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Landing Gear Shock Absorption Testing of Civil Aircraft

2019-10-31
WIP
ARP5644A
The intent of this document is to provide recommended practices for conducting shock absorption testing of civil aircraft landing gear equipped with oleo-pneumatic shock absorbers. The primary focus is for Part 25 aircraft, but differences for Part 23, 27, and 29 aircraft are provided where appropriate.
Standard

Gland Design: Nominal 3/8 Inch Cross Section for Compression-Type Seals

2019-06-17
CURRENT
AS4832A
This SAE Aerospace Standard (AS) offers gland details for a 0.364 inch (9.246 mm) cross-section gland (nominal 3/8 inch) with proposed gland lengths for compression-type seals with two backup rings over a range of 7 to 21 inches (178 to 533 mm) in diameter. The dash number system used is similar to AS568A. A 600 series has been chosen as a logical extension of AS568A, and the 625 number has been selected for the initial number, since 300 and 400 series in MIL-G-5514 and AS4716 begin with 325 and 425 sizes. Seal configurations and design are not a part of this document. This gland is for use with compression-type seals including, but not limited to, O-rings, T-rings, D-rings, cap seals, etc.
Standard

Landing Gear Common Repair

2019-04-11
CURRENT
AIR5885A
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.
Standard

External Hydraulic Fluid Leakage Definition for Landing Gear Shock Absorbers

2018-07-25
CURRENT
ARP6408
The purpose of this SAE Aerospace Recommended Practice (ARP) is to provide a practical definition of external hydraulic fluid leakage exhibited by landing gear shock absorbers/struts. The definition will outline normal (acceptable weepage) and excessive leakage (unacceptable leakage) of shock absorbers/struts that is measurable. The definition of leakage is applicable to new gear assemblies, refurbished/remanufactured (overhauled) shock absorbers/struts, leakage of shock absorbers/struts encountered during acceptance flights, newly delivered and in-service aircraft. This ARP is intended to provide guidelines for acceptable leakage of landing gear shock absorbers/struts between the ambient temperatures of -65 °F (-54 °C) and 130 °F (54 °C) and to outline the procedure for measuring such leakage. The specific limits that are applied to any particular aircraft shall be adjusted by the aircraft manufacturer before inclusion in the applicable maintenance manual.
Standard

Landing Gear Servicing

2018-07-03
CURRENT
ARP5908A
The present document addresses gas and hydraulic fluid servicing required on commercial and military aircraft landing gears, for both single and dual chamber (also known as dual stage and two stage) shock struts. This document should be considered as landing gear industry recommended practice but in no way is meant to supersede the shock strut OEM’s published procedures.
Standard

Landing Gear Component Heat Damage

2018-07-02
CURRENT
AIR5913A
The purpose of this report is to outline types of in-service heat damage that have been observed in high strength steel landing gear components, with an emphasis on a particular type that is referred to as “Ladder Cracking” which can develop in landing gear shock struts. The report discusses how ladder cracking can be detected visually and evaluated by non-destructive inspection methods, and how it can be repaired at overhaul with the prior approval of the Original Equipment Manufacturer. This report also describes the use of a bearing material that has resolved this problem without introducing other problems. Examples of other types of service induced heat damage are also discussed.
Standard

Landing Gear Structures and Mechanisms

2018-06-03
CURRENT
ARP1311D
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.
Standard

Plain Bearing Selection for Landing Gear Applications

2018-04-18
CURRENT
AIR1594D
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.
Standard

Design Recommendations for Spare Seals in Landing Gear Shock Struts

2017-06-09
CURRENT
ARP4912C
This SAE Aerospace Recommended Practice (ARP) provides recommendations on cavity design, the installation of elastomer type spare seals in these cavities, and information surrounding elastomer material properties after contact with typical shock absorber hydraulic fluid(s) or grease. This ARP is primarily concerned with the use of spare seals on shock absorbers where only a single dynamic seal is fitted and in contact with the slider/shock absorber piston at any one time. These shock absorbers typically have a spare (dynamic) seal gland located on the outer diameter of the lower seal carrier. This spare seal gland is intended to house a spare elastomer contact seal. Split Polytetrafluoroethylene (PTFE) backup rings can also be installed in the spare seal cavity. During operation, if the fitted dynamic shock absorber standard seal begins to fail/leak, then the aircraft can be jacked up, allowing the lower gland nut of the shock absorber to be dropped down.
Standard

Landing Gear Shock Strut Hydraulic Fluid

2016-05-06
CURRENT
AIR5358A
This document describes fluids used in landing gear shock struts with extreme pressure and antiwear additives that have been added for improved lubrication.
Standard

Guide for Installation of Electrical Wire and Cable on Aircraft Landing Gear

2015-07-04
CURRENT
AIR4004A
Recent field experience has indicated significant problems with some types of wire and cables as routed on aircraft landing gear. This SAE Aerospace Information Report (AIR) is intended to identify environmental concerns the designer should 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. In recent years aircraft certification regulatory agencies introduced new regulations regarding Electrical Wiring Interconnection Systems (EWIS) to further enhance safety of the associated systems and aircraft overall.
Standard

Landing Gear Shock Absorption Testing of Civil Aircraft

2013-04-20
CURRENT
ARP5644
The intent of this document is to provide recommended practices for conducting shock absorption testing of civil aircraft landing gear equipped with oleo-pneumatic shock absorbers. The primary focus is for Part 25 aircraft, but differences for Part 23, 27, and 29 aircraft are provided where appropriate.
Standard

Recommended Actions When Disinfectants, De-icers, and Cleaners Come in Contact with Landing Gear Structure

2012-10-03
CURRENT
AIR5541A
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.
Standard

Landing Gear Structural Requirements as Listed in the MIL-886X Series of Specifications

2012-10-03
CURRENT
AS8860A
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.
Standard

Extraordinary and Special Purpose Landing Gear Systems

2012-10-03
CURRENT
AIR4846A
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.
Standard

Disposition of Landing Gear Components Involved in Accidents/Incidents

2011-10-20
CURRENT
ARP4915B
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.
Standard

Development and Qualification of Composite Landing Gears

2010-10-07
CURRENT
AIR5552
This information report provides general guidance for the design considerations, qualification in endurance, strength and fatigue of landing gear using composite components as principle structural elements. The information discussed herein includes the development and evaluation of design data considering: the potential for imbedded manufacturing defects, manufacturing process variations, the component operating environment, potential damage threats in service, rework and overhaul, and inspection processes. This AIR mainly discusses the use of thick composites for landing gear structural components. Considerations and recommendations provided in this AIR may therefore differ greatly from considerations and recommendations found in widely accepted composite design references such as CMH-17 and Advisory Circulars such as AC 20-107(B).
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