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The Delco Carousel — proper name Carousel IV — was a popular INS-based navigation automation system for aircraft developed by Delco Electronics. Before the advent of sophisticated flight management systems, Carousel IV allowed pilots to automate navigation of an aircraft along a series of waypoints that they entered via a control console in the cockpit.
Carousel IV consisted of an inertial measurement unit (IMU) as its position reference, a digital computer to compute the navigation solution, and a control panel mounted in an aircraft's cockpit. It was used for long overwater and over the North Pole aircraft navigation. Many aircraft were equipped with dual or triple Carousels for redundancy.
Operation was relatively simple for its day, a pilot or flight engineer would have to enter the individual waypoints by their latitude and longitude points, next the pilot or engineer would have to enter the starting location in latitude and longitude. The system used spinning mass gyroscopes and proof-mass accelerometers to measure movement from the start point. An involved calculation followed sampling those sensors to determine a current position relative to the surface of the Earth.
The Carousel IV system derives its name from the fact that the inertial reference platform was rotated 180° every 60 seconds as a technique to reduce drift and increase accuracy by countering systematic errors. Low drift operation was aided by maintaining the gyroscopes and accelerometers at a constant temperature of 60 °C. The elevated temperature was maintained even when the aircraft was parked or undergoing maintenance.
Carousel IV was used in a number applications.
• Military: C-5A/B, KC-135 and its derivatives, C-141 • Missiles: Thor IRBM, Titan II ICBM, Titan III heavy lift launch system • Spacecraft: Apollo Command Module (IMU only) • Commercial: Boeing 747