All about f light
How does an aircraft fly?
In the 18th century, the Swiss professor, Daniel Bernoulli
discovered that in a moving fluid the pressure is lowest
in areas where the speed of the flow is greatest.
This discovery gave early engineers an idea: if the speed
of air above a plate could be increased in comparison to
the air below it, then the air above would be at a lower
pressure and hence would pull upwards on the plate.
Designers found that a curved upper surface and a flat
lower surface, as shown in figure A, could produce this
difference in air speed.
Area of low
pressure (suction)
Lift
Figure A
It was found that the lift produced increased with
increasing speed, so if an aircraft could be made to
travel fast enough, the resulting upward force could
lift the aircraft off the ground. This was achieved using
propeller engines (and later jet engines) which could
propel the aircraft fast enough with a force known as
‘thrust’.
How does an aircraft descend and
climb?
Just like any other moving object an aircraft goes straight
and level until there is another force that changes its
direction. Increase the speed of the engines and the
thrusting force produced by the engines makes the
aircraft go faster, which makes the air over the wings
flow faster producing more lift and making the aircraft
climb.
Elevators are used to control up and down (pitch)
movements of the plane. The elevators are surfaces on
the tail plane (figure B). If the pilot pulls the control stick
towards him, the elevators are angled upwards. The air
that is pushed against these surfaces pushes the tail
downwards, and the aircraft climbs.
The theory was that because the air flow over the top
has to travel a longer distance, it has to travel further
and at a higher speed (this has since been shown to be
more complex).
Result: The pressure above the wing is lower than the
pressure below. This pressure difference results in an
upwards force on a wing known as ‘lift’.
Rudder
Yaw
Elevators
Elevators
Figure C
If the pilot pushes the stick forwards (figure C), the
elevators are angled downwards and the tail is pushed
upwards by the speed of the air, making the aircraft
descend.
How does
direction?
Stick
an
aircraft
change
Two parts of the aircraft direct the left and right
turns: the rudder and the ailerons (figure B).
Roll
Ailerons
Pitch
Pedals
The rudder on the vertical fin pushes
the tail left or right depending on the
movement of the foot pedals. The
rudder acts in exactly the same way
as a rudder on a boat. This left or right
movement is called YAW.
Figure B
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For your safety and others we ask that you do not point or throw handmade planes at people or animals.
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All about f light
If the pilot presses the left pedal the rudder will angle
left causing the air to push the tail to the right and the
aircraft will go left.
There are four forces acting on an aircraft in level flight
(see figure D).
1. Thrust: produced by the engines
2. Drag: resistant force produced by the air ‘hitting’
the aircraft
3. Lift: produced by the flowing air over the wings
4. Weight of the aircraft acting downwards
The ailerons are long, thin flaps on the rear or trailing
edge of the wings. They are connected to each other
in that if one moves down the other one moves up. For
example if the aileron of the right wing moves down,
then this wing will move up and the aircraft will roll left.
The opposite movement causes a right roll of the aircraft.
The four forces are related to each other through the
following formulae:
Lift = 0.5 x density of air at altitude x speed2 x area of
wings x lift coefficient
Turning an aircraft is a combination of the left and right
movement of the control stick and pressing one of the
foot pedals, to combine roll and yaw.
Lift
Drag
Drag = 0.5 x density of air at altitude x speed2 x area
of wings x drag coefficient
In level flight: lift = weight
drag = thrust
Thrust
US
A380AIRB
The drag coefficient is related to the wing area, pitch
angle and induced drag. Induced drag is created by
the air flowing over the wing.
Weight
1.
The lift coefficient is related to the pitch angle and wing
geometry and indicates how much lift the wing can
produce.
Two experiments on mechanics of flight
Fold up
Cut
This experiment demonstrates the upwards force
created by the Bernoulli effect. Blow over a piece of
paper as shown below.
Fold down
The reduced pressure above the sheet pulls the sheet
upwards because the air above the sheet is faster, and
creates an upwards force.
2.
Fold a standard paper dart as shown above.
Ask an adult to help you cut 2 slots of approximately
1cm on each side of the wing as shown above. Then
fold one flap down and the other one up also as
shown above.
When you throw a dart it should spin.
Why? The airflow will hit the 2 flaps creating
forces in opposite directions and
making the dart spin.
Please read: Adult supervision may be required for some of these exercises so please ask an adult to help you.
For your safety and others we ask that you do not point or throw handmade planes at people or animals.
Thank you for taking care and have fun.
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• Drop a piece of paper on the ground.
• What happens?
Launch it and see how far it travels. Was it a success?
Do you think you could improve the design?
Try it again. This time fold the wing tips upwards. Was
it better or worse, did anything unusual occur? Try
folding the wings downward and see what happens.
• Now run with it held out flat in front of you.
• Can you explain what happens and why?
• Try holding the paper at different angles.
Fold a piece of paper into the shape of a paper aeroplane
as shown. This is a simple glider.
(a)
Using your glider you can now add paper clips to the
wings, one on each side. What happens now? What
you are doing is altering the centre of gravity.
(b)
Other ideas:
Make other gliders using the same pattern. Change
the shape of the wing. Make them from different
thicknesses of card. Add plasticine to the front end of
the glider and see what happens. Why?
