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TOPIC B: FLIGHT


SLE1 How can you improve the design of a model parachute based upon tests performed in the classroom?


Parachutes A parachute works to slow down someone, or something, from falling by creating “drag”. When an object moves or falls through air, it has to push the air molecules out of the way. This creates a resistance force, or drag, on the moving object. Since air is much thinner than water, air doesn’t have as much drag as water. The bigger something is (that is, the larger its surface area), the more drag it creates. That’s why a parachute works so well-it is very light and it has a very big surface area. It catches lots of air, creating lots of drag, which slows it down at it falls.


Parachutes The first real parachute was invented in the 1780s. Parachutes have been used to slow down the descent of people and things ever since. Huge parachutes are used to slow down the fall of rockets and space shuttles when they re-enter Earth’s atmosphere.


Parachutes What do you think might happen if you release a parachute with an object from a higher point? A lower point? *When released from a higher point, the falling time will be longer. *When released from a lower point, the falling time will be shorter. In some cases, the falling time will be very short because the parachute will not have time to open fully. When you conduct tests of a model parachute, experiment using different variables:      

– other parachute material – other sizes of parachute material – longer and shorter strings – heavier and lighter strings – objects of different weights – different dropping heights

What is the best design?


SLE2 How are rising and falling controlled in the design of a hot-air balloon?


Hot-Air Balloons 

The hot air balloon is the oldest successful human-carrying flight technology.

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Based on a very basic scientific principle: warmer air rises in cooler air. Since hot air is lighter than cool air, it has less mass. A hot-air balloon rises because it is filled with hot, less dense air and is surrounded by colder, denser air.

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A hot-air balloon has three essential parts: the burner, which heats the air; the balloon envelope, which holds the air; and the basket, which carries the passengers.


Hot-Air Balloons 

The burners in the modern hot-air balloons heat the air by burning propane, the same substance commonly used in outdoor cooking grills. The propane is stored in compressed liquid form, in lightweight cylinders positioned in the balloon basket.

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The heated air inside the envelope makes it buoyant since it has a lower density than the relatively cold air outside the envelope. Unlike gas balloons, the envelope does not have to be sealed at the bottom since the rising hot air only exerts pressure on the upper hemisphere of the balloon to provide lift.

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The envelope is generally made from nylon fabric and the mouth of the balloon (closest to the burner flame) is made from fire resistant material such as Nomex.


Hot-Air Balloons 

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To lift the balloon, the pilot moves a control that opens up the propane valve. This lever works just like the knobs on a gas grill or stove; as you turn it, the flow of gas increased, so the flame grows in size. The pilot can increase speed by blasting a larger flame to heat the air more rapidly. Hot-air balloons also have a flap at the top of the envelope to let air out. To let some of the warm air escape out of the top flap, the pilot pulls on a cord to open the flap. This causes the balloon to descend. If the pilot keeps the valve open long enough, the balloon will sink. Pilots can only move hot-air balloons up and down. To move in a particular direction, a pilot ascends and descends to the appropriate level and rides with the wind. Since wind speed generally increases as you get higher in the atmosphere, pilots can also control speed by changing altitude.


SLE3 What glider design goes further, stays up longer or flies in a desired way?


Gliders  

Gliders are aircraft with no attached power source Model gliders are usually hand-launched or catapultlaunched (using an elastic bungee) There are many factors that come in to being when you attempt to design your own glider. Consider the shape of the wing and the control surfaces on the glider (rudder, elevator and ailerons) These work together to provide directional control for the plane by altering the airflow around the surfaces of the plane


Shape and Size of Wing


Shape and Size of Wing An airfoil shape is used to give the greatest lift possible to an airplane.


Glider Designs The wing shape that would produce the most lift?


Glider Designs What wing design would produce the most lift?


Altering Control Surfaces


Glider Tests Make predictions about how your gilder will move or turn when the control surfaces are set in the positions below: Control Surfaces

Predicted Flight

Rudder

Elevator

Right Aileron

Left Aileron

Left

Up

Down

Up

Right

Up

Down

Up

Left

Down

Up

Down

Right

Down

Up

Down

Left

Straight

Down

Up

Actual Flight


Glider Designs To get the paper airplane to bank to the left on its next flight, you should fold a flap down/up on its right/left wing and up/down on its right/left wing


SLE4 What are the major components of an airplane and their control surfaces?


Major Components of an Aircraft An aircraft is made up of several different parts that enable a pilot to have a successful flight. The main body of the plane is called the fuselage.


