In the 50s and 60s, the development of one of the most exotic types of vehicles began - “flying platforms” and related “flying jeeps”. The initial purpose of the "flying platform" was to carry out reconnaissance missions, they were calculated for the flight of one person. The larger "flying jeep" seemed to be potentially useful for many different tasks.
Not so long ago, we discussed the HZ-1 Aircraft, but there were also examples of design ideas …
"Flying platform" began to be called a vertically taking off vehicle with coaxial propellers located in an annular channel. Development of single-seat "flying platforms" for combat use began in the United States as part of the NASA research program in the early 1950s. The tests involved manned tethered platforms, first lifted into the air with compressed air and then with rotors. The concept used in the development was proposed at one time by NASA engineer Ch. Zimmerman, who is already known to the reader for his flying pancakes V-173 and XF5U-1.
His proposal was as follows. If the rotor, for example, was placed at the bottom of the base of the vehicle, then the pilot would be able to control the vehicle by moving his own weight, the so-called. "Kinesthetic" management. This control is based on a person's instinctive response to maintain balance when standing or walking. In the "flying platform", the pilot tilts to the required side to turn the vehicle to the desired position. It was assumed that such control would allow the pilot to fly on such a platform after a little training.
Preliminary tests demonstrated the concept's technical feasibility, after which three companies - Lackner, Bensen and Hiller - were awarded contracts to develop a prototype of the platform.
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In the mid-1950s, Lackner developed an aircraft called the DH-4 "Helivector," later renamed the HZ-1 "Aerocycle," which looked like a hybrid of an outboard-powered helicopter with a motorcycle. This unit was a design with a 40 hp Mercury engine installed on it. and a landing device consisting of air bags at the ends of the side members. The air bags were later replaced by metal struts. The engine controlled a pair of counter-rotating 4.6 m diameter rotors mounted under the engine, while the pilot stood vertically on a platform above the engine, protected from falling into the rotor by safety harnesses.
The Helivector / Aerocycle first flew in January 1955 and was successful, after which the US Army ordered 12 aircraft. According to Lackner representatives that the aircraft could fly at speeds of up to 105 km / h and carry a 55 kg payload in addition to the pilot, the flight lasted for about one hour. However, one thing reminded me that flying was dangerous. Not only did the pilot stand above the rotating rotors, but the rotors were structurally located close to the ground, making landing and takeoff dangerous, as rocks and various debris could easily fall into them.
Some sources claimed the Helivector / Aerocycle was easy to fly, but others stated, citing the opinion of test pilots, that novices could not fly the craft in complete safety. After two flight accidents in which the counter-rotating rotors bent and collided, the project was abandoned before anyone was seriously injured.
Bensen's B-10 Propcopter was no more successful. This unsightly little machine consisted of a square frame with 1.2m diameter propellers mounted vertically in front and behind the frame. Each was powered by its own 72 hp McCulloch engine. The Propcopter flew in 1959 and was obviously difficult to fly.
The project was soon discontinued.
Hiller's projects have been better thought out and have attracted a lot of attention. Hiller developed its first "flying platform" VZ-1 "Pawnee" on the basis of a contract awarded in late 1953 by the Navy Research and Development Administration (ONR). The car took off for the first time in February 1955.
VZ-1 had a pair of counter-rotating rotors with a diameter of 1.5 m, located inside the annular channel. Each rotor was driven by its own 40 hp two-stroke engine. The pilot stood over the ring canal, surrounded by a railing and secured by seat belts. He controlled the engines with the throttle and bent down to steer the craft in one direction or the other. The annular channel improved safety during takeoff and landing. In addition, it also provided an additional 40% increase in lift. The device handled well in flight, but it was soon modified: they installed longer landing gear legs to increase ground clearance, and put eight rudders below the channel to improve flight control.
The US Army was interested in the VZ-1, and in November 1956 Hiller was awarded a contract to build a larger version, which made its maiden flight in 1958. The new unit had three 40hp engines. rotating rotors in an annular channel with a diameter of 2.4 m. This more than doubled the rotor area, increasing the payload weight and flight range while reducing engine noise.
