1、BRITISH STANDARD AEROSPACE SERIES BS G211:1971 Incorporating Amendment No.1 Specification for Reflection reducing coating of instrument windows and lighting wedges UDC 629.7.05:53.084:535.3BSG211:1971 This BritishStandard, having been approved by the AerospaceIndustry StandardsCommittee, waspublishe
2、d under theauthorityof the ExecutiveBoard of theInstitutionon 24March1971 BSI12-1999 The following BSI references relate to the work on this standard: Committee reference ACE/30 Draft for comment67/7655 ISBN 580 06129 9 Foreword This BritishStandard deals with the coating of glass to reduce the spec
3、ular reflection of white light from instrument windows and lighting wedges. It is not primarily concerned with light transmission, and does not specify the materials used for the coating, which may vary according to the type of glass to be coated. NOTEWhere equivalent values in imperial units are sh
4、own in parentheses after values in metric units, the figures in metric units are to be regarded as the standard. Such equivalents are approximate; more accurate conversions should be based on the tables in BS350, “Conversion factors and tables”. A British Standard does not purport to include all the
5、 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 document comprises a front cover, an inside front cover, pagesi andii, pa
6、ges1 to5 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. Amendments issued since publication Amd. No. Date of issue Comments 767 August 1971 Indicated by a sidelin
7、e in the marginBSG211:1971 BSI 12-1999 i Contents Page Foreword Inside front cover 1 Scope 1 2 Terminology 1 3 Physical properties of coating 1 4 Reflectance 1 5 Transmittance 1 6 Colour uniformity 1 7 Inspection and testing 1 Figure 1 Arrangement for inspection of coated elements for surface imperf
8、ections 3 Figure 2 Arrangement for inspection of coated lighting wedges for surface imperfections 3 Figure 3 Eraser for abrasion test 4 Figure 4 Arrangement for reflectance and transmittance test (see7.4) 4 Figure 5 Arrangement for colour uniformity test 5ii blankBSG211:1971 BSI 12-1999 1 1 Scope Th
9、is BritishStandard specifies the requirements for the treatment of the window elements and lighting wedges of aircraft instruments to reduce specular reflection of white light. 2 Terminology Unless otherwise stated, the terminology used in this standard is in accordance with BS. 1) , “Glossary of el
10、ectrotechnical, power, telecommunication, electronics, lighting and colour terms” Part4, “Terms particular to lighting and colour”. 3 Physical properties of coating 3.1 The coating shall be applied over the entire effective aperture of the specified surfaces, with the exception of a narrow border of
11、 dimensions to be agreed with the purchaser. 3.2 Surface imperfections 3.2.1 The coated element shall be free from visible imperfections when inspected in accordance with7.1.1. 3.2.2 (Lighting wedges only.) The coated lighting wedge shall be free from visible imperfections when inspected in accordan
12、ce with7.1.2. NOTEThis requirement is applicable to coated lighting wedges additionally to the requirements specified in3.2.1. 3.3 Unless otherwise agreed, evidence shall be produced by the manufacturer to the satisfaction of the purchaser that the materials and process used for the coating are such
13、 that the coated glasses will satisfy the requirements of the tests in7.3. 4 Reflectance The specular reflectance of the coated window for illuminant D6500 of the Commission Internationale de lEclairage (CIE) shall be less than0.5% per surface when viewed by a CIEstandard photopic observer. The refl
14、ectance shall be measured at any angle of incidence lying within the range from normal to15 . 5 Transmittance The regular transmittance of the coated window for normally incident CIE illuminant D6500 shall not be less than that of an uncoated window when viewed by a CIE standard photopic observer. 6
15、 Colour uniformity When inspected in accordance with7.5, the colour of the light reflected at an angle of15 1 by the coated surface(s) from the specified light source shall be uniform across the coated element. 7 Inspection and testing 7.1 Inspection 7.1.1 The coated element shall be visually inspec
16、ted as follows for conformity with the requirements specified in3.2.1: 1) The coated element is illuminated by the lamp specified in7.1.3 and viewed at a distance of250 50mm(102in) against a mat black background in a) the reflection mode see Figure 1, position(a); b) the transmission mode see Figure
17、 1, position(b). 2) The lamp is shielded from the observer and is the only source of illumination. 7.1.2 (Lighting wedges only.) The coated lighting wedge shall be visually inspected as follows for conformity with the requirements specified in3.2.2: 1) The coated lighting wedge is edge illuminated b
18、y the lamp specified in7.1.3 at a distance of50 10mm(2 0.4in) and viewed at a distance of250 50mm(102in) against a mat black background. 2) The lamp is shielded and is the only source of illumination. 3) A suitable inspection system is shown in Figure 2. 7.1.3 Inspection lamp. A240V4 W daylight type
19、 fluorescent lamp of tube nominal dimensions150mm(6in) length by16mm(0.625in) diameter shall be used for the purposes of the tests specified in this BritishStandard. 7.2 Testing. Tests shall be made on randomly selected samples, each sample being subjected to all of the tests, and the durability tes
20、ts being made in the order in which they are given in7.3. After each test the sample shall be cleaned with a lens tissue or a soft cloth and checked for compliance with the requirements specified in3.2 and Clauses4 and5. 1) In course of preparation.BSG211:1971 2 BSI 12-1999 7.3 Durability tests 7.3.
