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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 SAE Aerospace Information Report (AIR) advises that some of the chemicals being used to disinfect, de-ice, and clean airplanes can cause corrosion and/or degradation of landing gear components. Landing gear equipment includes shock struts, braces, actuators, wheels, brakes, tires, and electrical components. Some of the chemicals that have been recognized as potentially injurious are identified and recommendations for mitigating damage are presented.

Steel alloys, such as AF1410 (AMS 6527, UNS K92571) and AerMet 100 (AMS 6532), have been developed which have improved Fracture Toughness characteristics compared to the current landing gear steel alloy, 300M (AMS 6419 and AMS 6257, MIL-S-8844, UNS K44220). The 300M steel is the most widely used material in current landing gear designs. It has been successfully used in thousands of applications. The use of the 300M material necessitates a safe life design criterion where components are retired after on-fourth to one-sixth the laboratory test life. This criterion was established in part due to the relative low fracture toughness of low-alloy steel in the 260 to 300 ksi strength range. The high fracture tough alloys give comparable strength levels with an increase in fracture toughness and better resistance to stress corrosion cracking. These alloys may make possible the consideration of new procedures for operation, maintenance, and inspection.

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).

Steel alloys, such as AF1410 (AMS 6527, UNS K92571) and AerMet 100 (AMS 6532), have been developed which have improved Fracture Toughness characteristics compared to the current landing gear steel alloy, 300M (AMS 6419 and AMS 6257, MIL-S-8844, UNS K44220). The 300M steel is the most widely used material in current landing gear designs. It has been successfully used in thousands of applications. The use of the 300M material necessitates a safe life design criterion where components are retired after one-fourth to one-sixth the laboratory test life. This criterion was established in part due to the relatively low fracture toughness of low-alloy steel in the 260 to 300 ksi strength range. The high fracture tough alloys give comparable strength levels with an increase in fracture toughness and better resistance to stress corrosion cracking. These alloys may make possible the consideration of new procedures for operation, maintenance, and inspection.

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 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 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.