Equipment Installation Manual,
GDC31 Roll Steering Converter
INTRODUCTION:
This Installation Manual contains installation data, specifications and Instructions for Continued
Airworthiness for the DAC International Model GDC31 Roll Steering Converter, Part Number 1049-
4000-XX-001( ).
DESCRIPTION:
The GDC31 Roll Steering Converter with software version 001( ) is designed to receive RS232 or RS422
serial data from a GPS Navigation System to produce both an analog Roll Sum Steering (RSS) signal and
ARINC 429 labels bank angle command and ground speed.
The GDC31 output signal connects to the heading error input of the aircraft’s existing autopilot. The
GDC31 mimics the heading error signal of the aircraft’s installed HSI or DG. The GDC31 does not
reduce or otherwise alter any existing safety features of the autopilot, such as bank limiting, rate limiting
and protection from a hard over. The GDC31 provides lateral (roll) data only (no pitch data is supplied by
the GDC31). The ARINC 429 output can drive digital autopilots or converters.
The pilot simply selects between heading mode and GPS mode using the supplied switch / annunciator.
In heading mode, the autopilot operates as always, tracking the heading bug of the HSI or DG. In GPS
mode, the GDC31 RSS signal drives the autopilot’s heading channel. The GDC31 calculates the correct
course intercept angle from the data supplied by the GPS, smoothly guiding the aircraft onto the course.
The GDC31 then holds the aircraft on the selected course. If the GPS is programmed with Flight Plan
data, the GDC31 will calculate the new intercept angle at each waypoint change, intercepting and holding
the new course without pilot intervention.
The GDC31 is designed to operate with both rate based and position based autopilots.
GDC31 RSC
SERIAL / FLAG
HDG
GPS
HSI / CDI
HDG ERROR
ROLL STEERING
HDG ERROR
ANNUN / SW
ARINC 429 OUT
GPS
AUTOPILOT
(GS, BANK ANGLE)
Block Diagram
1049-2510-01 G.doc
1049-2510-01
Rev G
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