MIL-DTL-48557B
depress the mount to the limits of its excursion in both elevation and depression. When at
the limits of excursion, place the inspection aid, 8658940, on the leveling adapter or
observe the elevation reading on the scale of the fixture to confirm that the mount meets the
requirements of 3.7.3.
4.7.4 Elevation plumb travel. This test may be performed in conjunction with 4.7.3.
Mount sighting device, 10549200, to the telescope mounting surface with its line of sight
parallel to the telescope locating keys. Position a wall target with an appropriately labeled
azimuth scale for the distance it is placed from the objective end of the sighting device and
place the vertical line of the wall target in coincidence with the vertical reticle of the
sighting device. While looking through the sighting device at the plumbed reference,
elevate and depress the mount throughout the excursion range. Any deviation of the line of
sight from the plumbed reference shall be within the limits specified in 3.7.4.
4.7.5 Pitch adjustment range. Position the mount as specified in 4.7 and mount
sighting device, 10549200, to the telescope mounting surface with its line of sight parallel
to the telescope locating keys. Assure that the cross level vial bubble is centered (zero
cant). Rotate the pitch adjustment to the limit of its excursion in one direction. When at
the limit of excursion, place the inspection aid, 8658940, on the surface of the sighting
device and measure the pitch angle at the limit. Repeat in the opposite direction. Pitch
elevations at the limit shall meet the requirements of 3.7.5.
4.7.6 Pitch plumb travel. Position the mount as specified in 4.7 and mount sighting
device, 10549200, to the telescope mounting surface with a line of sight parallel to the
telescope locating keys. Assure that the cross level vial bubble is centered (zero cant).
Position a wall target with appropriately labeled azimuth scale for the distance it is placed
from the objective end of the sighting device and place the vertical line of the wall target in
coincidence with the vertical reticle of the sighting device and ensure that it is plumb.
While observing the position of the reticle of the sighting device in relation to the vertical
line of the wall target, rotate the pitch adjustment to the limits of its excursion and observe
any deviation. Any deviation of the line of sight from the plumbed reference shall be
within the limits specified in 3.7.6.
4.7.7 Pitch adjustment backlash. Position the mount as specified in 4.7. Assure
that both of the mount s level vial bubbles are centered. Turn pitch knob at least one
complete turn counter clockwise and then center the elevation level bubble using only a
clockwise motion of the pitch knob without overtravel. Place inspection aid, 8658940, on
the telescope mounting surface, measure the elevation read by the inspection aid and
record. Scribe an index line on the mount casting nearest to the pitch knob. Place an index
pointer on the pitch knob directly opposite the scribed index line. The index pointer may
be held in place mechanically or by the use of commercial putty. Turn pitch knob at least
one half turn clockwise and then return it to the position previously established by the
indices in a counter clockwise motion without overtravel. Place inspection aid on the
telescope mounting surface, measure the elevation read by the inspection aid and compare
with initial reading. The difference between these readings is the backlash and it shall be
within the limits specified in 3.7.7.
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