FLYING IN FOGS.

Putaruru Press, Volume VII, Issue 287, 9 May 1929, Page 3

FLYING IN FOGS.

AVIATION DIFFICULTIES. One of the great d'fficult'es by ■which civil aviation is faced is that of maintaining a regular service under bad weather conditions. The problems arising under this category relate to control, navigation, and landing, but it is with the first of these that we are now concerned (says Engineering). When the pilot is deprived of his horizon the control of an aeroplane becomes exceed ngly d ffieult, in spite of the information which can be supplied by such instruments as turn indicators. Generally if the rudder can be operated so as to keep the aeroplane flying in a constant difetion, most of the difficulty disapars. It should be noted, however, tJiat observation of a magnetic compass is practically useless from this point of view, owing to the disturbances which arise from centrifugal force when the aeroplane departs from a straight course. For this reason, the automatic rudder control de--veloped at the Royal Aircraft Establishment relies for its sense of direction on a free gyroscope, or “gyro azimuth.”

The control consists essentially of a pneumatic ram servo-motor, which operates an auxiliary rudder bar and is controlled by an air valve attached to the azimuth ring of a gyroscope. The gyrq wheel is spun at high speed, and its axle is set along the line of the required compass course. Deviation of the aeroplane from its course entails relative movement between the arimuth ring and the aeroplane, s.nce the axle of the wheel maintains a constant direction in space. The consequent disturbance of the valve admits

compressed air tof one cylinder of the servo-motor and exhausts the other to atmosphere thus causing the servomotor to apply a correction to the rudder. To prevent the application of excessive rudder, the servo-meftor is also connected to the cas'ng of the valve, thus causing the valve to shut when the servo-motor has moved the required amount. This mechanism constitutes a “follow up,” and has the effect of making the rudder displacement proportional to the deviation of the aeroplane from the desired course.