1、BRITISH STANDARD AEROSPACE SERIES BS 2G 117: 1975 (Superseding BSG117) Specification for Pressure-driven airspeed indicators UDC 629.7.054845852BS2G117:1975 This British Standard, having been approved by the AerospaceIndustry Standards Committee, was published underthe authority of the Executive Boa
2、rd on 31October1975 BSI 11-1999 The following BSI references relate to the work on this standard: Committee referenceACE/30 Draft for comment71/39032DC ISBN 0 580 08894 4 Foreword This revision of BSG117:1949 has been prepared to provide an up-to-date statement of the requirements for airspeed indic
3、ators in which the presentation is driven directly by a differential pressure-measuring mechanism, the two pressures being aircraft pitot and static pressures. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for th
4、eir 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, pages1to4 and a back cover. This standard has been updated (see copyright date) and may
5、have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No. Date CommentsBS2G117:1975 BSI 11-1999 i Contents Page Foreword Inside front cover 1 Scope 1 2 References 1 3 Definition 1 4 Unit of measurement 1 5
6、General construction 1 6 Particular requirements 1 7 Tests 1 Appendix A Serviceability tests 4ii blankBS2G117:1975 BSI 11-1999 1 1 Scope This British Standard specifies the general design requirements and test procedures for airspeed indicators operated directly by the aircraft pitot and static pres
7、sures. It relates to indicators with ranges partly or wholly up to800knots. 2 References This standard makes reference to the following British Standards: BS 3G100, General requirements for equipment for use in aircraft. BS 2G101, General requirements for aircraft indicators. BS G199, Tables relatin
8、g 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 Definition For the purposes of this standard the term “airspeed indicator” denotes an instrument used on aircraft to measure the pitot
9、-static pressure difference calibrated in terms of speed. The speed indicated is that speed relative to the air which the aircraft would have to fly in standard sea level conditions to obtain the measured pitot-static pressure difference. 4 Unit of measurement The unit of measurement shall be the kn
10、ot based on the international nautical mile of1852m (exactly). 5 General construction 5.1 The design, construction and presentation of the indicator shall comply with the relevant requirements ofBS 3G100 andBS 2G101 and with the test requirements of clause7 of this standard. 5.2 The preferred cases
11、are the type3 and type6 cases shown inBS 2G101. 6 Particular requirements 6.1 Detailed construction 6.1.1 The indicator shall contain a differential pressure-measuring mechanism driving a form of display complying with the requirements of the individual specification. 6.1.2 Any pointer scale used in
12、 the presentation, which need not be linear, shall comply with the requirements of the individual specification. 6.1.3 The pointer stop shall not be a scale marking. The pointer shall move off the stop to the first scale mark in accordance with the requirements of the individual specification. 6.1.4
13、 Pointers and any settable indices shall comply with the requirements ofBS 2G101. Preferably, the setting controls for indices should be in the bottom left-hand corner of the indicator. 6.1.5 The indicator shall be capable of withstanding a differential pressure10% greater than the maximum pressure
14、range. 6.1.6 The indicator shall be capable of withstanding a reverse pressure (i.e.staticpitot) of10mbar 1) . 6.1.7 The pitot and static connections shall comply with the requirements ofBS 2G101 and shall be indelibly markedP andS respectively. 6.1.8 If a limit pointer is fitted it shall comply wit
15、h the requirements ofBS 2G101. 6.2 Calibration. The calibration of the indicator shall be in accordance with the pressure/speed relationship defined inTable2 ofBS G199. 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 neither
16、 intended nor recommended that complete tests be made on every indicator supplied. Three kinds of tests 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 accordance with the sta
17、ndard; c) production quality tests, to be made on samples as specified in the individual specification. 7.1.2 For the guidance of users,Appendix A recommends minimum tests to verify the serviceability of indicators manufactured in compliance with this British Standard. 7.1.3 Vibration not exceeding0
18、.2g may be applied to the indicators during performance testing, except during the friction test specified in7.2.3. NOTEVibration of this order is attainable with a total amplitude of0.04mm at a frequency of50Hz. 1) 1mbar=10 2 N/m 2 =0.1kPaBS2G117:1975 2 BSI 11-1999 7.1.4 Unless otherwise specified,
19、 tests shall be made at a temperature of20 5 C. 7.1.5 The reference standard for the differential pressure shall be accurate, with corrections, to within0.15% of pressure reading or0.15mbar, whichever is the greater. 7.1.6 With the exception of the damping test in7.2.6, the rate of change of differe
20、ntial pressure applied to the indicator during testing shall not exceed the equivalent of100 pointer movement per second at any point on the indicator range. 7.2 Type tests 7.2.1 Ranging accuracy and hysteresis test 7.2.1.1 With the indicator in the normal position with the dial upright, the indicat
21、or shall be calibrated at both increasing and decreasing pitot pressures at the following points: a) at the lowest scale mark; b) at every50knot and100knot point up to300knots; c) at every100knot point to the maximum of the range: d) at the maximum range point, if not an exact“100”. Other calibratio
22、n points may be required by the individual specification. 7.2.1.2 At 100knots and above, the airspeed errors shall not exceed 2 knotsor 1% of airspeed, whichever is the greater. For speeds below100knots the accuracy requirements shall be stated in the individual specification. 7.2.1.3 If fitted, lim
23、it pointers shall conform to the tolerances specified in the individual specification. 7.2.2 Position test. The change in reading when the indicator is turned in any direction through90 from the normal position shall not exceed half the ranging tolerance appropriate to any point on the scale. 7.2.3
