Acknowledgements The Griffin design team wishes to acknowledge the following people and thank them for their guidance and assistance. Dr. Vengalattore T. Nagaraj - Senior Research Scientist, Dept. of Aerospace Engineering, University of Maryland, College Park Dr. Inderjit Chopra - Interim Chair, Gessow Professor, and Director of Gessow Rotorcraft Center (AGRC), Dept. of Aerospace Engineering, University of Maryland, College Park Dr. J. Gordon Leishman - Minta Martin Professor of Engineering, Dept. of Aerospace Engineering, University of Maryland, College Park Dr. Roberto Celi - Professor, Dept. of Aerospace Engineering, University of Maryland, College Park Dr. Fredric Schmitz - Senior Research Professor, Dept. of Aerospace Engineering, University of Maryland, College Park Dr. James Baeder - Associate Professor, Dept. of Aerospace Engineering, University of Maryland, College Park Dr. Darryll J. Pines - Dean, Clark School of Engineering and Professor, Dept. of Aerospace Engineering, University of Maryland, College Park Dr. Norman Wereley - Professor, Dept. of Aerospace Engineering, University of Maryland, College Park Dr. Christopher Cadou - Associate Professor, Dept. of Aerospace Engineering, University of Maryland, College Park Dr. Sean Humbert - Assistant Professor/Director, Autonomous Vehicle Laboratory, Dept. of Aerospace Engineering, University of Maryland, College Park Dr. Shreyas Ananthan - Assistant Research Scientist, Dept. of Aerospace Engineering, University of Maryland, College Park Jaye Falls, Jason Pereira, Peter Copp, Arun Jose, Monica Syal, Abhishek Roy, Moble Benedict, Vikram Hrishikeshavan, Brandon Bush, Nicholas Wilson, Daniel C. Sargent, Richard Sickenberger, Evan Ulrich, Ben Woods, Bradley Johnson, Ben Berry : Graduate students at the Dept. of Aerospace Engineering, University of Maryland, College Park Dr. Manikandan Ramasamy - NASA AMES Dr. Jinsong Bao - Dynamics and Acoustics, Sikorsky Aircraft, Co. Dr. Preston B. Martin - Research Scientist, NASA Ames Research Center Dr. A.R. Manjunath - Additional General Manager, Hindustan Aeronautics Limited, Bangalore, India.] LCDR Scott Stringer - MH-60S Class Desk, Naval Air Systems Command, NAS Patuxent RIver, MD Mr. Jeffrey DeBruin - Air Vehicle Engineering Department, Aeromechanics Division, Rotary Wing Performance Branch, Naval Air Systems Command, Patuxent River, MD Maryland State Police Aviation Command, Fredrick Station Section “Trooper 3”. 1 Contents Table of Contents ................................................. i List of Figures ................................................... vi List of Tables .................................................... ix RFP Compliance .................................................. x Executive Summary ................................................I 1 Introduction .................................................... 1 2 Vehicle Configuration Selection .......................................... 1 2.1 Identification of Design Drivers ...................................... 1 2.2 Selection of Baseline Helicopter ...................................... 1 2.3 Primary Mission Profile Determination .................................. 3 2.4 Quality FunctionDeployment ....................................... 3 2.4.1 Design Criteria - Value Engineering ............................... 3 2.5 Feasible VTOLTechnology ........................................ 4 2.5.1 Compounding .......................................... 4 2.5.2 StoppedRotor .......................................... 4 2.5.3 TipSpeedModulation ...................................... 6 2.5.4 Tilting Thrust .......................................... 6 2.5.5 VectoredThrust ......................................... 6 2.5.6 TorquelessRotor ......................................... 7 2.6 PughDecisionMatrix ........................................... 7 2.7 Trade Study of Tip Speed ModulationConcepts .............................. 7 2.8 Griffin’s Rotor/Drive System: VERITAS ................................. 9 3 Initial Sizing .................................................... 10 3.1 Descriptionof Methodology ........................................ 10 3.2 TradeStudies ................................................ 11 3.2.1 Choice ofBlade LoadingCoefficient .............................. 11 3.2.2 ChoiceofTipSpeed ....................................... 11 3.2.3 ChoiceofNumberofBlades .................................. 11 3.2.4 Choice of Rotor Solidity ..................................... 13 3.3 FinalConfiguration ............................................. 14 4 Drivetrain .................................................... 14 4.1 Configuration ................................................ 14 4.2 Engines ................................................... 