AIRPLANES WITH
GPWS INSTALLED 06 Page 401 Dec 25/8734-46-01
PERISCOPIC SEXTANT MOUNT - DESCRIPTION AND OPERATION
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1. General
_______
A. The airplane is provided with direct access from the flight deck to the outside atmosphere as a provision for using a periscopic sextant. A small port in the flight compartment ceiling provides this access and is normally covered by a shutter assembly. The shutter is a subassembly of the periscopic sextant mount and has provisions for attaching a gimbal base.
2. Shutter Assembly________________(See figure 1.)
A. When the sextant is not in use, the shutter assembly provides an airtight seal over the access hole. When the sextant is in use, the shutter is drawn aside and the sextant is extended so that the tip of the tube is exposed 1-1/2 inches above the airplane. The access hole is also used to evacuate smoke from the flight compartment when the airplane is pressurized. A decal is placed near the handle lanyard calling attention to this additional function.
B. The shutter is spring loaded. Pulling down on the lanyard is all that is required to operate the shutter.
C. A drain plug is provided at the low point in the shutter retraction well for draining water which might have collected in the mount.
D. The sextant mount is equipped with gimbals which allow the sextant to be compensated for variation of airplane attitude up to 15 degrees. The gimbal base is attached to the shutter assembly and may be rotated 360 degrees in azimuth.
E. The position indicator on the gimbal base is lighted with a 3-volt lamp, and is controlled by an ON-OFF toggle switch. Power to the lamp is supplied from a step-down transformer located in the P6 panel. (Refer to 33-15-00, Flight Compartment Auxiliary Lights.)
EFFECTIVITY
ALL 12 Page 1 Aug 25/9034-49-00
ILLUSTRATION OF SEXTANT MOUNT ON AIRPLANES REQUIRING SHUTTER HANDLE FORWARD OF SHUTTER OPENING
Periscopic Sextant Mount Shutter - Component Location Figure 1
EFFECTIVITYALL
790 Page 2
34-49-00
Aug 25/84
PERISCOPIC SEXTANT MOUNT - ADJUSTMENT/TEST
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1. General
_______
A. The operational test of sextant mount provides the check of the shutter assembly and the system test checks the alignment of the gimballed sextant mount.
2. Operational Test - Shutter Assembly
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A. Test Shutter Operation
(1)
Verify that shutter is closed and handle is pointing forward.
(2)
Pull shutter lanyard down. Check that handle is pointing aft and shutter is opened.
(3)
Pull shutter lanyard forward. Check that handle is pointing forward and shutter is closed.
NOTE: On airplanes with sextant mount rotated 180 degrees, handle
____ will be pointing aft when shutter is closed and handle will be pointing forward when shutter is open.
3. System Test - Periscopic Sextant Mount
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A. General
(1) The periscopic sextant mount system test utilizes a periscopic sextant to check the alignment of the gimballed mount with the airplane centerline.
B. Referenced Procedures
(1)
33-15-00, Flight Compartment Auxiliary Lights
(2)
Kollsman Document K214-500-658, Installation and Alignment Instructions for Kollsman Periscopic Sextant Mount with Azimuth Scale. Kollsman Type A28460-00-002.
C. Equipment and Materials
(1) Periscopic Sextant - Kollsman A28450-00-001
D. Test Sextant Mount
(1)
Perform shutter operational test. Leave shutter open.
(2)
Ensure that periscopic sextant light circuit breaker is closed.
(3)
Insert periscopic sextant in mount. Verify that sextant is correctly positioned as Pul1-to-Retract-Sextant knobs snap in place.
(4)
Check that sextant is free to rotate smoothly in either direction.
(5)
Connect electrical cable to receptacle on mount and on sextant.
(6)
Set the light switch on the mount to ON. Check that the true heading counter on the mount, the horizon and azimuth scale as viewed in the sextant eyepiece and the average scale on the sextant are illuminated.
(7) 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(54)
