1、AEROSPACESTANDARDSubmitted for recognition as an American National StandardMAXIMUM-ALLOWABLE-AIRSPEED INSTRUMENTS(TURBINE POWERED SUBSONIC AIRCRAFT)SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. Theuse of
2、 this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is thesole responsibility of the user.”SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or ca
3、ncelled. SAE invites your writtencomments and suggestions.Copyright 1996 Society of Automotive Engineers, Inc.All rights reserved. Printed in U.S.A.Land Sea Air and SpaceFor Advancing MobilityThe Engineering SocietyI N T E R N A T I O N A L 400 Commonwealth Drive, Warrendale, PA 15096-0001 Issued 19
4、63-04Revised 1996-09REV. AS437 AFOREWORDChanges in the revision are format/editorial only.1. SCOPE:This SAE Aerospace Standard (AS) covers one type of maximum-allowable-airspeed instrumentwhich gives a continuous indication of both indicated airspeed and maximum allowable airspeednot exceeding 650 k
5、nots.1.1 Purpose:This Aerospace Standard establishes the essential minimum safe performance standards forpitot-static type of maximum-allowable-airspeed instruments primarily for use with turbinepowered subsonic transport aircraft, the operation of which may subject the instruments to theenvironment
6、al conditions specified in Section 3.3.2. APPLICABLE DOCUMENTS:The following publications form a part of this document to the extent specified herein. The latestissue of SAE publications shall apply. The applicable issue of other publications shall be the issuein effect on the date of the purchase o
7、rder. In the event of conflict between the text of thisdocument and references cited herein, the text of this document takes precedence. Nothing in thisdocument, however, supersedes applicable laws and regulations unless a specific exemption hasbeen obtained.2.1 NTIS Publications:Available from NTIS
8、, Springfield, VA 22161.NACA Report 1235SAE AS437 Revision A- 2 -3. GENERAL REQUIREMENTS:3.1 Materials and Workmanship:3.1.1 Materials: Materials shall be of a quality which experience and/or tests have demonstrated tobe suitable and dependable for use in aircraft instruments.3.1.2 Workmanship: Work
9、manship shall be consistent with high grade aircraft instrumentmanufacturing practice.3.2 Identification:The following information shall be legibly and permanently marked on the instrument or attachedthereto.a. Name of instrument.b. SAE AS437.c. Manufacturers part number.d. Manufacturers serial numb
10、er or date of manufacture.e. Manufacturers name and/or trademark.3.3 Environmental Conditions:The following conditions have been established as minimum design requirements. Tests shall beconducted as specified in sections 5, 6, and 7.3.3.1 Temperature: When installed in accordance with the instrumen
11、t manufacturers instructions,the instrument shall function over the range of ambient temperature shown in column A belowand shall not be adversely affected by exposure to the range of ambient temperature shown incolumn B below.TABLE 1Instrument Location A BPressurized Areas -30 to 70 C -65 to 70 CSA
12、E AS437 Revision A- 3 -3.3.2 Altitude: When installed in accordance with the instrument manufacturers instructions, theinstrument shall function from sea level up to the altitudes and temperatures listed below. Altitude pressure values are per NACA Report 1235. The instrument shall withstand anexter
13、nal case pressure of 50 inches Hg absolute when installed properly and vented to anatmospheric pressure of approximately 29.92 inches Hg absolute.TABLE 2Instrument Location Altitude TemperaturePressurized Area 15,000 feet 50 C3.3.3 Vibration: When installed in accordance with the instrument manufact
14、urers instructions, theinstrument shall function and not be adversely affected when subjected to vibrations of thefollowing characteristics.TABLE 3Frequency Maximum DoubleCycles Amplitude MaximumInstrument Location Per Second Inches AccelerationInstrument panel 5 - 30 0.02030 - 1000 - 0.25 g3.3.4 Hu
15、midity: The instrument shall function and shall not be adversely affected following exposureto any relative humidity in the range from 0 to 95% at a temperature of approximately 70 C.3.3.5 Magnetic Effect: The magnetic effect of the instrument shall not adversely affect theperformance of other instr
16、uments installed in the same aircraft.4. DETAIL REQUIREMENTS:4.1 Display Markings:4.1.1 Finish: Unless otherwise specified by the user, matte white material shall be applied to allgraduations, numerals and indicating means.Non-functional surfaces and markings shall be durable dull black.4.1.2 Gradua
17、tions: The graduations shall be arranged to provide the maximum of readabilityconsistent with the accuracy of the instrument.SAE AS437 Revision A- 4 -4.1.3 Numerals: The display shall include sufficient numerals to permit quick and positiveidentification of each graduation. Numerals shall distinctly
