1、p -U-Q7 MIL-A-BL27bD 58 779790b 0367995 L MI L-A-81296D _. (AS 1 22 July 1985 SUPERSEDING 3 JANUARY 1974 MIL-A-81296C( AS) MILITARY SPECIF ICATION ALTIMETER SET, ELECTRONIC, ANIAPN-171 (V) This specification is approved by the Naval Air Systems Command, Department of the Navy, and is available for u
2、se by all Departments and Agencies of the Department of Defense. 1. SCOPE 1.1 Scope. This specification establishes the design, performance, and acceptance requirements for the AN/APN 171(V) electronic altimeter set, herein referred to as the equipment. The equipment covered by this specification sh
3、all provide an accurate indication of absolute altitude of an aircraft over land and water. *1.2 Classification. The equipment.covered by this specification consists of the following items: I tem Receiver-Transmitter, Radar Recei ver-Transmi tter, Radar Recei ver-Transmi tter, Radar Receiver-Transmi
4、tter, Radar Receiver-Transmi tter, Radar Recei ver-Transmi tter, Radar Indicator, Height Indicator, Height Indicator, Height Antenna Mounting - Type Designation RT-804B/APN-171 (V) RT-805/APN-171( V) RT-806A/APN-171 (V) RT-829A/APN-171 (V) RT-1006/APN-171 (V) RT-1062A/APN-171 (V) ID-1345/APN-171 (V)
5、 ID-1346/APN-171( V) ID-1725/APN-171 (V) AS-1858/APN-171 (V) MT-4167/APN-171 (V) Beneficial comnents (recmendations, additions, 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 Engineer
6、ing and Standardization Department (SESD) Code 93, Lakehurst, NJ 08733, by using the self-addressed Standardization Document Improvement Proposal (DD Form 1426) appearing at the end of this document or by letter. THIS DOCUMENT CONTAINS PAGES FSC 5826 “DISTRIBUTION STATEMENT A. Approved for public re
7、lease; distribution is unlimited.“ Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MI L -A-81 296 D ( AS ) 1.3 Associated Equipment . The equipment should operate with the associated equipment listed in 6.8. 2, APPLICABLE DOCUMENTS *2.1 Government Do
8、cuments. 2.1.1 Specifications and Standards. Unless otherwise specified, the following specifications and standards of the issue listed in that issue of the Department of Defense Index of Specifications and Standards (DoDISS) specified in the solicitation form a part of this specification to the ext
9、ent specified herein. SP E C I F I CAT I ON S MILITARY MIL IC-67 5 MIL -W -5088 MIL-E-5400 MI L -T - 54 2 2 MIL -1 -6181 MIL -M-7 793 MIL-E-17555 MIL -T-18303 MI L-N-18307 MIL-L-25467 MIL-L-27160 P Coating of Glass Optical Elements (Anti Reflection) Wiring; Aircraft, Installation of Electronic Equip
10、ment, Aircraft, General Specification for Testing, Environmental, Aircraft Electronic Equipment Interference control Requirements , Aircraft Equi pments Meter, Time Totalizing Electronic and electrical Equipment and Associated Repair Parts, Preparation for Delivery of Test Procedures; Preproduction
11、and Acceptance, for Aircraft Electronic Equipment, Format for Nomenclature and Nameplates for Aeronautical Electronic and Associ ated Equipment Lighting, Integral, Aircraft Instrument, General Specification for Lighting, Instrument, Integral White, General Specification for 2 Provided by IHSNot for
12、ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-A-8129bD 58 99977Ob OLb9997 5 MIL-A-81296D( AS) ST ANDAR DS O MILITARY MIL-STO-704 MIL-STO-781 Reliability Tests, Exponential Distribution MIL-STO-794 MIL-STD-965 Parts Control Program MIL-STO-2077 MIL-STO-2074 MS 17322 Y
13、S 24367 Electric Power, Aircraft, Characteristics and Utilization Parts ir 15 ns 125 T 75 ns . 900 i 350 ns +lo 2v O 2 0.5V *3.5.2.3 External zero altitude adjust. An externally accessible zero altitude adjustment shall be provided on the front of the Receiver-Transmitter to provide altitude adJustm
14、ent of not less than 2 5 feet. 3.5.3 Receiver-Transmi tter, Radar - RT-805/APN-l71(Vr 3.5.3.1 Function. The Receiver-Transmitter shall transmit a radio frequency signal, receive the reflected signal, and derive the proper analog voltage for O to 1,000 feet of radar altitude in accordance with the re
15、quirements of this specification. The range computer assembly shall consist of four printed circuit card networks. *3.5.4. Receiver-Transmi tter, Radar - RT-806A/APN-171( V) 3.5.4.1 Function. The Receiver-Transmitter shall transmit a radio frequency signal, receive the reflected signal, and derive t
16、he proper analog voltage for O to 1,000 feet of radar altitude in accordance with the requirements of this specification. The range computer assembly shall consist of five printed circuit card networks. 12 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-
17、,-,-MIL-A-L246D 58 W 9999706 OL70007 2 W MIL-A-812960( AS) *3.5.4.1.1 Additional outputs. In addition to the altimeter functions specified in 3.5.1 herein, the Ri-806Af APN-l71(V) shall twovide additional outwts compatible with-other aircraft systems: outputs. Receiver-Transmitter unit to provide th
