This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
Future Airplane Hydraulic Distribution System Design Developments and Testing Criteria
Annotation ability available
Sector:
Language:
English
Abstract
The latest tubing, fitting, and flexible line designs as well as the testing techniques presently used on production airplane hydraulic distribution systems are reviewed in this paper. Designs and materials that are being considered for future airplanes as well as their advantages are presented here in terms of weight and cost. Other major trade parameters such as reliability and maintainability are also considered along with the most significant of all distribution system areas requiring improvement-the installation criteria and techniques.
Advanced tensile, impulse, and flexure testing techniques are evaluated and compared with actual airplane combined load environments encountered by hydraulic systems on large jet aircraft.
Based on extensive analyses, an advanced all-welded approach and a conventional distribution system were fabricated and combined environment tested, as individual systems, to the most severe flight environments for the life of the airplane on an accelerated basis. Results of the system test program and separate tests conducted per Military specification are reviewed in detail. Noted are the vast differences between the combined stress levels measured using the two testing techniques. Maximum combined stress levels measured in the simulated airplane systems only reached one-third of those actually required if the systems were tested per Military specification.
Investigation showed that installation practices tended to explain why excessive stresses and/or wear conditions caused tube failures in service in spite of the fact that the connections had already passed Military specification requirements. Whether or not the resultant installation build-in stress levels were excessive only tends to point out the limited applicability of the present specification techniques; and gives another reason to establish a new basis for tubing and fitting testing. An evaluation of hydraulic impulse surges by computer and test verification in Boeing aircraft was conducted. A revised impulse wave form is considered as a recommended standard for impulse testing of tubing and fittings.
New criteria are recommended for both the installation and the testing of hydraulic tubing systems. Advanced installation techniques are suggested as a means to circumvent most of the service failures once the tube connectors have passed the advanced testing methods.
Recommended Content
Technical Paper | Permissible Defects in Hydraulic Tubing |
Technical Paper | Background for Impulse Testing of Hydraulic Medium and High Pressure Components |
Aerospace Standard | FLANGE PROFILES, V-COUPLING, DESIGN STANDARD |
Authors
Topic
Citation
Mutzke, R., Nelson, W., and van der Velden, H., "Future Airplane Hydraulic Distribution System Design Developments and Testing Criteria," SAE Technical Paper 700789, 1970, https://doi.org/10.4271/700789.Also In
References
- MIL-T-7081 Tube, Aluminum Alloy, Seamless, Round, Drawn, 6061, Aircraft Hydraulic Quality
- MIL-T-6845 Tubing, Steel, CRES (304) Aerospace Hydraulic, 1/8 Hard Hydraulic Condition
- BMS 7-185 Hydraulic Tubing, Corrosion Resistant (21-6-9)
- STMO8-600 Tubing, Steel, Heat, and Corrosion Resistant (AM 350), Hydraulic Cold Reduced and Tempered (CRT) Condition Lockheed Georgia Co.
- BMS 7-203A Titanium 3AL-2.5V Seamless Tubing for Hydraulic Systems
- MIL-H-5440, Hydraulic Systems, Aircraft, Types I and II, Design, Installation, and Data Requirements for
- “Coiled Tubing,” SAE New York, N. Y.
- Chmura Joseph et. al “Coiled Stainless Steel Tubing,” The Martin Co. WADC Tech. Report 57-507 Dec. 1957
- Rodabaugh E. C. et. al “Development of Mechanical AFRPL Threaded Fittings for Rocket Fluid Systems.” Air Force Rocket Propulsion Lab., Edwards Air Force Base Calif. Nov. 1965
- Proceedings of the Conference on Design of Leak Tight Separable Fluid Connectors Marshall George C. Space Flight Center Huntsville, Ala. Mar. 1964
- Helsley, C. W. Jr. “Titanium 6AL-4V Hydraulic Plumbing for Advanced Aerospace Vehicles.” North American Rockwell Corp., Los Angeles Div. May 1969
- Rothi R. “The DCIO and its Hydraulic System.” Vickers Aerospace Fluid Power Conference 1968
- A. Nemeche, K Lebold J. “The Hydraulic Power Distribution System-Lockheed L-1011,” Lockheed California Co. Aerospace Fluid Power Conference 1968
- “Impulse Test Equipment for Testing Hydraulic System Components.” SAE New York, N. Y.
- MIL-F-18280, Fittings Flareless Tube Fluid Connection
- “Flexure Testing of Hydraulic Tubing Joints” (Proposed) SAE New York, N. Y.