Serial Data Input: .....................................................................................................................................10
Roll Sum Steering Output:.......................................................................................................................10
AP Offset Input:.......................................................................................................................................11
Flag Input:................................................................................................................................................11
Analog Output..........................................................................................................................................12
Super Flag Input.......................................................................................................................................13
Material Not Supplied..............................................................................................................................14
Special Tools............................................................................................................................................14
Figure 2 KI 525 / 525A with KA 52 / KA 57 ........................................................................................34
Figure 3 ARINC HSI with Century IV..................................................................................................35
Figure 4 ARINC HSI with S-TEC 50, 55 or 60.....................................................................................36
Figure 5 NSD 360A / NSD 1000 with Century IV................................................................................37
Figure 6 NSD 360A / NSD 1000 with S-TEC 50 or 55......................................................................... 38
Figure 7 ARINC HSI with Century II or III ..........................................................................................39
Figure 8 KI 525A with KFC 150 ...........................................................................................................40
Figure 9 NSD 360 with ARC 400B (10VAC)......................................................................................41
Figure 10 52D54 DG with STEC 50, 55 or 60 ......................................................................................42
Figure 11 NSD 360 with ARC 400B (DC)............................................................................................43
Figure 12 NSD 360 with Century 2000 .................................................................................................44
Figure 13 NSD 360A with Century II or III ..........................................................................................45
Figure 14 HSI-70C with ARC 1000 .....................................................................................................46
Figure 15 KI 525A with KFC 200 / 300...............................................................................................47
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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 10494000-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.
HDG ERROR
ANNUN / SW
HDG
HDG ERROR
HSI / CDI
GPS
ROLL STEERING
AUTOPILOT
SERIAL / FLAG
ARINC 429 OUT
(GS, BANK ANGLE)
GPS
GDC31 RSC
Block Diagram
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Equipment Installation Manual,
GDC31 Roll Steering Converter
PART NUMBERS:
The GDC31 Data Converter is available under the following part numbers:
1049-4000-01-
001( ) GDC31 Roll Steering Converter, ARINC 429 Low Speed
|
1049-4000-02-
001( ) GDC31 Roll Steering Converter, ARINC 429 High Speed
|
Software part number, where ( ) contains the number zero for initial release, or
any letter, A – Z to denote a minor change.
REGULATORY COMPLIANCE:
Software
The Model GDC31 software was developed in accordance with RTCA/DO-178B to criticality level C.
PMA
The Model GDC31 is approved via PMA.
Environmental
The Model GDC31 meets the DO-160D environmental categories listed later in this manual.
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Equipment Installation Manual,
GDC31 Roll Steering Converter
SUPPLIED EQUIPMENT
Each Data Converter is shipped with the following items:
Part Number Description Qty
1049-4000-01-001( ) GDC31 Roll Steering Converter, ARINC 429 Low Speed 1
1049-4200-10 Installation Kit, GDC31 Data Converter 1
Part Number Description Qty
1049-4000-02-001( ) GDC31 Roll Steering Converter, ARINC 429 High Speed 1
1049-4200-10 Installation Kit, GDC31 Data Converter 1
NOTE: The Annunciator / Switch, P10280, comes pre-configured for 28V operation. For 14V operation,
see the section titled INSTALLATION - Wiring Considerations.
Complete installation kits are available under kit part number 1049-4200-10. Individual pieces are
available under the part numbers shown. Contact DAC International sales to place orders.
Part Number Description Qty
1049-4200-10 Installation Kit, GDC31 Data Converter
Complete installation kits are available separately under kit part number 1049-4200-50. Individual
pieces are available under the part numbers shown. Contact DAC International sales to place orders.
The Isolation Coupler (optional) attaches to the airframe via four mounting holes. See the paragraph
titled Isolation Coupler Outline Drawing for further details.
Height.................................................1.25 in
Width..................................................4.5 in (Includes mounting flange)
General Description...........................AC or DC excitation used to excite the heading bug on the HSI
or DG. The GDC31 uses the reference input to produce a
steering signal with correct phase and amplitude characteristics.
Two reference inputs are provided. Use only one, depending on
the autopilot type. The unused input will be a no-connect. See
typical interconnect diagrams later in this manual.
AP Ref 1.............................................Reference voltage input for use with gain settings found in
Table 1.
Maximum Input Level ..................42 volts peak (30Vrms)
MTBF.................................................Greater than 50,000 hours.
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Equipment Installation Manual,
GDC31 Roll Steering Converter
OPERATION:
Overview
The GDC31 Roll Steering Converter receives RS232 or RS422 serial data in RNAV 0, RNAV 1, King 0
or King 1 format from a GPS navigation system. It extracts Cross Track, Ground Speed and Track Angle
Error information from the data stream to compute an appropriate bank angle command to return the
aircraft to the Desired Track computed by the GPS navigation system.
Analog Output
The GDC31 produces an analog Roll Sum Steering (RSS) signal that drives the heading channel of the
autopilot. Phasing and amplitude of the RSS signal is based on the reference input supplied to the GDC31
from the autopilot and the gain and phase settings established by the program pins (refer to Tables 1, 2
and 3). The GDC31 will accept either an AC or a DC reference input as well as reference inputs that
contain an offset from airframe ground. The internal circuitry implements a multiplying Digital-toAnalog converter that uses the external reference input to produce the desired signal output amplitude and
phase relative to the reference input. Certain installations (Century II and III, for example) will not accept
a heading error signal referenced to ground, so require the Isolation Coupler in order to transformer
isolate the GDC31 output signal.
