Flight Unit B 6.6.1 Conduct tests of a model parachute design, and identify design changes - PowerPoint Presentation

Flight Unit B

6.6.1 Conduct tests of a model parachute design, and identify design changes to improve the effectiveness of the design.

Parachutes Earth is so large that its force of gravity pulls everything toward its surface. A parachute works to slow down something or someone from falling toward Earth’s surface by creating drag.

Drag Drag is the push on something from air or water. The bigger something is (that is, the larger its surface area), the more drag it creates. That is why a parachute works so well: it is very light, and it has a very large surface area.

How Parachutes Work It catches a lot of air, creating a lot of drag, which slows it down as it falls. 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 when they re-enter the Earth’s atmosphere.

6.6.2 Describe the design of a hot air balloon and the principles by which its rising and falling are controlled.

Hot Air Balloons Hot-air balloons are based on a very basic scientific principle: warmer air rises in cool air. A hot-air balloon rises because it is filled with hot, less dense air and is surrounded by colder, denser air.

How do they rise? In order to make a hot-air balloon rise and keep it rising, the air inside of it must be constantly heated. This is done with a burner positioned under an open balloon envelope . As the air in the balloon cools, the pilot can reheat it by firing the burner.

Hot-Air Balloon Parts A hot-air balloon has three essential parts: The burner , which heats the air The balloon envelope , which holds the air The basket , which carries the passengers

Fuel The burners in 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.

Lift 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 increases, so the flame grows in size. The pilot can increase speed by blasting a larger flame to heat the air more rapidly.

Descending 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 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.

Movement of Hot-Air Balloons 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 also control speed by changing altitude.

6.6.3 Conduct tests of glider designs; and modify a design so that a glider will go further, stay up longer or fly in a desired way; e.g.: fly in a loop, turn to the right.

Testing Glider Designs People often call paper gliders paper airplanes, but a true airplane uses an engine, while a glider relies on some external force to get it into the air. Both airplanes and gliders are designed to use the properties of air to fly. Once it is in the air, a glider uses the lift from its wings to remain in flight. A glider will not glide well if it is not designed well.

Design Factors Consider the following factors when designing and building a paper glider: Make the glider as light as possible. Make the fuselage (the part attached to the wings) as slim as possible to decrease drag. Make your glider stable. Adding a vertical stabilizer to your glider will help it fly straight and keep it stable during flight. The glider should have symmetry. This means that one side should be identical to the other in size and shape. Make sure your wings are the same size and shape.

Design Factors, Continued Make your folds carefully. Crisp, sharp edges allow the glider to fly better than edges that have been creased one way and refolded the other way. Pay close attention to the design of the wings. A good wing design has a slight curve so that it takes on an airfoil shape. This allows high-pressure air to build up under the wing and give the plane lift.

The Shape of the Wings The shape and size of the wings will also affect how the plane flies. Wings with a large surface area will give a glider a long, slow flight. Smaller, more aerodynamic wings will give the glider a shorter, quicker flight.

After the Test After testing your glider, consider the following questions: What do you notice about your glider’s flight? Does it travel in a straight line, or does it swoop and turn? How long will the basic paper glider stay in the air before it lands on the ground?

Modifications Think of ways you can make changes to the glider so it will fly differently. For example, what would happen if you added a paper clip to the glider’s nose? What if you folded the edges of the wings up or down to make ailerons? After each change, watch how your glider flies. Did the change help its flight the way you hoped it would?

6.6.4 Recognize the importance of stability and control to aircraft flight; and design, construct, and test control surfa ces.

Control Surfaces and Movement in Flight The control surfaces on an airplane are: The ailerons The elevators The rudder They allow a pilot to keep an airplane flying at a steady level, to move it to a different altitude, or to change course.