18、 indicate the graduation to whicheach applies.4.1.4 Instrument Title: The instrument title (airspeed) shall be of the same approximate size but nolarger than the numerals. The title may be of the same finish as the numerals. The units ofmeasure (Knots) shall appear on the dial in lettering noticeabl
19、y smaller than either the numeralsor title.4.1.5 Visibility: The indicating means and all markings shall be visible from any point within thefrustrum of a cone the side of which makes an angle of at least 30 degrees with theperpendicular to the dial and the small diameter of which is the aperture of
20、 the instrument case.The distance between the dial and the cover glass shall be a practical minimum.4.1.6 Indicating Means: Indicated airspeed and maximum-allowable-airspeed shall be displayed insuch a manner that the numerical values on the scale(s) shall increase in a clockwise, left toright, or b
21、ottom to top direction.4.2 Calibration:4.2.1 Airspeed Pointer: The indicated airspeed pointer shall indicate airspeed in accordance with thefollowing equation:V C qPi so co= +Ge7 Gf7 Ge9GebGeaGeaGeaGfaGfaGfa21 1 11 (Eq.1)where:Vi = Indicated airspeed in KnotsCso = Sea level speed of sound = 661.48 K
22、notsPo = Pressure at sea level - 29.92126 inches Hgqc = Impact pressure in inch Hg = Total pressure - Static Pressure = Ratio of specific heats = 1.40 for airValues shown in Table 4 are in accordance with the above.SAE AS437 Revision A- 5 -4.2.2 Maximum Allowable Airspeed Pointer: The maximum allowa
23、ble airspeed pointer shall indicatethe maximum allowable airspeed in accordance with the following equations, or in accordancewith engineering data supplied by the purchaser.For altitudes from sea level to altitude where VM = Mm (Figure 1).V C PP VCM sooEMso= + +Ge7 Gf7 Ge9GebGeaGeaGeaGfaGfaGfaGe6Ge
24、8Ge7Ge7Ge7Gf6Gf8Gf7Gf7Gf7Ge9GebGeaGeaGeaGeaGeaGf9GfaGfaGfaGfaGfa21 1 5 1 1 12211 (Eq.2)For altitudes where Mm is limiting factor (Figure 1).V C PP MM soom= +Ge7 Gf7 Ge9GebGeaGeaGeaGfaGfaGfa+Ge6Ge8Ge7Ge7Ge7Gf6Gf8Gf7Gf7Gf7Ge9GebGeaGeaGeaGeaGeaGf9GfaGfaGfaGfaGfa21 112 1 1 12 11( ) (Eq.3)where:VM = Maxi
25、mum allowable indicated airspeed in KnotsMm = Maximum allowable Mach = Ratio of specific heats = 1.40 for airPo = Pressure at sea level = 29.92126 inches HgP = Ambient static pressure in inch HgCso = Speed of sound at sea level = 661.48 KnotsCs = Speed of sound at altitude in Knots = Density ratio a
26、t altitudeVEM = Maximum equivalent airspeed in KnotsMaximum equivalent airspeed and maximum allowable Mach to be specified by the purchaser.4.3 Limitation of Indicated Airspeed Pointer Movement:The pointer movement shall be limited by stops in the mechanism in such a way that a pointer willnot rotat
27、e more than 10 degrees beyond the last graduation on the dial. Stops may also beincorporated in the instrument mechanism to limit counterclockwise motion of the pointer.SAE AS437 Revision A- 6 -4.4 Case Markings:The outlets in the rear of the case shall be marked:“P” - Pitot pressure connection.“S”
28、- Static pressure connection.5. TEST CONDITIONS:5.1 Atmospheric Conditions:Unless specified otherwise, all tests required by the Aerospace Standard shall be conducted atan atmospheric pressure of approximately 29.92 inches of mercury, an ambient temperature ofapproximately 25 C and a relative humidi
29、ty of not greater than 85%. When tests are conductedwith the atmospheric pressure or the temperature substantially different from these values,allowance shall be made for the variation from the specified conditions.5.2 Vibration (to minimize friction):Unless specified otherwise, all tests for perfor
30、mance may be made while the instrument issubjected to a maximum vibration of 0.001 inch double amplitude at a frequency of 10 to 60cycles per second. The term double amplitude as used herein indicates the total displacementfrom positive maximum to negative maximum.5.3 Vibration Equipment:Vibration e
31、quipment shall be such as to allow vibration to be applied along each of three mutuallyperpendicular axes of the instrument at frequencies and amplitudes consistent with therequirements of paragraph 3.3.3.5.4 Position:Unless specified otherwise, all tests shall be made while the instrument is mounte
32、d in its normaloperating position.6. INDIVIDUAL PERFORMANCE REQUIREMENTS:All instruments shall be subjected to whatever tests the manufacturer deems necessary todemonstrate specific compliance with this Aerospace Standard, including the followingrequirements where applicable.6.1 Scale Error:During t
33、he 12 hour period immediately preceding the test, the instrument shall not have beenoperated or been subjected to atmospheric pressure conditions substantially different from thosespecified in paragraph 5.1.SAE AS437 Revision A- 7 -6.1.1 Airspeed Scale Error: The instrument shall be tested for scale
