NAG-I-2217

MULTIDISCIPLINARY DESIGN INVESTIGATIONOF TRUSS-BRACED WING AIRCRAFT: PHASE 4

Final Report

April 2000

OCE N

Principal Investigators:

B. Grossman, R. K. Kapania,

W. H. Mason and J. A. Schetz

Department of Aerospace and Ocean EngineeringVirginia Polytechnic Institute and State UniversityBlacksburg, VA 24061

Virginia Tech

https://ntrs.nasa.gov/search.jsp?R=20000032960 2018-07-04T03:38:53+00:00Z

MULTIDISCIPLINARY DESIGN INVESTIGATION

OF TRUSS-BRACED WING AIRCRAFT: PHASE 4

FINAL REPORT

The subject grant NAG-I-2217 was in effect from 7/1/99 to 10/31/99. The objective

of this grant was to complete a strut-braced wing study which began under grant NAG-l-

1852, which was in effect from 6/27/96 until 9/15/99. While the initial grant was on-going,

we were also under subcontract to Lockheed-Martin, Aerospace Systems Division, Mari-

etta, GA to do additional studies related to the strut-braced wing grant under contract

RV28007, "A Structural and Aerodynamic Investigation of a Strut-Braced Wing Transonic

Aircraft Concept", 4/1/98-11/15/98. Lockheed-Martin was under contract to NASA Lan-

gley under contract NAS1-96014 DA17. Finally the research under this grant has led to a

joint proposal from NASA Langley, Locheed-Martin, Virginia Tech and NASA Dryden to

develop a transonic strut-braced wing demonstration aircraft in response to NASA NRA

99-LaRC-3, Flight Research for Revolutionary Aeronautical Concepts (REVCON). This

final report summarizes the research done under NAG-1-2217, augmented by the additional

concommitant research projects mentioned above.

The transonic truss-braced wing is a highly integrated technology concept that has

large potential payoffs including aircraft weight reduction and increased cruise perfor-

mance. The operational benefits are a higher aspect ratio, lower thickness ratio, and lower

wing weight compared to the conventional cantilever wing. The reduction in thickness

allows the wing sweep to be reduced without incurring a transonic wave drag penalty and

results in a further reduction of the wing weight. The reduced wing sweep also allows a

larger percentage of the wing area to achieve natural laminar flow resulting in lower drag.

The basic idea of a transonic strut-braced wing can be traced to early studies con-

ducted from 1954 to 1981, which concluded that although the strut-braced wing concept

showed promise, it also required careful technology integration between aerodynamics and

structures. Design tools needed to perform the integrated analysis required for this concept

were not available. However, when contemporary Multidisciplinary Design Optimization

(MDO) techniques are employed to integrate the aerodynamic and structural design re-

quirements, results indicate that not only is take-off gross weight reduced by more than

10-percent, but fuel usage is reduced in excess of 20-percent. This is for the case of fuselage-

mounted engines. Significantly larger weight reductions (19% TOGW) are obtained for

the wing-mounted engine case. An extensive follow-on industry study additionally found a

42-percent reduction in emissions and a 26-percent reduction in direct operating cost when

a strut-braced wing was installed on a 2010 entry advanced transport aircraft compared

to a 1995 technology baseline aircraft.

Two key technology issues are critical. These are the aerodynamic interference penal-

ties associated with the wing-strut junction at transonic speeds, and the need for an inno-

vative tension-only strut mechanism to avoid the problem of strut buckling at the negative

g loading condition. In previous studies, the need for the strut to be strong enough to

avoid buckling under the negative g condition resulted in the transonic strut-braced wing

concept actually becoming heavier than the corresponding cantilever wing design.

In the courseof our research,three students have completedM. S. theses,Joel Gras-meyer, Amir Naghshineh-Pourand Jay Gundlach, and onestudent hascompleted a Ph.D.dissertation, Philippe T_trault. Another M.S. degree,Andy Ko and another Ph.D. degree,Erwin Sulaemanare in progress. In addition, Dr. Frank H. Gem, working as a Post-Doeparticipated fully in this research.

On January 11, 2000, Joel Grasmeyerwon the Dr. Abe M. Zarem Award for Dis-tinguished Achievement. The award was "presented as a means for students pursuingadvanced degreesin aeronautics and astronautics to showcasetheir talent and work."Joel's award was for his master's level work on "Multidiseiplinary Design Optimization ofa Truss-Braced Wing Aircraft" and was presentedat the 38th AIAA AerospaceSciencesMeeting in Reno NV.

The results of our researchmay be found in the viewgraphsat the end of this report.The researchis also reported in Refs. 1-16 below.

REFERENCES

1. Grasmeyer,J.M., "A Discrete Vortex Method for Calculating the Minimum InducedDrag and Optimum Load Distribution for Aircraft Configurations with NoncoplanarSurfaces," VPI-AOE-242, AOE Dept., Virginia Tech, Blacksburg, VA, Jan. 1997.

