that secure the control unit. to the aircraft mounting
(1) Disconnect the cables from the front of there-
(2) Pull the control unit out of the aircraft mount-
(2) Loosen the two thumbscrews on the front of
ing panel and disconnect the cable from the rear of the
the mounting tray enough so that the lip on the bot-
tom of the receiver will clear the clamp.
(3) Lift the front end of the receiver slightly and
(1) Connect the control unit cable to the rear of
slide it off the mounting tray.
(2) Insert the control unit into the aircraft mount-
(1) Slide the receiver into the mounting tray. Be
ing panel and fasten the four turnlock fasteners se-
sure the lip on the rear of the receiver fits snugly
under the lip on the back of the mounting tray.
(2) Place the clamp over the lip on the front of the
3-13. Control Parts Replacement
receiver and tighten the two thumbscrews.
(3) Connect the cables to the front of the receiver.
(1) Remove the knobs by loosening the knob set-
3-11. Removal and
screws and sliding the knobs off the stems.
(2) Apply Loctite, grade HV, to the setscrews
when reinstalling or replacing the knobs.
b. Front Panel.
(1) Remove the receiver as described in paragraph
(1) Remove the control knobs as instructed in a
above. Remove the felt washers.
(2) Remove the screws that attach each of the
(2) Remove the two screws that attach the front
vibration isolators and the ground straps to the air-
panel and remove the panel.
frame and remove the mount.
c. Lamps and Lamp Filters.
(1) Remove the front panel as instructed in b
(1) The receiver mount is installed in the reverse
order of removal.
(2) Using tweezers or needle-nosed pliers, the
(2) Tighten the mounting screws.
lamp filters and lamps can be pulled straight out
3-12. Removal and Replacement of Re-
through the front panel.
c e i v e r Control C-10048/ARN-123(V)
Replace the lamp filters whenever the lamps
(1) Loosen the four captive turnlock fasteners
Section V. FLIGHT LINE TESTS
vent excessive drain on the aircraft battery.
Refer to the aircraft manuals for connection
a. The operational checks given in paragraph 3-15
and power requirements, and for setting of
are performed on the flight line with the equipment
communication power controls.
installed in the aircraft. These checks should be per-
b. The tests should be conducted at a location which
formed before removal and replacement of compo-
is free of electromagnetic energy reflecting surfaces
nents as the result of inflight problems or malfunc-
such as buildings, other aircraft, etc.
tions observed during operational checks (para 2-11)
3-15. Flight Line Operational Tests
and should be performed as part of the aircraft inter-
mediate preventive maintenance checks and services.
a. Test Setup.
Malfunctioning components should be removed for
(1) With the SET LINE TO 21V control OFF, con-
nect the SG-13/ARN to a 21- to 29-volt dc portable
bench testing in accordance with section VI or section
VII. The glideslope, VOR, and localizer tests are made
using Signal Generator SG- 13/ARN. The marker bea-
(2) Set METER switch to LINE.
con tests use Test Oscillator BC- 376. The aircraft and
(3) Rotate SET LINE TO 21V control for 21 0.5
receiver power must be on.
volts indication on meter.
(4) Set the MEGACYCLES control to 109.30
If the aircraft engines are operated during
(332.00 MHz), and set receiver frequency (in aircraft)
the following tests, the pilot or an authorized
to 109.30, or any frequency with a reported dis-
crewmember will start and operate the en-
gines. If the aircraft engines are not oper-
(5) Set AUDIO SELECTOR switch to GLIDE
ated, use an auxiliary power source to pre-