34、 errors at all points of the scaleindicated in Table 4. The tests shall be made by subjecting the instrument to the pressurespecified to produce these readings, first with pressure increasing, then with pressuredecreasing.With pressure increasing, the pressure shall be brought up to, but shall not e
35、xceed, thepressure specified to give the desired reading. With pressure decreasing, the pressure shall bebrought down to, but shall not fall below, the pressure specified to give the desired reading. The scale errors at the test points shall not exceed the tolerances specified in Table 4.6.1.2 Maxim
36、um Allowable Airspeed Scale Error: The maximum speed pointer shall be tested forscale errors at all points indicated in Table 6. The test shall be accomplished by subjecting theindicator to pressure (Altitudes) specified in Table 6. During this test, the pitot and staticconnections shall be connecte
37、d together to a standard mercury barometer and to sources ofvacuum and pressure. The reduction in pressure, as indicated by the barometer, shall be madeat a rate corresponding to an increase in altitude of approximately 3,000 feet per minute. Theindicator shall remain at the pressure corresponding t
38、o each test point for at least 1/2 minutebut not more than 5 minutes before a test reading is taken. The scale errors shall not exceedthe tolerances specified in Table 6. This test shall be combined with the hysteresis test.6.2 Hysteresis:Not more than 15 minutes after the indicator has been subject
39、ed to the pressure correspondingto the highest altitude specified in Table 6, the pressure shall be increased at a ratecorresponding to a decrease in altitude of approximately 3,000 feet per minute until the pressurecorresponding to the first test point specified in Table 5 is reached. The indicator
40、 shall remain atthis pressure for at least 5 minutes, but not more than 15 minutes, before the test reading istaken. After the reading has been taken, the pressure shall be further increased at the aboverate until the pressure corresponding to the second test point specified in Table 5 is reached. T
41、he indicator shall remain at the pressure for at least 1 minute, but not more than 10 minutes,before a test reading is taken. After the reading has been taken, the pressure shall be furtherincreased at the above rate until atmospheric pressure is reached. The reading of the maximumspeed pointer at e
42、ither of the two test points shall not differ from the corresponding reading, withdecreasing pressure, by more than the tolerances specified in Table 5.6.3 After Effect:Not less than 1 nor more than 5 minutes after the completion of the maximum speed scale errortest at room temperature, the maximum
43、speed pointer shall have returned to its original reading,corrected for any change in atmospheric pressure, within the tolerance specified in Table 5.SAE AS437 Revision A- 8 -6.4 Friction:6.4.1 Maximum Allowable Airspeed Pointer: The indicator shall be tested for friction at each pointindicated by a
44、n asterisk in Table 6. The pressure shall be decreased to bring the pointer to thedesired reading and held constant while the two readings are taken, the first before theindicator is vibrated and the second after the indicator is vibrated. The difference between anytwo readings shall not exceed the
45、tolerance specified. The pointer shall move smoothly whilethe pressure is varied uniformly without vibration of the indicator. This test may be combinedwith the test for scale error.6.4.2 Indicated Airspeed Pointer: The test specified for the maximum allowable airspeed pointer shallbe repeated for t
46、he indicated airspeed pointer except the pressure shall be increased instead ofdecreased and Table 4 shall apply instead of Table 6.6.5 Leak:6.5.1 Case Leak: The pitot and static pressure connections of the indicator shall be joined with a “Y”connection and shall be connected together to the same me
47、rcury manometer and sources ofsuction and pressure. A suction of 15 inches of mercury shall be applied to the pitot and staticpressure connections of the indicator. While the source is disconnected for a period of 1minute, the difference between the mercury levels in the manometer shall not change b
48、y morethan 0.05 inch.6.5.2 Airspeed Diaphragm Leak: While the static pressure connection is open to atmosphere, apressure sufficient to produce approximately full scale deflection of the indicated airspeedpointer shall be applied to the pitot connection of the indicator, at which point the connectio
49、ntubing shall be pinched off or otherwise completely sealed. During a period of 1 minute thereshall be no apparent change in pointer position.7. QUALIFICATION TESTS:As many instruments as deemed necessary by the manufacturer to demonstrate that allinstruments will comply with the requirements of this section shall be tested in accordance with hisrecommendations.7.1 Temperature Characteristics:7.1.1 Low Temperature Operations: The instrument shall be subjected to the applicable low ambienttemperature listed in column A of paragraph 3.3.1 for a
