NASA Armstrong Flight Research Center, Oct. 12, 2017 by Jelisa Beaty - The Adaptive Compliant Trailing Edge flight test project, or ACTE, is proving that a new flap design can reduce aircraft noise by as much as 30 percent on takeoff and landing.
The second phase of the project, ACTE II, which is expected to continue this fall and conclude at the end of the year, will build on the research and data collected on the flap locked in different positions in flight during the first phase. The second phase, taking place at Armstrong, also will validate the technology at higher speeds and research how the flaps impact aerodynamic forces that could improve fuel efficiency.
The goal of the ACTE flight test project is to investigate the capabilities of shape-changing surfaces and determine if advanced flexible trailing-edge wing flaps can improve aircraft aerodynamic efficiency, enhance fuel economy and reduce airport noise generated during takeoffs and landings.
“ACTE has tremendous potential to increase airframe efficiencies,” said Kevin Weinert, ACTE project manager. “We have tested the flap at six positions to show we can take advantage of lightweight, efficient structures.”
In 2014, engineers replaced the traditional 19-foot aluminum flaps for the ACTE wings on NASA’s Gulfstream-III Subsonic Research Aircraft, or SCRAT. The Air Force Research Laboratory funded the flexible flaps that change shape, bend and are made of composite materials designed by FlexSys Inc.
Traditional flaps, when lowered, create gaps between the forward edge, the sides of the flaps and the wing surface. A flexed wing configuration allows a level of control over how and where the wing responds to wind gusts. This design may significantly reduce a major source of airframe noise – making takeoff and landing quieter.
The first flight series for the ACTE took place in 2014 and 2015 at Armstrong, where relevant data were collected on the different flap settings and their ability to withstand the flight environment. These flaps have the potential to be retrofitted to existing airplane wings as well as incorporated into new airliners. The controls on the experimental surfaces were locked on a specific setting and were restricted to a speed of 0.75 Mach, which is approximately 570 miles per hour.
Initially, flights with ACTE flaps were in a flexed configuration and limited to a maximum speed of 250 knots and 20,000 feet. ACTE II showed the technology was safely demonstrated in flight at speeds similar to commercial airliners at Mach 0.85.
NASA is currently conducting data analyses to gain a better understanding of how these new wing flaps may affect aircraft fuel efficiency. The ACTE II flights will also analyze fuel flow through the engine to achieve accurate drag estimates at varied speeds, altitudes and weights, according to Weinert.
The ACTE project began under the former Environmentally Responsible Aviation project and then, due to promising benefits, was transitioned to the Flight Demonstrations and Capabilities project under the Integrated Systems Research Program in NASA’s Aeronautics Research Mission Directorate.
By: Jelisa Beaty
NASA Armstrong Flight Research Center
Editor: Yvonne Gibbs
Photo Credit: Nasa / Caria Thomas