2. Grasmeyer, J. M., Naghshineh-Pour, A., T_trault, P.-A., Grossman, B., Haftka, R.T., Kapania, R. K., Mason, W. H. and Schetz,J. A., "Multidisciplinary Design Opti-mization of a Strut-Braced Wing Aircraft with Tip-Mounted Engines," MAD CenterReport 98-01-01,Virginia Tech,AOE Dept., Blacksburg, VA, Jan. 1998.

3. Grasmeyer, J.M., "Truss-Braced Wing Code Description and User's Manual," VPI-AOE-255, AOE Dept., Virginia Tech, Blacksburg, VA, Jan. 1998.

4. Grasmeyer,J. M., "Stability and Control Estimation and Engine-Out Analysis," VPI-AOE-0254, Virginia Tech, AOE Dept., Blacksburg, VA, Jan. 1998.

5. Grasmeyer, J. M., "Multidisciplinary Design Optimization of a Strut-Braced WingAircraft," M.S. Thesis, Virginia Polytechnic Institute and State University, Blacks-burg_VA, April 1998.

6. Naghshineh-Pour, A., Kapania, R. K. and Haftka, R. T., "Preliminary StructuralAnalysis of a Strut-Braced Wing Aircraft," VPI-AOE-0256, Virginia Tech, AOEDept., Blacksburg, VA, June 1998.

7. Nagshineh-Pour, A., "Structural Optimization and Design of a Strut-Braced Wing

Aircraft," M.S. Thesis, Virginia Polytechnic Institute and State University, Blacks-

burg, VA, Nov. 1998.

8. Gundlach, J., F., "Multidisciplinary Design Optimization and Industry Review of

a 2010 Strut-Braced Wing Transonic Transport," M.S. Thesis, Virginia Polytechnic

Institute and State University, Blacksburg, VA, May 1999.

9. Gundlach, J. F., Naghshineh-Pour, A., Gern, F., T_trault, P.-A., Ko, A., Schetz, J. A.,

Mason, W. H., Kapania, R. K., Grossman, B. and Haftka, R. T., "Multidisciplinary

Design Optimization and Industry Review of a 2010 Strut-Braced Wing Transonic

Transport," MAD Center Report 99-06-03, Virginia Tech, AOE Dept., Blacksburg,

VA, June 1999.

10. Gern, F. H., Gundlach, J., Naghshineh-Pour, A., Sulaeman, E., Tetrault, P., Gross-

man, B., Haftka, R. T., Kapania, R., Mason, W. H. and Schetz, J. A., "Multidis-

ciplinary Design Optimization of a Transonic Commercial Transport with a Strut-

Braced Wing," Paper 1999-01-5621, World Aviation Congress and Exposition, San

Francisco CA, Oct. 1999.

11. Gundlach, J., Gern, F., Tetrault, P., Nagshineh-Pour, A., Ko, A., Grossman, B.,

Haftka, R. T., Kapania, R. K., Mason, W. H., and Schetz, J. A., "Multidisciplinary

Optimization of a Strut-Braced Wing Transonic Transport," AIAA 36th Aerospace

Sciences Meeting & Exhibit, Paper No. 98-0420, Reno, NV, Jan. 2000.

12. T_trault, P.-A., Schetz, J. A. and Grossman, B., "Numerical Prediction of the In-

terference Drag of a Streamlined Strut Intersecting a Flat Wall in Transonic Flow,"

AIAA 38th Aerospace Sciences Meeting & Exhibit, Paper No. 2000-0509, Reno, NV,Jan. 2000.

13. T_trault, P.-A., "Numerical Prediction of the Interference Drag of a Streamlined Strut

Intersecting a Flat Wall in Transonic Flow," Ph.D. Dissertation, Virginia Polytechnic

Institute and State University, Blacksburg, VA, January 2000.14. Gern, F. H., Naghshineh-Pour, A., Sulaeman, E., Kapania, R. and Haftka, R. T.,

"Flexible Wing Model for Structural Wing Sizing and Multidisciplinary Design Opti-mization of aStrut-Braced Wing," AIAA-2000-1327, 41stAIAA/ASME/ASCE/AHS/ASCStructures, Structural Dynamics, and Materials Conferenceand Exhibit, Atlanta, GA,April 2000.

15. Germ F. H., Ko, A., Sulaeman, E., Tetrault, P.-A., Grossman, B., Kapania, R.,Mason, W. H., Schetz, J. A. and Haftka, R. T., "Load Alleviation and InterfcrenceDrag in the Design of a Strut-Braced Wing Transport Aircraft." Paper to appear atthe 8th AIAA/NASA/USAF/ISSMO Symposium on Multidisciplinary Analysis andOptimization, Long Beach CA, Sept. 2000.

16. Ko, A., Grossman,B., Kapania, R. K., Mason, W. H., Schetz,J. A. and Haftka, R.T., "The Role of Constraints in the MDO of a Cantilever and Strut-Braced WingTransonic Commercial Transport Aircraft." Paper submitted to the World AviationCongress and Exposition, San Diego CA, Oct. 2000.

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