Adaptive surfaces would replace stiff structures designed as a compromise among ideal wing shapes for various maneuvers. Eventually vertical tails, ailerons, and stiff structures could be eliminated. These fluctuations knock the machinery out of alignment and cause a lot of down time. A helicopter's maintenance schedule is approximately 15 percent of its time. In the helicopter project, piezoelectric patches on blade surfaces function both as sensors and as actuators, or as generators of counter-force.
Flutter suppression is a particularly important problem.
Recent experiments in NASA wing tunnels with unoptimized smart structure designs have shown a 70 percnt decrease in displacement and a 20 percnt increase in blade speed by utilizing active vibration control concepts. This reduces stress upon crew members involved in increasingly longer duration missions. You can find the continuation of this article in the January-March 2000 issue.