15 4.3 Multi-SpeedGearbox ............................................ 16 i 4.3.1 AlternativeApproaches ..................................... 16 4.3.2 Operation ............................................ 16 4.3.3 DualClutch ........................................... 18 4.3.4 Geartrain ............................................. 19 4.3.5 GearSelection .......................................... 19 4.3.6 GearSynchronization ...................................... 20 4.3.7 Lubrication ........................................... 20 4.3.8 Housing ............................................. 20 4.3.9 FailureModes and EffectsAnalysis ............................... 21 4.4 MainRotorGearbox ............................................ 21 4.4.1 Design .............................................. 21 4.4.2 Housing ............................................. 23 4.4.3 Accessories ........................................... 23 4.5 ElectronicControls ............................................. 23 4.6 TailPropGearbox ............................................. 23 4.6.1 IntermediateGearbox ...................................... 24 4.6.2 SwivelingMechanism ...................................... 24 4.6.3 EmergencyRecall Mechanism ................................. 24 4.7 Maritime Considerations .......................................... 25 5 MainRotorandHubDesign ........................................... 25 5.1 Main Rotor AerodynamicDesign ..................................... 25 5.1.1 AirfoilSelection ......................................... 25 5.1.2 PlanformDesign ......................................... 26 5.1.3 Blade Twist ........................................... 27 5.1.4 BladeTaper ........................................... 27 5.1.5 DesignoftheTALONTip .................................... 27 5.2 Blade StructuralDesign .......................................... 29 5.2.1 ChoiceofMaterials ....................................... 29 5.2.2 Composite Coupling ....................................... 29 5.2.3 CompositeLay-UpandSizing ................................. 30 5.2.4 De-icingsystem ......................................... 30 5.2.5 Leading-edgeerosionguard ................................... 30 5.2.6 LightningProtection ....................................... 31 5.2.7 ElectromagneticShielding .................................... 31 5.2.8 Slip Ring ............................................. 31 5.3 Active Flaps for Vibration Control ..................................... 31 5.3.1 Selection of Trailing-Edge Flap Configuration ......................... 31 5.4 Vibration Reduction in the Griffin ..................................... 33 5.4.1 Definition of Vibration Levels .................................. 33 5.4.2 Vibration Reduction Attained Using Trailing-Edge Flaps ................... 34 5.5 Flap ActuationMechanism ......................................... 35 5.6 Active Vibration Control Scheme ..................................... 36 5.7 Performance Improvement with Trailing-Edge Flaps ........................... 36 5.8 SafetyAspects ............................................... 37 5.9 HubDesign ................................................. 37 5.9.1 RotorMast and Swashplate Assembly ............................. 37 5.9.2 Clover Plate ........................................... 38 ii 5.9.3 Elastomeric Frequency Adapter – Lead-Lag Damper ...................... 38 5.9.4 ElastomericConical Bearing .................................. 38 5.9.5 Bladefolding .......................................... 38 5.10 RotorDynamics .............................................. 39 5.10.1 Aeroelastic Stability Analysis .................................. 40 5.10.2 GroundResonance ........................................ 41 6 Empennage and Tail Prop Design ........................................ 42 6.1 EmpennageConstruction .......................................... 42 6.1.1 Tailboom ............................................. 42 6.1.2 H–tail .............................................. 42 6.1.3 CentralFin ............................................ 42 6.2 TailPropDesign .............................................. 43 6.3 Tail Prop Construction ........................................... 43 6.4 Accessibility ................................................ 44 7 Performance Analysis ............................................... 44 7.1 DragEstimation .............................................. 44 7.2 DragReduction ............................................... 45 7.2.1 FuselageDrag – Synthetic Jet Actuators ............................ 45 7.2.2 Rotor Hub, Pylon and Engine Installation ............................ 46 7.2.3 MainRotorDrag ......................................... 46 7.2.4 TailPropDrag .........................................