1、BRITISH STANDARD BS 2G 115:1956 Incorporating Amendment No.1 Specification for Sensitive altimeters for aircraftBS 2G 115:1956 This British Standard, having been approved by the AircraftIndustry Standards Committeeand endorsed bytheChairman ofthe EngineeringDivisional Council,was published underthea
2、uthority of the GeneralCouncil of the Institutionon 12December1956 BSI 01-2000 The following BSI references relate to the work on this standard: Committee referenceACE/30 Draft for commentCV(ACE)8908 ISBN 0 580 34121 6 Amendments issued since publication Amd. No. Date of issue Comments 1174 May1973
3、Indicated by a sideline in the marginBS 2G 115:1956 BSI 01-2000 i Contents Page Foreword ii 1 Scope 1 2 Definitions 1 Section 1. General requirements 3 Preferred size 1 4 Preferred units of measurement 1 5 General construction 1 Section 2. Particular requirements 6 Detailed construction 1 7 Calibrat
4、ion 2 Section 3. Tests 8 General 2 9 Ranging test 2 10 Hysteresis test 2 11 Friction test 2 12 Position test 2 13 Temperature test 3 14 Leakage test 3 15 Zero adjustment test 3 16 Pressure test 3 17 Vibration test 3 18 Acceleration test 3 19 Climatic tests 3 20 Routine production tests 3 Appendix A
5、Serviceability tests 4 Appendix B Corrections for temperature and gravity to be applied when using Kew pattern mercury test barometers having inch scales, standard at62 F (16.7 C), for calibrating altimeters 5 Table 1 Permissible errors 4 Table 2 4 Table 3 Fiducial temperatures in C for various lati
6、tudes and heights above mean sea level 6 Table 4 Temperature correction factors 7BS 2G 115:1956 ii BSI 01-2000 Foreword This revised British Standard has been prepared principally on account of the introduction of the International Civil Aviation Organization (I.C.A.O.) Standard Atmosphere 1)which s
7、upersedes the I.C.A.N. (International Commission for Air Navigation) relationship between static pressure and height to which these instruments were formerly calibrated. The tabulated pressure-height tables are accordingly revised and barometric data is quoted in accordance with BS2520, “Barometer c
8、onventions and tables”. In view of the fact that test barometers having scales to standards other than BS2520 are likely to remain in use for some years, AppendixA of BSG 115:1949, containing instructions for the correction of barometers having inch scales related to London laboratory conditions, is
9、 retained in this revision as Appendix B with appropriately amended pressure-height tables. The table of fiducial temperatures for various latitudes and heights above mean sea level has been modified as a result of changes in the formulae for establishing gravity corrections. The comparable informat
10、ion for barometers in accordance with BS2520 is given in that specification. Since the maximum difference between corresponding pressure values in the I.C.A.N. and I.C.A.O. conventions over the range covered in this BritishStandard is0.05millibars, the revised pressure-altitude tables have little ef
11、fect on the design or calibration of the instruments. Information has been included relating to the incidence of testing and a friction test has been added. Recommendations for minimum tests to verify serviceability have been included. The presentation of ground pressure has been restricted to the d
12、rum counter method. 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 from legal obligations. Summary of pages This
13、 document comprises a front cover, an inside front cover, pagesi andii, pages1to7 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 table on the inside front cover. 1) I.C.A.O. Document No.7488, “Ma
14、nual of the I.C.A.O. Standard Atmosphere”, (H.M.S.O.).BS 2G 115:1956 BSI 01-2000 1 1 Scope This British Standard specifies the design and performance requirements for sensitive altimeters for aircraft. It is applicable to mechanical instruments operated directly by an aneroid barometer movement. The
15、 performance requirements are based on tworanges 1000to35000ft and 1000to50000ft respectively. 2 Definitions For the purposes of this British Standard the following definitions shall apply: 2.1 sensitive altimeter an instrument used in aircraft to indicate the height of the aircraft in accordance wi
16、th the I.C.A.O. relationship between static pressure and height 2.2 sensitive instrument an instrument provided with a ground pressure scale or means of adjusting to prevailing ground pressure, and in which the presentation of the reading is of high magnification, such that the instrument can be rea
17、d easily to20feet, either by means of multiple pointers, subsidiary multiple scales, or similar devices Section 1. General requirements 3 Preferred size The preferred size is that of aircraft instrument case, Type1, as specified in BSG 100,“General requirements for electrical equipment and indicatin
