Vertical Take Off & Landing (VTOL) Aircraft -- A Comparison

1. Vertical Take Off & Landing (VTOL) Aircraft -- A Comparison

2. Fixed Thrusters l Vectored Thrusters l Lift / Propulsion / Control Approaches For VTOL Aircraft(General) For Shaft-Driven VTOL Aircraft, Need At Least Two Thrusters: > One Main, One Anti-Torque > Two Equal Size (Opposite Rotation) > Thruster Tilting > Exhaust Deflection

3. Methods of Transition for Various V/STOL Concepts

4. VTOL Concepts

5. 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) PURE HELICOPTER

6. Thrust Thrust Wing Lift Velocity Wing "Lift" Velocity (Download) Wing Needs Aircraft to be Nose Up to Get Lift Main Rotor Needs Aircraft to be Nose Down to Get Propulsion Need to Get Propulsion from Someplace Other than Main Rotor SOLUTION: Add a Third Fixed Thruster (Propulsive Thruster) or Use Vectored Thrust THERE ARE MAJOR PROBLEMS WITH ADDING A WING

7. 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 HELICOPTER (Fixed Thruster)

8. 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 HELICOPTER (Advancing Blade Concept)

9. 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) • ADVANTAGES • Good Hover/Loiter Efficiency • Low Downwash • Faster Than Pure Helicopter • Good Maneuverability (Except Conversion) • Reverse Prop Thrust at High Speed COMPOUND HELICOPTER (Vectored Thruster - Open Prop)

10. 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) COMPOUND HELICOPTER (Vectored Thruster - Ducted Prop)

11. 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) CANARD ROTOR WING

12. 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 ROTOR

13. 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) TILT WING

14. 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) TILTING DUCTED FANS

15. 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) FAN-IN-WING

16. 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) VECTORED JET LIFT

17. 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, . . . ?

18. Comparison of Different Types of V/STOL Platforms