcoming from the military. A total of 12 prototypes were built between 1956 and 1959, and testing continued until 1972, when the project was finally cancelled.

The original concept of an all-fabric inflatable aircraft was based on Taylor McDaniel's inflatable rubber glider experiments in 1931. Designed and built in only 12 weeks, the Goodyear Inflatoplane was built in 1956, with the idea that it could be used by the military as a rescue plane to be dropped in a hardened container behind enemy lines. The 44 cubic ft (1.25 cubic meter) container could also be transported by truck, jeep trailer or aircraft. The inflatable surface of this aircraft was actually a sandwich of two rubber-type materials connected by a mesh of nylon threads, forming an I-beam. When the nylon was exposed to air, it absorbed and repelled water as it stiffened, giving the aircraft its shape and rigidity. Structural integrity was retained in flight with forced air being continually circulated by the aircraft's motor. This continuous pressure supply enabled the aircraft to have a degree of puncture resilience, the testing of airmat showing that it could be punctured by up to six .30 calibre bullets and retain pressure.

There were at least two versions: The GA-468 was a single-seater. It took about five minutes to inflate to about 25 psi (170 kPa); at full size, it was 19 ft 7 in (5.97 m) long, with a 22 ft (6.7 m) wingspan. A pilot would then hand-start the two-stroke cycle, 40 horsepower (30 kW) Nelson engine, and takeoff with a maximum load of 240 pounds (110 kg). On 20 US gallons (76 L) of fuel, the aircraft could fly 390 miles (630 km), with an endurance of 6.5 hours. Maximum speed was 72 miles per hour (116 km/h), with a cruise speed of 60 mph. Later, a 42 horsepower (31 kW) engine was used in the aircraft.

Takeoff from turf was in 250 feet with 575 feet needed to clear a 50-foot obstacle. It landed in 350 feet. Rate of climb was 550 feet per minute. Its service ceiling was estimated at 10,000 ft.

The GA-466 was the two-seater version, 2 in (51 mm) shorter, but with a 6 ft (1.8 m) longer wingspan than the GA-468. A more powerful 60 horsepower (45 kW) McCulloch 4318 engine could power the 740 pounds (340 kg) of plane and passenger to 70 miles per hour (110 km/h), although the range of the plane was limited to 275 miles (443 km).

The test program at Goodyear's facilities near Wingfoot Lake, Akron, Ohio showed that the inflation could be accomplished with as little as 8 psi (544 mbar), less than a car tire. The flight test program had a fatal crash when Army aviator Lt. "Pug" Wallace was killed. The aircraft was in a descending turn when one of the control cables under the wing came off the pulley and was wedged in the pulley bracket, locking the stick. The turn tightened until one of the wings folded up over the propeller and was chopped up. With the wings flapping because of loss of air, one of the aluminum wing tip skids hit the pilot in the head, as was clear from marks on his helmet. Wallace was pitched out, over the nose of the aircraft and fell into the shallow lake. His parachute never opened. Only 12 Goodyear Inflatoplanes were built, but development continued until the project was cancelled in 1973.

Variants

GA-33 Inflatoplane
The initial single-seat version, with open cockpit, based on the Taylor McDaniel inflatable rubber glider experiments from the early 1930s. One built.
GA-447 Inflatoplane
An enclosed cockpit and new wing, used for undercarriage experiments (tricycle, uniwheel, and hydroskid). One built.
GA-466 Inflatoplane
Company designation for the AO-2 Inflatoplane
GA-468 Inflatoplane
Company designation for the AO-3 Inflatoplane
XAO-2-GI Inflatoplane
Military designation for the GA-466. One built.
XAO-3-GI Inflatoplane
Military designation for the GA-468. Five built.

The X-29 was developed by Grumman, and the two built were flown by NASA and the United States Air Force. The aerodynamic instability of the X-29's airframe required the use of computerized fly-by-wire control. Composite materials were used to control the aeroelastic divergent twisting experienced by forward-swept wings, and to reduce weight. The aircraft first flew in 1984, and two X-29s were flight tested through 1991. While only two were built, the concept is not entirely unique, considering the resemblance to the Sukhoi Su-47.

