6. Antenna/Coupler Unit (ACU) (GJ ALL EXCEPT B-2501 thru B-2505)
A. The H-FIELD antenna/coupler units are located on the tips of the left and right horizontal stabilizers. The units are secured to a adaptor plates by 6 screws. Each ACU contains the field sensing elements and the first two stages of signal amplification and frequency selectivity. Omnidirectional reception is provided by a pair of orthogonal loop antennas. The loop antennas consist of ferrite rods which sense the H-field (magnetic field) component of the OMEGA/VLF signals. The antennas are relatively temperature-insensitive and immune to the noise generated by electrostatic discharges from the airframe.
B. The ACU also contains BITE circuits for monitoring of the ACU by the RPU.
7. Horizontal Situation Indicator
A. Both the Captain's and First Officer's Horizontal Situation Indicators receive groundspeed and groundspeed valid from the Omega RPU. The data is displayed on the digital GND SPEED display at the top of the HSI. When the groundspeed valid signal becomes invalid, the digital GND SPEED display shows dashes. The HSI valid is displayed on the NAV valid annunciation.
B. Drift angle, drift angle + track angle error, crosstrack deviation, TO/FROM, track change ALERT, and HSI valid are switched to the HSI's through the RAD/OMEGA relays. When the NAV RAD/OMEGA switch on the pilot's lightshield is set to OMEGA, the HSIs display the OMEGA drift angle on the drift angle marker, OMEGA drift angle + track angle error on the course arrow, crosstrack deviation on the course deviation bar TO/FROM on the to-from pointer, track change ALERT on the ALERT annunciator, and NAV on the piewheel. The glide slope pointer will stow when OMEGA is selected on NAV RAD/OMEGA switch.
5C8
Jun 20/85 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 34-59-01 Page 6A
K73912
554 Control Display Unit
Feb 15/79 Figure 5 34-59-01
Page 7
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
7. Operation
A. The system controls are all located on each CDU and are described below.
(1)
DIM control - When rotated upward, reduces intensity of left (2), right (3), and from/to (17) displays. When rotated downward, increases intensity of displays.
(2)
Left display - Displays data selected by display switch (13).
(3)
Right display - Displays data selected by display switch (13).
(4)
ALR (alert) annunciator (amber) - Comes on when aircraft is two minutes from next waypoint. If mode switch is set to A, goes out when track leg change occurs; if mode switch is set to M, flashes when aircraft is one-half minute from next waypoint and continues to flash until manual track leg change is made.
(5)
DR (dead reckoning) annunciator (amber) - Comes on when ENT pushbutton is pressed to enter final present position coordinate (usually longitude); goes out when ONS enters navigate mode (status 01). Also comes on when ONS loses Omega navigation capability, including periods when manual relaning is in process. DR annunciator will not come on if power transfer occurs while acft is on ground of if ONS enters navigate mode within 2 minutes after power transfer.
(6)
SYN (synchronization) annunciator (amber) - Comes on when ONS begins synchronizing with received signals either during alignment or after a power interrupt; goes out when synchronization occurs. Flashes if synchronization does not occur within 3 minutes of ONS turn-on. SYN annunciator will not come on if acft is on ground or synchronization is achieved within 1 minute.
(7)
AMB (ambiguity) annunciator (amber) - Comes on when an Omega position ambiguity is detected and goes out when ambiguity ceases.
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