SAE AIR 975A-1996 Maintenance of Pitot- Static Systems of Transport Aircraft《运输类飞机全静压系统的维护》.pdf

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1、 AEROSPACEINFORMATIONREPORTSubmitted for recognition as an American National StandardMAINTENANCE OF PITOT-STATIC SYSTEMS OF TRANSPORT AIRCRAFTSAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. Theuse of this

2、report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is thesole responsibility of the user.”SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelle

3、d. SAE invites your writtencomments and suggestions.Copyright 1996 Society of Automotive Engineers, Inc.All rights reserved. Printed in U.S.A.Land Sea Air and SpaceFor Advancing MobilityThe Engineering SocietyINTERNATIONAL400 Commonwealth Drive, Warrendale, PA 15096-0001Issued 1972-07Revised 1996-09

4、REV.AIR975 A1. SCOPE:In efforts to increase the accuracy and reliability of altimetry, speed measurement and otheraspects of air data, a great deal of attention and money have been expended on new and refinedpressure transducing and computing systems and on the standards by which they are calibrated

5、. So much progress has been made in this that the limiting factor is, or may soon be, the sensingand transmitting in the aircraft of the pressures to be transduced. Until the appearance ofReferences 1-13 and 18 there was little guidance available on the maintenance of pitot and staticsystems. This r

6、eport presents what information is available, suggests limits, and lists the principaloriginal papers on the subject.1.1 Purpose:To set forth in a single document the principles and practices for maintenance of pitot and staticpressure systems of transport aircraft.2. REFERENCES:1. “Pitot-Static Sys

7、tems”; Patton and Bryan, Civil Aeronautics Administration, Airplane andEquipment Engineering Report No. 46, (Undated, circa 1950).2. “The Effect of Flow Disturbances on Airspeed Static Vent Readings”; Dunlap and Lapin,Douglas (internal memo) A250-AERO-243, July 1954.3. “An Investigation of the Effec

8、t of Random Fuselage Wall Irregularities on Flush Static PressurePort Calibrations”; Werner and Teigen, WADC Technical Report 57-365 (AD 130805), April1957.4. “Effects of Some Dimensional Variables on the Calibration Characteristics of Static PressureSources”; Teigen, WADC Technical Report 59-596 (A

9、D 266373), June 1959.SAE AIR975 Revision A- 2 -2. (Continued):5. “Fuselage Skin Irregularities in the Vicinity of Fuselage Static Pressure Ports”; De Leo andHagen, Rosemount Engineering Co., 1961.6. “Effects and Control of Installation Irregularities on Flush Static Systems”; Stratton, DouglasReport

10、 LB 30765, December 1961.7. “Aircraft Skin Contour Measurements Adjacent to Flush Static Ports on Military Transport TypeAircraft”; De Leo, Hagen and Thompson, Rosemount Engineering Co., Technical Report4622B, April 1962.8. “Recommendation on Flush Static Port Maintenance”; Anderson, United Air Line

11、s Report F-829B, August 1963. (Superseded by Refs. 9 and 30)9. “Recommendation on Maintenance of Pitot-Static Systems of Transport Aircraft”; Air TransportAssociation of America, Recommendation 34-10-4, December 1969.10. “Evaluation of Factors Affecting the Calibration Accuracy of Aircraft Static Pr

12、essure Systems”;De Leo et al, (U.S.) Air Force Systems Command, Technical Report SEG-TR-65-35 (AD621678, N66-13623), July 1965.11. “The Effects of Installation Irregularities on Flush Static Systems and the Means of EliminatingThem”; Stratton, Autonetics Publication 554-A-18, Undated.12. “The Influe

13、nce of Pressure System Leakage on Aircraft Static Pressure Measurements”; DeLeo and Hagen, Rosemount Engineering Co. Report 76111, Undated.13. “Relation of Static System Leakage to Altitude Error”; Wheatley, United Air Lines Report F-1096A, Rev. June 1967.14. “Pitot and Static Pressure Systems, Inst

14、allation and Inspection of”; Anonymous, (USAFSpecification) MIL-P-26292, January 1959. (Ref. 9 proposed revision.)15. “Recommendation on Design of Pitot-Static Systems for Transport Aircraft”; Anderson, UnitedAir Lines Report F-1242, May 1970.16. “Recommendation on Design of Pitot/Static Systems for

15、 Transport Aircraft”; Air TransportAssociation of America, June 1970.17. “Design and Installation of Pitot-Static Systems for Transport Aircraft”; Society of AutomotiveEngineers, ARP920, October 1968.18. “Wind-Tunnel Investigation of a Number of Total Pressure Tubes at High Angles of Attack;Subsonic

16、, Transonic and Supersonic Speeds”; Gracey, NACA Report 1303, 1957.SAE AIR975 Revision A- 3 -2. (Continued):19. “Wind Tunnel Test Results of Protruding Static Taps for Pressure Compensation”; Hansen,Douglas (internal memo) A250-AERO-60-29, January, 1960.20. “The Measurement of Pressure Altitude on A

