THE DIFFICULT TASK OF SUPPLANTING SMALL AIRPLANES AND HELICOPTERS: THE XXIst CENTURY IS ALREADY HERE. WHERE ARE THE FLYING CARS?
Throughout the last century, the most common vision of the future invariably included flying cars. The future used to be now 1980, now 2000. Well, the 21st century arrived but there are no flying cars anywhere. What happened? What has been done so far?
In all honesty, in the U.S. there is indeed a company that is already offering for sale a flying machine compact enough to takeoff from any street. Its flight technology is based on the so-called ducted fans, popular in many remote-control model airplanes: small propellers rotating at high speed in a short drum, so as to create an air current within the cylinder, which with the aid of inertia becomes a stable jet ejected powerfully from the aft part.
The machine, called Moller M400X Skycar, has four of these drums, one at each corner of the vehicle, that can turn down to takeoff and then back to level cruise flight. Each drum has two Wankel rotary-type combustion engines, alcohol-fueled, with 150 hp each, giving a total of 1200 hp to move the vehicle. The delicate transition from vertical to horizontal flight would be controlled by computers, as well as stability and coordination of the commands to go up, go down, speed-up or slow-down, so that the vehicle can be operated without having experience in piloting airplanes.
It has basically two problems: one is that every vehicle that rises more than three meters above the ground is classified by the authorities as an aircraft and not an automobile, so it must pass all safety, handling, stability, and reliability test required to planes and helicopters. Since 2002 a prototype Skycar has managed to rise a few meters but so far has not gone through any of these tests, despite the promises. The other problem is its price: US$ 995,000.
Several people have been put down deposits of US$ 100,000 to the company since 2003, and as yet they still do not have their flying cars in their garages court actions started.
As any new technology must compete on price and quality with what already exists, it is good to do a brief review of what already flies smoothly.
We do not consider small airplanes as flying cars because they need an airport, but as they usually content themselves with a few blocks of dirt road, they already have their uses. The best-selling airplane in History is the Cessna 172. Since its launch in 1956 until today over 43 000 units have been produced, in different versions. With its high wing and fixed landing gear this single-engine has become the stereotype of small plane. The current version is the 172 Skyhawk SP. With its 4-cylinder engine and 180 hp it surpasses the mark of 230 km/h and can travel 1180 km. Loaded with all the optional equipment it is sold for US$ 437,869 in the U.S. market.
The best-selling airplane during the year 2012 was the Cirrus SR22. It is a low-wing, fixed landing gear single-engine with a modern and spacious interior inspired by luxury cars. Unlike the Cessna, it is not made of aluminum but of plastic reinforced with fiber-glass, improving aerodynamics and weight. Another novelty is that it includes a large parachute of pyrotechnic deployment that serves as ejector seat: the occupants do not leave the airplane but the complete airplane is lowered down by the parachute. The version of the SR22 with the 6-cylinder engine with turbochargers gets close to 400 km/h, with a maximum range of about 2200 km, for a base price of US$ 619,900.
The fastest piston single-engine airplane today is the Acclaim Type S model of the U.S. company Mooney. Of conventional aluminum construction but careful aerodynamics, with retractable landing gear, it has a 6-cylinder engine supercharged by turbo-compressors that is quite powerful (280 hp) relative to the small size of this airplane, certainly somehow tight for 4 people. This combination achieves a top speed of almost 450 km/h. It costs about US$ 719,000 in the U.S. market.
The Skycar is more complex than these planes, so it would hardly cost less.
AIR TRAVEL IN CLOUDY DAYS
One problem with all these small planes is that they can not fly very high and therefore are unable to escape from bad weather clouds, which are often concentrated in the lower altitudes. This is both inconvenient and dangerous. Even if they could manage to get up high enough (for example, in the versions with engines blown by turbo-compressors), their cabins are generally not pressurized, so the occupants must wear oxygen masks continuously. Even so, the low atmospheric pressure usually causes other bodily ailments, such as abdominal pains. On the other hand, every time these airplanes have to cross through wet clouds to go up or down they are exposed to ice formation that might stick on sensitive parts of the machinery. In summary, traveling in these small airplanes is only advisable if the weather is good, so one must be very flexible with the schedules.
