when was the last time you took a flight or even saw a plane in the sky? planes have
become so common in our lives that it's easy to take them for granted and forget that these are
hundreds of tons of gravity defying metal gliding gracefully through the sky at 30,000 feet so in
this video we're going to break down the physics and engineering behind how that's even possible
and look at how the principles of aerodynamics are actually all around us whether in a paper
airplane or garden hose or even just driving down the streets now for an aircraft and level flights
there are four forces acting on its gravity or its weight pulling it down that is opposed by
an upward force called lift thrust enabling it to go forward opposed by drag that is pulling
it back gravity is pretty simple to understand but we're going to break down how lift thrust
and drag are produced and how different components of the plane are designed to essentially control
these forces depending on the face of flights so although the field of aerodynamics is incredibly
complex in fact it's quite literally rocket science I'm going to show you in this video
that anyone whether you're a pilot a student or math-o-phobe that you can understand at a high
level how planes work is using very simple beginner-friendly terms so let's get started
so how to planes seemingly defy gravity and create lift? well the answer is simple the
majority of lift is generated by the wings that meet the incoming airflow at an angle called the
angle of attack now this creates lift in two ways first the incoming air stream will be split into
two paths one above and below the wing now since the wing is tilted at an angle the air molecules
below the wing will be forced into a smaller area creating an area of high pressure and the opposite
happens above the wain where the air molecule must have a larger area to occupy which creates
an area of low pressure and of course the natural tendency for the molecules in the higher pressure
area is to expand upwards toward the area of lower pressure and hence as a result of this attempt for
Equalization the wing is pushed upwards now at the same time air molecules that hit the underside of
this tilted wing are forced downwards now Newton's third law tells us that for every action there is
an equal and opposite reaction what this means in this case is that since the wing exerts a force on
the incoming airflow pushing it downwards by Newton's third law the air must also exert a
force on the wing pushing it upwards and hence we have our lift now these two reasons are the
fundamentals behind how planes get off the ground now strictly speaking to measure the amount of
lift that is produced by an airfoil engineers use a metric called its lift coefficient that
is dependent on four factors air density wing area angle of attack and airspeed while air density and
wing area don't tend to fluctuate too much for a particular flights the airspeed becomes very
important for example during takeoff you'll feel the point where pilots start to lift the nose off
the ground this is to increase the aircraft's angle of attack for more lift this point is
also known as VR or rotation speed which tells pilots that the speed of the aircraft relative
to the incoming airflow is high enough to start producing lift now there is a common misconception
that I want to clear up here many of you may have heard a different explanation for how lift
is created involving an airfoil that looks like this and something called Bernoulli's principle in
this theory people speculated that airflow travels faster above the wing than below the wing since it
needs to cover more distance in the same amount of time they use what is called Bernoulli's principle
which states that a fluid traveling at a higher velocity will experience higher pressure so by
this principle since molecules travel faster above the wing this creates an area of lower
pressure than below the wing but this theory is only partially correct in fact it's got its
cause and effect the other way around in fact it's due to the angle of attack that the difference in
pressure is created and hence by the Bernoulli's principle the difference in air velocity above and
below the wing is observed otherwise how it planes be able to fly upside down and how it planes with
completely flat wings fly however there is very good reason why most wings today aren't completely
flat and that is to reduce drag drag is what pulls an aircraft backwards of course in most cases this
is undesirable now there are cute types of drag parasitic drag from the physical shape of the
airplane and induced drag that is produced as a byproduct of lift now parasitic drag is pretty
easy to understand any object in this case an airplane in an Airstream will disrupt airflow
essentially pushing air molecules away from its surface onto incoming air streams this is why
where we put our hands out the window of a moving car we feel a slight pressure pushing it backwards
now depending on the shape of the object the air is displaced differently and hence the amount of
drag created also varies this is why we see a lot of air foils with curved cross-sections and this
is to reduce drag now there's also a component called skin frictional drag that is created by
the airflow pushing against the different surfaces of the aircraft so of course the larger the
frontal cross section of the airplane the more parasitic drag it produces now there is also
induced drag that comes whenever lift is created we know that the area beneath the wing has higher
pressure than above the wing but near the wing tips these sneaky air molecules have a shortcut
instead of trying to push the wing upwards they can simply go around the outside of the wingtip
to the top instead and swirls back down onto the top of the wing now this creates a vortex and as
a result of these wingtip vortices the lift force at the wingtips is actually perpendicular to the
top of the wing this means that they also contain a component that is traveling backwards or a drag
force now these vortices called wake turbulence are actually very dangerous as they disturb the
air behind the aircraft now the weight turbulence caused by a larger airplane can actually be strong
enough to flip smaller airplanes and make them lose control of course this is why we don't see
airplanes takeoff one right after another now this is also why if you ever listen to
air traffic control radio you'll hear call signs like Air Canada wants you three heavy this is to
indicate to other airplanes behind it that it is a larger aircraft with heavy wake turbulence so stay
a safe distance away there are also many ways to minimize induced drag for example increasing
the ratio between the length of the wing and the width of the wing also called its aspect
ratio or by using tapered wing tips or winglets to decrease induced drag thrust is what allows
planes to move forward in a most civilian planes it is produced by propellers powered by engines
propellers worked exactly in the same way as wings do except in this case the airfoil is
simply traveling in a spiral course now instead of directing the airflow downwards toward the
ground to create lift the blades of a propeller direct airflow backwards to create thrust however
different parts of the propeller blade travel at different speeds so in order to generate the
same amount of thrust along its entire length the angle of attack at every point needs to change now
