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MIL-P-26366A
above test shall be conducted five separate
4.6.2 Environmental tests (see 6.6).
4.6.2.1 Test conditions.
times, with a teardown inspection after each
test sufficient to determine that the propeller,
4.6.2.1.1 Test apparatus. The environmen-
including the ice-control system, has not been
tal test of the propeller shall be conducted on
damaged.
apparatus which is capable of meeting the spe-
4.6.2.4 Cold soak. The propeller assembly
cific test conditions. Where applicable, the test
apparatus shall be such that the test propeller
shall be subjected to a static unfeather test and
a cold start test.
shall not exceed 50 percent of the internal vol-
ume of the test chamber, and the heat source
4.6.2.4.1 Static unfeather and cold start test.
shall be so located that radiant heat shall not
The assembly shall be rotated at the takeoff rpm
fall directly on the propeller assembly un-
specified in the model specification at an am-
der test. Normal day atmospheric condi-
bient temperature of 70F for 15 minutes, dur-
tions for the propeller operational checks are
ing which time pitch changes shall be made in
satisfactory.
sequence of increase-decrease feather, unfeather,
4.6.2.1.2 Test propeller. The propeller(s)
and reverse. The pitch change sequence shall
used for the environmental tests shall be in ac-
be repeated as often as practicable within the
cordance with the contractor's model specifica-
time limit of 15 minutes. The rotational speed
tion, unless otherwise specified herein. The
shall be reduced to zero, during which time the
propeller shall be completely connected elec-
test assembly shall be placed in the full-feather
trically, mechanically, or hydraulically, which-
position such that a feather shut down is accom-
ever be the case, to permit operation of the
plished as the rotation reaches zero. The
pitch change mechanism throughout its com-
ambient temperature shall be reduced to -65 F
plete range.
as rapidly as practicable and held at this point
4.6.2.1.3 Test data.  Prior to conducting
for an 8-hour soak. The test assembly shall then
any of the tests. specified herein, the propeller
be unfeathered for a minimum of 20 degrees
shall be operated under normal day atmospheric
from the full-feather position while static, by
conditions and a record made of all data neces-
means of the unfeather system in 45 seconds
sary to determine compliance with the con-
without damage to the unfeather system or re-
tractor's model specification. These data shall
lated mechanism.  Immediately after which,
provide the criteria for checking satisfactory
rotation of the propeller shall be started and in-
performance of the test propeller undergoing
creased 275 5 rpm and run at this speed for a
environmental tests. Variation from normal
period of 5 minutes. At ambient temperatures
day atmospheric condition performance shall be
of 70 F and -65 F, the following data shall be
within limits acceptable to the procuring activ-
recorded: Feather motor voltage, feather motor
ity. All necesary test data, if not established
current, ambient temperature time to move
herein, to be recorded and the recording inter-
blades a minimum of 20 degrees from full-
vals shall be acceptable to the Government
feather position, temperature of feather motor
representative.
prior and after unfeather, and blade angle. The
4.6.2.2 Instrumentation. The instrumenta-
above test shall be completed five separate times
tion and techniques used for monitoring the
with a teardowm inspection after each test suffi-
environmental test data shall be sufficient to
cient to determine that no part of the assembly
provide all necessary data for evaluation of the
has been damaged.
test propeller requirements.
4.6.2.5 High altitude. The assembly shall
4.6.2.3 Hot soak. The test propeller shall
be rotated at the takeoff rpm specified in the
o
be exposed initially to an 8-hour soak at 160 F.
model specification at an ambient temperature
sea level pressure. The propeller shall then
of +70F for 15 minutes, during which time,
simulate a start with 130 F convection cooling
pitch changes shall be made in sequences of in-
air and be brought up to takeoff rpm. Fifty
crease, decrease, feather, unfeather, and reverse.
cycles of pitch change operation shall be con-
The pitch change sequence shall be repeated as
ducted at the rate of one cycle per minute. The
often as practicable within the time limit of 15
40

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