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Comparing the IRS and INS, the IRS:

  • A

    Is cheaper.

  • B

    Is more precise.

  • C

    Uses a 4-axis model.

  • D
    Takes more time to align.

Inertial systems are the main source of attitude and navigational data in commercial transport category aircraft. The early generation of inertial systems is referred to as Inertial Navigation System (INS) and uses a gyro-stabilised platform, while more modern, “strap-down” systems are called Inertial Reference System (IRS).

The strap-down system dispenses with the gimbal mounted stable element and instead uses solid-state ring laser gyros (RLG). These gyros are not required to stabilise the accelerometers, as in the case of an INS, but provide aeroplane orientation, by determining the rate of rotation around each of the aeroplane axes.

The most significant error in the INS is produced by inaccuracies in its mechanical gyroscopes. This is eliminated with the IRS design using the more precise RLG technology.

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