A number of us can thank a cartoon character from the future, George Jetson, for instilling our longing. Students of aviation history might look for inspiration to the Autoplane prototype built in 1917 by the flight pioneer Glenn Curtiss. And tens of millions of motorists who have been stuck in traffic jams stretching towards the horizon must also feel a need to know: where are the flying cars?
It’s a dream that has reduced many would-be inventors to despair, as they grasped the immensity of the engineering and design challenges rooted in the widely divergent natures of airplanes and cars. Cars must provide occupants with comfort, decent handling, and braking and protection in the event of an accident—while complying with government air-pollution and fuel-economy standards. Keeping weight to a minimum is important, but a few extra pounds here and there can be tolerated.
Airplanes are quite a different matter. Weight is everything in a flying machine; it determines the engine power and the wingspan required to get off the ground. Thus, aircraft make extensive use of lightweight materials that their designers fashion into the most efficient structures they can dream up.
Trying to reconcile the conflicting requirements of the two types of vehicles invariably results in a boatload of compromises that, some say, make the flying car a non-starter. Yet the dream lives on.
Ray Morgan, a consulting aerospace engineer in Simi Valley, California, knows a lot about efficiency and lightweight structures, having led a group that developed a series of prototype aircraft, cars and blimps at AeroVironment. He has also studied flying car design. “In general, the idea that you are going to use an airplane for a car is just not realistic,” he said in a recent phone interview. “You are very likely to end up with both a bad airplane and a bad car.”
Over the years, flying car proponents have explored all sorts of propulsion systems, including propellers, downward-facing lift fans and helicopter-style rotors. Several small companies are working on flying car designs that they think will be the ones to finally crack the nut. One of these, Terrafugia of Woburn, Massachusetts, has flown a prototype with self-folding wings and a pusher propeller nestled between two tail booms. The company is working on an advanced hybrid design capable of vertical takeoff and highway driving using electric motors powered by batteries, along with a piston engine turning a pusher propeller during forward