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 entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefro
2、m, 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 2003 SAE InternationalAll rights reserved. No part of this publication may be
3、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: 724-776-4970 (outside USA)Fax: 724
4、-776-0790Email: custsvcsae.orgSAE WEB ADDRESS: http:/www.sae.orgAEROSPACE RECOMMENDED PRACTICEARP1821REV.AIssued 1982-09Revised 2001-04Reaffirmed 2003-10Superseding ARP1821Aircraft Ground Flotation Analysis Methods1. SCOPE:This SAE Aerospace Recommended Practice (ARP) includes recommended ground flo
5、tation analysis methods for both paved and unpaved airfields.1.1 Purpose:The purpose of this document is to identify the recommended aircraft ground flotation analysis methods that should be used for aircraft landing gear design.2. REFERENCES:1. AIR1780, Aircraft Flotation Analysis2. Computer Progra
6、m for Concrete Airport Pavement Design, Program PDILB, by Robert G. Packard, Portland Cement Association, 19683. ICAO, Aerodrome Design Manual-Part 3-Pavements-First Edition, 1977:a. Load Classification Number Method (LCN), Section 1.3, Method (LCN), Section 1.3, Method C)b. The Load Classification
7、Group (LCG) Method of Classifying Aerodromes and Aircraft (LCN/LCG), Section 3.3. (U.K. Practice)4. Procedures for Development of CBR Design Curves, by A. Taboza Pereira, Instruction Report S-77-1, U.S. Army Engineer Waterways Experiment Station, June 19775. Recommended Standard Data Format of Trans
8、port Airplane Characteristics, National Aerospace Standards, NAS 3601, Aerospace Industries Association of America, June 19686. Airport Pavement Design and Evaluation, AC 150/5320-6C, Federal Aviation Administration, December 1978Copyright SAE International Provided by IHS under license with SAENot
9、for ResaleNo reproduction or networking permitted without license from IHS-,-SAE ARP1821 Revision A- 2 -2. (Continued):7. Airport Pavement Design for the Boeing 777 Airplane, AC 150/5320-16, Federal Aviation Administration, October 19958. ICAO, Aerodrome Design Manual-Part 3-Pavements-Second Edition
10、-1983:Procedure for Pavements Meant for Heavy Aircraft (ACN-PCN Method) Section 1.19. Aircraft Ground Flotation Analysis Procedures-Paved Airfields, by Dale E. Creech and Donald H. Gray, ASD TR-7043, Aeronautical Systems Division, USAFSC, January 1971 (AD 720273)10. Evaluation of Aircraft Landing Ge
11、ar Ground Flotation Characteristics for Operation from Unsurfaced Fields, by Donald H. Gray and Donald E. Williams, ASD TR-68-34, Aeronautical Systems Division, USAFSC, September 1968 (AD 843585)11. Planning and Design of Roads, Airfields, and Heliports in the Theater of Operations, FM 5-430/AFJMAN
12、32-8013 Vol. 2, Department of the Army and the Air Force, September 199412. Paving, and Surfacing Operations, TM 5-337, Department of the Army, February 196613. Design of Aggregate Surfaced Roads and Airfields, TM 5-822-12, Department of the Army, September 199014. Rigid Pavement Design for Airfield
13、s, MIL-HDBK-1021/4, Department of the Navy, April 198715. Flexible Pavement Design for Airfields, DM-21.3/TM 5-825-2/AFM 88-6, Chap. 2 (Tri-Service) - Department of the Army, Navy, and Air Force, August 19783. AIRCRAFT GROUND FLOTATION:Aircraft ground flotation refers to the ability of an aircraft t
14、o operate on existing airfield pavements and is a process of trade-offs between demands for aircraft landing gears with acceptable ground loading pressure and the desirability for light landing gear weight for efficient flight and mission characteristics. The flotation analysis process can relate to
15、 the setting of landing gear characteristics for contemplated new aircraft designs, or it can relate to limitations of gross weight and tire pressure for existing aircraft mission capability to a particular landing site.Copyright SAE International Provided by IHS under license with SAENot for Resale
16、No reproduction or networking permitted without license from IHS-,-SAE ARP1821 Revision A- 3 -4. RECOMMENDED ANALYSIS METHODS:Flotation requirements involve a combination of gross weight, the distribution of that weight (number of tires) to the supporting pavement, the spacing of tires to limit over
