1、AEROSPACESTANDARDAS793 REV.AIssued 1966-05Reaffirmed 2008-02Revised 2001-07Superseding AS793Total Temperature Measuring Instruments(Turbine powered Subsonic Aircraft)FOREWORDChanges in this Revision are format/editorial only.1. SCOPE:This standard covers three basic types of total-temperature-measur
2、ing instruments used as a means of determining the total temperature developed by adiabatic heating of the air due to motion of the aircraft through the air.Type I - Flush-type total-temperature sensorType II - Probe-type total-temperature sensor (electrically heated)Type III - probe-type total-temp
3、erature sensor (unheated)1.1 Purpose:This standard establishes essential minimum safe performance requirements for total temperature measuring instruments, primarily for use with turbine-powered subsonic transport aircraft, the operation of which may subject the instruments to the environmental cond
4、itions specified in paragraph 3.4 et seq.2. REFERENCES:NACA Report 1235MIL-I-6181SAE 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 suit
5、ability 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, revised, or cancelled. SAE invites your written comments and suggestions. Copy
6、right 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 otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT O
7、RDER: 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.org SAE AS793 Revision A- 2 -3. GENERAL REQUIREMENTS:3.1 Materials and Workmanship:3.1.1 Materials: Materials shall be of a quality which exp
8、erience 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 manufacturing practice.3.2 Identification:The following information shall be legibly and permanently marked on t
9、he instrument or nameplate attached thereto:a. Name of instrumentb. SAE AS793Ac. Manufacturers part numberd. Manufacturers serial number or date of manufacturee. Manufacturers name and/or trademarkf. Rangeg. Rating (Electrical, etc.)h. Explosion categoryi. Aircraft identification3.3 Compatibility of
10、 Components:If components are individually acceptable, but require matching for proper operation, they shall be specified accordingly.3.4 Environmental Conditions:The following conditions have been established as minimum design requirements. Tests shall be conducted as specified in Sections 5, 6, 7
11、and 8 to insure compliance with this standard.3.4.1 Temperature: 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 following exposure to the rang
12、e of temperature shown in column B below.SAE AS793 Revision A- 3 -3.4.2Altitude - When installed in accordance with the instrument manufacturers instructions, the instrument shall function from sea level up to the altitudes and temperatures listed below: Altitude pressure values are per NACA Report
13、1235. The instrument shall not be adversely affected following exposure to extremes in ambient pressure of 50 and 2 in Hg abs, respectively.3.4.3 Vibration: When installed in accordance with the instrument manufacturers instructions, the instrument shall function and shall not be adversely affected
14、when subjected to vibrations of the following characteristics:3.4.4 Humidity: The instrument shall function and shall not be adversely affected following exposure to any relative humidity in the range from 0 to 95% at a temperature of approximately 70 C.TABLE 1Instrument Location A BNonpressurized o
15、r external areas -70 to +150 C -70 to +150 CTABLE 2Instrument Location Altitude TemperatureExternal areas 50,000 ft -2 CTABLE 3Maximum Double MaximumFrequency Amplitude AccelerationInstrument Location (CPS) (Inches) (g)Nacelle, nacelle mounts,wings, empennage andwheel wells 5 - 1000 0.036 10Fuselage
16、Forward of spar areaCenter of spar areaAft of spar area5 - 5005 - 10005 - 500500 - 10000.0360.0360.036-2475SAE AS793 Revision A- 4 -3.5 Explosion Category:The instrument component, when intended for installation either in uninhabited areas of nonpressurized aircraft or in nonpressurized areas of pre
17、ssurized 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, any instrument component which can be an ignition source and is intended for installation in an area in which
18、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 fluid or vapor can occur during normal operation (e.g., fuel tank) the instrument component shall meet the require
19、ments of category II.3.6 Fire Hazard:The instrument shall be so designed to safeguard against hazards to the aircraft in the event of malfunction or failure, and the maximum operating temperature of surfaces of any instrument component contacted by combustible fuel or vapor shall not exceed 200 C du
