Active flow control technology passes wind tunnel test

Crews shown installing a full-sized tail from a 757 commercial aircraft in the NFAC (National Full-Scale Aerodynamics Complex). The 757 tail came from an aircraft in a bone yard in Arizona and was modified and refurbished for the tests. (All images: NASA Ames Research Center)

Ames Research Center, Langley Research Center, and Boeing, recently teamed and completed wind tunnel testing over a two-month period of a full-scale Boeing 757 vertical tail model equipped with active flow control technology. The team utilized the U.S. Air Force's Arnold Engineering Development Center's 40- by 80-ft wind tunnel at Ames in Moffett Field, CA

Researchers devised the tests to prove that active flow control can enhance the performance of a vertical tail enough to allow future designers to reduce the size of the structure for a whole family of airplanes. That could reduce the penalties related to the vertical tail that aircraft currently pay in drag and weight.

Active flow control involves the manipulation of a flow field—through the addition of energy—to improve the aerodynamic performance of an aircraft structure. Active flow control can enable the design of simpler, smaller, and more aerodynamically efficient structures that help reduce aircraft weight, drag, and fuel consumption.

According to Project Manager Fay Collier, the series of tests comprise a key component of NASA's Environmentally Responsible Aviation Project (ERAP).

"The maturation of technologies such as active flow control, which will benefit aviation by improving fuel efficiency [while] reducing emissions and noise levels is what NASA's aeronautics research is all about. The promising results of these wind tunnel tests and the following flight demonstration in 2015 undoubtedly will have an impact on future 'green' aircraft designs," said Collier.

The flow control on the 757 vertical tail model comes from sweeping jet actuators, devices that essentially blow air in a sweeping motion along the span of the tail. NASA provided the actuators as part of a collaborative agreement under ERAP. "The tests were successful and the technology is now ready to move forward to benefit the traveling public," said Thomas Edwards, Director of Aeronautics at Ames.

The test vertical tail is an actual 757 vertical tail that came out of an aircraft bone yard in Arizona. With the help of the Boeing test and evaluation team,Advanced Technologies Inc., modified and refurbished the tail into a wind tunnel model.

The wind tunnel tests enabled the Boeing and 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, Boeing Research & Technology Program Manager for the testing. The team will pick the most efficient and effective flow control configuration for future flight testing "to see how it performs in the real flight environment," said Whalen.

Flight testing will be aboard the Boeing ecoDemonstrator program 757 flight test aircraft. Boeing's ecoDemonstrator program focuses on improving environmental performance by bringing new technologies, materials, and methods to implementation quicker than in the past.

The combined wind tunnel and flight tests will represent the first full-scale flight demonstration of this active flow control technology, according to Whalen. "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."