Having dealt with the technical aspects of the development of a flyable / roadable vehicle, it is important to deal with the human side of using such a product.

One of the sound basic premises of design is called the KISS Principle. (Keep It Simple Stupid). However, if the simple technical answer creates difficulties for the operator, it will meet with out-of-hand rejection.

For instance, this could happen if a car driver is asked to steer his automobile with a joy stick. It is probably possible to do and would likely simplify the design of a dual-purpose vehicle. However, many people would be uncomfortable without the steering wheel in their hands. To them, this design would be totally unacceptable.

A similar problem could arise in the combining of the control systems of a car and a plane. It is conceivable that it would be possible to use the steering wheel as a method of yaw control while in flight. This would eliminate the rudder pedals and would seem to be a simple way to eliminate "control clutter" on the floor boards. Roll and Pitch control could be handled in another way, such as a joy stick, and technically, this would be easy to do. Engine power could be controlled by the gas pedal on the floor.

However, currently licensed pilots flying today's general aviation aircraft ordinarily use the wheel of an aircraft for roll control. They do not use a wheel for yaw control. Drastic changes in the established, familiar control systems presently in place could be dangerous for such a person. Remember, it is the established pilot who initially will be the prime market for any new design.

The human needs must be met in any new concept.