17、ircraft”; Gracey, NACA TN 4127, October 1957.21. “Measurement of Static Pressure on Aircraft”; Gracey, NACA Report 1364, 1958.22. “Flight Calibrations of Fuselage Static Pressure Vent Installations for Three Types ofTransports”; Silsby and Stickle, NASA TN D-1356, May 1962.23. “Flight Calibration of

18、 Aircraft Static Pressure Systems”; De Leo and Hagen, FAA SRDS ReportRD-66-3, (Clearinghouse PB-170-763) (Rosemount Engineering Co. Report 76431) February1966.24. “Douglas Five-Probe Differential Pressure Head Proposal for the ATA Conference, Washington,D.C.”; Price, Douglas Technical Memorandum TM-

19、AERO-F-1785, February 1960.25. “Evaluation of New Methods for Flight Calibration of Aircraft Instrument Systems”; De Leo andHagen, WADC Technical Report 59-295 (Part III) (AD 268780) September 1961.26. “Trailing Cone Reference System”; Watson, (included in) Douglas Report DEV 3674, November1964.27.

20、“Lo-lag Trailing Cone System”; Watson, Douglas Technical Memorandum TM-4099, February1966.28. “Flight Test Procedures for Static Pressure Systems Installed in Subsonic Transport Aircraft”;Society of Automotive Engineers, ARP921, July 1971.29. “Influence of Orifice Geometry on Static Pressure Measure

21、ments”; Rayle, ASME Paper 59-A-234, November 1959.30. “Maintenance of Pitot-Static Systems of Transport Aircraft”; Anderson, United Air Lines ReportF-1119B, October 1967.31. “Bibliography on Altimetry, Static Pressure Measurement and Barometry”; Anderson, United AirLines Report F-780, Rev. 1962.32.

22、“Experimental Evaluation of TRU-42/A Pitot Tube Damage (REC Model 851C)”; Lemmermanand Malin, Rosemount Engineering Company, Report 8673, Undated (c. 1967).33. “Waviness and Mismatch Quality Standards: Static Ports”; Douglas Aircraft DivisionAttachment 1 to DQS C 4.2-3R, May 1968.SAE AIR975 Revision

23、 A- 4 -2. (Continued):34. “Operation, Maintenance and Data Processing Procedures for the DC-8 Trailing Cone Kit”;Douglas Aircraft Division, DR-66, (undated).35. “Specification for Aircraft Static System Flight Test by Trailing Cone Method”; Air TransportAssociation, (Attachment 2 to) Operations Memo

24、randum 66-134, November 1966.36. “DC-8 Airspeed Static Position Error Repeatability”; Mabry and Brumby, Douglas AircraftDivision, Paper 5517, (Undated; c. 1968).37. ICAO Circular 81-AN/68 - Aeroplane Static Pressure System - Uniform Method of Calibration ofPosition Error. (International Civil Aviati

25、on Organization, Montreal, Canada.)38. “Performance Report on Static Air Source on Air Carrier Turbojet Aircraft”; Air TransportAssociation, October 1966.39. “The Influence of Aerodynamic Cleanness of Aircraft Static Port Installations on Static PositionError Repeatability”; Douglas Aircraft Co. Rep

26、ort No. DAC-67485, November 20, 1968.40. “Installation Static Trailing-Cone Calibration System”, DC-8 Service Bulletin No. 34-101,Douglas Aircraft, June 1969.41. “DC-8 Airspeed Static Position Error Repeatability,” Mabry and Brumby, Douglas Paper 5517,Undated (circa 1969).3. BACKGROUND:3.1 All aircr

27、aft are fitted with pitot or pitot-static tubes for the sensing of pitot (or total) pressure. Theaccuracy of a tube may depend in part on its alignment on the airplane and on the condition ofthe tube itself at and near the entry (or nose). Very little information has been available to guidethe opera

28、tor in maintaining tubes. This Aerospace Information Report (AIR) endeavors to provideguidance.3.2 Most transport aircraft now in service or soon to enter service sense static pressure for thealtitude and speed instruments at flush ports mounted in the fuselage skin. It has long beenknown that the r

29、epeatability of the pressure sensing at such ports is largely dependent upon thecontour and smoothness of the surrounding skin; as the requirements for accuracy of altimetryhave become more stringent, this has become a matter of increasing concern.During the course of their service lives, airplanes

30、accumulate damage and minor surfacedeformation, some of which is in the static port area. In most instances, Structure RepairManuals for the various aircraft do not adequately detail the special requirements of these areas,and repairs which would be quite smooth enough in other fuselage areas, may l

31、ead to excessivepressure sensing errors. Comparison of information for various airplanes shows less agreementthan would be expected.SAE AIR975 Revision A- 5 -3.2 (Continued):This AIR endeavors to establish comparatively simple methods of measuring and setting limits onsurface irregularities on exist

