ATPL Principles of Flight - Class 13: Controls.
Summary
TLDRIn this educational video, Grant explores the principles of flight, focusing on aircraft control surfaces. He explains how ailerons, elevators, and rudders manipulate airflow to achieve pitch, roll, and yaw, allowing pilots to maneuver. The video also covers the concept of 'feel' in controls, aerodynamic balances, tabs, and the importance of trim systems. Additionally, it touches on advanced control concepts like stabilators, rudder trim systems, and spoilers, providing a comprehensive understanding of how aircraft control surfaces work.
Takeaways
- ✈️ The main aircraft controls manipulate airflow to achieve maneuverability around three axes: pitch, roll, and yaw.
- 📉 Ailerons control roll by creating unequal lift on the wings, while elevators manage pitch, and rudders handle yaw.
- 🔄 Control surfaces work by changing the camber of the wing, similar to flaps, to alter lift distribution and generate force.
- 📚 This class connects theoretical concepts with practical applications, emphasizing the importance of control surfaces in flight.
- 🔧 The 'feel' of controls is due to the aerodynamic forces generated when surfaces are deflected, creating a resisting moment.
- 🛠 Aerodynamic balances like inset hinges, horn balances, and internal balances are used to reduce the feel moment and make controls easier to manipulate.
- 📉 Control tabs, including balance tabs, anti-balance tabs, and servo tabs, are used to adjust the feel and response of control surfaces.
- ⚖️ Trim systems allow pilots to adjust the neutral point of control surfaces for ease of control and to counteract effects like a forward center of gravity.
- 🚀 High-speed aircraft often use powered or power-assisted controls due to the high forces involved, sometimes incorporating artificial feel systems.
- 🏞️ Adverse yaw can occur during roll maneuvers, but it can be mitigated by adjusting aileron deflection to balance drag.
- 🏁 Spoilers serve dual roles on larger aircraft, assisting in roll control and acting as speed brakes to increase drag and reduce speed.
Q & A
What are the three main axes of aircraft movement?
-The three main axes of aircraft movement are the normal axis, the longitudinal axis, and the lateral axis. These axes are responsible for pitch, roll, and yaw movements, respectively.
What is the primary control surface for roll movement?
-The primary control surface for roll movement is the aileron, located on the wings.
How does the elevator control the pitch of an aircraft?
-The elevator, located at the tail, controls the pitch by deflecting up or down, which changes the resultant force and causes the aircraft to rotate around the lateral axis.
What is the role of the rudder in controlling an aircraft?
-The rudder, also located at the tail, controls the yaw by deflecting to the left or right, which rotates the aircraft around the center of gravity.
How do control surfaces manipulate airflow to maneuver an aircraft?
-Control surfaces manipulate airflow by modifying the camber, similar to flaps, which changes the lift distribution and creates a large change in the local coefficient of lift, resulting in a force that allows the aircraft to rotate around its center of gravity.
What is the purpose of the aerodynamic balances in control surfaces?
-Aerodynamic balances are used to reduce the feel moment, which is the resistance felt by pilots when deflecting control surfaces. This makes it easier for pilots to manipulate the controls, especially at higher speeds.
What is the function of a servo tab in aircraft control?
-A servo tab is a small control surface that moves in response to the pilot's input, which in turn moves the main control surface. This allows the pilot to feel only the force in the servo tab, making control surface manipulation easier.
Why is it important to have a rudder trim system in an aircraft?
-A rudder trim system is important to adjust the neutral point when flying asymmetrically, such as when one engine is out, to prevent the risk of fin stall and to maintain directional control.
How do spoilers assist in roll control on large aircraft?
-Spoilers assist in roll control by deflecting up on the same side as the aileron that deflects up, or the downward going wing, creating a larger imbalance of lift between the wings and aiding in the rotation.
What is the concept of adverse aileron yaw and how is it managed?
