Cessna 150M - Wing, Horizontal Stabilizer Angle Of-Incidence and Wing Twist; Wing; Wing Skin

18-1. STRUCTURAL REPAIR.
18-2. REPAIR CRITERIA. Although this section
outlines repair permissible on structure of the air-
craft, the decision of whether to repair or replace a
major unit of structure will be influenced by .such
factors as time and labor available, and by a com-
parison of labor costs with the price of replacement
assemblies. Past experience indicates that replace-
ment, in many cases, is less costly than major re-
pair. Certainly, when the aircraft must be restored
to its airworthy condition in a limited length of time,
replacement is preferable. Restoration of a damaged
aircraft to its original design strength, shape, and
alignment involves careful evaluation of the damage,
followed by exacting workmanship in performing the
repairs. This section suggests the extent of struc-
tural repair practicable on the aircraft, and supple-
ments Federal Aviation Regulation, Part 43. Con-
sult the factory when in doubt about a repair not
specifically mentioned here.
18-3. EQUIPMENT AND TOOLS.
18-4. SUPPORT STANDS. Padded, reinforced saw-
horse or tripod type support stands, sturdy enough to
support any assembly placed upon them, must be
used to store a removed wing or tailcone. Plans for
local fabrication of support stands are contained in
figure 18-1. The fuselage assembly, from the tail-
cone to the firewall must NOT be supported from the
underside, since the skin bulkheads are not designed
for this purpose. Adapt support stands to fasten to
the wing-attach points or landing gear attach-points
when supporting a fuselage.
18-5. FUSELAGE REPAIR JIGS. Whenever a repair
is to be made which could affect structural alignment,
suitable jigs must be used to assure correct align-
ment of major attach points, such as fuselage, fire-
wall, wing and landing gear. These fuselage repair
jigs are obtainable from the factory.
18-6. WING JIGS. These jigs serve as a holding fix-
ture during extensive repair of a damaged wing, and
locates the root rib, leading edge and tip rib of the
wing. These jigs are also obtainable from the factory.
1
18-7. WING, HORIZONTAL STABILIZER ANGLE-
OF-INCIDENCE AND WING TWIST.
18-8. The following chart lists wing angle-of-inci-
dence and wing twist and horizontal stabilizer angle-
of-incidence. Stabilizers do not have twist. Wings
have a constant angle from the wing root to t he strut
fitting station. All twist in the wing panel is between
the strut fitting and the tip rib. The amount of twist
between these points is the difference between the
angle-of-incidence at the root and the angle-of-inci-
dence at the tip. Refer to figure 18-2 for instructions
for checking wing twist.
WING
Angle-of-incidence, Root
Angle-of-incidence, Tip
Twist (Washout) . . . .
18-2 Change 3
STABLILIZER
Angle -of -incidence
18-9. REPAIR MATERIALS. Thickness of a mate-
rial on which a repair is to be made can easily be de-
termined by measuring with a micrometer. In gen-
eral, material used in Cessna aircraft covered in
this manual is made from 2024 aluminum alloy, heat
treated to a -T3, -T4, or -T42 condition. If the type
of
material cannot readily be determined, 2024-T3
may be used in making repairs, since the strength
of -T3 is greater than -T4 or -T42 (-T4 and -T42
may be used interchangeably, but they may not be
substituted for -T3). When necessary to form a part
with a smaller bend radius than the standard cold
bending radius for 2024-T4, use 2024-0 and heat
treat to 2024-T42 after forming. The repair mate-
rial used in making a repair must equal the gauge of
the
material being repaired unless otherwise noted.
It is often practical to cut repair pieces from service
parts listed in the Parts Catalog. A few components
(empennage tips, for example) are fabricated from
thermo-formed plastic or glass-fiber constructed
material.
18-10. WING.
18-11. DESCRIPTION. The wing assemblies are a
semicantilever type employing semimonocoque type
of structure. Basically, the internal structure con-
sists of built-up front and rear spar assemblies, a
formed auxiliary spar assembly and formed sheet
metal nose, intermediate, and trailing edge ribs.
Stressed skin, riveted to the rib and spar structures,
completes the rigid structure. Access openings
(hand holes with removable cover plates) are located
in the underSide of the wing between the wing root
and tip section. These openings afford access to
aileron bell cranks, flap bellcranks, electrical wiring,
strut attach fittings, control cables and pulleys, and
control disconnect points.
18-12. WING SKIN.
18-13. NEGLIGIBLE DAMAGE. Any smooth dents
in the wing skin that are free from cracks, abrasions
and sharp corners, which are not stress wrinkles and
do not interfere with any internal structure or mech-
anism, may be considered as negligible damage. In
areas of low stress intensity, cracks, deep scratches,
or deep, sharp dents, which after trimming or stop-
drilling can be enclosed by a two-inch circle, can be
considered negligible if the damaged area is at least
one diameter of the enclOSing circle away from all
existing rivet lines and material edges. Stop drilling
is considered a temporary repair and a permanent
repair must be made as soon as practicable.
18-14. REPAIRABLE DAMAGE. Figure 18-4 out-
lines typical repair to be employed in patching skin.
Before installing a patch, trim the damaged area to
form a rectangular pattern, leaving at least a one-
half inch radius at each corner, and de-burr. The
sides of the hole should lie span-wise or chord-wise.
A circular patch may also be used. If the patch is
in an area where flush rivets are used, make a flush
patch type of repair; if in an area where flu;::" .civets