Research and DevelopmentThe evolution of most aerospace products relies heavily on applied
Research. In the case of an aircraft,
designers use computers to generate mathematical models that are then used to simulate hundreds of different flight patterns. When a successful design has emerged from this process, extensive wind-tunnel research, using scale models of the plane and its components, verifies the final configuration. A full-scale vehicle is then fabricated. Its wings, fuselage, landing gear, movable surfaces, and other assemblies are subjected to simulated flight loads and operational requirements. The findings of the simulated flights are incorporated into one or more operational
aircraft, which undergo flight testing. For large airliners, testing may take several months. A complex military aircraft may require several years. When the aircraft finally enters production, the prime contractor assembles it from components and subsystems supplied by hundreds of subcontractors.Specifications relating to the function of the aircraft also play a large role in its design. For a military fighter, designers must
consider the types of targets to be attacked, the desired speed, fuel capacity, and range of the vehicle, and its weaponry, which will differ in planes intended for high- or low-altitude combat. A low-level combat plane will generally carry heavier armor plate, more specialized weapon-control systems, and equipment to reduce the threat of ground-based missiles. The manufacturer of the craft must also consider the man-hours required to supply and maintain the vehicle, as well as the training required for maintenance crews.Maintenance costs and training are also considerations in the design of civil aircraft. The length of runways and their load-bearing weight may influence the proposed gross weight of the plane, the design of its wings, and the configuration of its landing gear. Allowances must be made for different seating patterns for high-density and low-density routes. Performance requirements will vary for operations from airports in hot climates at sea level or cold climates above 1,500 m (5,000 ft).