AIRCRAFT MAINTENANCE MANUAL
DFE-AMM-AR1
Rev. 1 – 07/24/2014
10-8
10.3.2.2.2.
Medium Damage
•
Tools needed: sand paper, scissors,
•
Parts needed: epoxy resin, drills, fiberglass cloth , degreasing agent
•
Type of maintenance: Line
•
Level of Certification needed:
-
Repairman (LS-M) or Mechanic (A&P) – both with the minimum level of certification to
perform heavy maintenance of SLSA in the U.S.
-
FAA approved Part 145 Repair station
•
Instructions:
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 grinding):
•
C/K (Carbon/Kevlar), roving of fabric of black color (C) take turns with yellowish (K)
•
G (glass), roving from milky white to transparent
Preparatory grinding
For good adhesion of repair layers it is necessary to do grinding up to the depth of
damage. It is necessary to do surface grinding from the damage area with overrun at the least
25 mm (1 in) for every damaged stiffener layer smoothly up to the top layer and then about 50
mm (2 in) for finishing and mastic application. It is convenient to do grinding with grinding
material having grain size of 160. It is carried out by dry grinding equipment with suction from
grinding area. Al203 Aluminum Oxide Power (fused corundum) can be used as grinding
material.
In case of Carbon/Kevlar stiffener, Kevlar roving tend to rise up from the surface at grinding - it is difficult to
grind them, we recommend using diamond grinding tool and one-way grinding.
Dust removing
Dust is removed by wiping with a clean and dry brush or by a vacuum cleaner.
Stiffener preparation
For this kind of repairs we recommend the stiffener G (glass) with plain weave, 150g/m
2
,
with surface protection (dewing) for epoxies.
Number of needed stiffener layers depends on depth of damage. It is possible to say that
each layer of the mentioned fabric represents at proper saturation by matrix resin thickness of
0.5 mm (0.02 in).
Stiffener layers must be prepared (cut out) gradually from the smallest (the lowest) up to
the bigger (upper), each with overrun of 20 mm (0.78 in).
