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MIL-P-26366A
checked through 5 pitch change cycle-s for
minutes. The rotational speed shall be reduced
proper operation. Upon completion of the 15-
to zero, during which time the propeller shall be
day test, the propeller shall be dried without
placed in the air start position by the time the
forced convection for 12 hours in air at less than
rotation reaches zero. The ambient tempera-
70 F with not less than 15 percent relative
ture shall be reduced to 65F at the specified
humidity. At the conclusion of this period,
altitude as rapidly as practicable. As soon as
four over-voltage power supply transients in ac-
this temperature and altitude condition has been
cordance with Standard MIL-STD-704 shall be
reached, rotation of the propeller shaft shall be
applied. Operation of the propeller shall be
started and increased to takeoff rpm. The pitch
checked at normal input voltages, for normal
change sequence noted above shall be followed
operation. The propeller shall be disassembled
once every 80 minutes during an 8-hour con-
and inspected.  No corrosion or other defects
tinuous run at the specified altitude and am-
shall be present that affect the function or struc-
bient temperature.  After each sequence of
tural strength of the propeller.
pitch change, the rate of pitch change at 25
propeller rpm overspeed and underspend at the
high and low beta angle limits shall be deter-
mined. The ice control system shall be subjected
to operation at the specified altitude without
current flow. A determination of the effect of
current flow shall also be performed, The wear
rate of the brushes and rings shall be such as
to indicate a total wear life compatible with the
desired propeller overhaul period of 1,500
hours. The following data shall be recorded at
sea level and altitude conditions, as applicable:
Altitude
Ambient temperature
Rotational speed of propeller
4.6.2.7 Sand and dust. The propeller shall
Feather motor temperature
be installed in a test chamber so that the air
Reference motor temperature
stream will strike the forward face of the as-
Governor temperature
semlly at a velocity of 100 feet per minute. The
Sump oil temperature
air shall carry sand and dust at a concentration
Power unit temperature
of l.50.4 grams per cubic foot. The sand and
Feather motor current. and voltage
dust used shall consist of more than 90 percent
Blade angle movement during pitch change
S i o2, shall be angular in structure, and shall
Sump pressure
screen as follows:
Degree of oil aeration
100-mesh screen US Standard Sieve Series
Beta high and low angle
passes 100 percent.
Mechanical reference on-speed
140-mesh screen US Standard Sieve Series
Electrical reference on-speed
passes 982 percent.
Rate of pitch change at 25 rpm underspeed
200-mesh screen US Standard Sieve Series
Rate of pitch change at 25 rpm overspeed
passes 902 percent.
Centrifugal switch operating rpm
325-mesh screen US Standard Sieve Series
This test shall be accomplished five separate
passes  752  percent.
times.
The temperature of the circulating air shall be
4.6.2.6 Humidity. The propeller, including
controlled as follows:
the ice control system, shall be subjected to an
atmosphere of clear water vapor under cycle
conditions specified as follows for a period of
15 days. After 12 hours, the propeller shall be
41

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