1、AEROSPACESTANDARDAS404 REV.CIssued 1948-11Reaffirmed 2008-02Revised 2001-07Superseding AS404BElectric Tachometer: Magnetic Drag (Indicator & Generator)FOREWORDChanges in this Revision are format/editorial only.1. SCOPE:This Aeronautical Standard covers magnetic drag tachometers with or without built
2、-in synchroscopes.1.1 Purpose:To specify minimum requirements for Electric Tachometers primarily for use in reciprocating engine powered civil transport aircraft, the operation of which may subject the instruments to the environmental conditions specified in Section 3.3.2. REFERENCES:NACA Report 123
3、53. GENERAL REQUIREMENTS:3.1 Materials and Workmanship:3.1.1 Materials: Materials shall be of a quality which experience and/or tests have demonstrated to be suitable and dependable for use in aircraft instruments.3.1.2 Workmanship: Workmanship shall be consistent with high-grade aircraft instrument
4、 manufacturing practice.SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infr
5、ingement arising therefrom, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions. Copyright 2008 SAE International All rights reserved. No part
6、 of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: 724-
7、776-4970 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE AS404 Revision C- 2 -3.2 Identification:The following information shall be legibly and permanently marked on the instrument or attached thereto:a. Name of Instrumentb. SAE AS404Cc. Manufactu
8、rers Part Number.d. Manufacturers Serial number or date of manufacture.e. Manufacturers name and/or trade mark.f. Range.3.3 Environmental Conditions:The following conditions have been established as minimum design requirements. Tests shall be conducted as specified in Sections 5, 6 and 7.3.3.1 Tempe
9、rature: When installed in accordance with the instrument manufacturers instructions, the instrument shall function over the range of ambient temperatures shown in Column A below and shall not be adversely affected by exposure to the range of temperatures shown in Column B below:3.3.2 Humidity: The i
10、nstrument shall function and shall not be adversely affected when exposed to any relative humidity in the range from 0 to 95% at a temperature of approximately 32 C.TABLE 1Instrument Location A BPowerplant Accessory Compartment -30 to 70 C -65 to 100 CHeated Areas (temperature con- -30 to 50 C -65 t
11、o 70 Ctrolled)SAE AS404 Revision C- 3 -3.3.3 Vibration: When installed in accordance with the instrument manufacturers instructions, the instrument shall function and shall not be adversely affected when subjected to vibrations of the following characteristics:3.3.4 Altitude: The instrument shall fu
12、nction and shall not be adversely affected when subjected to a pressure and temperature range equivalent to -1000 to 40,000 feet standard altitude, per NACA Report 1235, except as limited by the application of paragraph 3.3.1. The instrument shall not be adversely affected following exposure to an a
13、mbient pressure of 50 in Hg absolute.3.4 Radio Interference:The instrument shall not be the source of objectionable interference, under operating conditions at any frequencies used on aircraft either by radiation or feed-back, in electronic equipment installed in the same aircraft as the instrument.
14、3.5 Magnetic Effect:The magnetic effect of the indicator shall not adversely affect the operation of other instruments installed in the same aircraft.4. DETAIL REQUIREMENTS:4.1 Indicator:4.1.1 Indication: Engine speed shall be indicated by means of one or more moving pointers or dials.Relative movem
15、ent of the pointer with respect to the dial shall be clockwise for increasing RPM.4.1.2 Dial Visibility: The pointers and all dial markings shall be visible from any point within the frustum of a cone whose side makes an angle of not less than 30 with the perpendicular to the dial and whose small di
16、ameter is the aperture of the instrument case. The distance between the dial and the cover glass shall be a practical minimum and shall not exceed 0.200 inch.TABLE 2Inst. Location in AirframeCyclesPer SecondMaximum DoubleAmplitude (Inches)MaximumAccelerationPower Plant Mounted 5-150 .100 20 gFuselag
17、e 5-500 .036 5 gPanel or Rack (Vibration 5-50 .020 1.5 gIsolated)SAE AS404 Revision C- 4 -4.1.3 Dial Markings:4.1.3.1 Finish: Unless otherwise specified by the user, matte white material should be applied to all major graduations, numerals, and pointers. Non-functional surfaces should be a durable d
18、ull black.4.1.3.2 Graduations: All graduations shall be multiples of 10 RPM. The increment between graduations shall not exceed 2-1/2% of full scale, above 600 RPM.4.1.3.3 Numerals: Sufficient numerals shall be marked to identify positively and quickly all graduations.4.1.3.4 Instrument Name: The de
