# Lesson 2-2a Principles of Flight

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Lesson 2-2a Principles of Flight

The Forces of Flight

How many forces are present when an aircraft is cruising at constant speed and altitude? a. 0 b. 2 c. 4 d. 6 Chapter 1, Lesson 2

Lift Lift is produced almost entirely by moving air over and under the wings The profile of a wing is called an airfoil Changing the airflow on the surface of the airfoil (or wing) will increase or decrease the amount of lift

Bernoulli’s Principle
Faster airflow causes a decrease in air pressure Air flowing over the curved upper surface of a wing speeds up Increase in speed reduces pressure above the wing and produces the upward lifting force

Airfoils Can be wings or propeller blades
Parts of airfoil Include leading and trailing edges, camber and chord line

Wind Tunnels, cont. The Wright Brothers tested more than 200 wing shapes in a tunnel before the successful glider Researchers can carefully control airflow conditions and measure the forces on an aircraft model

Activity Bernoulli’s Principle in Action
Let’s do a quick experiment to demonstrate Bernoulli’s Principle in action using a funnel and a ping-pong ball

Effect of Angle of Attack on Flight
If a plane alters pitch—the up and down movement of the plane’s nose—the angle of attack on its wings will change As angle of attack increases, wings generate more lifting force

Critical Angle of Attack
Point at which a plane stalls—around 15⁰ Chapter 1, Lesson 1 Reproduced from NASA/Glenn Research Center

How Lift is Generated Air flows over top of wing reducing pressure on top surface relative to bottom surface of wing Lift depends on aircraft’s shape, size, and velocity To increase lift: Increase aircraft’s forward speed Increase airfoil’s angle of attack (up to stall angle) Increase surface area of airfoil Chapter 1, Lesson 2 Reproduced from NASA/Glenn Research Center

Airfoil Camber The curve in an airfoil is the camber
In most airfoils the upper surface curves more than the lower surface Airfoil’s thickness is the maximum distance between the upper and lower wing surfaces

Airfoil Types, Purpose, and Function
Aircraft weight, speed, and purpose determine wing’s shape Streamlined airfoils don’t create enough lift Teardrop shaped airfoils have no lift at zero angle of attack

Airfoil Types, Purpose, and Function
See handout of conventional airfoils

The Fuselage The fuselage is the aircraft body
Fuselage vary in shape to fit the mission Fuselage must be strong enough to withstand torque Chapter 1, Lesson 3 Courtesy of USAF/CMSgt Gary Emery

Wing Position and Parts
Wing position depends on aircraft’s mission Main internal parts are spars, ribs and stringers Fuel tanks usually part of wing Chapter 1, Lesson 3 Reproduced from US Department of Transportation/Federal Aviation Administration

Wing Angles Dihedral angles give aircraft roll stability and level flight Large commercial airliner wings have dihedral angles Fighter aircraft have anhedral angles Chapter 1, Lesson 3 Modified from NASA/Glenn Research Center

The Role of Stabilizers and Rudders
Stabilizers are on the aircraft’s tail Stabilizers keep aircraft stable so it can maintain straight flight path Vertical stabilizer prevents the nose of plane from roving side to size Horizontal stabilizer keeps plane from bobbing up and down

The Role of Stabilizers and Rudders, cont.
Rudder is the hinged piece on the vertical stabilizer Lets pilot steer the aircraft by moving the tail left or right Elevators are the hinged flaps on the horizontal stabilizer Lets pilot steer the aircraft by moving the tail up or down

The Positions of Flaps, Spoilers, and Slats on Aircraft
Flaps are hinged device at wing’s trailing edge that produces lift Spoiler is small, flat plate that attaches the tops of wings; it increases drag Slat is moveable, hinged parts that pivot down to generate more force

Primary and Secondary Controls
Primary Controls make aircraft controllable and safe to fly Rudders, elevators, and ailerons Secondary controls let the pilot maintain more control over aircraft’s performance Flaps, slats, and spoilers

Primary Flight Controls
Pilot uses primary flight controls to control aircraft yaw, pitch, and roll Rudders control yaw or side-to-side motion of aircraft Elevators control pitch or up and down motion of aircraft Ailerons control roll or banking of the wings

How Ailerons Work Aileron is a small hinged section on the outboard portion of each wing Ailerons operate in opposite direction on the wings, causing one to increase lift (point aileron down), one to decrease lift (point aileron up)

Secondary Flight Controls
Used primarily in more challenging flight conditions where low speeds are required (take-off and landing) Flaps are on trailing edge of wings and increase/decrease lift and drag on both wings at the same time Slats are on the leading edge of the wings and also increase/decrease lift and drag on both wings at the same time Spoilers reduce lift and increase drag and can be used on both wings at same time or on one wing and not the other

Spoilers Spoilers are small, flat plates that attach to the tops of the wings with hinges Raising spoilers on both wings slows aircraft in any phase of flight Raising spoilers on only one wing causes a rolling motion

Activity: Airplane Parts and Functions
Label the airplane parts Define their function in flight