13. INS Updating Annunciators (On airplanes with PMS)
_________________________

 A.  When the INS present position is being updated by the PMS, the corresponding (INS-1 or INS-2) annunciators on both the captain's and first officer's main instrument panels, will change from black to green. These annunciators alert the captain and first officer that the displayed INS present position is being updated by the PMS, and that a possible change in airplane position may be accomplished by the autopilot.
 14. INS Signal Interface
____________________
 A.  External Signal Inputs (Fig. 2)
 (1)  True airspeed from the cetnral air data computers (CADC) and digital data from the PMS (when installed) are the only external signal inputs used by the INS.
 B.  Output Signal Interface
 (1)  The overall INS interface is shown in Fig. 2. In addition to the displays, the INS provides the following:

 (a)  
Stabilization signals to the weather radar system, keeping it level during normal maneuvers

 (b)  
Navigation data and attitude to the autopilot/flight director system

 (c)  
On airplanes with INS program 72-50-04, rate and acceleration signals (autoland parameters) to the autopilot/flight direction system.

 (d)  
Pitch attitude reference to the auto throttle system

 (e)  
Roll attitude signals to the yaw damper system for turn coordination

 (f)  
Platform heading to the compass couplers of the magnetic heading reference system

 (g)  
Pitch attitude reference to the overrotation warning system

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 (h)  
Roll and pitch attitude signals to the flight data acquisition unit

 (i)  
On airplanes with PMS, flag output signals from the INS to the INS updating annunciators.

 C.  Intersystem Interface
 (1)  Interunit Interface (Fig. 2)
 (a)  
The three INS systems are interconnected to allow any one system to accept data from the other two. Waypoint data loading is accomplished through data interchange on digital data lines between systems.

 (b)  
Each navigation unit has three digital data input channels, each channel consisting of clock, data, and sync signals.

 D.  On airplanes with PMS, Performance Management System (PMS) Interface (Fig. 2).
 (1)  
The INS is capable of operating as a system dependent on the PMS (PMS waypoint control mode), or as a completely independent system (INS waypoint control mode).

 (2)  
When operating in the PMS waypoint control mode, the INS responds to digital transmissions from the PMS which provide:

 (a)  
Mode control (PMS waypoint control or INS waypoint control).

 (b)  
HSI warn and digital data test control.

 (c)  
Position updates based upon weighted INS and radio data.

 (d)  
Active track leg waypoint positions.

 (e)  
Alert annunciator control.

 (3)  
With the INS in the PMS waypoint control mode, the INS MSU is used to activate the INS. The PMS receives present position (loaded at the INS CDU) and monitors INS alignment progress. In this mode, the INS CDU functions only as a passive monitor. When NAV mode is achieved, the coordinates of the current waypoint pair and the updated present position are continuously transmitted from the PMS to the INS. The INS in turn provides present position, heading, velocity, and status to the PMS. The INS provides lateral navigation signals to the autopilot - flight director system when in PMS waypoint control.

 (4)  
When the airplane approaches the TO waypoint, the PMS provides (in the PMS waypoint control mode) a signal for the INS CDU ALERT annunciator to turn on and commands a track leg change as computed by the PMS. A new waypoint pair is then transmitted by the PMS to command the INU to compute the new desired track and steer the airplane to capture the new leg. In the new waypoint pair, the old TO waypoint becomes the FROM waypoint and the next waypoint is the TO waypoint.

 NOTE: In the PMS waypoint control mode the INS CDU FROM/TO display
____ is blank (with the AUTO/MAN/RMT switch in MAN).
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TRUE HDG TRUE HDG VALID NAV VALID ALERT TKE+DA TO/FROM DA TKE XTK DIGITAL DATA DIGITAL DATA VALID LEG SWITCH PLATFORM HDG
PLATFORM HDG VALID
INS NAV UNIT NO. 1
　
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