MIL-P-50307( MU)
v i b r a t i o n i n e a c h p l a n e , t h e a r m ( A r m 1 0 5 4 7 4 7 3 ) s h a l l b e i n a s t o w e d P o s i-
tion for one half hour and in an operating position for
the remaining
half hour. Record throughout the first hour of vibration in each plane
all predominant resonant frequencies exhibited by the projector and n o t e
Upon completion of the first hour
the position of the arm at that time.
o f vibration in each plane, select the
four most prominent resonant f r e -
quencies of all those recorded regardless of the
position of the arm.
Remove the reticle lamp and during the remaining one hour vibration in
each plane, vibrate the projector for not less than 15 minutes at each one
of the four resonant frequencies previously selected with the arm in the
position noted when the resonant frequency was first recorded. Upon com-
pletion of the entire vibration test (of two hours in each plane for a total
o f six hours), the projector shall be examined as specified in 4 . 6 . 6 . 6
with reticle lamp 10547031 reinserted.
4 . 6 . 4 . 2 V i b r a t i o n B . - Perform this test in compliance with require-
m e n t s of 3.7.1 and 3.7.l.2 ,procedures herein and in 4.6.4 with
the light in-
Prior to
tensity set f o r
optimum viewing of the projected reticle image.
vibration, the geometric center of the projected reticle image shall be
made coincident to the intersection of a crosshair and this intersection
shall be located at the center of a target's five mil radius circle. The
filament selector switch shall be in one "ON" position for half the vibra-
tion period and in an alternate O N position for the remaining half.
Throughout vibration, the
observer shall locate his eye eight to ten inches
from the beamsplitter in the direction of the projector lamp housing t o
verify that no flicker occurs in the projected reticle image and that the
coincidence established herein remains within the circumference of the
t e n m i l t a r g e t c i r c l e . Upon completion of the entire Vibration test, the
subsequent to vibration examination specified in 4.6.6.6 shall be per-
formed.
4.6.5 General.
".
4 . 6 . 5 . 1 S e a l i n g . - This test
shall be performed prior to the humidity
-
test 4.6.3 - when a humidity test is required (see 4-4) utilizing test
equipment conforming to 4.5. Housing 10547482 shall be internally
pressurized with dry nitrogen gas to the
pounds-per-square-inch gage
pressure (psig) in 3.7.11 for not less than two hours. Throughout this
period, no pressure drop greater than the limit specified in 3.7.11 shall
be evident. U p o n c o m p l e t i o n o f t h i s t e s t , f l u s h t h e h o u s i n g w i t h d r y
nitrogen gas through a regulator to prevent excessive internal pressure
during flushing. Utilize a dew point tester and continue flushing until
the gas bled from the housing exhibits a dew point at least as low as -25°F
w i t h a n i n t e r n a l p r e s s u r e o f b e t w e e n 0 . 1 0 a n d 0 . 2 5 p s i g . Housing 10547482
shall then be sealed.
4.6.5.2 Interior atmosPhere.- This test shall utilize the procedure
i n 4.6.5.1 except that the examination previously performed to d e t e c t
ex-
cessive loss of pressure need not be repeated. this examination shall
verify compliance with 3. 7.12 and be performed subsequent to all tests and
examinations of 4.6 except 4.6.5.6.
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