1、AEROSPACESTANDARDAS408 REV.CIssued 1948-11Reaffirmed 2008-02Revised 2001-07Superseding AS408BPressure Instruments - Fuel, Oil and Hydraulic(Reciprocating Engine Powered Aircraft)FOREWORDChanges in this Revision are format/editorial only.1. SCOPE:This Aeronautical Standard covers two basic types of f
2、uel, oil and hydraulic pressure instruments as follows:Type I - Direct IndicatingType II - Remote IndicatingThis Aerospace Standard does not apply to engine mounted torque meter systems.1.1 Purpose:This Aerospace Standard establishes the essential minimum safe performance standards for fuel, oil and
3、 hydraulic pressure instruments primarily for use with reciprocating engine powered transport aircraft, the operation of which may subject the instruments to the environmental conditions specified in Section 3.3.2. REFERENCES:NACA Report 12353. GENERAL REQUIREMENTS:3.1 Materials and Workmanship:3.1.
4、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.SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. Th
5、e use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement 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, revi
6、sed, or cancelled. SAE invites your written comments and suggestions. Copyright 2008 SAE International All rights reserved. No part 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 oth
7、erwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: 724-776-4970 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.orgSAE AS408 Revision C- 2 -3.1.2 Workmanship: Workmanship shall be
8、 consistent with high grade aircraft instrument manufacturing practice.3.2 Identification:The following information shall be legibly and permanently marked on the instrument or attached thereto:a. Name of instrumentb. SAE AS408Cc. Manufacturers part numberd. Manufacturers serial number or date of ma
9、nufacturee. Manufacturers name and/or trademarkf. Rangeg. Rating (Electrical, vacuum, etc.)h. Explosion category3.3 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 Temperature:
10、When installed in accordance with the instrument manufacturers instructions, the instrument shall function over the range of ambient temperature shown in Column A below and shall not be adversely affected by exposure to the range of temperature shown in Column B below:TABLE 1Instrument Location A BP
11、ower Plant Compartment -30 to +100 C -65 to +100 CHeated Areas (Temperature Controlled) -30 to +70 C -65 to +70 CUnheated Areas (Temperature Controlled) -55 to +70 C -65 to +70 CPower Plant Accessory Compartment -30 to +100 C -65 to +100 CSAE AS408 Revision C- 3 -3.3.2 Altitude: When installed in ac
12、cordance with the instrument manufacturers instructions, the instruments shall function and shall not be adversely affected following exposure 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 Parag
13、raph 3.3.1. The instrument shall not be adversely affected when subjected to an ambient pressure of 50 inches of mercury absolute.3.3.3 Vibration: When installed in accordance with the instrument manufacturers instructions, the instruments shall function and shall not be adversely affected when subj
14、ected to vibrations of the following characteristics:3.3.4 Humidity: The instruments 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 +70 C.3.4 Explosion Category:The instrument component, when inten
15、ded for installation either in uninhabited areas of non-pressurized aircraft or in non-pressurized areas of pressurized aircraft, shall not cause an explosion when operated in an explosive atmosphere. The component shall meet the requirements applicable to the explosion category below. Specifically,
16、 any instrument component which can be an ignition source and is intended for installation in an area in which combustible fluid or vapor may result from abnormal conditions, e.g., fuel line leakage, shall meet the requirements of Category I. If the intended location is an area where combustible flu
17、id or vapor can occur during normal operation, e.g., fuel tank, the instrument component shall meet the requirements of Category II listed below:TABLE 2Instrument Locationin AirframeCyclesper SecondMaximum DoubleAmplitude (Inches)MaximumAccelerationPower Plant Mounted 5-150 0.100 20 gWings and Empen
18、nage 5-500 0.036 10 gFuselage 5-500 0.036 5 gPanel or Rack (Vibration Isolated) 5-50 0.020 1.5 gSAE AS408 Revision C- 4 -3.5 Fire Hazard:The instruments shall be so designed to safeguard against hazards to the aircraft in the event of malfunction or failure, and the maximum operating temperature of