Airplane Movements The control surfaces work individually or in combination to move the airplane in three basic ways: Roll Pitch Yaw

Roll Roll is the rotation of the fuselage left or right. The pilot uses the ailerons to roll, or bank, the airplane left or right. Ailerons are hinged flaps on the training edge of an aircraft’s main wings.

How to Roll To achieve roll, the aileron on one wing is raised, and the aileron on the other wing is lowered. Airflow slows over the wing with the raised aileron, which causes a change in air pressure on the upper surface of that wing. The amount of lift on the wing decreases, and the wing dips down. The airplane banks in the direction of the dipped wing.

Banking left, banking right For example, if a pilot wants to bank the airplane to the left, the left aileron is raised, and the right aileron is lowered. The air moving over the upper surface of the left wing slows, and there is less lift on that side. As a result, the left wing dips and the plane banks to the left. If the right aileron were raised and the left aileron were lowered, the airplane would bank to the right. An airplane cannot roll if both ailerons are raised or lowered at the same time.

Pitch Pitch is the up-and-down movement of the nose of the airplane. Elevators are used to control the pitch. Elevators are hinged flaps found on the horizontal stabilizer of the tail.

Going up… When both elevators are up, the lift on the tail decreases. This is because the air moving over the top surface of the horizontal stabilizer is slowed down by the elevators and deflected upward. P ressure increases when airflow slows down. Higher pressure on the top of the horizontal stabilizer makes the tail dip. Air deflected upward pushes the tail down.

Lift When the tail goes down, the nose of the airplane rises. When both elevators are down, the lift on the tail increases, and the tail section moves upward. The nose drops. Elevators work together. They are either both up or both down to change the pitch.

Yaw Yaw is the side-to-side movement of the nose of the airplane. The rudder , a hinged flap on the vertical stabilizer of the tail, is turned to move the nose of the airplane. If the rudder is turned to the left, more drag is created on the left side of the vertical stabilizer. This turns the nose of the airplane left. If the rudder is turned to the right, more drag is created on the right side of the vertical stabilizer, and the nose of the airplane turns right.

6.6.5 Apply appropriate vocabulary in referring to control surfaces and major components of an aircraft. This vocabulary should include: wing, fuselage, vertical and horizontal stabilizers, elevators, ailerons, and rudder.

Aircraft Parts Airplanes and modern gliders are made up of several different parts that are needed for successful flight. Airplanes and modern gliders include the following parts…

Fuselage The main body of the airplane.

Cockpit Where the pilot sits

Landing Gear Wheels, floats, or skis used in takeoff, taxiing and landing on the ground.

Motor or Engine Gives the airplane thrust. In an airplane, the motor is attached to propellers.

Wing Extends out from the fuselage. The airfoil shape of the wing helps to create lift.

Leading edge The front edge of the wing that cuts into the air

Trailing Edge The back edge of the wing

Ailerons Flaps located on the trailing edge of the wings toward the tips. They can be used to make the airplane’s wings dip left or right. This movement is called roll. Ailerons work opposite each other.

Flaps Flaps located on the trailing edge of the wings close to the fuselage. They are used during takeoff and landing.

Horizontal Stabilizer A fixed horizontal tail part that stops the nose from moving up and down during flight.

Elevators Movable parts located on the horizontal stabilizers of the airplane. Elevators control the up- and down- motion of the nose of the airplane. This movement is called the pitch. Elevators work together.

Vertical Stabilizer A fixed vertical tail part that keeps the nose of the plane from swinging side to side during flight.

Rudder A movable part located on the vertical stabilizer of the tail of the plane. The rudder controls the left and right movements of the nose of the plane. This movement is called yaw.

6.6.6 Construct and test propellers and other devices for propelling a model aircraft.

Propellers There are two means of propulsion aircraft use to get thrust: Propellers Jet engines

Propellers Propellers are twisted wings that spin like powerful household fans. When looking at the cross section of a propeller, you would see that a propeller has an airfoil shape and different angles of attack. The airfoil shape creates high air pressure and low pressure areas. The propellers produce a lift force that moves the airplane horizontally instead of upward as the wings would.