17、lap of load-distribution effects within the supporting pavement or unpaved ground, and the intensity of surface tire loading as represented by the average tire contact pressure (tire load/tire contact area).Results obtained from flotation analyses can vary significantly by the type of analytical met
18、hod used for design of pavements and unpaved operating areas. There is a direct but variable relationship between the character of pavement subgrade and structure, and the air vehicle wheel spacing and to a lesser degree (reduced) tire pressure in avoiding overlap of load distribution effects within
19、 the supporting pavement or unpaved ground. In the past, the diversity of pavement design and evaluation methods applied to flotation analyses has led to confusion. More recently, however, a developing consensus has led to the overall summary of recommended methods presented in Table 1.It is importa
20、nt to realize that results of flotation analyses of low-strength subgrades requiring thick structures for support of loads can be quite different from otherwise identical analyses of good-strength subgrades requiring only relatively thin structures for load support. Thus, the manner in which a parti
21、cular pavement design method evaluates subgrade strength and relates it to load support or flotation will substantially influence quantitative results for a particular aircraft type or contemplated aircraft landing gear designs for a particular landing surface.Where flotation analysis consists of di
22、rect comparisons between aircraft types or between alternative landing gear designs for a new aircraft, the analysis method used has much less significance. In this case a ratio of quantified flotation is involved, and any valid analysis method selected will tend to provide a similar ratio even wher
23、e direct quantities differ between methods.4.1 Paved Airfields:On rigid pavements, flotation analyses for commercial and civil aircraft should be made using the Portland Cement Association (PCA) method, using the PDILB computer program. The Load Classification Number (LCN) and the Load Classificatio
24、n Number/Load Classification Group (LCN/LCG) methods are also used in some instances.FAA Advisory Circulars AC150/5320-6D and AC150/5320-16 and the ACN/PCN methods are also acceptable for flotation analysis. The Port Authority of New York and New Jersey has their own pavement design method. For mili
25、tary aircraft, flotation on rigid pavement is analyzed per ASD-TR-70-43 for USAF and U.S. Army, and per MIL-HDBK-1021/4 for the U.S. Navy. A precaution regarding rigid pavement assessments concerns the common use of both “center load“ and “edge load“ methods for design and evaluation. For comparativ
26、e ground flotation determinations either method should provide useful results, but comparisons where the different methods have been used will not be correct.Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from I
27、HS-,-SAE ARP1821 Revision A- 4 -TABLE 1 - Recommended Flotation Procedures4.1 (Continued):On flexible pavement, flotation analyses for commercial and civil aircraft should be made in accordance with U.S. Army Engineer Waterways Experiment Station Instruction Report S-77-1. The USAF and U.S. Army fle
28、xible pavement methods contained in ASD-TR-70-43 can continue to be used. The U.S. Navy and updated Air Force and Army methods are in the Tri-Service, “Flexible Pavement Design for Airfields,“ manual DM-21.3 (also TM 5-825-2 and AFM 88-6, Chap. 2). The ACN/PCN method may also be used for analysis.Th
29、e Defense Mapping Agency Aerospace Center (DMAAC) continues to utilize LCN/LCG, and additionally reports ACN/PCN data where available.4.2 Unpaved Airfields:The recommended methods for aircraft flotation analyses on unpaved airfields are described in the following paragraphs.Copyright SAE Internation
30、al Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-SAE ARP1821 Revision A- 5 -4.2.1 Bare Soil and Grass-Covered Airfields: The recommended method is described in Report No. ASD-TR-68-34, “Evaluation of Aircraft Landing Gear Groun
