K73905 T54340
OMEGA Navigation System Component Location  5C7 
34-59-01  Figure 1  Oct 20/90 
Page 2 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

554  OMEGA Transmitting Format 
Oct 20/83  Figure 2  34-59-01 
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

C.  The other two OMEGA frequencies are used for lane ambiguity resolution (Fig. 4). When the system receives less than 3 stations, the system operates in Dead Reckoning (DR) mode. The system accuracy is degraded and the estimated position could deviate from the 8 nm lane. To prevent the computed position from being in the wrong lane, when the third (or more) station is again received, the system will mix the 10.2 kHz and 11.33 kHz to provide 1.13 kHz which is used to develop a 72 nm lane. After position determination within this lane the system selects a  24 nm lane, formed by mixing 13.6 kHz and 10.2 kHz to provide a 3.4-kHz signal. After position determination within this lane, the system selects the correct 8 nm mile lane and normal navigation is resumed.
D.  The OMEGA system automatically determines the transmitting stations which are providing reliable VLF navigation signals. When the OMEGA system is turned on, the present position is manually inserted into the system and the system then computes the distance to each of the transmitting stations. The system then monitors the received signals to determine the stations that are being received and their respective signal strengths. It will then reject any stations that are more than 8000 nautical miles distant, have known diurnal or modal interference problems, or have a insufficient signal quality (index of less than 11). The distance constraint prevents wrap-around signals from being used for position determining. At least three stations must be selected by the ONS to enter the navigate mode; if less are available, it will remain in the Dead Reckoning mode. (After the first hour of operation, the ONS will navigate when only two stations are available even if they are transmitting on only one frequency each.)
E.  Low frequency propogation characteristics vary between seasons of the year, month, day and time of day. These factors are predictible and are programmed into the OMEGA system. The computer must be provided with GMT and date for proper application of these corrections into the system. Once inserted, the data will automatically update the correction factors.
3.  Receiver Processor Unit (Fig. 1)
A.  The Receiver Processor Unit (RPU) is a 3/4 ATR long unit which is rack mounted in the main electronic equipment rack. Electrical connections to the unit are provided through a rear connector which mates with an equipment rack connector and a connector on the front panel for the antenna coupler. The unit is secured in the rack by swivel nuts located on the equipment rack.
B.  The RPU contains solid-state micro-electronic circuit cards. The cards are designed to fold out for "in shop" maintenance. The unit contains the following subassemblies:
(1)  
Receiver Card - contains antenna switching circuits, three receiver channels, a 6.12 MHz oscillator and a frequency divider.

(2)  
Digital Card - contains serial to parallel and parallel to serial registers, associated I/O buffers, and RPU to CDU interface circuits.

(3)  
Analog Card - contains autopilot steering interface.

(4)  
Microprocessor Card - contains central processing unit, program control circuits, and input/output buffers.

34-59-01 May 15/81 Page 4
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.

K73909
554  OMEGA Lane Ambiguity Resolution 
Feb 15/79  Figure 4  34-59-01 
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

(5)  
Memory Card - contains random access memory (RAM), and ultraviolet erasable read only memory (UVE-ROM). The use of UVE-ROM allows new programs to be written into the system as future developments take place.

(6)  
Power Supply -Provides the necessary bias voltage throughout the RPU.

C.  The RPU front panel contains a BITE indicator which is set (black and white pattern) when the ONS has failed.
4.  Control Display Unit (Fig. 5)
A.  The Control Display Unit (CDU) is a panel mounted unit which is installed on the forward aisle stand. The unit contains all operating controls for the OMEGA system. The unit permits insertion of positional data and time/date data and provides readouts of inserted data and computed navigation information. The various controls and switches are described in Fig. 5. The front panel assembly consists of two separate plastic panels, each of which is secured to the chassis by two captive screws. The upper panel covers the fifteen readout lamps and six bipin lamps which make up the numerical and from-to displays; the lower panel includes integrally-molded edgelighting lamps and encloses all operating controls and annunciators, including the mode and display switches.
　
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