1、_ 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 infringement arising there
2、from, 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 2012 SAE International All rights reserved. No part of this publication m
3、ay 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: +1 724-776-4970 (outside U
4、SA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/AIR6168 AEROSPACE INFORMATION REPORT AIR6168 Issued 2012-04 Landing Gear Structural Health Mo
5、nitoring RATIONALE This SAE Aerospace Information Report (AIR) has been written to provide a review of the state-of-the-art of landing gear structural health monitoring. The document is intended to augment the work of the SAE G-11SHM by extending the airframe structural health monitoring concept to
6、the particulars of the landing gear. The purpose of this AIR is to objectively discuss and summarize historic as well as current state-of-the-art landing gear structural health monitoring technologies. INTRODUCTION The landing gear of an aircraft is a unique assembly. It must bear extreme and varyin
7、g loads when an aircraft maneuvers on the ground, is lifting off or landing, yet it must be lightweight and compact. The landing gear is both a structure and machine. In its simplest form it is a structure with energy absorption capability. However, in its modern incarnation it is a complex machine
8、with controlled articulation, means for steering and braking, multiple axes of energy absorption, and the sole structure supporting the aircraft on the ground. In most applications, landing gears have no structural redundancy. This coupled with the conflicting design requirements of high load carryi
9、ng capacity versus minimum weight and size, results in a landing gear being predominantly manufactured from very high strength (but relatively low toughness) steel, aluminum, and titanium alloys. This is in contrast to most airframes and other aircraft structures, which are typically made from ducti
10、le aluminum alloys that can withstand relatively long cracks that grow over time. The significant difference between the aircraft structure and landing gear is also reflected in the fact that aircraft design and approval methodologies are quite different. For example, many airframe designs use “dama
11、ge tolerant” design methodologies, which assume the presence of cracks in structural members and ensure that, should cracking develop, a safe period of operation is available before the cracks are detected and rectified, whereas currently, due to the design constraints identified above, most landing
12、 gears use “safe life” design methods that do not permit or consider cracks. (Note: Exceptions include the United States Navy carrier based aircraft landing gear that use damage tolerance design methodology and require more than one lifetime for crack growth from initial to critical length.) Therefo
13、re, many of the health monitoring technologies potentially applicable to damage tolerant structure that are based on the development of cracking in the airframe are not applicable to landing gear structures. The landing gear also has movable elements that form part of the structure. These components
14、 must be considered when taking into account monitoring of the entire landing gear structure. The differences between landing gear systems and other aircraft systems mean that often, an alternative approach has to be taken with landing gear structural health monitoring solutions. Historically, landi
15、ng gears have only been fitted with the minimum number of sensors required to indicate the position of the structure or state of articulation. This has been because of the low level of reliability of the sensor system as well as the harsh environment of the landing gear. As aircraft system complexit
16、y has increased and the reliability of the sensor systems have increased, so has the level of sensing on the landing gear. This AIR is based on the article Landing Gear, published in the Encyclopedia of Structural Health Monitoring 1. SAE AIR6168 Page 2 of 16 TABLE OF CONTENTS 1. SCOPE 3 2. APPLICAB
17、LE DOCUMENTS 3 2.1 SAE Publications . 3 2.2 Other Publications . 3 3. LANDING GEAR SHOCK ABSORBER MONITORING . 6 4. CORROSION 7 5. LANDING GEAR TRANSIENT OVERLOAD DETECTION 7 5.1 Dynamic Measurements . 7 5.2 Mechanical Devices 9 5.3 Force Measurements 10 5.3.1 Direct Instrumentation . 10 5.3.1.1 Str
18、ain Gauges . 10 5.3.1.2 Coatings 10 5.3.2 Sensors Using the Landing Gear as a Transducer 11 5.3.3 Capsulated Calibrated Transducer in the Load Path 11 5.3.4 Fluid Pressure in the Shock Absorber 12 6. LANDING GEAR FATIGUE MONITORING 12 6.1 Ask the Material 12 6.2 Sacrificial Component . 13 6.3 Loads
19、Monitoring. 13 6.3.1 Direct Approaches 13 6.3.1.1 Applied Load Comparison . 13 6.3.1.2 Energy Comparison 14 6.3.2 Model-Based Approaches . 14 7. SUMMARY 15 8. NOTES 15 APPENDIX A ABBREVIATIONS . 16 TABLE 1 LIST OF ABBREVIATIONS 16 SAE AIR6168 Page 3 of 16 1. SCOPE This SAE Aerospace Information Repo
20、rt (AIR) discusses past and present approaches for monitoring the landing gear structure and shock absorber, methods for transient overload detection, techniques for measuring the forces seen by the landing gear structure, and methods for determining the fatigue state of the landing gear structure.