32、ing airplanes, and to lend support to the instrument engineer whohas to plead for exceptional sheet metal work and for test flight time.3.3 There is need for more wind-tunnel studies to establish a firmer basis for the kinds of tolerancesthis AIR sets. While the effects of long-wavelength sinusoidal

33、 waviness and protrusion orrecession of port fittings have been well analyzed, the effects of step discontinuities, narrow gaps,and irregular roughness need study.Some types of aircraft now in service have skin in the static port region so thin that it can beexpected to bulge or quilt slightly betwe

34、en supporting members. The amount of this quilting, andits effect, if any, on static pressure sensing should also be the subject of studies.3.4 For recommendations on the design of pitot-static systems of new aircraft, or for the retrofit of oldones, References 10, 15-17 should be consulted.3.5 It i

35、s emphasized that this AIR is tentative, and in some areas intuitive in nature, and that while itoffers guidelines it should in no way be considered binding or mandatory.3.6 The Maintenance and Overhaul Manuals for each type of airplane should contain informationequivalent to this AIR, suitably adap

36、ted for that type of airplane. Where adequate specificinformation is available, it should be given more weight than a general recommendation such asthis one.4. LEAKAGE:4.1 General:4.1.1 Leakage, particularly of cabin air pressure into a pitot or static system is not an unusualoccurrence. Large leaks

37、 are immediately apparent from the behavior of the instruments. Smallleaks, however, may be so minor that their effect may be erroneously ascribed to instrumenttolerances or to static port irregularities, etc. It goes without saying that for routine airplaneoperation, leakage must be held below a ce

38、rtain limit, and that prior to calibration of a pitot-static system leakage should be completely eliminated.4.1.2 Purging and proof-pressure testing, while not part of leak testing should in some circumstancesprecede leak testing.4.1.3 Where Government regulations set more stringent requirements, th

39、ey shall prevail.SAE AIR975 Revision A- 6 -4.2 Tooling:4.2.1 For occasional leak testing, as after replacement of an instrument, the airplanes owninstruments may be used, although it is more convenient to have a test set which need consistonly of a simple airspeed indicator with a hand-pump, a pitot

40、 adapter, a static adapter andappropriate lengths of tubing.4.2.2 Special test sets for calibration checks of pitot-static instruments and system leak tests areavailable in various degrees of elaborateness. Basically they consist of pumps, altimeters,airspeed indicators and regulating and shutoff va

41、lves. In some models a machmeter and/orrate-of-climb indicator may be included; in some, the instruments may be calibrated in pressureterms, rather than in feet and knots.4.2.3 Suitable adapters allowing connection of the test equipment to the airplane system should beavailable. For pitot system tes

42、ts it is preferable to connect the test equipment by an adapterfitted over the tube. For static systems it is preferable that the connections be made at thestatic ports, rather than some other point in the plumbing, as for example a drain, for this wouldleave one point untested after removal of the

43、test equipment. The static port adapter, at leastfor use where the inside of the skin at the static port location is exposed to cabin pressure,should be large enough to include the annular gap between the face of the port fitting and thesurrounding skin so that any leakage path for cabin air pressur

44、e would be detected.It is usual to connect the adapter to the port on one side and to use tape to blank off thecorresponding port on the other side of the airplane. When using this method, somethingshould be placed between the face of the port fitting and the tape to prevent sealing of theorifices b

45、y the tape, so that if there is leakage between the port fitting and the skin it will bedetected as flow into the piping. (A coin of about the same diameter as the fitting might besuitable.)CAUTION: Large pieces of colored tape should be used so as to minimize the possibility oftheir being forgotten

46、.4.3 Purging:At each second airframe overhaul or at three-year intervals (unless the operators inspectionsindicate that a longer interval would be satisfactory), the instruments should be disconnected andthe plumbing blown with dry air or dry nitrogen at a pressure of about 50 psi (3.52 kg/sq cm),un

47、less a lower pressure is recommended by the airframe builder, in the direction from theinstruments towards the ports and drains. Hoses which show signs of deterioration and couldshed bits of lining should be removed beforehand. If there is reason to suspect that there ismuch solid material in the li

48、nes, they should be disconnected from port fittings of the “salt shaker”type so that the material may escape.CAUTION: Failure to disconnect instruments will result in damage to them.It may be necessary to restrain hoses from whipping and to prevent blasts of air from reachingthe disconnected instrum

49、ents.SAE AIR975 Revision A- 7 -4.4 Proof-Pressure Tests:If the necessity is indicated by the operators experience, after major modification, replacement ofseveral sections of plumbing or otherwise at the discretion of the operator, the system should bedisconnected from all instruments, plugged and pressurized with dry air or nitrogen to a pressureof about 100 psi (7.03 kg/sq cm) for 5 minutes, unless a lower pressure is recommended by theairframe builder.4.5 Visual Inspection:4.5.1 At each major airframe overhaul or at two year intervals all pitot and static tubing in vulnerableand a