1、BRITISH STANDARD AEROSPACE SERIES BS G226:1979 Specification for Counter and pointer, servo type, pressure altimeter systems UDC 629.7.054.058.42:531.719.4.085.311.087.9BSG226:1979 This BritishStandard, having been prepared under the directionof the Aerospace Standards Committee, was published under
2、 the authority ofthe Executive Board on 31January 1979 BSI 01-2000 The following BSI references relate to the work on this standard: Committee reference ACE/30 Draft for comment75/75233DC ISBN 0 580 10603 9 Foreword This BritishStandard, which is one of a series for indicators for use in aircraft, r
3、elates to servo type pressure altimeter systems, calibrated in feet, suitable for indications up to80000ft or a lesser altitude, as may be declared. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct
4、 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, pages1 to8, an inside back cover and a back cover. This standard has been updated (see copyright da
5、te) 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 CommentsBSG226:1979 BSI 01-2000 i Contents Page Foreword Inside front cover 1 Scope 1 2 References 1 3 General constructio
6、n requirements 1 4 Particular requirements 1 4.1 Construction 1 4.2 Performance 2 5 Tests 3 5.1 General 3 5.2 Test conditions 3 6 Type tests 4 6.1 Ranging accuracy and hysteresis test 4 6.2 Damping test 4 6.3 Barometric pressure scale test 4 6.4 Instrument attitude error test 4 6.5 Leakage tests 4 6
7、.6 Drift and after effect test 5 6.7 Servo chase rate test 5 6.8 Friction test 5 6.9 Threshold test 5 6.10 Pressure overload test 5 6.11 Test of failure warning device 5 6.12 Altimeter-encoder tests (type B instruments only) 5 6.13 Temperature tests 6 6.14 Vibration test 6 6.15 Acceleration test 6 6
8、.16 Tropical exposure test 6 6.17 Mould growth test 6 6.18 Salt mist test 6 6.19 Electrical tests 6 7 Production routine tests 6 8 Production quality tests 7 Appendix A Serviceability tests Inside back cover Figure 1 Encoder “turn-on” voltage limits 8 Table 1 Altitudes, pressures and permissible err
9、ors 2 Table 2 Test points for barometric pressure scale test 4 Table 3 Friction test: altitudes and tolerances 7 Table 4 Test points for altimeter-encoder test 7ii blankBSG226:1979 BSI 01-2000 1 1 Scope This BritishStandard specifies the general design and performance requirements for pressure altim
10、eter systems having a combined counter and single pointer presentation in two forms as follows. a) Type A. A panel-mounting indicator associated with its own internal or external pressure sensing mechanism. b) Type B. As type A but incorporating an encoder for altitude reporting purposes. Provision
11、is made for instrument systems operating over an indicated range of2000ft to+80000ft (geopotential) or such other range as may be declared. The design includes a barometric pressure setting facility and may include provision for applying corrections for the aircraft static pressure system error. 2 R
12、eferences This standard makes reference to the following standards publications. BS3G100, General requirements for equipment for use in aircraft. BS G101, General requirements for aircraft indicators. BS G191, Lighting for aircraft indicators using integral filament lamps. BS G199, Tables relating p
13、ressure to altitude, airspeeds and Mach numbers, for use in aeronautical instrument design and calibration. BS G211, Reflection-reducing coating of instrument windows and lighting wedges. BS2520, Barometer conventions and tables. The latest editions of these standards shall be used. NOTEThe latest r
14、evision of an Aerospace Series standard is indicated by a prefix number. Reference is also made to the following ICAO (International Civil Aviation Organization) publication: International Standards and recommended practices Aeronautical telecommunications Annex10 to the Convention of International
15、Civil Aviation VolumeI (ICAO Annex10 VolumeI) 1) 3 General construction requirements The design and construction of the indicator shall comply with the relevant requirements of BS3G100 and BS G101. The preferred case sizes for the indicators are the type3 and type6 cases given in BS G101. 4 Particul
16、ar requirements 4.1 Construction 4.1.1 The detailed construction and dial markings of the indicator shall comply with the relevant requirements of BS3G100 and BS G101. The presentation should generally conform to the recommendations given in the report of the United Kingdom Altimeter Committee 1) .
