Factors in the Design of Commercial Airplanes

Abstract

Abstract A steady and profitable market may be expected for existing equipment in remote and inaccessible places, where other forms of transportation are not available, but the real problem is to make the air transport compete successfully with the extra-fare trains. The real commodity that is being sold is transportation, and the factors involved are speed, comfort, and cost, assuming of course that safety and reliability have been demonstrated. The combination of these three factors must equal that of the fast train. The cost of air travel is of necessity high; therefore the speed-comfort combination must exceed that of the railroads. In general, the comfort of the train at least equals that of the airplane, so the latter must be sold on the speed factor alone, without sacrifice of a certain minimum requirement for comfort and at a cost that is justified by the increase in speed. Existing air transports have a high speed of 135 to 145 miles per hour, a capacity of ten to twelve passengers, and a power output of 100 hp. per passenger. The speed has been obtained by increasing the power per passenger to nearly double that formerly thought sufficient. High power means high fuel capacity and decrease in percentage of pay load. The author advocates the development of a 30 to 40 passenger airplane that will equal present speed requirements with a reduction of power to 50 to 60 hp. per passenger. To obtain this result he advocates abandoning direct-drive air-cooled radial engines and replacing them by geared engines, air-cooled or liquid-cooled, placed preferably inside the wing, with a remote drive to the propellers. The airplane itself should approach the flying wing, the wing loading should be high, and the landing gear should be retractable. Due to increase in landing speed the brakes should be much larger, should be operated by mechanical power, and should be capable of utilizing the full friction between the wheels and ground. The material from which the airplane is made will depend largely on a depreciation factor which is not yet clearly defined and cannot be set up until large airplanes have been in operation for a longer period of time.