19、signation “RPM“, plus such other nomenclature as may be necessary, shall be legibly marked on the dial and may be of the same finish as the numerals.4.1.3.5 Sealing: The indicator case may be either gasket sealed or hermetically sealed.4.2 Generator:The generator shall be designed to operate in eith
20、er direction of rotation and in any position.5. TEST CONDITIONS:5.1 Atmospheric Conditions:Unless otherwise specified all tests required by this Aeronautical Standard shall be conducted at an atmospheric pressure of approximately 29.92 inches of mercury and at an ambient temperature of approximately
21、 25 C and a relative humidity not greater than 85%. When tests are conducted with the atmospheric pressure or the temperature substantially different from these values, allowances shall be made for the variation from the specified conditions.5.2 Vibration (to minimize friction):Unless otherwise spec
22、ified all tests for performance may be made with the instrument subjected to a vibration of 0.002 to 0.005 inch double amplitude at a frequency of 1500 to 2000 cycles per minute.The term double amplitude as used herein indicates total displacement from positive maximum to negative maximum.5.3 Vibrat
23、ion Equipment:Vibration equipment shall be used which will provide frequencies and amplitudes consistent with the requirements of Section 3.3.3 with the following characteristics.5.3.1 Linear Motion Vibration: Vibration equipment for airframe structure-mounted or powerplant-mounted instruments or eq
24、uipment shall be such as to allow vibration to be applied along each of three mutually perpendicular axes of the instrument.SAE AS404 Revision C- 5 -5.3.2 Circular Motion Vibration: Vibration equipment for instruments located on the panel or rack (with shockmounts) shall be such that a point on the
25、instrument case will describe a circle, in a plane inclined 45 degrees to the horizontal plane, the diameter of which is equal to the double amplitude specified.5.4 Position:Unless otherwise specified, all tests shall be conducted with the instrument mounted in its normal operating position.6. INDIV
26、IDUAL PERFORMANCE REQUIREMENTS:All instruments or components of such shall be subjected to whatever tests the manufacturer deems necessary to demonstrate specific compliance with this Aeronautical Standard, including the following requirements when applicable.6.1 Scale Error at Room Temperature:The
27、tachometer indicator shall be connected to its generator and the generator operated at the shaft speeds within the ranges specified in Table 3. The scale error at any speed shall not exceed the values specified in Table 3 with the speed increasing or decreasing. When the speed is held constant at an
28、y point on the scale, the pointer shall not oscillate over a range greater than 20 RPM from 600 RPM to full-scale indication.6.2 Dielectric:Ungrounded instruments or grounded instruments prior to connection of the internal ground wire shall be tested by either the method of inspection of paragraph 6
29、.2.1 or 6.2.2.6.2.1 Insulation Resistance: The insulation resistance measured at 200 volts DC for five seconds between all electrical circuits connected together and the metallic case shall not be less than 5 megohms. Insulation resistance measurements shall not be made to circuits where the potenti
30、al will appear across elements such as windings, resistors, capacitors, etc., since this measurement is intended only to determine adequacy of insulation.TABLE 3GeneratorDrive ShaftSpeedRPMCorrectIndicatedSpeedRPMScale ErrorToleranceRPM300 - 1400 600 - 2800 251500 - 2250 3000 - 4500 40SAE AS404 Revi
31、sion C- 6 -6.2.2 Overpotential Tests: Equipment shall not be damaged by the application of a test potential between electrical circuits, and between electrical circuits and the metallic case. The test potential shall be a sinusoidal voltage of a commercial frequency with an RMS value of five times t
32、he maximum circuit voltage or per paragraphs 6.2.2.1 or 6.2.2.2 whichever applies. The potential shall start from zero and be increased at a uniform rate to its test value. It shall be maintained at this value for five seconds, and then reduced at a uniform rate to zero.Since these tests are intende
33、d to insure proper electrical isolation of the circuit components in question, these tests shall not be applied to circuits where the potential will appear across elements such as windings, resistors, capacitors, etc.6.2.2.1 Hermetically sealed instruments shall be tested at 200 volts RMS.6.2.2.2 Ci
34、rcuits that operate at potentials below 15 volts and contain low voltage elements such as transistors, doides, capacitors and special signal generators are not to be subjected to overpotential tests.6.3 Position Error:The change in pointer indication with change in instrument position from normal po
