TM 55-1510-221-10
(6.) TEST pushbutton. Pressed to check
indicator R/T unit and flag operation.
Operating the test button causes the flag to come
into view and altitude pointer to indicate approxi-
mately 100 feet. Release of button causes pointer to
return to existing altitude and flag to retract.
3-25. VOR/LOC NAVIGATION SYSTEM.
a. Description. The aircraft is equipped with
two VOR systems, controlled by a dual NAV 1 -
NAV 2 control panel located on the pedestal (fig.
2-7). Either VOR can direct input signals to the atti-
tude director indicator. Controls are shown on figure
3-1. Each VOR system includes independent
receiver units for VOR/LOC and glideslope (GS).
Each VOR receiver provides a VOR input to a
respective RMI, HSI, and the flight director com-
puter. Each glideslope receiver sends GS flag and
pointer deviation information to the HSI and flight
director computer. VOR/LOC indicators may be
used for navigation during manual control of the air-
craft, or the autopilot may be coupled to the VOR
system, accepting VOR inputs to the autopilot com-
puter. The pilot’s unit (VOR 1) is a navigation radio
system which receives and interprets VHF omni-
directional radio range (VOR) and localizer (LOC)
signals, glideslope signals (GS), and marker beacon
3-30
Figure 3-16. Radio Altimeter Indicator (RA-315)
signals. It has a maximum range of 120 nautical
miles line-of-sight. The system operates in a VOR/
LOC frequency range of 108.00 to 117.95 mega-
hertz, in a glideslope frequency range of 329.15 to
335.00 megahertz, and at a marker beacon fre-
quency of 75 megahertz. VOR 2 is similar to VOR
1 except VOR 2 cannot receive or interpret marker
beacon signals. Each VOR system provides course
deviation and glide path data, which can be
switched either to the copilot’s HSI or to the autopi-
lot flight computer and pilot’s HSI, or both. The
audio outputs of VOR 1 and VOR 2 systems are
supplied to the NAV control on the audio control
panels. VOR 1 bearing data is supplied to the single-
needle pointer on both Radio Magnetic Indicators.
VOR 2 bearing data is supplied to the double-needle
pointer on both Radio Magnetic Indicators. VOR 1
uses a marker beacon antenna located on the under-
side of the forward fuselage (fig. 2-1). VOR 1 and
VOR 2 both use the same glideslope antenna,
located inside the radome. Both VOR’s are pro-
tected by separate 2-ampere circuit breakers, located
respectively on the number 1 and number 2 avionics
bus. The circuit breakers are placarded VOR No.1
and VOR No.2 are located on the overhead circuit
breaker panel (fig. 2-26).
