INTRODUCTION TO HELICOPTER AERODYNAMICS WORKBOOK
NAVAL AIR TRAINING COMMANDNAS CORPUS CHRISTI, TEXASCNATRA P-401 (REV 09-00)INTRODUCTION TO HELICOPTERAERODYNAMICS WORKBOOKAERODYNAMICS TRANSITIONHELICOPTER2000
DEPARTMENT OF THE NAVYCHIEF OF NAVAL AIR TRAININGNAVAL AIR STATIONCORPUS CHRISTI, TEXAS 78419-5100N31431.CNAT P-401 (Rev. 9-00) PAT, Introduction to Helicopter Aerodynamics Workbook,Aerodynamics, Transition Helicopter, is issued for information, standardization of instructionand guidance of instructors and student naval aviators in the Naval Air Training Command.2.This publication will be used to implement the academic portion of the TransitionHelicopter curriculum.3.Recommendations for changes shall be submitted to CNATRA Code N3121. POC isDSN 861-3993. COMM (512) 961-3993/ CNATRA FAX is 861-3398.4.CNAT P-401 (Rev. 9-99) PAT is hereby canceled and superseded.Distribution:CNATRA (5)COMTRAWING FIVE (Academics) (395) ) Plus Originals, Code 70000)
STUDENT WORKBOOKQ-2A-0015INTRODUCTION TO HELICOPTERAERODYNAMICS WORKBOOKPrepared byCOMTRAWING FIVE7480 USS ENTERPRISE ST SUITE 205MILTON, FL 32570-6017Prepared forCHIEF OF NAVAL AIR TRAINING250 LEXINGTON BLVD SUITE 102CORPUS CHRISTI, TX 78419-5041SEPTEMBER 2000iii
LIST OF EFFECTIVE PAGESDates of issue for original and changed pages are:Original.0. (this will be the date issued)TOTAL NUMBER OF PAGES IN THIS PUBLICATION IS 82 CONSISTING OF THE FOLLOWING:Page No.Change No.Page No.Change No.COVER03-220LETTER04-1 – 4-120iii -ix04-13 (blank)0x (blank)04-1401-1 - 1605-1 – 5-1402-1 – 2-1405-15 (blank)03-1 – 3-2005-1603-21 (blank)00iv
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TABLE OF CONTENTSSTUDENT WORKBOOK TITLE PAGE . iiiLIST OF EFFECTIVE PAGES . ivCHANGE RECORD.vTABLE OF CONTENTS. viWORKBOOK PLANTERMINAL OBJECTIVE. viiiINSTRUCTIONAL MATERIAL. viiiDIRECTIONS TO STUDENT . viiiAUDIOVISUAL . viiiWORKBOOK TEXTCHAPTER ONE - THE ATMOSPHEREOBJECTIVES . 1-1ATMOSPHERIC PROPERTIES. 1-2ATMOSPHERIC PRESSURE . 1-2ATMOSPHERIC DENSITY AND POWER REQUIRED . 1-2REVIEW QUESTIONS. 1-5REVIEW ANSWERS. 1-6CHAPTER TWO - ROTOR BLADE AERODYNAMICSOBJECTIVES . 2-1DEFINITIONS. 2-2THEORIES OF HELICOPTER FLIGHT . 2-4AIRFOILS. 2-6PITCHING MOMENTS. 2-6ROTOR SYSTEMS . 2-9REVIEW QUESTIONS. 2-12REVIEW ANSWERS. 2-13CHAPTER THREE - HELICOPTER POWERED FLIGHT ANALYSISOBJECTIVES . 3-1POWER REQUIRED . 3-3POWER REQUIRED AND POWER AVAILABLE. 3-5TORQUE . 3-6STABILITY AND CONTROL . 3-7vi
VORTICES . 3-9GROUND EFFECT . 3-10GROUND VORTEX . 3-12TRANSLATIONAL LIFT. 3-12DISSYMETRY OF LIFT . 3-12PHASE LAG. 3-13BLOWBACK. 3-14TRANSVERSE FLOW AND CONING . 3-15BLADE TWIST . 3-16CENTER OF GRAVITY. 3-17REVIEW QUESTIONS. 3-21REVIEW ANSWERS. 3-22CHAPTER FOUR - AUTOROTATIONOBJECTIVES . 4-1FLOW STATES AND DESCENDING FLIGHT . 4-2AUTOROTATION . 4-3AUTOROTATION ENTRY. 4-4CUSHIONING THE TOUCHDOWN. 4-5AIRSPEED AND ROTOR SPEED CONTROL . 4-7HEIGHT-VELOCITY DIAGRAM . 4-10REVIEW QUESTIONS. 4-13REVIEW ANSWERS. 4-14CHAPTER FIVE - FLIGHT PHENOMENAOBJECTIVES . 5-1RETREATING BLADE STALL. 5-3COMPRESSIBILITY EFFECT. 5-5VORTEX RING STATE . 5-6POWER REQUIRED EXCEEDS POWER AVAILABLE . 5-8GROUND RESONANCE . 5-9DYNAMIC ROLLOVER . 5-10MAST BUMPING . 5-12VIBRATIONS . 5-14REVIEW QUESTIONS. 5-16REVIEW ANSWERS. 5-17GLOSSARY . G-1vii
NAVAL AIR TRAINING COMMANDADVANCED PHASEDISCIPLINE: AerodynamicsCOURSE TITLE: Aerodynamics (Transition Helicopter)PREREQUISITES: NoneTERMINAL OBJECTIVEUpon completion of the course, "Aerodynamics, Transition Helicopter," the student will possessan understanding of aerodynamics as applied to helicopters, to include the effects of atmosphere.The student will demonstrate a functional knowledge of the material presented throughsuccessful completion of an end-of-course examination with a minimum score of 80%.INSTRUCTIONAL MATERIALTo implement this learning session, the instructor in charge must ensure that one copy of theNATOPS Flight Manual, Navy Model TH-57B/C Helicopter, NAVAIR 01-110-HCC-1, beavailable to each student.When the material listed above has been assembled, the student will proceed in accordance withthe following directions:DIRECTIONS TO THE STUDENTSTEP 1STEP 2STEP 3STEP 4STEP 5Complete each chapter of the course workbook text.Take the review test for each chapter.Attend aero review before exam.Take the end-of-course examination. Remedial sessions prescribed if necessary.End of this course of instruction.AUDIOVISUALStock No.MinutesChapter 1Atmospheric Density and Helicopter Flight4B88/519:30Chapter 2Rotor Blade Aerodynamics - Part 1Rotor Blade Aerodynamics - Part 24B88/1-14B88/1-212:00Chapter 3Helicopter Powered Flight Analysis - Part 1Helicopter Powered Flight Analysis - Part 24B88/2-14B88/2-214:0019:50Chapter 4Autorotational Flight4B88/313:00viii
