GPS Align In Motion of civilian strapdown INS

Strapdown inertial navigation systems require an initialization process that establishes the relationship between the aircraft body frame and the local geographic reference. This process, called alignment, generally requires the device to remain stationary for some period of time in order to establish this initial state. This paper describes an alignment process where the initialization occurs while the device is moving. This is possible because an accurate determination of the aircraft motion is available based on measurements obtained from GPS. Align In Motion allows initialization of a Strapdown Inertial Navigation System while an aircraft is moving, in the air or on the ground. This is accomplished using Civilian grade GPS and an inertial reasonableness test, thereby allowing commercial data integrity requirements to be met. Align In Motion has been FAA certified to recover pure INS performance equivalent to stationary align procedures for civilian flight times up to 18 hours. This Align In Motion capability allows the removal of dedicated backup batteries on aircraft resulting in weight, cost, and reliability improvements. Align In Motion also has benefits for aircraft operations on the ground, on board ship, and in the air such as reduced turn backs, quicker dispatch, and world-wide alignment including polar regions. This paper will describe an avionics architecture using Align In Motion. It will cover INS warm start and cold start following a power interrupt with recovery to full inertial navigation capability without pilot interaction. Successful flight test results will also be presented.