Principles of Flight

Objective:

Understand the four forces of flight and the reasons behind why an airplane flies. Explain what the flight controls are and characterize them by what they do. Create a mentality of conditions that must exist to maintain positive flight control.

Attention:

Both of you make your favorite paper airplane and throw them.
Discuss why one flies differently than the other in a very general sense.

Motivation:

By understanding why an airplane flies, the pilot will not want to do anything that interrupts the forces to remain in complete control of the aircraft. What is happening when I move this control—what is it doing?

Emphasis:

Ground effect—what it does, what not to do, left turning tendencies and maintaining positive aircraft control.

Overview:

Identify the axes of an airplane. Discuss stability and its effects on flight. Identify the flight control surfaces and what they do. Discuss the four forces of flight and some of the hazards relating to aerodynamics.


Log Ground Training:

  • 61.105(b)(10) Principles of aerodynamics, powerplants, and aircraft systems;

Aerodynamics, Principles of Flight, Flight Controls

Development:

Axes of an airplane

  • Pitching around the Lateral axis (kabobs through the wings)
  • Rolling around the Longitudinal axis (kabobs through the fuselage)
  • Yawing around the Vertical axis (flagpole through the cockpit)

Stability

  • Static stability: the initial tendency, or direction of movement, back to equilibrium
  1. Positive
  2. Neutral
  3. Negative
  • Dynamic stability: the response tendency to return to equilibrium over time
  1. Positive
  2. Neutral
  3. Negative
  • Controllability: quality of an aircraft that permits it to be maneuvered easily and to withstand the stresses imposed by maneuvers.
  • Maneuverability: the capability of an aircraft to respond to the pilot’s control, especially with regard to flightpath and attitude.
  • Longitudinal Stability (pitching)
  • Lateral stability (rolling)
  • Vertical stability(yawing)

Airplane flight controls (purpose, location, direction of movement, effect and proper procedures for its use)

  • Primary flight controls
  1. Ailerons–roll
  2. Elevator–pitch
  3. Rudder–yaw
  • Trim control(s)
  • Wing flaps

4 Forces of Flight

  1. Lift—dynamic effect of the air acting on the airfoil, perpendicular to the flightpath through the center of lift
  • Airfoil design characteristics
  • Flight occurs from a combination of many physical principles
    • Daniel Bernoulli: fluid dynamics; increased speed creates decrease in pressure
    • Newton’s third law: every action has an equal and opposite reaction
      • Faster air from above the airfoil moves downward. This action downward creates an opposite reaction upward.
  1. Weight—the combined load of the aircraft itself, the crew, the fuel, and the cargo or baggage—down through center of gravity
  2. Thrust: forward force produced by the powerplant/propeller or rotor
  3. Drag: rearward, retarding force caused by disruption of airflow by the wing, rotor, fuselage, and other protruding objects
  • Parasite drag: drag not associated with the production of lift—a hindrance of air moving over the surface of the aircraft and airfoil
    • 3 types of parasite drag
      • Form drag: aircraft’s shape and airflow around it, e.g. engine cowlings, antennas, etc.
      • Interference drag: intersections of airstreams that creates eddy currents, turbulence, or restricts smooth airflow e.g. wing meets fuselage
      • Skin friction drag: aerodynamic resistance due to the contact of moving air with the surface of an aircraft.
      • Induced drag: drag as the direct result of lift—friction of high pressure air meeting low pressure air around an airfoil
  • In steady straight flight, the sum of all the opposing forces (lift to weight, and thrust to drag) is zero i.e. Lift doesn’t equal drag

Wingtip vortices and precautions to be taken—wake turbulence

  • Landing behind a large aircraft
  • Takeoff behind a large aircraft

Ground Effect

  • Reduced drag gives the perceptible illusion of greater lift
  • Helps smooth a landing if used properly
  • Do not pull out of ground effect too early

Turning tendency (toque effect)

  • Corkscrew effect
  • Gyroscopic action
  • P-factor
  1. The “bite” of the downward moving blade is greater than the “bite” of the upward moving blade.

Stalls and angle of attack overview

 
Aircraft Systems

  • Discuss the following systems in the aircraft to be flown
  • Airframe
  • Controls
  • Engine
  • Oil
  • Fuel
  • Electric
  • Etc.

Conclusion and Evaluation:

Remember what is needed to maintain lift and positive aircraft control and never disrupt these forces when you want to maintain flight.