MIL-DTL-27188C
scale and friction error test shall be conducted. The errors shall not exceed the tolerances specified in
table III. This test may be conducted concurrently with the low temperature exposure test.
4.5.15 Low temperature exposure. The indicator shall be subjected to a temperature of
-65 °C ± 2 °C for a period of 48 hours. While at this temperature, the indicator shall be operated
to ensure that the pointer moves over the entire scale range without exhibiting sticky or erratic
characteristics. The temperature shall then be raised to -55 °C ± 2 °C and held for a period of
24 hours. While at this temperature, the indicator shall be subjected to the scale error and friction
test, except that in every case, the indicator shall not require more than 4 seconds to come within
the tolerances of table III. The scale error and friction shall not exceed the tolerances specified in
table III. All parts of the indicator shall then be maintained at room temperature for a period of
not less than 4 hours and the indicator shall again be subjected to the scale error and friction test.
The scale errors shall not exceed the tolerances specified in table III. There shall be no damage or
deterioration that will affect subsequent operation.
4.5.16 High temperature exposure. The indicator shall be subjected to a temperature of
71 °C for a period of 24 hours and then tested at this temperature for scale errors as specified in
4.5.4. The scale error tolerances and friction shall not exceed the tolerances specified in table III.
All parts of the indicator shall then be maintained at room temperature for a period of not less
than 4 hours and the indicator shall again be subjected to the scale error and friction test. The
scale errors observed shall not exceed the tolerances specified in table III. There shall be no
damage or deterioration that might affect subsequent operation.
4.5.17 Thermal shock. The indicator shall be subjected to 8 cycles of immersion in water at
a temperature of 85 °C ± 2 °C and then in water at a temperature of 5 °C ± 2 °C without evidence of
moisture penetration or damage to the coating or the case. The length of time for each immersion
shall be 30 minutes with not more than 5 seconds between immersions. After eight continuous
cycles have been completed, the indicator shall be subjected to the test specified in 4.5.6.
4.5.18 Salt fog. The indicator shall be subjected to a salt fog test for a period of 48 hours
in accordance with MIL-STD-810, Method 509, Procedure I. There shall be no evidence of
external corrosion or deterioration that might affect subsequent operation. The scale errors after
this test shall not exceed the tolerances specified for room temperature scale error.
4.5.19 Radio noise interference. The indicator shall be subjected to a radio noise
interference test in accordance with MIL-STD-461 except that the frequency range for radiated
noise shall be within 0.15 megacycle to 150 megacycles. During this test, the synchro shall be
operated at 30 revolutions per minute (rpm) ± 5 rpm.
4.5.20 Unit torque gradient. The indicator shall be connected to the master transmitter
synchro and the master transmitter locked in the electrical zero position. The synchro rotors shall
then be energized with rated voltage and frequency ±1 percent. Weights shall be applied to a
torque pulley that has been positioned on the rotor shaft to rotate the shaft in a counter clockwise
direction through an angle of 5 degrees of arc. The torque tending to return the shaft to its
original position shall be computed and shall be no less than 2,000 milligram-millimeters per
degree of displacement.
15
For Parts Inquires call Parts Hangar, Inc (727) 493-0744
© Copyright 2015 Integrated Publishing, Inc.
A Service Disabled Veteran Owned Small Business