PS-28 Cruiser
PS-28N Cruiser
CR-MM-1-0-00
CHAPTER 15 – AIRPLANE REPAIRS
Revision No.: -
Date of issue: 2011-03-08
15 - 8
1 Correctly located patch
2
Incorrectly located patch
Fig. 15-3
: Location of patches on the airplane skin
Mark the damaged surface area (preferably by spirit felt tip) and cut out the most suitable
geometrical shape (circle, square, rectangle).
Be careful that all cracks as well as adjacent corroded areas are cutted out. Corners of cut
out holes in the skin must have minimum radius of 12.7 mm (
0.5 in
) and their edges must
be smoothly filed off.
Size of patch overlapping depends on the cut out of skin area:
(a)
Patch up to the area of 51.6 cm
2
(8 in
2
)
- rivet by one row of rivets, the patch edge
must overlap the edge of the cut out hole by minimum 19 mm (
0.75 in
).
(b)
Patch with the area over 51.6 cm
2
(8 in
2
)
- rivet by two rows of rivets, the patch edge
must overlap the cut out hole by minimum 32 mm (
1.25 in
).
Both ways of patching are shown on Fig. 15-5.
If the damaged area is located near the spars and frames, choose such patch dimension
so that it covers all these elements of structure and it is possible to rivet it (Fig.15-4).
Types of patches, according to their position on the airframe structure.
(a)
Surface patches
- These can be used in the areas where surface smoothness is not
important
(b)
Sunk patches
- Use for patches on the wing, tail unit and control surfaces.
(c)
Surface patches across obstacles and stiffeners in the skin
- pay special attention
to drilling the patch together with the surrounding structure. Attach the patch in several
points and then drill holes for rivets from inner side (if possible). Use original holes in
frames and stiffeners.