MIL-PRF-17850B
4.6 Performance and Environmental test.
4.6.1 Compass accuracy test. The accuracy of the compass shall be checked at 0, 90,
180, and 270 degrees magnetic. The compass error shall not be greater than 2 degrees when
tested against known surveyed targets. Any error 2 degrees or less shall constitute acceptance of
the test.
4.6.2 Freedom of rotation test. The compass shall be placed in a level position and
rotated 360 degrees and then tilted 15 degrees and totaled 360 degrees. The compass shall rotate
and operate freely in all positions. If there is no binding of the compass after this test, this shall
constitute acceptance.
4.6.3 Leakage test. The compass shall be submerged below the surface of the water for
period of 30 minutes. After 30 minutes, remove the compass from the water and inspect. If there
are no signs of leakage after this test, this shall constitute acceptance.
4.6.4 Floatation test. The compass shall be placed in distilled water at a temperature of
65 °F to 85 °F. If any portion of the compass remains above the surface of the water for greater
than 1 minute, this shall constitute acceptance.
4.6.5 Drop test. The compass shall be dropped a distance of five feet onto a hard surface
on the back, face, and side. The compass shall then be visually inspected for damage. If there is
no evidence of damage this shall constitute acceptance of the compass. Tests 4.6.1 through 4.6.3
and 4.6.7 shall be accomplished after this test.
4.6.6 High and low temperature operation test. The compass shall be raised to a
temperature of +140 °F for a period of 4 hours. The compass shall then be stabilized at ambient
temperature and then lowered to -40 °F for a period of 4 hours. Throughout the range from
-40 °F to +140 °F, the compass shall remain in conformance with 3.4.2 and 3.5.5. Conformance
with 3.4.2 and 3.5.5, shall constitute acceptance of the compass. Tests 4.6.1 through 4.6.5 and
4.6.7 shall be accomplished after this test.
4.6.7 Resistance to static charge test. Secure the compass on a horizontal surface with
the compass aligned with the north-south axis. Briskly rub the surface of the compass with a
clean, dry cotton rag for a period of 15 seconds. If the compass reads within 2 degrees of north
within 15 seconds after the rubbing operations is completed this shall constitute acceptance of the
compass to meet the static charge requirements of 3.2.
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