TOMARK, s.r.o.
Airplane Maintenance Manual
Chapter 51 Standard Practices Structure
Issue: 28.FEB 2017
Page 147
51-71-03 Stopping Cracks
Enlarging of small cracks can be stopped by drilling a hole at the
utmost end of the crack as shown in the following:
▶
Support the place of drilling with a wooden block at drilling thin skin
and use the sharp drill bit so that it will not drift and will not cause
another damage to the skin.
▶
At drilling the crack of the skin in the area of the flange, supporting
stiffener etc., protect these parts before drilling by supporting the
drilled place by means of the thin steel band.
▶
Drill a hole with the drill bit of diameter 3.2 mm (1/8 in) at the utmost
end of the crack.
▶
Check in the operation whether the crack was successfully stopped.
▶
If enlarging of the crack continues, repeat the drilling.
If the crack still enlarges after repeated drilling, the affected area has
to be cut out and the skin must be repaired by means of the patch -
see next paragraph. However this repair can be made only by
TOMARK, s.r.o. Aero division as producer or by authorized repair
shop - for more detailed information contact TOMARK, s.r.o.
51-71-04 Repairing the Skins with Patches
NOTE
The following procedure is intended for skin repairs only with
maximum area of the patch up to 200 cm
2
(area of the cut out skin).
▶
Before riveting the patch check the adjacent part of the inner
structure in the damaged area and find out whether its repair is
needed.
▶
Place patches on the fuselage so, that the longer patch side lies in the
longitudinal plane of the aircraft (in flight direction).