-Adverse aileron yaw occurs when the wing that travels up through the air, due to increased lift, also experiences more induced drag, causing a yawing motion towards that wing. It is managed by adjusting the levels of deflection on either side to balance the drag forces.
Outlines
🛫 Principles of Aircraft Controls
This segment introduces the concept of aircraft control surfaces and their role in maneuvering the aircraft. It explains that control surfaces manipulate airflow to achieve movement around the three main axes: pitch, roll, and yaw. The presenter, Grant, discusses the primary controls including ailerons, elevators, and rudders, and how they correspond to roll, pitch, and yaw respectively. The segment also covers the fundamental idea of control surfaces altering camber to change lift distribution, resulting in the rotation of the aircraft around its center of gravity. It sets the stage for a deeper dive into the mechanics of each control surface.
🔍 Deep Dive into Control Surfaces and Feel
This part delves deeper into the mechanics of control surfaces, focusing on the 'feel' experienced when they are manipulated. It explains that the resistance felt is due to the aerodynamic force generated by the deflection of control surfaces, which creates a moment opposite to the direction of deflection. The segment discusses various methods to reduce this 'feel' moment, such as aerodynamic balances, inset hinges, horn balances, internal balances, and tabs. It also touches on the use of powered controls in larger aircraft where manual force is insufficient, and the importance of maintaining control surface integrity to prevent overstressing.
✈️ Controlling Pitch and Trim Systems
The focus of this section is on pitch control and the use of elevators and stabilators. It describes how elevators, using a symmetrical airfoil, generate forces that rotate the aircraft around its center of gravity. The concept of trim is introduced, explaining how it adjusts the neutral point of control surfaces to maintain a desired attitude without continuous input from the pilot. The segment also discusses the trimmable horizontal stabilizer (THS), which allows for full range of motion while maintaining trim capabilities, and the importance of this system in modern jet aircraft.
📚 Understanding Yaw and Rudder Dynamics
This segment explores yaw control using the rudder and the vertical stabilizer, also known as the fin. It explains how rudder deflection generates forces that cause the aircraft to yaw, and how the airflow against the fin can create a restoring force to correct sideslip. The discussion includes the potential for a fin stall due to excessive angle of attack and the necessity of a rudder trim system to counteract this risk, especially during asymmetrical flight conditions like flying with one engine out.
🔄 Ailerons and Roll Control
The segment discusses roll control through the use of ailerons, which create unequal lift on each wing to induce rotation. It explains the phenomenon of aerodynamic damping, where the motion of the wings resists the roll due to the change in angle of attack. Additionally, it addresses the issue of adverse yaw, where the wing with more lift experiences more drag, causing a yawing motion. The segment also covers the use of spoilers for roll assistance and as speed brakes, highlighting their effectiveness at high speeds due to the relationship between parasitic drag and velocity squared.
🛠 Advanced Control Systems and Their Applications
This final segment summarizes the various control systems and their applications. It revisits the concepts of feel, aerodynamic balances, and tabs, emphasizing their role in reducing the feel moment for pilots. It also discusses the use of servo tabs, spring tabs, and powered controls to manage the forces involved in controlling large aircraft. The segment concludes by summarizing the functions of control surfaces in pitch, yaw, and roll, and mentions advanced configurations like V-tail rudders and flaperons. It also touches on the use of spoilers for roll assistance and as speed brakes, noting their effectiveness at high speeds.
Mindmap
Keywords
💡Control Surfaces
💡Pitch
💡Roll
💡Yaw
💡Aerodynamic Balances
💡Trim
💡Spoilers
💡Stabilator
💡Adverse Aileron Yaw
💡Servo Tab
Highlights
Introduction to aircraft control surfaces and their role in maneuvering the aircraft.
Explanation of the three main axes of aircraft movement: normal, longitudinal, and lateral.
Description of how ailerons control roll by manipulating airflow over the wings.
Discussion on how elevators control pitch through the use of a symmetrical airfoil.
