ASE463Q Final Report
Flutter Analysis of the Polen Special II
Addition of Ailerons and a Wet Wing to the Flutter Model
Submitted to:
Dr. Ronald O. Stearman
Department of Aerospace Engineering and Engineering Mechanics
The University of Texas at Austin
Austin, TX
Written by:
Erich Gross
Masayuki Wakamatsu
Department of Aerospace Engineering and Engineering Mechanics
The University of Texas at Austin
Austin, TX
December 6, 2002
December 6th , 2002
c/o The University of Texas at Austin
Department of Aerospace Engineering and Engineering Mechanics
Austin, TX 78712
Ronald O. Stearman
The University of Texas at Austin
Austin, TX 78712
Dr. Stearman:
We have completed our AMAFALA flutter analysis focusing on the addition of ailerons and a wet wing to the flutter model of the Polen Special II aircraft. We have researched the phenomenon of aerodynamic flutter, studied the work of students who participated in this project in the past, learned how to use the AMAFALA flutter simulation package, and edited Javier Fuentealba’s existing flutter model to include the ailerons and a preliminary wet wing design.
Our results are indicating that the flutter speeds for the aircraft range between 210 and greater than 400 knots CAS, depending on the altitude, fuel levels, and flutter symmetry conditions specified. It appears that the addition of ailerons to the wing of the flutter model has no significant impact on the aircraft’s flutter speeds. Because of this we would not expect aileron flutter to pose a threat to the aircraft’s future operation. The wet wing fuel tanks had more of an impact on flutter speeds, and after closely analyzing our results, we recommend that the wet wing model we developed be used as a framework to develop a more realistic wet wing model. Nevertheless, we feel that the wet wing model we developed shows the feasibility of implementing a wet wing design on the actual aircraft.
We hope that the work we have done this semester is useful to groups working on the project in the future. With some refinement of the wet wing model, we feel that a very accurate model of the aircraft can be created, one that may help Mr. Keyt make decisions regarding future modifications to his aircraft.
Sincerely,
Erich Gross
Masayuki Wakamatsu
ASE 463Q Final Report
Flutter Analysis of the Polen Special II
Addition of Ailerons and a Wet Wing to the Flutter Model
Abstract
The Polen Special II is a one-of-a-kind experimental aircraft. Its designer, Dennis Polen, never completed any formal flutter analyses of the aircraft. The Polen’s current owner, Mr. Dick Keyt, experienced serious rudder flutter in 1999 during a low altitude fly-by. After this flutter incident, the Department of Aerospace Engineering at the University of Texas at Austin teamed up with Mr. Keyt to analyze the flutter characteristics of the Polen. The Fall 2002 Polen group started the project with the goal of finding the aircraft’s flutter speeds when ailerons and additional fuel tanks were added to the existing Polen model. The original Polen AMAFALA model was constructed by a graduate student, Mr. Javier Fuentealba. Three cases are analyzed in this report: (1) addition of ailerons [antisymmetric flutter condition], (2) addition of new fuel tanks (wet wing model) [antisymmetric], (3) addition of new fuel tanks (wet wing model) [symmetric].
AMAFALA is the main tool used to find the flutter speeds, and it outputs V-g plots and mode shapes. The result of this analysis for case 1 was that flutter speed was found to be 350 knots with ailerons added, faster than the symmetric condition flutter speed of the original flutter model lacking ailerons. This indicates that aileron flutter will not be an issue for the aircraft. For cases 2 and 3, the flutter speed decreased as the new wing fuel tanks were filled. However, the flutter speeds were acceptable both at sea level and at an altitude of 25,000 ft, and some additional analysis performed in the future should lead to a more optimal design.
Acknowledgements
We would first like to thank Mr. Bill Brock allowing us unlimited access to his AMAFALA software package. The availability of the software on WRW LRC computers has made learning about and using AMAFALA much simpler than if we only had limited access to the software. We would also like to thank Mr. Brock for providing an excellent users guide for AMAFALA; it has proven invaluable in learning the structure of the input files we are working with.
Next, we would like to thank Marcus Kruger for acting as our advisor this semester. His guidance and knowledge of AMAFALA and the Polen Special II have made him an important resource to us this semester.
