E&T reports on one of a new crop of flying cars: a futuristic unfolding vehicle made of carbon fibre, which is also one of the world’s most fuel-efficient planes.
If there is one form of transport less popular with environmentalists than the car, it's the aircraft. Friends of the Earth has called aviation "one of the fastest-growing threats to life on Earth", while Greenpeace warns that it "will ultimately kill millions of people". Both organisations are campaigning hard against the third runway at Heathrow, claiming that by 2050, emissions from the airport could account for over a fifth of the UK's entire carbon budget.
It's perhaps not the best climate, then, in which to introduce a high-tech combination of the two: a new flying car. Carl Dietrich is CEO of US-based start-up Terrafugia, whose Transition 'roadable aircraft' made its maiden test flight in March. The two-seater vehicle has folding wings that can convert it from a car to plane in just 15 seconds. "We're not competing with airlines," he says, "and the Transition will not replace jet aircraft for long distance travel. But it could be a game-changer for distances from 100 to 500 miles, at a price that would meet or beat driving, with huge time savings."
A plane that's more fuel-efficient than a family car? The concept isn't as ridiculous as it sounds. Unlike heavy passenger jet aircraft, the Transition is a lightweight, carbon-fibre vehicle relying on a modest 100hp engine to drive both its rear-facing propeller and its four wheels. On the open road, it will manage around 36 miles per gallon - better figures than the 2009 Volkswagen Passat CC, Toyota Camry or Mitsubishi Galant. Even up in the clouds, it'll match the mileage of a Mini Cooper scooting around town.
The trick to creating a practical flying car, confides Dietrich, is all in the weight. Make the vehicle too light and it won't handle well on the highway. Make it too heavy, and it won't fly. As if that wasn't hard enough, Dietrich also wanted his creation to qualify as a Light Sports Aircraft (LSA) in the US. That meant restricting the total take-off weight to less than 600kg - or about half the weight of a Mini Cooper.
"We started technical work on the Transition in 2004, just to see if it was possible," he says. "It turned out that it was. It is a significant technical challenge to keep the weight down but the potential reward is so large that we were able to attract investment." Meeting the LSA criteria gave Terrafugia useful design freedoms compared with a heavier aircraft, and also allows it to be piloted by beginners after a much shorter training period (as little as 20 hours).
To build the Transition, Dietrich gathered engineers from his previous employer, NASA, his alma mater, MIT, and specialists in composites fresh from designing America's Cup yachts and high-endurance solar-powered cars. The result is a futuristic vehicle that might not look revolutionary but that incorporates dozens of innovations - the most impressive of which is the electromechanical folding wing.
"This is the first really integrated design where the wings fold up automatically and all the parts are in one vehicle," enthuses Dietrich. "It's like a little Transformer. None of the controls ever disconnect, and that helps with safety, reliability and weight. We also incorporate safety features that prior concepts didn't, like safety cage and crumple zones that meet the insurance and national highway regulations for a 45mph crash test for frontal offset."
As a car, the Transition has a normal steering wheel, accelerator and brake pedals but no gear stick (it has a continuously variable transmission). The prototype has been driven as fast as 90mph and can fit (just) inside a domestic garage. In the air, the Transition has a top speed of 115mph and a range of up to 500 miles. It boasts modern glass avionics, including a full GPS system for navigation and even an emergency parachute.
"It just gives a pilot a new level of flexibility that he or she hasn't had until today," claims Dietrich. "You can throw your skis in the back of the Transition - it might be a two-hour flight instead of a six-hour drive. If the weather's lousy when you want to come back, you drive back instead, or perhaps you drive halfway."
This is perhaps the biggest eco-benefit, thinks Dietrich: "Any time that you can travel point-to-point and save miles from your trip, that's a win environmentally over following roads out of your way or being stuck in a passenger airline's hub-and-spoke system."
Flying is greener than driving in another way, as roadable aircraft contribute less particulate matter to the atmosphere in the form of emissions from tyre, brake and clutch wear. In the UK, Defra has found that around a third of all PM10 emissions (the 10-micron and smaller particles that have been linked to severe heart and lung conditions) come from road travel, with a quarter of these from tyre and brake wear alone (see 'Tyred of life?' p62).
Unlike jet aircraft, which use high-octane kerosene complete with polluting lead additives, the Transition's Rotax engine currently runs on unleaded petrol. Dietrich is keen to explore the possibilities of alternative fuels. "The Rotax 912S has been run on ethanol with a relatively simple modification and that's very appealing to us," he says. "We would love to offer the option to our customers but the engine manufacturer does not certify it for use with anything over 5 per cent ethanol, so we are not able to take full advantage of its potential."
Looking further into the future, hybrid and all-electric powerplants are starting to find their way into general aviation, just as they are in motoring.
The small Electric Aircraft Corporation of New Jersey has made a prototype fixed-wing plane called the ElectraFlyer-C that has already received its airworthiness certificate. This 175kg single-seater uses a 13.5kW (18hp) direct drive motor and 5.6kWh lithium-ion polymer battery to fly at up to 90mph for over an hour.
Dietrich is less convinced by such technology, though. "Even if the FAA [US Federal Aviation Authority] approves the use of an electric motor and battery combination for aircraft, there are huge performance penalties with that," he says. "We would have to be sure that the market would be there for such a change. Informal surveys suggest that an electric alternative is not something that the market would support."
The same goes for fuel cells, he says. "They have a much higher cost and lower performance. Even if we wanted to use them, as an LSA manufacturer we are bound by law to use appropriately certified aircraft engines, so until other engines that use alternative fuels become certified for use in an aircraft, we are quite limited."
Certification is a word that haunts Terrafugia. As well as meeting FAA regulations, it has to deal with the US's National Highway Traffic Safety Admin-istration (NHTSA). "We're bogged down in paperwork," admits Dietrich. "Fortunately, the NHTSA has an exemption policy for low volume manufac-turers like Lamborghini, as we can't afford to develop the new advanced air-bag systems that pop up all around you depending on who's sitting where."
Insurance companies are yet another hurdle. The $200,000 (£137,000) Transition could be the safest, greenest vehicle on the planet but if insurers won't cover it, it's destined to be stuck in the garage. "It's a real issue," says Terrafugia VP Dick Gerson, who previously worked for 22 years in the insurance industry. "The existing regulations, insurance and laws never contemplated a flying car. You have to be patient and find someone who shares your passion."
As the Transition edges closer to commercial reality, those people are coming out of the woodwork. Terrafugia hopes to deliver the first production model by the middle of next year and already has pre-orders to keep its production line busy for at least two more years.
"Terrafugia is committed to bringing one of the safest and most environmentally-friendly aircraft in the world to the general aviation market," says Dietrich. "I realise that it won't become a mass market item anytime in the near future. You'll have to be rich to start with but if it becomes practical then it will trickle down in cost. There will be competition and we'll inspire other companies if we've made a go of it."
In the meantime, Dietrich will take his successes where he finds them. The maiden flight - a 37-second stability and control exercise at a New York airfield - was a big boost. Perhaps even more significant, though, was getting a small, rectangular piece of metal through the post.
"It took us five months of explaining and persuading to get our first number plate," says Dietrich. "It turns out we are now the only registered manufacturer of automobiles in the state of Massachusetts."
This Transformer just earned its wings.