18、g instruments for aircraft”. 4 Preferred units of measurement The preferred units of measurement are: a) Feet, in accordance with BSA 22. b) Ground pressure millibars, in accordance withBS2520. 5 General construction The construction of the instrument shall be mechanically sound, suitable for its pu
19、rpose, and in accordance with the requirements ofBSG 100, with respect to climatic proofing, temperature performance, and ability to withstand aircraft vibration. Section 2. Particular requirements 6 Detailed construction a) The instrument shall consist of an aneroid barometer having a scale graduat
20、ed in terms of altitude according to the relationship specified in Clause7. b) The detailed construction of the instrument shall be in accordance with relevant requirements of BSG100. c) The means of indicating ground pressure shall be such that the value in millibars is presented as the only visibl
21、e figure,e.g.by counters or similar means. The ground pressure setting shall have a range from800 to1050millibars. d) The ground pressure setting shall be moved by an adjusting knob or adjusting means readily accessible from the front of the instrument. e) The adjusting means shall be geared to the
22、pointers or height indicating means and to the ground pressure setting, which shall move in correct relationship to each other within the limits permitted in Clause15. Rotation of the adjusting means in a clockwise direction shall decrease the millibar reading on the ground pressure setting, the fig
23、ures moving upwards. NOTEAlthough instruments designed in accordance with this requirement continue to be acceptable, the agreed current practice is that clockwise movement will increase the millibar reading on the ground pressure setting, the figures moving downwards. f) In order to adjust the rela
24、tionship between the pointers or height indicating means and the ground pressure setting, means shall be provided for disengaging one of these from the ground pressure setting adjusting means so that the latter moves either the height indication or the ground pressure indication only. This adjustmen
25、t shall be capable of being sealed. g) In the design and construction of the movement all steps compatible with the instrument being adequately robust shall be taken to minimize friction, hysteresis and temperature errors. h) If stops are fitted they shall come into operation above the maximum scale
26、 readings of the instrument.BS 2G 115:1956 2 BSI 01-2000 7 Calibration a) The relationship between height and pressure to which the instruments are calibrated shall be in accordance with the general formulae stated in Paragraph3 of I.C.A.O. Document7488 for the troposphere and stratosphere respectiv
27、ely over the ranges appropriate to the ranges of height covered by instruments to this British Standard. The I.C.A.O. troposphere is postulated to extend to a geopotential (altitude) of36089ft 2)(the tropopause). The pressure values corresponding to heights in feet over the ranges covered by this sp
28、ecification are given inTable 1, in millibars. b) When barometers graduated in accordance with the conventions ofBS2520 are used for testing under conditions of local temperature and gravity other than the reference conditions of the barometer, appropriate corrections in accordance withBS2520 shall
29、be applied 3) . In order to obtain the readings of such a barometer which correctly represent the pressures corresponding to the I.C.A.O. altitudes the temperature and gravity corrections inBS2520 should be applied, with reversed signs, to the values inTable 1, Column2. c) The I.C.A.O. standard grou
30、nd pressure is1013.25millibars. Section 3. Tests 8 General a) Tests shall be made to prove compliance with all the requirements of this British Standard. It is not intended or recommended that complete tests shall be made on every instrument supplied. Two kinds of test, therefore, are specified as f
31、ollows: Type tests (Clauses9 to19) which shall be made in that order on the same instrument, on representative samples of each particular design and range of instrument. Routine production tests (Clause20) which shall be made on every instrument manufactured in accordance with the BritishStandard. b
32、) The minimum tests recommended to verify the serviceability of instruments manufactured in compliance with this British Standard are indicated inAppendix A. c) Sufficient agitation shall be applied to the instruments during the performance tests, except the friction test specified in Clause11, to r
33、emove the effects of friction. d) No pressure cycle or exercizing other than that produced by the normal variation of terrestrial barometric pressure shall be applied to the instruments for a period of not less than16hours before ranging or recheck calibration tests are performed. Type tests 9 Rangi
34、ng test With the ground pressure set to1013.25millibars and with the instrument in the normal position with the dial upright and in a vertical plane, the errors shall not exceed the amounts specified inTable 1 appropriate to the range of the instrument, irrespective of whether pressure is decreasing