21、This AIR covers the landing gear structure and shock absorber. It does not include the landing gear systems or landing gear wheels, tires and brakes. Landing gear tire condition and pressure monitoring are detailed in AIR4830 and ARP6137, respectively. 2. APPLICABLE DOCUMENTS The following publicati
22、ons form a part of this document to the extent specified herein. The latest issue of SAE publications shall apply. The applicable issue of other publications shall be the issue in effect on the date of the purchase order. In the event of conflict between the text of this document and references cite
23、d herein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained. 2.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-73
24、23 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org. AIR4830 Aircraft Tire Pressure Monitoring Systems ARP5908 Landing Gear Servicing AIR5938 Information on Hard Landings ARP6137 Tire Pressure Monitoring Systems (TPMS) for Aircraft 2.2 Other Publications 1. Schmidt, R.K. and Sartor
25、, P. 2009. Landing Gear. Boller, C., Chang, F.K. and Fujino, Y. (Eds). Encyclopedia of Structural Health Monitoring (pp. 1983-1994). United Kingdom: Wiley. 2. “Landing Gear Servicing” SAE ARP5908 Revision A. March 2010. 3. Luce, William E. Aircraft Shock Strut Having a Fluid Level Monitor. Canadian
26、Patent 2 500 458. 8 April 2004. 4. Woodward, Stanley E. A Wireless Fluid-Level Measurement Technique. NASA Technical Memorandum 214320 2006: 34. 5. Allison, S.G. Ultrasonic Measurement of Aircraft Strut Hydraulic Fluid Level. NASA Langley Research Center 02WAC-1931 August 2007. . 6. Seror, Christell
27、e. Method of Measuring the Compression of a Shock Absorber, and an Airplane Undercarriage Constituting an Application Thereof. US Patent 2005/0230200. 20 Oct. 2005. 7. Monitoring Systems, OPMS. Messier-Bugatti, SAFRAN Group. 6 Sep 2007 . 8. Zahm, A.F. Development of an Airplane Shock Recorder. Journ
28、al of the Franklin Institute 1919 88 2: 237-244. 9. Brevoort, M. Landing-Shock Recorder. National Advisory Committee for Aeronautics Technical Note NACA-TN-501 1934. 10. Finance, Robert. Detecting Hard Landings of Aircraft. UK Patent 2 014 731. 30 Aug. 1979. SAE AIR6168 Page 4 of 16 11. “Information
29、 on Hard Landings.” SAE AIR5938. January 2011. 12. Schmidt, Kyle R. System and Method for Determining Aircraft Hard Landing Events from Inertial and Aircraft Reference Frame Data. International Patent WO 2006/130984. 14 December 2006. 13. Yamada, Masamichi and Kawakami, Yoshifumi. “Landing Gear MEMS
30、 Health Monitoring Platform.” Sumitomo Precision Products Co., Ltd. SAE A-5 Aerospace Landing Gear Systems Conference. Toulouse, France. April 2008. 14. Balazinski, M., Beaton, H., Klim, Z.H. and Peloquin, F. “Hard Landing Indication System.” 22nd International Congress Condition Monitoring and Diag
31、nostic Engineering Management (COMADEM), San Sebastian, Spain, 9-11 June 2009. 15. Woodward, Stanley E., Coffey, Neil C, Gonzalez, Guillermo A., Taylor, B. Douglas, Brett, Rube R., Woodman, Keith L., Weathered, Brenton W. and Rollins, Courtney H. Development and Flight Testing of an Adaptable Vehicl
32、e Health Monitoring Architecture. Journal of Aircraft 2004 41 3: 531-539. 16. Reed, Steve. “Indirect Aircraft Structural Monitoring Using Artificial Neural Networks.” PhD Thesis. Dynamics Research Group, Mechanical Engineering Department, University of Sheffield. June 2006. 17. Reed S C, The Use of
33、Artificial Neural Networks in Aircraft Fatigue Monitoring - Prediction of Undercarriage Strains, QinetiQ/FST/CR041003, February 2004. 18. Messier-Dowty. Shear Pin. UK Patent Application Number 0718296.7. 19 September 2007. 19. Messier-Dowty. Overload Detection. UK Patent Application 0718297.5. 19 Se
34、ptember 2007. 20. Theisen, Jerome G. and Edge, Philip M. An Evaluation of an Accelerometer Method for Obtaining Landing-Gear Loads. NACA Technical Report 3247 1954. 21. Hall, Albert W., Sawyer, Richard H. and McKay, James M. Study of Ground-Reaction Forces Measured During Landing Impacts of a Large
35、Airplane. NACA Technical Report 4247 1958. 22. Cowan, Samuel J., Cox, Ronald L., Slusher, Harry W. and Jinadasa, Sunil. Airplane Hard Landing Indication System. US Patent 6,676,075. 13 Jan. 2004. 23. Kehlenbeck, U., Vengrinovich, V., Denkevich, Y. and Tsukerman, V. Onboard Aircraft Weighing System U
