1、 MILITARY SPECIFICATION MIL-A-818518 27 Feb 1986 SUPERSEDING 11 Mar 1985 MIL-A-81851A ALTIMETER AAU-31/A This specification is approved for use by all Departments and Agencies of the Department of Defense. 1. SCOPE 1.1 Scope. This specification covers the requirements for a counter- drum-pointer,int
2、egrally lighted, self-contained altimeter (indicator) having a range of -1,000 to 50,000 ft. 1.2 Classification. Two types of altimeters are covered by this specification and differ only in respect to variation in color of the integral white lighting as follows: I. Type AAU-31/A-1 Altimeter (interch
3、angeable with AAU-31/A) - Incorporates “aviation red“ lighting and “blue filtered“ white lighting. II. Type AAU-31/A-2 Altimeter (interchangeable with AAU-31A/A) - Incorporates “aviation red“ 1 ighti ng and “instrument and panel II white 1 i ghti ng. I Beneficial comments (recommendations, additions
4、, deletions) and any pertinent data which may.be of use in improving this document should be addressed to: Commanding Officer, Naval Air Engineering Center, Systems Engineering and Standardization Department (SESD) Code 93, Lakehurst, NJ 08733, by using the self-addressed Standardization Document Im
5、provement Proposal (DD Form 1426) appearing at the end of this document or by letter. 1 i AMSC-N/A FSC-661 O DISTRIBUTION STATEMENT A. Approved for public release; distribution is un1 i mi ted. THIS DOCUMENT CONTAINS 40 - PAGES. Provided by IHSNot for ResaleNo reproduction or networking permitted wi
6、thout license from IHS-,-,-MIL-A-81851B 2. APPLICABLE DOCUMENTS 2.1 Government documents. 2.1.1 Specifications, standards and handbooks. the contract or purchase order, the fol lowing specifications, standards and handbooks of the issue listed in that issue of the Department of Defense Index of Spec
7、ifications and Standards (DODISSI specified in the solicitation, form a part of this specification to the extent specified herein. Unless otherwise specified in MILITARY MIL-P-116 Preservation, Methods of ML-E-5400 Electronic Equipment, Aircraft; General Specification for MIL-C-554 1 Chemical Films
8、for Aluminum and Aluminum Alloys MIL-S-7742 Screw Threads, Standard, Optimum Selected Series; General Specification for MI L-A-8625 Anodic Coatings, for Aluminum Alloys and Aluminum DOD-0- 1 OOO/ 1 Drawings, Engineering and Associated Data MIL-C-14806 MIL-T-18303 MI L-C-25050 Coating, Reflection Red
9、ucing for Instrument Cover Glasses and Lighting Wedges Test Procedures, Production, Acceptance and Life for Aircraft Electronic Equipments; Format for Colors, Aeronautical Lights and Lighting Equipment; General Requirements for MIL-L-25467 Lighting, Integral, Aircraft Instrument; General Specificati
10、on for MIL-C-26482 Connectors, Electric, Circular, Miniature, Quick Di sconnect MIL-L-27160 Lighting, instrument, Integral, White; General Specification for MI L-8-27497 MI L-P-2 1 600 Faint System, Fluorescent, for Aircraft Bearing, Jewel, Sapphire or Ruby Synthetic Application MI L-G-81704 Glass,
11、Aircraft Instruments, Lighting Wedges and Cover 2 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-A-LS1B 66 7779706 0143666 b MIL-A-81851B STANDARDS FEDERAL FED-STD-595 Colors MILITARY MI L-STD- 1 30 Identification Marking of U.S. Military Proper
12、ty MI L-STD- 1 43 Specifications and Standards; Order of Precedence for the Selection of MIL-STD-461 Electromagnetic Interference Characteristics Requirements for Equipment Mai ntai nabi 1 i ty Demonstration MIL-STD-471 MIL-STD-704 Electric Power, Aircraft, Characteristics and Uti 1 ization of MIL-S
13、TD-781 Reliability Tests, Exponential Distribution MIL-STD-794 Parts and Equipment , Procedures for Packaging and Packing of MIL-STD-810 Environmental Test Methods MIL-STD-859 Standard Calibration Table for Aeronautical Pressure Measuring Equipment MS-3113 MS-3114 MS-3 3 549 MS-33558 MS-33649 Connec
14、tor, Electric Solder Type Solder Mounting, Bayonet Coupling Connectors, Receptacle, Electric Solder Type, Jam Nut Mounting, Bayonet Coupling Cases, Aircraft Instrument 2 314 Inch Dial With Sump, Standard Dimensions for Numerals and Letters, Aircraft Instrument Dial, Standard Form of Bosses, Fluid Co
15、nnection, Internal Straight Thread (Copies of specifications, standards, handbooks, drawings and publications required by contractors in connection with specific acquisition functions should be obtained from the contracting activity or as directed by the contracting officer.) 3 Provided by IHSNot fo
16、r ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-A-818518 2.1.2 Other Government documents, drawings and publications. other Government documents, drawings, and publications form a part of this The following specification to the extent specified herein. PUBLICATIONS D
17、epartment of Defense Standardization SD-6 Provisions Governing Qualification (Copies available from: Commanding Officer, Naval Publications and Forms Center, 5801 Tabor Avenue, Philadelphia, PA 19120) 2.2 Order of precedence. this specification and the references cited herein, the text of this speci
