IN order to make an examination of the fundamentals of air cargo transport, this very complicated subject has been simplified by assuming values for some of the less important variables that are consistent with practice and that may be obtained for specific conditions of flight, if not for a wide range of conditions in any one plane.
The first step in this study of the fundamentals of air cargo transport is a discussion of the division of useful load into fuel and cargo. To compare planes with each other, a term called Ultimate Range has been introduced, which is the range possible in still air, if all the useful load were given up to fuel.
The next step is an examination of the effect of speed on the quantity of cargo which may be delivered in a given time. A term called the Delivery Factor has been introduced as a means of comparing various aircraft on this basis.
This paper examines both the airplane and the airship as cargo carriers. One of the points brought out in regard to the airship is that it develops its highest delivery factor when the fuel used is one-third of the useful load, or one-half of the cargo load, regardless of the length of voyage or size of the ship. This means that the ship's speed for maximum delivery factor would be adjusted so as to consume one-third of its useful load as fuel, regardless of the length of the voyage.
Another point of comparison is the fuel used per ton-mile, which may be a matter of considerable importance where there is a fuel shortage. This is a point where the airship has a pronounced advantage over the plane, especially on long voyages.
In conclusion, it is shown that the fact that an airship can fly at moderate speeds well below those of airplanes, makes possible higher delivery factors for very long voyages than for planes, these airship speeds nevertheless being well in excess of surface speeds at sea.