Aspiring roadworthy aircraft designs multiply

Terrafugia, developer of the Transition flying car, is joined in the market by Scaled Composites' BIPOD and Carplane's Biomodal Convergence Vehicle.

In the news for several years, Terrafugia Inc. (Woburn, Mass.), developer of the composites-intensive Transition flying car, or as the company prefers, “roadable aircraft,” reported in June that it has received an exemption from the U.S. Federal Aviation Admin. (FAA) to allow the Transition a maximum takeoff weight (MTOW) of 1,430 lb/650 kg. This latest move in a series of efforts to gain approval for its hybrid design brought the Transition closer to commercialization, which the company anticipates within the next two years. But the Transition is no longer alone.

Scaled Composites (Mojave, Calif.) has developed a hybrid gasoline/electric competitor as part of an internal research and development program with the intent of strengthening its electric propulsion capabilities. The aircraft, dubbed the BIPOD, was the final design of Scaled’s founder and former CTO, Burt Rutan, prior to his retirement in April 2011.

BIPOD was conceived as a rapid, low-cost electric test bed, using as many COTS (commercial, off-the-shelf) components as possible. As Rutan’s retirement approached, Scaled pursued an aggressive schedule and successfully achieved first flight of the BIPOD vehicle within four months of beginning preliminary design. The entirely new design reportedly will operate as a high-performance airplane (maximum speed of 200 mph/322 kmh and 700-mile/1,125-km range), and serve as a urban commuter car, capable of freeway speeds, urban transport and garage storage.

The BIPOD’s twin fuselage configuration provides a low-drag enclosure for a robust, four-wheeled chassis with two cockpits (the right for flying, the left for driving) while providing a protected storage location for the wings and tail surfaces during ground operations. Internal combustion engines, one per fuselage, provide power to the rear wheels and to propellers located on the horizontal stabilizer. Scaled is continuing to test and develop the BIPOD configuration and hybrid propulsion system, with the goal of using similar systems on future unique aircraft configurations.

Speaking at the recent Experimental Aircraft Assn.’s (EAA) AirVenture event at Oshkosh, Wis. (see our AirVenture coverage on p. 45), Rutan said the vehicle’s short takeoff and landing (STOL) design enables it to take off easily from roads or clearings without the need for an airport. So far, it has been tested at high speed as a car and, EAA reports, flown briefly. Scaled is reportedly looking for a customer to fund further phases of the project.

Another road-bound aircraft (photo, p. 24) similar to the BIPOD, was unveiled in Germany in April. In development since 2008, the Carplane Bimodal Convergence Vehicle produced by Carplane GmbH (Braunschweig, Germany) uses composites in its construction, says project manager John Brown. The twin-pod Carplane, with electric motors for driving and an internal combustion engine for flying, is designed to be a light sport aircraft (LSA). Initially offered in kit form, it will conform to the emerging European Light Aircraft (ELA) standard, and the company is seeking partnerships for rate production. The way its wings fold and stow away during driving is unique and can be seen in a video at www.youtube.com/watch?v=Wpb3PkJDU_A.

Carplane composites will be sandwich constructions, cored mostly with honeycomb, but some foam. For preproduction vehicles, skins will be vacuum-infused dry glass fabrics, with some carbon and, for crashworthiness, hybrid glass/carbon fabric (50 g/m2 for small parts up to 250 g/m2 for larger components). In serial production, skins likely will be formed from prepreg over “hardened” tooling, said Brown.

Although several customers have offered to place orders, Brown says it’s simply too soon to accept them. “There is an informal waiting list, only,” he notes. “We’re not yet able to ... estimate when a production model will be available.”