1、BRITISH STANDARD AEROSPACE SERIES BS 3G 100-2.3.10: 1974 Specification for General requirements for equipment for use in aircraft Part 2: All equipment Section 3: Environmental conditions Subsection 3.10 Impact icingBS 3G100-2.3.10:1974 This British Standard, having been approved by the Aerospace In
2、dustry Standards Committee, was published under the authorityof the Executive Boardon 14 January 1974 BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference ACE/58 Draft for comment 70/26883 DC ISBN 0 580 08183 4 Amendments issued since publication Amd. No.
3、 Date CommentsBS 3G100-2.3.10:1974 BSI 07-1999 i Contents Page Foreword ii 1 Scope 1 2 Test procedure 1 3 Test severities 1 4 Performance evaluation 1 5 Information to be stated in the relevant equipment specification 1 Appendix A Choice of test severities 2 Appendix B Guidance on impact icing test
4、4 Figure 1 Variation of wet kinetic temperature with free steam velocity and temperature 7 Table 1 Continuous icing conditions 2 Table 2 Intermittent icing conditions 2 Table 3 Ice crystal conditions 3 Table 4 Mixed conditions 3 Table 5 Droplet-size distribution 4BS 3G100-2.3.10:1974 ii BSI 07-1999
5、Foreword This British Standard is part of a composite standard in the Aerospace Series of British Standards specifying requirements for equipment for use in aircraft. An introduction to the complete standard is given in BS3G 100-0 “Introduction”. This subsection of BS 3G 100 supplements the requirem
6、ents of BS 3G 100-2.3.9 “Ice formation”. This standard specifies requirements and gives guidance on the choice of severities for the testing of equipment which will be located external to the aircraft, where it may be subjected to impact by supercooled water droplets or ice crystals. Additional guid
7、ance is given on the conduct of impact icing tests. This standard makes reference to the following British Standards: BS 3G 100, General requirements for equipment in aircraft Part0:Introduction. BS G 135, Electrically-heated pitot and pitotstatic pressure heads 1) . NOTEInformation concerning metri
8、c (SI) units is given in BS 3763 “The International System of units (SI)”, BS350 “Conversion factors and tables” and PD5686 “The use of SI units”. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct a
9、pplication. 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, pages i and ii, pages1 to 7 and a back cover. This standard has been updated (see copyright date) and may have had
10、amendments incorporated. This will be indicated in the amendment table on the inside front cover. 1) The latest revision is currently in preparation.BS 3G100-2.3.10:1974 BSI 07-1999 1 1 Scope The test in this British Standard is applicable to equipment installed in a forward facing location external
11、 to an aircraft or in the intake ducting where it may be subjected to the impact of supercooled water droplets or ice crystals, and where under conditions of near or sub-zero temperatures ice may form or accumulate and interfere with the safe operation of the equipment or result in the shedding of i
12、ce fragments hazardous to other equipment installed downstream. This standard should be read in conjunction with BS3G 100-0. 2 Test procedure 2.1 The equipment shall be mounted in an icing wind tunnel at the angles of incidence and yaw specified in the relevant equipment specification. 2.2 The tunne
13、l free stream temperature 2) , airspeed and, where required by the relevant equipment specification, the altitude, shall be adjusted to the values appropriate to the particular test, (see clause3), and these values maintained until the equipment temperature has stabilized. 2.3 The equipment shall th
14、en be exposed to a uniform spray of super-cooled water droplets of 204m nominal volume median diameter (vmd), or ice crystal conditions, as appropriate to the test for the duration(s) specified. 2.4 The equipment anti-icing or de-icing system, when fitted, shall be activated as specified in the equi
15、pment specification. 3 Test severities Separate tests shall be made in turn at each set of test severities, defined in terms of temperature, water or ice crystal concentration, airspeed and duration, and altitude when applicable, in accordance with the relevant equipment specification. Although it i
16、s possible to define the design icing atmosphere, it is not possible to define a simple set of test severities applicable to all equipments since the most adverse test conditions for an individual equipment depend on a number of factors, e.g.the severity of icing for which clearance is required, the
17、 performance envelope of the aircraft to which it is fitted, the type of ice protection system employed, etc. Guidance on the choice of test severities is given in Appendix A. 4 Performance evaluation The tests are to be conducted to evaluate the performance of 1) the equipment and its anti-icing or
18、 de-icing system, or 2) the equipment when not fitted with an anti-icing or de-icing system, or 3) the anti-icing or de-icing system only. The object(s) of the test shall be clearly stated in the relevant equipment specification. The duty cycle of the equipment shall also be specified and shall be t
19、hat found most likely to give rise to defects of performance which the test is evaluating. 5 Information to be stated in the relevant equipment specification When an impact icing test is a requirement in the relevant equipment specification the following information shall be stated, as far as is app
20、licable. 2) This term is explained in Appendix B. Relevant clause (1) The object of the test, i.e. whether itis a demonstration of performance orsurvival. 4 (2) The phase(s) of the test cycle when the equipment is to be operated and theperformance evaluation made (if performance is to be assessed).
