GENERAL AEROSPACE
Boeing 737-300
MAINTENANCE MANUAL
EFFECTIVITY
PW245
34-53-00GA
DRAWING # GA-BC17-ATC-MM
Page 1
Use and disclosure shall be in accordance with the proprietary legend located on the cover of this document
AUG 15/10
ATC – DESCRIPTION AND OPERATION
1.
General (Figure. 1)
A.
The Air Traffic Control Radar Beacon System (ATCRBS or ATC), provides airplane tracking, altitude and
identification information to an ATC ground station. The ATC transponder responds to an interrogation
from an ATC ground station. The ATC system responds to ground station interrogations in one of three
different modes: mode-A, mode-C and mode-S. Mode-A and Mode-C provide identification and altitude
information. Mode-S provides selective airplane identification and data link capabilities. After a ground
station interrogation, the transponder automatically transmits a pulse coded reply signal in one of the above
modes. The mode of reply is determined by the mode of interrogation.
B.
Two ATC systems are installed on the aircraft, each with its own transponder. Only one transponder
operates at a time. A dual ATC Control Panel provides independent and isolated control for both systems.
Control information is sent to either transponder by discrete signals and an ARINC 429, 572, 718, or 730
bus.
C.
ATC antennas:
The bottom antenna is shared by the transponder 2 (Mode C) and transponder 1 (Mode S). A RF relay for
bottom antenna switches between transponders 1 or 2.
The top antenna is used by Transponder 1.
D.
Each transponder receives altitude data from Air Data Computer 1 (ADC-1).
E.
The ATC, TCAS and DME systems operate in the same L-band frequency range. A suppression circuit is
connected between the TCAS Computer, ATC transponders and the DME interrogators to prevent
simultaneous transmissions.
F.
The ATC system operates in three different modes: Mode-A, mode-C and mode-S. The mode of operation
is determined by the mode of interrogation from a ground station and the current configuration of the
altitude reporting function.
G.
The ATC-1 system receives 115VAC 400Hz, power from the electronics power bus No. 1. Power is
supplied through the ATC-1 circuit breaker located on the left load control center circuit breaker panel P18.
H.
The ATC-2 system receives 115 volt, 400Hz ac power from the electronics power No. 2 bus. Power is
supplied through the ATC No. 2 circuit breaker located on the right load control center circuit breaker
panel P6.
2.
ATC Control Panel (Fig. 1)
A.
The ATC Control Panel is located on the aft electronic control panel (P8). The Control Panel contains
switches and controls which provide reply codes and mode selection for two ATC transponders. The
Control Panel is divided into two operational systems No. 1 and No. 2. Each system. Each system provides
its respective transponder with tuning and control signals for system operation.
(1)
ATC Control Panel
The controls and indicators operate in the following manner:
(a)
The ATC keypad select the 4-digit identification code which is displayed in the ATC code
display window.
(b)
The transponder select switch activates the left or right transponder, as selected. Both
transponders are off with the switch in the STBY position.
(c)
The altitude reporting switch enables the transponder to reply with coded altitude information
supplied by left and right ADCs.
(d)
The identification switch causes the transponder to transmit a special pulse with each ATC code
reply generated. This is used to identify the airplane on the ground station scope.