Two X-29As were built by Grumman after the proposal had been chosen over a competing one involving a General Dynamics F-16 Fighting Falcon. The X-29 design made use of the forward fuselage and nose landing gear from two existing F-5A Freedom Fighter airframes (63-8372 became 82-0003 and 65-10573 became 82-0049). The control surface actuators and main landing gear were from the F-16. The technological advancement that made the X-29 a plausible design was the use of carbon-fiber composites. The wings of the X-29, made partially of graphite epoxy, were swept forward at more than 33 degrees; forward-swept wings were first trialed 40 years earlier on the experimental Junkers Ju 287 and OKB-1 EF 131. The Grumman internal designation for the X-29 was "Grumman Model 712" or "G-712".

The X-29 is described as a three surface aircraft, with canards, forward-swept wings, and aft strake control surfaces, using three-surface longitudinal control. The canards and wings result in reduced trim drag and reduced wave drag, while using the strakes for trim in situations where the center of gravity is off provides less trim drag than relying on the canard to compensate.

For more details of the X-29, click here.

The Handley Page HP.115 was a experimental delta wing aircraft designed and produced by the British aircraft manufacturer Handley Page. It was built to test the low-speed handling characteristics to be expected from the slender delta configuration anticipated for a future supersonic airliner.

The HP.115 was designed during the 1950s as a part of the wider supersonic aircraft research programme that was sponsored by the Ministry of Supply. At the time, both the delta wing and supersonic flight were both relatively recent innovations. By 1956, the Supersonic Transport Committee had been deemed necessary to build a demonstrator to prove that the slender delta wing design was not only suitable for high speed flight but would also be reasonably functional at lower speeds as well. Initially, work centred around an unpowered glider, but it was determined that a self-powered aircraft would be more economic. Accordingly, Handley Page was selected to produce its proposal, the jet-powered HP.115, at the company's Cricklewood facility.

On 17 August 1961, the sole HP.115 performed its maiden flight; flight testing of the wing commenced shortly thereafter. A separate research aircraft, the BAC 221, was also built to study the high-speed aspects of the wing research. Over a relatively lengthy period of experimental flying, the HP.115 proved itself to be relatively capable and provided significant data regarding delta wing characteristics during the takeoff and landing phases. The aircraft itself was withdrawn from the test programme in 1974 and subsequently preserved; it is presently on static display at the Fleet Air Arm Museum. The HP.115 had helped validate the properties of the slender delta wing, leading to a similar wing being adopted for Concorde, the Anglo-French supersonic airliner that entered service during the 1970s.

For details of the design and development, testing and evaluation, click here.

The Heinkel He-111Z was a five engine, twin fuselage aircraft of the Luftwaffe, used to tow large cargo gliders.

With the introduction of the Me-321 Gigant heavy cargo glider in 1940, the Luftwaffe had a need for suitable towing aircraft. To solve the need, two existing bombers were joined by sharing their main wing and adding a center section.

In 1941 the first two prototype Heinkel He-111Z (Zwilling – Twin) aircraft were produced, with a fifth engine added to the center section of the wing.

The glider tug was very successful, well liked by its crews, and enjoyed a trouble free career.

A total of 12 Heinkel He-111Z glider tugs were produced, with eight either shot down or destroyed from bombings. The fate of the remaining four is unclear.

The Hughes XF-11 was a prototype military reconnaissance aircraft designed and flown by Howard Hughes and built by Hughes Aircraft for the United States Army Air Forces. Although 100 F-11s were ordered in 1943, only two prototypes and a mockup were completed. During the first XF-11 flight in 1946, piloted by Hughes himself, the aircraft crashed in Beverly Hills, California. The production aircraft had been canceled in May 1945, but the second prototype was completed and successfully flown in 1947. The program was extremely controversial from the beginning, leading the U.S. Senate to investigate the F-11 and the Hughes H-4 Hercules flying boat in 1947–1948.

While Hughes had designed its predecessors to be fighter variants, the F-11 was intended to meet the same operational objective as the Republic XF-12 Rainbow. Specifications called for a fast, long-range, high-altitude photographic reconnaissance aircraft. A highly modified version of the earlier private-venture Hughes D-2 project, in configuration the aircraft resembled the World War II Lockheed P-38 Lightning, but was much larger and heavier.[2] It was a tricycle-gear, twin-engine, twin-boom all-metal monoplane with a pressurized central crew nacelle, with a much larger span and much higher aspect ratio than the P-38's wing.

The XF-11 used Pratt & Whitney R-4360-31 28-cylinder radial engines. Each engine drove a pair of contra-rotating four-bladed, controllable-pitch propellers, which can increase performance and stability, at the cost of increased mechanical complexity. Due to constant problems with the contra-rotating propulsion system, the second prototype had regular single four-bladed propellers.

