1、BRITISH STANDARD AEROSPACE SERIES BS 2G 201: 1996 Specification for Counter and pointer pressure altimeters ICS 49.090BS2G201:1996 This British Standard, having been prepared under the directionof the Engineering SectorBoard, was published underthe authority of the Standards Board and comes intoeffe
2、ct on 15 July 1996 BSI 11-1999 First published December 1967 Second edition The following BSI references relate to the work on this standard: Committee reference ACE/6 Draft for comment 95/700909 DC ISBN 0 580 25480 1 Committees responsible for this British Standard The preparation of this British S
3、tandard was entrusted to Technical Committee ACE/6, Aerospace avionic, electrical and fibre optic technology, upon which the following bodies were represented: British Airways British Cable Makers Confederation British Rubber Manufacturers Association Civil Aviation Authority (Airworthiness Division
4、) Federation of the Electronics Industry Ministry of Defence Society of British Aerospace Companies Amendments issued since publication Amd. No. Date CommentsBS2G201:1996 BSI 11-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Normative references 1 3 Constructi
5、on 1 4 Tests 2 Annex A (informative) Examples of counter and pointer pressure altimeterpresentation conforming to recommendations of the report of theUnitedKingdom altimeter committee 6 Annex B (informative) International Standard atmosphere 7 Annex C (informative) Serviceability tests 8 Figure A.1
6、Typical altimeter faces 6 Table 1 Permissible errors 2 Table 2 Ground pressure scale test points 3 Table 3 Friction 4 Table B.1 Standard atmosphere 7 List of references Inside back coverBS2G201:1996 ii BSI 11-1999 Foreword This British Standard has been prepared by Technical Committee ACE/6 and is a
7、 revision of BSG201:1967 which is superseded and withdrawn. It specifies pressure altimeters, calibrated in feet, suitable for indications up to50000ft. This revision brings the standard up to date and corrects the value for air pressure at4000ft. The requirements of this standard conform to the rec
8、ommendations contained in the report of the UnitedKingdom Altimeter Committee relating to presentation, examples of which are shown inFigure A.1 (seeAnnex A). A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for the
9、ir correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to8, an inside back cover and a back cover. This standard has been updated (see co
10、pyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS2G201:1996 BSI 11-1999 1 1 Scope This British Standard specifies the general design and performance requirements for pressure altimeters having a combined counter and sin
11、gle pointer presentation in two forms as follows. a) Type A. A panel-mounting indicator operating from any form of remote altitude transducer. b) Type B. A panel-mounting indicator containing its own sensing mechanism inside the case. The standard provides for instruments operating over an indicated
12、 range of1000ft to+50000ft (geopotential). The design may include provision for applying corrections to the aircraft static pressure system error. 2 Normative references This British Standard incorporates, by dated or undated reference, provisions from other publications. These normative references
13、are made at the appropriate places in the text and the cited publications are listed on the inside back cover. For dated references, only the edition cited applies; any subsequent amendments to or revisions of the cited publication apply to this British Standard only when incorporated in the referen
14、ce by amendment or revision. For undated references, the latest edition of the cited publication applies, together with any amendments. 3 Construction 3.1 General The design and construction of the indicator shall conform to the relevant requirements of BSG100 and BSG101. NOTEThe preferred case size
15、s for the indicators are the types5 and8 cases and 4-inch square cases as shown in BSG101. 3.2 Particular 3.2.1 The detailed construction and dial markings of the indicator shall conform to BSG100 and BSG101. 3.2.2 When transmission of electric signals from a remote mounted sensing mechanism is used
16、, the transmission signals shall conform to BSG183. 3.2.3 The value of the ground pressure shall be shown on counters clearly visible on the face of the indicator. The range of the ground pressure setting shall be from800mbar 1)to1050mbar. The marking shall be in millibars, and in inches of mercury
17、if required, conforming to BS2520 where a display of ground pressure setting in inches of mercury is required. 3.2.4 The ground pressure setting shall be moved by an adjusting knob readily accessible from the front of the indicator. Rotation of the knob in a clockwise direction shall increase the gr
