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Safran Landing Systems is a global leader in the design, development, manufacture and support of landing gear systems. The company, which is part of SAFRAN S.A., employs 7,000 people across 17 locations and seven countries, and also provides aircraft systems equipment and maintenance, repair and overhaul (MRO) services.
To save weight on the A380 superjumbo aircraft, Safran Landing Systems used Simcenter Amesim™ software and the software’s landing gear design capabilities to design an innovative, decentralized hydraulic generation system with lightweight micro-pumps that delivers power locally to emergency braking and landing gear steering systems.
Size definitely matters, especially when you’re developing the world’s largest passenger jet. With an overall length of 73 meters (m) and a wingspan of nearly 80 m, the Airbus A380 provides seating for 525 passengers and has a range of 15,200 kilometers (km) or more than 9,400 miles, which is sufficient to fly nonstop from New York to Hong Kong. To gain maximum fuel efficiency and payload capacity, weight savings was a must when developing this massive plane. Composites and other lightweight materials account for more than 25 percent of its structure, and engineers scrutinized every aspect of the aircraft to further trim its weight.
Of particular interest were heavy hydraulic lines running the length of the aircraft, from large centralized pumps to equipment such as brakes, landing gears and the nose wheel steering system. Ordinarily, large commercial jets have three sets of redundant hydraulics: two primary circuits and a third backup for safety, all adding up to a big load of hefty piping.
To reduce this bulk, the all-hydraulic backup circuit was replaced with a decentralized fluid-power generation system on the A380. Signals from electronic control units (ECUs) activate small multiple electrically-driven micro-pumps, each located close to the system to be controlled. The micro-pumps provide 5,000 pounds per square inch (psi) or 345 bar of local hydraulic pressure over short runs of small-diameter lightweight piping for braking and steering, so it’s always available in an emergency.
This local electrical hydraulic generation system (LEHGS), the first in a commercial airliner, was developed by Safran Landing Systems, a subsidiary of the SAFRAN Group and a global leader in aircraft landing and steering systems. An Airbus partner for over 30 years, the company’s customers include 250 airlines, 20 military air forces and major global aircraft manufacturers.
In working to optimize system performance, the engineering team faced major challenges in integrating and sizing the large number of different physical parts, assemblies and subsystems for the mechanical, electrical and hydraulic systems. Moreover, they needed to assess any risk factors, such as electrical overheating.
Compounding the difficulty, demanding deadlines and budgetary constraints prohibited numerous time-consuming and costly physical tests of system mockups. Instead, work in designing and optimizing the performance of this first-ever system would have to be done early in the plane’s development, before any hardware was built and at the same time the design of other aircraft systems was underway. That was a tall order that not many tier one suppliers in the aircraft industry would take on.
Safran Landing Systems met these challenges with the help of Simcenter Amesim software from Siemens Digital Industries Software, which the company had implemented on previous projects for predicting the behavior of complex multi-domain intelligent systems. Engineers began by selecting and piecing together individual components and subsystems from a library of predefined items: hydraulic resistance, hydraulic component design, electromechanical, electric motors and drives, thermal resistance, thermal hydraulics, thermal, hydraulics, and electrical basics.
Unlike conventional system modeling languages that require computer programmers to write software, the overall system model is created graphically using Simcenter Amesim, which prompts engineers to enter parameters where necessary. In this way, the software can be used to create a multi-domain system model from the overall conceptual information of interconnected parts and subsystems without requiring a full 3D geometry representation. This enables engineers to simulate and predict the behavior of intelligent systems long before detailed computer-aided design (CAD) geometry becomes available.
Throughout this process, Safran Landing Systems system engineers took advantage of convenient and cost-effective access to the solution thanks to the system’s flexible licensing arrangement, enabling them to optimize the use of specific modules and libraries while lowering overall system simulation expenses.
The modeling and analysis capabilities of Simcenter Amesim allowed Safran Landing Systems to analyze system hydraulic behavior in terms of performance, stability and robustness. Engineers also used the model to study the thermal characteristics of the hydraulic circuit and evaluate the need for heat exchangers. These results were then used to establish the sizing, output and other product specifications for the entire hydraulic power generation system, including the tank, pump and accumulator.
By using the software’s landing gear design capabilities, engineers were also able to explore a large set of parameters and scenarios. When developing a steering system, for example, various combinations of components and systems (actuators, motors, valves, ECU, etc.) could be compared from specification to validation, thus significantly improving steering system quality.
With these predictive capabilities, Safran Landing Systems was able to simulate the behavior of the electrohydraulic system, validate system power-generating performance and enable engineers to accurately size components early in the development of the A380. This significantly reduced dependency on numerous physical prototypes.
“With Simcenter Amesim, Safran Landing Systems is capable of tuning complex multi-domain systems without performing a large set of tests on the bench,” says Jerome Fraval, a systems modeling lead engineer at Safran Landing Systems.
“Simulation enabled us to anticipate and reduce the inherent development risks of a new technology by incorporating an upstream validation regarding the technical choices,” says Fraval. “Simulation results obtained in the early project stages using Simcenter Amesim were later confirmed on test benches with very good accuracy.”
In this manner, the landing gear solution enabled the members of the engineering team to significantly reduce guesswork and freed them to focus on innovation and research and development (R&D).
“Safran Landing Systems was able to predict systems and equipment performances – including critical new technologies – on the entire flight domain,” says Fraval. “The A380 enters into service with its nose wheel steering system control loop only tuned with Simcenter Amesim. Tests were just performed to confirm the good system performance.”