34-31-02
 ú ú 06 Page 15 ú Mar 15/92

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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A 737-300/400/500MAINTENANCE MANUAL
Taking one system as an example: rotation of the remote course knob selects the desired VOR/LOC course and positions the EHSI course arrow. At the time the course arrow is positioned, the selected course is also displayed on the DFCS mode select panel course counter. The course select resolver is also positioned in accordance with the selected course. Two signals from the resolver are fed to the VOR portion of the navigation unit for generation of the VOR deviation and to/from outputs. The to/from output is not used. The VOR deviation output is fed to the EFIS to drive the course deviation display in the EHSI.Position of the course deviation bar with respect to the miniature airplane, shows real airplane position with respect to the selected course. The course deviation scale dots are referenced points for showing airplane lateral displacement from the selected course. TO-FROM annunciation appears adjacent to the course deviation scale near the center of the EHSI. As the airplane passes over the selected VOR ground station, the to/from annunciation reverses 180 degrees. The VOR to/from display is initiated in the FMCS (AMM 34-62-01), and generated in the EFIS (AMM 34-22-00).VOR ground station bearing is displayed by the RDDMI bearing pointers. The narrow pointer displays VOR-1 bearing while VOR-2 bearing is displayed by the wide pointer. The RDDMI pointer flags are biased out of view when the VOR bearing is valid. Tuning to an ILS frequency parks the associated pointer at the 3 o'clock position. The VOR bearing displays are inhibited (frozen) with the pointer flags in view when the FMC and DME systems are operating in the autotune mode with DME agility enabled.Selecting an ILS frequency enables the EADI and EHSI localizer and glide slope displays for making an instrument landing approach.Localizer deviation is displayed by the EADI localizer pointer and the EHSI course deviation bar which move laterally across a scale to show airplane deviation from the localizer beam.Glide slope information is displayed by the glide slope pointer in the EADI and EHSI. The pointers remain horizontal and move vertically across the scale to show airplane deviation about the glide path.
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 34-31-02

 ú ú 02 Page 16 ú Jul 15/92
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
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When the system is tuned to a VOR frequency, the EADI and EHSI glide slope pointers and scales and the EADI localizer pointer and runway symbol are out of view.

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The VOR/LOC super flag signals control the respective EADI LOC, EHSI VOR OR LOC, and RDDMI pointer warning flags.

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 A system self-test feature is controlled by the test switches on the VHF NAV control panel.

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 For VOR test, tune VHF NAV to a VOR frequency, select a course of 000 degrees, select ATT mode and enter a heading of 000 degrees in both IRS systems, select FULL VOR/ILS mode for both EFIS systems and position VHF NAV transfer switch to NORMAL: When the VOR self-test is held actuated, test displays on the associated instruments are as follows:

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EHSI course deviation bar disappears for 3 seconds, reappears centered for 23 |5 seconds, then disappears again for as long as VOR self-test is actuated.

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EHSI to/from display indicates from

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Associated RDDMI pointer drives to 180 |3 degrees with respect to indicator compass card.

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Associated RDDMI pointer flags remain in view for 3 |1 seconds, retract from view, and 20 |5 seconds after initiating test, reappear and remain in view.

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 If during the VOR self-test, the EHSI course arrow is positioned 5 degrees on either side of the selected course, the course deviation bar will deflect to the appropriate first dot position on the course deviation scale.

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 For an ILS self-test, an ILS frequency is selected on the VHF NAV control panel and either the up/left or the down/right self-test is actuated in turn. Selecting an ILS frequency causes the EADI and EHSI glide slope and localizer scales to be displayed, the associated RDDMI VOR bearing pointers to park at 90 degrees, and the standby attitude/ILS indicator G/S and LOC flags to appear.
　
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