Cirrus SR20 2010, Maintenance Manual

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51-20
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EFFECTIVITY:
C I R R U S
A I R P L A N E M A I N T E N A N C E M A N U A L M O D E L S R 2 0
01 May 2012
(5) Repair Surface Preparation
Generally, hand-sanding or a orbital type sander are the preferred methods of repair surface
preparation. Care must be exercised not to apply excessive pressure on the sander, which could
tear into the laminate. The grade of sanding paper is to be chosen to suit and give a smooth fin-
ish. Do not use grinders, air files, or other single-action tools as they tend to intensify pressure
and will rapidly remove paint and damage the underlying laminate.
To facilitate proper sanding depth and surface coverage, marking the composite repair area with
a permanent maker to act as a depth tracer is recommended.
Remove dust and observe laminate surface frequently during the sanding procedure. If fiber
damage is apparent, stop sanding and repair the damaged area. When preparing peel ply sur-
faces, sand surface until the impression left from the peel ply is no longer visible. When prepar-
ing surfaces where no peel ply was present, such as barrier film, sand surface until no gloss is
visible. Replace or clean sandpaper often.
The repair surface must be free of EMM in an area equal to the size and shape of the largest
repair ply plus 0.5".
CAUTION: Do not use chemical strippers to remove surface protection. Chemical strippers
may leave a residue and breakdown the epoxy resin.
Note: To prevent possible re-contamination of the repair area, the repair must be done
immediately following repair surface preparation.
(a) Acquire necessary tools, equipment, and supplies.
(b) Remove damage from repair area. (Refer to 51-20)
(c) Determine warp axis and draw 0° reference line so it intersects the center of the damage.
This line will later be used for positioning repair plies.
(d) Mask off area surrounding repair with masking tape and paper. This area should include
the intended faying surface area plus at least 2 inches (50 mm).
(e) If applicable, install backing plate. (Refer to 51-20)
(f) For secondary bond damage, sand repair area:
Description P/N or Spec. Supplier Purpose
Tape - Any Source Masking.
Paper - Any Source Masking.
Vacuum - Any Source Cleaning.
Paint Brush - Any Source Cleaning.
Permanent Marker (Refer to 51-30) (Refer to 51-30) Depth tracer.
Sanding Pad - Any Source Abrasion.
Aluminum Oxide Paper
(hand sanding) 60 to 80 grade Any Source Abrasion.
Orbital Sander - Any Source Abrasion.
Aluminum Oxide Paper
(orbital sander) 120 to 180 grade Any Source Abrasion.