1、BRITISH STANDARD BS 2G 112: 1956 Specification for Air-driven directional gyroscopes for aircraftBS2G112:1956 This British Standard, having been approved by the Aircraft Industry Standards Committee and endorsed by the Chairman ofthe Engineering Divisional Council, was published under theauthority o
2、f the General Council of the Institution on 19April1956 BSI12-1999 The following BSI references relate to the work on this standard: Committee reference ACE/30 Draft for comment CV (ACE)5065 ISBN0580341003 Foreword BS G112:1949, “Direction indicator for aircraft” specified requirements for the gener
3、al and detailed construction, and for the accuracy of both air-driven and electrically-operated instruments. This standard has been prepared, under theauthority of the Aircraft Industry Standards Committee, to provide an up-to-date specification for air-driven directional gyroscopes in the light of
4、experience gained in the application of the relevant requirements of G112, which it supersedes. The requirements of G112 for electrically-operated instruments are covered by BS G122, “Aircraft magnetic compass, remote reading (gyro stabilized).” Information has been added relating to the incidence o
5、f testing, and recommendations included in respect of tests to verify the serviceability of the instruments. 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
6、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, 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
7、 indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No. Date CommentsBS2G112:1956 BSI 12-1999 i Contents Page Foreword Inside front cover 1 Scope 1 2 Definition 1 Section 1. General requirements 3 Case size 1 4 Fixing holes 1 5 General construction 1
8、 Section 2. Particular requirements 6 Construction 1 7 Air filter 1 8 Robustness 1 9 Air outlet connections 1 10 Moment of momentum 1 11 Lubrication 1 12 Balance 1 13 Marking 1 Section 3. Tests 14 General 2 15 Air consumption 2 16 Starting test 2 17 Gyroscope drift test 2 18 Roll, pitch and yaw test
9、 2 19 Rotation test 2 20 Turning test 3 21 Backlash test 3 22 Temperature test 3 23 Compass interference 3 24 Vibration tests 3 25 Endurance tests 3 26 Impact acceleration test 3 27 Climatic tests 4 28 Filter pressure drop test 4 29 Routine production tests 4 Appendix Serviceability tests 5 Figure 1
10、 Air connections for directional gyroscope 5 Table 1 Climatic cycle test points 4ii blankBS2G112:1956 BSI 12-1999 1 1 Scope This British Standard specifies the design requirements, performance and test procedure for air-driven directional gyroscopes for aircraft. 2 Definition For the purpose of this
11、 British Standard the following definition shall apply: directional gyroscope an instrument used on aircraft to indicate changes in heading of the aircraft by reference to a gyroscope coupled mechanically to an indicating system comprising a reference mark or pointer and a compass card. It is also r
12、eferred to as a “direction indicator” Section 1. General requirements 3 Case size The instrument case shall be not more than 4“ in. wide,5! in. high and 5“ in. deep. 4 Fixing holes The attachment of the instrument shall be effected by four fixing holes spaced4 1 / 6 in. laterally and3 29 / 32 in. ve
13、rtically with integral2BA stiffnuts: otherwise the fixing holes should be in accordance with those specified for aircraft instrument cases inBS G100, “General requirements for electrical equipment and indicating instruments for aircraft.” 5 General construction The instrument shall be sound and suit
14、able for its purpose and shall comply with the relevant requirements of BS G100. Section 2. Particular requirements 6 Construction a) The instrument shall consist of a gyroscope rotating about a substantially horizontal axis and mounted in a gimbal system the outer axis of which is parallel to the v
15、ertical axis (OZ) of the aircraft. b) The instrument shall be designed to operate with an air pressure difference from inlet to outlet of from3in. to5in. of mercury and with a maximum consumption of1.3cu.ft. of free air per minute. c) The rotor of the instrument shall start under normal temperature
16、conditions when a pressure difference from inlet to outlet of1in. of mercury is applied, and shall settle to its datum position rapidly. d) The preferred presentation shall be a vertical compass card driven through unit ratio gearing by the outer gimbal, which shall be read against a fiducial mark f
17、ixed to the instrument case. e) The gyroscope shall possess complete freedom about the outer gimbal axis and not less than 55 (but preferably 85 ) about the inner gimbal axis. f) Means shall be provided to maintain the axis of spin of the gyroscope substantially horizontal. g) Means shall be provide
