TOMARK, s.r.o.
Airplane Maintenance Manual
Chapter 51 Standard Practices Structure
Page 154 Issue: 28.FEB 2017
51-72-02 Medium Damage
Repair of damage by replacing the stiffener part, by mastic and
varnish repair. At such repair it is necessary to distinguish type of
used stiffener (especially for sanding):
C/K (carbon/Kevlar), roving of fabric of black color (C) take turns with
yellowish (K)
G (glass), rovings from milky white to transparent
Preparatory Sanding
DANGER Explosion hazard due to abrasive dust.
▶ Remove adhesive and dope only in explosion proof rooms with
exhaustion device.
WARNING Poisoning hazard due to abrasive dust.
▶ Wear externally ventilated protective clothing, protective goggles,
chemical resistant gloves and respiratory mask when removing
adhesive and dope.
NOTE In case of C/K stiffener K roving tend to rise up from the surface at
sanding - it is difficult to sand them, we recommend using diamond
sanding tool and one-way sanding.
▶ Use dry sanding equipment with suction from sanding area.
▶ Use Al2O3 or equivalent (fused corundum) as sanding material.
▶ For good adhesion of repair layers sand up to the depth of damage.
▶ Sand the surface of the damage area with an overrun of at least
25 mm (1 in) for every damaged stiffener layer smoothly up to the top
layer and then about 51 mm (2 in) for finishing and mastic
application.
▶ Sand with sanding material having grain size of 160.
Dust Removal
▶ Wipe with clean and dry brush or use a vacuum cleaner.
Stiffener Preparation
▶ For this kind of repairs use the stiffener G (glass) with plain weave
150 g/m2 (0.037 lb/ft2), with surface protection for epoxy resins.
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