1、c-s “O7 MIL-A-Z3887A(wpi 1DECEMBER 1.965 SUPERSEDING MI L-A-23 887 (WEP) 15 JANUARY 1964 MILITARY SPECIFICATION ALTIMETER SET, ELECTRONIC AN/APN-l41(V) This specification has been approved by the Bureau of Naval Weapons, Department of the Navy. 1. SCOPE 1.1 Scope - The equipment covered by this spec
2、ification shall provide an accurate indi- cation of absolute altitude of an aircraft over land or water. 1.2 Classification - The Electronic Altimeter Set shail consist of the items listed in 6.8. 2. APYLICABLE DOCUMENTS 2.1 General - T6e documents listed in 6. 10 of the issue in effect on the date
3、of invitation for bids form a part of this specification to the extent specified herein. 3. REQUIREMENTS 3.1 “3.2 Preproduction - This specification makes provision for preproduction testing. Parts and Material - In the selection of parts and materials, fulfillment of major design objectives shall b
4、e the prime consideration. In so doing the following shall govern: (i) Microelectronic items shall conform to requirements specified herein. (2) Other parts and materials requirements shall conform to Specification MIL-E-5400. (3) Nonrepairable subassemblies, as outlined in Specification MIL-E-5400,
5、 shall be used when practicable. circuitry to be included therein shall be approved by the procuring activity. Nonrepairable subassemblies must be reliable. (4) When previously produced models of this equipment did not use nonrepairable subassemblies, the design shall not be changed to employ nonrep
6、airable assemblies without the approval of the procuring activity. The general size of the subassembly and the amount uf (See 6.4. ) 3.2.1 Nonstandard Parts and Materials Approval - Approval for the use of nonstandard , parts and materials shall be obtained as outlined in Specification MIL-E-5400. E
7、lectron Devices - Electron tubes, transistors and diodes shall- be chosen and applied 3.2.2 as outlined in Specification MIL-E-4682. 3.3 Design and Construction - The equipment shall conform with all the applicable re- quirements of Specification MIL-E-5400 for design, construction and workmanship,
8、except as other- wise specified herein. *3.3.1 Total Weight - The total weight of the equipment, excluding cables, shall be a mini- mum consistent with good design and shall not exceed the sum of the individual weights specified for the units used. Provided by IHSNot for ResaleNo reproduction or net
9、working permitted without license from IHS-,-,-MIL-A-2387A 58 W 9999906 OL527LLI 3 MIL -A-23 8 87A (WP) 3.3.2 Reliability 3.3.2.1 Operational Stability - The equipment shall operate with satisfactory performance; continuously or intermittently for a period of at least 50 hours without the necessity
10、for readjustment of any controls which are inaccessible to the operator during normal use. 3.3.2.2 Operating Life - The equipment shall have a minimum total operating life of 3000 hours with reasonable servicing and replacement of parts. Parts requiring scheduled replacement shall be specified by th
11、e contractor. Reliability in Mean Time Between Failures (MTBF) - For the test program under Time Totalizing Meter - The equipment shall contain time totalizing meters in ac- *3.3.2.3 4.4.3 the mean (operating) time between failures shall be 400 hours. 3.3.2.4 cordance with Specification MIL-M-7793.