The army has ordered a third larger unit. Instead of a wheeled chassis, as in the two earlier designs, a ski chassis was installed. The aircraft had a seat and a conventional helicopter control as the center of gravity control became less efficient due to the increase in vehicle power and weight. This version first took off in 1959. The VZ-1 had its merits, but it was ultimately judged too small, slow and fit for limited use only. The army abandoned the program in 1963, and two of the three devices survived only in museum displays.
At the same time that research on "flying platforms" was being conducted, under contracts with the US Army, large aircraft such as "flying jeep" were being developed. This was the name of the aircraft of the two-screw longitudinal scheme or four-screw. Initially, "flying jeeps" were conceived as a universal vehicle that was supposed to take place between the army Jeep all-terrain vehicle and a light helicopter. It could be used for transport or reconnaissance operations, as a mobile platform for firing recoilless guns, launching missiles, for adjusting artillery fire, installing electronic equipment, etc. Research began in 1956, then a competition was announced, in which about 20 firms took part. The winners were Chrysler, Curtiss-Wright and Pyasetsky,which were awarded contracts totaling $ 1.7 billion to build prototypes.
Chrysler developed two prototypes of its "flying jeep" VZ-6, supplying them to the army in late 1958. The VZ-6 was a single-seat, rectangular box-shaped vehicle with two rotors at the front and rear. There were rubber conical fairings around the base of the vehicle, rudders were installed below the rotors. The VZ-6 was powered by a single 500 hp piston engine. Tethered flights in 1959 showed that the VZ-6 was not very well controlled and had insufficient power. The first free flight of the VZ-6 led to the overturning of the craft. The pilot survived, but the vehicle was badly damaged. The army recognized the VZ-6 as an unsuccessful development, both prototypes were sent for scrap in 1960.
Developed by Curtiss-Wright, the VZ-7 was also known as the "flying truck." Two prototypes were delivered to the army in mid-1958. The VZ-7 was a simple metal truss with a pilot in the front and four propellers positioned at the corners. All propellers were driven by a single 425 hp Artouste engine. The device was controlled by a differentiated change in the pitch of the screws, as well as by rudders. The VZ-7 was 5.2 m long and 4.9 m wide and had a maximum take-off weight of 770 kg, the unit could carry 250 kg of payload. The VZ-7 handled well and was easy to fly, but it did not meet the altitude and speed requirements. Soon the tests were completed, and the prototypes were returned to the company in mid-1960.
The efforts of the Pyasetskiy firm to create the "flying jeep" were the most successful of the three competing firms. Its first vehicle was the Model 59H AirGeep, which was given the military designation VZ-8P. The VZ-8P was 7.9 m long and 2.7 m wide, with three-bladed rotors in the front and rear, with the pilot and passenger in between. In the VZ-8P, the 2.4m rotors were driven by a pair of 180hp Lycoming piston engines, with one engine being able to drive both rotors if the other failed. The rotors rotated in opposite directions. Control was provided by changing the pitch of the propeller, as well as rudders mounted from below. Forward movement was achieved by lowering the nose of the apparatus down.
The first flight of the VZ-8P took place on October 12, 1958. Based on the results of the test flight, it was decided to supply a more powerful power plant. The device was returned to the company to replace the piston engines with one 425 hp Artouste IIB gas turbine engine, the upgraded VZ-8P flew at the end of June 1959. It weighed 1.1 tons and could carry a load of 550 kilograms, including the pilot.
The VZ-8P also took part in the competition for the development of a "flying jeep" for the Navy, which began in June 1961. An even more powerful Airesearch 331-6 engine was installed on it, in addition to this, the device was equipped with floats. The new version of the device received the designation RA-59 "SeaGeep".
