Mid-Continent Instruments MD41 Series Technical Document

INSTALLATION MANUAL AND
OPERATING INSTRUCTIONS
MD41-( ) Series GPS ANNUNCIATION CONTROL UNIT
FOR ALLIED SIGNAL KLN 90B
MD41-328 28vdc Horizontal Mount
MD41-338 28vdc Vertical Mount (shown on page 13)
MD41-324 14vdc Horizontal Mount
MD41-334 14vdc Vertical Mount (shown on page 13)
MID-CONTINENT INST. CO., INC MANUAL NUMBER 7016074

REV. 4 Jan. 09, 1997 2
MANUAL REVISION AND HISTORY
MANUAL: MD41-324, -334, -328, -338
REVISION: OCT. 25, 1995 Rev. 1
MANUAL NUMBER: 7016074
This revision level of this manual consist of the following changes:
Add MD41-334, -338 vertical mount versions.
REVISION: NOV. 06, 1995 Rev. 2
Add MD41-328(5V)/338(5V) These part numbers have 5 volt push-button lighting.
REVISION: JAN. 24, 1996 Rev. 3
Added GPS annunciation interlock.
REVISION: JAN. 09, 1997 Rev. 4
Revised DO160C section 4.0 environmental test data. Test D1 is now F2

REV. 4 Jan. 09, 1997 3
TABLE OF CONTENTS
SECTION 1 GENERAL DESCRIPTION
1.1 INTRODUCTION
1.2 SPECIFICATIONS, TECHNICAL
1.2.1 PHYSICAL CHARACTERISTICS
1.2.2 ENVIRONMENTAL CHARACTERISTICS
1.2.3 SPECIFICATIONS, ELECTRICAL
1.2.4 FRONT PANEL CONTROLS AND ANNUNCIATIONS
1.2.4.1 CONTROLS
1.2.4.2 ANNUNCIATIONS
1.2.5 INTERFACE
1.2.6 EQUIPMENT LIMITATIONS
1.2.7 MAJOR COMPONENTS
SECTION 2 INSTALLATION CONSIDERATIONS
2.1 COOLING
2.2 EQUIPMENT LOCATION
2.3 ADDITIONAL ANNUNCIATIONS
2.4 ADDITIONAL RELAYS
2.5 ROUTING OF CABLES
SECTION 3 INSTALLATION PROCEDURE
3.1 GENERAL INFORMATION
3.2 UNPACKING AND INSPECTING
3.3 MOUNTING THE MD41-( )
3.4 INSTALLATION LIMITATIONS
SECTION 4 POST INSTALLATION CHECKOUT
4.1 PRE-INSTALLATION TEST
4.2 OPERATING INSTRUCTIONS
FIGURE N0. LIST OF ILLUSTRATIONS
3.1 SCHEMATIC PINOUT, 25 PIN DSUB
3.2 SCHEMATIC PINOUT, 50 PIN DSUB
3.3 CUTOUT DIMENSION FOR PANEL MOUNTING
3.4 OUTLINE DRAWING
3.5 WIRING DIAGRAM, MD41-324/334 (14V)
3.6 WIRING DIAGRAM, MD41-328/338/328(5V)/338(5V) (28V)
APPENDIX
ENVIRONMENTAL QUALIFICATION FORM

REV. 4 Jan. 09, 1997 4
SECTION 1 GENERAL DESCRIPTION
1.1 INTRODUCTION
The MD41-( ) is a self -contained GPS Annunciation and Control unit. It combines all the
necessary functions required for switching HSI/CDI data inputs between a conventional
NAV (VOR) receiver and the Allied Signal KLN 90B approach-certified GPS receiver. In
addition, the MD41-( ) contains several GPS status annunciations used to indicate modes
selected by the front panel switches and various inputs from the GPS receiver.
A special ILS override feature has been incorporated to cause the MD41-( ) to
automatically switch to the NAV mode when the NAV (VOR) receiver is tuned to an ILS
frequency. Other features include dual, 16,000 hour lamps used for all annunciations,
internally lighted selection switches, automatic photocell dimming, and built-in
annunciation self test. A external annunciation dimming adjustment is provided for
balancing low level light conditions.
A 19 pole relay assembly is included within the MD41-( ) to simplify installation of the
switching between NAV (VOR), GPS and the associated HSI/CDI. All relays have gold
plated contacts and are nitrogen filled for high reliability.
Two versions are available that will allow the lighted selection buttons to operate from a
5 volt instrument dimming bus. These part numbers are as follows: MD41-328(5V) and
MD41-338(5V).
A MD156 adapter plate is available for front mount installations. Also a MD155 punch is
available for instrument hole cutout.
1.2 SPECIFICATIONS, TECHNICAL
1.2.1 PHYSICAL CHARACTERISTICS
Mounting: Panel
Width: 3.50 Inches
Height: 1.350 Inches
Depth: 4.625 Inches
Weight: 0.75 lbs.

