SINCE OUR DRIFT SIGHT PROJECT ENGINEER'S TRIP TO THE RANCH ON JULY 9, WE HAVE INITIATED ACTION TO CORRECT A NUMBER OF PROBLEMS IN THE DRIFT SIGHT.

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP89B00487R000300640011-1
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 2
• Document Creation Date: December 22, 2016
• Document Release Date: August 9, 2011
• Sequence Number: 11
• Publication Date: August 28, 1956
• Content Type: LETTER

Sanitized Copy Approved for Release 2011/08/09: CIA-RDP89B00487R000300640011-1
August 28, 195'
Since our Drift Sight Project Engineer's trip to the Ranch on July 9,
we have initiated action to correct a number of problems in the Drift
Sight. These are problems which have shown up through use of the
Drift Sight in actual practice. A number of these things have already
been covered in his summary contained in his report dated July 18,
entitled "Trip to Projector Sight July 9-11."
Prisms: Two Drift Sights which had been returned from the field and
are now in our hands have had the scanning prism edge sharpened to
eliminate the blurry line caused by this prism edge in the field of
vision. Upon completion of this work, the units will be returned to
the field through EFM, and two field units will be requested in return
(on a rotation basis) for sharpening of the prism edge. We will be
dependent upon EFM to keep sending us Drift Sights for this work as
he receives corrected Drift Sights from us. I covered this matter in
conversation with EFM on august 23, 1956.
Reticle Pattern: At the same time as the prisms are bing corrected, the
reticle will be changed to furnish another pattern. Use in the field
has shown the advisability of furnishing a broken center mark to define
optical axis of the Drift Sight.
Input Collars: Modified input collars for use at the head of the Drift
Sight to prevent flexible shaft bending have been designed and a set of
two furnished to at Hycon. These particdar parts have been
furnished to Hycon since they are maintaining the Drift Sight and are
in a position and have the facilities for removing the old input collar
and installing the new.
Plastic Lenses: A quantity of ten extra plastic lenses is being produced
now for replacement of the scratched plastic lenses in the Drift Sight
eyepieces. To date we have been able to determine that Detachment A
requires four such plastic lenses; Detachment B's exact needs are unknown
at this moment although two plastic lenses were shipped to them prior to
departure, and of the installations currently existant at the Ranch site,
only four plastic lenses are required there. On a trip during the wehk
of August 20 to the Ranch, an examination of the plastic lenses revealed:
Article 343. The yellow filter had been removed. In the process
of reassembling the retaining ring, it had evidently been over-tightened
to the extent that the two plastic lenses of the eyepiece were so squeezed
together that the air space normally existing between their vertices was
eliminated and the vertices contacted and pressed together. At the point
SO-lee C
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George August 28, 1956
of contact of the vertices, a flat spot exists causing variation of
magnification in this area which is approximately 112" in diameter.
This explains the complaint from the sextant people on 'variable
magnification.'
Article 344. The yellow filter had been removed from the eyepiece.
The exposed surface of the plastic lens was deeply scored with concentric
scratches. In addition, the vertices of the lenses have been forced into
contact causing a flat spot as described for Article 343. The concentric
scratches, I found, were due to the first attempt by LAC people in pro-
viding a Drift scale. The first scale was made of plastic which warped
and its scored lines rubbed against the plastic eyepiece causing the
concentric scratches. Where plastic lens vertices have been squeezed
together, it will be necessary to replace both plastic lenses. The plastic
lenses which will be supplied 14 -as replacements will also be furnished with
a special arrangement for separating the two lenses to a sufficient degree
that over-tightening of the retainer ring and consequent plastic deformation
of the lenses will prevent them from contacting.
Clear Filter: A quantity of 20 clear filters plus an additional amount for
spares are being manufactured of CR-39 plastic (high abrasion resistant
plastic) to take the place of the yellow filters which have been removed
from all Drift Sights. This clear plastic will protect the plastic lens
from further scratching due to cleaning or other causes. It should be
emphasized here that the placement of the clear filter and the replacement
of the plastic lenses are to be done only by qualified maintenance per-
sonnel who have been trained in this job by Peco.
Drift Sight Scale: Following the suggestion of EFM, we have manufactured
one movable Drift scale which is placed over the eyepiece. This unit is to
be shipped to the field during the week of September 3. Further tests on
this unit plus the two units that EFM has made will determine whether field
modification kits will be provided for all Drift Sights. A. conversation
with EFM has indicated that such a decision should be forthcoming from his
test people the week of September 10.
Desiccation: A service bulletin concerning the desiccation of the Drift
Sight was prepared and issued to all concerned in the month of July. A
copy of this bulletin is attached for your information. (As part of this
desiccation problem, the service bulletin was also issued for the Tracking
Camera.)
The above information should serve to bring you up-to-date on the action we
have taken to overcome some of the adverse comments we have received from
various sources on the Drift Sight. An additional report will be forth-
coming from EFM on additional tests that have been made concerning accuracy
of the Tracker since the auto pilot is still not functioning perfectly.
Any such information should be corrected where possible for auto pilot
TWM%dmg
cc: EFN
WA S
Sanitized Copy Approved for Release 2011/08/09: CIA-RDP89B00487R000300640011-1