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MIL-P-26366A
Feathering and unfeathering: Expo-
quired vibratory stress survey of the aircraft
(e)
sure shall be under various conditions
test shall be as specified in 2.5.3.2.
4.7.3. Vibratory stress survey.
of speed and power. Test duration
4.7.3.1 Ground survey. A ground vibration
shall be for a minimum of 500 cycles
stress survey of the propeller shall be conducted
of which no less than 100 cycles shall
on all nacelles of the aircraft to determine the
be accomplished at maximum condi-
tion of propeller operation.
stress characteristics of the propeller when
operated in the aircraft environment: The fol-
( f )  Negative torque signal: Exposure
lowing is provided as a guide. For four-engine
shall be under those conditions nor-
mally expected to be encountered in
aircraft, the propeller shall be initially installed
at the number three nacelle position and shall
service. The test shall be for a mini-
mum of 1,000 cycles.
remain at this position until all specified testing
conditions have been completed. The same pro-
(g)  Ice control system: The propeller
cedure shall apply for two-engine aircraft with
electrical ice control system compo-
initial installation at the number two nacelle
nents, including brushes and rings,
position. The ground survey shall be conducted
shall be subjected to a 500-hour dura-
bility test at the temperature-altitude
utilizing four strain gage groups. A survey
conditions specified in the model
shall be made of ground operation which shall
specification.
consist of obtaining all necessary stress meas-
4.6.4.7  Teardown inspection. After comple-
urements from three designated strain gage
tion of the tests, the  propeller components
groups during the performance of conditions 1
which underwent test shall be completely dis-
through 12 and 66 through 71 as specified on
assembled and inspected in accordance with
figures 19a, 19b, and 20. After completion of
4.5.1.9.
the above specified ground survey with the three
4 . 7 Aircraft test.
designated strain gage groups, the propeller
4.7.1 Test conditions.
shall be resurveyed utilizing the fourth strain
4.7.1.l Test apparatus. The following test
gage group, which shall be a composite group-
apparatus shall apply for all aircraft tests as
ing determined by the analysis of the three
applicable.
designated strain gage groups, to obtain stress
4.7.1.1.l Automatic recording equipment.
measurements at the same conditions when in-
Automatic recording equipment shall be used
stalled at the number two, one, and four nacelle
as specified in 4.5.2.1.1.2.
positions, in that order. An additional survey
4.7.1.1.2 Aircraft. The aircraft test of the
shall be accomplished, if the above representa-
propeller shall be conducted on the prototype or
tive conditions indicate a requirement. Appli-
first production aircraft which shall provide
cable vibratory stress survey attenuator set-
suitable means for testing the propeller. In
tings, oscillograph reduction and condition log
the case of a multiengined aircraft application,
data formats shall be prepared substantially in
the test shall be conducted on all nacelles.
accordance with figures 8, 9, and 21 through 25.
4.7.1.2 Test propeller. The propeller(s)
used for all the aircraft tests shall be in accord-
4.7.3.2 Flight survey. A flight vibratory
ance with the model specification except for
stress survey of the propeller shall be conducted
modification required for instrumentation.
on all nacelles of the aircraft to determine the
For multiengined aircraft all nacelles shall in-
stress characteristics of the propeller when
corporate identical models of the propeller.
operated in the aircraft environment. The fol-
4.7.1.3 Test data. During the aircraft test
lowing is provided as a guide. For four-engine
all pertinent test data provisions of 4.5.2.1.3
aircraft, the propeller shall be initially installed
shall be applicable.  In addition, recordings
at the number three nacelle position and shall
shall be made of the indicated air speed in
remain at this position until all specified testing
knots, altitude in feet, and the rate of climb in
conditions have been completed. The same pro-
feet per minute.
4.7.2 Instrumentation. The instrumentat-
cedure shall apply for two-engine aircraft with
ion and techniques used for monitoring the re-
initial installation at the number two nacelle
44

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