19、surfaces of any instrument component, whether functioning correctly or malfunctioning, contacted by combustible fuel or vapor shall not exceed +200 C due to self-heating.3.6 Radio Interference:The instruments shall not be the source of objectionable interference, under operating conditions at any fr
20、equencies used on aircraft, either by radiation or feedback, in electronic equipment installed in the same aircraft as the instruments.3.7 Magnetic Effect:The magnetic effect of the instruments shall not adversely affect the performance of other instruments installed in the same aircraft.TABLE 3Cate
21、gory Definition RequirementI Explosion proofed: Case notdesigned to preclude flame orexplosion propogationParagraph 7.11.1II Explosion proofed: Case designedto preclude flame or explosionpropogationParagraph 7.11.2III Hermetically sealed Paragraph 6.6IV Instrument not capable of causingan explosionS
22、hall not be capable ofproducing a capacitive orinductive spark of morethan 0.2 millijoules ofenergy or a contact sparkof more than 4.0 milli-joules of energy.SAE AS408 Revision C- 5 -3.8 Suction or Overpressure:Pressure or suction instruments, as applicable, shall not be adversely affected when subj
23、ected to suction or overpressure as specified in the following table:3.9 De-Compression:When installed in accordance with the instrument manufacturers instructions the instrument shall function and not be adversely affected following exposure to a pressure decrease from 22 to 2 inches of mercury in
24、2 seconds.4. DETAIL REQUIREMENTS:4.1 Indicating Means:The pressure instrument shall indicate by means of a visual display such as pointer(s) moving over a fixed dial, digital counter, etc.4.1.1 Finish: Unless otherwise specified by the user, mattewhite material shall be applied to all graduations, n
25、umerals, pointers and indication means.Non-functional surfaces and markings shall be durable dull black.4.1.2 Graduations: The graduations shall be arranged to provide the maximum of readability consistent with the accuracy of the instrument.4.1.3 Numerals: The display shall include sufficient numer
26、als to permit quick and positive identification of each graduation. Numerals shall distinctly indicate the graduation to which each applies.TABLE 4Maximum IndicatedPressure - PSIOverpressurePercent of Maximum IndicatedPressureSuctionPercent of Maximum SuctionOil and with the pressure decreasing, the
27、 pressure shall be brought down to, but shall not fall below the pressure specified to give the desired reading. The scale errors at room temperature of direct reading instruments shall not exceed 2% of the full scale value and transmitters shall not exceed 2.0% of the full scale value. The scale er
28、rors of remote indicators shall be determined by applying the specified electrical inputs. The scale errors at room temperature shall not exceed 0.75% of the full scale value.6.3 Friction Error:The instrument shall be tested for friction error at each test point. The pressure shall be so increased a
29、s to bring the pointer of the direct reading instrument or test instrument (for test of transmitters) approximately to the desired reading and then held constant while two readings are taken, the first before the direct reading instrument or transmitter is tapped and the second after the instrument
30、is tapped. The difference between any such readings is the friction error and shall not excess 1% of the full scale value. The friction error of remote indicators shall be determined in a similar manner by applying suitable electrical inputs. The friction error shall not exceed 1% of the full scale
31、value.6.4 Position Error:With sufficient pressure applied to obtain a reading of approximately mid-scale, the direct reading instrument or transmitter shall be held in each of several different positions. The change in the reading of a direct reading instrument or test instrument (for test of transm
32、itters), with change in position from the normal test position shall not exceed 1% of the full scale value. The position error of remote indicators shall be determined in a similar manner by applying suitable electrical inputs.The position error shall not exceed 0.5% of the full scale value.6.5 Leak
33、age (Pressure Element):With pressure applied to produce a full scale reading, the connection tubing shall then be sealed at a point within 2 inches of the pressure connection. During a period of 5 minutes, there shall be no change in reading.6.6 Sealing:Hermetically sealed instruments shall be teste
34、d for leaks by means of a mass spectrometer type of helium leak detector or equivalent. The leak rate shall not exceed 76 micron cubic foot per hour at a pressure differential of one atmosphere.SAE AS408 Revision C- 10 -6.7 Differential Pressure Error:This test is applicable to differential pressure
