EB14-1 Theory of Flight & EB14-2 Effects of Control & Flight Envelope - Study Notes

Theory of Flight (EB14-1)

  • Course information

    • Aircraft Course Number: EB14-1
    • Title: Theory of Flight
    • Version: V1.0
    • Effective date: 06.08.2025
    • Lesson Coordinator: Salvador García

  • Structural overview: Fixed-wing aircraft (page references in deck)

    • Main structural components: Wing, Fuselage (flight deck, crew, passengers & cargo), Elevator, Tailplane, Flap, Aileron, Rudder, Landing Gear (Nose wheel), Main Landing Gear, Vertical Stabiliser
    • Wing geometry concepts: Transition, Relative Airflow, Max Lift, Critical angle of attack, Angle of attack (deg)
    • Wing configurations (structural components): low wing, mid wing, high wing, inverted gull, gull wing, Anhedral wing, Dihedral wing

  • The four forces acting on an aircraft in flight (page 6)

    • Drag
    • Lift
    • Weight
    • Thrust

  • Weight (Definition and role) (Page 7)

    • Weight: the force due to Earth's gravity acting downward toward the Earth's center
    • It acts irrespective of aircraft attitude
    • Question posed: Which force is always acting on the aircraft? Answer: Weight

  • Lift (Definition and generation) (Page 8)

    • Lift enables an aircraft to fly by opposing weight
    • Lift is generated by an aerofoil’s motion through the air and is an aerodynamic force
    • Lift is produced by the interaction between the wing and the airflow

  • The Bernoulli Principle (Page 9)

    • Conceptual idea: differences in air pressure above and below a wing contribute to lift
    • Diagram shows higher pressure on one side and lower pressure on the other corresponding to velocity changes around the wing

  • How aircraft get more lift (Page 10)

    • Factors influencing lift: Chord, Flight Path, Angle of Attack (AoA)
    • Definitions:
    • Stalled vs Attached lift regimes
    • As AoA increases, lift generally increases up to a point; beyond that, stall may occur
    • Relationship details:
    • For small AoA: Lift increases with AoA
    • For larger AoA: The lift–AoA relationship becomes complex, involving the lift coefficient C_L(α)
    • Key takeaway: Lift is related to AoA and the lift coefficient (C_L)

  • Thrust (Page 11)

    • Thrust is the mechanical force provided by propulsion system to move the aerofoil through the air
    • Purpose: enables the aerofoil to produce lift by moving through the air

  • Drag (Page 12)

    • Drag is the aerodynamic force that opposes an aircraft’s motion through the air
    • Generated by every part of the aeroplane
    • Question: Which force does thrust help to overcome? Answer: Drag

  • Flight performance constraints and limiting factors (Page 13–14)

    • Limiting factors related to flight include:
    • Maximum speeds
    • Minimum speeds and stall speeds
    • Ceiling (maximum altitude achievable in level flight)
    • Critical angle of attack (AoA where stall occurs)
    • Maximum rate of climb (RoC)
    • Rotary-wing note: Helicopters have additional/alternative undercarriage configurations and tail rotor considerations (see rotary-wing section in later slides)

  • Rotary-wing aircraft structural components (Page 14)

    • Components listed: Wing concepts translated to rotorcraft: Tail rotor, Under-carriage, Fairing, Tail plane, Cabin, Tail boom
    • Helicopters may have non/partially retractable undercarriage, skids, or floats
    • Optional rotor configurations: contra-rotating discs, NOTAR (No Tail Rotor) propulsion concepts

  • Interim contact point (Page 16–17)

    • EB14-2: Effects of Control & Flight Envelope (continuation from EB14-1)

Flight Controls (EB14-2)

  • Controlling flight (Overview) (Page 18)

    • Primary flight-control surfaces: Rudder, Elevators, Ailerons
    • These are hinged or movable surfaces that allow a pilot to adjust attitude during take-off, flight manoeuvres, and landing
    • Control surfaces are operated via connecting linkages to rudder pedals and a control column (yoke)
    • Inputs allow rotation about one, two, or three axes simultaneously

  • Aircraft axes of rotation (Page 19)

    • Lateral axis (roll)
    • Vertical axis (yaw)
    • Longitudinal axis (pitch)

  • The Rudder (Page 20–21)

    • Purpose: Used for directional control; yawing movement about the vertical axis
    • Function: Enables the aircraft to yaw left or right; not the primary surface used to “turn” the aircraft in the sense of changing bank angle—the rudder aids coordinated flight and yaw control
    • Practical note: Rudder input affects the yaw and relative airflow, influencing lift distribution across wings

