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MIL-P-26366A Endurance run. A 20-hour endur- Propeller reassembly. After instru-
mentation, the propeller shall be reasembled in
ance run shall be conducted on the propeller in-
accordance with the test provisions required in
cluding spinner, cuffs, and ice control equip-
ment. During the run the blade angle shall be
set at that angle at which the propeller absorbs Vibratory stress survey. A vibra-
normal rated actual static sea level horsepower
tory stress survey of the propeller shall be con-
at normal rated rpm.  The propeller shall be
ducted on a whirl stand to determine the stress
run at 150 percent of the maximum rated horse-
characteristics of the hub find blade and the
power of the propeller.
flutter characteristics of the blade, The data Overspeed run. A l-hour over-
obtained by this survey shall be used in deter-
speed run shall be conducted on the propeller in-
mining the test operational limitations for sub-
cluding spinner, cuffs, and ice control equip-
sequent testing of the propeller on the whirl
ment. During the run, the blade angle shall
rig. Blade angle settings for the test shall be
be set at that angle at which the propeller
selected so that, if flutter is present, a flutter
absorbs at least normal rated nctual static sea
boundary curve can be determined for the
level horsepower at 120 percent of the maximum
propeller. This vibratory stress survey may
rated propeller rpm.
be conducted simultaneously with the calibra- Test condition. If not previously
tion test of 4.5.l.6 Stress limits shall be sup-
approved, the provisions of shall apply
plied to the approved testing activity prior to
only in the event that the vibratory stress in-
structural proof testing as specified in
strumentation required for monitoring the
The data shall be prepared substantially in
stress conditions of the propeller during the
accordance with figures 8 and 9.
overspeed run is susceptible to damage by those Calibration test. The procedure dur-
assembly components specified.
ing the propeller calibration shall be such as to Alternate test. When either of the
establish the sea level static performance char-
conditions of or are approved
acteristics of the complete propeller. The
for component alternate testing, a l-hour run
propeller shall be calibrated at various rota-
shall be conducted on those specified components
tional speeds up to 120 percent of the maximum
mounted on a propeller assembly with stub
rated speed of the propeller as specified in the
blades at 120 percent. of maximum rated pro-
model specification, in increments of not more
peller rpm.
than 5-degree settings of the blade angle over Teardown inspection. After comple-
the range specified in the test program. Data
tion of the testing specified in,,
shall be recorded for each angle at increments, and, the propeller and com-
of rpm as specified in The blade angle
ponents shall be completely disassembled for ex-
absorbing minimum power shall be determined
amination of all parts and measured as neces-
and recorded. Blade deflect ion data shun be
sary to disclose excessively worn, distorted, or
recorded during the calibration runs. The in-
weakened parts. These measurements shall be
crements of rpm at which data are recorded
compared with the data recorded in and
shall be reduced to obtain more detailed infor-
the contractor's drawing dimensions and toler-
mation in the suspected high stress conditions.
ances, Photographic records shall be made of
Curves shall be drawn showing corrected horse-
power and thrust at various speeds for each
failures, wear, and other unusual conditions.
blade angle from log data obtained during the
At the option of the procuring activity, periodic
test. The estimated blocking factor attribut-
teardown inspection during specific, test will be
able to the test rig shall be noted on the curves.
Figures 10 and 11 are typical curves. The Propeller reassembly. After satis-
whirl stand calibration test observed log data
factory completion of all the previous tests and
format shall be prepared substantially in ac-
inspections, the propeller shall be reassembled
cordance with figures 12 and 13, as applicable.
to include all necessary control subassemblies for Structuural proof tests.
conducting an overspeed feather test.

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