Edited by: Michael Jermann, Assistant Editor
Hispano-Suiza, a Safran Group company, designs, develops and produces electronic power controllers for airborne applications. The company was contracted by Brazilian aerospace manufacturer Embraer to do all the electrical distribution work, which includes the ram air turbine (RAT), for the Embraer KC-390, a medium-size, twin-engine, jet-powered military transport. The KC-390 is able to perform aerial refueling, transport cargo and troops and receive fuel in-flight. It will be the heaviest aircraft that the company has ever produced, and will be able to transport up to 23 tons of cargo, including wheeled armored vehicles.
Concept image of an Embraer KC-390 performing aerial refueling.
The RAT is a small turbine that is connected to a hydraulic pump or electrical generator that is used as an emergency power source capable of delivering enough electricity to run flight control systems. The RAT is able to generate power from the airstream due to the speed of the aircraft. RATs are common in military aircraft, which must be capable of surviving a sudden and complete loss of power.
The RAT must fit in a very confined space and the occurring loads must stay below the defined limits. By using LMS Virtual.Lab Motion software and LMS Imagine.Lab Amesim software from Siemens PLM Software, Hispano-Suiza was able to fulfill both requirements.
“If we didn’t have LMS Virtual.Lab and LMS Imagine.Lab during the design phase, we wouldn’t have discovered an inadvertent opening in the RAT in flight,” said Julien Guiraud, the Hispano-Suiza mechanics manager for the RAT KC 390 calculation and aircraft integration project. “They helped us discover some physics problems during the deployment that we absolutely didn’t expect.”
Improving physics insight
Hispano-Suiza recognized it needed a new design process that would provide improved physical insight of the model; enhance the validation process when exchanging information with Embraer and the different sub- component suppliers (for example, on damping of the system) and shorten the simulation and model validation phase.
The ram air turbine (RAT) connects to a hydraulic pump or electric generator to provide emergency power to flight control systems.
“When you deploy the RAT, you need to slow it down at very high air speed,” said Guiraud. “To avoid any failure, we created a hydraulic LMS Imagine.Lab model to work in parallel with our supplier to validate the supplier result and to quickly answer any questions from Embraer, knowing that if you change parameters like compressibility of the fluid or temperature variation, the damping performance during deployment will be increased.”
In addition to the damping characteristics, the Hispano-Suiza engineers also gained a lot of insight into the kinematic and dynamic performance of the RAT.
Reducing load cases
The KC-390 engagement provided a number of significant challenges for Hispano-Suiza. The company needed to design the RAT correctly the first time even though it< was the company’s first attempt at developing such equipment. The company also needed to provide Embraer with loads, performance and stress results for a variety of load cases to make sure it met Embraer’s specifications.
This presented a number of potential issues, including running and analyzing an enormous number of loads, the risk of errors and providing suppliers with the relevant load cases. It also meant performing kinematics and dynamics simulations, which required the ability to optimize the model to fit boundary conditions.
“Thanks to the use of a multi-body dynamic model, which includes the flexibility of all the components, we discovered that nonlinear problems were created,” said Guiraud. “As a result, we used the LMS Virtual.Lab Motion to check the stress in specific cases that we wouldn’t have discovered using other analysis packages.”
Realizing clear benefits
There were many challenges to implementing new processes and tools, including finding parts that were too flexible and could have led to the loss of door pretension and dramatic failures during the first flight; adjusting kinematic processes according to peaks of loads during the deployment; and developing a better understanding of the influence of parameters on the design and integration in the aircraft.
By using LMS Virtual.Lab Motion and LMS Imagine.Lab Amesim, Hispano-Suiza reduced the number of load cases to be analyzed by 90% — from 500 to 50 — and cut the time it took to conduct the load cases by 30 to 40%. The LMS solutions also helped Hispano-Suiza improve the reliability of the analysis results, enhance the performance of the RAT and bolster its credibility and communication with Embraer.
Hispano-Suiza plans to use optimization tools with the model to investigate computation fluid dynamics (CFD) links in conjunction with Siemens PLM Software tools and fatigue simulation in order to have the full loop of loads and designs in one model.
Siemens
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