17、4.1.2 The barometric pressure setting shall be shown on counters clearly visible on the face of the indicator. The range of the barometric pressure setting shall encompass800mbar to1088mbar or shall be as declared. The markings shall be in millibars and, if required, in inches of mercury. It shall b
18、e possible to set the counter readings to0.5mbar values and, where practicable, a datum mark shall be provided to ensure that the indicated value of1013.25mbar can be accurately set. 4.1.3 The barometric pressure setting shall be moved by an adjusting knob readily accessible from the front of the in
19、dicator and preferably situated on the lower right hand corner of the bezel. The torque to operate this knob shall be between25mN m and50mN m and a safety device shall be provided to prevent damage when attempting to set beyond the limits of the pressure scale range. 4.1.4 Any pre-set device fitted
20、for adjustment of the relationship between the barometric pressure setting and the altitude indication shall be such that the relationship which is set up is not capable of being inadvertently disturbed. The device shall not be accessible from the front of the indicator and the total possible correc
21、tion shall not exceed a range of 3mbar. 4.1.5 The pointer shall make one revolution per1000ft clockwise for increasing altitude. 4.1.6 A clear warning of failure shall be provided when the electrical power supply is inadequate for correct functioning of the system. This device and any additional fai
22、lure monitoring or warning devices shall themselves fail safe. 1) Obtainable from HMSO.BSG226:1979 2 BSI 01-2000 4.1.7 The relationship between the movement of the counters and the movement of the pointer shall be such as to ensure that the digits of the counter registering “thousands” change during
23、 the interval when the pointer travels between the“950” and“0” marks on the dial with altitude readings either increasing or decreasing. 4.1.8 Integral lighting, when fitted, shall comply with the requirements of BS G191. 4.1.9 The indicator window shall be coated in accordance with the requirements
24、 of BS G211. 4.1.10 If the indicator includes an internal method of static pressure error correction (PE correction), the aircraft type and model number shall be marked on the indicator label. If the indicator accepts correction signals from an external source which is defined for a particular aircr
25、aft, that aircraft type and model number shall be marked on the label of the external unit. A clear indication shall be incorporated in the altimeter presentation to identify when the PE correction is not operative. 4.1.11 Type B systems shall have a digitizer coupled into the altitude function so a
26、s to render it independent of the barometric pressure setting mechanism and referenced to the standard pressure setting of1013.25mbar. (SeeICAO Annex10 VolumeI, paragraph 3.8.7.12.2.5) 4.1.12 If a “press to test” switch is fitted for ground test purposes, provision shall be made to guard against its
27、 inadvertent use in flight. 4.1.13 After separate operation arising out of inadvertent disconnection or operation of ground test facilities, the various parts of the system shall re-synchronize within the individual specification tolerances over the whole altitude range. 4.1.14 In the case of an ide
28、ntified failure of the system, failure monitoring devices shall ensure an open circuit of the encoder output common return lead. 4.2 Performance 4.2.1 The response rate shall be such that the rate of follow of the indicator is not less than20000ft/min. 4.2.2 Calibration of the sensing mechanism and
29、of the barometric pressure adjustment system with which these counter pointer altimeter indicators operate shall be in accordance with Table 1A and Table 1B(1) of BS G199. In cases where integral PE correction is incorporated, the relevant pressure altitude relationship shall be published in the par
30、ticular specification for the instrument concerned. The exterior of the altimeter case, shall be clearly marked “PE corrected for (type and variant of aircraft)”. 4.2.3 Pressure values in millibars corresponding to altitudes in feet within the range covered by this specification, together with the r
31、equired accuracy, are given in Table 1. Table 1 Altitudes, pressures and permissible errors 4.2.4 The altitude encoder fitted in a typeB system shall comply with the following requirements. 4.2.4.1 The electrical signal output shall be compatible with the secondary surveillance radar transponder wit
32、h which it is to be used. (For code structure seeTable B in Part1 of ICAO Annex10 VolumeI.) NOTENo static error correction applied. Altitude Pressure Permissible error at+20 5 C a 1mbar expressed in feet ft 10 3 2 1 0 1 2 3 4 5 10 20 30 40 50 60 70 80 mbar 1088.66 1050.41 1013.25 977.16 942.13 908.1
33、2 875.10 843.07 696.81 465.63 300.89 187.54 115.98 71.72 44.38 27.62 ft 40 30 20 30 30 30 30 30 35 50 75 110 150 200 300 400 27.3 28.1 31.6 36.9 51.2 73.0 110.9 179.4 290.1 471.7 768.7 a Or at such temperature as may be required by the individual specification (see5.2.3).BSG226:1979 BSI 01-2000 3 4.