21、4 (3) The phase(s) of the test cycle when the anti-icing or de-icing systems are tobe employed (if fitted). 2.4 (4) The orientation of the equipment relative to air flow and/or water spray. 2.1 (5) The test severities, i.e. the airspeed,altitude (where applicable), icing conditions and duration(s).
22、3 and Appendix ABS 3G100-2.3.10:1974 2 BSI 07-1999 Appendix A Choice of test severities A.1 Introduction Although icing atmospheres have been derived for design purposes relating liquid water and ice crystal content to ambient air temperature, it is clearly unnecessary to test an equipment at all te
23、mperatures, altitudes and airspeeds within the performance envelope of the aircraft to which it is fitted. It is therefore necessary to select the minimum number of test conditions which will satisfy the Approving Authority 3)that adequate performance has been demonstrated. This requires that for ea
24、ch equipment a review is made of its performance over the entire operating envelope within the icing atmospheres to determine the most adverse operational conditions. Guidance in the transposition of these conditions into sets of test severities compatible with the limits of the test equipment defin
25、ed in terms of altitude, air temperature, air speed, water or ice crystal concentrations and duration is given in B.7 and B.8 of Appendix B. A.2 Icing atmospheres For design purposes four icing atmospheres, i.e.continuous icing conditions, intermittent icing conditions for supercooled water droplet
26、cloud, ice crystal conditions and mixed conditions, are stated in A.2.1 to A.2.4: A.2.1 Continuous icing conditions. The continuous icing conditions are as defined in Table 1, except that at altitudes less than1 200m(4000ft) it is assumed that there is linear variation of liquid water content with a
27、ltitude to zero content at sea level, except that below300m(1000ft) the content for300m(1000ft) is assumed. Table 1 Continuous icing conditions A.2.2 Intermittent icing conditions. The intermittent icing conditions for: 1) altitudes above9100m (30000ft) shall be 2.5 nautical miles of the appropriate
28、 condition of Table 2, alternating with 20 nautical miles of clear air; 2) altitudes below 9100m (30000ft) shall be 2.5 nautical miles of the appropriate condition of Table 2, alternating with 2.5 nautical miles of the appropriate continuous icing condition, except that at altitudes less than 4600m
29、(15000ft) the liquid water content of Table 2 may be assumed to decrease linearly with altitude to zero at sea level. Table 2 Intermittent icing conditions 3) The Approving Authorities for aircraft equipment are the Civil Aviation Authority, Airworthiness Division for civil aircraft and the Procurem
30、ent Executive, Ministry of Defence for military aircraft, or a design authority approved by them. Air temperature Altitude range Liquid water content Mean water droplet size C m ft g/m 3 4m 0 06100 020000 0.8 20 10 12007600 400025000 0.6 20 12009100 400030 000 0.3 30 12009100 400030 000 0.2 Air temp
31、erature Altitude range Liquid water content Mean water droplet size C m ft g/m 3 4m 0 15006100 500020 000 2.5 2.0 10 15007600 500025 000 2.2 20 30009100 10 00030 000 1.7 30 460010 700 15 00035 000 1.0 40 610012 200 20 00040 000 0.2 BS 3G100-2.3.10:1974 BSI 07-1999 3 A.2.3 Ice crystal conditions. The
32、 ice crystal conditions are as defined in Table 3. Table 3 Ice crystal conditions A.2.4 Mixed conditions. The mixed conditions are as defined in Table 4. Table 4 Mixed conditions A.2.5 Duration. The assumed duration of an icing encounter should be: 1) continuous icing conditions: 30 min; 2) intermit
33、tent icing conditions: a total duration of 10 min with the durations of alternative liquid water concentrations appropriate to the airspeed and horizontal extents; 3) ice crystal and mixed conditions: a total time of 30 min with the durations of the different contents appropriate to the airspeed and
34、 horizontal extents. The durations at the lower contents shall be equally divided about the times at the higher concentrations. A.3 Selection of test severities The derived test severities will depend on a number of features but the type of ice protection system employed will probably have the large
35、st influence. For example, in the case of a thermal anti-icing system, increase in speed increases the kinetic temperature of the surface but it also increases the catch efficiency and the rate of liquid water catch. The effect is such that a speed results at which the thermal requirements are at a