18、d for bringing the compass card to any desired position to synchronize with the aircraft compass. The operating knob shall be labelled “SYN” (Synchronize), and shall be spring-loaded outwards (push to engage). h) A pointer shall be provided which can be set to any desired heading and the operating k
19、nob shall be labelled “Set Heading” or “Set HDG”. 7 Air filter The instrument shall have a replaceable and efficient air filter at the air inlet to prevent ingress of dust. The filter shall satisfy the requirements of the pressure drop test specified in Clause28. 8 Robustness The instrument shall be
20、 so designed that shock loads giving an acceleration of50g in any direction do not impair the performance. 9 Air outlet connections A suitable arrangement of air outlet connections is shown inFigure 1. 10 Moment of momentum The angular moment of momentum shall be as high as possible consistent with
21、size. 11 Lubrication The rotor and gimbal bearings shall be designed to give satisfactory performance throughout the operating life of the instrument without re-lubrication. 12 Balance The rotor shall be dynamically balanced about its axis of spin. 13 Marking In addition to the marking required by B
22、S G100, instruments shall be marked with the latitude at which the instrument is compensated for the earths rotation.BS2G112:1956 2 BSI 12-1999 Section 3. Tests 14 General a) The requirements of this section are based upon the assumption that testing is carried out at the same latitude as that for w
23、hich the instrument is compensated. b) Tests shall be made to prove compliance with all the requirements of this British Standard. It is not intended or recommended that complete tests shall be made on every instrument supplied. Two kinds of test therefore are specified as follows: Type tests. (Clau
24、ses15 to28) which shall be made on representative samples of each particular design and range of instrument, as follows: i) Proof tests a sample instrument shall be subjected to all the tests specified in Clauses15 to23 inclusive. ii) Endurance tests a second sample instrument shall be subjected to
25、the tests specified in Clauses24, 25 and26. iii) Climatic tests a further sample instrument shall be subjected to the tests specified in Clause27. Routine production tests. (Clause29) which shall be made on every instrument manufactured in accordance with the British Standard. c) The minimum tests r
26、ecommended to verify the serviceability of instruments manufactured in compliance with this British Standard are indicated in the Appendix. d) The following conditions shall apply to all tests, unless otherwise specified: i) The instrument shall be mounted in the normal position and tested at room t
27、emperature (15 to20 C). The normal position shall be that in which the plane of the front face of the mounting flange is vertical and the centre line through the top fixing screw holes is horizontal within! . ii) All tests shall be effected with a pressure difference from inlet to outlet of3“ ( in.
28、of mercury. iii) From the time of starting ten minutes shall be allowed for the instrument to attain maximum speed. During the first seven minutes of this period, exercising with an amplitude about each gimbal axis of approximately7“ , i.e.,15 total movement, may be permitted. Type tests 15 Air cons
29、umption With a pressure difference from inlet to outlet of3“ in. of mercury the instrument shall not consume more than1.2cuft of free air per minute reduced to a temperature of15 C and a pressure of760mm of mercury. 16 Starting test The instrument shall be connected to an air source incorporating a
30、relief valve, a manometer and an ON/OFF tap. The relief valve shall be set to control the pressure difference applied from inlet to outlet to a maximum of1in. of mercury. After setting the relief valve the tap shall be turned off and the rotor allowed to come to rest. When the rotor is stationary, t
31、he tap shall be turned on quickly and the air flow allowed to continue for30seconds; the tap shall then be turned off. The instrument shall be immediately rotated about a vertical axis and the card shall be stabilized. 17 Gyroscope drift test The instrument shall be mounted and operated as specified
32、 in Clause14 d). The compass card shall be set to0 (N), and the table shall be set for roll, pitch and yaw motion to give an amplitude of 1“ and a period of between57cycles per minute. The direction of motion of the table shall be reversed at regular intervals of approximately one minute duration. A
33、fter15minutes the table shall be stopped and arranged horizontally, when the drift of the card shall be not more than3 . 18 Roll, pitch and yaw test The instrument shall be mounted on a gyroscope test table and subjected to a roll, pitch and yaw test at an amplitude of 7“ and from5 to7 oscillations
34、per minute. Whilst running, the table shall be reversed at one minute intervals. Starting with the case and gyroscope vertical and the card reading0 (N), the drift of the card after the table has been in motion for ten minutes shall not exceed3 . 19 Rotation test The instrument shall be mounted on a