18、fication shall take precedence. In the event of a conflict between the text of 3. REQUIREMENTS 3.1 Qualification. The general requirements for qualification are specified in Publication SD-6, Provisions Governing Qualification. The production instruments furnished under the specification shall repre
19、sent a product which has been tested and meets the qualification requirements specified herein under Section 4, Quality Assurance Provisions, and has been listed on or approved for listing on the applicable Qualified Products List. 3.1.1 -f qualification. Retention of qualification consists of perio
20、dic verification of compliance of the product with the requirements of this specification. The manufacturer shall provide a letter of certification of compliance to the activity responsible for the Qualified Products List at intervals of not more than two years. A copy shall also be submitted to the
21、 Naval Air Systems Command, Attention Avionics Division. attest that the qualified altimeter is still available from the listed plant and can be produced in the same plant under the same conditions as when qualified. manufacture of the altimeter shall be reported as required by SD-6, Provisions Gove
22、rning Qualification. The letter shall Any changes in parts, materials, design, or processes for 3.2 Selection of specifications and standards. Specifications and standards for necessary commodities and services not specified herein shall be selected accordi ng to MIL-STD-143. 3.3 Standard general re
23、quirements of MIL-E-5400 Class 2 shall apply. 3.3.1 Non-magnetic materials. Non-magnetic materials shall be used for all parts excerit where magnetic materials are essential. The extent to which magnetic materials ar required shall be reported to the procuring activity. 3.3.2 Protective treatment. W
24、hen materials are used in the construction of the altimeter that are subject to deterioration when exposed to climatic and environmental conditions likely to occur during service life, they shall be protected against such deterioration in a manner that will in no way prevent compl lance with the per
25、formance requirements of the specif i cation. 4 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-A-838SLB 66 m 7777906 O343668 T m MIL-A-81851B The use of any protective coating that will crack, chip or scale with age or extremes of climatic and e
26、nvironmental conditions shall be avoided. 3.3.3 Toxic and corrosive fumes. The materials, as installed in the altimeter and under the conditions sDecified herein, shall not liberate deleterious or corrosive fumes. are used. This shall include.any fungicidal agents that 3.3.4 Aluminum alloy parts. Al
27、uminum alloy.parts shall be covered with an anodic film conforming to MIL-A-8625, except that the dial, small holes, case inserts, and fine pitch gear teeth need not be anodized. anodize satisfactorily may be coated in accordance with MIL-C-5541. Parts which do not 3.3.5 Components. The electronic a
28、nd mechanical components shall be in accordance with MIL-E-5400. 3.3.6 Jewel bearings. All sapphire and ruby jewel bearings used in the al timeter shall be in accordance with MIL-6-27497. 3.3.7 Threads. The threads of all machine screws shall conform to MIL-S-7742. 3.4 Design and construction. 3.4.1
29、 Features. The altimeter shall include the following features: a precision all-mechanical altimeter mechanism, a counter-drum-pointer type altitude display, integral red and white lighting, and a barometric setting displayed by means of a four digit counter. the integral vibrator is 28 VDC from the
30、emergency power bus. The design of the altimeter should provide for sustained operation under any of the preceding power conditions. The altimeter shall be so constructed that no parts will work loose in service and will withstand the normal shocks, vibrations and such other conditions as are incide
31、nt to service, shipping, storage and installation without failure. 3.4.2 Mai ntai nabi 1 i ty. repair at depot level only. The electrical power to operate The maintenance concept for thi s equipment shall be 3.4.2.1 Repair time. The altimeter shall be completely repairable at depot level. The mainte
32、nance time shall not exceed 8 hours utilizing one depot technician and authorized depot AGE and technical information. Spare parts and facilities are assumed to be available. Maintenance time shall include al 1 repair and testtime excluding government or manufacturer acceptance testi ng. 3.4.3 Mecha
33、nism adjustment. The mechanism shall be provided with a means of adjusting or correcting the indications to conform to the performance required herein, if this should become necessary during the life of the altimeter. The calibration adjustment shall not affect the temperature performance of the ins