Airplanes Airplanes may have two to six long, thin blades attached to an engine. The engine is the same kind that is found in most cars. The propellers found on the wings push air backward. This moves the airplane forward. The forward movement results in the wings cutting into the air, creating lift. Some propeller aircraft have the propellers at the back, and these propellers push the aircraft forward.

Helicopters Helicopters use special propellers called rotors for lift and thrust. A rotor pushes air down and the helicopter goes up. The smaller rotor at the back keeps the helicopter stable so it does not spin around. Helicopters get their thrust by angling the rotor as they fly. They tilt the rotor forward so that the blades push the air backward.

Jet Engines A jet engine generates thrust by burning fuel. The fuel mixes with oxygen from the air and ignites in a chamber in the engine. The exhaust gases are forced backward at great speed. This pushes the airplane forward.

6.6.7 Describe differences in design between aircraft and spacecraft, and identify reasons for the design differences.

Design Differences in Aircraft and Spacecraft Aircraft and spacecraft are designed differently because there is no air in space.

How they take off One of the main differences between aircraft and spacecraft is how they take off for flight. Aircraft get lift from the action of air moving over and under their wings. An airplane moves down a runway to get enough speed to create differences in air pressure. Once the airplane is moving forward fast enough, it takes off.

3, 2, 1… Liftoff! A spacecraft liftoff is very different. Spacecraft take off from a fixed launch pad. Launch pads are platform-type structures from which launches are made. Spacecraft achieve liftoff using large rocket boosters and powerful engines. Most rocket engines burn stored liquid oxygen and fuel. The exhaust is forced out the bottom, and the spacecraft moves upward.

Propulsion An aircraft’s propulsion is generated by jet engines or propellers turned by engines. Jet airplanes have engines that use the oxygen in the air to burn the engine’s fuel. The hot gases produced are forced out the back of the engine. The exhaust moves backward, and the airplane moves forward. Some airplanes have propellers that rotate and push air backward. The air is pushed backward and the plane moves forward.

Spacecraft Thrust Spacecraft get thrust in a similar way to jet airplanes. They burn fuel in powerful engines that force the exhaust to go out in one direction. This moves the spacecraft in the other direction.

Rockets Unlike jet engines, however, rockets carry their own fuel and source of oxygen with them. They are not dependent on the oxygen in the air.

Rockets in Space When a rocket leaves Earth’s atmosphere, it needs no extra push to keep it going through space. It will continue on the same path until acted on by another force. Since there is no air in space, control surfaces such as ailerons and rudders would not work in space. Spacecraft use the main thruster to move forward and thruster jets to move sideways. A small amount of liquid fuel and oxidizer is burned, and the exhaust is released through the nozzle of a thruster. The short burst of exhaust in one direction makes the spacecraft move in the opposite direction.

Landing Gear Aircraft use the control surfaces on their wings and tail to land. The aircraft still uses air to control the descent and landing.

Landing a Spacecraft Spacecraft have different problems when returning to the ground. Spacecraft must slow down before re-entering the atmosphere. To slow down, spacecraft turn some engines around. The exhaust shoots out in the same direction as the spacecraft is travelling. Because the exhaust is pushed forward, the spacecraft is pushed backward. This slows the spacecraft down enough to re-enter the atmosphere.

May the force be with you When spacecraft first re-enter the atmosphere, they are affected by the forces of gravity and drag. The capsule of the rocket falls toward Earth’s surface because of the pull of gravity. The air resistance causes drag. The air slows the spacecraft enough so that parachutes can be opened.

Parachutes to the rescue! The parachutes ease the landing. The engineers on the ground have to figure out where the rocket capsule will land because the pilot has no control once the capsule enters the atmosphere. The shuttle has special wings that allow it to glide and land safely on a runway.