Control Surfaces of an Aircraft


Ailerons

Flaps are the part of the airplane that can be adjusted to increase the curvature of the wings to create more lift. Hinged flaps on the trailing edge of an aircraft’s main wing are called ailerons. These are used to make the airplane bank left or right, which is called “roll�. Ailerons control roll. If the left aileron is raised and the right one lowered, the air moving over the upper surface of the left wing is slowed, thereby increasing the air pressure. As a result, the plane banks to the left.


Elevators Two smaller flaps on the plane’s tail can be moved up or down. They are called elevators. They are attached to the horizontal stabilizers. Elevators are used to control pitch. Pitch is the upward or downward movement of the plane. With the elevators down, lift on the tail is increased and the nose drops. With the elevators up, lift on the nose is increased; the tail goes down and the nose rises.


Rudder

The flap attached to the tail of the wing on the vertical stabilizer is called the rudder. The rudder allows the pilot to change direction from left to right. This is called “yaw�. If the rudder is turned to the left, the nose of the plane turns left. If the rudder is turned to the right, the nose of the plane turns right. Pilots use both the ailerons and the rudder to turn the plane.


SLE5 Why is it important to control the flight and stability of an aircraft?


Flight of An Aircraft Four Forces of Flight Lift - upward Drag - down and backward Weight - downward Thrust - forward


Flight of An Aircraft In order for a plane to lift off, the four forces of flight must be balanced. If lift is greater than weight, the plane goes up. If lift and weight are equal, the aircraft continues in level flight. If weight is greater than lift, the plane goes down. The pilot must use the engines to move forward to provide thrust. Once there is enough thrust, the speed requirement will be met for lift. The force acting opposite to thrust is drag, the resistance of air on the plane’s wings and body. If thrust is greater than drag, the plane moves forward. If drag is greater than thrust, the plane slows down.


Stability An airplane in flight is constantly subjected to forces that disturb it from its normal horizontal flight path. Rising columns of hot air, down drafts gusty winds, etc., make the air bumpy and the airplane is thrown off its course. Its nose or tail drops or one wing dips. How the airplane reacts to such a disturbance from its flight attitude depends on its stability characteristics. Stability is the tendency of an airplane in flight to remain in straight, level, upright flight and to return to this attitude, if displaced, without corrective action by the pilot.


Stability of An Aircraft Control surfaces provide stability which is the ability of an airplane to control movement (pitch, roll and yaw) in order to maintain altitude despite air turbulence.


SLE6 What devices are used for propelling a model aircraft and how do they work?


SLE6 One of the problems with most aircraft is that they are quite large and cannot hover in one place. They must be moving forward all the time in order to achieve lift. This is not the case for helicopters. Helicopters are designed with a giant horizontal propeller, known as a rotor, which spins around very quickly. Each of the long thin blades of the rotor is the shape of an airfoil. These blades cut through the air at high speeds and provide the helicopter with lift.


Helicopters


Helicopters


SLE6 Lift can be generated while the helicopter is going straight up, hovering, flying forward, or flying backward. To move in these different directions, all the pilot has to do is tilt the rotor slightly in the direction he or she wants to go. The four forces of flight still apply to the movement of the helicopter.


SLE7 What are the differences between aircraft and spacecraft? Why would they be different?


Differences Between Aircraft and Spacecraft Since there is no air in space, aircraft and spacecraft have many design differences. The first difference is how they achieve lift. An aircraft achieves lift by first generating thrust, which creates enough speed to achieve lift. Spacecraft generate thrust to lift-off through two large rocket boosters and three main engines. The engines burn liquid oxygen and hydrogen. The fuel for the engines is stored in a large tank attached to the shuttle. After lift-off, the fuel tank is detached from the shuttle. With the help of a large parachute, it lands safely in the ocean where it is picked up.


Differences Between Aircraft and Spacecraft Shuttles are designed to meet the environmental needs of the astronauts on board. Astronauts need air to breathe, food to eat, water to drink, and a warm temperature. When the shuttle is ready to come back to Earth, it must come through Earth’s atmosphere. When the shuttle does this, it is moving so fast that large amounts of heat are generated form the friction of air molecules.


Differences Between Aircraft and Spacecraft Spacecraft are designed to be protected from the intensity of heat. They have reinforced carbon on the wing surfaces and underside, high temperature black surface insulation tiles on the upper forward fuselage and around the windows and low temperature white surface tiles on the remaining areas. These materials are designed to protect the shuttle from the intensity of the heat during re-entry. When re-entry to the Earth’s atmosphere is complete, the shuttle is able to fly like an airplane. Spacecraft are designed with wings that can generate lift when needed.


Flight