1、AEROSPACE RECOMMENDED PRACTICEARP427 REV.AIssued 1958-02Reaffirmed 2008-02Revised 2001-07Superseding ARP427Pressure Ratio InstrumentsFOREWORDChanges in this Revision are format/editorial only.1. SCOPE:This Aeronautical Recommended Practice covers two types of two unit Pressure Ratio Instruments each
2、 of which consist of a Transducer and an Indicator. The Transducer computes the ratio of two pressures and converts this ratio to a synchro electrical signal which is transmitted to the Indicator.Type I - All material in this document applies to this classification only.Type II - Additional material
3、 for this classification will be added to superseding issues as the state ofthe art permits.1.1 Purpose:To recommend requirements for electrical Pressure Ratio Indicating Instruments for use in aircraft, the operation of which may subject the instruments to the environmental conditions specified in
4、Paragraph 3.3.This recommended practice is to be considered as being currently applicable and necessarily subject to revision from time to time due to rapid development in the aircraft industry.2. REFERENCES:NACA Report 12353. GENERAL REQUIREMENTS:3.1 Materials and Workmanship:SAE Technical Standard
5、s Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is the sole respon
6、sibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions. Copyright 2008 SAE International All rights reserved. No part of this publication may be reproduced, stored
7、 in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: 724-776-4970 (outside USA) Fax: 724-776-0790 Email
8、: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE ARP427 Revision A- 2 -3.1.1 Materials: Materials should be of a quality which experience and/or tests have demonstrated to be suitable and dependable for use in aircraft instruments.3.1.2 Workmanship: Workmanship should be consistent wi
9、th high-grade aircraft instrument manufacturing practice.3.2 Identification:The following information should be legibly and permanently marked on the instrument or attached thereto:a. Name of instrument - Pressure Ratio Transducer, or Indicatorb. SAE Aeronautical Recommended Practice ARP427Ac. Manuf
10、acturers part numberd. Manufacturers serial number or date of manufacturee. Manufacturers name and/or trademarkf. Rangeg. Rating3.3 Environmental Conditions:The following conditions have been established as design requirements only. Tests should be conducted as specified in Sections 5, 6, and 7.3.3.
11、1 Temperature: When installed in accordance with the instrument manufacturers instructions, both transducer and indicator should function over a range of ambient temperatures from -55 C to 70 C. The indicator should not be adversely affected by exposure to temperatures of from -65 C to 80 C. The tra
12、nsducer should not be adversely affected by exposure to temperatures of from-65 C to 120 C.3.3.2 Humidity: The instrument should function and should not be adversely affected when exposed to any relative humidity in the range from 0 to 95% at any temperature up to 70 C.3.3.3 Vibration: When installe
13、d in accordance with the instrument manufacturers instructions, the instrument should function and should not be adversely affected when it is subjected to vibrations of the following characteristics.SAE ARP427 Revision A- 3 -3.3.4 Altitude: The instrument should function and should not be adversely
14、 affected when subjected to a pressure and temperature range equivalent to -1000 to 50,000 feet standard altitude per NACA Report 1235, except as limited by application of Paragraph 3.3.1. The indicator should not be adversely affected when subjected to a pressure of 50 in Hg absolute.3.4 Explosive
15、Atmosphere:All instruments located in the uninhabited areas of non-pressurized aircraft or in non-pressurized areas of pressurized aircraft should not cause an explosion when operated in an explosive mixture.3.5 Radio Interference:The instrument should not be the source of objectionable interference
16、, under operating conditions at any frequencies used on aircraft, either by radiation or feedback, in the radio equipment installed in the same aircraft as the instrument.3.6 Magnetic Effect:The magnetic effect of the instrument should not adversely affect the operation of other instruments installe
17、d in the same aircraft.4. DETAILED REQUIREMENTS:4.1 Rating:4.1.1 Pressure: The engine inlet pressure (PT2) limits are 7.0 to 60.0 inches of mercury absolute. The engine exhaust pressure (PT7) limits are 8.4 to 180.0 inches of mercury absolute.4.1.2 Electrical: The instrument should be designed to op
18、erate on 115 plus or minus 10% volts a-c, 400 plus or minus 5% cycles per second power.TABLE 1Instrument Locationin Airframe Cycles per Second Maximum DoubleAmplitude (Inches)MaximumAccelerationFuselage Forward-of 5-500 .036 2 gspar areaPanel or Rack (with 5-500 .02 2 gshock mounts)SAE ARP427 Revisi
19、on A- 4 -4.2 Mounting:The mounting rack, if used, should be such that it will satisfy the conditions necessary for shock and vibration tests.4.3 Indicating Range:The indicating range should be graduated from 1.2 to 3.4.4.4 Filling Medium:When hermetically sealed, the case should be filled with an in