REV. 4 Jan. 09, 1997 5
1.2.2 ENVIRONMENTAL CHARACTERISTICS
TSO Compliance: TSO C129
Applicable Documents: RTCA DO-160C, DO-208
Operating Temperature Range: -55°C to +70°C
Humidity: 95% Non-Condensing
Altitude Range: 0 to 55,000 ft.
Vibration: Cat. M and N
Operational Shock: Rigid Mounting, 6 G Operational
15 G Crash Safety.
1.2.3 SPECIFICATIONS, ELECTRICAL
Design: All Solid State
MD41-324/334 (14VDC) 0.65 Amps
MD41-328/338 (28VDC) 0.40 Amps
MD41-328(5V)/338(5V) (28VDC) 0.40 Amps
Relay contact current rating 2 Amps DC
Available relay poles (SPDT) 19
1.2.4 FRONT PANEL CONTROLS AND ANNUNCIATIONS
1.2.4.1 CONTROLS
NAV/GPS Alternate action switch, when pressed, will select NAV
(VOR) or GPS presentation on HSI/CDI.
GPS/APR Momentary switch, when pressed, will arm GPS Approach
Mode.
OBS/LEG Alternate action switch, when pressed, will select between
OBS and LEG modes.
LAMP TEST Momentary switch for testing annunciation lamps. Note:
Screwdriver adjustable control located on right side of case
sets annunciator low dimming level.
1.2.4.2 ANNUNCIATIONS
NAV NAV (VOR) information presented on the HSI or CDI.
GPS GPS information presented on the HSI or CDI.
ARM GPS is armed for automatic transition to approach mode.
ACTV GPS is actively engaged in the approach mode.

REV. 4 Jan. 09, 1997 6
OBS This will activate the course selector and also disable
the automatic GPS waypoint sequencing to the next leg.
LEG This will disable the course selector input to the GPS
and will enable automatic GPS waypoint sequencing to the
next leg of the pre-planned route.
MSG GPS message alert, from the GPS receiver.
WPT GPS waypoint alert, from the GPS receiver .
1.2.5 INTERFACE
APPR ARM Select
J1 Pin 24
Provides a momentary logic low to GPS
receiver when approach arm is selected.
APPR ARM
J1 Pin 16
Receives a logic low from the GPS receiver to
annunciate ARM.
OBS/LEG Select
J1 Pin 9
Provides a logic low to the GPS receiver
when OBS is selected.
GPS APR ACTV
J1 Pin 8
Receives a logic low from the GPS receiver
when a transition is made from arm to active.
ILS Override
JI Pin 14
Receives a logic low from the NAV (VOR)
receiver when tuned to an ILS frequency.
This will force the MD41-( ) into NAV mode
regardless of the NAV/GPS selection. This
connection is optional.
AP ILS Energize
J1 Pin 3
Provides an ILS ground to the autopilot
computer. This AP ILS energize will follow
the MD41-( ) NAV/GPS selection. When in
GPS mode, a ground will appear on J1 pin 3
when ACTV is annunciated.
NAV Receiver ILS
J1 Pin 4
Receives an ILS energize input from the
NAV(VOR) receiver. This will provide an
ILS energize output to J1 pin 3 when NAV is
selected on the MD41-( ).
MSG and WPT
annunciation
A logic low will cause the appropriate
annunciation to illuminate. GPS receiver must
be able to accept 100ma.
GPS DISPLAYED
J1 pin 17
Provides a ground to the GPS receiver when
NAV is selected on the MD41-( ).

REV. 4 Jan. 09, 1997 7
1.2.6 EQUIPMENT LIMITATIONS
The MD41-( ) series control units contain specific dash numbers to be used with various GPS
receivers. The installer must match the correct controller part number with the GPS receiver
being installed.
The conditions and tests required for TSO approval of this article are minimum
performance standards. It is the responsibility of those desiring to install this article either
on or within a specific type or class of aircraft to determine that the aircraft installation
conditions are within the TSO standards. The article may be installed only if further
evaluation by the applicant documents an acceptable installation and is approved by the
Administrator.
The MD41-324/328/334/338/328(5V)/338(5V) is TSO’D and certified for use with the
Bendix/King KLN 90B system. Any attempts to install the
MD41-324/328/334/338/328(5V)/338(5V) in an installation other than the Bendix/King KLN
90B is prohibited. This will void the TSO.
NOTE: Anytime the MD41-( ) is disconnected or removed from the aircraft, the HSI/CDI
will be inoperative in both NAV (VOR) and GPS.
1.2.7 MAJOR COMPONENTS
The system is comprised of one major component, the MD41-( ) GPS Annunciation Control
Unit.

