Design of Unconventional Commuter Configurations

This paper presents the results of an investigation into the design of advanced commuter configurations. The airplanes were required to carry 30 passengers over a 600 n.m. stage length at a cruise Mach number of 0.6 at an altitude of 28000 feet. The airplanes were required to have inherent static stability.

Five unconventional twin turboprop configurations were investigated. These consisted of three canard and two 3-surface configurations. To provide separation of passengers and crew from the plane of the propellers and engine turbine and compressor discs, aft-mounted pusher-propeller configurations were adopted. This also resulted in a saving in the amount of sound proofing (weight). High wing loading was chosen to reduce wetted area and achieve good ride qualities.

The combination of high wing loading and the required inherent static stability made it extremely difficult to realize canard configurations. In the configurations with wing-mounted engines, the aft positioning of the wing and hence the fuel tanks gave rise to rather large center-of-gravity travel and hence trim problems under certain flight conditions. The 3-surface configuration with pylon-mounted engines looked promising. Although a single canard configuration did not emerge, the configuration with pylon-mounted engines, again, appeared the most flexible.