Honeywell SPZ-8000 Pilot's Manual page 183

SPZ--8000 Digital Integrated Flight Control System
If radio altitude information is not valid, then distance is estimated as
a function of glideslope deviation and TAS. If neither radio altitude nor
glideslope data is valid, then distance is estimated as a function of TAS
and time.
Figure 8--18 shows the cockpit displays for the LOC TRACK phase of
flight.
Modes of Operation
8-22
Localizer (NAV) Mode Track
Figure 8--18
AD--58130@
AD--58131@
A28--1146--055
REV 2