1、BRITISH STANDARD AEROSPACE SERIES BS 2G 182: 1975 (Superseding BSG182) Specification for Pressure-driven machmeters for aircraft UDC 629.7.054845 852BS2G182:1975 This British Standard, having been approved by the AerospaceIndustry Standards Committee, was published underthe authority of the Executiv
2、e Board on 31October1975 BSI 04-2000 The following BSI references relate to the work on this standard: Committee reference ACE/30 Draft for comment 72/37616 DC ISBN 0 580 08964 9 Foreword This revision of BSG182:1963 has been prepared to cover the requirements of pressure-driven machmeters having cl
3、osely controlled performance over specified parts of the range. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity f
4、rom legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment
5、 table on the inside front cover. Amendments issued since publication Amd. No. Date CommentsBS2G182:1975 BSI 04-2000 i Contents Page Foreword Inside front cover 1 Scope 1 2 References 1 3 Definitions 1 4 General construction 1 5 Particular requirements 1 6 Declarations 2 7 Tests 2 Appendix A Service
6、ability tests Inside back cover Table 1 Calibration points and tolerances 4ii blankBS2G182:1975 BSI 04-2000 1 1 Scope This British Standard specifies the general design requirements and test procedures for machmeters of the following types. 1.1 Type A. Machmeter indicating a Mach scale range of at l
7、east0.5M up to a maximum scale reading of1.0M and of altitude range up to50000ft, with maximum accuracy from20000ft to40000ft, unless otherwise required by the individual specification. 1.2 Type B. Machmeter indicating a range extending above1.0M and of altitude range up to60000ft with maximum accur
8、acy in the region between the altitude limits20000ft and40000ft and in the indicated range of0.7M to0.9M. 2 References This standard makes reference to the following British Standards. BS 185, Glossary of aeronautical and astronautical terms. BS 3G 100, General requirements for equipment for use in
9、aircraft. BS 2G 101, General requirements for aircraft indicators. BS G 199, Tables relating pressure to altitudes, airspeeds and Mach numbers for use in aeronautical instrument design and calibration. The latest issues of these standards shall be used. 3 Definitions For the purposes of this British
10、 Standard the definitions given in BS185 and the following shall apply. 3.1 machmeter an instrument used in an aircraft to give an indication of Mach number as derived from pitot and static pressures in accordance with the relationship defined in BSG199 3.2 machmeter scale range the difference betwe
11、en the lowest calibrated Mach number and highest calibrated Mach number 4 General construction 4.1 The design and construction of the indicator shall comply with the relevant requirements of BS3G100 and BS2G101. 4.2 The preferred cases are the type3 and type6 cases shown in BS2G101. 5 Particular req
12、uirements 5.1 Construction 5.1.1 The indicator shall contain a differential pressure-measuring mechanism driving the indication through a suitable linkage and a static pressure-measuring mechanism which modifies the magnification of the output of the differential pressure-measuring mechanism accordi
13、ng to the static pressure. 5.1.2 The indicator dial shall be marked in whole numbers and decimals of Mach number except that the zero shall not be used before the decimal point for subsonic speeds. The marking shall conform with the requirements of BS2G101. 5.1.3 With no differential pressure applie
14、d, the pointer shall rest at least10 off scale. The calibration characteristics shall be nominally linear over the circular scale, the largest and smallest interval for0.1M being within20% of the mean. NOTESpecific requirements for alternative presentation, i.e.counters or tape, will be defined in t
15、he individual specification. 5.1.4 When a lubber or cursor is used to indicate an aircraft limitation it shall not be capable of adjustment in flight. 5.1.5 The indicator shall be capable of withstanding a reverse pressure (i.e.S P) of10mbar 1)without the calibration being affected. 5.1.6 The instru
16、ment case shall be airtight in accordance with BS2G101. 5.1.7 A warning label stating the limiting differential pressures shall be securely fixed near to the pressure connections. 5.1.8 The pitot and static connections shall conform to the requirements of BS2G101 and shall be indelibly marked P and
17、S respectively. 1) 1mbar=10 2 N/m 2 =0.1kPa.BS2G182:1975 2 BSI 04-2000 5.2 Calibration 5.2.1 The calibration of the indicator over the declared range shall be in accordance with the following as appropriate. 5.2.1.1 Type A. The indicator shall be calibrated at the points indicated inTable 1 and shal
18、l be within the tolerances stated. In addition the indicator shall be calibrated at every altitude level within the range ofTable 1 at the extremeties of its scale range. Production tests, which will normally include at least half of these test points, shall be specified in the individual specificat
19、ion. 5.2.1.2 Type B. Indicators indicating from0.5M to1.5M shall be calibrated in accordance withTable 1 to the tolerances specified. Indicators indicating from W 0.5M tou 1.5M shall be calibrated in accordance withTable 1 as appropriate but additional points shall be tested so that, during the type
20、 and production testing, each altitude level of10000ft up to and including50000ft is tested at least twice, one pressure setting being used within each interval equivalent to50knot indicated airspeed between150knot and700knot indicated airspeed. Indicators indicating from1.5M shall be calibrated usi
21、ng points selected in accordance with the principles outlined in the foregoing paragraph, each increment of0.1M being included in the schedule. For indicators with a scale range (see3.2) 1.0M the tolerance 0.0075M may be relaxed to 0.75% scale range. Additionally, for indicators with a scale range1.
