1、MIL-C-718.8 IO MAY 1951 Supersedfng 29 January i946 AN-C-156 MILITARY SPEGIFICATION COMPASSES, PILOTS STANDBY, INSTALLATION OF This specification was approved by the Departments of the Army, the Navy; and the Air Force for use of procurement services of the respective Departments. 1. SCOPE 1.1 This
2、specification covers the installation of pilots standby compasses. 2. APFXCCABLE-.SPECIFICATIONS 2.1 The following publications, of the issue in effect on date of invitation for bids, shall form a part of this specification to the extent specified herein: 2.1.1 Specifications.- filitary NIL-1-7028 I
3、nstruments and Inlitrument Boards; Aircraft Installation of Air Force-Navy Aeronautical AN-C-106 Compass Swinging; Aircraft AN-3-107 Compasses; Installation of (Copies of this specification and copies of other publications refer.enced.herein gr required for Government procurement, and the Index of M
4、ilitary Aeronautical (AN or MIL) Standards, may be obtained upon application to tihe commanding General, Air Materiel Command, Wright-Patterson Air Force Base, Dayton, Ohio; or the Commanding Officer, U. S. Naval Air Station, Johnsville, Pennsylvania.) 3. REQUIRFJBNTS 3;i General.- The requirements
5、specified in Specification .-1-7028 are appli- cable as requirsments of this specification. 3.1.1 In the event the requirements of this specification and the general specifi- cation conflict, the requirements of this specification shall govern. 3.2 Nonmagnetic Materials.- All materials used in mount
6、ing the compass, such as . brackets, screws, plate nuts, et cetera, shall be of nonmagnetic metal, on a bracket suitably insulated from vibration in some position off the instrument panel. The compass shall be positioned to be easily read by the pilot. through the lubber line and the center of the p
7、ivot are parallel to the longitudinal axis of the airplane. 3.3 Location.- The compass shall be located on the inst-aq panel or positioned 3.3.1 Lubber Line.- The compass shall be so installed that the vertical plan, - Provided by IHSNot for ResaleNo reproduction or networking permitted without lice
8、nse from IHS-,-,-MIL-C-7188 (May 1951) pilotis or copilotis instrument panel, it shall be so positioned that it is in a normal level position when the airplane is in normai flight attitude. 3.3.2 Leveling,- When the compass is installed in a location other than the 3.3.3 Labels,- The compass install
9、ation conforming to this specification shall be clearly labeled with a suitable placard as follows: “TO BE USED AS A STANDBY COMPASS ONLY.“ 3.4 VibraXion Insulation.- The compass mounting shall be vibration insulated in accordance with Specification MIL-1-7028. 3-5 Wiring.- When the Compass is equip
10、ped for individu The changes of compass reading due to magnetic mate- rials and electric currents, specified in this specification, appy only to locations at which the strength of the horizontal component of the earthts magnetic field (airplane re- moved) is 0.18 oersted. When tests are accomplished
11、 at locatias where the strength of the hoAzonta1 component of the earthis fi6ld aiffers from 0.18 oersted, the allowable changes specified herein, shall be corrected as specified in table II of Specification AN-C-107 4.2.7 during the tests. 4.2.8 Records.- Permanent records shall be kept ofall the d
12、ata which are obtained Readings.- All readings on the grbund and in the air shal be taken to the nearest degree. the change shall be recorded with an increase of reading taken as positive and a decrease of reading taken as negative. When noting changes of compass reading, both magnitude and directio
13、n of 4.3 mine compliance with this specification with respect to workmanship, installation, and demagnetization o 4.4 Individual Tests.- Each installation shall be inspected carefully to deter- Sampling Tests.- One prototype, 1 of the first 10 production airplanes of any design, and such additional
14、airplanes as may be specified by the Procuring Service, shall be selected by the inspector for subjection to the tests specified herein. 4.4.1 Effect on Climb and Glide, Ground Swing.- The airplane shall be placed on and east or west heading in an attitude of horizontal flight and in an attitude of
15、5 de- grees tail down. The compass shall be read in both attitudes with no electrical. circuits on. In each attitude the circuits to be tested as specified under tests headed, IIEffect of Variable Circuits“ and “Effect of Continuously Operated Electrical Circuits ,II shall be energized and the compa
16、ss reading noted. exceed 3 degrees. shall be performed with the airplane irr the horizontal flight attitude. The change in the compass reading shall not All remaining tests, with the exception of the Effect of Engine test, 4.4.1.1 This test need not be repeated on other headings. If a nonmagnetic ja
17、ck or dolly is unavailable, one having magnetic materials may be used provided the following re- quirement is met. The jack (or dolly) shall be moved in a circle about the compass in the position in which, and at the distance at which, it would be used to swing the airplane. Such movement of the dol
18、ly shall not cause a change in compass reading greater than 1/2 degree e 4.4.2 Effect of Movable and Removable Magnetic Parts.- placed on an east or west heading on the ground and the change of compass reading shall be noted while each item is moved through the entire range of movement possible. in
19、compass reading shall not exceed 3 degrees; be held stationary at the normal positipn, at the extreme limits of the motion, and at any position where the effect upon the compass is at a maximum, for sufficient time for the compass to settle. The airplane shall be The change During this procedure the
20、 equipment shall Each item shall be tested with all other items in their normal position. - 3 ti :- Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-C-7188 bb = 979990b 0478804 2 m m-c-7188 (May 1951) This test shall include such items as controls
21、, gun turrets, tail hooks, et cetera. For munition, bomb, and torpedo loads and other removable items, the compass reading shall be noted with the equipment in place and removed from the airplane, repeated on a north or south heading. heading on the ground, the engine or engines shall be run at appr
