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Most commercial planes (and certainly almost every civilian airliner?) have an inertial reference system that is backed up by GPS. The inertial reference syste
by aaronmdjones 10y ago
Most commercial planes (and certainly almost every civilian airliner?) have an inertial reference system that is backed up by GPS.
The inertial reference system is a physical unit that cannot be externally manipulated, but it has less accuracy. If the plane's flight management computer detects that the GPS significantly disagrees with the IRU, it will warn the pilots, and may automatically disable the GPS unit.
Planes can also obtain position data via 2 VOR radials, or a single VOR-DME radial, or such. There are many options.
To provide redundancy, there are usually 2 or 3 IRUs.