22、4M the tolerance 0.02M may be relaxedto 1.4% scale range. The individual specification shall detail the appropriate tolerance if calibration points are required below the equivalent of150knot indicated airspeed. The individual specification may require a special calibration tolerance at one particul
23、ar Mach number to approach parity with, for example, independent speed warning devices. 5.2.2 The relationship between altitude and dynamic pressure to which the instruments are calibrated shall be in accordance with BSG199. NOTEWhere the individual specification requires the calibration of the inst
24、rument to deviate from5.2.2 to provide some degree of static pressure error compensation, the equivalent tolerances specified in5.2.1 shall be maintained. 6 Declarations In addition to the declarations required by BS3G100-1, the manufacturer shall declare: a) the limiting Mach number range; b) the l
25、imiting altitude; c) the limiting P-S pressure; d) if static pressure error compensation is incorporated, the name and type of aircraft for which the compensation is designed. 7 Tests 7.1 General 7.1.1 Tests shall be made to prove compliance with all the requirements of this British Standard. It is
26、not intended or recommended that complete tests shall be made on every indicator supplied. Three kinds of tests, therefore, are specified as follows: a) type tests, to be made on representative samples to prove the design; b) production routine tests, to be made on all indicators manufactured in acc
27、ordance with this standard; c) production quality tests, to be made on samples as specified in the individual specification. 7.1.2 For the guidance of users, minimum tests recommended to verify the serviceability of indicators manufactured in compliance with this British Standard are indicated inApp
28、endix A. NOTETo obtain the best measurement of calibration errors, it is recommended that the static pressure should be set accurately and the pitot pressure adjusted to provide the precise information. The differential pressure P-S is measured and compared with the required pressure taken from the
29、appropriate columns of q cinTable3 of BSG199. The tolerance may be converted by linearly interpolating with respect to Mach number the figures of q cfrom the appropriate column for each calibration point. 7.2 Type tests 7.2.1 Ranging accuracy test. The indicator shall be tested over the declared ran
30、ge at a temperature of20 5 C with increasing and decreasing pitot pressures. Unless otherwise specified, vibration not exceeding0.2g shall be applied to the indicator during the test to minimise friction. NOTE 1Vibration of this order is attainable with a total amplitude of0.04mm at a frequency of50
31、Hz. NOTE 2On a number of modern aircraft, the temperature behind the instrument panel will be above the+20 C temperature at which tests are made in accordance with this specification and normal performance may be required in such circumstances at+40 C. Where required, this will be stated in the indi
32、vidual specification and the performance of the indicator at such temperature has to be declared.BS2G182:1975 BSI 04-2000 3 The errors of indicated Mach number shall not be greater than those specified in5.2.1. 7.2.2 Friction test. At three widely spaced increments on the scale range at any altitude
33、 between25000ft and30000ft, the static and pitot pressures shall be adjusted approximately to the desired reading and then held constant, the indicator being carefully isolated from vibration. Two readings shall then be taken for each operation, the first whilst the indicator remains undisturbed and
34、 the second after the indicator has been tapped until the pointer no longer moves. The following tests shall be carried out at each of the three indications: a) increase P, hold: increase S, hold: read: tap: read. b) increase P, hold: decrease S, hold: read: tap: read. c) decrease P, hold: increase
35、S, hold: read: tap: read. d) decrease P, hold: decrease S, hold: read: tap: read. The difference between any pair of readings shall not exceed0.005M or0.5% of scale range, whichever is greater. The test may be combined with normal ranging and calibration and testsa) tod) may be carried out in any se