Understanding yaw control with the rudder and its impact on the aircraft's movement.
The concept of modifying camber to change lift distribution and local coefficient of lift.
Importance of control surface deflection in generating force for aircraft rotation.
Feel in aircraft controls and its relation to the force generated by control surface deflection.
Methods to reduce feel moment in controls, such as aerodynamic balances and inset hinges.
Introduction to horn balances and their role in counteracting feel moment.
Explanation of internal balances and how they use air pressure to reduce feel.
The function of balance tabs in reducing the feel moment of control surfaces.
Use of anti-balance tabs to artificially increase the feel moment for control safety.
Servo tabs and their mechanism for reducing pilot feel while controlling large control surfaces.
The application of powered controls in large aircraft to assist with control surface movement.
Principle of trim in aircraft controls and its impact on the neutral point.
Trimmable horizontal stabilizer (THS) as a solution for maintaining full control range.
Rudder and fin interaction in controlling yaw and the concept of sideslip.
Adverse aileron yaw and methods to counteract it through control surface coordination.
Spoilers' role in assisting roll and acting as speed brakes on large aircraft.
Transcripts
it's all very well flying through the
air but it's a bit pointless unless we
can decide where we're going
we do this of course using the controls
but how do they work
let's find out
hi i'm grant and welcome to class 13 in
the principles of flight series
today we're going to be looking at how
the control surfaces manipulate the
airflow
and allow us to maneuver the aircraft
through the air and fly to where we want
to go
this class builds on everything we've
learned before and is a good
practical application of all those
theoretical concepts we've learned up
until this point
the main controls on an aircraft are
those that provide us with movement
around the three main axes
they are the normal axis
the longitudinal and
the lateral the movement around these
axes are known as pitch roll
and yaw roll is primarily controlled by
ailerons on the wings pitch
is primarily controlled by the elevator
at
the tail and yaw
is primarily controlled by the rudder
also located at the tail
the fundamental concept of a control
surface is to modify
the camber in the same way that flaps do
this changes the lift distribution and
means that there is a large change in
the local coefficient of lift
this increase in the local coefficient
of lift
results in a large force being created
and we use that to rotate around
the center of gravity in contrast to
flaps though
instead of only deflecting down flaps
sorry control surfaces because move up
as well as down to generate this force
and the corresponding force will be up
or down some direction if we look at the
individual controls quickly we can see
the
elevator uses a symmetrical airfoil and
the deflection
up or down makes a change in the
resultant force
and this will rotate the aircraft around
the lateral axis
in pitch the rudder is exactly the same
but we're operating
in a different plane this sort of
vertical
upright one using the normal axis
again any deflection of the rudder
either to the left or the right
will rotate us around the center of
gravity to
the left or to the right the ailerons on
the wings
are not always placed on symmetrical
airfoils because they're obviously on
the wing and quite often that is not a
symmetrical airfoil
so what they do is they use a difference
between either side
to generate this rotational moment when
one aileron drops to increase the lift
locally the opposite side will deflect
up and disrupt the airflow and cause a
reduction
in lift it won't cause a full downward
resultant force because
the aerofoil is not symmetrical it still
has
that asymmetric shape that classic
aerofoil shape
but it will cause a reduction in the
total amount of lift and this
out of balance lift between the upward
and the downward going ailerons
is why we get that unequal force and we
roll
um around the longitudinal axis we're
going to jump a bit deeper into
each of the individual controls later on
but first we have to understand some
general concepts about controls
the first concept to talk about is
something known as
feel as you might expect it is the
feeling of the controls it's that
stiffness and resistance to the movement
the reason for feel is because when we
deflect
our control surface down and generate
this new
force that we use to actually turn our
aircraft
you essentially end up with a moment
being generated
you have this force and the distance
that the force
um is generated from this sort of local
center of pressure
is a certain distance away from the
hinge of where you actually rotate the
control
around that means that
force times distance equals a moment and
that is in the
direction that is opposite to the
direction we are deflecting the control
so if we deflect the control down the
force that's generated
because we're increasing the camber is
up the way and the local center of
pressure for the control surface is
located here a certain distance away
from the hinge
and you get a resisting feel moment that
opposes the motion
of the control surface deflecting the
feel
moment is directly related to the force
produced
and the force is generated the same way
we do for all of our aerodynamic forces
it's a half rho v squared s c l
so we can make some assumptions about
our
feel moment basically if we have a
higher coefficient of lift
we're gonna have a higher force and that
means we're going to get a more severe
feel moment higher coefficient of lift
from deflecting the controls further we
increase the camber further which
increases that coefficient of lift
also if we increase the area
surface area of the control surface that
means that we're going to get a larger
force and more resistance one more
feel and another thing is traveling
faster
higher dynamic pressure means that we're
going to
struggle more to move the controls so
faster
larger area and deflecting more all
results in larger
feel which means it's harder to move the
controls
it can get so severe in fact that in
large aircraft you physically can't
overcome
the controls just with your own muscles
so you have to use
powered controls and you can also assist
with this
and by trying to reduce this feel moment
and make it easier for that hydraulic
system or
a manual cable system you use just your
brute force for
and you do this through something known
as aeronaut aerodynamic
balances there are quite a few types of
aerodynamic ballasts
but this is just the main ones here
in a normal hinge you have the hinge
point right where the control surface
and it meet
so when you generate the force here
your distance is this length here
what you can do is you can use an inset
hinge
where you move the hinge in and if you
generate that same force
the balance arm is shorter and the
moment is the force times the distance
you're reducing the distance
so that resistive feel moment will be
smaller in size
this is what it looks like in 3d you
would have a sort of in cut
into the wing surface itself
and it would rotate around this point
here
this would be your axis of rotation
another thing you can do is use a
horn balance horn balance adds
a portion of the control surface in
front of the hinge
like this and the area of control
surface in front
provides an opposing moment to
counteract the one created by the
control surface
and that counteracting moment reduces
the strength of the feel moment and
makes it easy for us another type is
something known as an internal balance
which uses a
pressure differential to create an
opposing moment
and counteract that feel moment
so basically a flexible seal is placed
on the inside between the control
surface and
the tail or the wing and when the
control surface deflects one way
the flexible seal stretches and creates
more space for the air to flow into
so if this was to deflect up this
flexible seal would reduce down like
this and you get a lot more pressure in
the top
than you would in the bottom and because
that is on the opposite side of the
hinge
that would counteract our feel moment
another thing we can do is use balance
tabs
in order to help us with controlling the
control surface itself
again balance tabs come in many forms
they're essentially small tabs placed on
the trailing edge of the control surface
and attached to the main wing or tail
itself when the control surface is
deflected they move in the opposite
direction
and therefore create a force in the
other direction and opposes the moment
this is a typical balance tab here if
you imagine you deflect the control
surface down
to create a force in this direction
this would still be attached to the wing
and it would deflect up the way and
create a force
this way so you would get an opposing
moment to the feel moment you also get
something called anti-balance tabs which
as you expect are the opposite of the
balance tab
it will deflect in the same direction as
the control surface
so if we move the control surface down
using our
physical cable connection to generate a
force here
the process of it deflecting down will
also deflect
this surface down and add to the fuel
moment
so you get one moment from the big
surface and one moment
from the small surface this basically
makes the controls feel
artificially heavier and it's useful for
reducing the possibility
of over stressing the controls on the
control surfaces
there's also something known as a servo
tab
so a servo tab is a method whereby
the control input this would be your
cable here
actually moves the tab
so it means the pilot only experiences
the force
from the tab so if you deflect it
down the way to create a force here the
pilot is only feeling this force
but what this does is this small tab
essentially flies the big tab so it
would
cause this big tab to move up the way
