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THE PRINCIPALS OF THE PRINCIPALS OF FLIGHT OF FLIGHT OF AN AEROPLANEAN AEROPLANE

PRESENTATION BY PRESENTATION BY

MR. NIKHIL D. PISEMR. NIKHIL D. PISE

• Aeroplanes fly because of a physical Aeroplanes fly because of a physical principal discovered by a Dutch scientist principal discovered by a Dutch scientist named Daniel Bernoulli (1700 - 1782).named Daniel Bernoulli (1700 - 1782).

• BERNOULLI’s PRINCIPALBERNOULLI’s PRINCIPAL:: This principal says that as the speed This principal says that as the speed

(velocity V) of a fluid increases, its (velocity V) of a fluid increases, its pressure (P) decreases. Since the flow of pressure (P) decreases. Since the flow of air over an airplane wing acts like a air over an airplane wing acts like a fluid, the principal applies.  fluid, the principal applies.  

  

• The Shape of Airplane Wings:The Shape of Airplane Wings:

    Airplane wings, like birds' wings, are Airplane wings, like birds' wings, are curved on top and flat on the curved on top and flat on the bottom.There is an old saying that you bottom.There is an old saying that you might have heard: "The shortest might have heard: "The shortest distance between two point is a straight distance between two point is a straight line." If the bottom of the wing is flat line." If the bottom of the wing is flat (straight) while the top of the wing (straight) while the top of the wing curves up and then back down, then the curves up and then back down, then the length of the line on the top of the wing length of the line on the top of the wing is longer than the line on the bottom.is longer than the line on the bottom.

A Tale of Two MoleculesA Tale of Two Molecules  • Let us take a look at two air molecules, one Let us take a look at two air molecules, one

traveling on the top side of the wing (Mtop), and the traveling on the top side of the wing (Mtop), and the other traveling on the bottom side of the wing other traveling on the bottom side of the wing (Mbottom). There are other air molecules all around (Mbottom). There are other air molecules all around our two molecules, so they must move along the our two molecules, so they must move along the wing.wing.

  • They will start at the tip of the wing, and meet at They will start at the tip of the wing, and meet at

the back (or trailing edge) of the wing. They must the back (or trailing edge) of the wing. They must both get to the back of the wing at the same time. both get to the back of the wing at the same time. Since the top surface of the wing is longer than the Since the top surface of the wing is longer than the bottom surface because of the curve, the molecule bottom surface because of the curve, the molecule on the top must travel faster than the molecule on on the top must travel faster than the molecule on the bottom.the bottom.

  

• According to Bernoulli's Principal, as the According to Bernoulli's Principal, as the molecule on top goes faster (velocity molecule on top goes faster (velocity increases) then its pressure decreases. increases) then its pressure decreases. Therefore, the pressure on the bottom of Therefore, the pressure on the bottom of the wing is greater than the pressure on the the wing is greater than the pressure on the top of the wing. This difference in pressure top of the wing. This difference in pressure causes the wing to move up. This is called causes the wing to move up. This is called the Bernoulli Effect. With airplanes, this the Bernoulli Effect. With airplanes, this upward movement is called Lift. The faster upward movement is called Lift. The faster the airplane goes through the air, the airplane goes through the air, the greater is the lift generated by the air the greater is the lift generated by the air flowing over the wings. flowing over the wings.

  

What Makes the Airplane Move What Makes the Airplane Move Forward?Forward?There are two basic types of airplanes – There are two basic types of airplanes –

1.Propeller driven planes and 2.Jet planes. 1.Propeller driven planes and 2.Jet planes.

  

• Propeller Driven PlanesPropeller Driven Planes - Propeller - Propeller driven airplanes use a propeller that is driven airplanes use a propeller that is turned by some type of engine. turned by some type of engine. Propellers also depend on Bernoulli's Propellers also depend on Bernoulli's Principal to function. They are shaped Principal to function. They are shaped just like the wings, and also generate just like the wings, and also generate lift, except that the lift is forward lift, except that the lift is forward instead of up and is called thrust. instead of up and is called thrust. Each propeller is made up of two or Each propeller is made up of two or more blades. more blades.

• Jet PlanesJet Planes - Jet planes do not have - Jet planes do not have propellers. Instead, they have jet propellers. Instead, they have jet engines that move the airplane forward engines that move the airplane forward through another physical principal through another physical principal discovered by Sir Isaac Newton (1642 - discovered by Sir Isaac Newton (1642 - 1727). This is Newton's Third Law of 1727). This is Newton's Third Law of Motion - "For every action there is an Motion - "For every action there is an equal and opposite reaction." equal and opposite reaction."

• You can think of a jet engine as a tube You can think of a jet engine as a tube in which a liquid fuel (like the fuel diesel in which a liquid fuel (like the fuel diesel truck use) is burned at high pressure truck use) is burned at high pressure with air from a compresser. The with air from a compresser. The resulting heat forces the gases out of resulting heat forces the gases out of the back of the tube at high speed. In the back of the tube at high speed. In accordance with Newton's Law, an equal accordance with Newton's Law, an equal force is applied in the forward direction, force is applied in the forward direction, moving the engine (and the plane it is moving the engine (and the plane it is attached to) forward .attached to) forward .

•       LANGLEY'S LAWLANGLEY'S LAW -- The law -- The law enunciated by Langley is, that the enunciated by Langley is, that the greater the speed the less the power greater the speed the less the power required to propel it. Water as a required to propel it. Water as a propelling medium has over seven propelling medium has over seven hundred times more force than air. A hundred times more force than air. A vessel having, for instance, twenty vessel having, for instance, twenty horse power, and a speed of ten miles horse power, and a speed of ten miles per hour, would require four times per hour, would require four times that power to drive it through the that power to drive it through the water at double the speed. The power water at double the speed. The power is as the square of the speed. is as the square of the speed.