20、ert gas at least 10 percent helium, of at least 98 percent purity, free of dust particles, and sufficiently dry so that fogging of the dial glass (indicator) does not occur during the low temperature tests of this ARP.4.5 Finish:Unless otherwise specified by the user, matte white material should be
21、applied to all major graduations, numerals and pointer. Non-functional surfaces should be durable dull black.4.6 Visibility:The indicating means and all significant dial markings should be readable from any point within the frustrum of a cone whose sides make an angle of not less than 30 degrees wit
22、h the perpendicular to the dial, and whose small diameter is the aperture of the instrument case. The distance between the dial and the cover glass should be a practical minimum and should not exceed 0.250 of an inch.5. TEST CONDITIONS:5.1 Atmospheric Conditions:Unless otherwise specified, all tests
23、 required by this ARP should be made at an atmospheric pressure of approximately 29.92 inches of mercury and at an ambient temperature of approximately 25 C, and at a relative humidity of not greater than 85%. When tests are conducted with the atmospheric pressure or the temperature differing materi
24、ally from these values, allowance should be made for the variation from the specified conditions.5.2 Power Conditions:Unless otherwise specified, the instrument should be tested with an applied voltage of 115V plus or minus 2 percent, AC single phase, 400 cps plus or minus 2 percent.SAE ARP427 Revis
25、ion A- 5 -5.3 Transmitting and Indicating Standards:Each synchro transmitter in the transducer and each synchro receiver in the indicator should be connected to an indicating standard and a transmitting standard, respectively, when readings must be taken except as otherwise specified. The indicating
26、 standard should be completely calibrated, and should have a maximum error of plus or minus 0.50 circular degrees when tested against a primary transmitting master. The primary transmitting master should have a maximum error of plus or minus 0.10 circular degrees. The tolerances of the standards may
27、 be added to those indicated for the applicable tests.5.4 Position:Unless otherwise specified, all tests should be conducted with the instrument in its normal operating position.5.5 Vibration Equipment:Vibration equipment should be used which will provide frequencies and amplitudes consistent with t
28、he requirements of Paragraph 3.3.3 with the following characteristics:5.5.1 Linear Motion Vibration: Vibrating equipment should be such as to allow vibration to be applied along each of three mutually perpendicular axes of the test instrument.5.5.2 Circular Motion Vibration: Vibration equipment shou
29、ld be such that a point on the instrument case will describe a circle in a plane inclined 45 degrees to the horizontal plane, the diameter of which is equal to the double amplitude specified.6. INDIVIDUAL PERFORMANCE REQUIREMENTS:All instruments should be subjected to whatever tests the manufacturer
30、 deems necessary to demonstrate specific compliance with this ARP, including the following requirements where applicable.6.1 Scale Error:With the transducer connected under the conditions of Paragraphs 5.1 and 5.2 pressures should be applied to the engine exhaust pressure and engine inlet pressure c
31、onnections per Table 1. The engine inlet pressure is to be stabilized. The engine exhaust pressures should be brought up to, but should not exceed the value given; a reading taken; the transducer tapped or gently vibrated, and another reading taken. The procedure should be repeated for decreasing en
32、gine exhaust pressures. Each reading taken after tapping should not differ from the theoretical reading by more than the tolerances given in Table 2A.The indicator scale errors should not exceed the tolerances given in Table 2B.SAE ARP427 Revision A- 6 -6.2 Friction Error:The difference between read
33、ings taken before and after tapping in Paragraph 6.1 should not be more than the values given in Tables 2A and 2B.6.3 Position Error:The difference in indicator readings between tests in the normal position and those in any other position should not exceed that shown in Table 2B.6.4 Power Variation
34、Test:When the power supply is varied between the limits indicated in Paragraph 4.1.2, the instrument (system) should not indicate a pressure ratio change exceeding .005.6.5 Leakage:The engine inlet pressure connection should be pressurized to 42 inches of mercury absolute. The pressure tube should t
35、hen be “pinched“ or otherwise sealed off upstream of the manometer. The pressure should not decrease by more than .15 inches of mercury during the next five (5) minute period. The engine exhaust pressure connection should be open to atmosphere during this test.The above test should be repeated with
36、a pressure of 96 inches of mercury absolute applied to the engine exhaust pressure connections and a pressure of 35 inches of mercury absolute applied to the engine inlet pressure connection. The engine exhaust pressure should not decrease more than .25 inches of mercury during the five (5) minutes.