and actually generate a force
down think about it hinged at this point
it
deflects down generates a force this way
which pulls the whole thing up
and the overall control surface reflects
up the way generating a force
down one of the problems with a servo
tab
is that at slow speeds the deflection
of this small servo tab
might not be strong enough to actually
deflect the whole control surface
because it's already a small area and
it's a slow speed to force my actual
knowledge to be strong enough to move
the control surface
so one of the ways to get around this is
to use a
spring tab the spring tab controls the
control surface only above
a certain force so you are directly
controlling
the control surface and then when it
gets
too powerful and too much effort to
control
the spring will make it control the
tab and the tab will fly the control
surface in the appropriate direction
so all these methods as well as the
aerodynamic balances are just methods to
reduce the feel
for the pilots another way to do that is
to just use
powered controls power controls can also
assist with a very large aircraft where
the surfaces and the speeds that you
travel are simply
too high to overcome with manual force
so you can either get us power assisted
or fully powered controls
power assisted essentially just help you
to move these cables
and you still feel a small amount of
these feel
moments with fully powered controls
however
the hinge moment is completely overcome
because
some motors and hydraulics are moving
these cables around
and moving the control surfaces so you
don't actually have any input
so what you need to implement is an
artificial feel system
the artificial fuel system will scale
with the speed
traveled much like a normal feel system
would
because if the v goes up our force goes
up our reaction moments and our
fuel moments go up we basically
artificially generate this feel
so that we don't over stress the
controls and because it's scaling
according to the speed
this section here this is your dynamic
pressure
if you you call and the field system
a q feel system if it's in fully powered
controls
to control ourselves in pitch or around
the lateral axis
we use the elevator we said earlier that
a symmetrical airfoil is used for the
horizontal stabilizer or tail plane
and that way depending on the direction
of elevator deflection
the resultant force causes the aircraft
to rotate around the center of gravity
so if we deflect this surface down we
generate an overall force that goes
up the way and we rotate around our
center of gravity at the front
and that will cause us to rotate nose
down
it's important to note that the
direction of the force is
opposite to the direction we move
because we're located behind the center
of gravity
another way to control ourselves and
pitch is through using a stabilator
which is a symmetrical airfoil that
moves entirely
and therefore creates a local angle of
attack to the airflow
that is either positive or negative and
the resultant force
is the same as the angle of attack
so if this whole thing was to deflect
down
we see a local angle of attack
to the airflow and this local angle of
attack
generates a downforce in this case and
that would rotate us
in a nose up motion something to note
is the concept of trim trim
is essentially a changing of the neutral
point of the control surfaces
this allows the pilots to select an
input trim
and then you can release the pressure
that you use to move the controls
and the controls will stay where they
are an example we have seen
before is with the case of a after
forward center of gravity
which makes our moment arm for our
center of pressure change so if we have
a
center of pressure out here for instance
we get our lift coming off
center of gravity here and that would
cause a nose
down rotation
what we can do is then trim our surface
to deflect in the appropriate way in
this case it would have to
generate down force and a nose up
moment to counteract the nose down
moment
caused by this lift and center of
gravity lift weight
couple the only problem with this is
that if we change the neutral point
we will lose part of the range of motion
of this surface so when we've got a
normal range
of something like this if we trim it to
this point
then we can only deflect up by this much
a bit of a reduction in our range of
deflection for one direction
so a solution to solve this problem
is to essentially combine a stabilator
and an elevator into one
and you end up with something called a
trimmable horizontal stabilizer or a ths
and what you do is it's essentially
a whole stabilizer that will move up or
down
and that's what you use to trim so you
get a full range of trim
but then within that you still always
get your
full range of elevator deflection so
even if you were up here and you were at
the full range of the stabilator
you would still have this arc of motion
for the elevator
this is what you see on almost every jet
today
is by far the most common because it
allows for that full range of motion
