1、MILITAFE SPECIFICATION SEXTANT, AIRCRAFT, PERISCOPIC This specification has been approved by the Department of the Air Force an Bubble Sextant Magnesium Alloy; Processes for Corrosion Packaging of Lightweight Aircraft Screw Threads, Standard, Aeronautical Webbing, Textile, Cotton, General Purpose, F
2、ilms, Reflection-Reduc ing, for Glass Protection of Accessories Natural or in Colors Optical FLements Marlding for Shipment and Storage Identification Marking of U. S. Military Sextant - Aircraft, Periscopic Property Air Force-Navy Aeronautical Standard Drawings ANS740 AN5742 AND10398 Watches; Navig
3、ation, Master Watch - Navigational Stop Metals - Definition of Dissimilar PUBLICATIONS Air Force-Navy Aeronautical Bulletins c KO. 143 No. 405 Specifications and Standards; Use of Storage Life - Aeronautical Articles O (Copies of specifications, standards, drawings,and publications required by contr
4、actors in connection with specific procurement functions should be obtained from the procuring activity or as directed by the contracting officer.) 3.1 Component parts.- This specification covers a sextant and a mount for supporting the sextant arid providing a pressurized seal. carrying case and sp
5、ares, shall consist of the following: The sextant, complete with (a) 1 Sextant. (b) 1 carrglng case. (c) 1 cable, electrical connecting. (d) 2 spare lamps. (e) 1 watch clip. 2 Licensed by Information Handling Services3.2 Materials.- 3.2.1 Metals.- Metals shall be of the corrosion-resistant Qpe or sh
6、all be suitably protxto resist corrosion during normal service life. 3.2.2 Dissimilar metals.- Dissimilar metais, as defined by Drawing AND10398, 3.2.3 3.2.h shall not be used in intimate contact di .d shall lie in the same or parallel vertical plane as the line of sight of the exig viewing prism. 3
7、.3.1.4.U 3.3.1.4.12 The exit pupil shall be not less than 4.5 millimetekS. Magnification of the optical system for viewing the true heading scale shall be at least two-power with adjustable f0cu.s. parallax exists between the scale and cross hair images. heading scale shall be visible in the eyepiec
8、e at all times. any evidence of stskiness or erratic behavior of the bubble during any test in this specification shall be considered cause for rejection. The design shall be such that no At least 25 degrees of the.true Any loose particles in the bubble cell or 3.3.1.4.13 Foreign particles (bubble).
9、- 3.3.1.4.4 Foreign particles (field of view).- Every effort shall be made to keep foreign Darticles in the field of view to a minimum. The maxilnum mber of foreign particles permitted in the field of view shall be detelmined as follows: Scanning the field of view, any particle larger than 0.004 sha
10、ll be cause for rejection. and the count weighed as follows: Particles over 0.001, count as 10 Particles 0.0003 to 0.01, count as 5 Particles under 0.0003, .count as 2.5 The remaining particles are to be counted Particle size may be estimated by comparison to the etched reticle lines which are 0.000
11、8 wide. In the center zone of the field of dew, defined as a circle of 5 degrees true field, the total weighed count of the particles shall not exceed 5. view, the outer zone, shall not have particles with a weighed count exceeding 30. center zone may be approximated by comparison to the entire fiel
12、d of view which is 15 degrees true field. The optical system of the sextant shall contain horizontal and vertical cross hairs centered in the line of sight to facilitate collimation and the reading of true heading. The cross hairs, bubble image, star image, and scale image shall aU have a common foc
13、d plane, The cross hairs shall be visible and distinct when subjected to the artificial lighting of the bubble cell. 10 degrees below the horizontal (zero) to 2 degrees above 90 degrees altitude. altitude shall be indicated on a drum-type counter with one complete revolution of the operating knob in
14、dicating approicimately 5 degrees change in altitude. 3.3.1.6.1 Altitude counter.- An altitude counter mechanism shali be incorporated. The counter shall be so located that it can be read from the right side of the sextant. The counter and averagjng windows shall be located close together and so ill
15、uminated that they may be read sbptaneously. 3.3.1.6.2 Counter range.- The counter shall Indicate altitudes throughout the effective range o? not less than -10 degrees to +92 degrees. provided to prevent damage to the sextant, or to prevent disengagement of the operating parts when the operating kno
16、b is rotated in either direction beyond the operating range of the sextant. stops imposes no pressure between applicable operating parts of the sextant mechanism other than the nonnal pressure existing when the stops are disengaged. The remainder of the field of The 3.3.1.5 Cross hairs.- . 3.3.1.6 A
17、ltitude range.- The sextant shall be capable or measuring altitudes from The Rugged stops shall be The design of the stops shall be such that forcible engagement of the Licensed by Information Handling ServicesMIL-S-5807C 66 9999906 0125177 b 3.3.1-6.3 Degree indicators.- The counter shall consist o
18、f three adjacent drums. The first two drums shall contain numerals from O through 9, with 8 height of approxi- mately 5/32 inch. black. The numerals on the first two drums shall indicate altitude in degrees. minutes of altitude from O through 55. The height of these numerals shall be 3/32 inch. Grad
19、uation marks for each minute of altitude shall also appear on the third drum. graduation marks for each minute of altitude shall be approxbately 3/64 inch in length, with each consecutive !hninute graduation mark approximately 5/64 inch in length, and both marks shall not exceed 0.005 inch in width.
