Shortly after World War II, as aircraft became more sophisticated and power-assist, flight-control functions became a requirement, hydraulic system operating pressures rose from the 1000 psi level to the 3000 psi level found on most aircraft today. Since then, 4000 psi systems have been developed for the U.S. Air Force XB-70 and B-1 bombers and a number of European aircraft including the tornado multirole combat aircraft and the Concorde supersonic transport. The V-22 Osprey incorporates a 5000 psi hydraulic system. The power levels of military aircraft hydraulic systems have continued to rise. This is primarily due to higher aerodynamic loading, combined with the increased hydraulic functions and operations of each new aircraft. At the same time, aircraft structures and wings have been getting smaller and thinner as mission requirements expand. Thus, internal physical space available for plumbing and components continues to decrease.

Commercial Aircraft Hydraulic Systems: Shanghai Jiao Tong University Press Aerospace Series focuses on the operational principles and design technology of aircraft hydraulic systems, including the hydraulic power supply and actuation system and describing new types of structures and components such as the 2H/2E structure design method and the use of electro hydrostatic actuators (EHAs). Based on the commercial aircraft hydraulic system, this is the first textbook that describes the whole lifecycle of integrated design, analysis, and assessment methods and technologies, enabling readers to tackle challenging high-pressure and high-power hydraulic system problems in university research and industrial contexts. Commercial Aircraft Hydraulic Systems is the latest in a series published by the Shanghai Jiao Tong University Press Aerospace Series that covers the latest advances in research and development in aerospace. Its scope includes theoretical studies, design methods, and real-world implementations and applications. The readership for the series is broad, reflecting the wide range of aerospace interest and application. Titles within the series include Reliability Analysis of Dynamic Systems, Wake Vortex Control, Aeroacoustics: Fundamentals and Applications in Aeropropulsion Systems, Computational Intelligence in Aerospace Engineering, and Unsteady Flow and Aeroelasticity in Turbomachinery. - Presents the first book to describe the interface between the hydraulic system and the flight control system in commercial aircraft - Focuses on the operational principles and design technology of aircraft hydraulic systems, including the hydraulic power supply and actuation system - Includes the most advanced methods and technologies of hydraulic systems - Describes the interaction between hydraulic systems and other disciplines

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.

This book is the first of a series of volumes that cover the topic of aerospace actuators following a systems-based approach. This first volume provides general information on actuators and their reliability, and focuses on hydraulically supplied actuators. Emphasis is put on hydraulic power actuators as a technology that is used extensively for all aircraft, including newer aircraft. Currently, takeovers by major corporations of smaller companies in this field is threatening the expertise of aerospace hydraulics and has inevitably led to a loss of expertise. Further removal of hydraulics teaching in engineering degrees means there is a need to capitalize efforts in this field in order to move it forward as a means of providing safer, greener, cheaper and faster aerospace services. The topics covered in this set of books constitute a significant source of information for individuals and engineers seeking to learn more about aerospace hydraulics.

Tests were conducted at temperatures from - 40 F to + 120 F on two simulated aircraft flight control hydraulic circuits. One of the circuits used an A-7 aileron flight control actuator designed for 3000 psi operating pressure with 3/8 and 1/4 inch diameter tubing. The other circuit used an actuator designed for 8000 psi operation with 1/4 and 3/16 inch diameter tubing. Both actuators were designed for the same frequency response, rate and thrust requirements. MIL-H-83282 fluid was used for all tests. Frequency response and zero load rate tests at varying temperatures on the two circuits established the minimum temperatures at which performance requirements were met. Time versus temperature data from A-7D Category II Tests was used in heat transfer calculations to provide a comparison of warm up times for aircraft systems using 3000 or 8000 psi. Results of all tests and analysis indicate that there is no essential difference in warm up time for systems operating at 3000 or 8000 psi.

The Lightweight Hydraulic System (LHS) Advanced Development Program is a multi-phase investigation of the concept of using an 8000 psi operating pressure level to achieve smaller and lighter weight hydraulic components than those used in aircraft with conventional 3000 psi systems. This report presents the results of Phase II in which a full scale A-7E 8000 psi dual system hydraulic simulator was fabricated and tested. Tests conducted were proof pressure, system integration, baseline, dynamic performance, and 600 hours of endurance cycling. No major technological problems were encountered. Four flight control actuators accumulated over 3,000,000 cycles; one pump accumulated over 1000 hours of operation (Phase I + Phase II). Hydraulic system math models were corroborated by test data. A weight and space analysis update projected 33.1% and 36.3% savings, respectively, over an equivalent 3000 psi system. A study of simulator operating experience indicated a 23% improvement in reliability over a comparable 3000 psi system. An additional 600 hours of simulator endurance cycling are scheduled for completion in FY '86.