(3)
Crazing.
(a)
Crazing in the windshields is critical.
(b)
Determine depth of craze using a calibrated depth gauge or scale (see Figure 601).
(c)
A craze 0.031 inch (0.787 mm) deep is cause for replacement at the earliest opportunity.
(d)
Crazing in any portion of the windshields requires replacement.
(4)
Haze or foggy appearance on the glass is not acceptable if the amount of haze/fog causes an obstruction of vision in the area used for operation of the aircraft.
(5)
Blemishes.
(a)
Blemishes in windshields form in the vinyl plastic interlayer bonding the two glass panes together.
(b)
Blemishes in the critical or semi-critical portion of the windshields are not acceptable unless 0.062 inch (1.575 mm) or smaller in circumference, including distorted area.
(c)
No more than two blemishes, at least 12 inches (30.48 cm) apart are acceptable in the windshields.
(d)
No more than two blemishes within a two inch (5.08 cm) area along the upper portion of the windshields are acceptable.
(6)
Scratches.
(a)
Light scratches in the lower portion of the window and windshield are acceptable if they do not extend more than 1.00 inch (2.54 cm) from the outside windshield retainer and are less than 1.00 inch (2.54 cm) long.
6" SCALE
DEEPCRAZE
REFLECTION OF
SCALE
Determining Depth of Craze
Figure 601
EFFECTIVITY: 040-999
56-00-00 Feb 1/98
PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCEMANUAL
(b)
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.
(c)
Replace acrylic windows with scratches that cannot be reworked in accordance with these standards.
(7)
Delamination.
(a)
Cloudy or milky appearance in the delamination indicates moisture or solvent penetraton. Windshields with this condition should be replaced at the earliest opportunity.
(b)
Delaminated areas characterized by irregular or jagged boundaries indicate uneven separation of the vinyl and glass. This condition may cause the vinyl to pull chips from the inner glass surface, resulting in failure of the glass ply. Conduct periodic inspections to determine if the damage is progressive or if chipping of the inner glass surface is present.
(c)
Replace windshield if any of the following condition are noted:
1) Evidence of chipping of inner glass surface.
2) Area of vision required for safe operation is affected (pilot's discretion). 3) Windshield heat system inoperative.
(8)
Cracks. Inspect for cracks as directed in paragraph 1 e, Crack Inspection -Acrylic Windows.
(d)
NON-CRITICAL AREA INSPECTION -CABIN WINDOWS. A non-critical area is a portion of a window not used for flight vision.
(1)
Mark-Off in moderate amounts is acceptable provided that visibility is not impaired.
(2)
Distortion.
(a)
Distortion along the sides of the window within 0.5 inches (1.27 cm) or less of the retainer is acceptable.
(b)
Distortion along the upper portion of the window is acceptable if distortion does not extend downward more than 2.00 inches (5.08 cm) from the top and does not impair vision.
(c)
Distortion of the main body of the side window is acceptable providing the distorted area does not exceed 25 percent of the window area.
(3)
Crazing.
(a)
Crazing in the window is critical.
(b)
Determine depth of craze using a calibrated depth gauge or scale (see Figure 601).
(c)
A craze of 0.062 inch (1.575 mm) depth is cause for immediate replacement. A craze 0.031 inch (0.787 mm) deep is cause for replacement at the earliest opportunity.
(d)
Crazing in any portion of the window requires replacement.
(4)
Haze or foggy appearance on the glass is not acceptable if the amount of haze/fog causes an obstruction of vision in the area used for operation of the aircraft.
(5)
Cracks. Inspect for cracks as directed in paragraph e, Crack Inspection -Acrylic Windows.
(e)
CRACK INSPECTION -ACRYLIC WINDOWS.
(1)
Perform this inspection annually or each 1,000 hours, whichever occurs first.
-Note -This inspection should also be performed after repainting when any chemical stripping agent was used. Use the prism method described in step (3) to inspect the entire circumference of the window for stripper damage/etching; especially in areas concealed by window frames, retainers, plates, or collars.
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