20、e to self-heating.All material should be noncombustible and shall not liberate gases or fumes which will result in such corrosion as to cause malfunction of equipment or discoloration of dials or indicia, nor shall toxic gases or fumes that are detrimental to performance of the aircraft or health of
21、 personnel be liberated under the operating conditions specified herein.TABLE 4Category Definition RequirementI Explosion proofed: case not designed Paragraph 7.10.1to preclude flame or explosion propaga-tionII Explosion proofed: case designed to Paragraph 7.10.2preclude flame or explosion propaga-t
22、ionIII Hermetically sealed Paragraph 6.2IV Instrument not capable of causing an Shall not be capable ofexplosion producing a spark of morethan 1.0 millijoule ofenergy and shall not have ashort circuit current of morethan 100 milliamperesSAE AS793 Revision A- 5 -3.7 Radio Interference:The instruments
23、 shall not be a source of objectionable interference under operating conditions at any frequencies used on the aircraft, either by radiation conduction, or feedback in any electronic equipment installed in the same aircraft as the instruments in accordance with Specification MIL-I-6181, latest revis
24、ion.4. DETAIL REQUIREMENTS:4.1 Submersion:The instrument shall function and shall not be adversely affected following submersion in water maintained at 18 C (65 F) for a period of 8 hours.4.2 Thermal Response:The thermal time constant shall not exceed 1.5 seconds when subjected to an airflow of Mach
25、 0.3 at sea level. The thermal time constant is defined as the time required to reach 63% of a step function change in temperature.4.3 Static Loading:The instrument shall withstand static impact pressures the equivalent of Mach 1.5 at 10,000 ft or 3512 psf.4.4 Reactance:The resistance shall not vary
26、 more than 0.04 ohm when tested for inductive or capacitive effect over a frequency range of 0 to 2000 cps.4.5 Self-Heating:4.5.1 Temperature Sensing Element: Self-heating shall not change the resistance more than the equivalent of 3 C when tested at 0.3 Mach at standard sea level pressure and tempe
27、rature.4.5.2 Heater Element (Type II only): The resistance of the temperature sensing element shall not change by more than the equivalent of 1 C when the deicing heater element is operated at rated voltage and the probe is in an ambient airflow of Mach 0.3 at sea level conditions.4.6 Power Variatio
28、n:The instrument shall properly function with 15% variation in DC voltage, and/or 10% variation in AC voltage, and 5% variation in frequency.SAE AS793 Revision A- 6 -4.7 Hermetic Sealing:When hermetically sealed, the instrument shall be filled with an inert gas, free of dust particles, and sufficien
29、tly dry so that condensation does not occur during the low temperature tests of this standard.4.8 Electrical Characteristics:4.8.1 Temperature Sensing Element: The resistance versus temperature relationship of the sensing element shall follow the Callendar-Van Dusen equation:where RT = resistance at
30、 temperature in C, Ro = resistance at 0 C, = 0.03925, = 1.45, B = 0 (for temperatures above 0 C) and B = 0.10 (for temperatures below 0 C) and T = temperature in C. Deviations from the Callendar-Van Dusen equation over the temperature range of the instrument shall not be greater than allowed by the
31、following equation:Where T is allowable deviation in C (the negative sign, when T is below 0, shall not be used in this equation).Ro shall be specified by the airframe manufacturer.4.8.2 Heater Element (Type II Only): The nominal heater power consumption shall not be greater than 350 w when the prob
32、e is operating under in-flight icing conditions with a static temperature ranging from -10 to -35 C and an indicated airspeed of from 200 to 350 knots.4.9 Mounting:The mounting method shall be keyed to prevent installation with the wrong orientation.5. TEST CONDITIONS:5.1 Atmospheric Conditions:Unle
33、ss otherwise specified herein, all tests required by this standard shall be made at an atmospheric pressure of approximately 29.92 in Hg, an ambient temperature of approximately 25 C and a relative humidity of not greater than 85%. When tests are conducted with the atmospheric pressure or temperatur
34、e substantially different from these values allowance shall be made for the variation from the specified conditions.RTRo- 1 T ST100- 1 T100- B T100- 1 T100- 3+=T 0.25 0.005T+SAE AS793 Revision A- 7 -5.2 Vibration Equipment:Vibration equipment shall be such as to allow vibration to be applied along e