and maximizes our control to control
ourselves in yaw
or around the normal axis we use the
rudder we said earlier that a
symmetrical airfoil
is used for the vertical stabilizer more
commonly known as the fin
and that depending on the direction of a
rudder deflection
our resultant force becomes either right
or left in direction and if it's forced
to the right that'll locate to rotate us
this way
and if it's forced to the left it'll
rotate us this way when we use the
foot pedals to deflect the rudder the
aircraft nose
will yaw towards the fruit that you have
pressed
so if you press the left foot down it
will deflect this surface
to the left hand side it'll essentially
pull this over to this way
like this and it will generate a force
out to the right
if you continue to hold your foot down
when you fly through the air
you will have the relative airflow
hitting the
fin at an angle like this this means
that a local
angle of attack is formed between the
control
surface and the fin and the relative
airflow if we were to release
our fruit and realign everything
we would see that this local angle of
attack here
means that we create a force this
direction
if you think about this as a normal
aerofoil
the angle of attack produces a reaction
force in this direction
this force will then restore this
yaw moment back to its original state
before we pushed in the
foot and made this deflection happen
hopefully you can see now why it's
called a vertical stabilizer
any airflow coming in from any direction
other than straight on
causes a local angle of attack and
generates a force that will try and
restore the aircraft back to the point
where the airflow is aligned
this is the same way as the horizontal
stabilizer or tail flame works
for us in pitch as well so important
point to note is because
the rudder and fin rely on airflow and
sort of angles of attack
it is possible that this airflow becomes
way too steep
and the fin stalls it's a bit strange to
think about the first time because
when you're talking about stalling
you're normally associated with the
pitch of an aircraft
but this is essentially stalling in a
different dimensional plane in this sort
of vertical plane
this can become an issue when flying
asymmetrically that means one engine is
out and one engine is on because that
all causes a yawing motion
we'll look at this at further detail in
future classes
but essentially to counteract this risk
of fin
stall there's a rudder trim system
installed and it's the same as the
trimmable horizontal stabilizer
but it just rotates obviously in this
axis
instead of the axis controlling pitch
to control ourselves in row or around
the
longitudinal axis we use the ailerons
the pair of ailerons act in opposite
directions
to create unequal amounts of lift on
either wing
which leads to this rotation there's
more left on the left side here than
there is on the right
which causes us to rotate clockwise with
the
left wing going up and the right wing
going down
when the wings are moving through the
air the upward going wing
this case on the left has an upward
component
that modifies the downwash and reduces
the angle
of the relative angle of attack
think about this would be the normal
sort of downwash we add in the upward
motion
takes away and we have this new starting
point here which makes our angle of
attack
lower this means that it actually
fights this lift and reduces the
strength of it
the opposite thing happens on the
downward going wing
so the downward going wing as soon as it
starts rotation
has this added downward component that
gets added to the downwash effect
and that means that our angle of attack
is greater and that means that a
more large amount of lift is produced
and it will fight this downward motion
this phenomenon is known as aerodynamic
damping
because of the added motion of the wings
actually rotating
it resists the rotation itself
another problem with roll is something
known as adverse aileron
yaw the wing that travels
up through the air has more lift that's
why it's traveling up through the air
because it's got more lift it has more
induced drag
and that means that when compared to the
right hand side in this case the
downward going wing
it has a lot more drag than
the downward going wing and that results
in this yawing motion
towards the wing that is going up so you
rotate
up and then you yaw towards it like that
this can be counteracted by
changing the levels of deflection on
either side so that you get
more drag on the aileron that deflects
up the way the aileron deflects up the
way which makes the wing go down
and the aileron deflects down that goes
up it's quite confusing when you're
talking about deflection
and the direction of the wing travel
itself
but essentially you would make this
upward deflecting aileron
on the downward going wing deflect more
to create a larger amount of drag and
have these lines balance out so that it
doesn't yaw
it balances out and it's okay spoilers
are not main controls and so we're not
