27 January 2021 at 3:58 pm #4010
EO Number and Title
231.02 THE PRODUCTION OF LIFT
WHAT: HOW LIFT IS PRODUCED IN AN AIRCRAFT
WHEN AND WHY ANYTHING AVIATION RELATED AND WE ARE AIR CADETS SO YEAH
BE QUICK WITH THIS
TEACHING POINT 1 AND 2
5 MIN EACH
TP1 AIR IS A FLUID
EXPLAIN IT LIKE IT WAS WATER
NEWTON’S FIRST LAW SAYS THAT AIR IS A FLUID AND IT REMAINS IN MOTION WHEN IN MOTION
NEWTON’S SECOND LAW SAYS THAT TO MOVE SOMETHING SOMETHING HAS TO MOVE IT
NEWTON’S THIRD LAW SAYS THAT EVERY FORCE HAS AN EQUAL AND OPPOSITE FORCE
THAT THIRD FORCE MAKES IT POSSIBLE TO FLY BECAUSE WE APPLY A FORCE TO THE AIR IT CREATES AN EQUAL AND OPPOSITE REACTION AND WITH HAVING A LOWER PRESSURE ON TOP AND A HEAVIER PRESSURE ON THE BOTTOM YOU CAN MOVE UP
TP2 BERNOULLI’S PRINCIPLE
To develop the equal and opposite reaction described by Newton’s third law of motion, the wing is given a shape that takes advantage of Bernoulli’s Principle to make the air change direction. Air behaves like a fluid since it has pressure and speed. As airspeed increases, its pressure drops. A wing uses Bernoulli’s Principle to deflect air, which causes an equal and opposite reaction.
DRAW A PICTURE OF A WING AND HOW IT MAKES HIGH AND LOW PRESSURE
Q1. How does air follow Newton’s first law of motion?
Q2. How does air follow Newton’s second law of motion? Q3. How does air follow Newton’s third law of motion?
A1. When in motion, air tends to remain in motion.
A2. When in motion, a force must be applied to change air’s motion.
A3. When air’s motion is changed, an equal and opposite reaction results.
TAKE TIME WITH THIS
Q1. What relationship exists between air speed and air pressure?
Q2. What is the wing’s connection between Newton’s third law and Bernoulli’s Principle? Q3. What is a wing’s shape calculated to do?
A1. An inverse relationship: as speed increases, pressure drops and as speed drops, pressure increases.
A2. A wing uses Bernoulli’s Principle to deflect air, which causes an equal and opposite reaction.
A3. A wing’s shape is calculated to decrease pressure above while increasing pressure below.
TEACHING POINT 3
The pressure of moving air can be examined by blowing gently over a small piece of curved paper. The air does not push the paper down as might be intuitively assumed. Instead, the paper behind the curve rises toward the moving air. This happens because the air pressure drops over the paper due to the air’s increased speed – this would seem to match the description of speed/pressure relationship. The curvature in the paper enhances the effect of the lowered air pressure. A similar effect can be observed when air moves past any object that is light enough to be affected by the drop in air pressure associated with movement. A balloon is light enough to show this effect clearly
NEED TWO BALLOONS AND HAVE THE CADETS BLOW IN BETWEEN THEM AND THEY SHOULD MOVE TOWARDS EACHOTHER. THIS IS BECAUSE YOU HAVE FASTER AIR ON THE ONE SIDE THAT THE OTHER LIKE A WING
TEACHING POINT 4
An aircraft wing is an airfoil because of its cross-sectional shape. The top surface is curved outward (convex curvature). Therefore, the air flowing over the top has further to go, over the curve, and so it must move faster which, as we know, will result in lower pressure. This happens above the wing. Below the wing, the air is deliberately slowed to increase its pressure. This is done by curving the surface slightly inward (concave curvature) and by sloping the wing so that it is slightly higher at the front (leading edge) than it is at the back (trailing edge). This angle of the wing’s under-surface, which encounters the moving air, is called the wing’s angle of attack. Use a model aircraft to demonstrate to the cadets that the wing’s angle of attack increases when the aircraft’s nose is raised during flight. The greater the wing’s angle of attack, the more air the under-surface of the wing will encounter, thereby generating more lift. This is a direct relationship between angle of attack and lift. Increasing the wing’s speed will also cause it to encounter more air, thereby generating more lift. This is also a direct relationship between speed and lift. There is a limit to the amount of lift that can be produced by merely increasing the angle of attack. Long before the wing becomes vertical, it stops generating lift above and this often happens abruptly. The wing “stalls” and stops generating lift when this happens.
Q1. Which surface of an aircraft wing is curved outward (convex)?
Q2. What shape is often given to the underside of an aircraft wing?
Q3. What happens to air pressure under a wing as angle of attack increases?
A1. The top surface of a wing is curved outward. A2. A slight inward, or concave, curve is often given to an aircraft wing. A3. The pressure increases as angle of attack increases.
END OF LESSON CONFIRMATION
THEIR END OF LESSON CONFIRMATION WILL BE TO MAKE THE BEST PAPER AEROPLANE THEY CAN AND THROW IT AND THE WINNER WILL GET SOMETHING FROM CANTEEN THE NEXT WEEK
SPLIT TIME REMAINING INTO HALF AND GIVE THEM HALF THE TIME TO MAKE AND TEST AND THE OTHER HALF TO COMPETE
Lesson Summary: 4 FORCES THAT ACT UPON AN AIRCRAFT
Your next lesson will be next week with components of a piston powered internal combustion engine with fsgt wohlgemuth
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