The multi-mode receiver (MMR) contains the instrument landing system and the global positioning system functions. This section only covers the instrument landing system function.
The instrument landing system (ILS) provides lateral and vertical position data neccessary to put the airplane on the runway for approach. The system uses signals from a glideslope ground station and a localizer ground station.
The glideslope ground station transmits signals to give the airplane a descent path to the touchdown point on the runway.
The localizer ground station transmits signals to give the
airplane lateral guidance to the runway centerline.