The inertial navigation system provides information similar to that supplied by a doppler system, and it also gives readings of latitude and longitude when desired. The inertial system utilizes extremely sensitive gyros and accelerometers to develop signals from which navigation information is computed.

The heart of the Collins INS-61 inertial system is the inertial sensor unit (ISU) which contains the
inertial measurement unit (IMU), the system power supply, and the battery charger. The IMU is manufactured by the Kearfott Systems Division of Singer- General Precision, Incorporated.

This unit contains a stabilized platform on which are mounted two 2 degrees-of-freedom gyros, a two axis accelerometer, and 401 a single-axis accelerometer. The stable platform is isolated from angular motions in the aircraft by a shock-mounted gimbal system providing isolation from aircraft vibration.

The IMU is contained within a fixed outer frame which serves to mount the platform, the IMU connectors, and the electronics for instrument compensation and electrical adjustments.

Aircraft pitch, roll, and heading data is provided by synchros mounted on the platform-gimbal axis. The gyros in the IMU sense pitch, roll, and yaw and produce signals which are converted to usable information by the computer.

Acceleration in any direction is sensed by the accelerometers, and this information is also employed by the computer to provide navigation information. The information developed by the computer is displayed on the control/ display panel.

The following information is available: track angle and ground speed, true heading and drift angle, crosstrack distance and trackangle error, present position in latitude and longitude, latitude and longitude of any of the nine way points stored in the system, wind speed and direction, distance and time to the next way point, desired track, from or to a way point, way-point alert, system-failure warning, battery mode of operation annunciation, and attitude reference-mode annunciation.

Desired information is displayed when the selector switch on the control/display panel is rotated to the appropriate position.

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