Inertial navigation has been in airline use for some five years and a substantial amount of experience has been built up. The system seems to have fulfilled the expectations of operators. In this paper, which was read at a meeting of the Institute in London on 8 January 1974 with the President in the Chair, Mr. Edwards of British Airways discusses its accuracy and the cost of ownership.

In 1969 a paper was presented to this Institute by F. J. Sullings of the then B.O.A.C. which described some of the engineering aspects of INS and predicted in some detail the costs of operating such equipment for a fleet of twelve B747 aircraft. It is the purpose of this paper to refer back to those early predictions and to make comparison with what has actually been realized. Sullings also referred to the anticipated navigational accuracy of the equipment and this paper will demonstrate that the anticipated accuracies have consistently been exceeded since the first use of the equipment by B.O.A.C. in May 1970. Finally, since the equipment has now been in use for five years, it is considered appropriate to review some developments in which airlines are taking an active interest.