Slide 1Slide 2Methods of Transition for Various V/STOL ConceptsSlide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16SummarySlide 18Vertical Take Off & Landing Vertical Take Off & Landing (VTOL)(VTOL)AircraftAircraft----A ComparisonA ComparisonLift / Propulsion / Control ApproachesLift / Propulsion / Control ApproachesFor VTOL AircraftFor VTOL Aircraft (General)For Shaft-Driven VTOL Aircraft, Need At Least Two Thrusters: Fixed Thrusters > One Main, One Anti-Torque> Two Equal Size (Opposite Rotation) Vectored Thrusters > Thruster Tilting> Exhaust DeflectionMethods of Transition for Various V/STOL ConceptsVTOL ConceptsVTOL ConceptsPURE HELICOPTERPURE HELICOPTER ADVANTAGES•Most Efficient Hover/Loiter•Low Downwash•Good Low Speed Maneuverability•Symmetrical Yaw Control•Low Empty Weight DISADVANTAGES•Low Max Speed•Lowest Cruise Efficiency (Range)•Limited High Speed Maneuverability•Attitude Depends on Speed/Acceleration•Rotating Component RCS•Highest Vibration Environment•Complexity (2 Fixed Thrusters)Add a Third Fixed Thruster (Propulsive Thruster)orUse Vectored ThrustSOLUTION:Need to Get Propulsion from Someplace Other than Main RotorTHERE ARE MAJOR PROBLEMS WITH ADDING A WINGMain Rotor Needs Aircraft to be Nose Down to Get PropulsionVelocityThrustWing "Lift"(Download)Wing Needs Aircraft to be Nose Up to Get Lift VelocityThrustWing LiftCOMPOUND HELICOPTERCOMPOUND HELICOPTER(Fixed Thruster) ADVANTAGES•Good Hover/Loiter Efficiency•Low Downwash•Faster Than Pure Helicopter•Good Maneuverability -- All Speeds•Attitude Independent of Speed/Acceleration•Symmetrical Yaw Control•Reverse Prop Thrust -- All Speeds DISADVANTAGES•Low Cruise Efficiency (Range)•Rotating Component RCS•High Vibration Environment•Increased Empty Weight•Complexity (3 Fixed Thrusters)COMPOUND HELICOPTERCOMPOUND HELICOPTER(Advancing Blade Concept) ADVANTAGES•Good Hover/Loiter Efficiency•Low Downwash•Faster Than Pure Helicopter•Good Maneuverability -- All Speeds•Attitude Independent of Speed/Acceleration•Symmetrical Yaw Control•No Anti-Torque Rotor Required•Reverse Prop Thrust -- All Speeds DISADVANTAGES•Low Cruise Efficiency (Range)•Rotating Component RCS•High Vibration Environment•Increased Empty Weight•Complexity (3 Fixed Thrusters)COMPOUND HELICOPTERCOMPOUND HELICOPTER(Vectored Thruster - Open Prop) ADVANTAGES•Good Hover/Loiter Efficiency•Low Downwash•Faster Than Pure Helicopter•Good Maneuverability (Except Conversion)•Reverse Prop Thrust at High Speed DISADVANTAGES•Low Cruise Efficiency (Range)•Conversion (Limited Agility)•Attitude Depends on Acceleration at Low Speed•Unprotected Vectored Thruster•Rotating Component RCS•High Vibration Environment•Increased Empty Weight•Complexity (1 Fixed + 1 Vectored Thruster)COMPOUND HELICOPTERCOMPOUND HELICOPTER(Vectored Thruster - Ducted Prop) ADVANTAGES•Good Hover/Loiter Efficiency•Low Downwash•Faster Than Pure Helicopter•Good Maneuverability (Except Conversion)•Reverse Prop Thrust at High Speed•Ground Safety/Damage (Ducted Prop) DISADVANTAGES•Low Cruise Efficiency (Range)•Conversion (Limited Agility)•Limited / Unsymmetrical Yaw Control•Attitude Depends on Acceleration at Low Speed•Rotating Component RCS•High Vibration Environment•Complexity (1 Fixed + 1 Vectored Thruster)CANARD ROTOR WINGCANARD ROTOR WING ADVANTAGES•Good Hover/Loiter Efficiency•Low Downwash•Potential for High Subsonic Cruise•Good Maneuverability (Except in Conversion)•No Anti-Torque Rotor•Reduced RCS in High Speed Mode•Low Vibration Environment in High Speed Mode DISADVANTAGES•Limited Maneuverability in Conversion•Power for Yaw Control Near Hover•Moderate Vibration Environment in Low Speed & Conversion Modes•Rotating Component RCS in Low Speed Mode•Complexity (Rotor Stopping & Convertible Engine)TILT ROTORTILT ROTOR ADVANTAGES•Good Hover/Loiter Efficiency•Moderate Downwash•Good Max Speed•Good Cruise Efficiency (Range)•Good Maneuverability -- All Speeds•Attitude Independent of Speed/Acceleration•Ground Safety/Damage (No Tail Rotor) DISADVANTAGES•Greater Operating Width•Conversion (Benign)•Rotating Component RCS•Moderate Vibration Environment•Increased Empty Weight•Complexity (2 Vectored Thrusters)TILT WINGTILT WING ADVANTAGES•Fair Hover/Loiter Efficiency•Faster Than Tilt Rotor•Good Cruise Efficiency (Range)•Good High Speed Maneuverability•Attitude Independent of Speed/Acceleration•Symmetrical Yaw Control DISADVANTAGES•Marginal Downwash•Conversion (Limited Corridor)•Rotating Component RCS•Increased Empty Weight•Complexity (1 Fixed + 2 Vectored Thrusters)TILTING DUCTED FANSTILTING DUCTED FANS ADVANTAGES•Enclosed Thrusters (Safety)•Symmetrical Yaw Control DISADVANTAGES•Low Hover/Loiter Efficiency•Limited Low Speed Maneuverability•Conversion (Limited Corridor)•High Empty Weight•Complexity (1 Fixed + 2 Vectored Thrusters)FAN-IN-WINGFAN-IN-WING ADVANTAGES•High Max Speed•Good Cruise Efficiency (Range)•Attitude Independent of Speed/Acceleration•Good RCS (High Speed Mode)•Low Vibration Environment DISADVANTAGES•Low Hover/Loiter Efficiency•High Downwash / Temperature•Limited Low Speed Maneuverability•Conversion (Limited Corridor)•High Empty Weight•Complexity (3 Vectored Thrusters)VECTORED JET LIFTVECTORED JET LIFT ADVANTAGES•Highest Max Speed•Highest Cruise Efficiency (Range)•Excellent High Speed Maneuverability•Attitude Independent of Speed/Acceleration•Symmetrical Yaw Control•Low Vibration Environment•Moderate Empty Weight DISADVANTAGES•Poor Hover/Loiter Efficiency•Extreme Downwash / Temperature•Limited Low Speed Maneuverability•Conversion (Benign)•Rotating Component RCS (Forward)•Jet Exhaust IR•Complexity (1 Thruster + 8 Nozzles)Summary•VTOL Aircraft Are Inherently More Complex Than Conventional Take-Off and Landing (CTOL) Aircraft–Mechanization Required to Change Direction of Thrust With Respect to Aircraft–Additional Controllers (e.g., Collective Stick, Conversion)•“Best VTOL Concept” Only Has Meaning in the Context of the Mission to be Performed–What Do You Need Most? Hover Time, Fast Cruise, Long Range, . . . ?–What Do You Have Available? Runway, . . . ?VTOL Concept Helicopter