12、Meters conforming to MS17322 and having a maximum range of 10,000 hours shall be provided for both the Receiver-Transmitter RT-GOlB/APN-l41(V) and the RF Switching Unit SA-791A/APN- 141(V). 3.3.3 Cabling and Connections 3.3.3.1 Cables and Connectors - The equipment shall provide for the use of cable
13、s and con- nectors in accordance with Specification MIL-E-5400. 3.3.3.2 Interconnection Cabling - The equipment shall be capable of satisfactory operation using external wiring in accordance with the applicable requirements of Specification MIL-W-5088. The external wiring shall be unshielded except
14、that a minimum number of the individual wires may be shielded when demonstrated as necessary to meet interference control requirements and provided the assembly of the cable to its plugs may be easily accomplished. External cables and that portion of the connectors attached to the cables shall not b
15、e supplied as part of the equipment. Interchangeability of Reordered Equipment - For reordered equipment interchangea- bility shall exist between units and all replaceable assemblies, subassemblies, and parts of a desig- nated model of any previously manufactured equipment, supplied or designated by
16、 the procuring activity . 3.3.4 3.3.5 interference Control - The generation of radio interference by the equipment and the vulnerability of the equipment to radio interference shall be controlled within the limits of Specification MIL,-1-6181. 3.3.6 Maintenance Provisions and Field Testing - Provisi
17、ons for maintenance shall be as specified in specification MIL-E-5400. Specific test points and test facilities shall be provided to the greatest extent practicable for ease of field testing and maintenance. 3.3.7 Nomenclature and Nameplates - Nomenclature assignment and nameplate approval Standard
18、Conditions - The following conditions shall be used to establish norma for equipment identification shall be in accordance with Specification MIL-N-18307. performance characteristics under standard conditions and for making laboratory bench tests. Temperature Room ambient (25C rt5“C) *3.3.8 Altitude
19、 Vibration Humidity Input power voltage Normal ground None Room ambient up to 90% relative humidity 115 11. O VAC and 5 the temperature and altitude may vary at a rate as high as lC per second and O. 5 inch Hg per second, respectively. (5) Indicator - Continuous operation over the temperature altitu
20、de range as defined by Figure 1, Sheet 2, of MIL-T-5422; the temperature and altitude may vary at a rate as high as 10C per second and O. 5 inch Hg per second, respectively. - .- 3.3.9.3 Shock - Equipment shall not suffer damage or subsequently fail to provide the performance herein specified when s
21、ubjected to 18 impact shocks of 15 g having a time duration of 11 +1 milliseconds; the maximum Receiver- Transmitter, when in operation. Operation during the period of shock application is not required, but must be re- sumed with no reduction in accuracy in less than 1. O second after cessation of t
22、he shock load. shall occur at approximately 5-1/2 milliseconds. The RF Switching Unit and Coupler must survive shock loads of 32 g *3.3.9.4 Humidity - Equipment shall not suffer damage or deterioration or subsequently fail to provide the performance herein specified when subjected to an environment
23、of relative humidity up to 100 percent, including conditions wherein condensation takes place in the form of water and frost. Acoustical Noise - When the. Antennas, Receiver-Transmitter, RF Switching Unit and Coupler are normally mounted, they shall operate satisfactorily when subjected to the follo
24、w- ing acoustical environment for a period of three hours: 3.3.9: 5 + Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-A-237A 58 W 9179906 UL527Lb 7 m MIL-A-23887A (WP) 127.5 db in 75-150 cps band 126. O db in 150-300 cps band 119.5 db in 300-600
25、cps band 119.5 db in 600-1200 cps band 123. O db in 1200-2400 cps band 117. O db in 2400-4800 cps band 113. O db in 4800-9600 cps band 132.5 db overall 3.3.9.6 Equipment Nonoperation - Equipment shall not suffer damage or subsequently fail to 3.3.9.6.1 Temperature - Temperature ranging from -62C to
26、+125“C for all components except provide the performance herein specified when subjected to the following storage environment. the indicator. Temperature ranging from -62C to +95“C for Indicator only. Temperature shock of 125C delta temperature for all components. 3.3.10 Warm-up Time - The time requ
27、ired for the equipment to warm-up prior to Oper- ation shall be kept to a minimum and shall not exceed 5 minutes under standard conditions and 5 minutes at extreme service conditions. *3.3.11 Primary input Power Requirements - The equipment shall meet all applicable requirements of MIL-STD -704 and
28、shall give specified performance from the following power sources. The power required shall not exceed the specified amounts. (1) AC power (single phase) 115 V, 400 cps, category “B“ 90 volt-amperes. (2) 5. O volts, AC or DC, 1. O amp (for Indicator lighting) The electric power desribed above shall
29、also be sufficient to operate the equipment as necessary to perform all servicing functions on the equipment. 3.3.11.1 Degraded Performance - Degraded performance will be permitted for voltage transients not exceeding O. 5 second during normal electric system operation. to normal with no resulting d
30、amage to the equipment, Operation shall return 3.4 Performance - Unless otherwise specified, values set forth to establish the require- ments for satisfactory performance apply to performance under both standard and extreme service conditions. When reduced performance under the extreme conditions is
