Flutter Analysis of the Polen Special IIFlutter Analysis of the Polen Special IIEmphasizing Addition of a Wet Wing and Emphasizing Addition of a Wet Wing and

Ailerons to Flutter ModelAilerons to Flutter Model

Structural EngineersStructural EngineersErich Gross, Masayuki WakamatsuErich Gross, Masayuki Wakamatsu

Advisor: Marcus KrugerAdvisor: Marcus Kruger

ASE463Q [Fall2002]

Final Presentation

Presentation Outline

Polen Special II Background and SpecsPolen Special II Background and Specs Project Motivation and ObjectivesProject Motivation and Objectives Past Polen Group WorkPast Polen Group Work Flutter TheoryFlutter Theory AMAFALAAMAFALA Objectives Completed (Results)Objectives Completed (Results) Conclusions Conclusions

Polen Special II Background

Designed by Dennis PolenDesigned by Dennis Polen

Aluminum body, cantilevered low-wing, conventional Aluminum body, cantilevered low-wing, conventional

gear monoplane gear monoplane

Designed to achieve high speed (300mph+)Designed to achieve high speed (300mph+)

Development began in 1967Development began in 1967

First flew in 1972First flew in 1972

Currently owned by Dick KeytCurrently owned by Dick Keyt Ex-Air Force, current American Airlines PilotEx-Air Force, current American Airlines Pilot

Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

Polen Special II Background

Designed as a racing airplaneDesigned as a racing airplane Mr. Keyt participates in various competitionsMr. Keyt participates in various competitions A longer range would be desirableA longer range would be desirable Wings are the only practical place to store Wings are the only practical place to store

additional fueladditional fuel Addition of wing fuel tanks was one of the Addition of wing fuel tanks was one of the

primary project objectivesprimary project objectives

Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

Polen Special II Specifications

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

Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

Critical Problem and Project Motivation: Insufficient Flutter Analysis

Rudder DamageRudder Damage

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

Courtesy of Spring 2001 463Q group

Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

Past Polen Groups’ Works

Fall 2000 & Spring 2001 (Not Accessible)Fall 2000 & Spring 2001 (Not Accessible) GVT, Modal Studies GVT, Modal Studies

Summer 2001Summer 2001 AMAFALA user manual & initial input filesAMAFALA user manual & initial input files

Fall 2001Fall 2001 Revision of input files & wing tip EI and GJRevision of input files & wing tip EI and GJ

Spring 2002Spring 2002 Completed general Polen ModelsCompleted general Polen Models

Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclustion

Project Objectives

Research flutter and analyze past dataResearch flutter and analyze past data Learn AMAFALALearn AMAFALA

Add components to the Polen modelAdd components to the Polen model Ailerons (Case 1)Ailerons (Case 1) Fuel Tanks [Wet Wing]Fuel Tanks [Wet Wing]

(Case 2, Case 3)(Case 2, Case 3)

Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

Team Organization

Dr. Ronald StearmanConsultant

Department of Aerospace Engineering and Engineering Mechanics

The University of Texas at Austin

Marcus KrugerAdviser

Masayuki Wakamatsu

Theoretical ResearchPast Group Data Analysis

AMFAFALA Editing

Erich GrossTeam Leader

Team OrganizationPast Group Data Analysis

AMAFALA Editing

Javier Fuentealba

AMAFALA Consultant

Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

Phenomena of Flutter (Flutter Theory)

Definition: a self excited vibration of a flexible Definition: a self excited vibration of a flexible body [ASE355 notes]body [ASE355 notes]

Imagine a ball in these conditionsImagine a ball in these conditions  

a) Stable b) Neutral c) Unstable

Flutter speed is defined as a minimum (neutral Flutter speed is defined as a minimum (neutral condition) speed at flutter occurscondition) speed at flutter occurs

  

Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

Flutter Video!

Courtesy of www.airspacemag.com

Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

Causes of Flutter (Flutter Theory)

Inability of an airframe to dissipate energy Inability of an airframe to dissipate energy to the airstreams to the airstreams Airframe—elastic; deflects due to Airframe—elastic; deflects due to

bending and torsionbending and torsion New geometry - new aerodynamic forceNew geometry - new aerodynamic force And so on…And so on…

Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

To find the Flutter Speed

Eigenvalue problemsEigenvalue problems i.e. seek the flutter speed and frequencyi.e. seek the flutter speed and frequency

Structural Analysis and AerodynamicsStructural Analysis and Aerodynamics V-g MethodV-g Method

Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

To find the Flutter Speed (V-g method)Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

g: artificial structural g: artificial structural damping (< 0.033)damping (< 0.033)

Mach number and altitude Mach number and altitude are held constantare held constant

V-g plot shows when flutter may occur

AMAFALA outputs a V-g plot

Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

Flutter: Symmetric VS Antisymmetric

(a) symmetric (b) Antisymmetric

Two primary flutter conditions of interest: symmetric and 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

AMAFALA (Airplane Modal Aerodynamic Flutter And Loads Analysis)

A text-based flutter analysis programA text-based flutter analysis program Past 463Q teams worked with itPast 463Q teams worked with it

This is the main tool that we used in our This is the main tool that we used in our analysisanalysis

Hard to learn- took two years for past groups to Hard to learn- took two years for past groups to run the programrun the program

We modified existing input files created by We modified existing input files created by Javier Fuentealba rather than creating new onesJavier Fuentealba rather than creating new ones

Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

AMAFALA (Airplane Modal Aerodynamic Flutter And Loads Analysis)

AMAFALA InputsAMAFALA Inputs Geometric Data (layout of wing)Geometric Data (layout of wing) Mass Data (inertial strips)Mass Data (inertial strips) Stiffness Data (inertial strips)Stiffness Data (inertial strips) Aerodynamic DataAerodynamic Data

AMAFALA OutputsAMAFALA Outputs Mode FrequenciesMode Frequencies Mode ShapesMode Shapes V-g PlotsV-g Plots

Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

Wing Input File Overview

Input file contains geometric and mass data Input file contains geometric and mass data

required to model the flutter characteristics of the required to model the flutter characteristics of the

wingwing

Original input file was complete except for the Original input file was complete except for the

addition of ailerons and wing fuel tanksaddition of ailerons and wing fuel tanks

We modified the original wing input file by We modified the original wing input file by

adding the ailerons and fuel tanks to the wingadding the ailerons and fuel tanks to the wing

Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

Wing Input File Overview

Visual Representation of Data Contained in Wing Input File

New wing tanks

Aileron

Aileron CG

Results: Case 1 (Original, Antisymmetric Condition) Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

No flutter occurrence is indicated for this condition

Results: Case 1 (with Ailerons, Antisymmetric Condition)Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

Flutter occurs at roughly 350 knots

Results: Case 2 (New Fuel Tanks, Antisymmetric)Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

Flutter occurs at roughly 350 knots

Note: This is identical to Case 1

New fuel tanks empty

Results: Case 2 (New Fuel Tanks, Antisymmetric)Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

Flutter occurs at roughly 290 knots60 knots slower than for no additional tank case

New fuel tanks half full

Results: Case 2 (New Fuel Tanks, Antisymmetric)Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

New fuel tanks full

Flutter speed has fallen to 190-200 knotsFlutter is being induced!

Results: Case 3 (Fuel, Symmetric)Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

New fuel tanks empty

Flutter occurs at roughly 350 knots

Results: Case 3 (Fuel, Symmetric)Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

New fuel tanks half full

Flutter speed has fallen to 200 knots (conservative)Realistically, flutter speed is probably closer to 275 knots

Results: Case 3 (Fuel, Symmetric)Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

New fuel tanks full

Flutter speed is now approximately 250-260 knotsFlutter speed is decreasing as fuel is added

Conclusions

Case 1 [aileron, antisymmetric]Case 1 [aileron, antisymmetric] Flutter occurs at around 350 knotsFlutter occurs at around 350 knots

Case 2 [antisymmetric, new fuel tanks]Case 2 [antisymmetric, new fuel tanks] Case 3 [symmetric, new fuel tanks]Case 3 [symmetric, new fuel tanks]

Flutter speed decreases with the addition of Flutter speed decreases with the addition of

fuel to the new tanksfuel to the new tanks This is counterintuitive and undesirableThis is counterintuitive and undesirable Centers of gravity for the new tanks must be Centers of gravity for the new tanks must be

moved closer to the wing leading edgemoved closer to the wing leading edge This will mean less fuel can be carried in the This will mean less fuel can be carried in the

wingwing

Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

Conclusion (Recommendations)Outline1) Polen &

Project background

2) Flutter

3) AMAFALA

4) Results

5) Conclusion

Learn AMAFALA ASAPLearn AMAFALA ASAP Develop more precise wet wing modelDevelop more precise wet wing model

i.e, get more information about the structure i.e, get more information about the structure

of the wing and edit wing file accordinglyof the wing and edit wing file accordingly Develop an external fuel tank modeDevelop an external fuel tank mode

Questions?