Extra 300LT, Maintenance Manual

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CHAPTER 51
PAGE 42 PAGE DATE: 21. March 2014
MAINTENANCE MANUAL EXTRA 300LT
exceedance. In case an elongated hole, a crushed plywood
insert or fuzzy or delaminated surrounding fiber plies are
identified, oversized flange bushing are needed. Contact
Extra Flugzeugproduktions- und Vertriebs GmbH for advice
and repair instructions.
Use a mixture of epoxy-resign Epikote Resin L20 with
Epikure Curing Agent 960 (for mixing ratio ref. Chapter 51-
30-01) and cotton flocks. The weight ratio should be 100
parts L20/960 with 7 up to 15 parts cotton flocks (so called
"HB7" and "HB15").
For re-bonding of flange bushings the wing has to be re-
moved from the fuselage first.
1 Remove wing from the fuselage. Refer to the applicable
Chapter of this Manual.
2 Carefully remove the front or rear loose flange bushing from
the main spar at a time. If a tool is needed, handle with care
to prevent damage of adjacent composite structure. The re-
maining flange bushing will be used to align the removed
flange bushing during the re-bonding process.
3 Visually check the exposed surface area of the hole in the
spar web for any damage.
4 Remove any residual resin debris existing on the bonding
surface of the flange bushing. Protect the inner surface of
bushing and sandblast or use 80-grit sandpaper to rough the
outer surface which will be bonded later on (no remaining
shiny areas are allowed).
5 Solvent clean the bushing thoroughly with isopropyl alco-
hol, carbon-tetrachloride or acetone.
W A R N I N G Solvents used for cleaning re-bond areas are flamma-
ble liquids and should be used with proper ventilation
and safety equipment.
6 Take 80-grit sandpaper and sand the exposed surface area of
the hole in the spar web where the bushing will be placed
later on smooth. Any remaining material from the initial bond
within the hole must be removed. Use 120-grit sandpaper
to rough the ring surface area of the main spar web where
the flange of the bushing will be bonded to later on.