35、sition shall not exceed 25 RPM.6.4 Sealing:This test shall apply to hermetically sealed instruments only. The indicator shall be immersed in a suitable liquid, such as water. The absolute pressure of the air above the liquid shall then be reduced to approximately 1 inch of mercury and maintained for
36、 1 minute, or until air bubbles substantially cease to be given off by the liquid, whichever is longer. The absolute pressure shall then be increased to 2-1/2 inches Hg. Any bubbles coming from within the indicator case shall be considered as leakage and shall be cause for rejection. Bubbles which a
37、re the result of entrapped air in the various exterior parts of the case shall not be considered as a leak.A helium leak detector or other means of test, equal or superior in sensitivity to the immersion method described above, may be used. Where a leak detector is employed for conducting the test,
38、the leak rate shall not exceed 1 micro-cubic foot per hour at a pressure differential of approximately 1 atmosphere.If the indicator incorporates non-hermetically sealed attachments, such as a case extension, these components may be removed prior to the Sealing Test.SAE AS404 Revision C- 7 -7. QUALI
39、FICATION TESTS:As many instruments as may be deemed necessary to demonstrate that all instruments will comply with the requirements of this section shall be tested in accordance with the manufacturers recommendations.7.1 Low Temperature:The instrument shall be subjected to -30 C for three hours. The
40、 change in indication from the reading obtained at room temperature shall not exceed one percent of full scale. The instrument may be operated at 2000 RPM or half scale, whichever is higher, for a period of 10 minutes before making this scale error test. The force required to turn the generator shaf
41、t while and after it has been subjected to a temperature of minus 55 C for two hours, shall not exceed 8 pound inches. No damage to the generator shall result from this test.7.2 High Temperature:The instrument shall be subjected to a temperature of 70 C for a period of three hours. The change in ind
42、ication from the readings obtained at room temperature shall not exceed one percent of full scale for the range 600-2800 RPM and shall not exceed one and one-half percent of full scale for the range from 3000 to 4500 RPM.7.3 Extreme Temperature Exposure:The instrument shall, after alternate exposure
43、 to ambient temperatures specified in Column B of Section 3.3.1 for a period of 24 hours each and a delay of 3 hours at room temperature following completion of the exposure, meet the requirements of Section 6.1. During the high temperature exposure, the generator shall be operating at a shaft speed
44、 equivalent to half-scale indicator reading and shall be supplying full-rated electrical load for that speed. There shall be no evidence of damage as a result of exposure to the extreme temperatures specified herein.7.4 Magnetic Effect:The magnetic effect of the indictor shall be determined in terms
45、 of the deflection of a free magnet, approximately 1-1/2 inches long, in a magnetic field with a horizontal intensity of 0.19 0.01 gauss when the indicator is held in various positions on an east-west line with its nearest part 12 inches from the center of the magnet. This test shall first be made w
46、ith the indicator not operating and then shall be repeated with the indicator in normal operation. The maximum deflection of the free magnet shall not exceed 5 degrees for any pointer or dial position.SAE AS404 Revision C- 8 -7.5 Vibration:7.5.1 Resonance: The instrument, while operating and with va
47、rious pointer settings throughout the range, shall be subjected to a resonant frequency survey of the appropriate range specified in Section 3.3.3 in order to determine if there exists any resonant frequencies of the parts. The amplitude used may be of any convenient value that does not exceed the m
48、aximum double amplitude and the maximum acceleration specified in Section 3.3.3.The instrument shall then be subjected to vibration at the appropriate double amplitude or maximum acceleration specified in Section 3.3.3 at the resonant frequency for a period of one hour in each axis or with circular
49、motion vibration whichever is applicable. When more than one resonant frequency is encountered with vibration applied along any one axis, a test period may be accomplished at the most severe resonance, or the period may be divided among the resonant frequencies, whichever shall be considered most likely to produce failure. The test period shall not be less than one-half hour at any resonant mode. When resonant frequencies are not apparent within the spec