essential
but you'll see them a lot on large
passenger jets
they are upward extending plates placed
in front
of the trailing edge on the wings upper
surface like this
so this would be your ailerons and your
flaps along the trailing edge
and these plates deflect up the way into
the airflow
usually they have two functions they can
be either used to assist in roll
or as an air brake so to assist and roll
they will deflect
up on the same side as the aileron that
deflects up
or the downward going wing this just
creates a larger
imbalance of lift between the wings and
helps with the rotation
the advantage of this on large aircraft
is that the wings are flexible
and the ailerons can cause a twisting
motion at high speeds
when they generate these large forces so
by moving some of the responsibility to
the spoilers
it means that less force is needed from
the ailerons and twisted becomes
less severe the other function is to be
used
as an air brake more commonly it's
called
the speed brake to do this all the
spoilers will just deflect upwards and
create a large increase
in form drag this increase in form drag
may use to slow down it can
increase the rate of descent or the
angle of descent
and just help with controlling the speed
in general in a descent
the speed brakes become less effective
the slower you fly
because they are essentially parasitic
drag
devices and we know that parasitic drag
varies according to v
squared so at high speeds the difference
in drag
is much more severe than when you're at
low speeds
so to summarize quickly then feel is
generated
because of the opposite direction moment
because when we deflect the control
surface down force is generated
and because there's a distance between
the force and the hinge
resisting moment is caused or a feel
moment is caused
to reduce the effect of this feel moment
we can use aerodynamic balances we've
got
inset hinges which reduce the balance
arm we've got horm balances which create
another moment in front of the
hinge to help oppose the feel moment
and we've got internal balances which do
the same thing as a hormone balance but
use
air pressure instead we can also use
tabs which are small control surfaces on
the
back of the main control surface
a balance tab causes a rotational
movement in the opposite direction to
our feel moment and therefore reduces
the strength of that fuel moment
an anti-balance tab will actually add to
the feel moment
and it's used to stop us from over
stressing the controls
another thing is the servo tab
and essentially you fly the tab and the
tab will fly the control surface
you deflect this tab down the way it
will lift the whole control surface up
the way
and the overall resultant force will be
down the way
the advantage of this is you only feel
the moment that's in the servo tap
the disadvantage is sometimes this servo
tab doesn't generate
enough force to move the control
surfaces when it slow speeds
so in that case you use a spring tab
and the spring tab will move the control
surface directly at slow speeds and then
at high speeds
will activate the tab and the tab will
there
after fly the control surface and you'll
only feel
the feel from the servo tab
surface here to control and pitch we use
a symmetrical tail plane and an elevator
or a stabilator which is an entire
moving surface
the elevator deflects to create a force
and the aircraft rotates around the
center of gravity
and we trim in order to change the
neutral point
and the best example of a
trim device is a trimmable horizontal
stabilizer where
the whole plane moves and then the
elevator can deflect from that which
means we have our full range of motion
controlling yaw we use a fin and a
rudder deflection
of the rudder will cause a rotation
around
the center of gravity there's the
concept of sideslip which is when air
comes in at an angle and that will
create a local angle of attack
towards the fin and that generating
force
will rotate us in towards the air
flow and correct this side slip
if this airflow comes in at too severe
an angle too high an angle of attack we
can stall the fin
which is very bad for our directional
control
so we need to have some sort of rudder
trim system which will trim the neutral
point
if we are flying asymmetrically but
obviously we're going to learn about
that in future classes
to control ourselves in roll we use
ailerons
and they will create more lift on one
side
and reduce the amount of lift on the
other side to create an imbalance and
cause us to roll
all your controls can be combined in
various ways such as the
v-tail rudder vators and you get
flapper ons and stuff like that as well
spoilers are used
on the upper surface of the wing
and they deflect up the way to either
assist and roll or if they all deflect
up
it will be to be used as a speed break
which will help reduce our speed
and this speed break is way more
effective at high speeds
due to the parasitic drag being
v squared proportional to v squared
you
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