18、ound pressure reading on the setting counters, the numerals moving downwards. A datum mark shall be provided on the millibar scale to ensure that the indicated value of1013.25 mbar can be accurately set. 3.2.5 Any pre-set device fitted for adjustment of the relationship between the ground pressure s
19、etting and the altitude indication shall be such that the relationship which is set up is not capable of being inadvertently disturbed. The device shall not be accessible from the front of the indicator and the total possible correction shall not exceed a range of 3mbar. 3.2.6 The pointer shall make
20、 one revolution per1000ft clockwise for increasing altitude. 3.2.7 Numerals on the height indicating counters shall move downwards for an increase in indication. 3.2.8 If the altimeter includes mechanical reversion or electrical assistance, when operated in the reverted state, the permissible errors
21、 shall not exceed those specified in BSG115. 3.2.9 Warning flags provided to give an indication of malfunction shall be legible. 3.2.10 The relationship between the movement of the counters and the movement of the pointer shall be such as to ensure that the1000ft digit of the counter changes during
22、the interval when the pointer travels between the “950” and “0” scale marks on the dial with altitude readings either increasing or decreasing. 3.2.11 The response rate shall be such that the rate of follow of the indicator is not less than70000ft per minute. 3.2.12 The servo system, when fitted, sh
23、all be damped. 3.2.13 The threshold of the indicator and its associated sensing mechanism shall be such that low changes of pressure applied to the sensor at any altitude will result in movement of the pointer. 1) 1mbar=100N/m 2 =100Pa.BS2G201:1996 2 BSI 11-1999 3.2.14 Any mechanism provided within
24、the indicator to generate static pressure error corrections to the indicating mechanism and/or altitude measuring mechanism, shall not introduce an error of more than an equivalent 0.5mbar outside the permissible errors quoted inTable 1 above5000ft. Below5000ft any error due to the pressure error co
25、rrection mechanism shall not cause the indicator to read outside the permissible errors quoted inTable 1. Table 1 Permissible errors 3.3 Calibration Calibration of the sensing mechanisms and of the ground pressure adjustment system with which these counter/pointer altimeter indicators operate shall
26、be to the ICAO standard atmosphere. NOTE 1A table of values for the standard atmosphere up to45000ft is given inTable B.1 and Annex B. NOTE 2Pressure values corresponding to heights in feet over the ranges covered by this specification and the required accuracy are given inTable 1 in millibars. 4 Te
27、sts 4.1 General 4.1.1 Tests shall be made on both type A and type B indicators to prove conformance to the requirements of this British Standard. For type A indicators the manufacturer shall declare the performance and accuracy requirements of the remote altitude transducers to be used with the indi
28、cator. NOTE 1It is not intended or recommended that complete tests should be made on every indicator supplied. Three kinds of test 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 manufacture
29、d in accordance with the standard. c) Production quality tests. To be made on samples as specified in the individual specification. NOTE 2For the guidance of users, minimum tests recommended to verify the serviceability of indicators manufactured conforming to this British Standard are indicated inA
30、nnex C. 4.1.2 Vibration not exceeding0.2g shall be applied to the indicators during the performance tests, except the friction test specified in4.2 and4.3. NOTEVibration of this order is attainable with a total amplitude of0.04mm and a frequency of50Hz. 4.1.3 Pressure cycling or exercising other tha
31、n that produced by normal variation of terrestrial barometric pressure shall be applied to the indicators for a period of not less than16h before the ranging tests are performed. 4.1.4 Readings taken from barometers used to test the altimeters shall be corrected for latitude and temperature as speci
32、fied in BS2520. 4.1.5 Unless otherwise specified, tests shall be made at a temperature of (20 5) C. 4.1.6 The reference standard for atmospheric pressure shall be a mercury barometer which is certified at least once every two years by the competent authority to be accurate, with corrections, to with
33、in 0.2mbar. NOTE 1A reference barometer newly introduced into service should be checked at intervals of approximately six months until the stability of its calibration has been established. NOTE 2Unless extreme care is taken in reading the reference barometer, the error introduced may exceed some of
34、 the tolerances specified in this test procedure. 4.2 Type tests 4.2.1 Ranging, accuracy and hysteresis test With the ground pressure set to1013.25 mbar and with the indicator in the normal position with the dial upright and in a vertical plane, the errors shall not exceed the amounts specified inTa
