747飞机维护手册AMM CHAPTER 34 - NAVIGATION 第34章导航2(89)

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 (c)  The fifth digit indicates the align mode number and must indicate 5 before the NAV mode can be entered. On airplanes with Delco CIV-31N or CIVA-32C INS, during the NAV mode, the align mode number is automatically set at 5. On airplanes with Delco CIVA-25 INS, during the NAV mode, the align mode number has been made representative of navigation performance. During NAV, this digit, sometimes referred to as the Accuracy Index (AI) number, will range from 1 to 9, with 1 being the best accuracy. The INU computer forces this number to 1 when the NAV mode is entered. The number progresses toward 9 as time in NAV increases. As DME updating is being performed, the AI number decreases toward 1. The rate of increase or decrease of this number is dependent on time in NAV, DME station geometry, length of time of DME acquisition, and whether dual or single DME updating is being performed. The AI number is limited to 9. The AI number increases at a rate of 3T where T is time in hours if no DME update is being performed. On airplanes with Delco CIVA-28A-2 INS, during the NAV mode, the align mode number has been made representative of navigation performance. During NAV, this digit, sometimes referred to as the Accuracy Index (AI) number, will range from 1 to 9, with 1 being the best accuracy. The INU computer forces this number to 1 when the NAV mode is entered. The number progresses toward 9 as time in NAV increases. As DME updating is being performed, the AI number decreases toward 1. The rate of increase or decrease of this number is dependent on time in NAV, DME station geometry, length of time of DME acquisition, and whether dual or single DME updating is being performed. The AI number is limited to 9. The AI number increases from 1 toward 9 at a slower rate during triple INS mixing than it does during unaided operation. The following equations are used to calculate the AI number during triple INS mixing, and unaided operation:
 AI = 1 + 2T - DPL (triple INS mixing) AI = 1 + 3T - DPL (no triple INS mixing)
 where,  T = Nav time in hours DPL = Decrementing value based on DME updating

 (d)  On airplanes with Delco CIV-31N, CIVA-20, CIVA-25, -28A and 32C INS, the sixth digit is automatically set to a desired performance index of 5 during ALIGN and cannot be changed until the INS enters the NAV mode. In NAV this sixth digit indicates the selected operating mode and is a number ranging from 0 to 5.
 EFFECTIVITY

 AIRPLANES WITH DELCO INS  CONFIG 1  03 A Page 25  Apr 25/8934-41-00
 To change the operating mode during NAV, press numbered key and then press the INSERT key. The inserted number is indicative of the selected operating mode. For example: Operating mode number 4 indicates that the INS is operating in the aided inertial mode using DME data or triple INS mixing. Operating mode number 0, 2, 3 or 5 indicate that the INS is operating independently but with any previous position update being retained. Operating mode number 1 can be keyed in and inserted to perform a position update eradication. The display then returns to normal showing an operating mode of 5. Numbers greater than 5, for example 6, 7, 8 or 9 can be keyed into the CDU display, but when the INSERT key is pressed, the INS program will interpret and process the number as if it were a 5. The operating mode number would therefore be displayed as a 5 after the INSERT key had been pressed. On airplanes with Delco CIVA-28A-2 INS, the sixth digit is automatically set to a desired performance index of 5 during ALIGN and cannot be changed until the INS enters the NAV mode. In NAV this sixth digit indicates the operating mode, with a number ranging from 0 to 5. When the INS enters the NAV mode the sixth digit automatically changes to 4. To change to operating mode numbers 0, 1, 2, 3, and 5 during NAV, press the respective numbered key and then press the INSERT key. Operating mode number 4 indicates that the INS is operating in (or available to operate in) the aided inertial mode using DME data or triple INS mixing. Operating mode numbers 0, 2, 3 or 5 indicate that the INS is operating independently but with any previous position update being retained. Operating mode number 1 can be keyed in and inserted to perform a position update eradication. The display then returns to normal showing an operating mode of 5. Numbers greater than 5, for example 6, 7, 8 or 9 can be keyed into the CDU display, but when the INSERT key is pressed, the INS program will interpret and process the number as if it were a 5. The operating mode number would therefore be displayed as a 5 after the INSERT key had been pressed. During NAV, if operating in mode 5 and a DME station is then designated on the CDU, the sixth digit will automatically change to operating mode 4.

 G.  The AUTO-MAN switch is normally left at the AUTO position. This allows automatic navigation leg switching during flight. If the MAN position is used, the INS will not switch to the next navigation leg, but will continue to furnish and display steering signals to maintain the desired track for the completed navigation leg.
　
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