TOMARK, s.r.o.
Airplane Maintenance Manual
Chapter 51 Standard Practices Structure
Issue: 28.FEB 2017 Page 151
51-71-10 Repair of U-Profile
Repair method consists in stiffening the damaged angle by means of
the new one. When repairing observes the following instructions:
▶ Determine the section area of the damaged angle S1.
▶ Choose S2 = 1.1 S1 as section area of the stiffening angle.
▶ Choose thickness t2 = (1 to 1. 3) t1.
▶ Drill of rivets in the area of repair.
▶ Choose the same rivet diameter as in the damaged place.
▶ Use at least two rivets on each side from the crack.
▶ For riveting follow Chapter 20-10-02 Rivets.
51-72 Repair of Composite Parts
General
Two kinds of parts are made from composite materials in the
airplane:
structural, load-bearing parts (canopy frame)
design appearance, non-load-bearing parts (fairings)
NOTICE Any damage of parts from reinforced plastics with epoxy matrix leads
to increased saturation of the matrix with humidity and subsequently
to loss of properties.
▶ Therefore carry out the repair as soon as possible after the damage
has occurred.
▶ Carry out the repairs by means of epoxy resin and glass or carbon
stiffeners.
Epoxy resin mixtures are prepared in a given mass ratio by means of
weighing (accuracy of scales 1 gram (0.002 lbs)).
Damage Classification
According to the damage size we can divide repairs into:
small damage (surface defects, not affecting the stiffeners)
medium damage (not more than 2/3 of stiffener thickness damaged)
major damage
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