The firm "Pyasetsky" built another device under the new contract under the designation "Model 59K" (military designation VZ-8P (B) "AirGeep II"), which made its first flight in the summer of 1962. The device VZ-8P (B) was similar to its predecessor, except that the structure had a slight break in the middle. It was believed that a slight tilt of the nose and tail rotors would reduce drag in level flight. As a power plant for the VZ-8P (B), two Artouste PS engines with a capacity of 400 hp were used, connected so that if one engine failed, the other could control both rotors. One engine could also be connected to a wheeled chassis to steer the machine while driving on the ground. The increased power of the power plant made it possible to achieve a maximum take-off weight of 2200 kg. The pilot and observer had ejection seats, which allowed the crew to escape at almost zero speed of the vehicle. In addition, the vehicle had room to accommodate additional passengers or cargo.
The experience of operating "flying platforms" and "flying jeeps" in the 50-60s showed that they had some advantages, in particular, they were smaller in size than helicopters and could work on the ground more successfully. However, the helicopters could easily land in mountainous terrain and had more comfortable seating for passenger seats. The biggest drawback was that the "flying platforms" and "flying jeeps" had small rotor areas, because this was the reason for their instability in some modes, and a relatively high fuel consumption. And since they did not show sufficient advantages over helicopters, their further development was suspended.
However, at the end of the 90s, interest in devices of this type reappeared. The American firm "Millennium Jet" (Sunnyvale, Calif.) Has developed an unusual project called the "SoloTrek" XFV. It is a hybrid of a "flying platform" and a tiltrotor. The pilot is standing in the apparatus, above his head there are two screws with a diameter of 0.9 m in the annular channels, the apparatus is controlled by two handles in the armrests. The right stick is for directional control and the left stick is for engine speed control. The pilot, in addition to the usual flight instruments, has a display built into the helmet goggles. When moving horizontally (forward or backward), the screws are synchronously deviated from the vertical axis; when the apparatus is rotated around the vertical axis, the differential deviation of the screws is carried out.
SoloTrek "has a total weight of 318 kg, cruising speed - 95 km / h, top speed - 130 km / h, fuel capacity - 38 liters, range - 240 km. The ceiling is expected to be 2440 m, although in practice the device will fly at low altitudes. The SoloTrek prototype had a 120 hp Hirth F30 engine. This engine is often used in ultralight aircraft. It can rotate propellers at speeds up to 5,000 rpm, although the craft is expected to take off at 3,500 rpm. The propellers are made of nylon / CFRP composite material and can withstand bird impact. In serial production, the SoloTrek will probably be equipped with a 125 hp WTS-125 engine. The set of the SoloTrek apparatus includes a parachute, which opens automatically upon a signal from the accelerometer if the apparatus begins to fall. At the end of October 2000, the experimental apparatus was tested at the center. Ames (California). Its designer Michael Moshier, a former US Navy pilot, believes that "the time has come for aircraft like the SoloTrek."
The Israeli company Aero-Design & Development (AD&D) has been working on a "flying platform" called the Hummingbird, which bears a resemblance to the Hiller apparatus. The Hummingbird is built using modern technologies, for example, to reduce weight in the design and
enjoy composite materials. The power plant of the apparatus consists of four piston engines. The device weighs about 115 kg, the maximum flight duration is 45 minutes at a speed of 45 km / h.
The Millennium Jet is developing another device called the DuoTrek, which is a hybrid of a helicopter and a tiltrotor. "DuoTrek" is 4.8 m long, fully loaded weighs 660 kg, can carry 160 kg of payload at a distance of 550 km. Variants of the vehicle with two and four propellers are being developed, designed for a crew of one and two people. This development became interested in the Advanced Research Department of the US Department of Defense.
Another American company, PAM (Virginia), has been working on the "flying platform" since 1989 and built the ILV (Individual Lifting Vehicle). ILV resembles an interesting blend of various early flying platform designs. It is a simple tubular structure with a diameter of approximately 3 m on legs, powered by two 195 hp "Hirth" F-30 engines, each of which rotates a 2.8 m diameter propeller. Control is provided by a pilot who stands on top of the platform and uses a control method by moving the center of gravity. The PAM 100V device has an empty weight of approximately 300 kg, can carry a payload weighing up to 200 kg, the maximum speed is 100 km / h, and the range is 40 km. The company intends to use the device, in particular,for the protection of cattle herds or for the pollination of crops.