Schuler pumping of inertial velocity errors due to gravity anomalies along a popular North Pacific airway

Gravity anomalies have long been a major error source for high precision inertial navigation, but were thought to have a minimal effect on the performance of the less precise inertial navigation systems used for commercial air transport. For the most part that is true. However, there are isolated areas where gravity anomalies are so significant that they become the dominant error source even for a commercial air transport inertial system. One such area, the Kuril trench, lies directly along a popular North Pacific airway. The anomalies along this airway not only are very large but vary in such a way as to Schuler pump the inertial velocity errors when flying at cruising speed. This paper describes the results of a recent night test program which led to the discovery of the unique variations along this airway.