(8)
If azimuth scale reading does not agree with true heading counter within tolerance, reset sextant as follows:
(a) Remove cover adjacent to true heading counter on mount.
EFFECTIVITY
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(b) Loosen two setscrews in coupling exposed.
CAUTION: DO NOT ADJUST LOCKING NUT ADJACENT TO COUPLING
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SCREWS.
(c)
Hold coupling and crank true heading scale until true heading reading and azimuth scale reading against lubber line agree.
(d)
Tighten coupling setscrews.
(e)
Reset true heading counter to 000.0 and check that azimuth scale reading against the lubber line is 0 (|0.2) degrees. Replace cover.
(9)
Set true heading counter to 179.8 degrees.
(10)
Level artificial horizon in center of reticle field. Rotate sextant to align vertical crosshair to reticle with lowest visible point on centerline of vertical fin of airplane.
(11)
Lock line of sight lever. Check that the vertical crosshair coincides with 359.8 (| 0.2) degrees on azimuth scale in the reticle
(12)
If airplane vertical fin cannot be observed, adjust as follows:
(a)
Establish the airplane centerline by means of plumb bobs hung from forward and aft centerline marks on airplane fuselage.
(b)
At a considerable distance in front of the airplane (at least 100 feet or as required) set a vertical pole 5.25 inches to left of airplane centerline.
(c)
Set the true heading to 000.0.
(d)
Level artificial horizon in center of reticle field. Rotate sextant to align the vertical crosshair of reticle with lowest visible point on the pole.
(e)
Lock line of sight lever. Check that the vertical crosshair coincide within 0 (| 0.2) degree on the azimuth scale on the reticle.
(13)
If the crosshair of sextant does not coincide with true heading within tolerance, reset as follows:
(a)
Loosen four lubber line clamp screws on mount.
(b)
Grasp portion of mount containing the lubber line and rotate sextant assembly until vertical crosshair of sextant coincides with the pole and with 0 (|0.2) degree on the azimuth scale in the reticle.
(c)
Tighten four clamp screws.
(14)
Remove sextant and close shutter.
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SHUTTER ASSEMBLY - REMOVAL/INSTALLATION
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1. General
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A. The shutter assembly is installed on the aft control cabin ceiling. Access to the mounting screws is on top of the airplane. The shutter assembly must be supported from below during removal and installation.
2. Remove Shutter Assembly (Fig. 401).
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A. Open periscopic sextant light circuit breaker on panel P6.
B. Disconnect electrical connector on mount.
C. Support shutter assembly and remove 12 mounting screws.
D. Remove shutter assembly and gasket.
3. Install Shutter Assembly (Fig. 401).
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A. Position gasket and shutter assembly in place and install 12 mounting screws.
B. Connect electrical connector to mount.
C. Close periscopic sextant light circuit breaker on panel P6.
D. Test shutter assembly as follows:
(1)
On mount installations with shutter handle FWD and to the right:
(a)
Pull shutter lanyard down. Check handle is pointing forward and shutter is open.
(b)
Pull shutter lanyard aft. Check handle is pointing aft and shutter is closed.
(2)
On mount installations with shutter handle AFT and to the left:
(a)
Pull shutter lanyard down. Check handle is pointing aft and shutter is open.
(b)
Pull shutter lanyard forward. Check handle is pointing forward and shutter is closed.
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Shutter Assembly - Removal/Installation
Figure 401
EFFECTIVITY ALL
799 Page 402 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：747飞机维护手册AMM CHAPTER 34 - NAVIGATION 第34章导航4(55)