20、 The numerals and markings on the drums shall be of durable dull 3.3.1.6.4 Mimte indicator.- The third drum shall contain numerals for each 5 The 3.3.1.6.5 Index line,- An index line engraved in durable dull white of l/h-inch length and 0.01-inch width shall be vertically centered on the counter cov
21、er glass over the minute indicator, the cover glass in turn centered with respect to the counter drums. The index Une shall be so situated to afford rapid alinement of the degree and minute values for accurate altitude reading. Filters and shade glasses.- Suitable filters shall be provided and shall
22、 have a visible light transmission through a range of approhately 0.01 percent to 85.0 percent, secondary images or deviation in excess of 3 minutes of arc in horizontal plane or 30 seconds of altitude in a vertical plane. 3.3.1.7 Introduction of the shade glass into the line of sight shall not prod
23、uce 3.3.1.8 Sextant illumination.- The sextant shall contain adequate provisions to illuminate the watch, altitude counters, bubble, and true heading scale. furnished in accordance with Standard MS28011, shall be connected in parallel, and shall be controlled by a toggle switch on the mount. The ill
24、umination from these lamps shall cause no glare in the field of view, of reducing bubble illumination to the point which permits taking observation on second magnitude stars. sextant to receive power from the mount via the connecting cable. The receptacle shall be constructed of 75S-T6 aluminum in a
25、ccordance with Specification a-A-277 or CQ-A-282. The true heading scale shall be illuminated to permit adequate visibility when taking observations on secondmagnitude stars. adequately illuminated for any combination of outside bright daylight and inside dim aircraft illumination levels. The lamps,
26、 The bubble chamber lamp shall also be The rheostat shall be capable A receptacle as shown on Standard 28011 shall be installed on the controlled by a rheostat which does not contain an off-on mitch. The bubble and true heading scale shall be 3.3.1.9 Connecting cable.- The sextant shall be provided
27、with a suitable con- necting cable with connector piugs on both ends in accordance with Standard MS28011. suitable for securely holding the AN5740 or AN5742 watch, shall be so positioned on the sextant proper as to allow the watch face to be read with the eye in line with the eyepiece position. The
28、watch shall be illuminated to permit adequate readability. Variable time averager (VTA).- The variable time averager shall be designed to continuously average sextant altitude settings, and shall give the average altitude and half the elapsed time when used over anytime interval from 30 seconds to 2
29、.minutes. The averager shall be so constructed that no parts wiU work loose in service and shall be so built to withstand the strains, jars, vibrations, and other conditions incident to shipping, storage, installation, and service, without failure. reduced to a minimum. . 3.3.1.10 Watch clips.- A wa
30、tch clip permanently fastened to the sextant, 3.3.1.n Backlash shall be 3.3.1.11.1 Dust protection.- The averager shall be enclosed Fn a dustproof housing. 6 Licensed by Information Handling ServicesMIL-S-5807C bb 979970b 0125178 MIL-S-S807C( ASG) 3.3.1.ii.2 Winding lever.- The winding lever shall b
31、e located conveniently for winding the mechanism. altitude averaging indicators to their respective zero.positions. Where a shutter is used in the sgsten, zero setting of the winding lever shall remove the shutter from the line of vision. averager shall be ready for operation. shall not involve forc
32、ed slippage of any part of the averager. Averager zero adjustment.- the averager made ready for its intended usage, it shaU be possible to adjust accurately the zero position af the averager by means of an adjustment screw accessLble either from the outside of the case, or by removing the cover of t
33、he averager Kithout disassembly of the mechanism. One complete turn or less shall be sufficient to set the Approximately 5 seconds after release of the winding lever, the The method of returning indicator to zero position 3.3.3.U.3 After the mechanism has been rewound and 3.3.1.11.4 Half-time dial.-
34、 The diameter of the half-time dial shall be a minimum of 3/4 of an inch. represent 2 seconds of time. identified by numerals. elapsed time to within an accuracy of 5-4 seconds, or 5-2 seconds if read on the half- time dial. over a period of 2 minutes with a maxhura allowable error of 2 seconds per