21、1 Adhesion test. A length of freshly cut unused25mm(1in) wide pressure-sensitive adhesive tape 2)of at least9.8N/25mm(1000gf/in) peel adhesion rating shall be pressed firmly on to the coated surface of the glass. The tape shall then be removed quickly with a snap action. 7.3.2 Solubility test. The c
22、oated windows shall be immersed for a period of24hours in a solution of water and sodium chloride. The mixture shall be37g of salt in1litre of water(6oz/UKgal) at room temperature. 7.3.3 Humidity test. Sample coated windows, mounted vertically, shall be exposed continuously for24hours in an atmosphe
23、re of49 1 C and982% relative humidity. 7.3.4 Abrasion test. The coated element shall be tested by rubbing with a standard eraser 3)mounted in a standard holding device (see Figure 3) 4) . A force of between9N and11N(2lbf and2.5lbf) shall be applied. Strokes of approximately25mm(1in) shall be made if
24、 the size of the element permits, shorter strokes shall be made on smaller elements. All the strokes shall be made in an approximately straight line along one path for twenty strokes. 7.4 Reflectance and transmittance test 7.4.1 A suggested test arrangement for testing coated windows for compliance
25、with the requirements specified in Clauses4 and5 is shown in Figure 4. Light from an incandescent tungsten lamp T is condensed on to an aperture A and a collimated beam is produced by a lens L. The cross section of the beam may be continuously varied by an iris diaphragm D. A suitably coated integra
26、ting sphere equipped with internal baffle and a selenium photo-voltaic cell is employed as detector, the output of the cell being measured with a galvanometer. Acorrection filter F is placed in the beam in order to simulate the conditions of standard illumination and observation specified in Clauses
27、4 and5. Thechoice of filter is dictated by both the colour temperature of the lamp and the spectral response of the detector. 7.4.2 For testing for compliance with the requirements specified in Clause4 a clean, uncoated glass plate of known optical constants is introduced at S, inclined at the appro
28、priate angle of incidence. The photometer head is positioned to collect the reflected light and the galvanometer reading noted. The plate is then replaced by the coated window and the new reading noted. When related to the calculated reflectance of the uncoated plate, the ratio of these readings yie
29、lds the measured reflectance of the coated window. Thephotometer is to be calibrated to ensure that the measured reflectance of a typical sample does not differ by more than10% from the reflectance determined under the standard conditions specified in Clause4. 7.4.3 For testing for compliance with t
30、he requirements specified in Clause5 the uncoated and coated window are interposed in turn in the normally incident beam at S, and the relative galvanometer readings noted. 7.4.4 Alternatively, the reflectance and transmittance tests may be carried out by using a suitable spectro-photometer and the
31、requirements specified in Clauses4 and5 extrapolated by calculation. In this instance it is also necessary to ensure that the calibration of the instrument lies within the tolerance described in7.4.2. 7.5 Colour uniformity test. The coated element shall be visually inspected as follows for conformit
32、y with the requirements specified in Clause6: 1) The coated element is illuminated by the lamp specified in7.1.3 at a distance of250 50mm(102in) and viewed at an angle of reflection of15 1 at a distance of250 50mm(102in). 2) The axis of symmetry of the fluorescent lamp is parallel to the plane of th
33、e coated element surface. 3) The two coated surfaces of a wedge element are evaluated separately. 4) The lamp is shielded from the observer and is the only source of illumination. 5) A suitable inspection system is shown in Figure 5. 2) Scotch Tape No.56 is suitable for this test. 3) Standard eraser
34、s, conforming to U.S. Military Specification MIL-E-12397 B, are obtainable from the Sira Institute, South Hill, Chislehurst, Kent. 4) This eraser holder conforms to U.S. Military Specification drawing No. D.7680606 issue24.3.67.BSG211:1971 BSI 12-1999 3 Figure 1 Arrangement for inspection of coated
35、elements for surface imperfections Figure 2 Arrangement for inspection of coated lighting wedges for surface imperfectionsBSG211:1971 4 BSI 12-1999 NOTESpring pressure to be11 1 N(2.5 0.25lbf) when compressed to show any portion of white indicator band “A” flush with end of body“X”. Part Description
36、 1 Hand moulded rubber body 2 Brass plunger 3 Brass rod 4 Brass adaptor 5 Wire spring 6 Eraser plug Figure 3 Eraser for abrasion test Figure 4 Arrangement for reflectance and transmittance test (see 7.4)BSG211:1971 BSI 12-1999 5 Figure 5 Arrangement for colour uniformity testBS G211:1971 BSI 389 Chi
37、swick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandards. It presents the UK view on standards in Europe and at the international level. It is incorporated by Royal Charter. Revisions BritishStandards are updated by
38、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 of our products and services. We would be grateful if anyone finding an inaccuracy or ambiguity while using this BritishStandard
39、 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 offers members an individual updating service called PLUS which ensures that subscribers automatically receive the latest editions o
40、f standards. Buying standards Orders for all BSI, international and foreign standards publications should be addressed to Customer Services. Tel:02089969001. Fax:02089967001. In response to orders for international standards, it is BSI policy to supply the BSI implementation of those that have been
41、published as BritishStandards, unless otherwise requested. Information on standards BSI provides a wide range of information on national, European and international standards through its Library and its Technical Help to Exporters Service. Various BSI electronic information services are also availab
42、le 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 standards developments and receive substantial discounts on the purchase price of standards. For details of these and other be
43、nefits contact Membership Administration. Tel:02089967002. Fax:02089967001. Copyright Copyright subsists in all BSI publications. BSI also holds the copyright, in the UK, of the publications of the international standardization bodies. Except as permitted under the Copyright, Designs and Patents Act
44、 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 written permission from BSI. This does not preclude the free use, in the course of implementing the standard, of necessary detail
45、s 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.
