Cruising flight

For the most part, the flight of an aircraft can be divided into at least three dis­tinct phases – take-off and climb, cruise, descent and landing. In this chapter we will be primarily concerned with the cruise performance of the aircraft. Landing and take-off will be discussed later in Chapter 13.

The nature of the cruise will change depending on the use to which the aircraft is to be put. For example, a commercial airliner must operate as eco­nomically as possible, and so reducing fuel usage over a given route is of prime importance. However, as we shall see later, this is not the only factor that matters as far as the operator is concerned. For a patrol aircraft, such as the airborne radar system, AWACS, or a Police observation aircraft (Figs 7.3 and 4.9) endurance is likely to be the overriding consideration. For a fighter it may well be a combination of high speed, in order to make an interception, coupled with a need for either range or endurance, depending on the particular mission undertaken. In this case the ‘cruise’ phase of the flight can be subdivided. This is also true of other aircraft types. For instance, a commercial airliner must frequently spend some time in waiting its turn to land at a busy airport, and so an important ‘stand off’ phase is introduced, which is required purely for organisational purposes.