What is Flight-Simply Speaking #2

The first “What is Flight” article introduced the concept of a liquid, such as air, when moving faster over the curved top of a wing generate less pressure or a vacuum, theBernoulli Principal. In this article we discuss the parts of a very simple fixed wing aircraft. The physics of a simple aircraft apply to the most advanced 747 but, in a smaller scale.

So far, we have a fuselage with wings that pull or lift the aircraft up, a propeller to pull the aircraft forward and, stabilizers at the back or tail of the aircraft to keep our aircraft flying straight like feathers do for an arrow.

Now, how does the aircraft turn, climb and descend? Each wing has an aileron that is controlled by the pilot. For a left turn the pilot moves the yoke or stick toward the left and the left aileron moves up into the airflow, disrupting the flow and reducing the lift while the right aileron moves down, increasing the curvature of the wing top and increasing the lift. Right wing moves up and left wing moves down, and the aircraft turns left. Simple enough except, another law of physics from Isaac Newton complicates the maneuver. “For every action there is an equal and opposite reaction”, so as the right wing generates more lift it also generates more drag on that wing resulting in a yaw or sideways force. The nose of the aircraft moves up and to the right. The pilot then uses a panel attached to the vertical stabilizer to move the nose left to coordinate the turn. His rudder pedals at his feet move the rudder disrupting the flow of air, in this case toward the left counteracting the right yaw from the aileron movements. What happened to “Flight-Simply Speaking? “

The opposition force of drag causes the aircraft to slow and descent unless the pilot uses another control by pulling back on his yoke or stick which activates another panel attached to the horizontal stabilizer called the elevator. It raises up into the airflow, forcing a downward force on the tail and an upward movement for the nose. Finally, a coordinated turn to the left has been accomplished but with the increased drag the aircraft will slow and eventually ‘stall’ or quit flying unless the pilot increases an opposite force to the drag called thrust.

An aircraft deals with three axes; vertical or yaw, longitudinal or roll, and lateral or pitch. Our wing has ailerons to generate a turn and the vertical and horizontal stabilizers have a rudder and an elevator to coordinate the turn.

Our next article will discuss the several forms of thrust, without which we could never get airborne and wing flaps that increase the lift of a wing to allow shorter take offs and slower landings. The pilot is much like a conductor of an orchestra. His players are thrust, ailerons, elevator, rudder and a few other players that we will discuss in future articles.


Art Krull                                                           

FoF Volunteer Ambassador

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