General Description; Introduction; Equipment Description; Mutual Suppression Pulses - Garmin GTX 327 Installation Manual

1.

GENERAL DESCRIPTION

1.1

INTRODUCTION

This manual describes the physical, mechanical and electrical characteristics, plus the installation
requirements and operating instructions for the Garmin GTX 327 Digital Display Transponder system.
Information pertaining to the maintenance, alignment and procurement of replacement parts is found in
the GTX 327 Maintenance Manual, Garmin P/N 190-00187-05. After installation of the GTX 327, FAA
Form 337 must be completed by an appropriately certificated agency and ATC transponder tests required
by 14 CFR, Part 91.413 must be completed to return the aircraft to service.
1.2

EQUIPMENT DESCRIPTION

The Garmin GTX 327 is a panel-mounted transponder with the addition of altitude reporting and timing
functions. The transponder is a radio transmitter and receiver that operates on radar frequencies,
receiving ground radar or TCAS interrogations at 1030 MHz and transmitting a coded response of pulses
to ground-based radar on a frequency of 1090 MHz.
As with other Mode A/Mode C transponders, the GTX 327 replies with any one of 4,096 codes, which
differ in the position and number of pulses transmitted. By replying to ground transmissions or TCAS
interrogations, the GTX 327 enables ATC to display aircraft identification, altitude and groundspeed on
ATC radar screens or TCAS traffic indicators. The GTX 327 is equipped with IDENT capability that
activates the Special Position Identification (SPI) pulse for 18 seconds.
The GTX 327 is configured with all key controls. The layout of the front panel keys and displays
segregates the transponder's primary functions from the secondary timing functions. The unit can be
configured so the aircraft avionics master bus can turn the unit on.
1.3

MUTUAL SUPPRESSION PULSES

Other equipment on board the aircraft may transmit in the same frequency band as the transponder, such
as DME or another transponder. Mutual suppression is a synchronous pulse that is sent to the other
equipment to suppress transmission of a competing transmitter for the duration of the pulse train
transmission. The transponder transmission may be suppressed by an external source and other
equipment on board may be suppressed by the transponder. This feature is designed to limit mutual
interference.
1.4

INTERFACE SUMMARY

The GTX 327 provides the following interface connections via the rear connector:
•
Ten (10) encoding altimeter inputs.
•
External IDENT input.
•
External STBY input.
•
External suppression pulse input.
•
Switched power output of up to 1.5 amps (for digital altitude encoder power).
GTX 327 Installation Manual
190-00187-02
Page 1
Rev J