Date:27 January 2011
The flying car – it’s been a tantalising but elusive dream since the early days of aviation. Now a new wave of entrepreneurs, Nasa and the Pentagon are trying to reinvent personal flight and put an aircraft in every garage. But the engineering challenges remain as formidable as ever.
Even at its best, the Golden West Airshow in Olivehurst, Caliornia, is not one of the world’s premier aviation events. The annual weekend-long celebration of light sport and experimental aircraft usually attracts only a few thousand spectators to Yuba County Airport. This year’s turnout is especially light. High winds have kept some performers away and are preventing smallplane pilots from flying in to the venue, but the show must go on.
The pilots and prop-heads in attendance crane their necks to watch pairs of Aerobatic Racing Challenge biplanes corkscrew through a sequence of complex aerial manoeuvres. Other visitors wander the booths seeking memorabilia, airplane sales pamphlets or overcooked hamburgers.
Away from the flight line, about 25 people are seated inside a hangar, only partly sheltered from the gusts blowing through the open door, to hear a speech titled “Move over, Jetsons!” Sam Bousfield, founder and president of Samson Motorworks, picks up a handheld microphone and begins to tout his flying motorcycle, the Switchblade. “It’s two vehicles in one, an airplane and a car,” he says. “Go pick up groceries, drop off your grandma at the beauty salon, fly to San Francisco.”
A 1,2-metre model of the aircraft sits on a folding table in front of Bousfield, its narrow nose inclined at a slight angle for maximum viewing impact. The race-car-sleek lines, tinted windows, curved rear aerofoil and bright red paint are designed to reel in investors and re the imaginations of pilots.
Bousfield also uses the model as a prop to describe the craft: it’s a two-seat, threewheeled vehicle sheathed in a lightweight carbon-fibre shell. An owner would drive the Switchblade to anywhere a general aviation aircraft can take off, then swing out the wings and extend the telescoping tail to prepare for flight. When the Switchblade returned to the ground, the pilot would button down the flight-control surfaces inside clamshell doors underneath the chassis.
Samson Motorworks plans to sell the Switchblade as a kit aircraft at a price of about R400 000, meaning that owners must buy an engine and construct at least 51 per cent of the finished product. The final price could reach R600 000, comparable with other kit aircraft. “Why would I spend my time and investors’ money coming up with something as wild as this?” he asks the audience. “When I look at aviation, the only thing wrong with it is that it’s not done enough.”
But as the Q&A session after the speech makes clear, the audience members have not been fantasising about the Jetsons, Blade Runner or The Fifth Element. They have more pragmatic considerations on their minds.
“Does it have legal clearance for California roads?”
“Is the wing retraction mechanism manual, hydraulic or what?”
“Is it possible to put in a four-cylinder engine, like a Subaru’s?”
Even though Bousfield fields each question with enthusiasm, no one puts down a R14 000 deposit. If a rousing speech cannot convert pilots into customers, perhaps a demonstration of the hardware will do the trick.
But the flying-car prototype in Samson Motorworks’ Booth A-27 bears little resemblance to the Ferrari-inspired model in the hangar. For one thing, it’s missing certain design elements common to aircraft – like wings. The vehicle, a triangular lattice of bent steel tubes enclosing two seats and a rear-mounted engine, is more dune buggy than airplane. Bousfield and his employees stayed up until 2 am preparing this kluge of a skeleton for the first test of the Switchblade’s drivetrain, suspension and steering.
Bousfield is not just the company’s president, he is also its test driver. He climbs into the prototype.
“It’s our inaugural flight,” he announces to a dozen onlookers. “Well, not quite a flight.”
He turns the ignition, the 1 340-cm3 four-stroke four-cylinder engine roars, and the Switchblade scoots across the asphalt. When Bousfield reaches the end of a row of hangars, he slows and makes a sharp turn – the Switchblade’s first. The metal cage handles the manoeuvre with ease. On the return leg, feeling more confident, he mashes the accelerator and the Switchblade speeds to 65 km/h. Back at the booth, Bousfield is exhilarated that the prototype passed its first – and very public – test. But the onlookers just want to know about the turn radius, aileron control and take-off and landing performance criteria.
In Yuba County, flying-car fantasies are a tough sell.
