PRIMUSr 1000 Integrated Avionics System
A28--1146--112--00
System Limits
7-2
Glideslope (GS) Gain Programming as a Radio
Altitude (RA) Function
Gain programming starts after the VBS trips. The gain is programmed
as a function of RA. If the RA altimeter is invalid, gain programming
occurs at GS capture and is controlled by a runway height estimator.
The value estimated is a function of GS capture, GS track, and middle
marker.AtGScapture,theheightisestimatedat1200feet.AtGStrack,
and the middle marker is passed, the height is 250 feet. Ifthe micro air
data computer (MADC) is not valid, or the true air temperature (TAT)
probe fails, airspeed is preprogrammed at 120 knots.
GS Gain Programming as a RA and Vertical Speed
(VS) Function
Gain programming starts after the VBS trips. The gain is programmed
as a function of RA and vertical speed VS. If the radio altimeter is
invalid, gain programming occurs at GS CAP and is controlled as a
function of VS, TAS, and time.
GS Capture (CAP)
The following conditions are required for GS CAP:
D Glideslope is valid
D Glideslope is armed
D The localizer mode is captured
D Glideslope deviation is less than one dot.
D Either of the following are satisfied:
- The VBS is tripped
- GS deviation is less than 20 mV.
Lateral Beam Sensor (LBS)
Whenflyingtointercept theVOR,LOC,orBCbeam,theLBS istripped
as a function of beam deviation, course error, TAS, and distance
measuring equipment (DME), if DME is available and not on HOLD. In
the VOR or LOC mode, the course error is compared with the beam
deviationsignalandrateofcrossingthebeamto determinetheLBStrip
point.
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