36、quence. 7.2.3 Position test. At two widely spaced points on the scale range and at two widely spaced increments on the altitude range (neither exceeding40000ft) (total: four test points), the change in reading when the indicator is turned through90 in any direction from the declared installed positi
37、on shall not exceed0.01M or the normal calibration tolerance, whichever is the greater, from the reading in the normal position. 7.2.4 Temperature-pressure tests. These tests shall be conducted in accordance with the requirements of BS3G100-2.3.2 appropriate to the classification and grading declare
38、d in the individual indicator specification. Unless otherwise stated, additional tolerances shall not be greater than the normal tolerance or0.01M, whichever is less, for temperatures of20 C and+50 C. 7.2.5 Overload test. The indicator shall not be deranged by subjection to the overload pressures sp
39、ecified in the individual specification for five minutes. Readings taken immediately afterwards, with decreasing pitot pressures and with a static pressure corresponding to an altitude of30000ft, shall be such that the errors do not exceed the ranging errors specified in5.2.1. 7.2.6 Leakage test 7.2
40、.6.1 With the pitot connection blanked off and thestatic connection open to atmosphere, the indicator shall comply with the requirements ofBS2G101, 3.10. 7.2.6.2 The maximum pressure shall be applied to the pitot connection and then slowly reduced until a precise indication is achieved. The air shal
41、l then be shut off. The indication shall not change for a period of one minute, during which time the temperature shall remain constant. 7.2.7 Fouling test. Any lubber or cursor shall be checked at all positions within its range to verify that no fouling takes place that can affect the indication. 7
42、.2.8 Vibration tests. Vibration tests shall be conducted in accordance with the requirements of BS3G100-2.3.1, in particular3.4 orB.4.2. The accuracy of the indication shall comply with5.2.1, and the magnitude of the oscillation of the indication shall be within the overall tolerance, unless otherwi
43、se stated in the individual specification. 7.2.9 Acceleration tests. Acceleration tests shall be conducted in accordance with the general requirements of BS3G100-2.3.6 and the particular requirements of the individual specification which shall define the acceleration levels and the indicator toleran
44、ces for this test, which shall in no case exceed0.01M/g for altitudes at or below40000ft. 7.2.10 Additional environmental tests. The indicator shall be subjected to additional environmental tests specified in BS3G100-2, as required by the individual specification. The required functioning tests shal
45、l be the ranging accuracy test at three points spaced equally over the indicated range, each at three equally spaced altitudes up to40000ft to the tolerances stated in5.2 and7.2.4 as appropriate. 7.3 Production routine tests 7.3.1 Ranging accuracy, friction, position, overload, leakage and lubber ma
46、rk tests. Each indicator shall satisfactorily fulfil the requirements of the tests specified in7.2.1, 7.2.2, 7.2.3, 7.2.5, 7.2.6, and7.2.7, except that the ranging and accuracy tests shall be at the points and to the tolerances specified in5.2.1. 7.4 Production quality tests 7.4.1 Sample indicators,
47、 selected and tested in accordance with the individual specification, shall satisfactorily fulfil the requirements of the tests specified in7.2.8 (resonance search only) and7.4.2.BS2G182:1975 4 BSI 04-2000 7.4.2 At temperatures of20 C and+50 C the errors in indicated Mach number shall not exceed1.5t
48、imes the tolerances specified in7.2.1. After subjection to temperatures of62 C and+85 C, the indicator shall not be deranged nor shall the calibration errors be outside normal tolerances, and the indicator shall satisfy the requirements of the pressure test specified in7.2.5. Table 1 Calibration poi
49、nts and tolerancesBS2G182:1975 BSI 04-2000 Appendix A Serviceability tests The minimum tests recommended to verify the serviceability of instruments manufactured in compliance with this British Standard are as follows. A.1 Ranging accuracy test (7.2.1) At those Mach numbers recommended for production tests in5.2.1 at the following altitudes: 0ft, 20000ft, 30000ft, 40000ft, 50000ft. The indicated Mach number should be within the appropriate tolerances shown inTable 1. A.2 Fouling test (7.2.7) A.3 Leakage test (7.2.6) A.4 Friction test (7.2.2)BS 2G 182: 1