The air show demonstration may seem humble, but the Switchblade is far closer to reality than most flying-car concepts ever get. The history of roadable aircraft, as their proponents call them, is littered with frustrated ambitions. Glenn Curtiss’s failed 1917 Autoplane, which was supposed to usher in an era of ubiquitous flying-car ownership, was the first of many disappointments. Over the decades, dozens of companies have drawn blueprints, built prototypes and solicited investor money, and ended up with almost nothing to show for their efforts.
Why have so many talented dreamers failed to make the flying car a reality? The answer: physics. Cars and aircraft operate in very different environments, so building a car that doubles as a plane results in an inferior version of both. The challenges are so intractable that flying cars have become a cultural punch line, a metaphor for technological promises that never come true.
Despite all that, the dream is very much still alive. Over the past 10 years, scores of start-up companies have proposed a new generation of dual-purpose vehicles. In 2010, the I-TEC Maverick, which is a dunebuggy- style vehicle with a pusher prop and parachute, was cleared for flight by the FAA and for the road by the state of Florida.
Other outfits have dodged fly-drive pitfalls by designing personal air vehicles that require neither roads nor runways. Martin Jetpack has lined up funding to build a factory that will produce a backpack mounted with shrouded propellers. In addition to these private sector players, the Pentagon is funding a flying Humvee programme; Nasa is designing a one-person electric helicopter/small-aircraft hybrid for commuters.
This renewed interest has been spurred by changes in aviation, including the widespread use of lightweight carbon-composite materials, the advent of smarter flight control computers and new civil aviation regulations that reduce training requirements for pilots of small aircraft.
It seems like a hopeful time for the flying car. “The appeal is obvious,” says R John Hansman, director of the MIT-based International Centre for Air Transportation. “There’s always a market – if you can do it well.” But the odds – and the physics – are still stacked against the enthusiasts.
Cars with identity crises
The Transition, the most advanced flying car in the United States, rolls down a runway, gathering speed at the start of its test flight. The pusher propeller at the back of the car buzzes loudly as the nose lifts and the car lurches into the grey skies over Plattsburgh, New York.
Once airborne, the Transition prototype looks like a bulky light-sport plane, with a bulbous fuselage, an 8,1-metre wingspan, a slender twin tail and a wide front bumper that doubles as a canard. The flight is brief, about a minute. The Transition does not rise higher than 100 metres and never veers from the safety of the 3-kilometre runway, which was designed to accommodate massive B-52 bombers. The test pilot uses every bit of the long stretch of asphalt to set down.
Terrafugia quietly conducted this milestone flight in March 2009, away from the eyes of the public and press. (The company has released videos of only three of Transition’s 28 test flights.) If Samson Motorworks is trying to be the showy cardinal of the flying-car world, then Terrafugia is content to be the secretive thrush.
Formed by five MIT graduate students in 2006, the company is built on solid engineering and tech-business roots. Carl Dietrich, who spearheaded Terrafugia’s creation while he was still working on his PhD in aeronautics and astronautics, wants to build a product for pilots who don’t want to pay for hangar space. It’s a practical business model applied to an infamously impractical idea. “People tend to have popular-culture visions of flying cars,” Dietrich says. “The reality does not match that set of expectations. However, the reality is Transition offers a freedom that does not exist in the aviation market.”
The Transition is a car that has been adapted for flight, and that simple fact brings some serious limitations to its performance as an aircraft.
During take-off , for example, an aircraft’s wings must be at a certain angle, at a certain speed, to generate enough lift for flight. When a pilot reaches take-off speed, he pivots the plane’s nose over its centre of gravity, a manoeuvre called rotation.
Most engineers position the main landing gear close to the aircraft’s centre of gravity for easier rotation, which allows for take-offs and landings at relatively slow speeds on short runways. But Transition’s wheels – like those on most flying cars – are at the perimeter of the chassis. And for good reason: if a car’s wheels were at its centre of gravity, a pothole or speed bump could flip the vehicle. But, Dietrich admits, “it makes for some different take-off dynamics.” In other words, Transition owners will need to find long runways.
“Look at the video,” says aeronautical engineer Austin Meyer of the Transition’s test flights. “The pilot has the elevator fully deflected and he can still barely raise the nose.” Meyer is the creator of X-Plane, the leading flight simulator for personal computers. Other simulators use data from test flights to plug into simulations; X-Plane can predict how an aircraft will handle in flight while it’s still being designed.
