Introduction to Aircraft Design

MILITARY AIRCRAFT TYPES

FIGHTERS

These aircraft have had several designations over the years, including pursuit and interceptor aircraft. There are many types, and definitions become blurred between fighters and bombers and ground-attack aircraft. True fighters may be divided into two major classes. The first class is that of relatively simple short-range interceptor aircraft (class 1), whilst the second used to be called ‘all-weather’ fighters which tend to have longer range and more avionic equipment (class 2). Figure 4.1 shows a plot of combat wing loading against thrust/weight ratio, which is a good indication of the manoeuvrability of combat aircraft (see Chapter 3 for the definition of thrust/weight and wing loading). Recent requirements for high agility have moved aircraft towards the top left-hand corner where high thrust/weight and low wing loading improve climb, sustained turn and attained turn performance. Most aircraft in this region are class 1 short-range fighters and class 2 are closer to the bottom-right quadrant, where the higher wing loading leads to better long-range cruise.

The class 1 short-range, high-performance interceptor carries the minimum of equipment and maximum speed is always important. However, for such an aircraft the rate of climb and manoeuvrability may be even more important. This arises from the fact that due to the fighter's necessarily short range it cannot take off until a target is definitely located, but must then rapidly climb to interception. A very high thrust/weight ratio is implied by these requirements, particularly at altitude. Compatible with reasonable operational safety, everything must be placed second to climb and interception performance. Only one crew member can be carried and acquisition and life-cycle costs are reasonably low. Due to the relative simplicity of the equipment carried, reliability should be high. The Typhoon is in this category (see Fig. 4.2).

The high thrust/weight ratio for combat manoeuvrability leads to the thought that only a little extra thrust might give vertical take-off and landing capability (VTOL). The BAE SYSTEMS Harrier has been developed into an extremely effective strike/bomber aircraft with the very significant operational advantage of lack of reliance on runways. The invention of the ski-jump runway improved payload/range by offering an extremely short take-off distance (STO). These innovations led to the extremely potent Sea Harrier interceptor aircraft flown from small aircraft carriers.