31、 acceptable, tolerances or values setting forth acceptable variations from the performance under the standard conditions will be specified. Operation - The Electronic Altimeter Set is a range tracking radar that utilizes pulse techniques and leading edge tracking of ground return signals to produce
32、highly accurate altitude infor- mation from O to 5,000 feet of altitude. The altimeter system has two modes of operation. In the search mode, the system successively examines increments of range with each cycle of operation until the complete altitude range is searched for a ground return signal. In
33、 the track mode, the system locks on and tracks a ground return signal giving continuous altitude information. Altitude information is obtained by measuring the time from the instant that r-f energy leaves the transmitter until the first ground return signal is detected in the receiver. The system c
34、onverts this time interval information to a dc voltage. amplitude of the dc voltage. 3.4.1 This voltage is applied to a device which indicates altitude (in feet) proportional to the Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-A-238878 (WP) 3:
35、4.2 Altitude Range - The equipment shall operate reliably and indicate absolute altitude from O to 5,000 feet over water or land. 3.4.3 Accuracy - The over-all system accuracy shall be less than +5 feet or +5 percent of the correct terrain clearance, whichever is the greater. 3.4.4 Frequency - The e
36、quipment shall operate within the allocated frequency range of 4200 to 4400 megacycles with a center frequency of 4300 110 megacycles and with guard bands at both ends of the range to preclude interference with equipment operating outside this range. 3.4.5 Electrical Tracking Rate *3.4. 5.1 Indicate
37、d Altitude - The equipment including Indicator shall follow changes in height at the rate of not less than A/2 feet/second or 50 feet/second whichever is greater (where A equals the indicated altitude in feet). *3.4.5.2 Altitude Signal - The altitude signal (equipment less the Indicator) shall follo
38、w changes in height at the rate of not less than 400 feet/second below 400 feet of indicated altitude and 3000 feet/second above 400 feet of indicated altitude. Tracking error shall be less than 2% of tracking rate below 400 feet and less than 1/2% of tracking rate above 400 feet. C3.4.6 Ground Spee
39、d Limit - The system shall provide reliable operation over level terrain and constant aircraft height at all ground speeds up to 2000 knots. 3.4.7 Minimum Reflected Signal - Minimum reflected signal at 5,000 feet shall be no less than 9 db above that required for reliable operation assuming 12 db at
40、tenuation at reflection. 3.4.8 Aircraft Attitude - The system shall operate normally and reliably in an aircraft when climbing and diving at 50“ angles and when banking at 30“ angles. No detrimental effects shall be caused to the operation of the equipment by any flight maneuver, and operation of th
41、e equipment in any position shall not prevent normal operation when the aircraft returns to normal flight. 3.4.9 *3.4.10 False Indication - The system shall not lock on noise or any interfering or false Low Altitude Limit Function - A switching function shall be provided in the altimeter signal. whi
42、ch will complete an electrical circuit when the absolute altitude is lower than the preselected height. The switching function in the ID-881 and ID-1015 units shall close and open at the limit index setting within +5 feet or +5 percent of the indicated altitude, whichever is greater (+lo feet or +10
43、 per- cent of the existing altitde). The switching function in the ID-1304 units shall close and open at the limit index setting +lo feet or 5 percent of the indicated altitude, whichever is greater (+15 feet or - +10 percent of the unless tests indicate that a reliable ground lock-on can be maintai
44、ned during hi. 3.4.12 unit. This will be used for inflight and preflight testing of the equipment. Self-test shall be activated by depressing the control knob on the Indicator Unit or closing the contacts of the weight-on-gear switch and shall be capable of being energized continuously with no detri
45、mental effects. The indicator shall indicate 5, +5, -10 feet whenever self-test is actuated. Self-Test Provisions - A “GO, NO-GO“ test provision shall be incorporated in the 5 7 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-A-23887A 58 9777706
46、0352738 O W 3.5 Detailed Requirements 3.5.1 Receiver- Transmitter RT- 6OlB/APN- 141 (V) - The Receiver- Transmitter shall meet the following requirements. 3.5.1.1 Function - The Receiver-Transmitter shall transmit a radio frequency signal, re- ceive the reflected signal, and derive the proper indica
47、tion of radar altitude in accordance with the performance of this specification. 3.5.1.2 Form Factor - The Receiver-Transmitter shall be contained within the volume defined in Figure 1. *3.5.1.3 3.5.1.4 Weight - The weight of the Receiver-Transmitter shall not exceed 6.5 pounds. Contents of Unit - T
48、he Receiver-Transmitter shall contain the following assemblies and circuits. 3.5.1.4.1 Power Supply - The power supply shall convert the 115 V, 400 cps, single phase - 3.5.1.4.2 Modulator - The modulator shall provide the triggering pulse to the transmitter cavity, the positive bias pulse and narrow
49、 pulse trigger to the microwave crystal switch, and a low- altitude fast ramp trigger pulse to the time comparator. 3.5.1.4.3 Transmitter Cavity - The transmitter cavity shall be a plate pulsed cavity oscil- lator having a manual frequency adjustment. The cavity is driven into oscillation by the modulator trigger pulse. A sample of the RF energy shall be coupled out of the cavity, detected and applied to the time comparator to operate the high altitude fast ramp. The output characteristics of the