• THEORIES AND FACTS ABOUT FLYINGTHEORIES AND FACTS ABOUT FLYING

•       THE "SCIENCE" OF AVIATIONTHE "SCIENCE" OF AVIATION.. -- It may -- It may be doubted whether there is such a thing be doubted whether there is such a thing as a "science of aviation." Since Langley, as a "science of aviation." Since Langley, on May 6, 1896, flew a motor-propelled on May 6, 1896, flew a motor-propelled tandem monoplane for a minute and an tandem monoplane for a minute and an half, without a pilot, and the Wright half, without a pilot, and the Wright Brothers in 1903 succeeded in flying a bi-Brothers in 1903 succeeded in flying a bi-plane with a pilot aboard, the universal plane with a pilot aboard, the universal opinion has been, that flying machines, to opinion has been, that flying machines, to be successful, must follow the structural be successful, must follow the structural form of birds, and that shape has form of birds, and that shape has everything to do with flying. everything to do with flying.

•       MOMENTUM A FACTORMOMENTUM A FACTOR.. -- Each had -- Each had transferred to it a motion. The initial transferred to it a motion. The initial speed was the same, and the power speed was the same, and the power set up equal in the two. Why this set up equal in the two. Why this difference, the answer is, that it is in difference, the answer is, that it is in itself. It was the mass or density which itself. It was the mass or density which accounted for the difference. It was accounted for the difference. It was mass multiplied by speed which gave mass multiplied by speed which gave it the power, called, in this case, it the power, called, in this case, momentum. momentum.

•       We have two balls the same We have two balls the same diameter, one of iron weighing a half diameter, one of iron weighing a half pound, and the other of cotton pound, and the other of cotton weighing a half ounce. The weight of weighing a half ounce. The weight of one is, therefore, sixteen times greater one is, therefore, sixteen times greater than the other. than the other.

       Suppose these two balls are thrown Suppose these two balls are thrown with the expenditure of the same with the expenditure of the same power. What will be the result! The power. What will be the result! The iron ball will go much farther, or, if iron ball will go much farther, or, if projected against a wall will strike a projected against a wall will strike a harder blow than the cotton ball. harder blow than the cotton ball.

•     RESISTANCERESISTANCE. -- Now, in the . -- Now, in the movement of any body through space, movement of any body through space, it meets with an enemy at every step, it meets with an enemy at every step, and that is air resistance. This is much and that is air resistance. This is much more effective against the cotton than more effective against the cotton than the iron ball: or, it might be expressed the iron ball: or, it might be expressed in another way: The momentum, or in another way: The momentum, or the power, residing in the metal ball, is the power, residing in the metal ball, is so much greater than that within the so much greater than that within the cotton ball that it travels farther, or cotton ball that it travels farther, or strikes a more effective blow on strikes a more effective blow on impact with the wall. impact with the wall.

•       HOW RESISTANCE AFFECTS THE SHAPE.HOW RESISTANCE AFFECTS THE SHAPE. -- It is because of this counterforce, -- It is because of this counterforce, resistance, that shape becomes important resistance, that shape becomes important in a flying object. The metal ball may be in a flying object. The metal ball may be flattened out into a thin disk, and now, flattened out into a thin disk, and now, when the same force is applied, to project when the same force is applied, to project it forwardly, it will go as much farther as it forwardly, it will go as much farther as the difference in the air impact against the the difference in the air impact against the two forms. two forms.

• THE LIFTING SURFACES OF AEROPLANESTHE LIFTING SURFACES OF AEROPLANES

      This subject includes the form, shape This subject includes the form, shape and angle of planes, used in flight. It is and angle of planes, used in flight. It is the direction in which most of the energy the direction in which most of the energy has been expended in developing has been expended in developing machines, and the true form is still machines, and the true form is still involved in doubt and uncertainty. involved in doubt and uncertainty.

• LIFT AND DRIFTLIFT AND DRIFT. -- The terms should be . -- The terms should be explained, in view of the frequent allusion explained, in view of the frequent allusion which will be made to the terms which will be made to the terms hereinafter. Lift is the word employed to hereinafter. Lift is the word employed to indicate the amount which a plane surface indicate the amount which a plane surface will support while in flight. Drift is the term will support while in flight. Drift is the term used to indicate the resistance which is used to indicate the resistance which is offered to a plane moving forwardly against offered to a plane moving forwardly against the atmosphere. the plane A is assumed to the atmosphere. the plane A is assumed to be moving forwardly in the direction of the be moving forwardly in the direction of the arrow B. This indicates the resistance. The arrow B. This indicates the resistance. The vertical arrow C shows the direction of lift, vertical arrow C shows the direction of lift, which is the weight held up by the plane. which is the weight held up by the plane.

•   NARROW PLATES MOST EFFECTIVENARROW PLATES MOST EFFECTIVE. . -- It was learned, in the early stages -- It was learned, in the early stages of the development by practical of the development by practical experiments, that a narrow plane, experiments, that a narrow plane, fore and aft, produces a greater lift fore and aft, produces a greater lift than a wide one, so that, assuming than a wide one, so that, assuming the plane has 100 square feet of the plane has 100 square feet of sustaining surface, it is far better to sustaining surface, it is far better to make the shape five feet by twenty make the shape five feet by twenty than ten by ten. than ten by ten.

•       However, it must be observed, that However, it must be observed, that to use the narrow blade effectively, it to use the narrow blade effectively, it must be projected through the air must be projected through the air with the long margin forwardlywith the long margin forwardly

• Its sustaining power per square foot Its sustaining power per square foot of surface is much less if forced of surface is much less if forced through the air lengthwise. through the air lengthwise.

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