CHAPTER 51
PAGE 43
PAGE DATE: 21. March 2014
MAINTENANCE MANUAL EXTRA 300LT
N O T I C E Bonding area must be free of dirt, dust and grease.
7 Remove sanding dust with a pneumatic vacuum cleaner and
solvent clean the surface area of the hole in the spar web
with isopropyl alcohol, carbon-tetrachloride or acetone in
case dirt or grease was introduced during the preparation.
8 Prepare a sufficient amount of epoxy resin compound L20/
960. The weight ratio is: 100 parts L20 with 34 parts 960
(ref. Chapter 51-30-01). Record quantities of parts to be
mixed, ambient air temperature and humidity.
9 Apply a sufficient amount of epoxy resin compound L20/
960 to the exposed surface area of the hole and the ring
surface area of the main spar web. Additionally apply "HB15"
compound.
10 Apply a sufficient amount of epoxy resin compound L20/
960 to the outer surface area of the flange bushing which
will be bonded to the spar. Additionally apply "HB15" com-
pound.
11 Apply mold-release agent to the surface of the related wing
main bolt. Insert the bolt to the flange bushing which is still
fixed in the main spar (opposite side) to provide a guidance
for the flange bushing to be bonded to the spar.
12 Insert the flange bushing to the hole. Slide on the main bolt
and slightly rotate the bushing clockwise or
counterclockwise while it is moved into the hole of the spar
web. A continuous movement is required to minimize en-
trapped air. Avoid partly removing and reapplying, as this
will cause air to become entrapped in the bonding gap.
13 Verify epoxy resin compound at the edge of the flange bush-
ing is continuous and free of gaps.
14 Remove excessive resin compound at the flange with cloth
damped with isopropyl alcohol.
15 Do not apply any pressure on the flange bushing prior to
complete curing cycle. Disturbing the flange bushing may
create bonding voids.
16 Apply curing procedure (specified time and temperature):
At elevated room temperature 25°C (77°F) for 10h.
17 Remove the main bolt from the flange bushing.
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