31、d Flotation Characteristics for Operation from Unsurfaced Soil Airfields,“ September 1968. As noted in the Introduction to that report, the method may be used to evaluate relative ground flotation performance for aircraft operation; i.e., it does not necessarily calculate the absolute values since t
32、hose values can only be obtained by examining the characteristics of the particular airfield to be used, and are, even then, only applicable for a particular point in time.Grass-covered airfields are considered to be similar to bare soil fields, although, apart from flotation, they may vary with res
33、pect to their non-uniform conditions such as surface roughness, braking coefficients, and rolling resistance. In general, to maximize performance, the grass should be cut short, but the turf and sod root structure should not be disturbed. Analysis is best performed by utilizing Cone Index, Airfield
34、Index, or CBR.4.2.2 Matted/Membrane Airfield Surfacing: Use FM 5-430, “Planning and Design of Roads, Airfields, and Heliports in the Theater of Operations,“ and TM 5-337, “Paving and Surfacing Operations.“ These documents discuss landing mat categories, load capacities, and subgrade strength require
35、ments. They also discuss waterproofing and dust suppression membrane types and capacities.4.2.3 Gravel Airfields: Gravel and bare soil surfaces are analogous in relation to surface strength assessment for flotation and can be analyzed for flotation by ASD-TR-68-34. Gravel, however, consists of a lay
36、er of aggregate over the soil subgrade. As such, the thickness of the gravel layer in relation to the subgrade strength and the spacing of multiple-wheels can become a primary factor in flotation analysis. TM 5-822-12 contains criteria for design of aggregate surfaced airfields.4.2.4 DMAACs LCN: MAA
37、C reports LCN for some unpaved airfields, although the LCN of an unpaved field does not provide a means of quantifying an aircrafts load capacity (passes) on these surfaces. If only LCN is provided for an unpaved field, it is recommended that an equivalent CBR value be used for analysis.5. ACN/PCN S
38、YSTEM:The Aircraft Classification Number/Pavement Classification Number or ACN/PCN System has been developed to provide a single means for reporting the aircraft weight bearing capacities of airfield pavements for use in controlling pavement over-load. The system has been adopted by the Internationa
39、l Civil Aviation Organization (ICAO), and is described in Aerodrome Design Manual Part 3, Pavements, Second Edition 1983, ICAO. As a concurring member nation, the United States also has adopted the ACN/PCN System, and National Aerospace Standard (NAS) 3601 requires use of the ACN/PCN System for repo
40、rting aircraft weight bearing limits for pavements. NAS 3601 also defines the other data to be presented in “Airplane Characteristics for Airport Planning,“ and it is common practice for NAS 3601 to be used for all commercial and civil aircraft.Copyright SAE International Provided by IHS under licen
41、se with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-SAE ARP1821 Revision A- 6 -5. (Continued):Consistent with the developing consensus reflected in Table 1, the ACN/PCN System employs methods of PCA (PDILB) for rigid and S-77-1 for flexible pavements to relate
42、 ACN to gross weight for any specific aircraft configuration. The system, however, also establishes standard pavement parameters for computation and sets four subgrade strength classes, with ACN versus gross weight to be determined for each. To the extent possible, these aspects of the ACN/PCN Syste
43、m should be used for future flotation analyses.Note that for established aircraft type, for which ACN versus gross weight relations already exist, comparative analyses of flotation can be made directly by comparing ACN values or by comparing gross weights at equal ACN values.It is recognized that AC
44、N and S-77-1 computations for flexible pavements do not give realistic results for landing gears with more than 4 wheels (B-777, C-5, C-17, etc.). This problem is being addressed by an ICAO ACN study group and an FAA test facility that is scheduled to be operating in 1998.PREPARED UNDER THE JURISDICTION OFSAE COMMITTEE A-5, AEROSPACE LANDING GEAR SYSTEMSCopyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-
