(8)  
Learock No. 888 Buffing Compound (Ref 20-30-31)

(9)  
Learock No. S-30 Buffing Compound (Ref 20-30-31)

(10)
Simoniz Polish (Ref 20-30-31)

(11)
Plex-I-Glow Cleaner and Polish (Ref 20-30-31)

(12)
Wet-or-Dry Sandpaper No. 600-A to 100-A

(13)
Isopropyl Alcohol-TT-I-735 (Ref 20-30-31)

C.  Repair Scratched or Crazed No. 3 Windows
(1)  
Inspect chip carefully to ensure no cracks propogate from chip.

(2)  
Chips determined to be in mounting bolt holes and large chips in window surface should be repaired per Overhaul Manual.

(a)  
Use optical micrometer to check that window thickness permits rework. Outer panes

0.380 inch minimum after rework.

(b)  
Mask window frame and exposed seal with tape.

(c)  
Provide water spray.

(d)  
Remove loose dirt with water spray and hand.

(e)  
Remove minor clamshell surface chips, scratches and/or surface crazing with an abrasive paper or cloth appropriate to the surface starting condition (generally not coarser than 100 grit for gouges, deep scratches and severe crazing). Use ample water to keep the window surface cool and to flush away grit and acrylic material removed. A vibrating sander (approx. 8000 cpm) stroked with alternating 100% horizontal coverage, followed by 100% vertical coverage over the entire window surface works well. Two to five minutes of coarse grit sanding will remove approximately 0.005 inches of acrylic from a typical cockpit window. Change abrasive paper frequently, flush well with water, and continue until all surface damage is removed and the surface appearance is uniform. Then continue for approximately two more minutes to ensure complete removal of craze/cracks.

NOTE:  If the condition requiring repair is minor, start with finer abrasive to reduce subsequent polishing time. Do not attempt to rework only a local part of the surface area as this will result in optical distortion.

(f)  
Polish the window with a graduated series of abrasive materials. Use 100 - 600 grit paper and micromesh cloths of 1600 - 8000. Continue each step until the polishing marks of the previous step are removed (normally 2 - 3 minutes). Use alternating horizontal and vertical strokes with the vibrating sander and make sure the water flow is continuous.

(g)  
Check finished window dimensions. Minimum outer pane thickness permitted after repair is 0.380 inch. This thickness can apply uniformly to the whole surface.

(h)  
Remove water spray.

(i)  
Finish polish the window with buffing compound and a clean muslin or wool pad. If necessary, use coarse and fine compounds to obtain a high gloss. If a rotary buffer is used, wheel surface speed should be 3200 fpm for coarse compound and 4200 fpm for fine compound.

(j)  
Check window visually for optical quality. If distortion exists, repeat the procedure provided outer pane thickness will meet 0.380 inch minimum after rework.

(k)  
Wax window surface (Ref Maintenance Practices).

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2.  Repair of Chipped No. 3 Windows
(1)  Clamshell chips on the pane edge may be sanded to a 62 RHS finish, provided limits in Inspection/Check are not exceeded.
500 
Oct 20/88  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  56-11-21 Page 803 

WINDOWS NO. 4 AND 5 -REMOVAL/INSTALLATION
1.  General
A.  Windows No. 4 and 5 are pressure sealed on installation by means of a beaded silicone rubber molded-in-place pressure seal (Fig 401). The beaded rubber seal is molded to the window mounting surface. A continuous bead molded in the rubber seal ensures an effective pressure seal around the window.
B.  Fairing compound is applied to the window frame and its purpose is to accommodate the irregularities in the frame surface, ensuring that a perfectly flat surface is presented to the windowpane. The thickness of the compound varies: at high spots on the window frame there is no compound.
C.  Also shown on Fig. 401 are some items which are not components of the pressure seal. They are:
(1)  
Aerodynamic Smoother. Aerodynamic smoother is installed in the gap between the window frame and the edge of the pressure seal and windowpane and provides aerodynamic flushness and protection against water entrapment. A nylon cord, or nylon thread, is installed under the aerodynamic smoother to facilitate its removal when required.

(2)  
O-rings. Ethylene propylene O-rings are installed under the nut washers. The O-rings are allowed to compress a predetermined amount thereby transmitting sufficient compression load into the window assembly to compress the seal bead to make a weather seal.
　
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