Specific transportation planning to answer these questions is quite complex and depends on many variables. It is possible, however, if certain assumptions are made, to assess the transportation feasibility of a particular plan of action. The purpose of this appendix, then, is to present a simplified method for calculating productivity in tons/day accurately enough to determine feasibility. The way the calculations are structured also shows how the process can be adjusted to accomplish achievable results.
Logistics productivity is measured in tons per day and is dependent on three primary factors: (1) the number of mission aircraft that can be kept functioning throughout the day; (2) the mission load that can be carried on each round trip or sortie; and (3) the number of mission sorties each aircraft can make in a day. The general formula is
The number of mission aircraft that can be kept functioning is the number of aircraft assigned adjusted by the average availability factor:
mission aircraft = assigned aircraft x % availability. 
For helicopters and tilt-rotor aircraft, there is a direct trade-off between useful load and fuel. Configured with a fuel-only maximum load, the aircraft can fly to the so-called "ferry range." The maximum round-trip range, with near-zero useful load, is here termed the "no-load distance," approximately half the ferry range. One could think of the no-load distance also as the maximum distance that a single passenger could be delivered under emergency conditions, and the aircraft returned without refueling. As shown in Figure D.1, the maximum useful load ≅ maximum "mission fuel" (≈ one-half the maximum all-fuel load). The fuel consumption per mile can be estimated as