This SAE Aerospace Recommended Practice (ARP) sets forth criteria for the selection, inspection, retread and repair of worn civil aircraft tires, and the means to verify that the retreaded tire is suitable for continued service. This document is applicable to both bias ply and radial aircraft tires qualified subsequent to the adoption of this document. ARP4834 is the industry document supporting AC145-4A. This industry standard applies to both tubeless and tube type aircraft tires. For tube type tires, the diffusion performance capability of the assembly is controlled by the inner tube and not the tire. Since this standard defines the minimum performance capabilities of the tire, and not the inner tube, the diffusion performance threshold defined is only applicable to tubeless tires. It is, therefore, necessary to clarify this standard and to address diffusion for tube type tires under 7.1.9 and Section 10.
An aircraft’s interface with the ground—through its wheels, tires, and brakes—is critical to ensure safe and reliable operation, demanding constant technology development. Significant advancements have occurred with almost all civil airliners entering service with radial tires, and with the Boeing 787 having entered service in 2011 with electrically actuated carbon-carbon brakes. This book is divided into three sections: tires, control systems, and brakes, presenting a selection of the most relevant papers published by SAE International on these matters in the past fifteen years. They have been chosen to provide significant interest to those engineers working in the landing gear field. With almost all current large civil aircraft (and many smaller aircraft) opting exclusively for carbon-carbon brakes, a number of papers addressing the challenges of this technology are included. Papers touching on tire behavior and papers discussing brake control strategies are provided. For those looking for more information on aircraft landing gears, brakes, and tires, the SAE A-5 committee (the Aerospace Landing Gear Systems Committee), which meets twice a year, serves as a useful forum for discussion on landing gear issues and development. A current listing of documents produced and maintained by the A-5 committee is included in the appendix.
The aircraft landing gear and its associated systems represent a compelling design challenge: simultaneously a system, a structure, and a machine, it supports the aircraft on the ground, absorbs landing and braking energy, permits maneuvering, and retracts to minimize aircraft drag. Yet, as it is not required during flight, it also represents dead weight and significant effort must be made to minimize its total mass. The Design of Aircraft Landing Gear, written by R. Kyle Schmidt, PE (B.A.Sc. - Mechanical Engineering, M.Sc. - Safety and Aircraft Accident Investigation, Chairman of the SAE A-5 Committee on Aircraft Landing Gear), is designed to guide the reader through the key principles of landing system design and to provide additional references when available. Many problems which must be confronted have already been addressed by others in the past, but the information is not known or shared, leading to the observation that there are few new problems, but many new people. The Design of Aircraft Landing Gear is intended to share much of the existing information and provide avenues for further exploration. The design of an aircraft and its associated systems, including the landing system, involves iterative loops as the impact of each modification to a system or component is evaluated against the whole. It is rare to find that the lightest possible landing gear represents the best solution for the aircraft: the lightest landing gear may require attachment structures which don't exist and which would require significant weight and compromise on the part of the airframe structure design. With those requirements and compromises in mind,The Design of Aircraft Landing Gear starts with the study of airfield compatibility, aircraft stability on the ground, the correct choice of tires, followed by discussion of brakes, wheels, and brake control systems. Various landing gear architectures are investigated together with the details of shock absorber designs. Retraction, kinematics, and mechanisms are studied as well as possible actuation approaches. Detailed information on the various hydraulic and electric services commonly found on aircraft, and system elements such as dressings, lighting, and steering are also reviewed. Detail design points, the process of analysis, and a review of the relevant requirements and regulations round out the book content. The Design of Aircraft Landing Gear is a landmark work in the industry, and a must-read for any engineer interested in updating specific skills and students preparing for an exciting career.
The aircraft landing gear system is relatively unique on board an aircraft—it is both structure and machine, supporting the aircraft on the ground, yet providing functions such as energy absorption during landing, retraction, steering, and braking. Advances in Aircraft Landing Gear is a collection of eleven hand-picked technical papers focusing on the significant advancements that have occurred in this field concerning numeric modeling, electric actuation, and composite materials. Additionally, papers discussing self-powered landing gear and more electrical overall aircraft architectures have been included. The content of Advances in Aircraft Landing Gear is divided into two sections: Analysis and Design Methods; and Electric Actuation, Control, and Taxi. For those looking for more information on aircraft landing gears, the SAE A-5 committee (the Aerospace Landing Gear Systems Committee), which meets twice a year, serves as a useful forum for discussion on landing gear issues and development. A current listing of documents produced and maintained by this committee appears in the appendix.
This SAE Aerospace Information Report (AIR) describes the current process for performing comparative wear testing on aircraft tires in a laboratory environment. This technique is applicable to both radial and bias tires, and is pertinent for all aircraft tire sizes.This AIR describes a technique based upon "wear" energy. In this technique, side wear energy and drag wear energy are computed as the tire is run through a prescribed test program. The specifics that drive the test setup conditions are discussed in Sections 4 through 7. In general, the technique follows this process: A test profile is developed from measured mechanical property data of the tires under study. Each tire is repeatedly run to the test profile until it is worn to the maximum wear limit (MWL). Several tires, typically 5 to 10, of each tire design are tested. Wear energy is computed for each test cycle and then summed to determine total absorbed wear energy. An index is calculated for each tire design. This is accomplished by dividing the total linear inches of wear at the most worn point into the total wear energy. The indexes are then normalized to provide a comparative wear rate.The described technique is not meant to provide an absolute wear rate or wear index because the technique does not produce results that allow the user to say a tire will last for a specific number of landings. However, it does provide a comparative index. It will make a distinction from one tire design to another by indicating a percentage difference in abrasive wear rate under representative operational conditions. The technique has been demonstrated in a number of test programs and is shown to have an extremely high correlation to field data. Supporting data is included in Section 9. This document outlines a specific approach for testing use one particular facility. Revisions to this document are not anticipated and Five-Year Reviews have been determined to be unnecessary by the subcommittee. Therefore, it was agreed to stabilize this document.
