Litton LN3-2A - Inertial Navigation Platform - Moving 3 Gimbals

This is a Litton LN3-2A Inertial Navigation Platform from the sixties.
It was used in the Lockheed F-104 Starfighter and the McDonnell Douglas F-4 Phantom aircraft.

Its main purpose is navigation. With an Inertial platform, you do not require the use of external sources like radio beacons or GPS, and it does not emit any radiation like radar.

This is a short video showing the 3 main gimbals moving.

From the outside towards the inside:

- Outer Roll Gimbal
- Pitch Gimbal
- Inner Roll Gimbal
- Azimuth Gimbal

The Inner Roll Gimbal is not moving in this video.

The 2 main gyros and the gimbals are used to keep the inner platform holding the 3 accelerometers in a fixed position wrt the earth's surface.
The output of the accelerometers is integrated to get velocity.
The velocity obtained is one more integrated to get the distance.

Inside the orange gyros is a sphere floating in a fluid. The density of the fluid, the volume of the sphere, and its mass make the spere float in the fluid. (neutral buoyancy)
Inside this sphere is a 3-phase motor spinning a mass. (the actual Gyro)
When the gyro moves in one direction this results in a force moving the spinning mass in a perpendicular direction. This is detected by a pair of pick-up coils. The amplified difference signal of the pick-up coils is used to drive the correct gimbal. This restores the relation between the gyroscope housing and the floating sphere. The rotation of the gimbals keeps the platform with the 3 accelerometers stable wrt the earth.

Видео Litton LN3-2A - Inertial Navigation Platform - Moving 3 Gimbals канала Satadorus