this is why propeller blades are often twisted on many smaller aircrafts like cessna's the forward
thrust these propellers produce alone is enough but on commercial airliners like a Boeing 737
these propellers are used to direct air into its jet engines now we can break down what happens
inside a jet engine in five steps first a large amount of air is pulled into the engine by super
efficient propellers also called turbo fans second the air is compressed up by about 40 times its
original volume now this increases its pressure and its temperature this step is necessary since
it increases the amount of oxygen in the chamber which is an essential ingredient for combustion
and at higher temperatures reactions occur faster third this compressed air is sent into
a combustion chamber where it comes into contact with streams of fuel and combusts immediately then
the hot air is pushed through a set of turbine blades essentially spinning them like a windmill
now this turbine is connected to the turbo fans in the front powering them to spin faster and second
more air to complete the cycle finally in step five the large volume of hot air is then squeezed
through a small opening in the back of the engine and again Bernoulli's principle tells us that the
increase in pressure means that the hot gas is expelled at a higher velocity this is similar
to how if you hold your thumb over a garden hose you'll notice that the water shoots out faster
and with higher pressure so now you understand how jet engines work now most of these principles hold
for subsonic flight or flight below the speed of sound and as we start to exceed the sound barrier
some of these characteristics become a little bit wonky and hence modifications needs to be made for
aircraft design especially for fighter jets or a reconnaissance aircraft life the Blackbird now
in order not to make this video two hours long we won't be diving into how supersonic flight affects
thrust however it's definitely a very interesting topic that I recommend you research on your own
so now that we understand the different forces acting on an airplane during flights how do pilots
actually manipulate those forces to control the airplane well to understand that we have to know
that the airplane has three basic movement axes it can change its roll pitch and yaw now you can
imagine a roll movement to be similar to rolling a burrito in this case rolling the plane along
its fuselage roll is changed by the ailerons that are located on the outer section of the
wing an aileron can move to increase or decrease the angle of attack of the wing which changes its
amount of lift now this imbalance in list on the two ways creates a roll movements now the
second movement is the pitch which essentially points the nose upwards or downwards this is
controlled by the elevators that are located on the horizontal stabilizer in the back of the plane
and similarly it's able to change the amount of lift generated on the tail section of the plane
so if this hill generates more lift relative to the wings the plane points downwards and if this
hill generates less lift the plane points upwards and lastly we have a yaw movement or the movement
of the nose left and right just imagine movement of a plane that is placed on a mega-sized lazy
susan this is controlled by the rudder located on the vertical stabilizer which is basically a
huge vertical wing that deflects air to the left or to the right now by using a combination of
those controls pilots are able to navigate the airplane to mostly aware they like to go stall
happens when lift is no longer being created the slower the aircraft flies the slower the stream
of airflow hits the wing and hence the higher angle of attack is needed to generate lift but
when the angle of attack is too high either from the airspeed being too low or just pilot control
lift is no longer being created as we mentioned before the air logged must flow downwards on top
made an area of lower pressure however when the angle of attack is too high air molecules zoom
past the top of the wing directly to these can happen what's an aircraft stalls it can go into
a dive or spin when both wings lose lift at the same time the plane will enter a nosedive no the
way to recover from a dive it's actually pretty counterintuitive because the pilot needs to push
the nose down even further to decrease the angle of attack essentially the play needs to trade
altitude for airspeed for the wings to create lift once again this is why it's especially dangerous
for planes to stall close to the ground during a stall we can also happen is one-way loses lift
before the other and the plane will roll violently and enter a spin spins are a lot more difficult to
recover from and recover ability also depends on how controllable the aircraft is for example on
planes such as the b-2 spin recovery is near impossible since the control surfaces are so
limited now I dive deeper into the engineering of the beach.you in an airplane anatomy episode
so feel free to go check that out if you're interested now there is another factor affecting
lift that we haven't talked about much and that is air density now as we get higher in altitude
the air becomes less dense hence to generate the same amount of lift the airplane needs to speed
up this is why stall speeds for airplanes increase as altitude increases as well but airplanes also
have a limit to how fast they can fly they exceed this called over speed the aircraft is at risk
for physically breaking apart or components failing hence as the plane flies higher the
margin between the stall speed and the over speed limits becomes smaller and smaller until they meet
this is what is referred to as coffin corner and is what restricts airplanes from simply flying
into space now this graph is actually slightly misleading you'll see that the over speed limit
decreases as altitude increases now this is actually not because the limit is changing
but because the speed in this case is measured using an indicated airspeed which is a sensor that
measures dynamic pressure now indicated airspeed is then calculated using a fixed air density which
in reality decreases as you fly higher hence even if your true airspeed is the same you're
indicated airspeed actually decreases as you gain altitude this is why it might seem like the over
speed limit is decreasing as altitude increases when in reality it stays constant throughout so
there you have it a crash course to the basics of aerodynamics now I hope that by watching this
video you have some sort of new appreciation for these magical machines that stay in the skies and
I hope that the next time you fly just a little bit of that anxiety and frustration and sadness
of traveling is replaced by a little bit of wonder lust at the plane that you're flying on but this
is just the tip of the iceberg on my channel I actually do a series called airplane and out of
EU where I break down the history the engineering and the physics behind different airplanes so so
far I've done the sr-71 Blackbird the Supermarine Spitfire and the Airbus a380 and many more so
feel free to go check those out and of course if you enjoyed this video give it a thumbs up and
share it to your friends shares your community maybe they'll enjoy it too now don't forget
to subscribe to my channel for new a nation content coming out and I'll see you soon you