35、 or increasing at a rate equivalent to not less than1000ft/min. 10 Hysteresis test The hysteresis, as shown by the difference between the errors at the same barometric pressure, with pressure decreasing and increasing in the ranging test, shall not exceed150ft, up to and including30000ft, and250ft a
36、bove30000ft. 11 Friction test The pressure shall be adjusted to bring the pointers approximately to the desired reading and then shall be held constant; the altimeter meanwhile being carefully insulated from vibration. Two readings shall then be taken, the first whilst the altimeter remains undistur
37、bed and the second after the instrument has been tapped until the pointer no longer moves. The difference between the two readings shall not exceed the tolerances listed inTable 2. This test may be combined with the normal ranging test but shall in any event be performed with both increasing and dec
38、reasing pressure. Other points may be tested with tolerances interpolated fromTable 2. 12 Position test The errors shall not exceed those laid down in Table 1 when the instrument is tilted90 in any direction from the normal position. 2) To the nearest foot. 3) Corrections to be applied to Kew Type R
39、.A.F. Mk.1A and1B mercury barometers having inch scales referred to London laboratory conditions are given inAppendix B to this specification.BS 2G 115:1956 BSI 01-2000 3 13 Temperature test The instrument shall be tested throughout its range at20 C and up to8000ft at+35 C. The errors shall not exce
40、ed the amounts specified inTable 1 except that the tolerances between1000 and+1000ft shall be increased to 70ft. In addition, the instrument shall function without derangement, and the ground pressure setting means shall work freely and correctly, over the whole range of the ground pressure scale at
41、40 C and+70 C. After these tests the instrument shall still comply with the accuracy requirements of Clause9. 14 Leakage test The pointers shall be set to indicate zero. Suction shall be applied sufficient to move the pointers to5000ft and then shut off. There shall be no change in the height indica
42、tion during the ensuing minute. 15 Zero adjustment test The relationship between the ground pressure setting and the height indications shall be such that when the ground pressure value is adjusted by means of the setting knob to a given reading, and the corresponding pressure is applied to the stat
43、ic connection, the height indication shall be0ft with a tolerance of+30ft,45ft. This test shall be applied atat least six points selected at random and widely disposed over the whole range of ground pressure setting. In performing the test, the reference pressure shall be applied first and the groun
44、d pressure counter brought to the corresponding reading by rotating the setting knob, readings being taken when the value is approached from either direction. 16 Pressure test If the instrument is intended for use in pressure cabin aircraft it shall withstand an external pressure difference of15poun
45、ds per square inch above that of the interior without failure. The height indication shall not change under these circumstances. The test shall be performed in a pressure chamber with the static connection of the instrument blanked off and positive pressure applied to the outside of the case. 17 Vib
46、ration test The instrument shall show no errors outside the tolerance specified in Clause9 when subjected to the varying frequency vibration tests specified in BSG 100 relevant to its installation position in the aircraft, and any pointer oscillation shall be within the limits permitted therein. The
47、 instrument shall also withstand any appropriate endurance vibration test laid down in the same standard without damage or derangement. 18 Acceleration test The instrument shall be subjected to the grade of acceleration test specified inBSG 100 appropriate to the performance grading declared by the
48、manufacturer. 19 Climatic tests The instrument shall be subjected to the climatic tests specified in BSG 100 appropriate to the performance grading declared by the manufacturer. During these tests the instrument shall respond qualitatively and shall subsequently comply with the requirements of the r
49、anging, hysteresis, friction and leakage tests specified in Clauses9 to11 and Clauses14 or16 as appropriate. For the purpose of these tests the static connection of the instrument shall be connected to a20ft length of 1 / 4 in. bore static tubing. The tubing shall be coiled with the open end exposed within, but not lying flat upon the floor of, the test chamber. The maximum altitude rating governing the reduced atmospheric pressure applied during the specified periods as defined inBSG 100, Clause25.2.1 b) shall be taken as the maximum of the appropriate r
