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| MIL-T-18232B(AS)
BOLTS. - Taper bolts and self-locking bolts shall be used
3.1.20.14
only upon specific approval of NAVAIR. Steel bolts smaller
than one-fourth inch in diameter shall not be used in any single bolted structural
connection. Aluminum alloy bolts} nuts, and screws shall be used in nonstructural
lightly stressed aluminum alloy parts except electrical assemblies. Structural
bolts which are loaded in tension shall be prestressed to a value consistent with
minimizing the effects of fatigue in the joints. Bolts shall be inserted with
the head uppermost or forward unless specifically approved otherwise by the LGR.
In the mechanical portion Of the propulsion control system including induction
air control, propeller control, auxiliary power plant control, etc., self-retaining
bolts shall be used at all joints which serves as an axis of rotation or is
designed to transmit motion which may result in relative rotation between the
components of the joint. The bolts shall be additionally locked in position by
slotted, self-locking nuts properly secured by cotterpins. The self-retaining
bolt shall be designed to remain in place and maintain the control system function
should the cotterpin or nut become disengaged. The bolt shall be designed so it
can be removed without damage to the mating parts and shall be reusable.
3.1.20.14.1
CIEVIS BOLTS. - Clevis or other equivalent shear-type bolts
with self-locking nuts, or with shear nuts properly secured
cotterpins, shall be used in all locations where loss of the bolt would adversely
affect safety of flight, for example: propulsion and flight controls and wing
bolts. Clevis or shear-type bolts shall be of correct grip and length in order
to prevent looseness or binding. (For self-locking nuts, see 3.1.30.17.1)
3.1.20.14.2
CLOSE-TOLERANCE BOLTS. - AN173-186, NAS464$ and NAS334-340
close-tolerance series or equivalent bolts or pins shall be
used in shear connections of wings, aerodynamic stabilizing surfaces, control
surfaces~ engine mounts, etc., to their adjacent principal assemblies, except
where the number of bolts is sufficient to obtain a group effect and the connec-
tion is such as not to require the improved fatigue characteristics of close
tolerance fasteners. The actual hole diameter for bolts or pins of 0.500 inch or
less shall not exceed the nominal bolt diameter by more than 0.001 inch. The
actual hole diameter for bolts or pins greater than 0.500 inch up to and including
l.00O inch, shall not exceed the nominal bolt diamter by more than 0.0015 inch.
The actual hole diameter for bolts or pins greater than 1.000 inch shall not
exceed the nominal bolt diameter by more than 0.002 inch. For connections in-
corporating antifriction bearings, the maximum diameters of the hinge-pin holes
in the supporting structure adjacent to the bearing shall be reamed to the nominal
standard size allowing a total tolerance of 0.00l inch.
3.1.20.15
PINS. - Flat head pins shall not be used where loss would
adversely affect safety of flight. Taper pins shall be
threaded and shall be secured with nuts and cotterpins or with self-locking nuts.
SPRINGPINS. - Spring pins, such as "Sel-lok", "Rollpin",
3.1.20.15.1
and "Spirol Pin" may be used.
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