747飞机维护手册AMM CHAPTER 34 - NAVIGATION 第34章导航2(104)

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 EQUIPMENT IS OPERATED WITHOUT PROPER EQUIPMENT COOLING.
 (2)  The INS circuit breakers listed in Fig. 20 must be closed.
 (3)  Turn-on of the INS involves alignment of the system and its
 operation in the NAV mode. The INS is now prepared to accommodate
 normal system operational test procedures (Refer to INS -
Adjustment/Test).
 XA  (4)  Gimbal Slew Test (Delco CIV SYST only)
 XA  (a) Gimbal slew allows the simulation of airplane attitude
 XA  movements without the use of a tilt table or removal of the
 XA  INS navigation unit from the equipment rack. The resulting
 XA  outputs enable the checkout of INS attitude signal interfaces
 XA  and the calibration of interfacing systems.
 XA  (b) Gimbal slew is initiated by inserting a special P28 gimbal
 XA  slew test connector (A.C. P/N 7888466) into J28 on the front
 XA  of the INU. When the test connector is inserted, the WARN
 XA  light comes on and action code 00 is displayed if the data
 XA  selector switch is set to DSRTK/STS. The mode selector is set
 XA  to ALIGN and the navigation unit aligns in a normal manner
 XA  through Mode 7. When Mode 7 is completed (PI is 6), the
 XA  gimbal slew mode is automatically entered.
 XA
 XA  NOTE: In order to complete INS alignment, present position____
 XA  data must be loaded before the navigation unit can
 XA  complete Mode 7.
 XA

 EFFECTIVITY

 AIRPLANES WITH DELCO INS  CONFIG 1  01 A Page 70  Apr 25/8734-41-00
 XA  (c)  In normal INS operation, there is a small platform offset with
 XA  respect to gimbal angles (off level) due to noise from
 XA  electrical coupling in the gimbal area. This offset is
 XA  measured during manufacturing and a gimbal oriented bias (GOB)
 XA  correction factor is inserted into the INS computer memory.
 XA  In normal operation, the computer uses the GOB factor to torque
 XA  the gyros for leveling of the gimbals. In the gimbal slew
 XA  mode, the GOB factor is automatically stored and replaced with
 XA  a new correction factor for gimbal slew. When the HOLD light
 XA  is off, a large bias correction factor is applied causing the
 XA  computer to torque the gyros (at maximum torquing rate) in an
 XA  attempt to correct for this correction factor. When the HOLD
 XA  light is on, a zero bias correction factor is applied and the
 XA  computer stops torquing the gyros. Because the roll gimbal
 XA  axis becomes unstable near 90 degrees pitch, the computer
 XA  stops all torquing when 71 degrees in pitch or roll is reached.
 XA  (d)  Slewing is commanded with the HOLD light off. The pitch and
 XA  roll gimbals are slewed at approximately 2 degrees/min. The
 XA  selection of pitch or roll is determined by the position of
 XA  the AUTO/MAN switch. AUTO provides pitch slewing and MAN
 XA  provides roll slewing. If the REMOTE light is illuminated, the
 XA  torquing will be down in pitch or left in roll; if the REMOTE
 XA  light is out, the torquing will be up in pitch or right in
 XA  roll.
 XA  (e)  Azimuth torquing is normally accomplished by pitch slewing to
 XA  a finite angle followed by roll slewing. The azimuth slew rate
 XA  is approximately proportional to the sine of the gimbal pitch
 XA  angle. The maximum azimuth slew rate is about 1/2 degree per
 XA  minute.
 XA  (f)  Releveling the platform can be accomplished in two ways. One
 XA  way is to reverse the direction of slew until zero attitude is
 XA  achieved. The other way is to turn the mode selector to OFF.
 XA  Allow the gyros to run down for 2 minutes and then repeat the
 XA  "align" process in preparation for the next test.
 XA  (g)  Post gimbal slew procedures for returning to normal INS
 XA  operation are as follows:
 XA  1) Remove the gimbal slew test connector from J28 on the
 XA  connector access coverplate.
 XA  2) Verify data selector switch in DSRTK/STS position. INS
 XA  downmodes to course level (P.I. = 8) and action code 02 is
 XA  displayed.
　
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