Controlling Buffeting Loads by Rudder and Piezo-Actuation

High performance aircraft, especially those with twin vertical tails, encounter unsteady buffet loads when flying at high angles of attack. These stochastic loads result in significant stresses, which may cause fatigue damage leading to restricted capabilities and availability of the aircraft. An international collaborative research activity among Australia, Canada and the United States, conducted under the auspices of The Technical Cooperation Program (TTCP) contributed resources toward a program that coalesced a broad range of technical knowledge and expertise into a single investigation to demonstrate the enhanced performance and capability of the advanced active Buffet Load Alleviation ( ) control system in preparation for a flight test demonstration. The research team investigated the use of active structural control to alleviate the damaging structural response to these loads by applying advanced directional piezoelectric actuators, the aircraft rudder, switch mode amplifiers, and advanced control strategies on an F/A-18 aircraft empennage. Some results of the full-scale investigation are presented herein

Actively Controlling Buffet-Induced Excitations

High performance aircraft, especially those with twin vertical tails, encounter unsteady buffet loads when flying at high angles of attack. These loads result in significant random stresses, which may cause fatigue damage leading to restricted capabilities and availability of the aircraft. An international collaborative research activity among Australia, Canada and the United States, conducted under the auspices of The Technical Cooperation Program (TTCP) contributed resources toward a program that coalesced a broad range of technical knowledge and expertise into a single investigation to demonstrate the enhanced performance and capability of the advanced active BLA control system in preparation for a flight test demonstration. The research team investigated the use of active structural control to alleviate the damaging structural response to these loads by applying advanced directional piezoelectric actuators, the aircraft rudder, switch mode amplifiers, and advanced control strategies on an F/A-18 aircraft empennage. Some results of the full-scale investigation are presented herein

A preliminary study on passive and active flutter suppression concepts for aeronautical components

The scope of this work is to study computationally both passive and active flutter suppression characteristics of a cantilever cork agglomerate core sandwich with CFRP facings and an aluminum plate, the latter through the application of piezoelectric patches, respectively. Recently, cork agglomerates have been gaining an increasing interest from the aerospace industry due to their good thermal and acoustic insulation capabilities. In addition, cork based materials intrinsically have excellent vibration suppression properties, which suggest that the combination of cork with high performance composites (such as CFRPs) may lead to high specific strength materials with improved damping characteristics suitable for flutter prevention. Sandwich specimens were modeled using commercially available software ANSYS® and a demo version of ZAERO® software for the determination of the flutter speed and related frequencies. ANSYS® piezoelectric modeling and transient analysis capabilities were used for the active vibration study. Specimen aspect ratio and thickness were chosen as a function of wind tunnel maximum speed for further experimental tests. Results were compared with conventional CFRP and aluminum plates. It was demonstrated that a cork agglomerate core sandwich with CFRP facings can act as a natural flutter suppresser which allows the reduction of the wing weight for a given flight envelope and that the application of piezoelectric actuators is a valuable aeroelastic control concept. An increase of about 20% in flutter speed was achieved using actuated piezoelectric devices. The main goal remains in investigating higher strain smart materials and control strategies, since these improvements are only possible in small structures.O objectivo deste trabalho é o estudo computacional de soluções de supressão de flutter, passiva e activa, através de uma sandwich com núcleo de aglomerado de cortiça e faces de carbonoepoxy e de uma placa de alumínio, esta última através de actuadores piezoeléctricos, respectivamente. Recentemente, os aglomerados de cortiça têm ganho um interesse crescente por parte da indústria aeronáutica devido às suas propriedades de isolamento térmico e acústico. Além disso, os materiais à base de cortiça têm intrinsecamente excelentes propriedades antivibráticas, o que sugere que a sua combinação com materiais de alto desempenho (como o carbono-epoxy) pode levar a materiais de resistência específica elevada e com características de amortecimento melhoradas, adequados à prevenção do flutter. A sandwich foi modelada usando o software de elementos finitos ANSYS® e uma versão de demonstração do ZAERO® para a determinação da velocidade de flutter e respectiva frequência. Por sua vez, as capacidades de modelação piezoeléctrica e transiente do ANSYS® foram usadas para o estudo do controlo de vibração activa. A razão de aspecto das placas foi escolhida em função da velocidade máxima do túnel de vento, para posteriores testes experimentais. Os resultados foram comparados com placas de alumínio e carbono-epoxy convencionais. Foi demonstrado que a sandwich com núcleo de aglomerado de cortiça pode actuar como um supressor natural de flutter que permite uma redução do peso da estrutura para um dado envelope de voo. No que concerne ao controlo activo, a aplicação de actuadores piezoeléctricos é um conceito de controlo aeroelástico valioso que permitiu, neste estudo, um aumento de 20% na velocidade de flutter. No entanto, o principal objectivo permanece em investigar estratégias de controlo e materiais de características piezoeléctricas com capacidade de induzir maiores extensões a custo de uma menor potência

Aeronautical engineering: A cumulative index to a continuing bibliography (supplement 274)

This publication is a cumulative index to the abstracts contained in supplements 262 through 273 of Aeronautical Engineering: A Continuing Bibliography. The bibliographic series is compiled through the cooperative efforts of the American Institute of Aeronautics and Astronautics (AIAA) and the National Aeronautics and Space Administration (NASA). Seven indexes are included: subject, personal author, corporate source, foreign technology, contract number, report number, and accession number

Aeronautical engineering: A continuing bibliography with indexes (supplement 277)

This bibliography lists 467 reports, articles, and other documents introduced into the NASA scientific and technical information system in Mar. 1992. Subject coverage includes: the engineering and theoretical aspects of design, construction, evaluation, testing, operation, and performance of aircraft (including aircraft engines); and associated aircraft components, equipment, and systems. It also includes research and development in ground support systems, theoretical and applied aspects of aerodynamics, and general fluid dynamics

Aeronautical enginnering: A cumulative index to a continuing bibliography (supplement 312)

This is a cumulative index to the abstracts contained in NASA SP-7037 (301) through NASA SP-7073 (311) of Aeronautical Engineering: A Continuing Bibliography. NASA SP-7037 and its supplements have been compiled by the Center for AeroSpace Information of the National Aeronautics and Space Administration (NASA). This cumulative index includes subject, personal author, corporate source, foreign technology, contract number, report number, and accession number indexes

Aeronautical engineering: A continuing bibliography with indexes (supplement 296)

This bibliography lists 592 reports, articles, and other documents introduced into the NASA scientific and technical information system in Oct. 1993. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Aeronautical engineering: A continuing bibliography with indexes (supplement 289)

This bibliography lists 792 reports, articles, and other documents introduced into the NASA scientific and technical information system in Mar. 1993. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Aeronautical engineering: A continuing bibliography with indexes (supplement 292)

This bibliography lists 675 reports, articles, and other documents recently introduced into the NASA scientific and technical information system database. Subject coverage includes the following: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Aeronautical engineering: A continuing bibliography with indexes (supplement 270)

This bibliography lists 600 reports, articles, and other documents introduced into the NASA scientific and technical information system in September, 1991. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics