(10)
When the display selector switch is set to WPT, the WPT (waypoint) selector switch is used to select waypoints (1 thru 9) for latitude and longitude insertion, or to select waypoints (0 thru 9) for presentation of waypoint coordinates on left and right numerical displays.
(11)
The TK CHG (Track Change) pushbutton enables entry of FROM/TO track numbers.
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(12)
The FROM/TO display displays the "from" and the "to" waypoint numbers of the track being navigated. During automatic mode, the FROM/TO display will automatically advance to the next waypoint 30 seconds before reaching that waypoint. In manual mode, the operator must initiate a track change to update the FROM/TO readout for the next waypoint being tracked.
(13)
The AUTO/MAN/RMT switch provides the following functions:
(a)
In the AUTO position, the INS performs automatic sequential track leg changes and also permits manual track leg changes.
(b)
In the MAN position, the INS allows manual track leg changes only.
(c)
The RMT position enables semiautomatic autofill operation, remote ranging and display of inserted crosstrack offset. Flight legs are switched automatically when in RMT.
(d)
In the STBY and ALIGN modes (with the CDU data selector switch in TEST position), the position of the AUTO/MAN/RMT switch affects various values of INS test outputs to the HSI and other interfacing systems.
(14)
The INS is placed in an attitude slew mode when a special attitude slew test connector is installed in J4 on the front of the Navigation Unit and the mode selector is set to ALIGN. With the data selector switch set to POS, pitch slew angles up to a maximum of 15 degrees can be inserted on the data keyboard. The N pushbutton is selected for a pitchdown attitude and the S pushbutton for a pitch up attitude. Roll slew angles (there is no limit on roll) are also inserted on the data keyboard. The E pushbutton is pressed for a left roll angle and the W pushbutton for a right roll angle.
5. Inertial Navigation Unit
________________________
A. The inertial navigation units (INU), one for each INS, are installed in individual mounting trays on main equipment center shelf E2-6 (Fig. 1). Each INU weighs approximately 60 pounds and consists of a computer and digital subsystem, platform and platform electronics, synchro repeaters and an integral power supply. A temperature control and sensing circuit maintains required environmental conditions. Mounted on the front panel of each INU are an elapsed time indicator and a magnetically latched fault indicator. Any failure that causes the WARN annunciator on the CDU to come on will also trip the INU fault indicator from the normal black indication to a yellow indication. Two conditions (not failures) will cause the WARN annunciator to come on but will not trip the fault indicator. These are low battery voltage (indicated by BATT annunciators illuminating) and recycling from ATT mode to any other mode escept OFF.
B. If the primary 115-volt ac power source should fail, fall below, or go above preset levels, a power monitor will automatically switch the system to the backup battery. An indicator on the front of the INU and the WARN indicator on the CDU both come on during an INU malfunction.
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C. The INU inertial platform is the source of north-south and east-west acceleration signals for the INS. The INU digital computer uses the acceleration signals to compute the actual track, ground speed, and position coordinates of the airplane. The digital computer stores the desired route coordinates, computes steering commands to automatically guide the airplane along the desired flight path, and computes airplane crosstrack deviation for display by the course deviation bar in the horizontal situation indicator.
6. Battery Unit
____________
A. The battery unit (BU) provides auxiliary power to initiate INS turn on and to supply essential power to maintain INS operation when the 115-volt input power is interrupted or drops below the required voltage. The battery unit contains 19 nickel-cadmium cells which are connected in series to furnish 24 volts dc. A 20-ampere circuit breaker on the front of the battery unit protects it from excessive current flow if a short circuit develops. Power from the battery unit is used momentarily to close a relay which turns on the INS. Battery unit power is connected to the INS power circuits so that it will sustain INS operation in any operating mode if primary power fails. The battery unit will sustain INS operation for periods of up to 15 minutes.
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本文链接地址：747飞机维护手册AMM CHAPTER 34 - NAVIGATION 第34章导航2(113)
