Why Electro-mechanical Actuators are Best for Your Aerospace Application
June 05, 2018Sponsored content
Actuators are devices that convert input energy from an electric, hydraulic or pneumatic source into a linear or rotary motion. They are critical components found in assemblies for virtually all industries, including manufacturing, medical, solar, agriculture, robotics, automotive and aerospace.
Figure 1: Aerospace-qualified electro-mechanical actuators. Source: CEF IndustriesAdvanced electro-mechanical actuators have been steadily replacing hydraulic and pneumatic actuators in demanding aerospace applications, where manufacturers are constantly looking for opportunities to reduce weight and increase component reliability.
Selection Criteria
Design engineers factor in many criteria when selecting the best actuator for an aerospace or military application, including cost, system size and weight, efficiency, control, maintenance and safety.
Cost is always a critical factor to consider when selecting any component. Actuator cost incorporates more than the initial purchase price. Assembly, maintenance and repair costs are considerations as well. Hydraulic and pneumatic actuator systems can be complicated and expensive to install and have higher maintenance and repair costs than electro-mechanical systems.
Reduction of system size and weight is a major reason that aerospace manufacturers are changing from hydraulic to electric actuators. Hydraulic systems are heavy, and replacing them with lighter electro-mechanical actuators allows aircraft to be more fuel-efficient and fly farther per gallon of fuel. Modern jets employ dozens of actuators for a variety of interior and exterior systems, including engine and flight control, landing gear uplock, seat adjustments, door control and canopy actuation. In addition to lower weight, aerospace actuators feature higher power density compared to standard electric actuators. Converting to electric actuators can save hundreds to thousands of pounds in a commercial aircraft.
Electric actuators also have control and efficiency advantages compared to hydraulic actuators. Electric actuators feature very high position, velocity, and acceleration and deceleration control capabilities, while hydraulic actuators have low control performance characteristics. Electric actuators also outperform hydraulic actuators with respect to repeatability, as hydraulic actuators are subject to seal wear, pressure drops or spikes and hydraulic leaks. Electric actuators also run cooler than hydraulic actuator systems.
Safety is paramount in aerospace and military applications where component failure can have life and death consequences. Electric actuators feature higher reliability and lower maintenance, which has a direct correlation to system safety.
CEF Industries
CEF Industries was one of the first companies to manufacture aerospace-qualified electro-mechanical actuators. Since entering the aerospace market in 1948, CEF has manufactured thousands of different configurations for a diverse number of aerospace and defense applications, including:Figure 2: Model 20 linear actuator. Source: CEF Industries
- APU inlet door
- RAM air door
- Utility door
- Landing gear uplock
- Aircraft trim
- Air bypass doors
- Seat adjustment
- Canopy actuation
- Engine control
- Valve control
The Model 20 linear actuator from CEF Industries, a standard product line offering, is an ideal solution for customers with limited funding or development time. All Model 20 actuators are RTCA-DO 160E qualified and are available with a variety of speed, mounting, electrical connection and annunciation options. The Model 20 actuators convert the speed and torque of an electric motor to a linear motion. Standard models are available with strokes up to 5 in., limit or Hall Effect end or travel switches and load capabilities up to 250 lb. A variety of gear ratios and lead screw combinations generate a range of standard performance curves.
Figure 3: Model 20 structural load. Source: CEF Industries
Design features and benefits of all CEF actuators include:
- Operating temperature range: -67° to 167° F (-55° to 71° C); suitable for extreme environmental conditions
- EMI, RFI tested; aerospace qualified
- Solid state (electrical) limit switches; accurate, repeatable extended and retracted positions (with indication)
- Non-jamming mechanical stops; protects system from over-travel
- Optional electrical interfaces and mounting configuration; adaptable to customer installation constraints
- Each unit functionally tested; assured performance
Visit the CEF Industries website to see the complete line of standard Model 20 actuators and specifications, as well as the CEF actuator brochure.
Custom Solutions and Case Studies
If a standard actuator is not suitable for the application, CEF Industries has the expertise and experience to design a custom tailored linear or rotary actuator to meet performance, life and reliability and size requirements. All custom actuators meet the same stringent quality standards and use the same high-quality components as the line of standard actuators.
Custom actuator designs can be tailored to fit limited space requirements or unique environmental conditions. CEF engineers work closely with customers, from the initial concept phase through actuator production. Lead-time for initial functional prototype development is as little as six to 12 weeks. When development is complete, CEF will typically perform any necessary qualifications. In some cases, a custom design can lead to a standard product feature.
Lesson Learned 1
As our Model 20 actuators are among the most power dense, low weight and dependable in the aerospace industry, CEF was puzzled when one of our customers commented on failures one of their customers had experienced in the field. The unit was returned to CEF and something just wasn’t right. We decided to go and visit the end user with the customer to discover what might be causing the failure. During our visit, we observed the end user subjecting our actuators to extreme conditions that were never considered nor tested for. CEF engineering then went to work and came up with a solution to mitigate the unforeseen condition and we now incorporate this same solution in all of our new Model 20 actuators, just in case.
Lesson Learned 2
Being the market leader for auxiliary door actuators in aircraft, CEF has learned many lessons. Chief among these lessons is understanding actual operating performances under power and environmental extremes. CEF has created a proprietary actuator modeling program that takes predicted electrical and mechanical performances and then cross-references these predictions with actual recorded field data. What this enables us to do is to accurately characterize each new design and see if there are any areas of possible weakness. Our success rate with this approach is outstanding and our customers benefit from less design and schedule risk, resulting in more reliable actuators from the start.
Conclusion
Electro-mechanical actuators offer many advantages over hydraulic actuators and should be considered for all aerospace or military applications. Aerospace-qualified actuators from CEF address cost, system size and weight, efficiency, control, maintenance and safety concerns. With nearly five decades of experience producing electro-mechanical aerospace actuators, CEF Industries is uniquely suited to meet end user needs, whether with the standard Model 20 actuator or a custom-tailored solution.
Contact CEF Industries during the concept phase for best results, and a CEF engineer will work with you from initial concept through production of your actuator. Engineers are available to meet with you anywhere in the world.