vtol aircraft comparision
DESCRIPTION
soliton.ae.gatech.edu/people/dschrage/.../VTOL%20Aircraft.pptTRANSCRIPT
Vertical Take Off & Landing
(VTOL)
Aircraft --
A Comparison
Lift / Propulsion / Control Approaches
For VTOL Aircraft (General)
For Shaft-Driven VTOL Aircraft, Need At Least Two Thrusters:
l Fixed Thrusters
> One Main, One Anti-Torque
> Two Equal Size (Opposite Rotation)
l Vectored Thrusters
> Thruster Tilting
> Exhaust Deflection
Methods of Transition for
Various V/STOL Concepts
VTOL Concepts
PURE 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)
or
Use Vectored Thrust
SOLUTION:
Need to Get Propulsion from Someplace Other than Main Rotor
THERE ARE MAJOR PROBLEMS WITH
ADDING A WING
Main Rotor Needs Aircraft to
be Nose Down to Get Propulsion
Velocity
Thrust
Wing "Lift"
(Download)
Wing Needs Aircraft to
be Nose Up to Get Lift
Velocity
Thrust
Wing Lift
COMPOUND 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 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 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 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 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 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 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 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-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 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 Compound Compound Compound Compound Tilt Rotor Tilt WingCanard Rotor
WingFan-in-Wing Jet Lift
Features (Tail Rotor +
Aux Prop)
(Advancing
Blade Concept)
(Vectrd Thrst -
Open Prop)
(Vectrd Thrst -
Ducted Prop)
ExamplesAH-64,
RAH-66AH-56 Sikorsky XH-59
Sikorsky
AAFSSPiasecki VTDP
XV-3, XV-15,
V-22
CL-84, TW-68,
XC-142Boeing CRW
XV-5, Grum-
man ACASAV-8B
Hover / Loiter / Ground Ops
Efficiency (Endurance) Best Good Good Good Good Good Fair Low Low Poor
Downwash / Temperature Low Low Low Low Low Moderate Marginal Marginal High Extreme
Ground Ops Protection Optional Open Prop No Anti-Torque Open Prop Ducted Prop --- Optional No Anti-Torque --- Jet Exhaust
Cruise / Dash
Max Speed (Dash) Low > Helicopter > Helicopter > Helicopter > Helicopter Good > Tilt Rotor High High Highest
Cruise Efficiency (Range) Lowest Low Low Low Low Good Good Good Good Highest
Maneuverability / Agility
Low Speed Good Good Good Good Good Good Fair Limited Limited Limited
High Speed Limited Good Good Good Good Good Good Good Good Excellent
Conversion --- --- --- Limited Agility Limited Agility Benign Lmtd Corridor Lmtd Corridor Lmtd Corridor Benign
Attitude vs Accel (Low Speed) Coupled Independent Coupled Coupled Coupled Independent Independent Independent Independent Independent
Reverse Thrust Capability --- All Speeds --- High Speed High Speed --- High Speed --- --- ---
Yaw Control Symmetrical Symmetrical Symmetrical SymmetricalLimited /
UnsymmetricalSymmetrical Symmetrical
Limited in Low
SpeedSymmetrical Symmetrical
Survivability
RCS (Low Speed Mode) Rotating Blade Rotating Blade Rotating Blade Rotating Blade Rotating Blade Rotating Blade Rotating Blade Rotating Blade Doors / Louvers Short Inlet
RCS (High Speed Mode) Rotating Blade Rotating Blade Rotating Blade Rotating Blade Rotating Blade Rotating Blade Rotating Blade Good Good Short Inlet
IR (Engine Exhaust) Lowest Power Low Power Low Power Low Power Low Power Low Power Medium Power High Power High Power Short Exhaust
Cost / Supportability
Vibration Environment Highest High Very High High High Moderate --- Moderate Low Low
Empty Weight Low Increased Increased Increased Increased Increased Increased Increased High Moderate
Complexity
(Min # of Thrusters)2 Fixed 3 Fixed 2 Fixed
1 Fixed +
1 Vectored
1 Fixed +
1 Vectored2 Vectored
1 Fixed +
2 Vectored
Convertib le
Engine3 Vectored
1 Thruster +
8 Nozzles
Key to Table: Advantage Neutral Disadvantage
Comparison of Different Types of V/STOL Platforms