18、ese outputs shall meet and in no way degrade those requirements specified in 3.5.1. 3.5.412 through 3.5.4.6 specify these The additional circuitry and components which must be added to the *3.5.4.2 Automatic fliqht control system interface. RT-806A/APN-l71(V) shall provide an altitude error output w
19、hich is referenced to a selected altitude. The error output is used by the Automatic Flight Control System (AFCS) to provide the aircraft with an automatic altitude hold capability. 3.5.4.2.1 Altitude error siclnal. proportional to the altitude difference between the aircraft altitude as sensed by t
20、he altimeter and a reference altitude. The reference altitude is represented by an altitude reference signal as specified in 3.5.4.2.1.8. The altitude error signal is a voltage 3.5.4.2.1.1 Error signal. The altitude error signal shall be a 400 Hz signal with a scale factor of 716 millivolts RMS per
21、foot of error. 3.5.4.2.1.2 Signal null. The altitude error signal shall reach a minimum when the aircraft altitude coincides with the reference altitude. This minimum or null signal shall occur when the altitude signal (see 3.5.1.7.2) is within one foot or 2 percent, whichever is greater, of the ref
22、erence altitude under standard conditions and one foot or 5 percent, whichever is greater, under service conditions. The null voltage shall be not greater than 716 millivolts RMS and the 400 Hz component shall be not greater than 358 millivolts RMS. 3.5.4.2.1.3 Resolution. The error signal shall hav
23、e a resolution of 0.5 foot for al ti tude errors between -50 and +50 feet for reference al ti tudes extending from O to 200 feet. 3.5.4.2.1.4 Accurac The slope of the error signal shall be within 5 percent feet . of the 716 mil 7-y ivolt per foot scale factor for all altitude errors between - t 30 3
24、.5.4.2.1.5 Linearity. The error signal shall not deviate more than 0.33 feet or 2 percent, whichever is greater, from the best straight line whose slope is within 5 percent of 716 millivolt per foot, for altitude errors between - t 30 feet 3.5.4.2.1.6 Phase. Receiver-Tran-er units 400 Hz excitation
25、shall be O0 when the aircraft altitude is greater than the reference altitude and 180 when the aircraft altitude is less than the reference altitude. The phase angle tolerances shall be + 7O under standard conditions and 2 100 under service conditions for altTtude errors between + 10 feet. angle tol
26、erance shall be-+ - 150 under service conditions. The error signal phase angle with reference to the For errors greater than 2 10 feet, the phase 13 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-A-81296D (AS) a 3.5.4.2.1.7 Load, The altitude er
27、ror signal shall be capable of operating into a 200,000 ohmresistive load, 3,5.4,2.1,8 Altitude reference signal. The reference altitude, represented by a linear dc voltage proportional to the reference altitude, shall be provided to the Receiver-Transmitter unit, This signal is developed across a 2
28、500 ohm (1 percent resistance tolerance and 2 percent linearity) potentiometer which is excited by a -15 VDC 1 3-percent output from the Receiver-Transmitter unit. The potentiometer is linearly calibrated to 200 feet. 3.5.4,3 Self-test inhibit signal, A 28V (nominal) signal shall be provided to * th
29、e Receiver-Transmitter unit to inhibit the self-test function of the altimeter. Normal self-test operation shall be restored when this voltage is removed, This signal shall be provided by the AFCS when the radar altimeter coupler is engaged and shall be removed when the coupler is disengaged. *3,5,4
30、.4 Radar altimeter warning system interface. The RT-806A/APN-l71(V) shall provide an altitude proportional signal and an altimeter reliable signal to the radar al timeter warning system (RAWS) 3.5,4.4,1 Proportional signal. A positive, linear dc voltage proportional to altitude shall be available. T
31、he range of this signal shall be 1 volt to 11 volts corresponding to O feet to 500 feet respectively. The signal shall be not greater than +15 volts dc at altitudes above 500 feet or when the altimeter is not in track. O 3,5.4.4,1,1 Accurac The proportional signal shall be within 2.5 feet plus 2 per
32、cent of actual altitude plus 5 percent of average altitude rate under service conditions in the range of O to 500 feet. percent of actua + a titude under standard conditions and within five feet plus 5 3.5.4,4,1.2 Load. The proportional signal shall be as specified when connected to a 10,000 ohm res
33、istive load, *3.5.4,5 Blanking pulse output, A blanking pulse shall be provided having the fol lowing characteristics: a. b, da e. f, g* he C. Load Impedance Source Impedance RF Lead Time Ri se Time (10-90%) Fall Time (10-90%) Width (50% points) Amp1 i tude Inter-pulse Output 1000 ohm typical, 50 oh
