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The primary focus of this document is to provide information on the impacts hard landings and abnormal load conditions on landing gear and related systems. However, because hard landings potentially affect the entire aircraft, this document also includes information for non-landing gear areas. The document may be considered to be applicable to all types of aircraft. This document does NOT provide recommended practices for hard landing inspections, nor does it provide recommendations on the disposition of damaged equipment. Refer to ARP4915 and ARP5600 for information on dispositions relating to landing gear components or wheels involved in accidents/incidents.

This aerospace information report (AIR) provides historical design information for various aircraft landing gear and actuation/control systems that may be useful in the design of future systems for similar applications. It presents the basic characteristics, hardware descriptions, functional schematics, and discussions of the actuation mechanisms, controls, and alternate release systems. The report is divided into two basic sections: 1 Landing gear actuation system history from 1876 to the present. This section provides an overview and the defining examples that demonstrate the evolution of landing gear actuation systems to the present day. 2 This section of the report provides an in depth review of various aircraft. A summary table of aircraft detail contained within this section is provided in paragraph 4.1. The intent is to add new and old aircraft retraction/extension systems to this AIR as the data becomes available.

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. The recommendations in this document do not apply to components made of non metallic composite materials.

This document outlines the most common repairs used on landing gear components. It is not the intention of this AIR to replace overhaul/component maintenance or technical order manuals, but it can serve as a guide into their preparation. Refer to the applicable component drawings and specifications for surface finish, thickness, and repair processing requirements. This document may also be used as a guide to develop an MRB (Material Review Board) plan. The repairs in this document apply to components made of metallic alloys. These repairs are intended for new manufactured components and overhauled components, including original equipment manufacturer (OEM)/depot and in-service repairs. The extent of repair allowed for new components as opposed to in-service components is left to the cognizant engineering authorities. Reference could be made to this document when justifying repairs on landing gears. For repairs outside the scope of this document, a detailed justification is necessary.

This document defines the criteria used for the selection of landing gear shock strut upper and lower bearings (see Figure 1).

This document provides information on the current practices used by commercial and military operators in regards to hard landings (or overload events designated as hard landings). Since detailed information on inspections would be aircraft specific, this AIR provides only a general framework. Detailed information and procedures are available in the maintenance manuals for specific aircraft. Because hard landings potentially affect the entire aircraft, guidelines are listed here for non-landing gear areas. But, the primary focus of the document is the landing gear and related systems. The document may be considered to be applicable to all types of aircraft. This document does NOT provide recommended practices for hard landing inspections, nor does it provide recommendations on the disposition of damaged equipment. Refer to ARP 4915 and ARP 5600.

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 outlines the most common repairs used on landing gear components. It is not the intention of this AIR to replace Overhaul/Component Maintenance or Technical Order Manuals, but it can serve as a guide into their preparation. This document may also be used as a template to develop an MRB (Material Review Board) plan. The recommendations in this document apply to components made of metallic alloys. These recommendations are intended for new manufactured components as well as for overhauled components. The extent of repair allowed for new components as opposed to in-service components is left to the cognizant engineering authorities. Reference could be made to this document when justifying repairs on landing gears. For repairs outside the scope of this document, a detailed justification is necessary. It must be understood that all the repairs listed in this document are not to be applied without the involvement of the cognizant engineer.

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 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 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 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 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.