REV. 4 Jan. 09, 1997 8
SECTION 2 INSTALLATION CONSIDERATIONS
2.1 COOLING
No direct cooling is required. As with any electronic equipment, overall reliability may be
increased if the MD41-( ) is not located near any high heat source or crowded next to other
equipment. Means of providing a gentle air flow will be a plus.
2.2 EQUIPMENT LOCATION
The MD41-( ) must be mounted as close to the pilot’s field of view as possible. The preferable
location is near the HSI/CDI that will be displaying the GPS information. The unit depth, with
connector attached, must also be taken into consideration. A MD156 adapter plate is available
for front mounting.
2.3 ADDITIONAL ANNUNCIATIONS
Depending upon the installation and approving agency, you may be required to provide
additional NAV Source Select external annunciators near the HSI/CDI. Spare relay contacts
on the MD41-( ) J1 or J2 connector may be used for this purpose.
2.4 ADDITIONAL RELAYS
The MD41-( ) contains 19 relay poles. Some installations may require more than 19 poles due
to data lines, superflags etc. If this should occur, you may use one spare relay pole to switch
additional relays. In cases where it may be more desirable to have all the relay switching done
at a remote location, (i.e.: remote mounted equipment) one relay pole on the MD41-( ) may be
used for switching this bank of relays. Please note that the maximum relay contact rating for
the MD41-( ) is 2 amps DC.
2.5 ROUTING OF CABLES
Care must be taken not to bundle the MD41-( ) logic and low level signal lines with any high
energy sources. Examples of these sources include 400 HZ AC, Comm, DME, HF and
transponder transmitter coax. Always use shielded wire when shown on the installation print.
Avoid sharp bends in cabling and routing near aircraft control cables.

REV. 4 Jan. 09, 1997 9
SECTION 3 INSTALLATION PROCEDURES
3.1 GENERAL INFORMATION
This section contains interconnect diagrams, mounting dimensions and other information
pertaining to the installation of the MD41-( ). After installation of cabling and before
installation of the equipment, ensure that power is applied only to the pins specified in the
interconnect diagram.
3.2 UNPACKING AND INSPECTING EQUIPMENT
When unpacking equipment, make a visual inspection for evidence of damage incurred during
shipment. The following parts should be included:
1. MD41-324 (14V) or MD41-328 (28V) Horiz. Mount
MD41-334 (14V) or MD41-338 (28V) Vert. Mount
MD41-328(5V) (28volt) 5 volt button lighting Horiz. Mount
MD41-338(5V) (28volt) 5 volt button lighting Vert. Mount
2. J1 Connector Kit (25 pin). MCI PN 7014517
3. J2 Connector Kit (50 pin). MCI PN 7014509
4. Installation Manual. MCI PN 7016074
5. 4-40 x 1.0” Mounting Screws, 4ea. MCI PN 7016165
3.3 MOUNTING THE MD41-( )
Plan a location in the aircraft for the MD41-( ) to be mounted as close to the pilot’s field of
view as possible. The preferable location is near the HSI/CDI that will be displaying the GPS
information. Avoid mounting close to heater vents or other high heat sources. Allow a
clearance of at least 3 inches from back of unit for plug removal.
The indicator is secured in place behind the panel since it is designed for rear mount only.
Make a panel cutout as shown in Figure 3-3. Secure the indicator in place with four 4-40 x 3/8
to 1.0” flat head phillips screws. A MD156 adapter plate is available for front mount
installations. Also a MD155 punch is available for hole cutout.
3.4 INSTALLATION LIMITATIONS
Wire the aircraft harness according to figure 3-5 or 3-6. Use at least 24 AWG wire for all
connections. You MUST use shielded wire where shown. Avoid sharp bends and routing
cable near high energy sources. Care must be taken to tie the harness away from aircraft
controls and cables. Normal installation techniques should be applied.

REV. 4 Jan. 09, 1997 10
REAR VIEW OF J1 (bottom) CONNECTOR
J1
PIN NO.
1 ---------------- NO7 RELAY
2 ---------------- NC7 RELAY
3 ---------------- ILS ENERGIZE TO AUTOPILOT
4 ---------------- ILS FROM NAV (VOR) REC (for autopilot)
5 ---------------- C8 RELAY
6 ---------------- NC8 RELAY
7 ---------------- NO8 RELAY
8 ---------------- GPS APR ACTV ANNUNCIATION
9 ---------------- OBS HOLD (logic low to GPS)
10 -------------- MSG ANNUNCIATION
11 -------------- WPT ANNUNCIATION
12 -------------- 14 VDC UNIT PWR -324/334 ONLY
13 -------------- 28 VDC UNIT PWR -328/338/328(5V)/338(5V) ONLY
14 -------------- ILS FROM NAV (VOR) REC. (for ILS override)(optional)
15 -------------- C7 RELAY
16 -------------- APR ARM ANNUNCIATION
17 -------------- GPS DISPLAYED (gnd to GPS)
18 -------------- C5 RELAY
19 -------------- NC5 RELAY
20 -------------- DIM LOW (to lighting bus)(for push-button lighting)
21 -------------- DIM HIGH (to lighting bus)(for push-button lighting)
22 -------------- NO5 RELAY
23 -------------- TO NAV CIRCUIT BREAKER (for fault monitoring)
24 -------------- GPS ARM (momentary logic low to GPS)
25 -------------- POWER GROUND
FIGURE 3-1 SCHEMATIC PINOUT, 25 PIN DSUB