We would also like to thank Javier Fuentealba for his help with AMAFALA. Mr. Fuentealba has a great wealth of knowledge of AMAFALA, and he created the input files for the aircraft that we will be using this semester. Javier was always able to pinpoint problems with our AMAFALA code, and we are grateful to have had his assistance this semester.
Finally we would like to thank Dr. Stearman for instilling in us a great interest in the Polen Special II and allowing us technical consultations. Dr. Stearman also made it possible for us to see the Polen Special II in person and meet as well as converse with the experienced pilot and owner of the aircraft, Mr. Dick Keyt.
Table of Contents
Cover letter ii
Abstract iii
Acknowledgements iv
Table of Contents v
List of Figures & Tables vii
1.0 Introduction 1
1.1 Aircraft History 1
1.2 Project History 3
1.3 Team Organization 5
1.4 Semester Goals 5
2.0 Flutter Theory 7
2.1 Phenomena of Flutter 7
2.2 Causes of Flutter 8
2.3 Seeking Flutter Speed and Frequency 9
2.4 Structural Damping and the V-g plot 10
2.5 Analysis of V-g Plot 12
3.0 AMAFALA 14
3.1 Input Files 15
3.2 Wing Input File –Initial Data 16
3.3 Wing Input File—Geometric Data 18
3.4 Mass Data 19
3.5 Stiffness Data 21
3.6 Aerodynamic Data 22
3.7 Flutter Input File 24
3.8 Wing Input File –Visual Representation 27
4.0 Results 28
4.1 New Aileron Model Antisymmetric [Case 1] 28
4.2 New Fuel Tanks, Antisymmetric [Case 2] 30
4.3 New Fuel Tanks, Symmetric [Case 3] 33
4.4 Results Summary 36
5.0 Conclusions 37
5.1 Recommendations 38
6.0 References 40
Appendix A: Schedule of the Polen Group 41
Appendix B: GVT damping Data 42
Appendix C: Mass and CG Data of the Polen Special II 43
Appendix D: Mr. Javier Fuentaebla’s AMAFALA input files 44
Appendix E: V-g plot of the Polen Special II, Symmetric Condition 61
Appendix F: Mode Shapes of Aileron Model 62
Appendix G: Fall 2002 AMAFALA Input Files 67
List of Figures & Tables
Figures
1.1 The rudder damage to the Polen 2
2.1a-c Examples of static stability 8
2.5 Three example of V-g plot 12
3.2 Condition of an airplane (a) Symmetric, (b) Antisymmetric 14
3.3 Graphical depiction of wing input file 16
3.6 AMAFALA Wing Sections 23
3.8 Wing Input File Drawing 27
4.1-1 V-g plot of the Original Configuration, Antisymmetric, Sea Level 28
4.1-2 V-g plot of the Aileron Model, Antisymmetric, Sea Level 29
4.2-1 V-g Plot of Empty Fuel, Sea Level, Antisymmetric Condition 31
4.2-2 V-g Plot of Full Fuel, Sea Level, Antisymmetric Condition 31
4.2-3 V-g Plot of Empty Fuel, 25,000 ft, Antisymmetric Condition 32
4.2-4 V-g Plot of Full Fuel, 25,000 ft, Antisymmetric Condition 32
4.3-1 V-g Plot of Empty Fuel, Sea Level, Symmetric Condition 34
4.3-2 V-g Plot of Full Fuel, Sea Level, Symmetric Condition 34
4.3-3 V-g Plot of Empty Fuel, 25,000ft, Symmetric Condition 35
4.3-4 V-g Plot of Full Fuel, 25,000ft, Symmetric Condition 35
Tables
1.1 Specifications for the Polen Special II 1
1.2 Summary of past projects 4
3.2 Initial Input Data 16
3.3 Geometric Input Data 18
3.4 Mass Input Data 19
3.5 Stiffness Input Data 21
3.6 Aerodynamic Input Data 22
3.7(a) Flutter Input File 25
3.7(b) Flutter Input File 26
4.4 Total Results of the Analysis Conducted 36
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