The Bizzare Design of Quadcopters
For over a hundred years the world of aviation has been one of humanity’s most fertile playgrounds, a melting pot of ideas both weird and wonderful where experimentation is prized and orthodoxy shunned – cue the Quadcopters.
Most of the time peculiar designs fuel innovation, and many of their novel components or systems are often integrated into future aircraft in a process of constant technological refinement.
But sometimes aeronautical engineers can go a little off the deep end, and create craft so outlandish it is hard to find many redeeming features. One such contraption was the Curtiss-Wright VZ-7, just one of many freakish quadcopters that entered into the US Army’s 1956 ‘Flying Jeep’ competition.
Quadcopters have always been explored since the very earliest days of aviation. It was first introduced by the Brèguet brothers in 1907 with their Brèguet-Richet Gyroplane No. 1 consisting of four rotors powered by a belt and pulley system.
The next engineer to take up the quest for quadcopters was fellow Frenchman Étienne Oehmichen in 1920 with his creation, the Oehmichen No. 2, which had four two-bladed rotors that could be warped to provide rudimentary control. Since the Brèguet-Richet Gyroplane was engineered with no control surfaces, the Oehmichen was the first genuinely flyable quadcopter, able to remain airborne for several minutes at a time by 1923.
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In 1922 George de Bothezat and Ivan Jerome dabbled with a similar craft replete with six-bladed rotors and two additional propellors, but it was only ever able to reach 5 meters off the ground.
Plagued by unsolvable weight and technical issues, enthusiasm for the concept died down for many decades as engineers re-shifted their focus to more viable machines.
It would take until 1956 and the construction of the Convertawings Model A, for the idea to gather steam once more after it was discovered that forward flight could actually be achieved with quadcopters.
A lack of customer interest though meant this particular project was swiftly abandoned, but the cause was not lost, for that very same year the US Army held a bizarre competition to finally determine the quadrotor’s true efficacy.
Officials were on the hunt for a light aerial utility vehicle that could hover at low altitudes to overcome difficult terrain, fly forward at moderate speeds, and which could carry a payload for several hours at a cruising altitude of between 1.5 to 3.6 meters.
Piquing the interest of several manufacturers, very soon the Army had several ‘Flying Jeep’ proposals, all of which were helicopter-like quadcopters.
Chrysler’s answer to the unusual call was the VZ-6, a rectangular-shaped craft whose two ducted propellers were powered by a 373 kilowatt Lycoming reciprocating engine located at the centre of the vehicle, right next to the offset pilot’s position.
With propellors placed both forward and aft, a rubber skirting outside the vehicle’s bottom edge helped sustain lift, while forward propulsion was achieved by lowering the nose arch and channelling the propellor’s slipstream to the rear with the assistance of duct-mounted vanes.
In late 1958 two VZ-6 units with the serial numbers 58-5506 and 58-5507 were delivered in preparation for test flights commencing at the start of 1959. During trials however, the VZ-6, which weighed 1,088 kilograms, performed very poorly since it was too heavy and its engine was woefully underpowered, which in turn meant it suffered from serious lateral stability problems.
In fact, on its first non-tethered flight, it was this litany of issues that would ultimately cause it to flip completely over. Although the pilot emerged unscathed the VZ-6 was broken beyond repair. With US evaluators not willing to provide the capital to mend it, the entire program was shelved and both VZ-6 quadcopters were promptly disposed of in 1960.
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In contrast to the disaster-prone Chrysler V-6, the Piasecki VZ-8, the product of an Army Transportation Research Command awarded in 1957, showed remarkably more promise.
The brainchild of Piasecki, an industry leader in vertical lift research and development, the VZ-8 initially started life as the Model 59K Sky Car before changing to Airgeep during trials and then to VZ-8P, with ‘P’ standing for Piasecki.
Equipped with two tandem, three-bladed, ducted rotors, the VZ-8 was propelled by two 134-kilowatt Lycoming piston engines hooked up to a single central gearbox which ensured it would still stay airborne if one of the powerplants failed.
