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PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL

(2)  
Inspect window panes as follows:

(a)  
Inspect sealant for signs of wear, deterioration, and positive contact with mounting surfaces.

(b)  
Inspect window frames, retainers, plates, and collars for cracks, loose rivets or screws, corrosion, and structural defects.

(3)  
Inspect emergency exit and eyebrow window bolt holes using Window Inspection Kit, Part Number 766-294.

(4)  
Crack Limitation.

(a)  
The maximum acceptablelength of a crack from any single screw hole is 0.300 inch (7.62mm).

(b)  
The maximum combined length of multiple cracks into the space between two adjacent boit holes is 0.300 inch (7.62mm).

(c)  
If a crack less than 0.300 inch (7.62mm) is left unrepaired, reinspect the window each additional 25 hours of aircraft operation.

(d)  
A maximum of three bolt holes with cracks less that 0.299 inch (7.59mm) long are acceptable in any one window pane before that window pane must be replaced.

(e)  
Replace window pane if a single crack or combination of adjacent facing cracks exceed

0.300 inch (7.62mm) in length.
(5)  
Chips, Scratches, and Crazing Limitations.

(a)  
Scratches in acrylic windows may be reworked if:

1)  They are less than 0.030 inch (0.762 mm) deep.
2)  No vision distortions in critical and semi-critical areas as a result of rework.
3)  0.437 inch (11.099 mm) panes are a minimum of 0.393 inch (9.982 mm) thick after rework.
4)  0.375 inch (9.525 mm) panes are a minimum of 0.337 inch (8.559 mm) thick after rework.
(b)  Replace acrylic windows with scratches that cannot be reworked in accordance with these standards.
2.  Window Repair / Rework Procedure (Side Acrylic Windows Only). The following methods should be used for repairs:
-CAUTION-

ANY ACRYLIC WINDOW WHICH MAY HAVE BEEN DAMAGED BY PAINT THINNER, PAINT REMOVER OR OTHER SOFTENING AGENT MUST BE REPLACED. NO REPAIR IS PERMITTED FOR THIS TYPE OF DAMAGE.
(a)  
AREAS WITH SMALL SCRATCHES:

(1)  
Clean the window, using generous amounts of water and a mild detergent.

(2)  
Polish the window with an approved compound and soft cloth.

(3)  
Clean and wax the polished area.

EFFECTIVITY: 
040-999  PAGE 5 
Feb 1/98 

PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL

(b)  
AREAS WITH LARGE SCRATCHES, GOUGES AND NICKS: Areas with damages exceeding .003 of an inch depth or those with less than .003 of an inch in depth, having sharp edges which cause hanging of fingernail should be locally rounded out or buffed.

(1)  
Clean the window using generous amounts of water and a mild detergent.

(2)  
Use a scratch removal kit, such as the type supplied by Micro-Surface Finishing Products Inc.,

P.O. Box 456, Wilton, Iowa, to remove the defective area, blend and buff.
(3)  
Using 400A wet or dry abrasive paper wrapped around a smooth rubber block and generous amounts of water, lightly sand over and around the defected area in a circular motion, extending in a diameter equal to two or three times the defected area.

(4)  
Continue sanding until the initial defect is no longer apparent. Thoroughly flush the area with water.

(5)  
Using 600A wet or dry abrasive paper, repeat step (3). Continue sanding only until the hairline scratches caused by the coarse sanding are no longer apparent. Sand a larger area than that covered by the original sanding operation. Thoroughly wash the area.

(6)  
Finish the repair using instructions given in Method a.

3.  Cleaning Windshield and Windows
(a)  
Remove dirt, mud, etc. from exterior surface with clean water.

(b)
Wash with mild soap and water, or a 50/50 solution of isopropanol and water (do not use plastic cleaners on glass windshields). Use soft cloth or sponge with a straight gentle rubbing motion.

(c)
Rinse thoroughly and dry.

(d)
After cleaning, plastic surfaces can be polished with a thin coat of hard polishing wax. Rub lightly with a soft cloth. Use a circular rubbing motion.

NOTE: Do not apply wax to glass windshields with surface coatings for anti-static protection.

(e)
To improve visibility through rain, a repellent such as REPCON must be applied to windshield and windows, according to manufacturer's instructions.

EFFECTIVITY:
040-999

Feb 1/98 56-00-00
　
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