EFFECTIVITY
GJ ALL EXCEPT B-2509, B2510

K73438
Low Range Radio Altimeter Antenna Installation  5C8 
34-48-11  Figure 401 (Sheet 1)  Oct 20/85 
Page 402 

BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
EFFECTIVITY
GJ B2509, B2510

K75518
501  Low Range Radio Altimeter Antenna Installation 
Oct 20/85  Figure 401 (Sheet 2)  34-48-11 
Page 403 

BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.

LRRA RECEIVER-TRANSMITTER - REMOVAL/INSTALLATION
1. General
A.  The LRRA receiver-transmitter/s are located on shelf four of electronic rack E2. Each unit is retained in its mount by means of a knurled clamp nut.
2.  Remove LRRA Receiver-Transmitter
A.  Open RADIO ALTM-1 or RADIO ALTM-2 circuit breaker on load control center panel P18 or P6 respectively, as required.
CAUTION:  RADIO ALTIMETER CIRCUIT BREAKER MUST BE OPENED WHEN REMOVING OR INSTALLING A RECEIVER-TRANSMITTER TO AVOID DAMAGE TO UNIT.
B.  Loosen knurled nut-securing unit to rack mounting.
C.  Pull unit forward in mounting to disengage electrical connector and remove unit.
3.  Install LRRA Receiver-Transmitter
A.  Make certain circuit breaker in par. 2 above is opened for LRAA-1 or LRRA-2 R/T unit being installed.
B.  Position unit in mounting taking care to engage guide pins for proper mating of electrical connector.
C.  Engage and tighten knurled clamp nut.
D.  Close circuit breaker/s opened in par. 2 above.
E.  Test receiver-transmitter for satisfactory operation by performing LRRA system test in 34-48-( ), Adjustment/Test Section, as applicable.
F.  Remove electrical power if no longer required.
501 
Feb 20/84  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  34-48-21 Page 401 

LRRA HEIGHT INDICATOR - REMOVAL/INSTALLATION
1.  General
A.  A height indicator is mounted on each pilots instrument panel.
2.  Remove Height Indicator
A.  Open RAD10 ALTM-1 or RADIO ALTM-2 circuit breaker on load control center panel P6 or P18, as required.
CAUTION:  RADIO ALTIMETER CIRCUIT BREAKER MUST BE OPENED WHEN REMOVING OR INSTALLING A HEIGHT INDICATOR TO AVOID DAMAGE TO UNIT.
B.  Remove indicator from instrument panel and disconnect electrical connector.
3.  Install Height Indicator
A.  Check circuit breaker(s) in par., 2 opened, as applicable for indicator being installed.
B.  Connect electrical connector to indicator and secure indicator on mounting in instrument panel.
C.  Close circuit breaker/s opened in par. 2 above.
D.  Test height indicator for satisfactory operation by performing LRRA system test (Ref 34-48-( ), Adjustment/Test), as applicable.
E.  If testing complete, remove electrical power as required, and restore airplane to normal.
501 
Feb 20/84  B
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 34-48-31 Page 401 

ATC SYSTEM - DESCRIPTION AND OPERATION
EFFECTIVITY
GJ ALL EXCEPT B-2524

1. General (Fig. 1)
A.  The ATC (Air Traffic Control) system, when interrogated by a ground station, automatically transmits a pulse-coded reply signal to the ground station. This reply signal is used to identify and locate airplanes equipped with ATC equipment for air traffic control. The reply signal is used to display airplane range, bearing, altitude and identity on the ground station radar scope.
B.  The ATC system consists of two independent ATC transponders, two ATC antennas and a common control panel. The control panel enables selection of either the No. 1 or 2 transponder, and either No. 1 or 2 (when installed) air data computer for automatic altitude reporting.
C.  Electronics bus No. 1 and 2 supply 115 volts ac to the system through circuit breakers on P6 and P18, load control center-left and right.
2.  ATC Control Module (Fig. 1)
A.  Controls for the transponders are on a control panel located on the pilots' forward electronic control panel. The ATC control panel is common to both ATC No. 1 and ATC No. 2 (if installed) transponders.
B.  The four identification coding select switches set the 4-digit code in the display window. The TEST button when pressed, simulates a received interrogation. The IDNT button when pressed, causes an identification pulse to be inserted in each transmitted reply pulse train. The REPLY light indicates the transponder is transmitting coded reply pulses. The FAULT light indicates a transponder or antenna fault.
　
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