Proceedings of AEROTECH-II 2007 Conference on Aerospace Technology of XXI Century, 20-21 June 2007, Kuala Lumpur AEROTECH-II-AN005.doc PARAMETRIC STUDY OF THE FLUTTER CHARACTERISTICS OF TRANSPORT AIRCRAFT WINGS Harijono Djojodihardjo and Yee Hong Hoe Universiti Sains Malaysia, Engineering Campus 14300 Nibong Tebal, Seberang Perai Selatan, Pulau Pinang harijono@djojodihardjo.com, Tel: 04-599 5947, Fax: 04-5941026 ABSTRACT With the progress of aircraft technology, materials and lighter aircraft structures, modern aircrafts are de- signed to be lighter and much more flexible. For the aircraft designers, manufacturers, as well as operators, the state of the art and trends of the structural dynamic characteristics of modern aircraft structures are of great interest and relevance. For instructional and conceptual study purposes, it would be of advantage to look into a simple method that may give instructive results. It is with such objectives that the present study is carried out. Various modern transport aircrafts are classified and investigated in view of their structural dy- namic and aeroelastic characteristics of their wing structure. For this purpose, the basic philosophy and formulation of flutter phenomena as reflected in the generic binary flutter problem is revisited and reflected to real aircraft for general understanding and conceptual design purposes. To this end, a parametric study is carried out on the influence of geometrical and elastic properties of the wing structure on their structural dynamic and aeroelastic characteristics, in view of their performance and aeroelastic stability design re- quirements. Keywords: aeroelasticity, aircraft design, aerody- namics 1. INTRODUCTION With the progress of aircraft technology, materials and lighter aircraft structures, modern aircrafts are designed to be lighter and much more flexible. For the aircraft designers, manufacturers, as well as operators, the state of the art and trends of the struc- tural dynamic characteristics of modern aircraft structures are of great interest and relevance. For instructional and conceptual study purposes, it would be of advantage to look into a simple method that may give indicative results. It is with such ob- jectives that the present study is carried out. Here an analytical approach is followed to investigate the structural dynamic and aeroelastic characteristics of the wing structure of modern transport aircrafts and to obtain some correlation between some repre- sentative specifications to their structural dynamic and aeroelastic characteristics of their wing struc- ture. For conceptual design and instructional purposes, it would be desirable to be able to identi- fy certain pertinent correlation between structural characteristics and flutter perspectives. It is with such objectives in mind that we will look into a fundamental equation governing flutter, and for this purpose the basic two-degree of freedom aeroelas- tic equation for typical section will be revisited. A typical section, which is usually taken at 70-75% of the wing span from the root has been considered to be representative of the aeroelastic behavior of the wing[1-3]. Two problems will be investigated, these are the flutter stability analysis, and the solu- tion of flutter equation using the classical VG or K- Method, chosen for its eloquence. Along this line a simple (non-exhaustive) parametric study will be carried out, to illustrate structural characteristics relevant for flutter behavior. For this purpose, we will look into three different aerodynamics approx- imation in the flutter equation, all for the incompressible case, to obtain the influence of such approximation to flutter behavior. For this purpose, the well known BAH (Bisplinghoff-Ashley- Halfman) typical section, modified as required, will be utilized, which also serves as benchmarking purposes. For flutter stability analysis, the analysis well elab- orated in Zwaan[3], using Done’s aeroelastic stability analysis the generic bending-torsion binary flutter of typical section will be closely followed. For the solution of the flutter equation to obtain the onset of flutter, VG or K-Method as described in AGARD Manual on Aeroelasticity [4] will be uti- lized. Results of the analysis will be discussed in view of actual aircraft data. Hence, in addition for its usefulness for instructional purposes, this inves- tigation will be useful for conceptual and preliminary design purposes for which simple but representative parametric studies could be based on such basic analytical tool. 2. TYPICAL SECTION REPRESENTATION OF 3-D WING FOR AEROELASTIC ANALYSIS