36、maximum, at a particular temperature. If the heating is by hot air, as opposed to electric heating, the air supply may be affected by engine setting, which is a function of speed and altitude and therefore may result in an additional adverse speed condition. NOTEAn example of an icing test in accord
37、ance with the requirements of this British Standard, is specified in BS G135 for electrically-heated pitot and pitotstatic pressure heads. Air temperature Altitude range Ice content Extent Mean crystal size C m ft g/m 3 nautical miles mm 8.0 0.5 0 to 20 3000 9 100 10 000 30 000 5.0 2.0 1.0 2.5 50 30
38、0 1 20 to 40 4600 12 200 15 000 40 000 5.0 2.0 1.0 0.5 2.5 10 50 300 1 Air temperature Altitude range Ice content Water content Extent Mean crystal size Max.water droplet size C m ft g/m 3 g/m 3 nautical miles mm mm 0 to 10 3 0009 100 10 000 30 000 7 4 1 0.5 1 1 1 0.5 0.5 2.5 5.0 300 1 2 BS 3G100-2.
39、3.10:1974 4 BSI 07-1999 Appendix B Guidance on impact icing test B.1 General introduction B.1.1 The purpose of the test is to check the performance of exposed forward facing equipments during simulated flight through ice forming conditions: to check the performance of an anti-icing or de-icing syste
40、m, to ensure that the maximum size of ice accretion does not interfere with the safe operation of the equipment or result in the shedding of ice fragments hazardous to other equipments downstream. B.1.2 A sophisticated test facility is required for accurate simulation of flight through cloud. The co
41、nstruction, and especially the calibration, of an icing tunnel requires both considerable expertise and expenses recourse should be made, where possible, to established icing wind tunnels for tests of this nature. B.2 Icing tunnels Essentially, an icing wind tunnel consists of a working section with
42、in which a velocity controlled low temperature airstream is supplied with a homogeneous spray of supercooled water droplets, ice crystals or water droplet/ice crystal mixture of controlled size and concentration. Free stream temperatures (see B.7) in the range0 C to40 C are required and this is usua
43、lly achieved by heat exchangers situated in a low velocity section of the tunnel or by the injection of liquid nitrogen. Closed or open circuit tunnels can be used but precautions must be taken to ensure that frost or liquid water condensation on the heat exchangers does not affect the flow or the t
44、emperature during long uns, or enhance the supercooled water concentration in the working section or provide ice forming nuclei. Since the icing case at40 C is not normally the critical design case, a free stream tunnel temperature range of0 C to30 C is usually adequate. B.3 Droplet size and size di
45、stribution The size of the droplets in the spray is defined in terms of a vmd of 20 4m. In a droplet spectrum 50 % of the volume of water is contained in droplets of diameter smaller than the vmd and 50 % in droplets of diameters larger than the vmd. The size distribution should be reasonably simila
46、r to that in natural cloud given in Table 5. Table 5 Droplet size distribution B.4 Droplet production various methods can be used to produce liquid water droplet sprays but gas-atomizing spray nozzles have proved to be the most successful for icing work and can be made to approximate closely the req
47、uired droplet size distribution. Care must be taken to avoid static temperatures that are in the order of40 C or below in the spray or spontaneous formation of ice crystals may result. This is usually achieved by pre-heating the air, water or both, which also reduces the risk of freezing up of the n
48、ozzles. B.5 Spray calibration Periodic calibration of the droplet spray is required to ensure its adequacy. Various methods can be used for this, some of which are listed below. Droplet dia. ratio d F /d V 0.27 0.55 0.83 1.1 1.39 1.67 1.95 2.22 % by weight of total water content contained in droplet
49、s of dia. d F 3 8 20 30 20 10 5 4 where d Fis the particular droplet diameter under consideration and d Vis the volume median droplet diameter. Heated intake and hygrometer Samples of the cloud are heated to evaporate the droplets, the dew point determined by hygrometer and the water content calculated. Proprietary water content meters or icing rate meters Various instruments are available whi
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