Having successfully completed the development-testing phase, Parker Aerospace’s BACS modulates high-pressure bleed air from the engine, which is used to draw cool ambient air from outside the aircraft as it takes off. Once the outside air pressure is too low to draw in and the bleed air temperatures are cooler, the BACS will transition to use only low-pressure bleed air to pressurize the cabin. At very high altitudes, the BACS will also supplement the low-pressure air with additional high-pressure air as required to meet flow requirements.
The system’s ability to measure and respond to constantly changing variables is what sets it apart. To enable Parker’s controller software to make decisions about which air sources to draw upon in a given flight scenario, special sensors were engineered that measure the mass air flow rate and the temperature of the air.
The Denali’s cabin is based on past Cessna Citation designs and can be formatted to accommodate 11 passengers. (Image source: Textron Aviation)
Another challenge was using electronically actuated valves in a hot environment. To keep heat away from the electronics, the valves use standoffs made of a unique ceramic material to hold the actuators. This ceramic has a thermal conductivity one-third that of titanium, a thermal expansion rate similar to stainless steel, and a tensile strength similar to aluminum and so proved to be an ideal candidate for the standoffs at a lower cost than titanium or mica alternatives.
In addition to its in-house design and manufacturing activities, Parker is working closely with its suppliers to optimize other system components, such as the efficient and reliable high-temperature stepper motor used to drive the flow control valves.
“The Cessna Denali is expanding the envelope in turboprop aircraft design and performance, and Parker’s bleed air control system reflects that commitment to innovation,” says Joe Stilla, pneumatics project engineer, for the Parker Aerospace Fluid Systems Division. “We invested significantly in the up-front design of the system and were able to demonstrate the effectiveness of our solution to Cessna. The Denali program will be a significant piece of business for us, and we believe the win can lead to additional opportunities for Parker.”
The Cessna Denali single engine turboprop aircraft was first announced at EAA AirVenture Oshkosh in 2015. It is currently in development and is expected to fly in late 2018. The Denali will use the GE Aviation Catalyst engine – the first clean-sheet turboprop engine in more than 30 years – which incorporates 3D-printed components, digital full authority digital engine control (FADEC), and advanced multistage turbine blades.
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William Kucinski is content editor at SAE International, Aerospace Products Group in Warrendale, Pa. Previously, he worked as a writer at the NASA Safety Center in Cleveland, Ohio and was responsible for writing the agency’s System Failure Case Studies. His interests include 'literally anything that has to do with space,' past and present military aircraft, and propulsion technology. And also sportscars.
Contact him regarding any article or collaboration ideas by e-mail at firstname.lastname@example.org.
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