  • Elevators (Page 22–25)

    • Purpose: Used for longitudinal control; pitch up or down
    • Function: Change the aircraft’s attitude to climb or descend
    • Mechanism: Pushing the control column forward makes elevators move down, causing the tail to rise and the nose to drop; results in descent
    • Conversely: Pulling the control column back makes elevators move up, tail down, nose up; results in climb

  • Ailerons (Page 26–28)

    • Purpose: Used for lateral control; roll about the longitudinal axis
    • Mechanism: When the stick is moved left or right, opposing ailerons move in opposite directions to tilt the wings and roll the aircraft
    • Example: Roll left causes left aileron to move up and right aileron to move down; roll right reverses

  • Trim tabs (Page 31–33)

    • Definition: Auxiliary flight-control surfaces allowing adjustments during flight to correct unbalance
    • Function: Reduce continual control forces required by the pilot by keeping the aircraft trimmed
    • Example: Nose-up trim (trim tab down) vs Elevator trim tab interactions (Trim Tab vs Elevator) – opposite direction adjustments

  • Flaps & Slats (Page 33)

    • Purpose: Increase lift at low speeds during takeoff and landing
    • How they work:
    • Flaps: Extend towards the tail to increase the wing’s effective camber, increasing lift; extension also increases drag to slow the aircraft for landing
    • Slats: Maintain laminar flow for longer, allowing higher AoA before stall
    • Overall effect: Higher lift at lower speeds, enabling safer takeoffs and landings

  • Power (Page 37)

    • Role of power: Used to overcome drag
    • Throttle effect: Increasing power raises airspeed and can contribute to climb; reducing power lowers airspeed and can cause descent

  • Helicopters: Rotary-wing controls (Page 38–43)

    • Three main inputs: Cyclic, Collective, Anti-torque pedals
    • Mixing unit: For more complex rotors, a mechanical/hydraulic link combines cyclic and collective inputs to produce the desired rotor response
    • Controls:
    • Cyclic: Tilts rotor disk to move the helicopter direction; changes blade pitch cyclically as rotor turns to tilt the rotor plane
    • Collective: Changes pitch of all rotor blades collectively to climb or descend
    • Anti-torque pedals: Similar role to rudder pedals; control tail rotor pitch to yaw the helicopter
    • Layout: Pedals at the same location as fixed-wing rudder pedals

  • Flight controls interim summary (Page 44)

    • RUDDER, AILERO N, ELEVATORS, THROTTLE, FLAPS, TRIM TABS, ROTARY WING CONTROLS

Flight Envelope and Performance (EB14-1/EB14-2 content)

  • The Flight Envelope (Page 45)

    • Definition: The performance envelope of an aircraft in terms of speed and altitude
    • Critical factors within the envelope include:
    • Maximum speeds
    • Stall speeds
    • Ceiling
    • Airflow regime (laminar vs turbulent)
    • Angle of Attack (AoA)

  • Rate of Climb (RoC) details (Page 46–47)

    • RoC is the vertical position increase per unit time (ft/min or m/s)
    • Vy: Speed for best RoC (least time to gain vertical position)
    • Vx: Speed for best AOC (Angle of Climb) – i.e., least distance to gain vertical position
    • Operational note: In controlled airspace London/Scottish FIRs, climb/descent rates should not exceed 8000 ft/min except in emergencies or certain military activities
    • Example dialogue: Expedite descent or climb instructions (e.g., “BIGJET 347, expedite descent FL180” or “BIGJET 347, climb FL280, expedite until passing FL180”)

  • Speed performance and category definitions (Page 34–35, 49)

    • Aircraft performance affects airspace and instrument approach procedures; five categories defined based on stall speed in landing configuration at max certified landing mass
    • Classification table (nominal ranges; speeds in IAS):
    • Category A: Less than 91 knots IAS
    • Category B: 91 knots to 120 knots IAS
    • Category C: 121 knots to 140 knots IAS
    • Category D: 141 knots to 165 knots IAS
    • Category E: 166 knots to 210 knots IAS
    • Core principle: Speed bases on stall speed (MLMA, “dirty” configuration) multiplied by 1.3 to define speed limits for approach procedures and holding patterns
    • Formula (as described): V<em>extcategory=1.3imesV</em>extstall,dirtyV<em>{ ext{category}} = 1.3 imes V</em>{ ext{stall, dirty}}