34、2.4.2 The encoder shall have isolating diodes incorporated within the unit in each encoding lead, to allow several encoders within the aircraft to be wired in parallel but controlled through switching of the common lead. 4.2.4.3 Transition between adjacent signal codes shall take place within50ft of
35、 the nominal altitude indicator reading with the baroscale set at1013.25mbar. (For nominal transition altitudes seeTable B in Part1 of ICAO Annex10 VolumeI.) 4.2.4.4 The design aim shall be that, under all altitude conditions, the voltage between the signal lines when “turned on” and the common retu
36、rn line shall not exceed2V, or the equivalent resistance, for any current in the range of0.38mA to5mA. The resistance of the encoder against current, or, in the case of the voltage source, the equivalent resistance against current, shall be declared for each type of encoder, on a log-log graph as sh
37、own in Figure 1. This graph shall also include equivalent resistance lines corresponding to2V and5V. The encoder resistance curve shall not exceed the2V line in the current range0.38mA to0.75mA. In the current range0.75mA to5mA, the resistance curve should preferably not exceed the2V line, but in an
38、y case shall not exceed the5V line. If the resistance curve exceeds5V within the latter current range, the current value at which it reaches5V shall be declared as a limitation, which shall be taken into account in parallel operation. Any resistance, in excess of normal wiring resistance, in the com
39、mon return lead should be avoided. If any excess resistance is included, this shall be declared. 4.2.4.5 The voltage between the signal lines when “turned off” and the common return line shall be not less than18.5V or the resistance shall be not less than100k7 under any conditions. The maximum volta
40、ge shall not exceed30V. 5 Tests 5.1 General 5.1.1 Tests shall be carried out to prove compliance with all the requirements of this BritishStandard. Three kinds of tests are specified as follows. a) Type tests. To be carried out on representative sample(s) to prove the design. b) Production routine t
41、ests. To be carried out on all units manufactured in accordance with this standard. c) Production quality tests. To be carried out on samples specified in the individual specification. 5.1.2 For the guidance of users, minimum tests recommended to verify the serviceability of units manufactured in co
42、mpliance with this BritishStandard are indicated in Appendix A. 5.2 Test conditions 5.2.1 Pressure cycling or exercising, other than that produced by normal variation of terrestrial barometric pressure, shall not be applied to the indicators for at least1h before the ranging tests are performed. 5.2
43、.2 Unless the equipment used to test the altimeter is fitted with automatic means of correction, readings shall be corrected for latitude, height above mean sea level and temperature, as specified for barometers in BS2520. 5.2.3 Unless otherwise specified, tests shall be carried out at a temperature
44、 of20 5 C and with electrical power supplies at nominal values as defined in BS3G100-3:1972. NOTEOn a number of modern aircraft the temperature behind the instrument panel will be above the temperature of+20 C at which tests are carried out in accordance with this specification and normal performanc
45、e may be required in such circumstances at a higher temperature. Where a higher temperature is required, this will be stated in the individual specification and the performance of the indicator at such temperature is to be declared. 5.2.4 Pressure-measuring equipment used for calibrating altimeters
46、manufactured in compliance with this BritishStandard shall not have errors greater than 0.2mbar. This shall be periodically verified either directly by the National Physical Laboratory or against a reference standard certified by the National Physical Laboratory. In the latter case, the errors or un
47、certainty of the reference standard shall be taken into account, such that the absolute errors of the test instrument do not exceed0.2mbar.BSG226:1979 4 BSI 01-2000 6 Type tests 6.1 Ranging accuracy and hysteresis test NOTEThis is a combined test in which accuracy and hysteresis are established in o
48、ne test. 6.1.1 Systems not including PE correction. With the ground pressure set to1013.25mbar approached from a lower reading, and with the indicator in the normal position with the dial upright and in a vertical plane, the errors shall not exceed the amounts specified in Table 1. The test shall be
49、 made with pressure decreasing at approximately3000ft/min and with pressure increasing at approximately6000ft/min. The rate of change of pressure shall be reduced progressively as the check points are approached to avoid passing the check point. Movement of the pointer during decreasing as well as increasing pressure shall be smooth and free from erratic motion when the pressure is changed uniformly. 6.1.2 Systems including internally generated PE correction. If the correction is a function of altitude, the ranging accuracy test shall be carried out in acco