(c)
(d)
(a) Take a piece of paper and fold it in half as shown
(b) Now fold the two corners down
(c) Fold the top edge back to meet the bottom edge
(d) Fold it again to complete the plane
Please read: Adult supervision may be required for some of these exercises so please ask an adult to help you.
For your safety and others we ask that you do not point or throw handmade planes at people or animals.
Thank you for taking care and have fun.
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Moving t
All aircraft need power to launch them and, apart
from gliders, to propel them when in the air. Small
aircraft can use engines like those in cars but larger
ones need a lot more power. Heavy engines also need
power to put themselves into the air!
Make some paper planes and try changing the shape
of the wing. Does this affect the way that they fly? See
if you can make a delta winged plane (flying triangle).
To see how a propeller works ask an adult to cut out
two blades from a piece of card.
The wing is really an aerofoil and has a curved top.
This makes the air flow faster over the top with
less pressure. So the higher pressure underneath
produced lift. Slight changes in the shape will make a
lot of difference to their lift.
Helicopters have
rotating blades called
rotors. You can make
your own rotor using
the plan below.
Ask an adult to cut a cork in half, make a hole through
it lengthways and then cut a slit for each blade in the
side of the cork. Glue the blades into the slits. Put the
propeller onto the shaft.
Balsa wood
12 x 2 cms
Rubber Band
Blow from the front and record what happens. Which
way does it turn? Try blowing from behind. Try twisting
the propeller blades slightly.
1.Fix the two pieces of balsa
wood (you could use wooden
lolly pop sticks together with a
rubber band).
2. Adjust for flight.
3.Take off band and glue
together.
• Find a sycamore seed and watch it fall.
• The turning blades of a helicopter
produce lift
• How do you think the jump-jet works?
• Look at pictures of different
helicopters.
• Why do you think many
helicopters have small rotors on
the tail?
Please read: Adult supervision may be required for some of these exercises so please ask an adult to help you.
For your safety and others we ask that you do not point or throw handmade planes at people or animals.
Thank you for taking care and have fun.
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W
Air is all around us.
It is made up of invisible gases. The main gases are
nitrogen and oxygen. There
is about 160 kilometres of air
above us.
The layer of air around
the earth is known as
the atmosphere. One
way in which you can
test that it is there
is by taking a deep
breath. You will be able
to feel the air going into your
mouth.
The air nearest the ground is thickest and the higher
you get the thinner it gets. What do you think the
problem would be if you were standing on the highest
mountain in the world and how do you think you could
overcome it?
In space there is no air at all.
What do you think astronauts use to help them
breath?
The air can lift and carry things along.
Take a piece of paper outside on
a windy day and place it on the
ground. What happens to the
piece of paper?
Why?
Did you know that air presses down on the ground
just like a solid object!
Throw a number of different objects through the air
and write down what happens. You could try a solid
rubber ball, a tennis ball, a table tennis ball. Which of
them goes the furthest? Why?
Do you think it has got anything to do with the
air?
Please read: Adult supervision may be required for some of these exercises so please ask an adult to help you.
For your safety and others we ask that you do not point or throw handmade planes at people or animals.
Thank you for taking care and have fun.
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Kites an
Kites have flown for thousands of years and are very
easy to make.
Some of the most spectacular ones are made by
the Chinese and Japanese.
Using this simple plan, make your own kite. Try it out
without a tail and record what happens. Now add a
tail to your kite and see if there is any difference.
Ask an adult to help you make your own parachute
using a piece of thin paper or tissue. Cut out a square
and fit a piece of cotton to each corner. Fix the ends
of the threads together with a piece of Plasticine and
add a small weight. Drop the parachute and record
what happens.
• Does it go in a straight line?
• Does it drop quickly or slowly?
The lift is the force which keeps the kite in the air.
Parachutes were first thought of by Leonardo da Vinci.
He drew sketches of them.
Now make a number of
parachutes using different
materials. Do you notice
any differences when you
drop them?
Collect some seeds
together and watch how
they fall. Why do you think
they fall in different ways?
Please read: Adult supervision may be required for some of these exercises so please ask an adult to help you.
For your safety and others we ask that you do not point or throw handmade planes at people or animals.
Thank you for taking care and have fun.
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Make y
Airports are busy places and need to be built in areas
with good road and rail links.
What kind of services do you think you might
need at an airport and what kind of aircraft
would you allow to land there?
What decides the direction in which you
build your runways and how long are they?
You could collect together a number of airline
timetables or look on the internet and see how long it
might take you to travel from one country to another.
See if you can find out the names of the major airlines
flying into this country.
Some planes like the Airbus A380 are very
large and can take many people very long
distances.
Ask an adult to
help you design and
build a model airport.
Mark in the runways and fix
up a system of lights alongside
the runways to help the aircraft
when they have to land at night or in
the fog.
You could produce some invitations to the
opening of the new airport, and design a
brochure telling people about the facilities
you have to offer.
Travel in the future may be very different
from today. Imagine you are travelling 100
years from now, what would it be like and
where would you go?
Find some pictures showing the different
types of aircraft available and decide which
ones will be allowed to land. Is your runway
long enough and do you have enough room
for the new Airbus A380 double-decker?
How many passengers do you
think your planes will carry?
Please read: Adult supervision may be required for some of these exercises so please ask an adult to help you.
For your safety and others we ask that you do not point or throw handmade planes at people or animals.
Thank you for taking care and have fun.