It has always been important for military commanders to be able to rely on their equipment being available to them during a conflict. Some recent published figures, however, showed that two modern fighter aircraft were only available for missions for 47% or 56% of the time.

A simple operation simulation model was derived to show an aircraft's sensitivity to the main availability parameters. This model can be applied to any aircraft type provided that the necessary inputs can be calculated. The simulated operations were as realistic as possible, although many assumptions had to be made.

For reasons of national security it was not possible to relate this study directly to any current service aircraft, so a design project study has been used as the baseline aircraft in the simulation model. This aircraft was the 1980 Mini-CAS, developed at Cranfield Institute of Technology. This was used because all the necessary data were available or could be estimated with reasonable confidence and also the operating conditions are comparable to a number of current service types employed in the Close-Air-Support role. Thus the simulation was kept realistic and the results and conclusions are directly applicable to real and projected designs. Subsequent work checked the validity of the model by simulating an A-10 exercise and Sea Harrier operations in the Falklands conflict.

The Operations Simulation Model proved to be a satisfactory means of assessing the effectiveness of a force of aircraft under war-time conditions. It was far more flexible than the Availability and Mission Readiness equations commonly used to compare the in-service performance of aircraft and highlighted areas where resources could best be concentrated to improve availability. Further improvements are necessary however, to take account of spares shortages and the effect of adverse weather.