Langley Research Center, Hampton, VA
Conventional high-lift systems allow transport aircraft to safely operate at low speeds for landing and takeoff. These high-lift devices, such as Fowler flaps, are complex, heavy, and have high part counts. Fowler flap mechanisms also protrude externally under the wings, requiring external fairings, which increase cruise drag. Simple-hinged flaps are less complex, and an ideal choice for low-drag cruise efficiency. However, simple-hinged flaps require high flap deflections to achieve lift comparable to Fowler flaps. These flap deflections cause severe adverse pressure gradients, which generate flow separation that is difficult to control. In response to these challenges, NASA developed the High Efficiency Low Power (HELP) active flow control (AFC) system.
Although simple-hinged flaps represent optimal high-lift systems for reducing cruise drag, previous attempts to design flow control systems enabling such technology in transport aircraft have been unsuccessful. This is largely because such systems generally require a tradeoff between (a) the ability to achieve the required lift performance, and (b) possessing sufficiently low pneumatic power to enable feasible aircraft system integration (i.e., avoiding excess weight penalties associated with high pneumatic power).
NASAs HELP AFC system represents a breakthrough in flow separation control technology to efficiently achieve necessary lift performances while requiring low pneumatic power relative to alternative flow control techniques. It uses a unique two-row actuator approach comprised of upstream sweeping jet (SWJ) actuators and downstream discrete jets, which share the same air supply plenum. The upstream (row 1) SWJ actuators provide good spanwise flow-control coverage with relatively mass flow, effectively pre-conditioning the boundary layer such that the downstream (row 2) discrete jets achieve better flow control authority.
The two-row actuator system, working together, produce a total aerodynamic lift greater than the sum of each row acting individually. The result is a system that generates sufficient lift performance for simple-hinged flaps with pneumatic power requirements low enough to enable aircraft integration.
This simple, elegant invention can control flow separation resulting from the high flap deflections required by simple-hinged flap systems making such flaps a viable option for aircraft designers. Aircraft with simple-hinged flap systems will achieve reduced cruise drag, thereby increased fuel efficiency.
NASA is actively seeking licensees to commercialize this technology. Please contact NASA’s Licensing Concierge at This email address is being protected from spambots. You need JavaScript enabled to view it. or call at 202-358-7432 to initiate licensing discussions. Follow this link here for more information.
This article first appeared in the September, 2022 issue of Tech Briefs Magazine.
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Tech Briefs - September 2022 - Vol. 46 No. 9
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