35、 instruments only. The applicable pressure shall be applied to the vent boss. Pressures shall be so applied to the pressure boss that the pressure differential between the pressure and vent bosses is equal to the required test pressure. The scale errors shall not exceed the tolerances specified in P
36、aragraph 6.2.7. QUALIFICATION TESTS:As many instruments or components deemed necessary by the manufacturer to demonstrate that all instruments will comply with the requirements of this section shall be tested in accordance with his recommendation.7.1 Temperature Characteristics:7.1.1 Low Temperature
37、 Operation: The instrument shall be subjected to the applicable low ambient temperature listed in Column A of Paragraph 3.3.1 for a period of five hours without operating. The instrument shall be subjected to at that temperature, a scale error test and the scale errors of direct reading instruments
38、shall not exceed 3.5% of the full scale value and transmitters shall not exceed 3.0% of the full scale value. The scale errors of remote indicators shall not exceed 1.0% of the full scale value.7.1.2 High Temperature Operation: The instrument shall be subjected to the applicable high ambient tempera
39、ture listed in Column A of Paragraph 3.3.1 for a period of five hours without operating.(Electrical equipment shall be energized). The instrument shall be subjected to, at that temperature, a scale error test and the scale errors of direct reading instruments shall not exceed 3.5% of the full scale
40、value and transmitters shall not exceed 3.0% of the full scale value. The scale errors of remote indicators shall not exceed 1.75% of the full scale value.7.1.3 Extreme Temperature Exposure: The instrument shall be exposed to the applicable low and high temperatures listed in Column B of Paragraph 3
41、.3.1 for a period of 24 hours at each extreme temperature, without operating. After a delay of three hours at room temperature, the instrument shall meet the applicable individual performance tests (Section 6, except 6.1) at room temperature.There shall be no evidence of damage as a result of exposu
42、re to the extreme temperatures specified.7.1.4 Altitude: The instrument shall be subjected to the ambient temperature and pressure listed in Paragraph 3.3.2 for a period of three hours while operating. The instrument shall meet the requirements of Paragraphs 7.1.1 and 7.1.2 while at these conditions
43、.The instrument shall be exposed alternately to 50 inches Hg absolute and three inches Hg absolute, nonoperating. The instrument shall then meet the applicable individual performance tests (Section 6 except 6.1) at atmospheric pressure following this test.SAE AS408 Revision C- 11 -7.2 Vibration:7.2.
44、1 Resonance: The instrument while operating shall be subjected to a resonant frequency survey of the appropriate range specified in Paragraph 3.3.3 in order to determine if there exists any resonant frequencies of the parts. The amplitude used may be any convenient value that does not exceed the max
45、imum double amplitude and the maximum acceleration specified in Paragraph 3.3.3. The instrument shall then be subjected to vibration at the appropriate maximum double amplitude or maximum acceleration specified in Paragraph 3.3.3 at the resonant frequency for a period of one hour along each axis. If
46、 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
47、 not be less than one-half at any resonant made. When resonant frequencies are not apparent within the specified frequency range, the instrument shall be vibrated for two hours along each axis in accordance with the vibration requirements schedule (Paragraph 3.3.3) at the maximum double amplitude an
48、d the frequency to provide the maximum acceleration.7.2.2 Cycling: The instrument, while operating, shall be tested with the frequency cycled between limits specified in Paragraph 3.3.3 in 15 minute cycles for a period of one hour along each axis at an applied double amplitude specified in Paragraph
49、 3.3.3, or an acceleration specified in Paragraph 3.3.3, whichever is the limiting value or a total of three hours for circular motion vibration whichever is applicable. Pointer variation and oscillation shall not exceed 1.5% of the full scale value for direct reading instruments and 1.5% for pointer oscillation and 1.0% for pointer variation of the full scale value for remote indicators. After the completion of this vibration test, no damage shall be evident and the instrument shall meet the applicable individual performa