Chapter 5Helicopter Flight Phenomena - Part 1Helicopter Flight Phenomena - Part 2Helicopter Flight Phenomena - Part 3ix4B88/4-14B88/4-24B88/4-326:3014:0012:00
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CHAPTER ONETHE ATMOSPHERETERMINAL OBJECTIVE1.0Upon completion of this chapter, the student will define density altitude, the factorsaffecting it, and the effect density altitude has on aircraft performance.ENABLING OBJECTIVES1.1Recall the main gases of the air.1.2Recall the effect of pressure, temperature, and humidity on the density of the air.1.3Define pressure altitude.1.4Define density altitude.1.4.1Recall the effect of temperature and humidity on density altitude.1.4.2Compute the density altitude using a density altitude chart.1.4.3Compute the density altitude using the rule of thumb formula.1.4.4Recall the relationship between helicopter performance and density altitude.THE ATMOSPHERE 1-1
CHAPTER 1HELICOPTER AERODYNAMICS WORKBOOKTHE ATMOSPHEREATMOSPHERIC PROPERTIESHelicopter aerodynamics is the branch of physics dealing with the forces and pressuresexerted by air in motion. The atmosphere, the mass of air, which completely envelops the earth,is composed of varying and nonvarying constituents. The nonvarying constituents includeoxygen (21%) and nitrogen (78%). The varying constituents include CO2, argon, hydrogen,helium, neon, krypton, and water vapor, which will vary from negligible amounts toapproximately 4% by volume (100% relative humidity). Air is a fluid and is affected by changesin temperature, pressure, and humidity.ATMOSPHERIC PRESSUREAtmospheric pressure at any altitude is a result of the downward pressure exerted from themass of air above that altitude. The air at the surface of the earth will be under a greater pressurethan air further up a given column of air. Pressure altitude is defined as an altitudecorresponding to a particular static air pressure in the standard atmosphere. The standardatmosphere corresponds to the temperature and pressure of the standard day (15 C, 29.92 or10MB, 14.7 psi at sea level). Therefore, the pressure altitude of a given static air pressurecorresponds to the actual altitude only in the rare case where atmospheric conditions between sealevel and the aircraft's altimeter correspond exactly to that of the standard atmosphere.ATMOSPHERIC DENSITY AND POWER REQUIREDAtmospheric density is also greatest at the earth's surface and the atmosphere becomes lessdense, or contains fewer molecules per unit volume, as distance from the earth's surfaceincreases. Atmospheric density also decreases with an increase in temperature or humidity.Heated air expands, causing the air molecules to move farther apart, thus decreasing air densityper unit volume. As relative humidity increases, water vapor molecules, which have a smallermolecular mass than oxygen and nitrogen molecules, displace some air molecules in a givenvolume, creating a decrease in density in a given volume.Density altitude is the altitude in the standard atmosphere corresponding to a particular airdensity. It is pressure altitude corrected for temperature and humidity. Air density affects theaerodynamic forces on the rotor blades and the burning of fuel in the engine, affecting bothpower required and power available. For a given set of atmospheric conditions, the total powerrequired to drive the rotor depends on three separate requirements, which have a common factor-- rotor drag. Each power requirement is considered separately, and will be discussed in greaterdepth in a later section.1. Rotor Profile Power (RPP). This is the power requirement to overcome friction drag ofthe blades. RPP assumes a constant minimum pitch angle and a constant coefficient of dragvalue. As density altitude increases and air density decreases, drag, and therefore RPP, willdecrease. However, blade stall begins sooner, so more of the blade is in stall, increasing profilepower.1-2 THE ATMOSPHERE