37、 The volume of the entrapped air in the manometer well and connecting piping should not exceed 45 cubic inches.6.6 Dielectric:Ungrounded instruments or grounded instruments prior to connection of internal ground wire, should be tested by either the method of inspection of Paragraph 6.6.1 or 6.6.2.6.
38、6.1 Insulation Resistance: The insulation resistance measured at 500 volts DC (200 volts for hermetically sealed, inert gas filled instruments) between all electrical circuits connected together and the metallic case should not be less than 20 megohms.6.6.2 Dielectric Strength: The insulation should
39、 withstand without evidence of damage the application of a sinusoidal voltage at a commercial frequency between all electrical circuits connected together and the metallic case, for a period of five seconds. The RMS value of the sinusoidal voltage applied should be either five (5) times the maximum
40、instrument operating voltage, or 500 volts, (200 volts for hermetically sealed, inert gas filled instruments) whichever is lower.SAE ARP427 Revision A- 7 -6.6.2.1 Instruments having a permanent internal ground connection should be tested as follows:The insulation should withstand without evidence of
41、 damage the application of a sinusoidal voltage at a commercial frequency between each electric circuit and the metallic case, for a period of five (5) seconds. The RMS value of the sinusoidal voltage applied should be 1.25 times the maximum circuit operating voltage obtainable between two test poin
42、ts.7. QUALIFICATION TESTS:As many instruments as may be deemed necessary to demonstrate that all instruments will comply with the requirements of this section should be tested in accordance with the manufacturers recommendations.7.1 Room Temperatures:7.1.1 Response Rate: The transducer should be con
43、nected to an indicating standard. Pressure should be applied to the engine inlet pressure connection per Table 3 and stabilized at each test point. Pressure should then be applied to the engine exhaust pressure connection for the smaller number listed in Table 3 corresponding to the engine inlet pre
44、ssure used. When the pressures are stabilized the pressures should be blocked in the transducer. The power should remain “on“ during this test. A set up similar to Figure 1 should be used. The quick acting valve should be closed and the pressure should then be raised to and stabilized at the higher
45、pressure given in Table 3 corresponding to the engine inlet pressure used. The quick acting valve should be opened within 5 minutes after the pressures are stabilized. The response time during each step tested should not be greater than the times specified in Table 3. The indicator should be conside
46、red stabilized when the total motion does not exceed 0.02 inches. The indicating means should begin to move within 0.25 seconds of the change in pressure in the transducer. The indicator should stabilize within 1.5 seconds of the time the indicating means first shows the final reading.7.1.2 Sensitiv
47、ity and Deadband: The engine inlet pressure and the engine exhaust pressure should be adjusted and stabilized to the pressures indicated in Table 4. While holding the engine inlet pressure constant, the engine exhaust pressure should be increased until a change of indication is first detected. The e
48、ngine exhaust pressure should then be decreased slowly until a change of indication is detected. The decrease of pressure necessary to cause the change of indication should not be greater than those values specified in Table 4. The procedures should be repeated by varying the engine inlet pressure a
49、nd holding the engine exhaust pressure constant.SAE ARP427 Revision A- 8 -7.2 Humidity:The instrument, unless hermetically sealed, should be mounted in a chamber maintained at a temperature of 70 plus or minus 2 C and a relative humidity of 95 plus or minus 5% for a period of six hours. After this period the heat should be shut off and the instrument allowed to cool for a period of 18 hours in this atmosphere in which the humidity rises to 100% as the temperature decreases to not more than 38 C. This complete cycle shoul
