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Theory of Flight Flight Performance

Theory of Flight Flight Performance

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Theory of Flight Flight Performance

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  1. Theory of FlightFlight Performance

  2. Reference From the Ground Up Chapters 2.1.5, 2.1.6, 2.1.7: Flight Performance Factors, Airspeed Limitations, Mach Number Pages 26 - 33

  3. Introduction • There are many factors that affect an aircraft’s flight performance. As well, the four forces are manipulated to be able to maneuver an aircraft.

  4. Outline • Flight Performance Factors • Climbing, Gliding & Turns • Stalls, Spins & Spiral Dives • Load Factor & Airspeed

  5. Torque In nose-engine aircraft, propeller rotates clockwise (as seen by pilot) Result: Roll to left (counterclockwise rotation from equal and opposite reaction) Correction: Slight right-turning tendency built-in to aircraft

  6. Asymmetric Thrust At high angles of attack and high power setting (i.e. take-off), descendingpropeller blade has greater angle of attack than ascending blade Right side of prop produces more thrust then left side Result: Yaw to left Correction: Use right rudder

  7. Precession Spinning propeller acts like a gyroscope: When force applied to spinning gyro, force acts as if it was 90° in direction of rotation Result: Quick Nose-Up = Sharp yaw right Quick Nose-Down = Sharp yaw left Correction: Use opposite rudder Tail-wheel aircraft prone to precession when nose pushed forward on take-off

  8. Slipstream Propeller pushes air back in corkscrew motion which hits left side of fin (pushing it right) Result: Constant yaw to left (depending on power setting) Correction: Offset fin, trim, right rudder

  9. Climbing Ability to climb dependent on thrust: More thrust needed at higher altitudes Thrust Lift Angle of Attack Increase: More lift, less speed Decrease: Less lift, more speed Drag Weight

  10. Climbing - Shorter Time- Longer Distance - Longer Time- Shorter Distance Best Angle of Climb (Vx) Most altitude in least horizontal distance (used for obstacles) Best Rate of Climb (Vy) Most altitude in least time (used on normal take-off) Normal Climb Used during cruise

  11. Gliding Gliding = 3 forces (Weight, Lift, Drag) Glide Reaction = Resultant of liftand drag, opposesweight Lift Drag Thrust = Horizontalcomponent of weight Weight

  12. Gliding Best Range SpeedFurthest distance per altitude lost Best Endurance SpeedMost time in air peraltitude lost - Longer Time- Shorter Distance - Shorter Time- Longer Distance

  13. Turns Vertical Component of Lift Keeps aircraft in air (opposes weight) Lift Centripetal Force Horizontal component of lift, pulls aircraft into turn Centrifugal Force Imaginary force that pulls aircraft outside of turn (is really inertia) Weight Angle of Bank

  14. Turns • Shallow Bank • Lesser turn rate • Larger turn radius • Lower Stall Speed • Less Wing Loading • Steep Bank • Greater turn rate • Smaller turn radius • Higher Stall Speed • More Wing Loading

  15. Turns • Faster Airspeed • Lesser turn rate • Larger turn radius • Slower Airspeed • Greater turn rate • Smaller turn radius Same bank angle

  16. Turns • Load Factors in Turns • Angle of bank increase • = Load factor increase • 60° bank = 2 G's • Dangers • High load factor • = Possible structural failure(overload) • Increased load factor • = Increased stall speed

  17. Stalls • Definition: Wing can’t create enough lift to support weight • When Critical Angle of Attack (Stall Angle) reached, turbulent airflow surpasses laminar airflow on wing • C of P rapidly moves towards trailing edge • Aircraft can stall at any airspeed or attitude if critical angle of attack is exceeded • Aircraft will stall at same indicated airspeed regardless of altitude

  18. Factors Affecting Stall • Weight • More weight = higher angle of attack (closer to stall angle) • C of G • Forward = higher stall speed • Rearward = lower stall speed • Turbulence • Upward vertical gust could cause aircraft to exceed stall angle • Turns • Angle of bank increase = Stall speed increase (load factor/weight) • Flaps • Increasing lifting potential of wing = Stall speed decrease • Aircraft Condition • Snow, Frost, Ice, Dents = Disrupted laminar flow (increases stall speed)

  19. Spins • Definition: Auto-rotation which develops after aggravated stall • When wing drops in stall: • Down-going wing has greater angle of attack • Wing receives less lift, drops more rapidly • Drag on down-going wing increases, further increasing angle of attack • Wing stalls further, nose drops, auto-rotation starts

  20. Spins

  21. Spiral Dives • Definition: Steep descending turn in which airplane has excessive nose down attitude • Characteristics: • Excessive angle of bank • Rapidly increasing airspeed • Rapidly increasing rate of descent • Structural damage can occur if airspeed increases beyond limits

  22. Spiral Dives

  23. Spins vs Spiral Dives • Spin: • Aircraft stalled • Airspeed constant and low • Spiral Dive: • Aircraft not stalled • Airspeed increasing rapidly

  24. Airspeed Limits • Never Exceed Speed (VNE) • Max speed airplane can be operated in smooth air • Normal Operating Speed (VNO) • Design cruise speed, should not be intentionally exceeded • Maneuvering Speed (VA) • Max speed at which flight controls can be fully deflected without damage to structure • Maximum Flaps Extended Speed (VFE) • Max speed at which full flaps can be used

  25. Mach Number • Ratio of speed of body to speed of sound (in air surrounding body) • Mach 1 = Speed of sound • Varies with air temperature, pressure and density

  26. Next Lesson 2.5 - Theory of Flight Flight Instruments From the Ground Up Chapter 2.2: Flight Instruments Pages 33 - 44