HELICOPTER AERODYNAMICS WORKBOOKCHAPTER 12. Induced power. This is the power associated with producing rotor thrust and must besufficient to overcome the induced drag which increases proportionally to thrust. In order tomaintain rotor thrust as air density decreases, angle of attack (AOA) must be increased byincreasing pitch on the rotor blades. The resulting increase in rotor drag requires an increase ininduced power to maintain a constant Nr. Increased density altitude affects induced powersignificantly.3. Parasite power. This is the power required to overcome the friction drag of all theaircraft components, rotor blades being the exception. Parasite drag is constant for a given IAS.As density altitude (DA) increases, TAS increases, and parasite drag will decrease slightly.The combination of these ups and downs result in greater power required at a higher densityaltitude.Power required, the amount of power necessary to maintain a constant rotor speed, isadversely affected by increased DA and decreased rotor efficiency. The pitch angle of the bladesmust be increased to increase the AOA during high DA conditions in order to generate the sameamount of lift generated during low DA conditions. Increased pitch angle results from anincreased collective setting, which demands more power from the engine.DA also affects power available, or engine performance. Turbine engine performance willbe adversely affected by an increase in DA. As DA increases, the compressor must increaserotational speed (Ng) to maintain the same mass flow of air to the combustion chamber; and thebottom line is, when maximum Ng is reached on a high DA day, there is a lower mass flow of airfor combustion, and therefore (because of fuel metering) a lower fuel flow as well. Thus, withincreased DA, power available from a gas turbine engine is reduced.Since DA affects helicopter rotor and engine performance, it is a necessary consideration forsafe preflight planning. It can be determined in two ways: deriving a value from NATOPScharts (figure 1-1) or a “rule of thumb” which can be used in the aircraft when no chart isavailable (see figure 1-2).THE ATMOSPHERE 1-3
CHAPTER 1HELICOPTER AERODYNAMICS WORKBOOKFigure 1-1Density Altitude/Temperature Conversion ChartIncrease DA 100' for each 10% increase in relative humidityFigure 1-21-4 THE ATMOSPHERE
HELICOPTER AERODYNAMICS WORKBOOKCHAPTER 1CHAPTER ONE REVIEW QUESTIONS1. Oxygen comprises approximately percent of the earth's atmosphere.2. Air density changes in direct proportion to and inverse proportionto , , and .3. Compared to dry air, the density of air at 100% humidity isa.b.c.d.4% more dense.about the same.decreased 1 percent per 1000'.less dense.4. The altitude of a given static air pressure in the standard atmosphere is .5. Density altitude is pressure altitude corrected for and .6. When relative humidity is 50%, the moist air is half as dense as dry air. (True/False)7. As temperature increases above standard day conditions, density altitude increases/decreasesand air density increases/decreases.8. Using the Density Altitude Chart on page 1-4, find the density altitude for a pressure altitudeof 3500', temperature of 240C, and relative humidity of 50%.9. Using the rule of thumb formula, calculate the density altitude for a pressure altitude of6000', temperature of 170C, and relative humidity of 50%.10. An increase in humidity increases/decreases density altitude, which increases/decreases rotorefficiency.11. State the effects that increased density altitude has on power available and power required.THE ATMOSPHERE 1-5
CHAPTER 1HELICOPTER AERODYNAMICS WORKBOOKCHAPTER ONE REVIEW ANSWERS1. 212. pressure . . . altitude . . . temperature . . . humidity3. d4. pressure altitude5. temperature . . . humidity6. false7. increases . . . decreases8. 5900'9. 8180'10. increases . . . decreases11. Power available decreases and power required increases.1-6 THE ATMOSPHERE