On the urgent recommendation of Colonel Elliott Roosevelt, who led a team surveying several reconnaissance aircraft proposals in September 1943, General Henry "Hap" Arnold, chief of the U.S. Army Air Forces, ordered 100 F-11s for delivery beginning in 1944. In this, Arnold overrode the strenuous objections of the USAAF Materiel Command, which held that Hughes did not have the industrial capacity or proven track record to deliver on his promises. (Materiel Command did succeed in mandating that the F-11 be made of aluminum, unlike its wooden D-2 predecessor.) Arnold made the decision "much against my better judgment and the advice of my staff" after consultations with the White House. The order for 100 F-11s was reduced at the end of the war to just three. Hughes delivered only one, a static test model, the other two were either destroyed in a hangar fire or in his crash.

Numerous difficulties of both a technical and managerial nature accompanied the program from the beginning. From 1946-1948, the Senate subcommittee to investigate the Defense Program, popularly known as the Truman Committee and then the Brewster Committee, investigated the F-11 and H-4 programs, leading to the famous Hughes-Roosevelt hearings in August 1947. The program cost the federal government $22 million.

The Hybrid Air Vehicles Airlander 10, originally developed as the HAV 304, is a hybrid airship designed and built by British manufacturer Hybrid Air Vehicles (HAV).

Comprising a helium airship with auxiliary wing and tail surfaces, it flies using both aerostatic and aerodynamic lift and is powered by four diesel engine-driven ducted propellers.

The HAV 304 was originally built for the United States Army's Long Endurance Multi-intelligence Vehicle (LEMV) programme. Its maiden flight took place in 2012 at Lakehurst, New Jersey, in the US. In 2013, the LEMV project was cancelled by the US Army.

HAV reacquired the airship and brought it back to Cardington Airfield in England. It was reassembled and modified for civilian use, and in this form was redesignated the Airlander 10. The modified aircraft completed design certification testing before being written off [1] when it came loose from its moorings in a high wind on 18 November 2017 at Cardington Airfield.

A production run of the Airlander 10 is now planned for 2025.

The images below show why the aircraft has earned the nickname the "Flying Bum".

For more details of this most unique aircraft,click here.

The Junkers F 13 was the world's first all-metal transport aircraft, developed in Germany at the end of World War I. It was an advanced cantilever-wing monoplane, with enclosed accommodation for four passengers. 322 planes of the type were manufactured, an exceptionally large number for a commercial airliner of the era, and were operated all over the globe. It was in production for thirteen years and in commercial service for more than thirty.

The F 13 was a very advanced aircraft when built, an aerodynamically clean all-metal low-wing cantilever (without external bracing) monoplane. Even later in the 1920s, it and other Junkers types were unusual as unbraced monoplanes in a biplane age, with only Fokker's designs of comparable modernity. It was the world's first all-metal passenger aircraft and Junkers' first commercial aircraft.

The designation letter F stood for Flugzeug, aircraft; it was the first Junkers aeroplane to use this system. Earlier Junkers notation labelled it J 13. Russian-built aircraft used the designation Ju 13.

Like all Junkers duralumin-structured designs, from the 1918 J 7 to the 1932 Ju 46, (some 35 models), it used an aluminium alloy (duralumin) structure entirely covered with Junkers' characteristic corrugated and stressed duralumin skin. Internally, the wing was built up on nine circular cross-section duralumin spars with transverse bracing. All control surfaces were horn balanced.

Behind the single engine was a semi-enclosed cockpit for the crew, roofed but without side glazing. There was an enclosed and heated cabin for four passengers with windows and doors in the fuselage sides. Passenger seats were fitted with seat belts, unusual for the time. The F 13 used a fixed conventional split landing gear with a rear skid, though some variants landed on floats or on skis.

The F 13 first flew on 25 June 1919, powered by a 127 kW (170 hp) Mercedes D IIIa inline upright water-cooled engine. The first production machines had a wing of greater span and area and had the more powerful 140 kW (185 hp) BMW IIIa upright inline water-cooled motor.

Many variants were built using Mercedes, BMW, Junkers, and Armstrong Siddeley Puma liquid-cooled inline engines, and Gnome-Rhône Jupiter and Pratt & Whitney Hornet air-cooled radial engines. The variants were mostly distinguished by a two letter code, the first letter signifying the airframe and the second the engine. Junkers L5-engined variants all had the second letter -e, so type -fe was the long fuselage -f airframe with a L5 engine.

