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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 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

Information on Hard Landings

2018-02-27
WIP
AIR5938A

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.

Standard

Tail Bumpers for Piloted Aircraft

2017-07-14
CURRENT
ARP1107C
This recommended practice covers the fixed structure, or independent energy absorbing system affixed to the airframe to afford protection to the control surfaces, engine and other portions during ground handling, take-off and landing.
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 Fatigue Spectrum Development For Part 25 Aircraft

2014-06-10
CURRENT
AIR5914
This SAE Aerospace Information Report (AIR) provides guidelines for the development of landing gear fatigue spectra for the purpose of designing and certification testing of Part 25 landing gear. Many of the recommendations herein are generalizations based on data obtained from a wide range of landing gears. The aircraft manufacturer or the landing gear supplier is encouraged to use data more specific to their particular undercarriage whenever possible.
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

Tests, Impact, Shock Absorber Landing Gear, Aircraft

2012-10-03
CURRENT
AS6053A
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.
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

Landing Gear Structural Health Monitoring

2012-04-12
HISTORICAL
AIR6168
This SAE Aerospace Information Report (AIR) discusses past and present approaches for monitoring the landing gear structure and shock absorber, methods for transient overload detection, techniques for measuring the forces seen by the landing gear structure, and methods for determining the fatigue state of the landing gear structure. This AIR covers the landing gear structure and shock absorber. It does not include the landing gear systems or landing gear wheels, tires and brakes. Landing gear tire condition and pressure monitoring are detailed in AIR4830 and ARP6137, respectively.
Standard

Information on Hard Landings

2011-01-03
CURRENT
AIR5938
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.
Standard

Crashworthy Landing Gear Design

2010-05-04
CURRENT
AIR4566A
The intent of this SAE Aerospace Information Report (AIR) is to document the design requirements and approaches for the crashworthy design of aircraft landing gear. This document covers the field of commercial and military airplanes and helicopters. This summary of crashworthy landing gear design requirements and approaches may be used as a reference for future aircraft.
Standard

Landing Gear Structures and Mechanisms

2009-02-04
HISTORICAL
ARP1311C
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

Landing Gear Retraction / Extension Systems

2008-05-14
WIP
ARP5569
This Aerospace Recommended Practice (ARP) will cover normal and emergency landing gear retraction/extension systems. This includes all equipment necessary for the control and sensing of the components used for raising and lowering the gear, up-locking and down-locking the gear, opening and closing the associated landing gear doors, and any latching of this equipment. The document will provide recommended practices for the use of conventional technologies and for those newer technologies now coming into use. It will include the regulatory and other safety requirements for these systems together with recommendations for; sequencing and timing, sensor selection, and failure monitoring of both normal and emergency operation and the support of maintenance and test needs.
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