35、 turntable, the speed of rotation of which shall be between180 and210 per minute. After one complete revolution of the table the difference between card readings before and after the test shall not exceed1 . To eliminate backlash in the instrument gearing, the table shall be first rotated to the dat
36、um in the direction in which the test is to be made, and after completing the revolution the table shall not over-run the datum.BS2G112:1956 BSI 12-1999 3 20 Turning test With the instrument mounted on a turntable the speed of rotation shall be adjusted to complete one revolution in from28 to32secon
37、ds. The instrument shall then be rotated through six revolutions in both clockwise and counter-clockwise directions. After each six revolutions the drift of the gyroscope in azimuth shall not exceed3 . To eliminate backlash in the gear, the table shall be first rotated to datum in the direction in w
38、hich the test is to be made. The card reading shall then be noted, and on completion of the six revolutions the table shall not over-run the datum. 21 Backlash test With the instrument operating and mounted on a turntable, the table shall be rotated by hand in a clockwise direction until the table g
39、raduation mark is in line with the table datum, when the compass card reading shall be noted. The table shall then be rotated in a clockwise direction, through approximately90 and then shall be rotated in a counter-clockwise direction until the table graduation mark is again in line with the table d
40、atum. The compass card reading shall not differ from the previous reading by more than2 . When setting the table graduation mark to the table datum, the table shall not over-run the datum. 22 Temperature test a) With the gyroscope stationary, the instrument shall be maintained at a temperature of20
41、C for a period of three-quarters of an hour. Ten minutes shall be allowed for the gyroscope to attain maximum speed, during which time the turntable and the instrument may be exercised by rotation either clockwise or counter-clockwise. The turning test specified in Clause20 shall then be repeated at
42、20 C and the drift shall not exceed5 . b) After the test in a) the air supply shall beturned off and the temperature lowered to55 C. After three-quarters of an hour at that temperature the gyroscope shall start and continue to run on application of a pressure difference of3“ in. of mercury, as obser
43、ved by appropriate deflection of the card when the test table is turned in either direction. c) After the test in b) the air supply shall be turned off and the temperature gradually raised to+50 C. After three-quarters of an hour at that temperature the turning test specified in Clause20 shall be re
44、peated at+50 C, when the drift shall not exceed5 . d) After the test in c) the air supply shall be turned off and the temperature raised to+70 C. After three-quarters of an hour at that temperature the gyroscope shall start and continue to run on application of a pressure difference of3“ in. of merc
45、ury, as observed by appropriate deflection of the card when the test table is turned in either direction. e) On completion of the tests in a) to d) the instrument shall be subjected to and shall comply with the tests specified in Clauses16 to20 inclusive. 23 Compass interference The compass safe dis
46、tance shall be not more than5in. when measured in accordance with BSG100. 24 Vibration tests The instrument shall be subjected to the resonance and fatigue tests specified in BS G100 appropriate to its installation position and its declared vibration grade and shall comply with the tests specified i
47、n Clauses16 to21 inclusive. 25 Endurance tests The instrument shall be mounted and run on a rocking table so that both gimbal axes are rocked equally with a total movement of5 at5 to7 complete oscillations per minute for1000hours at normal temperature (15 C to20 C.). After this test the instrument s
48、hall comply with the requirements of the serviceability tests (see Appendix) without further lubrication or adjustment. NOTEIt may be necessary to connect the two gimbals flexibly to maintain the gyroscope spin axis at right angles to the outer gimbal axis during this test. 26 Impact acceleration te
49、st The instrument shall be subjected to the acceleration test specified in BS G100, Clause32, after which it shall comply with the requirements of the tests specified in Clauses15 to21 of this British Standard.BS2G112:1956 4 BSI 12-1999 27 Climatic tests The instrument shall be subjected to the climatic tests specified in BS G100, Clause25, and the following tests shall be applied at the appropriate points, defined inTable 1: 28 Filter pressure drop test One per cent of the filters shall be selected at random and subjected t