Much of the VZ-8’s control interface resembled that of a helicopter, with directional stability provided by a series of hinged vanes mounted under each rotor duct, while much like a conventional plane, it had fixed tricycle wheeled landing gear.
Lastly, unlike the single-seated VZ-6, the VZ-8 had space for a pilot as well as a passenger, both of whom sat between the rotor ducts.
After its maiden flight in October 1958, the engines of the VZ-8 were also changed, with the Army retrofitting it with a single 317 kilowatt Turboméca Artouste IIB turbine in place of the Lycoming pistons.
Following the first turbine-powered flight in June 1959, the craft was next loaned out to the Navy for a brief period before being returned to the Army and reinstalled with the lighter and more powerful AiResearch TPE331-6 turbine. The Piasecki was certainly a strong contender, but the Curtis-Wright VZ-7 threatened to be even better.
Like the VZ-8, in 1957 the Curtiss-Wright Santa Barbara Division, formerly known as the Aerophysics Development Corporation before it was merged, was also awarded a contract for the development and flight testing of two prototype aircraft. Designated VZ-7, in mid-1958 two Curtiss-Wright flying jeeps emblazoned with the serial numbers 58-5508 and 58-5509 were delivered promptly to the US Army.
The VZ-7 in many ways resembled the design of the VZ-6 but was much superior in almost every aspect. The VZ-7 had a rectangular central airframe, four vertically mounted ducted propellors which were later replaced with unshrouded propellors, and its central fuselage accommodated the pilot’s seat, flight controls, fuel and lubricant tanks, as well as the single 317-kilowatt Turboméca Artouste IIB shaft-turbine engine.
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The control layout was simple and elegant, with directional movement controlled by varying the thrust of each individual propellor and yaw movement determined by movable vanes fixed over the engine exhaust.
During company flight testing and Army assessments, both VZ-7s were impressed with their ability to hover and to perform forward flight with relative stability. On the other hand, the VZ-7 proved consistently incapable of meeting altitude and speed requirements set out by the Army, and by mid-1960 both specimens had been returned to their manufacturer.
Although all of the submissions to the 1956 competition had been either discontinued or destroyed, by 1960 the US Army had not quite given up on the dream of the flying jeep. Collaborating once again with Piasecki, a more advanced version of the VZ-8, one of the more impressive entrants, was conceived and given the moniker Model 59H Airgeep II by the manufacturer and VZ-8P (B) by the Army.
Among the most pertinent differences to the previous edition was the inclusion of an angled duct, a set of 298-kilowatt Artouste IIC engines, zero-altitude zero-speed ejection seats, seating for 3 passengers accommodating a pilot, co-pilot, and gunner, and finally the addition of a powered tricycle landing gear to improve ground handling as well as overland mobility.
During its first non-tethered flight in the summer of 1962, the merits of the VZ-8P began to show. Since it was not dependent upon surface-effect lift for flight, the new model could fly thousands of feet in the air with stability despite it only being required to operate only a few feet off the ground. What’s more, the VZ-8P was fairly agile and could hover above or below trees as well as between buildings and other obstacles.
Moreover, the Airgeep demonstrated it could be a surprisingly good weapons platform that could even trump helicopters. This was because unlike choppers, which had to rise above their targets to get shots off, the Airgeep gunner was able to engage targets with the same range and scope at a much lower position, and thus it would be able to more effectively use cover.
In addition, the Airgeep was found to possess desirable stealth characteristics since its ducts shielded the turning rotors, making them invisible not only to the human eye but also to radar.
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Unfortunately despite possessing a slew of unexpected advantages over the helicopter, the Airgeep was canceled because it was believed that such a contraption would be mechanically ill-suited to the rigors of field operations.
The dropping of both Airgeeps from the inventory of the Army in the mid-1960s would also sound the death knell of quadcopters, a strange if entertaining historical footnote.