A NORTHROP Grumman-led team has begun work on a two-year "smart"-wing contract from the US Advanced Research Projects Agency (ARPA) to develop and demonstrate lift enhancement and optimal transonic cruise concepts.
A smart wing uses advanced materials and structures to sense changes actively in air speed and pressure, and then alter the shape of the wing to suit the new conditions. "The ultimate dream of all this is to have the wings and control surfaces adapt like a bird's, to manipulate the whole flying surface as a single entity," says Northrop Grumman adaptive-wing programme manager, Dr Jaynath Kudva.
Although the smart-wing idea is not new, the team believes that recent developments in sensor and actuator technology are paving the way for the first practical adaptive wing. The team hopes to gain the aerodynamic benefits seen in Boeing's Mission Adaptive Wing experiments and Rockwell/ NASA's Active Flexible Wing programmes, but without the weight penalties which both incurred through the use of contemporary actuator technology.
"We are hoping that, with in-built integrated sensors and new materials, we will show better benefits," says Kudva. Two different smart wings will be tested, a one-sixth-scale McDonnell Douglas F-18 aerofoil and a full-scale wing section from a Gulfstream II.
In all, three "smart" materials will be evaluated, including Lockheed Martin-developed shape memory alloys, which deform when heated. "The trick is to make them deform partially, rather than to their full extent," says Kudva.
Iowa-based ETREMA Products is working on magnetorestrictive materials which deform under applied magnetic fields. This technology will be applied mainly to the Gulfstream II wing, which will be used for laboratory demonstrations by late 1996.
Another set of smart materials to be tested are piezoelectric, which deform under applied electric currents. This work will be performed principally by the Universities of California and Texas, which are developing "...the slightly risky hybrid actuators", says Kudva.
Work on sizing up the F-18 model has begun, and "...we will begin building the windtunnel models in a couple of months", says Kudva. The first windtunnel tests, at NASA Langley, Virginia, are expected to begin in late April 1996.
Source: Flight International