36、sing Barkhausen Noise Sensors. 7th European Conference on Non-Destructive Testing, Copenhagen, 26-29 May 1998. 24. Avallone, Eugene and Baumeister, Theodore. “Marks Standard Handbook for Mechanical Engineers.” 9th Edition. New York: McGraw-Hill Book Company, 1978. 25. Fuji Film Prescale Pressure Mea
37、surement Film. Fuji Film. 11 August 2008. 26. Schmidt, Robert Kyle and El-Samid, Nadar Abu. Structural Deflection and Load Measuring Device. International Patent WO 2006/024146. 8 March 2006. 27. Kadlec, Charles. Aircraft Weight Measurements. US Patent 3,426,586. 11 Feb. 1969. 28. Harris, Carl L., R
38、ama, Leighton C. and Soward, Dallas V. Aircraft Hard Landing Indicator. US Patent 3,712,122. 23 Jan. 1973. 29. Kehlenbeck, Ulf. Airbus A340 Weight and Balance System. 58th Annual Conference of Society of Allied Weight Engineers, San Jose, California, 24-26 May 1999. SAE AIR6168 Page 5 of 16 30. Nels
39、on, Harold K., Kleingartner, Charles A. and Vetsch, LeRoy E. Strain/Deflection Sensitive Variable Reluctance Transducer Assembly. US Patent 4,269,070. 26 May 1981. 31. Patzig, Hans-Norbert and Schult, Klaus. Arrangement of Sensors on the Landing Gear of an Aircraft for Measuring the Weight and Posit
40、ion of Center of Gravity of the Aircraft. US Patent 5,257,756. 2 Nov. 1993. 32. Patzig, Hans. Method for Calibrating Sensors Arranged in Pairs on Loaded Structural Parts. US Patent 5,239,137. 24 Aug. 1993. 33. Giazotto, Alessandro Riccardo Britannico. Optically Measuring the Dispacing sic or Load fo
41、r an Aircraft Component, Landing Gear, Braking Control. US Patent 2007/0006662. 11 Jan. 2007. 34. Schmidt, Robert Kyle. Monitoring Parameters in Structural Members. UK Patent 2 387 912. 29 Oct. 2003. 35. Dellac, Stephane and Lafaye, Emmanuel. Force-Measurement Cell and a Connection Pin Fitted With S
42、uch A Cell. US Patent 2006/0266561. 30 Nov. 2006. 36. Segerdahl, Roy R. and Greene, Sandford I. Method for Reducing Frictional Error in Determining the Weight of an Object Supported by a Pneumatic or Hydraulic Device. U.S. Patent 3,581,836. 1 June 1971. 37. Lindberg, George R. and Thomas, Harold O.
43、On-Board Aircraft Weighing and Center of Gravity Determining Apparatus and Method. US Patent 5,521,827. 28 May 1996. 38. Nance, Kirk. Aircraft Weight and Center of Gravity Indicator. US Patent 5,548,517. 20 Aug. 1996. 39. Nance, Kirk. Method of Determining Status of Aircraft Landing Gear. US Patent
44、6,293,141. 1 Sept. 2001 40. Elfenbein, Jack Asher and Mueller, Manfred, Carl. Aircraft Weight and Center of Gravity Computer. U.S. Patent No. 3,513,300. 19 May 1970. 41. Yates, Michael Stuart and Keen, Phillip. Landing Load Monitor for Aircraft Landing Gear. International Patent WO 2007/023280. 1 Ma
45、rch 2007. 42. Zhi, Zhou, Duan, Zhongdong, Jia, Zhonghui and Ou, Jinping. New Kind of Structural Fatigue Life Prediction Smart Sensor. Proceedings - SPIE the International Society for Optical Engineering 5384 (2004): 8. 43. Harting, Darrell R. The S-N Fatigue Life Gage: A Direct Means of Measuring Cu
46、mulative Fatigue Damage. Experimental Mechanics 1966 6: 19-24. 44. Oudovikine, Alex. Sensing Method Predicts the Fatigue Life of Materials. ISG Preventative Technology Inc. 17 Aug 2007. . 45. Delest, Thierry, Regis, Olivier and Schuster, Patrick. Method and Device for Detecting that the Design Loads
47、 of an Aircraft Have Been Exceeded. US Patent 5,511,430. 30 April 1996. SAE AIR6168 Page 6 of 16 3. LANDING GEAR SHOCK ABSORBER MONITORING The movable portions of the landing gear demand the most care and maintenance, and as such have lent themselves to the introduction of monitoring systems earlier
48、 than the purely structural portions. Shock absorber servicing indicators, whether as a ground support aid or through the aircraft central maintenance computer, could help to ensure that the shock absorber is performing as designed. Health monitoring of any oleo-pneumatic, single stage shock absorbe
49、r requires knowledge of the nitrogen gas pressure, hydraulic fluid volume, temperature and shock absorber position to determine the status of the landing gear shock absorber. Currently, to ensure that the landing gear is properly serviced, the ground crew measures the shock absorber extension and nitrogen gas pressure and compares the measurements to the servicing chart on the shock absorber or maintenance manual 2. If the extension is
