1. Flutter Analysis of the Polen Special II Emphasizing Addition of a Wet Wing and Ailerons to Flutter Model
ASE463Q [Fall2002]
Final Presentation
Structural Engineers Erich Gross, Masayuki Wakamatsu
Advisor: Marcus Kruger

2. Presentation Outline Polen Special II Background and Specs
Project Motivation and Objectives
Past Polen Group Work
Flutter Theory
AMAFALA
Objectives Completed (Results)
Conclusions

3. Polen Special II Background
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclusion
Polen Special II Background
Designed by Dennis Polen
Aluminum body, cantilevered low-wing, conventional
gear monoplane
Designed to achieve high speed (300mph+)
Development began in 1967
First flew in 1972
Currently owned by Dick Keyt
Ex-Air Force, current American Airlines Pilot

4. Polen Special II Background
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclusion
Designed as a racing airplane
Mr. Keyt participates in various competitions
A longer range would be desirable
Wings are the only practical place to store additional fuel
Addition of wing fuel tanks was one of the primary project objectives

5. Polen Special II Specifications
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclusion
Polen Special II (Specifications courtesy of the EAA)
Model Year: 1967
Engine: Lycoming TSIO-360
Horsepower: 180 hp normally aspirated, 200 hp turbocharged
Number of Seats: 1
Length: 19'6“
Height: 4'10“
Wing Span: 21'5“
Gross Weight: 1,500 lbs.
Max Speed: 345 mph
Cruise Speed: 325 mph
Service Ceiling: 28,000 feet

6. Critical Problem and Project Motivation: Insufficient Flutter Analysis
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclusion
Rudder Damage
Courtesy of Spring Q group
High frequency rudder flutter occurred during a low-pass fly-by
Fortunately, Mr. Keyt landed safely
Mr. Keyt requested a flutter analysis from the ASE department at UT Austin
Project has been developed since Fall 2000

7. Past Polen Groups’ Works
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclustion
Fall 2000 & Spring 2001 (Not Accessible)
GVT, Modal Studies
Summer 2001
AMAFALA user manual & initial input files
Fall 2001
Revision of input files & wing tip EI and GJ
Spring 2002
Completed general Polen Models

8. Project Objectives Research flutter and analyze past data
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclusion
Research flutter and analyze past data
Learn AMAFALA
Add components to the Polen model
Ailerons (Case 1)
Fuel Tanks [Wet Wing]
(Case 2, Case 3)

9. Team Organization Outline Dr. Ronald Stearman Marcus Kruger
Polen & Project background
Flutter
AMAFALA
Results
Conclusion
Team Organization
Dr. Ronald Stearman
Consultant
Department of Aerospace Engineering and Engineering Mechanics
The University of Texas at Austin
Marcus Kruger
Adviser
Masayuki Wakamatsu
Theoretical Research
Past Group Data Analysis
AMFAFALA Editing
Erich Gross
Team Leader
Team Organization
AMAFALA Editing
Javier Fuentealba
AMAFALA Consultant

10. Phenomena of Flutter (Flutter Theory)
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclusion
Definition: a self excited vibration of a flexible body [ASE355 notes]
Imagine a ball in these conditions
a) Stable
b) Neutral
c) Unstable
Flutter speed is defined as a minimum (neutral condition) speed at flutter occurs

11. Flutter Video! Outline Polen & Project background Flutter AMAFALA
Results
Conclusion
Flutter Video!
Courtesy of

12. Causes of Flutter (Flutter Theory)
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclusion
Inability of an airframe to dissipate energy to the airstreams
Airframe—elastic; deflects due to bending and torsion
New geometry - new aerodynamic force
And so on…

13. To find the Flutter Speed
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclusion
Eigenvalue problems
i.e. seek the flutter speed and frequency
Structural Analysis and Aerodynamics
V-g Method

14. To find the Flutter Speed (V-g method)
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclusion
g: artificial structural damping (< 0.033)
Mach number and altitude are held constant
V-g plot shows when flutter may occur
AMAFALA outputs a V-g plot

15. Flutter: Symmetric VS Antisymmetric
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclusion
Two primary flutter conditions of interest:
symmetric and antisymmetric
(a) symmetric
(b) Antisymmetric
For aileron flutter, we are concerned with the
antisymmetric case because ailerons are designed to
deflect antisymmetrically
We need to look at both symmetric and antisymmetric cases
to assess the changes caused by the new fuel tanks

16. AMAFALA (Airplane Modal Aerodynamic Flutter And Loads Analysis)
A text-based flutter analysis program
Past 463Q teams worked with it
This is the main tool that we used in our analysis
Hard to learn- took two years for past groups to run the program
We modified existing input files created by Javier Fuentealba rather than creating new ones
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclusion

17. AMAFALA (Airplane Modal Aerodynamic Flutter And Loads Analysis)
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclusion
AMAFALA Inputs
Geometric Data (layout of wing)
Mass Data (inertial strips)
Stiffness Data (inertial strips)
Aerodynamic Data
AMAFALA Outputs
Mode Frequencies
Mode Shapes
V-g Plots

18. Wing Input File Overview
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclusion
Input file contains geometric and mass data required to model the flutter characteristics of the wing
Original input file was complete except for the addition of ailerons and wing fuel tanks
We modified the original wing input file by adding the ailerons and fuel tanks to the wing

19. Wing Input File Overview
Visual Representation of Data Contained in Wing Input File
New wing tanks
Aileron
Aileron CG

20. Results: Case 1 (Original, Antisymmetric Condition)
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclusion
No flutter occurrence is indicated for this condition

21. Results: Case 1 (with Ailerons, Antisymmetric Condition)
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclusion
Flutter occurs at roughly 350 knots

22. Results: Case 2 (New Fuel Tanks, Antisymmetric)
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclusion
New fuel tanks empty
Note: This is identical to Case 1
Flutter occurs at roughly 350 knots

23. Results: Case 2 (New Fuel Tanks, Antisymmetric)
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclusion
New fuel tanks half full
Flutter occurs at roughly 290 knots
60 knots slower than for no additional tank case

24. Results: Case 2 (New Fuel Tanks, Antisymmetric)
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclusion
New fuel tanks full
Flutter speed has fallen to knots
Flutter is being induced!

25. Results: Case 3 (Fuel, Symmetric)
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclusion
New fuel tanks empty
Flutter occurs at roughly 350 knots

26. Results: Case 3 (Fuel, Symmetric)
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclusion
New fuel tanks half full
Flutter speed has fallen to 200 knots (conservative)
Realistically, flutter speed is probably closer to 275 knots

27. Results: Case 3 (Fuel, Symmetric)
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclusion
New fuel tanks full
Flutter speed is now approximately knots
Flutter speed is decreasing as fuel is added

28. Conclusions Case 1 [aileron, antisymmetric]
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclusion
Case 1 [aileron, antisymmetric]
Flutter occurs at around 350 knots
Case 2 [antisymmetric, new fuel tanks]
Case 3 [symmetric, new fuel tanks]
Flutter speed decreases with the addition of
fuel to the new tanks
This is counterintuitive and undesirable
Centers of gravity for the new tanks must be moved closer to the wing leading edge
This will mean less fuel can be carried in the wing

29. Conclusion (Recommendations)
Outline
Polen & Project background
Flutter
AMAFALA
Results
Conclusion
Learn AMAFALA ASAP
Develop more precise wet wing model
i.e, get more information about the structure
of the wing and edit wing file accordingly
Develop an external fuel tank mode

30. Questions?