Navigation by the use of inertial information is now an accepted technique for military aircraft and for missiles. In civil aircraft the application of inertial techniques are, as yet, limited to defining the vertical and providing a memory of azimuth direction; that is, as aids to flight rather than a primary or even sole navigational aid. Although the principles applied—the inertial properties of matter and the laws of gravitation—are the same, the accuracy of the inertial sensors differs by some three orders of magnitude, and the cost by some two orders, between these two extremes.

Mr. A. Stratton of the Royal Aircraft Establishment first of all presents in perspective the range of application of inertial techniques that are available for civil use and suggests how the information obtained by inertial means can be related to that from other airborne sources. He shows that even if the expense of an accurate inertial platform of ‘navigational’ quality should not be justified, considerable advantage over existing sources obtains in terms of accurate attitude reference, and instantaneous velocity and acceleration, by the use of a lower-grade platform in conjunction with other navigation aids.