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Components mounted on the nose of other types
3.28.6 Control system adjustment. External
of engines or gear boxes shall be located to pro-
adjustment to the control shall be limited to
vide the necessary installation clearances as
adjustments which can be made correctly with
specified in 3.7. Those components mounted at
the propeller assembled. These adjustments
other locations on the engine shall conform to
shall be clearly marked and accessible with the
the provisions provided on the engine.
propeller installed.  A l l other adjustments
shall be protected to avoid tampering. The ex-
3.29.1 Attaching parts. Attaching parts
ternal adjustments shall be specified in the
utilized for either installation of a propeller
model specification.
or components and provided by the propeller Adjustments. When adjustments of
c o n t r a c t o r shall be listed in the model
limiting values of the controlled propeller
variables are required, positive features shall
3.30 Electrical harnesses. Electrical har-
be provided so that it shall not be possible to
nesses furnished by the propeller contractor as
preset the adjustments to the extent that will
components for the propeller control or ice con-
result in catastrophic consequences to the
trol systems shall be so constructed as to with-
stand the environmental conditions to which
3.28.7 Ground handling control. Adequate
they will be exposed, including vibration, temp-
provisions shall be provided for situations in
erature, abrasion, moisture and fire. An ac-
which it is desired to change pitch while the
ceptable harness construction is shown in
propeller rotational speed is at zero.
figure 3. Harnesses shall be specified in the
3.28.8 Maintainability. The propeller and
model specification.
control assemblies shall provide for simple
3.31 Balance.
adjustment, ready accessibility, and adequate
3.31.1 Blade. Prior to painting, all blades
field cleaning procedures.
shall be balanced against a master balance
3.28.9 Reliability.  The propeller control
which has ben approved by the procuring ac-
system shall be designed for inherent reliabil-
tivity. The blade shall balance horizontally
ity. The system shall be designed to prevent
and vertically at any two blade angles 90 de-
propeller overspeeds beyond limits specified in
grees apart.  The rotation of the blade caused
the model specification. Either manual or
by horizontal out-of-balance shall be stopped or
automatic safety features may be provided to
reversed by an opposite moment determined as
insure the foregoing reliability.
the weight of the blade times an eccentricity of
3.28.10 Failure analysis. A failure analysis
0.002 inch except that a moment of 0.10 pound-
shall be submitted to the procuring activity for
inch minimum shall be used. The rotation of
review prior to initiation of the qualification
the blade caused by vertical out-of-balance shall
be stopped or reversed by an opposite moment
3.28.11 Stress analysis. A stress analysis of
determined as the weight of the blade times an
all important propeller components, with par-
eccentricity of 0.004 inch except that a moment
ticular emphasis given to vital components as
of 0.20 pound-inch minimum shall be used. It
indicated by the failure analysis shall be sub-
is permissible to use equipment of equivalent
mitted to the procuring activity for review in
accuracy in which the unbalance is determined
conjunction with the failure analysis. The
with the blade centerline located in either a
stress analysis shall include prediction of the
horizontal or vertical position, Where balanc-
magnitude of steady stresses (or loads) and
ing equipment other than knife edges is used,
prediction of the magnitude and frequency of
the unbalanced moment specified above may be
the vibratory stresses (or loads).
applied as scale rending deviations from the
3.29 Component mounting. Components
specified master moments.
mounted on the nose of a reciprocating engine
shall be specified in the model specification, and Ground adjustable. For correction
these mountings shall conform to the appli-
of horizontal balance in ground adjustable
cable standards listed on Standard AND10152.
blades a concentric hole shall be bored in the

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