The move toward the more electric aircraft and electric actuators addresses a couple of key issues, according to Stan Griffin, director of engineering for Triumph Group’s fluid power and actuation business. “One is that hydraulic actuators leak. Secondly, utilizing electric actuators precludes the need for hydraulic lines, which reduces weight, space and installation costs”.
Griffin reports that as aircraft systems become increasingly electric, many hydraulic actuators are being replaced by electromechanical actuators. “However, we also see centralized hydraulic systems moving toward smaller, electrically powered distributed systems, which power hydraulic actuators that are not easily replaced by electromechanical actuators”, he notes.
“The power density of hydraulic actuators”, he explains, “gives them the ability to create a tremendous amount of force, in a relatively small package, compared to an electromechanical actuator”. “In the meantime, we are looking at mounting a smaller, noncentralized hydraulic system in the landing gear bay to power hydraulic landing gear actuators”, Griffin says.
Heavy Weight, High Power
Werner Buecheler, director of flight controls and actuation systems at Liebherr-Aerospace Lindenberg in Germany, says that while hydraulic actuator systems still play an important role, the market is demanding more electrically activated actuators. Buecheler points out that higher power density requirements, such as those for trailing-edge actuators or leading-edge geared rotary actuators, require new development methods. They include optimized gear geometries, increased requirements with tolerance and enhanced production methods such as additive laser melting to achieve improved hydraulic valve blocks on actuators. Glynn Thomas, chief engineer for commercial actuation at the Moog Aircraft Group, cites recent trends indicating a movement away from conventional hydraulic servo actuation to more electrically driven actuators-based on two system architectures.
Any actuator system weight reductions will likely involve the increased use of composite materials and lighter-weight electric drives, as well as additive manufacturing techniques, says Thomas.
The evolution from hydraulically powered to electrically powered actuators is “at the heart of Curtiss-Wright’s strategy as an electromechanical actuator specialist”, says Oliver Green, director of business development at Curtiss-Wright Actuation Group. He says there is increasing use of smart actuators featuring digital control-either located adjacent to, or as part of, the actuator itself.
“We are also seeing continued and ongoing improvements in motor and power electronics technology that helps to significantly reduce actuator weight”.
While actuator technology advances, engineering challenges remain. Among them, Green cites the use of electromechanical actuators in primary flight controls, due to stringent safety requirements for airliners.
The Switzerland-based company is a major supplier of motors for commercial airliner interior actuation systems and fire-suppression actuators.
Collected and summarized from the source below by Minh Pham https://www.mro-network.com/engineering-design/electromechanical-actuators-advance-hydraulic-still-reigns