Boeing and the National Aeronautics and Space Administration have just completed wind tunnel testing of a full-scale 757 vertical tail model equipped with active flow control technology.
One aim of the tests is to show that active flow control can enhance the performance of a vertical tail enough to enable future designers to reduce the size of the structure for a whole family of airplanes. And a smaller tail can help reduce an airplane's drag and weight, which could improve aerodynamic efficiency and fuel efficiency, respectively.
The testing, which began in early September and concluded on Nov. 4, 2013, took place at a 40x80 foot wind tunnel at the NASA Ames Research Center at Moffett Field, Calif.
The wind tunnel tests have enabled the Boeing-NASA team to observe “a wide array of flow control configurations across the whole low-speed flight envelope of the vertical tail,” said Ed Whalen, the Boeing Research & Technology project manager for the testing. The team will pick the most efficient and/or effective flow control configuration for future flight testing “to see how it performs in the real flight environment,” Whalen said.
The flight testing will be aboard the Boeing ecoDemonstrator program 757 flight test aircraft. The ecoDemonstrator program is Boeing’s development and test program that focuses on improving environmental performance by bringing new technologies, materials and methods to implementation faster than ever before.
The combined wind tunnel and flight tests will represent the first full-scale flight demonstration of this active flow control technology, Whalen said. “That will give us insight into how the system works, how effective and efficient it is, things that we’re not completely sure of at this point.”
The flow control on the 757 vertical tail model comes from sweeping jet actuators, which are devices that essentially blow air in a sweeping motion along the span of the tail. As the actuators blow air over the rudder, they help to redirect and reattach the air flow over the rudder that would otherwise be separated at some of the higher rudder angles. Eliminating separation on the rudder benefits performance.
The application of active flow control technology throughout an aircraft system could affect the way future airplanes are designed, Whalen said.
“There might be different wing shapes, you might choose different sweep angles, different aspect ratios of wings, based on the fact that you know what the effect of flow control is ahead of time,” he said. “And you could get an overall more effective and efficient system if you consider active flow control as part of the system rather than as a fix or add-on.”
The test vertical tail itself is an actual 757 vertical tail that came out of an aircraft bone yard in Arizona. With the help of a Boeing Test & Evaluation team, Advanced Technologies Inc. of Newport News, Va., modified and refurbished the tail into a wind tunnel model. The actuators are provided by NASA as part of a collaborative agreement under the NASA Environmentally Responsible Aviation program.
To watch a short NASA video about this wind tunnel test, click here and scroll down the page.