have you ever wondered what makes an
airplane fly
there are four forces acting on an airplane in flight
these forces are left wat
thrust and dry
the study of these forces and their role in flight
is known as aerodynamics let's take a look at how these forces work together
to achieve straight and level on accelerated life this means that the
airplane is not turning
climbing this sending for changing
airspeed it should be fairly clear that before an airplane comply
left must be created left is the
upward force created by the effective airflow as it passes
over and under the way wat
is the force that opposes left and is caused by the downward pull a gravity
thrust created by the power plant
propels the airplane forward through the air while drag
a retarding force opposes rushed and limits the speed of the airplane
in an accelerated flight
were thrust in drag our equal the airplane will not speed up or slow down
like Rustin drag when left in wat r
equal the airplane will not buy I'm or the same
to help you understand that let's take a look at the basic principles of motion
my
in the 18th century Daniel Bernoulli expanded on Sir Isaac Newton's Laws 'em
force and motion to describe the principal love air flow pressure
differential
observing what happened to air as it passed through a to MNE
were newly discovered that as the velocity of the fluid or gas increases
its pressure decreases am
he also found that with a constant velocity
the pressure on the air remains the same had both hands at the tomb
the constriction is placed in the middle of the two the same Amada
here has to pass through a smaller area this increases the velocity
and decreases the pressure if you were to replace the construction with an
airfoil
such as a weighing the same principle would still apply
as oncoming air meets the leading edge of the airfoil
it separates with part of the air flow going over the top
and part going below since the air flowing over the top as farther
go it must travel faster the result is lower
air pressure above the way this is a component
up total let hey the remaining lived is provided by the downward backward
lower their generated from the top surface of the way the left provided by
this flow can be explained by Newton's third law of motion
which states that for every action there isn't equal
and opposite reaction the reaction to this down wash results in an
upward force on the wing and in increase in total left
before we look at various
airfoils and how they are configured to take advantage of the laws of motion
and principles uplift let's look at some of the terminology
a mind drawn from the leading edge to the trailing edge an airfoil
is referred to as the cord mine the camber up an airfoil
is the curve its surface and general aviation training aircraft
the upper camber is usually more pronounced then the Lord camber
any object moving through the air encounters a relative went
his way and is always parallel to and opposite the flight path
the angle formed between the relative wind and the cord mine
is called the angle of attack a way to measure left as relates to angle of
attack
is the mathematical expression coefficients
I've left for CL which is determined by wind tunnel tests
and is based on the design of the airfoil each airplane has an angle of
attack
where maximum lift the kurds this point is known as
CL max beyond this point
the airflow begins to separate from the wing surface
becoming so turbulent that the airport I'll can no longer create there
at this point the wing is in a stalled condition
the amount left that a wink and produce
depends on several factors one of these factors is wing design
which includes the shape or plan for my the way a straight wing has good slow
flight characteristics
but is not structurally efficient in terms of left and right swept back or
delta wing
is much better at higher speeds the tapered weighing on the other hand
has good slow flight characteristics and
has a relatively efficient design another wing design factor
is the aspect ratio or the relationship between the wings length and where
aspect ratio can be found by dividing the wingspan by the
average court in this example the wing has an aspect ratio of 9
at a given angle of attack the larger the aspect ratio
the last drag produced for the same amount have left
general aviation training aircraft for instance
normally have aspect ratios up seven to nine
while gliders are usually between 20 and 30
and other design factor that affects the wings flight characteristics
is the angle at incidents in this case the wings attached to the fuselages with
the cord mine
incline upward at a slight angle
you as a pilot can control left by changing individually
or in combination the airplanes airspeed
its angle of attack and the wing configuration
such as lowering the flaps if all other factors remain constant
doubling in airplanes airspeed develops four times more left
there's increase however is not without its drawbacks
sense any increase in left also results in an increase
in drag in addition with all other factors remaining constant
and increase in angle of attack increases left
for left to remain constant air speed and angle of attack must be used in
conjunction with each other
if air speed increases you must decrease angle of attack
conversely if you want to maintain the same Amada left at a slower airspeed
you must increase the angle of attack
and either way of controlling left is by changing the configuration of the wing
lowering the flaps can increase the lifting efficiency of the wing
and decrease the air speed at which the airplane stalls
as flap six dead and they change both the camber and the cord line at the wing
in the area of the flaps
there's not only produces lower pressure above the wing
due to the change in camber but it also changes the wings angle of attack
suppose that with the flaps up the angle of attack is five degrees
by lowering the flaps which changes the chord line
the angle of attack increases to 10 degrees
this higher angle of attack provides more left
and more drag
wage Mike left is not a constant it varies with the equipment installed in
the airplane
the number of passengers the amount of cargo
and the fueled during the course of a flight the total weight of the airplane
will decrease as fuel is consumed
in some specialized flight operations such as crop dusting
firefighting
or skydiving an additional reduction of total weight will occur
in the forward acting force which opposes drag and propels the airplane
is thrust same physical principles involved in the generation up left apply
when describing the foursome thrust
the thrust necessary to overcome drag
and propel the airplane through the air is produced by the power plant
turning the propeller if you look closely at a propeller
you will notice that it looks like a twisted airfoil as the propeller turns
a lower pressure area is created in front of each rotating blade
more pressure in front of the propeller like that above the wing
provides Leftwich axe forward this forward acting left
or thrust moves the airplane forward during an accelerated flight
where the airplane is neither increasing or decreasing airspeed
dressed in drag our equal however
thrust may be increased by using the throttle to increase power
when you increase power thrust will exceed drag
causing the airplane to accelerate with this acceleration however
there is a corresponding increase in drag drag will continue to increase
until it is equal to thrust these two forces are
in equilibrium the airplane will stop accelerating
and maintain the new hire airspeed the force acting in the opposite direction
to thrust
is dragged there are two types have dragged parasite
and induced parasite drag includes all the drag not directly related to the
production have left
it has generated by those areas in the airplane
which disrupt the otherwise streamlined floor there
these include items protruding into the air flow
such as the landing gear rough surfaces
and the mixing up the air such as where the Wayne joins the fuselage
as the speed of an airplane increases
the affects a parasite drag also increase
in contrast induced drag
is a direct byproduct of left it is greatest at slow speeds with a high
angle of attack
conversely at higher speeds and at lower angles of attack
induced drag decreases if the to drag terms are combined
and the values added together we can find a point where dragons at a minimum
this point is known as L
over d-max which is where left when compared to drag
is at its greatest in later sections you will see that flying the airplane at
this speed
provides the best glide ratio and other performance benefits
the phenomenon known as ground effect occurs when the earth's surface
interferes with normal airflow patterns that's causing a reduction in induced
drag
during flight altitudes the down wash created by wing tip vortices
causes the average relative wind to be inclined
downward because left axe perpendicular to the average relative wind
total left is inclined after by the same amount
the component have left acting in a rear were direction
is induced drag as your airplane the SANS to within one wing span on the
ground
the wing tip vortices at resulting down wash
are deflected horizontally this in turn moves the average relative wind closer
to the horizontal
and the total debt vector closer to vertical
thus increasing the vertical component left
and decreasing induce drag as a result the airplane tends to fly longer in
ground effect
or float down the runway this can be a problem on shorter runways
and other problem occurs during takeoff where you may left off in ground effect
at a very slow airspeed
your airplane has an accelerated to a safe climb speed
before climbing out a grounder fact the airplane could settle back to the runway
the information presented in this section has provided you with a
fundamental knowledge
up the forces at work on the airplane during straight and level
on accelerated flight the next section will expand your knowledge
what happens to the four basic forces during maneuvering flight