Aerodynamic engineers interested in a new challenge should look up Airtrain, Inc. in Wichita, KS. The small group of aerospace industry veterans is putting together a high-speed ground transportation system that suspends a plane-like railcar from an overhead monorail.

As envisioned, the 70-seat railcar will leave the station much like a conventional monorail, with rollers supporting its weight on the rail. As the car accelerates past 85 knots, two sets of stub wings start producing lift and the rollers lift off the rail, dramatically reducing drag.

The car's connection remains centered around the overhead rail, however, using proximity sensors feeding data to a sophisticated flight computer which activates ailerons, rudders and hinged wingtips to maintain the optimal aerodynamic position. Only a spring-loaded electrical contact will remain touching the rail.

The Airtrain is to be electrically powered, using two motors driving ducted fans with variable-pitch blades. It also will have two vertical stabilizers. The rail is to be supported by arched stanchions placed every 100 feet. Project backers believe the above-ground monorail configuration and quiet electric motors will allow operation of the Airtrain in densely populated urban areas and reduce potential opposition to the system in the suburbs.

Airtrain is targeting markets where its speed will be an advantage, such as city-to-city transportation systems about 300 miles in length. Toronto to Montreal is one such route. Airtrain promoters are trying to interest the Canadian manufacturer Bombardier, which makes trains as well as business and regional jets, in the technology.

The Airtrain presents special aerodynamic challenges as it cannot crab into the wind like an aircraft. Boeing Technology Services recently completed computational fluid dynamics analysis of the vehicle. Project backers hope the existing aerodynamic control surfaces will be adequate to maintain rail clearance without requiring a complex gimballing system on the ducted fans. As it is, complex aerodynamics probably will rule out multiple railcar trains, they said.