Past, present, and future capabilities of the Transonic Dynamics Tunnel from an aeroelasticity perspective

Stanley R. Cole*Jerry L. Garcia tAeroelasticity BranchNASA Langley Research CenterHampton, VA 23681A17stractThe NASA Langley Transonic Dynamics Tunnel(TDT) has provided a unique capability for aeroelastictesting for forty years. The facility has a rich history ofsignificant contributions to the design of many UnitedStates commercial transports, military aircraft, launchvehicles, and spacecraft. The facility has many featuresthat contribute to its uniqueness for aeroelasticity testing,perhaps the most important feature being the use of aheavy gas test medium to achieve higher test densities.Higher test medium densities substantially improvemodel-building requirements and therefore simplify thefabrication process for building aeroelastically scaledwind tunnel models. Aeroelastic scaling for the heavy gasresults in lower model structural frequencies. Lowermodel frequencies tend to a make aeroelastic testing safer.This paper will describe major developments in thetesting capabilities at the TDT throughout its history, thecurrent status of the facility, and planned additions andimprovements to its capabilities in the near future.IntroductionHistorical _oersgective on aeroelasticitvAlthough this paper is about the NASA LangleyResearch Center's Transonic Dynamics Tunnel (TDT), toa very large extent the TDT is about aeroelasticity. Tothis end, an historical perspective on aeroelasticity isoffered here as a method of introducing the TDT and toshed a great deal of light on the past importance andpotential future contributions of the TDT. Aeroelasticity* TDT Facility Manager, Senior member AIAA.t TDT Data Acquisition System Manager.Copyright (©2000 by the American Institute of Aeronautics andAstronautics, Inc. No copyright is asserted in the United Statesunder Title 17, U.S. Code. The U.S. Government has a royalty-free license to exercise all rights under the copyright claimedherein for Government Purposes. All other rights are reservedby the copyright owner.is a field of aeronautics that deals with the interaction ofvehicle structural components, in terms of elastic andinertial characteristics, and aerodynamic loads thatdevelop over the vehicle in flight. Aeroelasticityencompasses dynamic phenomena such as buffet andflutter and static phenomena such as aileron reversal andwing divergence. Dynamic phenomena are highlyundesirable and can result in catastrophic instability if noteliminated during the design and development process.Aeroelasticity is predominantly thought of in terms ofdetrimental dynamics. However, static phenomena suchas the deformation of an elastic wing under steadyaerodynamic loads are also important considerations invehicle design. Such deformations may or may not becatastrophic. Even if the deformations are notcatastrophic, they can degrade desired lift and dragproperties. The field of aeroelasticity also deals withmethods to prevent instabilities, such as throughaeroelastic tailoring or through active controlmethodologies. For the reader with an interest in learningmore about aeroelasticity, references I-3 are three classictextbooks on the subject.Aeroelastic behavior has been important with respectto many technological advancements for a very long time.Reference 4 briefly describes some early, unusualencounters with aeroelasticity. Two examples of theseearly aeroelastic effects are problems in windmills thatwere empirically solved four centuries ago in Holland andsome 19th century bridges that were torsionally weak andcollapsed from aeroelastic effects. Many other examplesexist of aeroelastic problems in civil engineering;however, the widest attention has been given toaeroelasticity in the field of aeronautics. Virtually fromthe beginning of flight aeroelasticity has played a role inthe design or flight readiness process of new vehicles.One of the earliest examples of conscientious andbeneficial use of aeroelasticity was the Wright Brothers'application of wing warping to take advantage of wingflexibility for the purpose of lateral control of theiraircraft. 5As flight capabilities progressed rapidly in the early20th century, aeroelasticity continued to play an important1American Institute of Aeronautics and Astronautics