  • Stalling speed and altitude effects (Page 50)

    • Stall speed is the minimum level-flight speed
    • As altitude increases, stall speed increases (wing area remains constant; air density drops, so higher speed is needed to generate enough lift)
    • Graphically: speed vs altitude forms a diagonal line for stall speed

  • Ceiling and zero-rate-of-climb region (Page 51)

    • Ceiling: maximum altitude at which the aircraft can maintain a given speed
    • Zero-rate-of-climb region: area where altitude cannot be increased at the given speed due to lift not exceeding weight
    • Cause: Lift decreases with altitude (density and air properties) until it no longer exceeds weight

  • Aerodynamic flow regimes and boundary layer (Page 52–53)

    • Laminar (streamline) flow vs Turbulent flow
    • Boundary layer: region near the wing where flow transitions from laminar to turbulent or where separation can occur
    • Flow separation near high AoA leads to stall; designers aim to keep separation small and toward the trailing edge to maximize lift without stalling
    • Flow illustrations: examples of laminar flow on submarine hull vs turbulent flow on hull illustrate the concept

  • Wake vortex (Page 54–56)

    • Wake vortex generation by aircraft affects downstream traffic and spacing

  • Angle of Attack (AoA) (Page 57)

    • Definition: the angle between the wing’s chord line and the aircraft’s flight direction
    • AoA has a large effect on lift generated by the wing
    • As AoA increases, lift generally increases until stall occurs; beyond stall, lift decreases due to flow separation

  • Final summary (Page 58–59)

    • Key concepts to remember:
    • Flight Controls
    • Flight Envelope
    • Wake Vortex
    • Maximum Speeds
    • Stall Speeds
    • Ceiling
    • Airflow (Laminar vs Turbulent)
    • Angle of Attack

  • Key mathematical and definitional notes (embedded in the deck)

    • Lift generation: general formula commonly used in aerodynamics (not explicitly shown on the slides but relevant to lift concepts)
    • L = frac{1}{2}
      ho v^2 S C_L(oldsymbol{\alpha})
    • where: \rho is air density, v is true airspeed, S is wing area, and C_L is the lift coefficient as a function of angle of attack \boldsymbol{\alpha}
    • 1.3 rule for approach performance: V<em>extcategory=1.3imesV</em>extstall,dirtyV<em>{ ext{category}} = 1.3 imes V</em>{ ext{stall, dirty}}
    • Best Rate of Climb and Best Angle of Climb speeds:
    • VY=speed for best rate of climbV_Y = \text{speed for best rate of climb}
    • VX=speed for best angle of climbV_X = \text{speed for best angle of climb}

Notes on cross-cutting concepts and connections

  • Core idea: Lift equals the aerodynamic force supporting the weight; thrust overcomes drag to achieve motion through the air; control surfaces (rudder, elevators, ailerons) and power settings shape the flight path, attitude, and speed
  • Relationship to the flight envelope: as pilots demand higher speeds, lift needs and drag increase; the envelope defines practical limits for safe operation across speed and altitude
  • Control surfaces and trim: pilots use control surfaces to adjust attitude; trim tabs help counteract persistent control forces and stabilize flight, reducing pilot workload
  • Rotary vs fixed-wing differences: Helicopters rely on cyclic, collective, and anti-torque pedals to control rotor blade pitch and yaw, enabling flight in three dimensions with different stability considerations than fixed-wing aircraft

Quick reference: essential terms and definitions

  • Lift (L): aerodynamic force acting upward to support weight, generated by wing moving through air
  • Weight (W): gravitational force pulling toward Earth’s center
  • Drag (D): aerodynamic resistance opposing motion through air
  • Thrust (T): propulsion force moving aircraft forward to overcome drag
  • AoA (\alpha): angle between the wing’s chord line and flight direction; governs lift up to stall
  • C_L(\alpha): lift coefficient as a function of AoA (shape of lift curve)
  • V_Y: speed for best rate of climb
  • V_X: speed for best angle of climb
  • Stall speed: minimum steady flight speed; increases with altitude
  • Ceiling: maximum altitude where usable flight speed can be maintained
  • Boundary layer: thin region near wing surface where flow transitions from laminar to turbulent; flow separation leads to stall
  • Wake vortex: downwash and vortices left behind by wings that affect following aircraft
  • 1.3× stall speed rule: used to estimate approach speeds for different categories

End of notes (condensed overview of EB14-1 Theory of Flight and EB14-2 Effects of Control & Flight Envelope)