1333. Lightweight Hydraulic System Development and Flight Test

Paper

Abstract

This paper discusses the development of aircraft lightweight hydraulic systems which utilize high operating pressure, 8000 psi, as compared to today’s 3000 psi systems. The concept of utilizing higher operating pressures for aircraft hydraulic system provides for significant reductions in both weight and volume. The power level of hydraulic systems in military aircraft has risen from less than 10 horsepower in the early 1940s to nearly 300 on the Navy’s modern F-14 fighter, 500 on the SST Concorde, and 1000 on the Air Force’s B-1 bomber. With considerable theoretical and empirical data available, a selection of 8000 psi was determined to be the best practical level to operate an aircraft hydraulic system. This pressure level was applied to the Navy’s F-14 and it was theoretically determined that 30 percent of the weight and 40 percent of the volume of the F-14 hydraulic system could be reduced. In order to verify the overall concept, a short flight test program was conducted in the Rockwell/Navy T-2C basic trainer aircraft.
The development of aircraft Lightweight Hydraulic Systems (LHS) has been an ongoing Navy R&D program since 1965 and is being funded by the Naval Air Development Center (NADC) at Warminster, Pennsylvania. This system employs an operating pressure of 8000 psi as compared to today’s 3000 psi and provides significant reductions in both weight and volume. The 3000 psi pressure level was established in the late 1930s. Two major areas that provide the impetus to operate at this level were the elastomeric O-ring seal and the advent of a reliable variable displacement pump. No significant change in the operating pressure level has been made since that time. However, the Navy and Rockwell International have recognized that considerable advances in the state-of-the-art have been made and higher operating pressures are now feasible. This paper describes these developments.