CHAPTER TWOTERMINAL OBJECTIVE2.0Upon completion of this chapter, the student will be able to construct a blade elementdiagram, defining each of its components, and state their interrelationships. The studentwill be able to identify the forces acting on the rotor system and their effects on the system.ENABLING OBJECTIVES2.1Draw a blade element diagram.2.1.1Define the following terms: Airfoil, chord line, tip-path-plane, aerodynamic center,rotor disk, pitch angle, linear flow, induced flow, angle of attack, lift, induced drag,profile drag, thrust, and in-plane drag.2.1.2State the relationships between induced flow, linear flow, and relative wind;between relative wind and angle of attack; between pitch angle and angle of attack.2.2Differentiate between and characterize the symmetrical and nonsymmetrical airfoils.2.3Define geometric twist and state why it is used in helicopter design.2.4Define flapping.2.5Define geometric imbalance.2.5.12.6State how geometric imbalance affects horizontal blade movement (lead/lag).Differentiate between and characterize the three types of rotor systems in use today.2.6.1State the method by which flapping is accomplished in each system.2.6.2State the method by which geometric imbalance is compensated for or eliminated ineach system.THE ATMOSPHERE 1-1
CHAPTER 2HELICOPTER AERODYNAMICS WORKBOOKROTOR BLADE AERODYNAMICSDEFINITIONSTo begin our discussion of rotary wing aerodynamics, we will start with a few basicdefinitions using figure 2-1 as a reference. A chord line is the line connecting the leading edgeof the blade to the tip of the trailing edge. The chord is defined as the distance between theset
CHAPTER 1 HELICOPTER AERODYNAMICS WORKBOOK 1-2 THE ATMOSPHERE THE ATMOSPHERE ATMOSPHERIC PROPERTIES Helicopter aerodynamics is the branch of physics dealing with the forces and pressures exerted by air in motion. The atmosphere, the mass of air, which completely envelops the earth, is composed of varying and nonvarying constituents.
described as “Introduces helicopter and propeller analysis techniques. Momentum and blade-element, helicopter trim. Hover and forward flight. Ground effect, autorotation and compressibility effects” (Arizona State Universiy, 2014). The required textbook is Principles of Helicopter Aerodynamics by Gordon Leishman of the University of Maryland.
Aerodynamics is the study of the dynamics of gases, or the interaction between moving object and atmosphere causing an airflow around a body. As first a movement of a body (ship) in a water was studies, it is not a surprise that some aviation terms are the same as naval ones rudder, water line, –File Size: 942KBPage Count: 16Explore furtherIntroduction to Aerodynamics - Aerospace Lectures for .www.aerospacelectures.comBeginner's Guide to Aerodynamicswww.grc.nasa.govA basic introduction to aerodynamics - SlideSharewww.slideshare.netBASIC AERODYNAMICS - MilitaryNewbie.comwww.militarynewbie.comBasic aerodynamics - [PPT Powerpoint] - VDOCUMENTSvdocuments.netRecommended to you b
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0521858607 - Principles of Helicopter Aerodynamics, Second Edition J. Gordon Leishman Excerpt More information. 6 1 / Introduction: A History of Helicopter Flight combustion engines with sufficient power-to-weight ratios suitable for use on a helicopter did not occur until the 1920s. 3. Keeping structural weight and engine weight down so the .
Unit 91: Principles of Helicopter Flight and Aerodynamics Unit code: A/600/7347 QCF Level 3: BTEC Nationals Credit value: 10 Guided learning hours: 60 Aim and purpose This unit will develop learners’ knowledge and understanding of the principles of helicopter flight and will give them an understanding of how it is controlled. Unit introduction
6.13 Human-Powered Helicopter 331 6.14 Hovering Micro Air Vehicles 334 6.15 Chapter Review 338 6.16 Questions 338 Bibliography 340 7 Aerodynamics of Rotor Airfoils 347 7.1 Introduction 347 7.2 Helicopter Rotor Airfoil Requirements 348 7.3 Reynolds Number and Mach Number Effects 350 7.3.1 Re
Principles of Helicopter Aerodynamics Second Edition The helicopter is truly a unique form of aircraft and a mastery of modern aeronau-tical engineering that fulfills a variety of civilian and military roles.
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