34、trument. This means of adjustment shall be reasonably simple to manipulate and of such nature that adjustment (rezeroing) can be accompl i shed by tools ordinarily used by an instrument repairman. The adjustment shall be made in accordance with the manufacturers instructions (Government approved) at
35、 the 5 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-A-81851B level of maintenance for which such an adjustment is authorized by the government. 3.4.4 Barometric setting system. A setting system, controlled by a knob, shall be provided that wil
36、l permit the altimeter display to be set to indicate zero altitude at any existing ground level pressure throughout the range of 28.10 to 31.00 (inclusive) inches of mercury in 0.01 inch increments. The gear ratio between the setting knob and the display pointer shall be such that one complete revol
37、ution of the setting knob shall result in a display pointer movement of approximately 200 to 300 ft. Clockwise rotation of the setting knob shall result in clockwise rotation of the pointer. The shaft of the setting knob shall be capable of withstanding a load of 15 pounds applied perpendicular to t
38、he shaft at the extreme outward end of the knob without permanent deformation. A positive stop or stops shall be provided to limit the barometric setting mechanism movement such that the setting range of 28.0 to 31.1 inches of mercury is not greatly exceeded. The setting system shall not introduce e
39、rrors greater than specification tolerances when set at any point within the range established by the stops. The stops shall be capable of withstanding a torque of 6 pound inches applied to the barometric setting knob without damage to the If the design is such that the stops or the mechanism may be
40、 damaged by the application of 6 pound inches torque to the knob, the use of a torque limiting mechanism incorporated in the knob or in the instrument is acceptable if specification requirements are otherwise met. The design of such a device is subject to the approval of the qualifying agency. The r
41、esistance (torque) when setting the barometric pressure shall be within the range of 3 to 10 ounce inches. The barometric counter unit displaying the setting shall be located as shown in Figure 1. The mechanism shall be capable of withstanding a push and a pull of 15 pounds while the barometric scal
42、e is rotated through the range of settings from the minimum stop to the maximum stop without disengagement or damage of the mechanism. vibration throughout the frequency range of 5 to 2000 Hz without barometric counter display shift exceeding .O1 in. Hg. stops or the mechanism. The barometric settin
43、g system shall be designed to withstand a 2 g 3.4.4.1 Adjustment of barometric scale counter to pointer. The barometric setting system, controlled by the setting knob in its extended position, shall permit adjustment of the relative setting of the pointer and barometric scale counter. Unlockins of t
44、he zero set lockinci screw as shown in Fiqure 1 shall make this adjustment possible. It shall not be necessary to repos barometric setting knob along the setting knob shaft. The setting shall be capable of correcting for zero shifts encountered in serv without requiring that the altimeter be returne
45、d to overhual or to manufacturer for this purpose tion the system ce use the 3.4.4.2 Setting .knob position and lock. The barometric setting shall be provided with a Tock which shall hold the setting knob in its normal position and allow adjustments as specified in 3.4.4. The means for unlocking the
46、 barometric setting system shall be accessible from the face of the altimeter when installed on the instrument panel. The unlocked barometric setting system shall allow adjustments as specified in 3.4.4.1. shall provide for a seal to prevent unauthorized adjustment. The locking mechanism shall be de
47、signed to prevent the loss of the locking screw, locking The design 6 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-A-81851B hb W 7777706 01113670 MIL-A-81851B pin or any other part of the locking mechanism while rezeroing the altimeter. The de
48、sign of the locking mechanism shall be such that in the event the locking screw is accidentally loosened, movement of the barometric setting knob to the barometric scale adjustment positions shall not be possible without further action such as pulling up on the locking screw to disengage the lock. I
49、t is intended that accidental adjustment of the relative settings of the pointer, and barometric scale counter, by the aircraft pilot is precluded in the event the locking screw becomes loose. 3.4.5 Pointer, counter and drum relationship. The pointer shall indicate readings in feet with reference to a single circular uniform graduated scale making one revolution for each 1,000 ft. of altitude. The pointer shall be positively geared to the 100 ft. drum so
