Military Avionics Systems

10Vehicle Management Systems

10.1 Introduction

The utility systems are a collection of fluid, air, mechanical and electrical systems associated with the provision of sources of power or energy to perform the general or utility functions of the basic air vehicle. This control is usually obtained by the performance of some functional activity resulting in the appropriate control of that energy to impart flow or motion. These systems are also known as:

• Flight systems;
• General systems;
• Aircraft systems;
• Power and mechanical systems;
• Vehicle systems.

Figure 10.1 shows the aircraft considered as a set of systems to illustrate the position of utility systems relative to the airframe, the avionics and the mission systems. These systems can and do operate autonomously, but there are important system interactions that need to be considered in the design of each system. Examples are:

1. Fuel is often used to maintain the aircraft centre of gravity within certain limits. This is especially relevant to an unstable fighter aircraft where cg has an impact on manoeuvrability and is dependent on fuel status and external weapons carriage.
2. Fuel is also used as a cooling medium, for example in fuel-cooled oil coolers, and its temperature needs to be carefully monitored.
3. Undercarriage oleo switches are used as an indication of weight on wheels, and these signals are used to inhibit some functions.

Figure 10.1 The aircraft as a set of systems.

The utility systems of an aircraft have a particular ...