35、minute. 3.3.1.ii.s Averaging indicator.- An indicator shall be provided which, when returned to its zero position by operation of the sextant control knob upon completion of an observation and prior to rewhding, shall determine the average altitude, as read on the sextant altitude counter, to within
36、 2 minutes of arc after a 2-minute observation without ambiguity witfiin 40 degrees throughout the total sextant altitude range. averaging indicators shall have a background of durable duil black finish. Numerals and reference markings shall be painted white When a revolving disk-type indication is
37、used, a uhite rectaugle approYdmately 1/8 by i/L of an inch shall be used in addition to the durable dull black for the background of the reference markers of the averaging indicator. The index mark on the white rectangle shall be a dull black. Operating button or lever.- A single start-stop button
38、or lever shall start anfi stop theer. The button shall be so located that when an observer holds and sights through the sextant having the averager attached, he may conveniently operate the button with the thumb or one of the first two fingers of the hand not being used to operate the altitude contr
39、ol knob of the sextant. Period of operation.- When the averager is fully wound and ready for operation, the mechanism shall start and continue functioning when the start-stop button is moved through not more than 3/4 full displacement. The button may then be released without affecting the operation
40、of the mechanism. The averager shall continue in operation through a period of 2 minutes seconds and after operating for the maximum period, the averager shall stop automatically. After the averager bas been operating for a period not to exceed 30 seconds, depressing and releasing the button at any
41、time befope the total period has elapsed shall stop the operation. body when the start-stop button is depressed to stop operation, or when the cycle of operation of the averaging device is complete. Within the period of 2 seconds of the end of the averagercycle, the averager shall actuate the shutte
42、r mechanism It shall be graduated into 60 equal divisions, each division to Every fifth graduation shall be a major graduation, The nmeds shall read from O to 55. The dial shall indicate The timing mechanism shall drive the half-time dial to indicate elapsed time 3.3.1.ll.6 Dial marking.- The markin
43、gs of the half-time dial and the altitude 3.3.1.11.7 3.3.i.U.8 33.l.ii.8.1 A shutter shall automatically intercept the light from the observed 7 Licensed by Information Handling ServicesMIL-S-5807C bb 7797706 0125177 T W 3.3.1.11.9 3.3.1.11.10 Windows.- Suitable plastic nindows shall cover both the
44、half-time :Range.- The averager shall be capable of averaging a series of observations extenping over the ful sextant altitude rangesKithout limit stops. dial and the averaging indicators. An index line 0.01 inch Kide shall be vertically centered on the window with respect to the zero position of th
45、e averaging indicators and half-time dial. be durable duXi. black, while that portion of the line extending over the half-time dial shai be durable dull white. me guard.- eye guard to protec%.the eye and to exclude light. The eye gua2d shall be so designed that it may be readily adjusted without too
46、ls for use with either eye and shall be free to rotate under service conditions. A positive means of attaching the rubber eye guard shall be provided. Cementing alone shall not be considered adequate. 3.3.1.i.12 Averager instruction plate.- An instruction plate carrging brief instructions for the op
47、eration of the averager shall be placed on its outside housing. The instructions on the plate shall be subject to the appmval of the procuring activity. 3.3.1.12 Moisture indicator.- Visible silica gel indicators shall be provided in the sealed tube and case to indicate the presence of moisture. pro
48、vided shall be in accordance with Specification MIL-D-3716, type IV, group H. mount shaii be designed and constructed to receive the periscopic tube of thi? sextant and shall allow the sextant to be positioned iiUpii for sighting, and oDomn when the sextant is not in use. The sextant shall be capabl
49、e of being removed from the mount. Provisions for tilting the sextant proper at least lb-1/2 degrees from the vertical in any direction shall be contained in the mount. When mounted on a flat surface, no part of the mount shall touch the mounting surface at full tilt. Pressure seal.- seal the opening in the aircraft skin or astro siqhting window uith a flush seal when the sextant is in the “Down“ position. lock or a series of positive releasing devices to require interrupted motions in removing the sextant from the mount. when the sextant is lowered from the Ylpfi or operatin
