NASA Seeks It All: High Lift, Low Drag

posted Mar 20, 2013, 7:10 AM by Larry Nelson

Ideas for how to more seamlessly change the shape of an aircraft wing's edge to achieve

greater aerodynamic performance are on the AHLLE table. Image credit: NASA/Jim Banke



NASA and its industry partners led by Northrop Grumman are working on an Advanced High-Lift Leading-Edge system for laminar flow wings, developing and testing two ideas that might do the job and that could be integrated into future airliner designs flying during the 2030s.

The challenge is to figure out how to design an airplane wing so that it can provide high lift during takeoff and landing, yet still be able to cruise at altitude such that the air is moving absolutely smoothly across the wing – a concept called laminar flow.

Achieving this goal would enable an airplane to fly more efficiently throughout its flight, and that in turn could result in significant fuel savings that reduce both operating costs and noxious engine emissions.

The first idea was to design a wing section already proved to have a shape and surface conducive to laminar flow at cruise, but built with none of the slats that normally would extend from the leading edge to provide high lift during takeoff and landing.

Instead, high-speed air would be blown across the wing's leading edge to artificially generate high lift. The pressurized air would be bled off from the jet engines and piped within the wing to be released through tiny slots near the front of the wing.

As the expelled air passes over the wing it creates extra lift, in place of the slats, through its interaction with the air already moving over the wing resulting from the airplane's forward momentum – a process called active flow control.  Active flow control also is used near the wing's trailing edge, where a simple, hinged flap is made possible instead of using a more mechanically complex, slotted flap often seen on airliners.

The second idea was to take that same wing section with good laminar flow at cruise but this time test a wing capable of seamlessly changing its shape by drooping down its leading edge – in effect, by morphing.  The morphed leading edge of the wing would enable the same high-lift effect that deploying slats would accomplish.

By not using the panels for slats on the front of the wings, the resulting gaps, steps and seams from the retracted slats would disappear and maintain the otherwise smooth wing surface needed for laminar flow.

The result: the wing can change its shape as needed depending on what part of the flight the airplane is in, and never lose the advantages of having high lift at the beginning or end, or the non-turbulent, fuel-efficient flow of air over the wing during cruise.

Both ideas exceeded all expectations and met all the goals for the study, which means the technology is far enough along to be optimistic about its use in the future.  It is envisioned that there will be further studies using a large-scale wind tunnel model of a modern transport wing, incorporating technologies such as the ones studied in this effort and other active flow control concept for seamless, mechanically-simple, high-lift systems.

Jim Banke
NASA Aeronautics Research Mission Directorate

Larry Nelson,
Mar 20, 2013, 7:10 AM