22、oximately 1,500 rpm, and the change in compass deviation noted from that with the engines not running. The change in the compass reading shall not exceed 3 degrees. ing this test. This test shall be 4.4.3 Effect of Ehgine.- The airplane shall be placed on an ezst or west magnetic The battery shall n
23、ot be charging dur- This test shall be repeated on a north or south heading. 4.4.4 Effect of Variable Circuits.- The airplane shall be placed on an east or west magnetic heading on the ground, and the change of compass reading produced by the operation of each direct current electrical circuit, whic
24、h carries a variable current or which intermittently operated during flight, shall be noted. reading shall not exceed 3 degrees. The sum of all individual positive changes due to the effect of variable circuits and the effect of movable and removable magnetic parts shall not exceed 5 degrees for the
25、 compass. The sum of all individual negative changes for the compass shall not exceed 5 degrees. This test shall include such circuits as: Generator circuits, including auxiliary power plants, pitot static tube heaters, cockpit and cabin heaters, galley motors for gun turrets and other equipment, co
26、ckpit and cabin lights, navigation lights, et cetera. the discretion of the inspector. running or, if desired, the generator may be replaced by an external source to produce normal generator output current. The change in the compass grills, inverters and dynamotors for radio and other equipment, Thi
27、s test may be conducted with the engines either running or not running, at The generator circuit test may be made with engines This test shall be repeated on a north or south heading. 4.4.5 gfect of Continuously Operated Electrical Circuits.- The test procedure f variable circuits shall be followed,
28、 except that the tests shall be performed on circuits which draw a steady current. tric circuits operated continuously at all times of operation of the airplane shall not ex- ceed 3 degrees for the compass. not exceed 3 degrees. The sum of all individual positive changes caused by elec- The sum of a
29、ll the negative changes for the compass shall 4.4.6 Effect of Electrical Circuits, Take-off and Landing.- The test procedure of * variable circuits shall be followed, except that the tests shall be run on the circuits for wing flap motors, landing gear and float motors, landing lights, et cetera. Th
30、e change in compass readings shall not exceed 8 degrees. 4.4.7 Effect of Landing Gear.- The effect of landing gear may be tested either on the ground or in flight, at the discretion of the inspector. ing shall not exceed 4 degrees. The change in compass read- 4.4.7.1 Ground Test.- The airplane shall
31、 be supported on 8 north or south mag netic heading by means of suitable jacks or hoists and the compass reading recorded with the landing gear successively in the retracted, lowered, and tben retracted position. This procedure shall be repeated on east or west magnetic headings. The apparatus which
32、 supports the airplane should preferably be nonmagnetic. The airplane may be flown by the automaDic pilot or by re- ference to a directional gyro on a straight level course on an approxidte north magnetic heading with the landing gear retracted. carefully and recorded. The landing gear shall be retr
33、acted and the third compass reading recorded. dure shall be repeated with the airplane on an approximate east, south, and west magnetic heading, and maximum change of compass reading of any heading noted, 4.4.7.2 Flight Test.- The average compass reading shall be estimated This proce- The landing ge
34、ar shall be lowered and the compass read again. 4 6: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-P MIL-C-7188 66 E 77777Ob 0498805 4 M PEL-C-7188 (May 1951) 4.4.8 Uncompensated Deviation.- 4.4.8.1 Ground Swing.- With the airplane placed in an eas
35、t or west-heading, the spread between the maximun positive deviation and the maximum negative deviation, with all equipment in its-horma1 position and all ele.ctrica1 circuits turned on, which are normally operated in flight (engine running with.battery being charged), shall not be more than 24 degr
36、ees for the compass. throughout a complete revolution. The procedure shall be repeated for each 30-degree heading 4.4.8.2 Airswing.- The.airplane shall be in normal flight conditions and the airswing carried out on 12 approhmately evenly spaced magnetic headings. A graph shall be plotted of deviatio
37、n against the magnetic heading from which the deviation at the-30- degree heading shall be taken. tor, The difference between airswing and ground swing shall not exceed 2 degrees. 4.4.9 This test may be conducted at the discretion of the inspec- Compensated Deviation.- The compensator shall be attac
38、hed to the standard test compass and the compass compensated in accordance with Specification ANX-106 with the exception that the alinement of the compass on the panel or mount need not be compen- sated (coefficient IlAIf). The spread between the maximum positive deviation and the maXi- mum negative
39、 deviation shall not exceed 8 degrees for the compass. 4.5 Rejection and Retest.- Rejected installations shall not be resubmitted for inspection without furnishing full particulars concerning previous rejection and measures taken to overcome the defects, 5. PFU3PAFATION FOR D!XtIVERY Not applicable.
40、 6. NOTES 6.1 Intended Use.- This specification is intended to govern the installation of the standby compass in aircraft. 6.2 Definitionfi- 6.2.1 Deviation.- Deviation of an aircraft compass is the difference between the compass heading and the corresponding magnetic heading of the aircraft in whic
41、h it is in- stalled. ing of the aircraft. Deviation is computed by subtracting the compass reading from the magnetic head- NOTICE: When Government drawings, specifications, or-other data are used,for any purpose other than in connection with a definitely related Government procurement ope.ration, th
42、e United States Govern- ment thereby incurs no responsibility nor any obligation.%itsoever; and the fact that the Government may have formulated, furnishe.d, or in any way supplied the said drawings, specifhatiofis, or other data is not to be regarded by implication or otherwise as in any manner lic
43、ensing the holder or any other person or corporation, or convey- ing any rights or permission to manufacture, use, or sell any pat- ented invention that may in any way be related thereto. CUS t odian: Air Force Other interest: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
