XA see *[1] 34-41-00 page 1. 3) Triple INS Mixing (Airplanes without PMS). In a three INS installation, triple INS mixing can be commanded at the INS CDU (operating mode number 4). Triple INS mixing will update the displayed INS present position to approximately the mid inertial latitude and mid inertial longitude of the three systems.
NOTE:____1. The operating mode number appears in the 6th digit of the CDU right-hand display, when the data selector is set to DSRTK/STS.
2. On airplanes with CIVA-28A-2 INS, when the INS enters the NAV mode the sixth digit automatically changes to operating mode 4.
4) Triple INS Mixing (Airplanes with PMS). In a three INS installation, triple INS mixing can be commanded at the PMS CDU, in the PMS waypoint control mode; or at the INS CDU, in the INS waypoint control mode (operating mode number 4). Triple INS mixing will update the displayed INS present position to approximately the mid inertial latitude and mid inertial longitude of the three systems.
5) DME Update of INS Present Position (Airplanes without PMS). For an INS connected to the DME distance data; if one or more DME stations are within range, DME updating can be commanded at the INS CDU (operating mode number 4). When DME updating is commanded, the displayed present position of the INS is automatically updated by the DME.
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6) PMS Update of INS Present Position (Airplanes with PMS). If one or more DME stations are within range, DME updating can be commanded at the PMS CDU (PMS is connected to DME distance data). When DME updating is commanded, and the INS is in the PMS waypoint control mode, the displayed present position of the INS is automatically updated by the PMS.
(g) Attitude (ATT)
1) In the ATT mode, the computer and CDU are shut down, and no displays are available. It is entered as required if navigation and/or steering data signals become unreliable. Attitude signals and platform heading outputs continue to be available. The NAV mode cannot be re-entered from the ATT mode unless the system is realigned. Alignment can take place only on the ground.
B. Functional Description, Self-Test Procedures
(1)
The TEST switch can be pressed at any time during INS operation to test the indicating lamps and displays on the MSU and CDU and the DCU input/output. Proper operation is indicated by illumination of all lamps and displays while the switch is pressed. Each digit in the FROM-TO display and data displays is lighted to indicate an 8. The directional letters (N S E W) are also lighted in the data displays.
(2)
Illumination of the WARN lamp can be caused by either an intermittent or a continuous out of tolerance condition. Pressing the TEST switch while the WARN lamp is lighted will reset the DCU warning circuits and the WARN lamp will go out if the condition is not persistent. If the WARN lamp remains illuminated, the malfunction persists and may impair system performance.
(3)
Pressing and releasing the TEST switch while the data selector is at DSRTK/STS will display any malfunction codes in the second and third digits of the right hand data display. When the WARN lamp is illuminated, additional malfunction codes can be displayed by additional TEST switch operation. If more than one failure is detected by the DCU, each actuation of the TEST switch will display another malfunction code until all current malfunction codes have been displayed. Actuation of the TEST switch after all current malfunction codes have been displayed will cause the two digits to go blank.
(4)
The DCU stores a record of all failures, whether intermittent or persistent from the start of fine leveling in the alignment mode until the next time the DCU enters the fine leveling mode. The DCU memory can be interrogated to determine all failures that have occurred during this period.
C. Controls
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(1) Prior to operating the inertial navigation system, electrical power
must be provided to the aircraft (Ref 24-22-00, Electrical Power,
Manual Control), the central air data computer system must be
operating (Ref 34-12-00, Central Air Data Computer System -
Adjustment/Test), both VOR-ILS/INS switches (located on pilot's
lightshield panels) should be in the INS position, and the
equipment cooling system should be operating (Ref 21-58-00
Equipment Cooling System).
CAUTION: DAMAGE TO ELECTRONIC EQUIPMENT CAN RESULT IF THE_______
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