Raymond W. Brooks
To understand flight, we must first understand three basic things about airplanes.
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1. The major parts and the function of each of these parts.
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2. The forces that act on the aircraft.
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3. How to control the aircraft.
A. THE MAJOR PARTS OF OF THE AIRPLANE
The airplane is divided into 5 major parts.
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1. fuselage
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2. wing
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3. engine
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4. tail section
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5. landing gear
Fig. 4-1.
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Fig. 4-2.
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Fig. 4-3.
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Fig. 4-4.
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Fig. 4-5.
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The fuselage contains the cockpit and flight controls, the passenger compartment, and all major parts of the airplane are connected to the fuselage.
The wings are the devices that provide lift for the airplane and contain the ailerons which are used to change the direction of flight. Wings come in various shapes and sizes.
The engine is the vehicle that provides the thrust for the airplane. The engine can be propeller driven, a device that bites into the air causing the plane to thrust forward, or jet powered, compresses air and forces it out the rear opening at a higher rate of speed.
The tail section gives the airplane directional stability by the vertical stabilizer, (rudder) and the horizontal stabilizer. (elevators)
The landing gear is important not only for landing the aircraft safely, but also to get the aircraft into the air. The landing gear can be fixed in place or it may be retractable into the fuselage. In most cases, the retractable is more desirable as it reduces drag on the airplane and is less likely to be exposed to hazards in flight. The flaps, which are located on the wings, also aid the aircraft in landings and take-offs.
B. FORCES ACTING ON THE AIRPLANE IN FLIGHT
There are four major forces acting on an airplane in level flight at constant speed. They are lift, gravity, thrust, and drag.
Fig. 4-6.
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In order to lift the airplane into the air, we must overcome the force of gravity. This is accomplished by having the wing shaped in such a way that a low pressure area is created at the top of the wing by air moving faster over the top than across the bottom of the wing. This unequal pressure causes the wing to move up to fill this area of lower pressure. The angle of the wing and speed of moving air will determine the amount of lift.
Near the end of a class period have the students blow across a piece of paper and have them observe what happens to the piece of paper. Do not say anything at this time. Ask if anyone would like to blow a ping-pong ball out of an upright funnel. After trying to do this tell them you will help them out by inverting the funnel and again ask for volunteers. Upon completing this activity have them do a homework assignment on “Bernoulli Principle.” Discuss this principle the next day and how it relates to an airplane. Explain that some books try to use this as an explanation for flight but, this does not explain flight otherwise how could an airplane fly upside down? Briefly explain that it is a circulation pattern around the wing that causes lift. A good explanation can be found in “What Makes Airplanes Fly.”
Gravity is the force that tends to pull all matter toward the center of the earth. This force must be overcome before the aircraft can become airborne. An aerodynamically designed craft will make this task a little easier.
Thrust is what causes an airplane to move forward. The faster the engine causes air to move, the faster the aircraft will travel.
Drag is the opposite of thrust and is caused by the resistance of the airplane. Again aerodynamics plays an important part in reducing drag by streamlining the airplane to let the plane operate more efficiently.
Newton’s Laws can be discussed at this time and explained how they relate to flight. A good way to start the discussions is to use a ballistics car. Start by showing what happens to the ball when the car is at rest. Now put the car into motion and observe what happens to the ball. Ask how many students have ever heard of Sir Isaac Newton. Have them do a homework assignment on Newton telling where he lived, when he lived, and a brief explanation of his three laws.
Discussion of this assignment could begin with defining “inertia.” Discuss what value seat belts are to people in automobiles by talking about what forces act on a person in the car from starting to moving to stopping and running into a tree.
We could discuss why the more massive a plane the more fuel it will use to operate. F = ma
Blow up a balloon and let it go. Ask students why the balloon behaved as it did. Newton’s action—reaction
If you have access to Physical Science Software by Prentice-Hall you will find the following disks very helpful.
NEWTON’S FIRST LAW
Students begin by seeing examples that illustrate the law of inertia. Then they examine forces that affect motion, and control and measure these forces and their effects on the object involved. Such interaction allow for an understanding of motion in terms of analysis of position and velocity. Finally, students analyze and apply Newton’s First Law.
NEWTON’S SECOND LAW
In this product, students explore the mathematical relationship between force, mass, and acceleration. By analyzing and measuring velocity and acceleration, they discover how various quantities in Newton’s Second Law of Motion are affected when the values of this other quantities are changed. Students also carry out rearrangement of the equation. By doing so, they learn how to handle the units involved in the expression of force, mass, and acceleration.
NEWTON’S THIRD LAW
After students generate, monitor and measure action and reaction forces, they compare the magnitudes of the forces and motions involved and investigate net force. They then discover the relationship between the mass-velocity products of two objects that are acting upon one another. In this way they discover the nature of momentum and the role of this quantity in action-reaction situations.
C. CONTROL OF THE AIRPLANE
The control surfaces of an airplane are found on the wings, horizontal stabilizer, and vertical stabilizer. These control surfaces control the three axes of movement. Pitch, roll, and yaw.
Fig. 4-7.
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Pitch is the rise and fall of the airplane. The elevators on the horizontal stabilizer will control this movement. A fun activity is to have the student make a paper airplane to test how the elevators control the rise and fall of an airplane.
Fig. 4-8.
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The roll of an airplane is controlled by the ailerons. These work opposite each other meaning when one aileron is in the up position the other is in the down position which causes the airplane to roll left or right depending on which is up or down position.
The yaw of the airplane, side to side motion, is controlled by the rudder which is located on the vertical stabilizer. This is used to make minor adjustments as “skidding” takes place if major adjustments are to be made so the use of the ailerons are more effective.
Now that we know how to get the airplane into the air and we are able to control the flight path so that we can go where we wish to travel, what else should we know?