Boeing F4B-1 - Page 10

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10. LINE-UP (Reference Fig. 7): a. There are three leveling positions which
can be used. These are as follows:
A-B. Laterally on lugs on lower longer_ons.
B-C. Longitudinally on lugs on lower nght longeron.
D. Laterally across the top longerons, near sta. 8.
For ordinary alignment the points A, B and C are the only ones used. A
leveling board approximately 20 inches long will be necessary in checking the
longitudinal level. . .
b. In handling the fuselage care must be taken to lift and support it only at
strut points. Always secure the fuselage so that it can not fall from its supports.
11. TESTING ALIGNMENT (Reference Fig. 7 and 8): a. The construction
of the fuselage is such that no adjustment necessary ( or possible) except in lower
bays Sta. 1-2 and 2-3. If fo_r any reason the fu~elage _is_ thought _to be out of line,
level it at A-B and B-C (Fig. 7), place a level m posit10n D (Fig. 7) and drop a
plumb-bob from the ~op of the tail post. This_ will indicate any serious misalign-
ment in the rear port10n of the fuselage. The alignment should be checked further
by attaching a center line from front to rear and taking measurements as shown
in Fig. 8.
b. When installing the brace wires in the bottom of the fuselage between
stations 2, 3 and 4, check the alignment by trammelling diagonally across the
bays. Trammel marks will be found on the lower side of the longerons between
the fitting bolts.
12. MAINTENANCE: a. Inspect the fuselage at intervals for corrosion,
loose bolts, worn fittings, etc. Clean and paint if necessary.
b. Many fuselage fittings, particularly at lower stations 3 and 4, are provided
with drain holes. These must be kept open and replacement fittings are to be
similarly drained.
c. To lift the tail, when moving the airplane on the ground, insert a crowbar
or heavy gauge steel pipe at least four feet long in the lifting tube provided. Any
attempt to lift otherwise will result in damage to the light formers under the fabric.
13. REPAIRS (Reference Fig . 8 and 10): a. Before undertaking repairs, note
the following:
Duralumin members and fittings in the fuselage are heat-treated, and replace-
ments must be made with heat-treated duralumin or with steel parts of the same
dimensions. The heat-treatment of duralumin parts is to be in accordance with
A. P. S. No. 21.
When replacing steel parts refer to the Alloy Steel Chart on page 43.
Figure 10 and the table on page 17 give the necessary information on the size
of fuselage members.
Before removing parts , support and secure the fuselage so that its alignment
will be preserved.
Duralumin parts must not be welded.
Bolt holes are to be drilled at assembly and reamed for a light drive fit. Over-
size bolts must be used in repairs and replacements. When removing bolts to be
replaced, care must be taken not to enlarge the holes.
Repairs are to be finished in accordance with Spec. S. D. 81.
b. When tubular members are dented, chafed, or partially cut, so that their
end attachments are not injured and their tensile strength not seriously reduced,
satisfactory repairs may be made by installing a reinforcement sleeve around
the damaged part as shown in Fig. 9. The sleeve may be made of steel or heat-
treated duralumin and is to be not less than .057 inches thick. ·
. If .058 inch thick square tubing can be obtained whose outside width is ½ of
a!1 mch great~r ~han that _of the _tube being reinforced, a sleeve may be made very
simply by _splittmg a section of it along one corner. If such square tubing should
~10t be avai!abl~, · an entirely satisfactory sleeve may be made of sheet material, as
illus~r~ted m Fig. 9. Note that the edges of the sleeve are flanged, as this aids in
o~tammg a snug fit and contributes to the strength. The sleeve is to be fastened
with dural (or steel) bolts the same size as those used in attaching the ends of the
member: The number of bolts in each half of the sleeve should be equal to the
number m the end of the member, but in no case less than three. Note the spacing
of the bolts in Fig. 9.
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