For operational history, 'Back in Production 2009-2019' and list of variants, click here.

The Junkers G.38 was a large German four-engined transport aircraft which first flew in 1929. Two examples were constructed in Germany. Both aircraft flew as a commercial transport within Europe in the years leading up to World War II.

During the 1930s, the design was licensed to Mitsubishi, which constructed and flew a total of six aircraft, in a military bomber/transport configuration, designated Ki-20.

The G.38 carried a crew of seven. Onboard mechanics were able to service the engines in flight due to the G.38's blended wing design, which provided access to all four power plants.

During the 1920s, Hugo Junkers made several attempts to produce a large scale commercial transport. His initial attempt, the four-engined JG1, was developed during 1921-1922; but Junkers was forced to destroy the incomplete airplane based on post-WWI Allied demands citing the Treaty of Versailles. Later in the decade, in 1925, he published design specifications for a proposed eighty passenger trans-Atlantic aircraft - the J.1000 project. Then again, towards the end of the decade, the G.40 project was started by the Junkers design team as a trans-Atlantic mail plane. From the G.40 design, which was a seaplane configuration, Junkers also developed a landplane design, designated the G.38. Despite interest from the German armed forces in the G.40 variant, Junkers pushed forward with the landplane design which, having received financing from the Reich Air Ministry (Reichsluftfahrtministerium), was taken forward to the construction stage.

The first Junkers prototype—3301 and marked as D-2000—first flew on 6 November 1929 with four diesel engines: two Junkers L55 V-12 engines and two 294 kW L8 inline-6 engines, with a total power rating of 1470 kW (1971 hp). The Reich Air Ministry purchased the D-2000 for demonstration flights, and took delivery on 27 March 1930. In flight tests, the G.38 set four world records including speed, distance and duration for airplanes lifting a 5000 kg payload. On 2 May 1930 Luft Hansa put the D-2000 into commercial service for both scheduled and chartered flights.

Structurally the G.38 conformed to standard Junkers' practice, with a multi-tubular spar cantilever wing covered (like the rest of the aircraft) in stressed, corrugated duraluminium. The biplane tail, found in other large aircraft of the time, was intended to reduce rudder forces; initially there were three rudders with only a central fixed fin. The undercarriage was fixed, with double tandem main wheels that were initially enclosed in very large spats. The wing had the usual Junkers "double wing" form, the name referring to the full span movable flaps which served also as ailerons in the outer part.

On 2 February 1931 the Leipzig-based Junkers' yard re-engined the D-2000 with two Junkers L8 and two L88 engines, giving a total power rating of 1764 kW (2366 hp) and increasing passenger capacity from 13 to 19.

During its early life the G.38 was the largest landplane in the world. Passenger accommodation was sumptuous by today's standards and was meant to rival that found on the competing Zeppelin service offered by DELAG. The plane was unique in that passengers were seated in the wings, which were 1.7 m (5 ft 7 in) thick at the root. There were also two seats in the extreme nose. The leading edge of each wing was fitted with sloping windscreens giving these passengers the forward-facing view usually available only to pilots. There were three 11-seat cabins, plus smoking cabins and washrooms.

In design terms the G-38 followed the Blended Wing Body design pioneered by Louis de Monge, later followed by Vincent Burnelli in his UB14 and later CBY-3 designs, and even later considered by both NASA and Boeing as an alternative to traditional tube and wing aircraft configurations.

For operational history, click here.

The Kalinin K-7 (Russian: Калинин К-7) was a heavy experimental aircraft designed and tested in the Soviet Union in the early 1930s. It was of unusual configuration, with twin booms and large underwing pods housing fixed landing gear and machine gun turrets. In the passenger version, seats were arranged inside the 2.3-meter thick (7 ft 7 in) wings. The airframe was welded from KhMA chrome-molybdenum steel. The original design called for six engines in the wing leading edge, but when the projected loaded weight was exceeded, two more engines were added to the trailing edges of the wing, one right and one left of the central passenger pod. Nemecek states in his book that at first only one further pusher engine was added.

The K-7 was designed by World War I aviator and Soviet aircraft designer Konstantin Kalinin at the aviation design bureau he headed in Kharkiv, Ukraine, It was one of the biggest aircraft built before the jet age. It had an unusual arrangement of six tractor engines on the wing leading edge and a single engine in pusher configuration at the rear.

