Indicating instruments

The pilot is effectively part of the aircraft’s control system, and he needs to have a good indication of the results of his action. Figure 10.2 shows the primary instruments available on a typical light aircraft. In some aircraft, many of the individual instruments are now replaced by a display on a form of com­puter screen, as seen in Fig. 10.3.

Ailerons (roll control)

Rudder (yaw control)

Elevator (pitch control)

Fig. 10.4 The primary conventional control surfaces

Yaw control

On conventional aircraft, the yaw-control pedals are connected to a mov­able rudder, which is attached to the vertical stabiliser or fin, as illustrated in Fig. 10.4. Operation of the rudder effectively produces a camber of the vertical stabiliser surface, and this hence generates a sideways force. Less commonly, the whole fin surface is turned so that it is inclined to the flow. Since the side – force is applied well behind the centre of gravity, it produces a yawing moment.

For reasons that we shall give later, yaw control is not used as the primary means of changing direction, except when manoeuvring on or very close to the ground.

On large aircraft, several independently driven rudders may be provided (on a single fin), mainly for reasons of safety. The use of multiple rudders can also enable the balance between yaw and roll action to be controlled, according to whether an upper, or a lower rudder is used. On multi-finned aircraft, two or more rudders may be used, operating in parallel.