The simulation models the aerodynamic forces on aircraft parts: a wing is not judged as a single component; it is split into dozens of sections, each of which is evaluated separately. When Meyer flew the Transition in his simulation, he found that its twin vertical stabilisers, canards and external wheels created enough drag to degrade the flight performance.
Even supporters acknowledge the vehicle’s limitations. “The Terrafugia guys have done a good job,” says MIT’s Hansman, who advised the company. But no matter what, “it’s a compromised car and a compromised airplane.”
The Switchblade tries to avoid this conundrum by placing its three wheels in a confi guration similar to an aircraft’s.The large rear wheels remain at the edge of the vehicle, like a car, but Bousfield promises a quick take-o since the craft needs to lift its nose only 4 degrees to fly.
But X-Plane’s Meyer says the Switchblade faces other aerodynamic problems. When he tested the components, using the company’s specs, he found the aircraft’s small stabilisers – located behind the rear wheels for a convenient automobile layout – were not effective at steadying it during level flight. “It could be flyable,” Meyer says. “But the flying characteristics would be poor.”
The difficulties of engineering a flying car are also found under the bonnet. In flight mode, the Switchblade routes power from its motorcycle engine to the blades of a ducted fan, whereas the Transition uses its plane engine to power a pusher propeller. In the case of the Switchblade, the engine’s duty cycle will be far different in the air to what it will be on the ground.
The driver of a land-based vehicle frequently accelerates, stops and turns. The engine’s revolutions per minute (1 000 to 6 000 r/min) and power curve aren’t broad enough to accommodate this speed range, which is why a car engine is fitted with a transmission. A small aircraft’s engine runs at a lower, but relatively constant, 2 000 to 3 000 r/min and, unlike a car engine, generates nearly maximum torque at full load for most of its operation.
Some recreational pilots use car engines for aircraft, but adapting them is complicated. The pilots need to figure out ways to dump heat, since the thin air and high load make an engine in flight work harder than one in use on the ground. To increase reliability and to prevent overspinning of the prop, the repurposed car engines are configured to run slower, and the bearing clearances are enlarged, which increases oil flow and helps cool the engine.
Due to the differences in performance and operating temperatures, powertrains adapted for both flight and road work tend to be heavier, more complex, less reliable and more expensive than single-use engines. Engineers are aware of the problems that trade-offs can cause. “They’ve got reasons for their decisions,” Meyer says. “But the reasons usually come down to basic laws of physics that prohibit cars from ever flying efficiently.”
UNCLE SAM’S PUFFIN
Known as a loner, the pu. n is an awkwardlooking bird with wings that seem too small for its rotund body. It’s appropriate, then, that engineers at Nasa adopted the moniker for their bizarre one-person aircraft that takes off from an upright position.
Mark Moore, an aerospace engineer at NASA Langley who designed the Puffin, is not interested in trying to meld airplanes and automobiles. Instead, he envisages a radical personal aircraft with only one mission – to deliver a commuter to his office. On a budget of less than R7 million, Moore designed the Puffin to avoid gridlock.
Here’s how the Puffin could redefine a typical commute: a rider walks to his backyard, steps into the cockpit, enters his destination into the flight-control computer and takes off . Two electric engines, powered by 50 kilograms of lithium-phosphate batteries, are so quiet that the rest of his family doesn’t know he’s leaving for work.
The commuter steers the Puffin with a two-axis joystick to indicate direction and speed, and the flight-control computer translates the input into movement of the Puffin’s control surfaces. Always on some level of autopilot, the craft would not obey dangerous commands.
At a predesignated altitude, automatic controls take over. Instead of rotating its engine nacelles, like a traditional tilt-rotor aircraft, the Puffin tips its entire body (and its passenger) over on to its belly for forward motion through a flight corridor – a sort of bicycle lane in the sky.
In Moore’s world, airspace is open to unmanned aerial vehicles. In reality, the FAA has been reluctant to allow UAVs to share the sky with airliners, sport aircraft and helicopters. The Pentagon is leading the effort to draft the rules and de. ne the technical standards that will open airspace.
Pressure is mounting to do so as national government and local agencies develop plans for using drones to monitor weather, provide tactical reconnaissance for police or conduct environmental studies. So commuting in a Puffin would be like hitching a ride on a UAV studded with collision-avoidance sensors and wired for direct communication with other aircraft and sensors on ground infrastructure.