35、ach of three mutually perpendicular axes of the instrument at frequencies and amplitudes consistent with the requirements of paragraph 3.4.3.5.3 Power Conditions:Unless otherwise specified herein, all tests should be conducted at the power rating recommended by the manufacturer.5.4 Position:Unless o
36、therwise specified herein, all tests shall be conducted with the instrument in its normal operating position.6. INDIVIDUAL PERFORMANCE REQUIREMENTS:All instruments shall be subjected to tests by the instrument manufacturer to demonstrate specific compliance with this standard, including the followin
37、g requirements where applicable.6.1 Dielectric:The instrument shall be completely submerged in water maintained at 18 C (65 F) for a period of 8 hours. Upon completion of the 8-hour period, the instrument shall be removed from the water and dried for a period of one hour. At the end of this time eac
38、h instrument shall be tested by the method of inspection listed in paragraphs 6.1.1 and 6.1.2.6.1.1 Insulation Resistance: The insulation resistance measured at 200 V DC for 5 seconds between all electrical circuits and the metallic case shall not be less than 5 megohms.Insulation measurements shall
39、 not be made to circuits where the potential will appear across elements such as windings, resistors, capacitors, etc., since this measurement is intended only to determine adequacy of insulation.6.1.2 Overpotential Tests: The instruments shall not be damaged by the application of a test potential b
40、etween 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 the maximum circuit voltage, or per paragraph 6.1.2.1 or 6.1.2.2, whichever applies. The potential shall start
41、 from zero and be increased at a uniform rate to its test value. It shall be maintained at this value for 5 seconds, and then reduced at a uniform rate to zero.Since these tests are intended to insure proper electrical isolation of the circuit components in question, these tests shall not be applied
42、 to circuits where the potential will appear across elements such as windings, resistors, capacitors, etc.SAE AS793 Revision A- 8 -6.1.2.1 Hermetically sealed instruments shall be tested at five times the maximum circuit voltage up to a maximum of 200 RMS.6.1.2.2 Circuits that operate at potentials
43、below 15 are not to be subjected to overpotential tests.6.2 Sealing:Hermetically sealed components shall be tested for leaks by means of a mass spectrometer type of helium leak detector or equivalent. The leak rate shall not exceed 0.0434 mu cubic ft/hour*/cubic inch of filling gas at a pressure dif
44、ferential of one atmosphere.*A micron cubic foot per hour leak rate is defined as that gas leakage which would change the pressure of a one cubic foot volume by the amount of one micron (one millionth of a meter of mercury) in one hour.6.3 Calibration:The resistance of the instrument shall be measur
45、ed at 0 and at 100 C. The resistance shall meet the temperature resistance calibration equation of paragraph 4.8.1, within the accuracy specified therein.7. QUALIFICATION TESTS:As many instruments or components deemed necessary by the manufacturer to demonstrate that all instruments will comply with
46、 the requirements of this section shall be tested in accordance with his recommendations.7.1 Calibration:The resistance of the instrument shall be measured at -40, 0, 100, and 150 C. The resistance shall meet the temperature resistance calibration equation of Paragraph 4.8.1 within the accuracy spec
47、ified therein.7.2 Thermal Response:The thermal time constant shall not exceed 1.5 seconds when measured at an airflow of Mach 0.3 at sea level. The thermal time constant is defined as the time required to reach 63% of a step function change in temperature.SAE AS793 Revision A- 9 -7.3 Aerodynamic Cal
48、ibration:The conduction and radiation errors of the instrument shall be determined under dynamic conditions.The instrument shall be subjected to the aerodynamic conditions necessary to produce the conditions specified in Table 5. The errors of the instrument in determination of the stagnation temper
49、ature shall not exceed the values specified in Table 5.7.4 Reactance:The instrument shall be tested for inductive and/or capacitive reactance effect. The resistance of the instrument shall not vary more than 0.04 ohm at any frequency of the measurement from 0 to 2000 cps.7.5 Self-Heating:7.5.1 Temperature Sensing Element: The instrument shall be tested wi
