Air-position indicator Mk.1A

Air-position indicator Mk.1A

The Air Position Indicator was developed concurrently with the Air Mileage Unit during the Second World War and provides a continuous and automatic air plot, as well as showing the aircraft heading. No allowance, however, is made for wind speed.

The aircraft heading from the D.R. Gyro-Magnetic Compass through the variation setting Control, is obtained electrically and drives the repeater motor. Air speed is obtained from the air linkage Unit through a flexible drive, and this enables the heading to be resolved continuously into N-S and E-W components, which after conversion are fed to counters indicating Latitude and Longitude.