Flying in a prone position might be unacceptable to most commuters. But there’s one thing Moore does not have to worry about that consumes flying-car companies: marketability. The government’s role, Moore believes, is to come up with the innovations and regulations needed to finally build a flexible point-to-point transportation system. What companies sell, and what products customers will actually buy, is another matter. “Let the private market . gure it out,” says Moore. “It always does.”
6 new ways to fly
Players on aviation’s fringes are producing radical personal aircraft that go beyond the flying car.
Vehicle/Developer: M400X Skycar/Moller International
Type: Vertical takeoff and landing (VTOL) aircraft; prototype
Description: The Skycar points four ducted fans down to take off vertically; the fans swivel to provide thrust during flight.
Status: Inventor Paul Moller has been developing the concept for nearly 50 years. To date, the
M400X has only hovered on a tether.
Vehicle/Developer: Martin Jetpack / Martin Aircraft Company
Type: Ultralight personal helicopter; commercial product
Description: A rider uses two petrol-driven, 52 cm diameter ducted rotors to fly up to 50 km at an FAA mandated maximum speed of 100 km/h.
Status: In 2010, Martin landed an R80 million outside investment to build 500 packs. They will
be sold to governments and defence ? rms for R700 000 each.
Vehicle/Developer: CarterCopter / Carter Aviation Technologies
Type: Autogyro rotorcraft; prototype
Description: Wings and a twin-boom tail help the helo fly at slow rotor speeds, but it can hover for only seconds. On June 17, 2005, it broke a record for slow-rotor flight but crashed later that day.
Status: Carter engineers are building a larger prototype. The company, founded in 1994, is still seeking a partner to commercialise its manned and unmanned designs.
Vehicle/Developer: Maverick / I-TEC
Type: Roadable, powered-parachute buggy; commercial product
Description: Florida-based I-TEC designed this R550 000 off-roader for missionaries in the Amazon. It stays aloft using a parachute and rear propeller.
Status: PM gave I-TEC a Breakthrough Award in 2009. In late 2010, the Maverick became the
second US flying car to be declared street- and air-legal; the ?first was approved in 1956.
Vehicle/Developer: Milner AirCar / Milner Motors
Type: Roadable aircraft; prototype
Description: This four-door car, about the size of a Honda Civic, has a foldable main wing in the rear of the vehicle and a canard in front.
Status: Milner’s designers have driven, but not flown, the AirCar. The company is seeking an aeronautical ? firm to conduct flight tests intended to validate the prototype’s design.
Vehicle/Developer: Transformer TX / Defence Advanced Research Projects Agency
Type: VTOL Humvee; government research project to create prototypes
Description: In 2010, the Pentagon selected companies to design two versions of a flying jeep. One design uses an exposed rotor and wings; the other, ducted fans.
Status: The Pentagon gave Lockheed Martin and AAI, a unit of Textron Systems, R20 million each to build prototypes as part of a R370 million programme.
Roadworthy VS Airworthy
Made to drive
Engine: Engines are designed to withstand varying r/min, since drivers constantly speed up and slow down.
Wheels: Car wheels are at the perimeter of the vehicle, away from the centre of gravity, to provide stability.
Airfoils: Features such as spoilers disrupt airflow that generates lift to ensure a car grips the road as it accelerates.
Made to fly
Engine: When flying, aircraft engines run at a near-constant r/min that is about half a car’s maximum.
Wheels: Landing gear is near the centre of gravity so a pilot can easily raise the aircraft’s nose for take-off.
Airfoils: Aircraft are shaped to generate more lift the faster they go; wings bend airflow to maximise the effect.
Flight of the Puffin
How Nasa’s single-rider concept craft will avoid traffic-clogged commutes.
1. READY FOR LIFT-OFF: The rider steps into a pressurised cabin and straps in, standing up. He starts an almost totally automated flight by entering a destination into the flight-control computer.
2. RISE UP: The Puf?fin is classi?fied as a “tail sitter”. As the 2,3-metre props spin, the craft ascends and the legs fold together to form a tail.
3. TIP OVER: Instead of rotating the nacelles, the Puf?fin pitches forward to fly like an aeroplane.
4. FLY FACEDOWN: The Puf?fin cruises at 250 km/h and soars up to 9 000 metres. Lithium-phosphate batteries power flights of up to 80 kilometres – long enough to complete the average commute.