24、Friction. At two points, one in the middle and one in the lower range of the indicator, pitot pressure shall be applied to bring the indication approximately to the desired reading without overshoot and then shall be held constant, the indicator being carefully isolated from vibration. Two readings
25、shall be taken, the first with the instrument undisturbed and the second after the instrument has been tapped or vibration has been applied. The difference between the two readings shall not exceed2knots. 7.2.4 Temperature. At temperatures of20 C and+50 C the errors in airspeed shall not exceed1.5ti
26、mes 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. The indicator shall satisfy the requirements of the test specified in7.2.10 b). NOTEOn a number of modern aircraft
27、 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 individual specification and the performance
28、 of the indicator at such temperature has to be declared. 7.2.5 Overload test. The indicator shall remain within calibration after subjection to the overload pressures specified in6.1.5 and6.1.6 for a period of5min. 7.2.6 Damping test. The damping of the indicator shall be such that, when pressure e
29、quivalent to two-thirds of the full scale reading is applied to the pitot connection and suddenly released, the pointer returns past the minimum scale reading in not more than1s and not lessthan0.5s. 7.2.7 Vibration test. Vibration tests shall be made in accordance with the requirements of BS 3G100-
30、2-3.1, in particular3.4 orB.4.2. Theaccuracy of the indication shall comply with the requirements of7.2.1 of this standard and the pointer oscillation shall be within the overall tolerances, unless otherwise stated in the individual specification. 7.2.8 Acceleration test. The indicator shall be subj
31、ected to acceleration tests in accordance with the requirements ofBS 3G100-2, as required by the individual specification. 7.2.9 Additional environmental tests. The indicator shall be subjected to additional environmental tests specified inBS 3G100-2, as required by the individual specification. The
32、 required functioning tests shall be ranging accuracy at three points spaced equally to cover the range. 7.2.10 Leakage test. This test shall be conducted as follows. a) Pitot pressure shall be applied to the indicator to move the indication to the maximum of the calibrated range and the indicator s
33、hall then be sealed off. After the internal temperature settles, the indication shall not show any decrease in the ensuing minute. b) With the pitot and static connection connected to atmosphere, the indicator shall comply with the requirements of3.10 ofBS 2G101.BS2G117:1975 BSI 11-1999 3 7.2.11 Poi
34、nter freedom test. Pointers or indices shall be checked at all positions within their range to ensure that no fouling with the main indication takes place. 7.3 Production routine 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
35、.2.10 and7.2.11. 7.4 Production quality tests. Sample indicators, selected as specified in the individual specification, shall satisfactorily fulfil the requirements of the tests specified in7.2.4, 7.2.6, 7.2.7 (resonance search only),7.2.8 and7.2.9. Any significant change in resonance frequency or
36、any new resonance frequencies shall be recorded.BS2G117:1975 4 BSI 11-1999 Appendix A Serviceability tests The minimum tests recommended to verify the serviceability of indicators manufactured in compliance with this British Standard are as follows. A.1 Ranging accuracy and hysteresis test(7.2.1). A
37、.2 Friction test(7.2.3). A.3 Leakage test(7.2.10). A.4 Pointer freedom test(7.2.11), if relevant.blankBS2G117: 1975 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandards. It presents the UK view on stan
38、dards in Europe and at the international level. It is incorporated by Royal Charter. Revisions BritishStandards are updated by amendment or revision. Users of BritishStandards should make sure that they possess the latest amendments or editions. It is the constant aim of BSI to improve the quality o
39、f our products and services. We would be grateful if anyone finding an inaccuracy or ambiguity while using this BritishStandard would inform the Secretary of the technical committee responsible, the identity of which can be found on the inside front cover. Tel:02089969000. Fax:02089967400. BSI offer
40、s members an individual updating service called PLUS which ensures that subscribers automatically receive the latest editions of standards. Buying standards Orders for all BSI, international and foreign standards publications should be addressed to Customer Services. Tel:02089969001. Fax:02089967001
41、. In response to orders for international standards, it is BSI policy to supply the BSI implementation of those that have been published as BritishStandards, unless otherwise requested. Information on standards BSI provides a wide range of information on national, European and international standard
42、s through its Library and its Technical Help to Exporters Service. Various BSI electronic information services are also available which give details on all its products and services. Contact the Information Centre. Tel:02089967111. Fax:02089967048. Subscribing members of BSI are kept up to date with
43、 standards developments and receive substantial discounts on the purchase price of standards. For details of these and other benefits contact Membership Administration. Tel:02089967002. Fax:02089967001. Copyright Copyright subsists in all BSI publications. BSI also holds the copyright, in the UK, of
44、 the publications of the international standardization bodies. Except as permitted under the Copyright, Designs and Patents Act 1988 no extract may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, photocopying, recording or otherwise without prior wr
45、itten permission from BSI. This does not preclude the free use, in the course of implementing the standard, of necessary details such as symbols, and size, type or grade designations. If these details are to be used for any other purpose than implementation then the prior written permission of BSI must be obtained. If permission is granted, the terms may include royalty payments or a licensing agreement. Details and advice can be obtained from the Copyright Manager. Tel:02089967070.