To avoid having to stay at home if it rains, all-weather small airplanes have been developed for decades, but obviously these are much more expensive.
For example, a M350 from Piper has pressurization in its 6-passenger cabin and (when well equipped) anti-ice devices on the wings, stabilizers, propeller and engine, and even has an onboard weather radar. Its turbocharged, 350-hp 6-cylinder engine takes it to 7600 m (25 000 ft) altitude. But it costs US$ 1,296,274.
The ultimate propeller-driven personal transport is probably the Beechcraft King Air C90GTx. It has no pistons but reliable turbines spinning the propellers. In fact it has two engines, which gives peace of mind when flying over the sea or over mountainous terrain. Price of this all-weather airplane: US$ 3,595,000.
If you have all those millions you could buy small jets like the Cessna Citation Mustang (US$ 3,350,000), but as these jets can not operate from short and unpaved runways they end up competing not with cars but rather with the airlines.
TAKEOFFS FROM TENNIS COURTS
But back to what we all seek: vertical takeoff. The cheapest helicopter in the market is the Robinson R22 Beta II. For just two people, it is raised by a small piston engine with 4 cylinders and 130 hp, which turns a two-bladed rotor of just 7,7 meters in diameter (the same width as the Harrier vertical-takeoff fighter). His bigger brother, the four-seater R44 Raven II, is the best-selling helicopter today. It can reach a price of US$ 495,420 in the U.S. market.
If you want the extra safety provided by a turbine engine a popular choice is the Eurocopter EC 120B Colibri, at a price of about US$ 2 million.
But none of them is ready to fly in bad weather. For that you would have to have something big and with all the bells and whistles as the Agusta Westland AW109 Power, a twin-engine helicopter with retractable wheels and 285 km/h, in the range of $ 6.3 million. The Skycar would be cheaper, but it could not fly in bad weather ... if it gets to fly at all.
A GOOD IDEA AND THE MONEY NEEDED
The only flying car that was able to be approved by the authorities for retail was the Taylor Aerocar. Developed during the 1950s by U.S. engineer Molt Taylor, it was actually a plane that could travel along the ground: its fuselage was specially designed to be driven around town once you separate its wings and tail. These parts, along with the propeller, could be towed on wheels behind what becomes now a car, or left at the airport waiting for the return of its owner from her or his urbanite businesses, to be assembled in minutes and initiate the return flight to the city of origin.
Six prototypes were built, but when Taylor sought financial backers to install the production line it was discovered that its market was very small, with only half of the required 500 clients, so the business never took off. The prototypes ended being acquired by museums and collectors. One is still flying today.
The problem, like so many things in life, seems to be money. With the cost of a plane-car you could buy a good plane and a good car, jointly.
Achieving a vertical-takeoff-and-landing machine as compact as a car is difficult. In the 1950s an odd jet flying saucer, called VZ-9-AV Avrocar, was offered to the U.S. Army for the vertical transport of troops. It was only 5,5 meters in diameter, but it was very noisy and gave off an unbearable heat. And that is a problem inherent in any device that moves air or other gases for takeoff. The lift force will depend on the diameter of the column of jet and its velocity, so if we want to reduce the diameter we must increase its velocity, thus increasing the problems of required power and excessive noise and/or heat.
Obviously, the helicopter is not the same as the car run by "anti-gravity" (or something like that) that everyone is expecting. In that case, the future has not yet arrived. Meanwhile, those with deep pockets could daydream by giving a new look to that tennis court in the backyard of the mansion.
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Originally published in ABC Color, on 2 December 2007. Photograph: The Taylor Aerocar III (registration: N100D) on display at "The Museum of Flight", Seattle, USA, 5 March 2005. The port wing is extended while the starboard remains folded. Note the tail assembly and pusher propeller. Photo credit: Jim Collaborator, via Wikimedia Commons.