Reference Inputs (Excitation)
The GDC31 contains two reference inputs to accommodate the wide range of reference voltages
available. Input Ref1 will accommodate excitation voltages up to a maximum input of 42 volts peak
(30Vrms). Input Ref2 will accommodate excitation voltages up to a maximum of 15 volts peak (15Vdc
or 10.6Vrms). The determination of which reference to use will depend on the gain needed to match the
autopilot scale factor as well as the maximum expected reference voltage. Certain installations (Century
II and III, for example) produce a reference voltage that is floating relative to airframe ground. These
installation require the Isolation Coupler in order to transformer isolate the GDC31 reference input signal.
ARINC 429 Output
The GDC31 produces an ARINC 429 digital output containing labels 121 and 312 intended to drive
digital autopilots or digital autopilot converters.
Equipment Installation Manual,
GDC31 Roll Steering Converter
GPS Mode Annunciator Control
The GDC31 contains a Normally Open relay contact configured as a SPST switch to control the external
GPS mode annunciator. This annunciator is further controlled by external switching and is active when
the pilot selects GPS mode in place of heading mode with the external switch. Refer to the typical
interconnect diagram later in this manual. If GDC31 output data is valid, the relay contacts are closed,
allowing the mode annunciator to illuminate. If the data is invalid, the GDC31 will cause the mode
annunciator to blink at a 1 Hz rate and command the steering output to zero degrees of bank (wings level).
The GPS mode annunciator blinks if either the super flag input is invalid or the serial data from the GPS
is missing or not the correct format (see Appendix A).
Super Flag Input
The GDC31 reads the Super Flag (14 or 28Vdc) from the GPS receiver. If the flag is greater than 5Vdc,
the flag shall be considered valid, if less than 2Vdc, the flag shall be considered as invalid. If the Super
Flag indicates invalid, the GDC31 shall produce a steering signal of zero degrees, blink the GPS
annunciator relay and invalidate the ARINC 429 label 121, bank command data, and label 312, ground
speed data.
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Equipment Installation Manual,
GDC31 Roll Steering Converter
INSTALLATION
This section provides details for the installation of the GDC31 Roll Steering Converter, including
configuration, wiring, mounting and checkout procedures. Follow the procedures and recommendations
found in this section to assure a successful installation.
Read this entire section before beginning the installation.
Prior to installation, determine the required scale factor and phasing for use with the aircraft’s autopilot.
Consider the location of the mode selector / annunciator switch; it should be installed within the pilot’s
primary field of view and easily accessible by the pilot.
Complete an electrical load analysis in accordance with AC 43.13-1B, Chapter 11 prior to starting the
aircraft modification to insure the aircraft has sufficient load capability.
Complete an aircraft weight and balance prior to aircraft modification to insure the aircraft has sufficient
weight and CG margin.
Material Not Supplied
The following items are required for the installation but not supplied:
• Wire: MIL-W-22759/16 or equivalent
• Shielded Wire: MIL-C-27500 or equivalent
• Mounting screws: MS35206 6-32, 4 each
• Circuit Breaker: Klixon 7277-2-2 or equivalent
• Tie straps or lacing cord
• Ring terminals (for grounding)
• Splices
Special Tools
Use the following crimp tool to ensure reliable crimp contact connections to connector J1.
• Crimp tool M22520/2-01
• Positioner M22520/2-08
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Equipment Installation Manual,
GDC31 Roll Steering Converter
Mounting Considerations
The GDC31 Roll Steering Converter can mount in the avionics bay, shelf or other suitable structure. It
can be mounted in any orientation.
The optional Isolation Coupler can mount in the avionics bay, shelf or other suitable structure. It can be
mounted in any orientation.
Attach the GDC31 and Isolation Coupler to suitable structure using the following hardware.
AN or MS self-locking nut plates may be used in place of the nut and lock washer specified above.
Mount the GPS/HDG mode annunciator / switch as near as practical to the autopilot mode controller. If
there is insufficient space there, mount the mode annunciator within the pilot’s primary field of view, near
the HSI or CDI.
Wiring Considerations
Wiring should be done in accordance with AC 43.13-1B, Chapter 11. Refer to the typical interconnect
diagram later in this manual for specifics. Use 22 to 24 AWG wire for all connections.
Fabricate wiring harness; refer to the interconnect diagrams and pin description. Test all the wiring for
continuity and for shorts. Insure aircraft power is on the correct pins of J1; refer to Table 6. Install slide
latch assembly onto J1 using instructions found later in this manual.
The mode annunciator/switch, P10280, comes pre-configured for 28V operation. For 14V operation,
perform the following steps:
1. Pull firmly on the edges of the lens to disengage the lamp assembly from the body. The lamp
assembly will hinge out and away from the body.
2. Remove and discard the four existing lamps, and replace with the four 14V lamps, P10301,
contained in the kit.
3. Push the lens firmly back into the body.
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