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AERSP 407 and AERSP 504Aerodynamics of V/STOL Aircraft

Kenneth S. BrentnerDepartment of Aerospace Engineering

The Pennsylvania State University

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AERSP 407 and 504

Goals:To introduce and study key concepts related to aerodynamic loads, vehicle performance, basic rotor dynamics, and control of helicopters and tilt-rotor aircraft.

Time: Monday, Wednesday, Friday: 1:25-2:15pm

Place:151 Willard Building

Instructor:Dr. Kenneth S. Brentner233 D Hammond BuildingTel: (814) 865-6433Email: ksbrentner@psu.edu

Office Hours: Monday and Wednesday 10:30-11:30am; by appointment; I also have an open door policy.

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Reference Materials

Textbook:Principles of Helicopter Aerodynamics,

J. Gordon Leishman

I will be basing lecture note primarilyon this book.

Other Good References:Aerodynamics of V/STOL Flight, B. W. McCormick, Jr.Helicopter Theory, W. JohnsonRotary-Wing Aerodynamics, W. Z. Stepniewski and C. N. KeysAerodynamics of the Helicopter, A. Gessow and G. C. Meyers

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Outline

1. Introduction (also read Chapter 1)2. Fundamentals of Rotor Aerodynamics (Chapter 2)3. Blade Element Analysis (Chapter 3)4. Blade Motion and Rotor Control (Chapter 4)5. Basic Helicopter Performance (Chapter 5)6. Conceptual Design of Helicopters (first part of Chapter 6)7. Introduction to Unsteady Aerodynamics, Dynamic Stall,

and Rotor Wakes – time permitting (portions of Chapters 7-10)

This is my first time teaching this course, so I don’t have dates for when we will cover each of the sections.

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Grading – AERSP 407

Homework and computer assignments – 35%Approximately 7-8 assignments

Mid-term exam20% in class10% take-home tentatively Oct 21, 2005

Final exam - 35%Term paper - extra credit

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Grading – AERSP 504

Homework and computer assignments – 20%Mid-term exam

20% in class10% take-hometentatively Oct 21, 2005

Final exam – 35%Term paper and presentation – 15%

Topic due Sept. 30Outline due Oct. 28Paper due Nov 23Presentations – sometime during last two weeks of class.

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Academic Integrity

Faculty Senate Rule 49-20 states, in part, "Academic integrity is the pursuit of scholarly activity free from fraud and deception and is an educational objective of this institution."

Faculty are required to clarify the application of this rule to each course:

You are encouraged to study together and to discuss the homework assignments, but the work that you submit for grading must be your own.

Acts of academic dishonesty will result in either a grade of zero for an assignment, or an F for the course.

If you have any questions about this, please feel free to talk to me first – this will avoid any problems.

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About Your Instructor:Kenneth S. Brentner

EducationBS Aeronautics and Astronautics, Purdue University – 1983MS Aerodynamics, The George Washington University – 1987Ph.D. Acoustics, University of Cambridge (UK) – 1991 (J.E. Ffowcs Williams, advisor)

Experience(1983 – 2000) Senior Research Engineer at NASA Langley Research Center

Rotorcraft AcousticsComputational AeroacousticsAuthor of WOPWOP rotorcraft noise prediction program

(2000 – present) Associate Professor at The Pennsylvania State University, Department of Aerospace EngineeringPersonal

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Today’s Lecture

Introduction to CourseAdministrationMotivation

Introduction to HelicopterLay ground work for Helicopter Aerodynamics

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What is a Helicopter?

Leishman“Helicopters are highly capable and useful rotating-wing

vehicles that have a variety of civilian and military applications. Their usefulness lies in their unique ability to take off and land vertically, to hover stationary to the ground,and to fly forward, backwards, or sideways. These unique flying qualities, however, come at a price, including complex aerodynamic problems, significant vibrations, high levels of noise, and relatively large power requirements compared to fixed-wing aircraft.”

Unique features:Rotating-wing vehiclesAbility to hoverLand and take off verticallyFly forward, backward, and sideways

Helicopters are closely related to autogiros and tiltrotors

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Introduction and Motivation

A unique aspect of a helicopter is its ability to hover.The ability to hover is a very useful attribute

Example: A hummingbird is able to feed on the nectar in flowers by hovering for several seconds at a time.

Photo: Luiz Claudio Marigo

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Introduction:Helicopters at Work

Helicopters perform a wide range of missions that benefit from this unique capability (hover or vertical lift)

Scheduled Passenger Service

Executive Transport

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Introduction:Helicopters at Work

source: www.hmc.psu.edu/lifelion

Medical evacuation

source: www.hmc.psu.edu/lifelion

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Introduction:Helicopters at Work

source: helispot.comPacific Rotors Magazine

Aerial fire fightingAerial Logging

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Introduction:Helicopters at Work

Agricultural: crop spraying

Heavy Lift (tiltrotor in helicopter mode)

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Introduction:Helicopters at Work

Boeing AH-64

Military Helicopters

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Comparison of Fixed-Wing Aircraft and Helicopters

Fixed Wing AircraftWings produce lift and roll controlEngines produce thrustTail – primarily for directional and pitch control

Primary functions and controls are decoupled

HelicopterRotor

Produces liftProduces thrustProduces directional control

AND – unbalanced torque!Lift, Thrust, and Control are all

coupled in a helicopter

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Unique Helicopter Problems1. Rotor Torque2. Unequal Lift3. Higher Power Requirements

More power required than a F/W aircraft at any forward velocityTurbine engines; composites; improved rotor airfoils all helped

4. ControlTilting of thrust vector (mechanically difficult)

Swashplate and cyclic pitchCross coupling of motions (pitch, roll, yaw, etc.)

5. Structural Weight6. Vibration and Dynamics Issues7. Interactional Aerodynamics8. Costs and Complexity

Direct Operating Costs (DOC) of helicopter is significantly higher than fixed-wing aircraftMaintenance hours / flight hour also higher

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Rotor Torque Control

Ways of countering the Reactive Torque

Other possibilities: Tip jets, tip mounted engines

Question: Why do each of these methods work?What are the likely advantages and disadvantages of each?

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Main Rotor - Tail Rotor Configuration

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Tandem Rotors (Chinook)

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Coaxial Rotors (Kamov KA-52)

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NOTAR Helicopter

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NOTAR Concept

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Tilt Rotor (BA 609)

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Unequal Lift Distribution

Ref: Principles of Helicopter Aerodynamics, J. Gordon Leishman

tipV R= Ω

tipV R V∞= Ω +

tipV R V∞= Ω −

Lift ~ V2

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High-Speed Forward Flight Limitations

As the forward speed increases, advancing side experiences shock effects, retreating side stalls. This limits thrust available.Vibrations go up, because of the increased dynamic pressure, and increased harmonic content.Shock noise goes up.Fuselage drag increases, and parasite power consumption goes up as V3.We need to understand and accurately predict the air loads in high speed forward flight.

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Interactional Aerodynamics

The aerodynamic environment for a helicopter rotor is complex – rotor aerodynamics important for:

PerformanceStructural AnalysisDynamicsFlight DynamicsAcoustics…

This is my area of research

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Next Time

Read Chapter 1We will start on Momentum Theory for a hovering rotor