Equipment And Tools For Structural Repair; Repair Materials; Wing Angle-Of-Incidence; Wing Skin Damage - Cessna 177 SERIES Service Manual

18-1. STRUCTURAL REPAIR.
(empennage tips, for example) are fabricated from
thermo-formed plastic or glass fiber constructed
18-2. REP.IR CRITERIA.
Although this section material.
outlines repair permissible on structure of the air-
craft. the decision of whether to repair or replace a
18-8. WING ANGLE-OF-INCIDENCE. Angle-of-
major unit of structure will be influenced by such
incidence and wing twist are listed in the following
factors as time and labor available and by a com- chart.
The cantilever wing has a uniform twist
parison of labor costs with the price of replacement
from the root rib to the tip rib. The amount of
assemblies.
Past experience indicates that replace-
twist between these two ribs is the difference be-
ment. in many cases, is less costly than major re-
tween the angle-of-incidence at the root and the
pair. Certainly, when the aircraft must be restored angle-of-incidence at the tip.
See figure 18-2.
to its airworthy condition in a limited length of time,
replacement is preferable. Restoration of a damag-
Angle-of-incidence, Root------------- +330
'
ed aircraft to its original design strength, shape and
Angle-of-incidence, Tip-------------- + 30'
alignment involves careful evaluation of the damage,
Twist (Washout) ---------------------
3
°
followed by exacting workmanship in performing the
repairs.
This section suggests the extent of struc-
18-9. WING.
tural repair practicable on the aircraft and supple-
ments Federal Aviation Regulation, Part 43. Con-
18-10. DESCRIPTION. The wing is sheet-metal
suit the factory when in doubt about a repair not
constructed, with a single main spar, two fuel spars,
specifically mentioned here.
formed ribs and stringers. The front fuel spar also
serves as an auxiliary spar and is the forward wing
18-3. EQUIPMENT AND TOOLS.
attaching point. An inboard section forward of the
main spar is sealed to form an integral fuel bay
18-4. SUPPORT STANDS. Padded, reinforced saw- area.
The main spar consists of milled spar caps
horse or tripod type support stands, sturdy enough to
and attaching fittings joined by a web section. The
support any assembly placed upon them, must be used aft fuel spar is a formed channel.
The front fuel
to store a removed wing or tailcone. Plans for local
spar is a built-up assembly consisting of a formed
fabrication of support stands are contained in figure
channel, doubler, attach strap and support angle.
18-1.
The fuselage assembly, from the tailcone to the
Stressed skin, riveted to the ribs, spars and string-
firewall, must NOT be supported from the underside,
ers, completes the wing structure. Access openings
since the skin bulkheads are not designed for this pur- (hand holes with removable cover plates) are located
pose. Adapt support stands to fasten to the wing-
in the underside of the wing between the wing root
attach points or landing gear attach-points when sup-
and tip section. These openings afford access to the
porting a fuselage.
flap and aileron bellcranks, flap drive pulleys, flap
actuator in left wing, flap and aileron control cable
18-5.
FUSELAGE REPAIR JIGS. Whenever a repair
disconnect points, fuel transmitter, air scoop con-
is to be made which could affect structural alignment,
nectors and electrical wiring.
suitable jigs must be used to assure correct align-
ment of major attach points, such as fuselage, fire- 18-11. WING SKIN.
wall, wing and landing gear. These fuselage repair
jigs are obtainable from the factory. 18-12.
NEGLIGIBLE DAMAGE. Any smooth dents
in the wing skin that are free from cracks, abrasions
18-6. WING JIGS. These jigs serve as a holding
and sharp corners, which are not stress wrinkles
fixture during extensive repair of a damaged wing,
and do not interfere with any internal structure or
and locates the root rib, leading edge and tip rib of
mechanism, may be considered as negligible damage
the wing. These jigs are also obtainable from the
in any area of the wing. Outboard of wing station
factory.
40.00 in areas of low stress intensity, cracks, deep
scratches or sharp dents, which after trimming or
18-7. REPAIR MATERIALS.
Thickness of a mate-
stop drilling can be enclosed by a two-inch circle,
rial on which a repair is to be made can easily be de-
can be considered negligible if the damaged area is
termined by measuring with a micrometer. In gen-
at least one diameter of the enclosing circle away
eral, material used in Cessna aircraft covered in
from all existing rivet lines and material edges.
this manual is made from 2024 aluminum alloy, heat
The area on the lower surface of the wing between
treated to a -T3, -T4, or -T42 condition. If the
the two stringers adjacent to the main spar is not
type of material cannot readily be determined, 2024-
considered low stress intensity. Stop drilling is
T3 may be used in making repairs, since the strength
considered a temporary repair and a permanent re-
of -T3 is greater than -T4 or -T42 (-T4 and -T42
pair should be made as soon as practicable.
may be used interchangeably, but they may not be
substituted for -T3. When necessary to form a part
18-13. REPAIRABLE DAMAGE. Repairs must not
with a smaller bend radius than the standard cold
be made to the upper or lower wing skin inboard of
bending radius for 2024-T4, use 2024-0 and heat
station 40.00 without factory approval. However, an
treat to 2024-T42 after forming. The repair mate-
entire skin may be replaced without factory approval.
rial used in making a repair must equal the gauge of Refer to Section 1 for wing station locations. Figure
the material being repaired unless otherwise noted. 18-4 outlines typical repairs to be employed in patch-
It is often practical to cut repair pieces from service
ing skin. Before installing a patch, trim the damag-
parts listed in the Parts Catalog. A few components
ed area to form a rectangular pattern, leaving at
18-2