34、m min. Less than 10 ohms 300 + 50 ns 20 7: 15 ns 125 T 75 ns 900 c 350 ns +lo c 2v O 7 - 0.5V 14 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,- MIL-A-8227bD 58 9777706 0270009 b MIL-A-81296D( AS) *3.5.4.6 External zero altitude adjust. An externall
35、y accessible zero altitude adjustment shall be provided on the tront of the receiver-transmitter to provide altitude adjustment f not less than 2 5 feet. 3.5.5 Indicator, Height - ID-l345/APN-l71(V) 3.5.5.1 Function. The indicator shall indicate altitude from O to 5,000 feet by means of a single poi
36、nter against a fixed dial. A movable marker positioned against the same dial shall indicate the pre-selected height below which the control signals for the altitude warning device operates. The “no track“ condition shall be indicated by a flag coming into view. Altitudes higher than 5,000 feet or th
37、e loss of track, shall also be indicated by clockwise movement of the pointer behind the masked portion of the indicator dial. The accuracy, sensitivity and low altitude switch errors shall be within the limits specified in Table I. . 3.5.5.2 Form factor. The indicator shall conform to the dimension
38、s of EI-562-12. 3.5.5.3 Weight. 1.6 pounds. The weight of the height indicator shall be not greater than 3.5.5.4 Contents. Each indicator shall include the. necessary mechanism to rotate the altitude indicator pointer to a position determined by the system. It shall also include a low altitude limit
39、 index. 3.5.5.5 Controls. A control knob located as shown in EI-562-12 shall control the low altitude limit index, actuation of the self-test circuit, and also function as the system power control knob. The low altitude limit index shall be continuously adjustable throughout the range of the equipme
40、nt. When the equipment is turned off, this index shall be positioned at less than zero feet. When the equipment is turned on, the initial position of the limit index shall be no greater than zero feet. depressing the control knob. The self-test circuit shall be actuated by *3.5.5.6 Electrical connec
41、tions. A single multicontact connector shall be mounted on the back of the indicator opposite the dial for all electrical connections. Connections to external circuits shall be as shown on EI-562. 3.5.5.7 Dial markings. The scale markings shall utilize approximately 320 degrees of the dial face. The
42、 dial shall be as shown in figure 2. The tip of the pointer shall provide 0.03 inch clearance with the innermost point of the minor graduations. The low altitude limit index shall be in the form of an equilateral triangle and shall be positioned to provide 0.03 inch clearance with the pointer tip. 1
43、5 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,- - MT.L-L29bD 58 i 99979Ob 017OOLO MIL-A-81296D( AS) 2i 3.5.5.8 Indicator protection, to avoid damaging the indicator at altitudes above 5009 feet and the system chal 1 resume normal operation while d
44、escending through 5090 feet. Protection shall be provil ed wi hin the system * 3.5.5.9 Low altitude limit. The indicator shall contain the low altitude warning light as specified in 3.4.9. 3.5.5.10 Response. 0.3 seconds. full scale response of the indicator pointer shall be 2.0 2 3.5.5.11 Damping. T
45、he indicator shall be damped to prevent pointer overshoots greater than one degree. The settling time of the pointer shall be not greater than 0.2 second, Damping shall be 0.6 to 0.85 of critical. 3.5.5.12 Lightingr The indicator shall incorporate integral red lighting in accordance with MIL-L-25467
46、. The indicator lighting shall be compatible with 5 volt and 28 volt ac and dc aircraft lighting systems, For 5 volt lighting, MS24367 lamps with a red coating shall be used. For 28 volt lighting, T-1 size lamps (Los Angeles Miniature Lamp Co. #62 or approved equal) with a red coating shall be used.
47、 3.5.5.12.1 Coverglass and wedges, A reflection reducing film as specified in MIL-C-675 shall be mandatory on the instrument coverqlass and optional on intermedi ate transparent elements between the covergfass and di al. 3.5.5.12.2 Brightness. Lighting shall be in accordance with MIL-L-25467 except
48、that pointer tip brightness shall be greater than that of the nearest exposed indicia. 3.5.5.13 Fogging. The indicator face shall be free of any visible condensation when operating within the environmental conditions specified in 3.3.10. A rapid change in environmental conditions shall not generate
49、condensation on the face of the indicator. 16 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,- MIL-A-8129bD 58 W 9999906 OL70011 Y W I I I MIL-A-81296D ( AS) - +(6.4ft.+0.88% of alt.) Table I. ID-l345/APN,-171 (V) Indicator characteristics (-0 to 50.00 foot unit) +53.4 1 - +22.0 Al ti tude Range (feet) o - 200 200 -1000 1000 -5000 Sensitivity (feet) - + 0.50 +3 - + 15 Po
