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This SAE Aerospace Information Report (AIR) was prepared by a panel of the SAE A-5 Committee. This document establishes the specifications for fluids used in landing gear shock struts with extreme pressure and antiwear additives that have been added for improved lubrication. This document requires qualified products.

This SAE Aerospace Recommended Practice (ARP) applies to landing gear structures and mechanisms (excluding wheels, tires, and brakes and other landing gear systems) for all types and models of civil and military aircraft. All axles, wheel forks, links, arms, mechanical and gas/oil shock struts, downlock and uplock assemblies, braces, trunnion beams, and truck beams etc., that sustain loads originating at the ground, and that are not integral parts of the airframe structure, should be designed and validated in accordance with this document. Hydraulic actuators (retraction, main and nose gear steering, positioning, damping, etc.) should also be included in this coverage. System level, non-structural components such as retraction/extension valves, controllers, secondary structure and mechanisms in the airframe (e.g., manual release mechanisms, slaved doors) as well as equipment that is located in the cockpit are not addressed in this ARP.

This SAE Aerospace Recommended Practice (ARP) provides recommendations on cavity design and the installation of elastomer type spare seals in these cavities.

The present document addresses gas and hydraulic fluid servicing required on commercial and military aircraft landing gears, for both single and dual chamber shock struts.

A landing gear system comprises the most compelling assembly of engineering skills. Its importance to the successful design of an aircraft can be favorably compared with that of the aircraft's wings and engines. A landing gear system consists of several different engineering disciplines, and is continually in the public eye especially with regard to safety. The primary objective of AIR4846 is to present a record of a variety of interesting gears, gear/aircraft systems and patents, and to discuss wherever possible the lessons learned, and the reasons for the design. Thus, the document is not only a historical account, but a means of recording technical knowledge for the practical benefit of future landing gear designers. Commendable efforts have been made over the years by several individuals to make such recordings, and AIR4846 will make continual reference to them. This applies to all books, papers, or specifications that have the approval of the SAE A-5 Committee.

This specification contains landing gear strength and rigidity requirements, which, in combination with other applicable specifications, define the structural design, analysis, test, and data requirements for fixed wing piloted airplanes. These requirements include, but are not limited to the following: a General Specifications 1 The shock-absorption characteristics and strength of landing-gear units and the strength and rigidity of their control systems and of their carry-through structures.

This SAE Aerospace Recommended Practice (ARP) applies to fatigue testing of landing gear and landing gear components.

This document defines the criteria used for the selection of landing gear shock strut upper and lower bearings.

This specification contains landing gear strength and rigidity requirements, which, in combination with other applicable specifications, define the structural design, analysis, test, and data requirements for fixed wing piloted airplanes. These requirements include, but are not limited to the following: a General Specifications 1 The shock-absorption characteristics and strength of landing-gear units and the strength and rigidity of their control systems and of their carry-through structures.

This document establishes a procedure for disposition of landing gear components that have been involved in accidents/incidents. The recommendations in this document apply to components made of ferrous and non-ferrous alloys.

Recent field experience has indicated significant problems with some types of wire and cable as routed on aircraft landing gear. This Aerospace Information Report (AIR) is intended to identify environmental concerns the designer must consider, materials that appear to be most suitable for use in these areas, routing, clamping, and other protection techniques that are appropriate in these applications.

This specification covers definition of landing impact tests which are to be conducted on landing gear assemblies including shock absorbers, suggested instrumentation for the tests and required data of the resulting test report. It is intended to standardize impact test procedures on landing gear shock absorbers and to provide sufficient data to allow evaluation of the design with respect to requirements of MIL-L-8552 and MIL-S-8959 as applicable.

This document covers the recommended criteria and performance requirements for the design and installation of an aircraft emergency arresting hook intended for use with emergency runway arresting systems. Design criteria for fully operational hooks and for carrier based aircraft hook installations are contained in specification MIL-A-18717.

This document is intended to give advisory information for the selection of plain bearings and bearing materials most suitable for aircraft landing gear applications. Information included herein was derived from bearing tests and service experience/reports. Airframe/landing gear manufacturers, commercial airlines, the U.S. Air Force and Naval Air Systems Command provided input for the document. Information is given on bearing installation methods and fits that have given satisfactory performance and service life. Base metal corrosion is a major cause of problems in bearing installations for landing gears. Therefore, methods of corrosion prevention are discussed. Effort is directed toward minimizing maintenance and maximizing life expectancy of landing gear bearings. Lubricated and self-lubricating bearings are also discussed. There are wide ranges of bearing load and motion requirements for applications in aircraft landing gears.

This document is intended to give advisory information for the selection of plain bearings and bearing materials most suitable for aircraft landing gear applications. Information is given on bearing installation methods and fits that have given satisfactory performance and service life expectancy. Corrosion is a major cause of problems in bearing installations for landing gears. Therefore, methods of corrosion prevention are outlined. Effort is directed toward minimizing maintenance and maximizing life expectancy of bearing installations. Lubricated and self-lubricating bearings are discussed. There are wide ranges of bearing load and motion requirements for applications in aircraft landing gears. For this reason, it is the responsibility of the designer to select that information which pertains to his particular application. Anti-friction bearings, defined as rolling element bearings generally used in wheel and live axle applications, will not be discussed in this document.

This SAE Aerospace Recommended Practice (ARP) provides recommendations on cavity design and the installation of elastomer type spare seals in these cavities.

This SAE Aerospace Standard (AS) covers an alternate gland design for the installation of scraper/wiper rings in the lower end of landing gear shock struts for the purpose of contaminant exclusion. The defined scraper gland covered by this document, as shown in Table 1, is a variant of AS4716, the accepted gland standard for MS28775, O-ring packing seals. Piston diameters, gland internal diameters, groove sidewall angles and the surface finish are all defined by AS4716, but the gland outer retaining wall diameter is changed. AS4088 is similar to this document, but was developed by SAE A-6 for flight control and general-purpose cylinders. It differs from this document primarily by the clearance between the rod (piston) and outer gland wall. Since landing gears are more susceptible to dirt contamination, the additional clearance provides a larger path to allow excessive dirt accumulation to exit the gland.

A landing gear system comprises the most compelling assembly of engineering skills. Its importance to the successful design of an aircraft can be favorably compared with that of the aircraft's wings and engines. A landing gear system consists of several different engineering disciplines, and is continually in the public eye especially with regard to safety. The primary objective of AIR4846 is to present a record of a variety of interesting gears, gear/aircraft systems and patents, and to discuss wherever possible the lessons learned, and the reasons for the design. Thus, the document is not only a historical account, but a means of recording technical knowledge for the practical benefit of future landing gear designers. Commendable efforts have been made over the years by several individuals to make such recordings, and AIR4846 will make continual reference to them. This applies to all books, papers, or specifications that have the approval of the SAE A-5 Committee.

This document will examine the more important considerations relative to the utilization of "one piece", or integral electronics proximity switches, and "two piece", or separate sensor and electronics proximity switches, for applications on aircraft landing gear. In general, the recommendations included are applicable for other demanding aircraft sensor installations where the environment is equally severe.

This document establishes a procedure for disposition of landing gear components that have been involved in accidents/incidents. The recommendations in this document apply to high heat treat steel components (FTU = 180 ksi and above).