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1、BRITISH STANDARD AEROSPACE SERIES BS G 211:1971 Incorporating Amendment No. 1 Specification for Reflection reducing coating of instrument windows and lighting wedges UDC 629.7.05:53.084:535.3 Licensed Copy: London South Bank University, London South Bank University, Sat Dec 09 02:24:40 GMT+00:00 200
2、6, Uncontrolled Copy, (c) BSI BS G 211:1971 This British Standard, having been approved by the Aerospace Industry Standards Committee, was published under the authority of the Executive Board of the Institution on 24 March 1971 BSI 12-1999 The following BSI references relate to the work on this stan
3、dard: Committee reference ACE/30 Draft for comment 67/7655 ISBN 580 06129 9 Foreword This British Standard deals with the coating of glass to reduce the specular reflection of white light from instrument windows and lighting wedges. It is not primarily concerned with light transmission, and does not
4、 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 shown in parentheses after values in metric units, the figures in metric units are to be regarded as the standard. Such equivalents are approxima
5、te; more accurate conversions should be based on the tables in BS 350, “Conversion factors and tables”. 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 Stand
6、ard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 5 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indi
7、cated in the amendment table on the inside front cover. Amendments issued since publication Amd. No.Date of issueComments 767August 1971Indicated by a sideline in the margin Licensed Copy: London South Bank University, London South Bank University, Sat Dec 09 02:24:40 GMT+00:00 2006, Uncontrolled Co
8、py, (c) BSI BS G 211:1971 BSI 12-1999i Contents Page ForewordInside front cover 1Scope1 2Terminology1 3Physical properties of coating1 4Reflectance1 5Transmittance1 6Colour uniformity1 7Inspection and testing1 Figure 1 Arrangement for inspection of coated elements for surface imperfections3 Figure 2
9、 Arrangement for inspection of coated lighting wedges for surface imperfections3 Figure 3 Eraser for abrasion test4 Figure 4 Arrangement for reflectance and transmittance test (see 7.4)4 Figure 5 Arrangement for colour uniformity test5 Licensed Copy: London South Bank University, London South Bank U
10、niversity, Sat Dec 09 02:24:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii blank Licensed Copy: London South Bank University, London South Bank University, Sat Dec 09 02:24:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS G 211:1971 BSI 12-19991 1 Scope This British Standard specifies the requirem
11、ents 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 electrotechnical, power, telecommunication,
12、electronics, lighting and colour terms” Part 4, “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 dimensions to be agreed with the purchas
13、er. 3.2 Surface imperfections 3.2.1 The coated element shall be free from visible imperfections when inspected in accordance with 7.1.1. 3.2.2 (Lighting wedges only.) The coated lighting wedge shall be free from visible imperfections when inspected in accordance with 7.1.2. NOTEThis requirement is a
14、pplicable to coated lighting wedges additionally to the requirements specified in 3.2.1. 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 that the coated glasses will satisfy
15、the requirements of the tests in 7.3. 4 Reflectance The specular reflectance of the coated window for illuminant D6500 of the Commission Internationale de lEclairage (CIE) shall be less than 0.5 % per surface when viewed by a CIE standard photopic observer. The reflectance shall be measured at any a
16、ngle of incidence lying within the range from normal to 15. 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 Colour uniformity When inspected
17、in accordance with 7.5, the colour of the light reflected at an angle of 15 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 inspected as follows for conformity wi
18、th the requirements specified in 3.2.1: 1) The coated element is illuminated by the lamp specified in 7.1.3 and viewed at a distance of 250 50 mm (10 2 in) against a mat black background in a) the reflection mode see Figure 1, position (a); b) the transmission mode see Figure 1, position (b). 2) The
19、 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 in 3.2.2: 1) The coated lighting wedge is edge illuminated by the lamp specified i
20、n 7.1.3 at a distance of 50 10 mm (2 0.4 in) and viewed at a distance of 250 50 mm (10 2 in) 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. A 240 V 4 W daylight type fluoresc
21、ent lamp of tube nominal dimensions 150 mm (6 in) length by 16 mm (0.625 in) diameter shall be used for the purposes of the tests specified in this British Standard. 7.2 Testing. Tests shall be made on randomly selected samples, each sample being subjected to all of the tests, and the durability tes
22、ts being made in the order in which they are given in 7.3. After each test the sample shall be cleaned with a lens tissue or a soft cloth and checked for compliance with the requirements specified in 3.2 and Clauses 4 and 5. 1) In course of preparation. Licensed Copy: London South Bank University, L