In civil transport configuration, it had a capacity for 120 passengers and 7,000 kg (15,000 lb) of mail. As a troop transport it had capacity for 112 fully equipped paratroopers. In bomber configuration it would be armed with 8 x 20mm autocannons, 8 x 7.62mm machine guns and up to 9,600 kg (21,200 lb) of bombs.

The K-7 was built in two years in Kharkiv, starting in 1931.

The K-7 first flew on 11 August 1933. The very brief first flight showed instability and serious vibration caused by the airframe resonating at the engine frequency. The solution to this was thought to be to shorten and strengthen the tail booms, little being known then about the natural frequencies of structures and their response to vibration. The aircraft completed seven test flights before a crash due to structural failure of one of the tail booms on 21 November 1933.

The existence of the aircraft had only recently been announced by Pravda, which declared it was "victory of the utmost political importance," since it had been built with Soviet, rather than imported, steel.

The accident killed 14 people aboard and one on the ground. Flight speculated that sabotage was suspected as the investigating committee had representation by the state security organization, the Joint State Political Directorate (OGPU).

However, there appeared recently some speculation in the Russian aviation press about the role of politics and the competing design office of Andrei Tupolev, suggesting possible sabotage. Although two more prototypes were ordered in 1933, the project was cancelled in 1935 before they could be completed.

Images of this aircraft are scarse or of very poor quality. Some of these images have been taken from flight simulators and are been modified ( eg. extra engines on bottom image). Concept only.

The Lasco Lascondor (also frequently known by the misspelling "Lasconder") was a 1930s Australian 8-seat passenger and mail carrier aircraft built by the Larkin Aircraft Supply Company (Lasco) at Coode Island, Victoria. It is claimed to be the first multi-engined aircraft designed and built in the Southern Hemisphere.

Development of the Lascondor began in June 1928, concurrently with the company's Lascoter; the two aircraft had 90% commonality of structural parts. Like the Lascoter the Lascondor was a high-wing monoplane with a tubular steel structure, featuring a tailwheel undercarriage and a fully enclosed cabin for the passengers and the pilot. A major change was the Lascondor's three Armstrong Siddeley Mongoose engines instead of the Lascoter's single more powerful Siddeley Puma engine. The Lascondor also had greater fuel capacity and a slightly longer fuselage with a redesigned cabin to accommodate an extra row of seats. In addition, while the Lascoter had two sets of flying controls in the cockpit the Lascondor had only one to allow for another passenger seat, giving an overall capacity of seven passengers and one pilot.

The only available photo of the Lascondor.

The Ling-Temco-Vought (LTV) XC-142 was a tri-service tiltwing experimental aircraft designed to investigate the operational suitability of vertical/short takeoff and landing (V/STOL) transports. An XC-142A first flew conventionally on 29 September 1964, and on 11 January 1965, it completed its first transitional flight by taking off vertically, changing to forward flight and finally landing vertically. Its service sponsors pulled out of the program one by one, and it eventually ended due to a lack of interest after demonstrating its capabilities successfully.

In 1959 the United States Army, Navy and Air Force began work on the development of a prototype V/STOL aircraft that could augment helicopters in transport-type missions. Specifically they were interested in designs with longer range and higher speeds than existing helicopters, in order to support operations over longer distances, or in the case of the United States Marine Corps, from further offshore. On 27 January 1961, a series of DOD actions resulted in an agreement where all of the military services would work on the Tri-Service Assault Transport Program under the Navy's Bureau of Naval Weapons (BuWeps) leadership.

The original outline had been drawn up as a replacement for the Sikorsky HR2S, with a payload on the order of 10,000 lb (4,500 kg). BuWeps released a revised specification that specified the same payload, but extended the operational radius to 250 miles (400 km) and increased the cruising airspeed to 250–300 knots (460–560 km/h) and the maximum airspeed to 300–400 knots (560–740 km/h). However, for the Marine Corps mission, the requirement stated that the fuel load could be reduced so that the maximum gross weight would not exceed 35,000 pounds (16,000 kg), as long as a 100-nautical-mile (190 km) radius was maintained.

Vought responded with a proposal combining engineering from their own design arm, as well as Ryan and Hiller, who had more extensive helicopter experience. Their proposal won the design contest, and a contract for five prototypes was signed in early 1962 with first flight specified for July 1964. The design was initially known as the Vought-Ryan-Hiller XC-142, but when Vought became part of the LTV conglomerate this naming was dropped.