35、ble 1. The test shall be made with pressure decreasing at approximately3000ft per minute and with pressure increasing at approximately6000ft per minute. The rate of change of pressure shall be reduced progressively as the test points (seeTable 2) are approached to avoid passing the test point. Movem
36、ent of the pointer during decreasing as well as increasing pressure shall be smooth and free from irregular motion when the pressure is changed uniformly. Altitude Pressure Permissible errors at +20 5 C 1 mbar expressed in feet ft 1 000 mbar mbar 1 1050.40 0 1013.25 27.3 1 977.16 28.1 2 942.13 30 3
37、908.12 4 875.00 5 843.07 31.6 10 696.81 35 36.9 20 465.63 50 51.2 30 300.89 73 73 40 187.54 110 110.9 50 115.98 180 179.4 NOTENo static error correction applied.BS2G201:1996 BSI 11-1999 3 NOTEThis is a combined test in which ranging accuracy and hysteresis are established in one test. Other specific
38、ations for similar equipments frequently show these two items as separate tests. Table 2 Ground pressure scale test points 4.2.2 Static pressure error correction test (if applicable) NOTEThis test may be incorporated as part of the ranging test of4.2.1 or made separately, as required by the individu
39、al specification. Combinations of pitot pressure and altitude shall be applied as follows: a) if made in combination with the test in4.2.1 the overall error in indication shall not exceed1.5mbar above an altitude of5000ft or the tolerances ofTable 1 below5000ft; b) if made separately the difference
40、in corrected and uncorrected indications shall not be greater than the nominal correction 0.5mbar, except that below5000ft the indications as corrected shall not exceed the tolerances shown inTable 1. 4.2.3 Damping The damping of indication shall be such that with rapid changes of pressure between s
41、ea level and3000ft and between40000ft and50000ft per minute increasing or decreasing, the pointer shall settle at the new position after not more than three cycles having a maximum amplitude of50ft, peak to peak. 4.2.4 Ground pressure scale test The indicator shall be tested at the five points in th
42、e millibar setting range specified inTable 2; each test point shall be approached as follows: a) pressure increasing with the baroscale knob turned clockwise and counter-clockwise; b) pressure decreasing with the baroscale knob turned clockwise and counter-clockwise. NOTEThis ensures that any hyster
43、esis effects in the ground pressure setting mechanism are known. At each of the pressure values specified inTable 2 the pointer shall indicate zero within 35ft when the corresponding setting is made on the ground pressure scale and the appropriate barometer corrections have been applied. 4.2.5 Instr
44、ument position error test With atmospheric pressure applied to the indicator, the difference between the pointer indication when the indicator is in the normal operating position and when it is in any other position shall not exceed 20ft. 4.2.6 Leak test With the pointer set to indicate zero, suctio
45、n shall be applied sufficient to move the counter and pointer to5000ft indicated and then shut off. The isolation shall be applied as close to the instrument as possible. There shall be no change in height indication in excess of10ft during the ensuing minute. The following test shall be made on the
46、 pitot pressure section of indicators incorporating PE (position error) correction sensing mechanism within the indicator case. a) Apply a pressure equivalent to300knots to the pitot connection and then shut off the air. The applied pressure, when it is stabilized, shall be measured and there shall
47、be no change of pressure after1min. b) If the indicator is a read-out unit from a remote transducer it shall be suitably tested to establish that changes of ambient pressures experienced over the altitude range do not result in deformation, or degrading of the accuracy, of the complete transducer in
48、dicator. 4.2.7 Drift test and after effect The following tests shall be applied to the indicator, in the sequence shown, to establish drift and after effect. a) Establish a datum pressure approximately corresponding to sea level and note the pressure and the indicated altitude. b) Decrease the press
49、ure to approximately30000ft and hold for4h. The readings at the beginning and the end of the test shall be within the tolerances quoted inTable 1. The maximum difference between the two readings shall be50ft. c) Immediately on completion of test2 increase the pressure at20000ft per minute to the original datum pressure. The reading shall be within30ft of the reading taken at the commencement of the test. mbar in 800 23.50 900 26.00 1 000 28.50 1013:25 29.92 1 050 31.00 NOTEOn indicators with ground pressure setting in inches of me
