Dr. Friedrich Karl Straub

Dr. Friedrich Karl StraubTechnical Director/Lichten Award ChairThe Boeing CompanyTelephone: (480)891-6058Fax: (480) 891-7671

Friedrich Straub, Boeing's principal investigator on the project, explains that Smart is "part of a larger program by DARPA to apply smart materials and structures to enhance the effectiveness of a variety of military vehicles.
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"We focused on piezoelectric material because it gave us the bandwidth or frequency response we needed," said Straub.
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"Our tests demonstrated that the active flap system works in full scale, thus confirming it met the requirement," said Straub.
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Straub said that, years ago, engineers tested a system that used the same principle to make significant improvements.

"These successful whirl tower tests demonstrated that the active flap system works in full scale, confirming it meets the requirement," said Friedrich Straub, Boeing principal investigator in Mesa.

Noise also was reduced, said Friedrich Straub, Boeing lead engineer on the project.

The system used an existing five-bladed rotor from an MD 900 Explorer helicopter for the testing.Each 17-footlong blade was modified to include a single flap on its trailing edge and an actuator that moved the flap up and down up to 40 times a second.

"The flap movement modulates the aerodynamic forces, which when done in a systematic way can control vibration and noise and improve aerodynamic performance," Straub said.

A real helicopter would need to be equipped with sensors to measure vibrations in the cabin, feed the information to a controller that would make instantaneous calculations and pass the information to the actuator to control the flaps, he said.

Such a system might increase the initial cost of a helicopter, but maintenance costs would be lower because of the reduction in vibration, he said.

It also would increase a helicopter's productivity and fleet readiness, he said.

According to Boeing principal investigator Friedrich Straub, "The vibration reduction from an operational point of view would lower maintenance costs, extend the life of airframe components and avionics boxes, and improve readiness and availability.
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"That turned out toe be very successful," notes Mr. Straub.
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"There may be some future versions that would have higher authority actuators that would do primary flight control also," observes Mr. Straub.

According to Boeing principal investigator Friedrich Straub, "The vibration reduction from an operational point of view would lower maintenance costs, extend the life of airframe components and avionics boxes, and improve readiness and availability.
...
"That turned out toe be very successful," notes Mr. Straub.
...
"There may be some future versions that would have higher authority actuators that would do primary flight control also," observes Mr. Straub.