The basic design was fairly typical for a cargo aircraft, consisting of a large boxy fuselage with a tilted rear area featuring a loading ramp. It had a wingspan of 67 ft (20 m) and was 58 ft (18 m) long overall. The fuselage housed a 30 ft (9.1 m) long, 7.5 ft (2.3 m) wide 7 ft (2.1 m) high cargo area with a somewhat boxy cockpit on the front for the crew of two pilots and a loadmaster. The wing was high-mounted and the tail surfaces were a "semi-T-tail" to keep the rear area clear during loading. Tricycle landing gear were used, with the main legs retracting into blisters on the fuselage sides. In normal parked configuration it would appear to be a conventional cargo plane.

For V/STOL operations, the aircraft "converted" by tilting its wing to the vertical. Roll control during hover was provided by differential clutching of the propellers, while yaw used the ailerons, which were in the airflow. For pitch control the aircraft featured a separate tail rotor, oriented horizontally to lift the tail, as opposed to the more conventional anti-torque rotors on helicopters that are mounted vertically. When on the ground, the tail rotor folded against the tail to avoid being damaged during loading. The wing could be rotated to 100 degrees, past vertical, in order to hover in a tailwind.

For more details of development, design, and operational history, click here.

The Lockheed U-2, nicknamed "Dragon Lady", is an American single-jet engine, high altitude reconnaissance aircraft operated by the United States Air Force (USAF) and previously flown by the Central Intelligence Agency (CIA). It provides day and night, high-altitude (70,000 feet, 21,300 meters), all-weather intelligence gathering.

Lockheed Corporation originally proposed it in 1953, it was approved in 1954, and its first test flight was in 1955. It was flown during the Cold War over the Soviet Union, China, Vietnam, and Cuba. In 1960, Gary Powers was shot down in a CIA U-2C over the Soviet Union by a surface-to-air missile (SAM). Major Rudolf Anderson Jr. was shot down in a U-2 during the Cuban Missile Crisis in 1962.

U-2s have taken part in post-Cold War conflicts in Afghanistan and Iraq, and supported several multinational NATO operations. The U-2 has also been used for electronic sensor research, satellite calibration, scientific research, and communications purposes. The U-2 is one of a handful of aircraft types to have served the USAF for over 50 years, along with the Boeing B-52, Boeing KC-135, and Lockheed C-130. The newest models (TR-1, U-2R, U-2S) entered service in the 1980s, and the latest model, the U-2S, had a technical upgrade in 2012.

For details of the background, design and development, operational history, and long list of variants, click here.

The Lockheed XFV (sometimes referred to as the "Salmon") was an American experimental tailsitter prototype aircraft built by Lockheed in the early 1950s to demonstrate the operation of a vertical takeoff and landing (VTOL) fighter for protecting convoys.

The Lockheed XFV originated as a result of a proposal issued by the U.S. Navy in 1948 for an aircraft capable of vertical takeoff and landing (VTOL) aboard platforms mounted on the afterdecks of conventional ships. Both Convair and Lockheed competed for the contract but in 1950, the requirement was revised, with a call for a research aircraft capable of eventually evolving into a VTOL ship-based convoy escort fighter. On 19 April 1951, two prototypes were ordered from Lockheed under the designation XFO-1 (company designation was Model 081-40-01). Soon after the contract was awarded, the project designation changed to XFV-1 when the Navy's code for Lockheed was changed from O to V.

The XFV was powered by a 5,332 hp (3,976 kW) Allison YT40-A-6 turboprop engine driving three-bladed contra-rotating propellers. The tail surfaces were a reflected cruciform v-tail (forming an x) that extended above and below the fuselage. The aircraft had an ungainly appearance on the ground with a makeshift, fixed landing gear attached. Lockheed employees derisively nicknamed the aircraft the "pogo stick" (a direct reference to the rival Convair XFY's name).

The Lockheed YO-3 Quiet Star is an American single-engined, propeller-driven aircraft that was developed for battlefield observation during the Vietnam War. Designed to be as quiet as possible, it was intended to observe troop movements in near-silence during the hours of darkness.

The YO-3A was designed to a United States Army specification of 1968, which called for an observation aircraft that would be acoustically undetectable from the ground when flying at an altitude of 1,500 feet (457 m) at night.