23、ondon South Bank University, Sat Dec 09 02:24:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS G 211:1971 2 BSI 12-1999 7.3 Durability tests 7.3.1 Adhesion test. A length of freshly cut unused 25 mm (1 in) wide pressure-sensitive adhesive tape2) of at least 9.8 N/25 mm (1 000 gf/in) peel adhesion ra
24、ting 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 coated windows shall be immersed for a period of 24 hours in a solution of water and sodium chloride. The mixture shall be 37 g of salt in 1 litre
25、 of water (6 oz/UKgal) at room temperature. 7.3.3 Humidity test. Sample coated windows, mounted vertically, shall be exposed continuously for 24 hours in an atmosphere of 49 1 C and 98 2 % relative humidity. 7.3.4 Abrasion test. The coated element shall be tested by rubbing with a standard eraser3)
26、mounted in a standard holding device (see Figure 3)4). A force of between 9 N and 11 N (2 lbf and 2.5 lbf) shall be applied. Strokes of approximately 25 mm (1 in) shall be made if the size of the element permits, shorter strokes shall be made on smaller elements. All the strokes shall be made in an
27、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 with the requirements specified in Clauses 4 and 5 is shown in Figure 4. Light from an incandescent tungsten lamp T is co
28、ndensed 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 integrating sphere equipped with internal baffle and a selenium photo-voltaic cell is employed as detector, the output of the
29、cell being measured with a galvanometer. A correction filter F is placed in the beam in order to simulate the conditions of standard illumination and observation specified in Clauses 4 and 5. The choice of filter is dictated by both the colour temperature of the lamp and the spectral response of the
30、 detector. 7.4.2 For testing for compliance with the requirements specified in Clause 4 a clean, uncoated glass plate of known optical constants is introduced at S, inclined at the appropriate angle of incidence. The photometer head is positioned to collect the reflected light and the galvanometer r
31、eading 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 yields the measured reflectance of the coated window. The photometer is to be calibrated to ensure that the measured
32、reflectance of a typical sample does not differ by more than 10 % from the reflectance determined under the standard conditions specified in Clause 4. 7.4.3 For testing for compliance with the requirements specified in Clause 5 the uncoated and coated window are interposed in turn in the normally in
33、cident 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 requirements specified in Clauses 4 and 5 extrapolated by calculation. In this instance it is also necessary
34、to ensure that the calibration of the instrument lies within the tolerance described in 7.4.2. 7.5 Colour uniformity test. The coated element shall be visually inspected as follows for conformity with the requirements specified in Clause 6: 1) The coated element is illuminated by the lamp specified
35、in 7.1.3 at a distance of 250 50 mm (10 2 in) and viewed at an angle of reflection of 15 1 at a distance of 250 50 mm (10 2 in). 2) The axis of symmetry of the fluorescent lamp is parallel to the plane of the coated element surface. 3) The two coated surfaces of a wedge element are evaluated separat
36、ely. 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 erasers, conforming to U.S. Military Specification MIL-E-12397 B, are obtainable from the Sira Ins
37、titute, South Hill, Chislehurst, Kent. 4) This eraser holder conforms to U.S. Military Specification drawing No. D.7680606 issue 24.3.67. Licensed Copy: London South Bank University, London South Bank University, Sat Dec 09 02:24:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS G 211:1971 BSI 12-199
38、93 Figure 1 Arrangement for inspection of coated elements for surface imperfections Figure 2 Arrangement for inspection of coated lighting wedges for surface imperfections Licensed Copy: London South Bank University, London South Bank University, Sat Dec 09 02:24:40 GMT+00:00 2006, Uncontrolled Copy
39、, (c) BSI BS G 211:1971 4 BSI 12-1999 NOTESpring pressure to be 11 1 N (2.5 0.25 lbf) when compressed to show any portion of white indicator band “A” flush with end of body “X”. PartDescription 1Hand moulded rubber body 2Brass plunger 3Brass rod 4Brass adaptor 5Wire spring 6Eraser plug Figure 3 Eras
40、er for abrasion test Figure 4 Arrangement for reflectance and transmittance test (see 7.4) Licensed Copy: London South Bank University, London South Bank University, Sat Dec 09 02:24:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS G 211:1971 BSI 12-19995 Figure 5 Arrangement for colour uniformity t
41、est Licensed Copy: London South Bank University, London South Bank University, Sat Dec 09 02:24:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS G 211:1971 BSI 389 Chiswick High Road London W4 4AL BSI British Standards Institution BSI is the independent national body responsible for preparing Britis
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