An aircraft flying out of sight of land, using GNSS and ABAS (without SBAS), briefly loses power to the IRS. The navigation information of the IRS is lost due to the temporary power loss. What effect could this failure have on how GNSS is used during the flight?
Airborne-based Augmentation System (ABAS) is a type of augmentation system that is installed on-board aircraft. ABAS has two sub-categories: Receiver Autonomous Integrity Monitoring (RAIM) and Aircraft Autonomous Integrity Monitoring (AAIM). Therefore, ABAS = RAIM + AAIM.
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RAIM improves redundancy based only on multiple satellite signals and no external systems. It applies the technique of using more satellites in view than the minimum 4 that are needed for a 3D position fix. This method is using to verify the fixing information.
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AAIM uses additional on-board sensors (such as barometric altimeter and inertial reference system) to cross-check the GNSS position. It compares the 3D position with the navigation information from on-board systems and not with signals from other satellites.
=> If the Inertial Reference System (IRS) is lost, barometric altitude from AAIM and the RAIM function are still available.
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