Lockheed Missiles and Space Company located in Sunnyvale, California was contracted to produce two prototype aircraft. In 1966, the company built two QT-2 "Quiet Thrusters", using modified Schweizer SGS 2-32 gliders. The prototype QT-2s were then modified to the QT-2PC "PRIZE CREW" configuration. The QT-2PC had a silenced engine and a slow-turning propeller for quiet operation.

Following operational trials with the QT-2PC in Vietnam, a production aircraft, designated the YO-3A was ordered. This aircraft's design was also based on the Schweizer SGS 2-32 glider. Like the QT-2PC, the YO-3A has a large wingspan and a larger canopy area for observation. Two crew members (a pilot and an observer) are seated in tandem. The observer is located at the front of the cockpit. The YO-3A is an all-metal low-wing monoplane of semi-monocoque construction. The control surfaces of the YO-3A including the ailerons and rudder are fabric-covered. The engine cover, canopy, engine exhaust shroud, wing-root fairings, and wheel-well fairings were constructed of fiberglass. The YO-3A has retractable tailwheel-type landing gear.

The YO-3A was powered by an air-cooled, six-cylinder, horizontally opposed, fuel-injected, Continental Model No. IO-360D engine. The engine is coupled to a slow-turning propeller through a belt pulley-drive system. The propeller reduction ratio is 3.33:1. Originally equipped with a six-bladed ground-adjustable-pitch propeller, this was replaced in March 1971 with a three-bladed laminated constant-speed wooden propeller designed by Ole Fahlin. The engine cowling and firewall were lined with fiberglass material to dampen and contain engine noise.

The YO-3A is equipped with an Asymmetrical Exhaust System. A crossover exhaust pipe is used to remove exhaust from the left bank of engine cylinders to the right side of the engine compartment. This crossover joins the right bank exhaust pipe and exits along the lower right side of the engine compartment. The exhaust gases are then moved through an acoustical fairing into a dissipating and resonating muffler continuing to the aft end of the fuselage.

Nine of the eleven YO-3As produced operated in South Vietnam, at night, from 1970 to 1971 (Late June 1970 to September 1971) and, although three were destroyed in crashes, were never damaged by enemy fire or shot down. The YO-3A was very successful in spotting movement by the Viet Cong and North Vietnam Army (NVA) operating in South Vietnam.

For more details of operational history during the Vietnam war, and postwar usage, click here.

Variants

QT-1 Quiet Thruster
Proposed single-seat powered glider based on the Schweizer SGS 2-32, not built.
QT-2
Two modified Schweizer X-26 two-seat sailplanes for evaluation, later modified with sensor packages as the QT-2PC.
QT-2PC PRIZE CREW
Two QT-2s with combat sensor packages for evaluation in Vietnam theatre, one reduced to spares and the other returned to the United States Navy as the Schweizer X-26B.
Q-Star
Modified Schweizer SGS 2-32 for engine/propeller development.
YO-3A
Production aircraft for the United States Army, 11 built

The Lun-class ekranoplan (also called Project 903) is a ground effect vehicle (GEV) designed by Rostislav Alexeyev in 1975 and used by the Soviet and Russian navies from 1987 until sometime in the late 1990s.

It flew using lift generated by the ground effect acting on its large wings when within about four metres (13 ft) above the surface of the water. Although they might look similar to traditional aircraft, ekranoplans like the Lun are not classified as aircraft, seaplanes, hovercraft, or hydrofoils. Rather, crafts like the Lun-class ekranoplan are classified as maritime ships by the International Maritime Organization due to their use of the ground effect, in which the craft glides just above the surface of the water.

The ground effect occurs when flying at an altitude of only a few meters above the ocean or ground; drag is greatly reduced by the proximity of the ground preventing the formation of wingtip vortices, thus increasing the efficiency of the wing. This effect does not occur at high altitude.

The Utka, can engage enemy ships out to its radar horizon (about 35 kilometers/22 miles) but can fire the SS-N-22 out to the missile's 100-kilometer (62-mile) range with over-the-horizon targeting data.

The name Lun comes from the Russian word for the harrier. Two were planned, one was built, the other cancelled.

However, after its retirement in the late 90s, the heavily-armed ship - which is bigger than a jumbo jet - was left sitting at the unused Kaspiysk naval base. The Russian MD-160, aka 'Ekranoplan', aka 'Utka'  - nicknamed the 'Caspian sea monster' - has been transported to Derbent, Dagestan, to become a tourist attraction.