ATPL Principles of Flight - Class 13: Controls.

Summary

In 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

00:00

🛫 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.

05:02

🔍 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.

10:02

✈️ 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.

15:03

📚 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.

20:03

🔄 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.

25:04

🛠 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.

Keywords

💡Control Surfaces

Control surfaces are the movable parts of an aircraft's wings and tail that are used to control the aircraft's movement and direction. In the video, control surfaces are discussed as the primary means of maneuvering the aircraft through the air, allowing for pitch, roll, and yaw movements. They manipulate airflow to create the necessary forces for these maneuvers.

💡Pitch

Pitch refers to the rotation of an aircraft around its lateral (width-wise) axis, causing the nose to move up or down. The video explains that pitch is primarily controlled by the elevator, a control surface at the tail of the aircraft. The elevator's deflection changes the lift distribution, resulting in a pitching moment around the center of gravity.

💡Roll

Roll is the rotation of an aircraft around its longitudinal (length-wise) axis, causing one wing to rise and the other to lower. The video describes that roll is primarily controlled by the ailerons, which are found on the wings. When one aileron deflects upward and the other downward, they create an imbalance in lift, leading to a rolling motion.

💡Yaw

Yaw is the rotation of an aircraft around its vertical (height-wise) axis, causing the nose to move left or right. The video mentions that yaw is primarily controlled by the rudder, a control surface at the tail. Deflection of the rudder to either side results in a yawing moment, turning the aircraft in the corresponding direction.

💡Aerodynamic Balances

Aerodynamic balances are mechanisms used to reduce the 'feel' or resistance experienced by pilots when moving control surfaces. The video explains that these balances, such as inset hinges, horn balances, and internal balances, counteract the feel moment generated by the control surfaces, making it easier for pilots to manipulate them.

💡Trim

Trim is the adjustment of an aircraft's control surfaces to maintain a desired attitude without the need for constant input from the pilot. The video discusses the use of trim to change the neutral point of control surfaces, allowing the aircraft to maintain a set position without further pilot input, which is crucial for reducing pilot workload during flight.

💡Spoilers

Spoilers are devices on the upper surface of an aircraft's wings that can be extended into the airflow to disrupt it, reducing lift and increasing drag. The video mentions that spoilers can be used to assist in roll control or to act as speed brakes, helping to slow down the aircraft or control its descent rate.

💡Stabilator

A stabilator is a type of control surface that combines the functions of an elevator and a stabilizer. The video explains that a stabilator moves as a single unit to control pitch, providing a more efficient way to generate the forces needed for pitch maneuvers compared to a traditional elevator.

💡Adverse Aileron Yaw

Adverse aileron yaw is a phenomenon where an aircraft tends to yaw in the direction of the raised wing during a roll. The video describes how this occurs due to increased drag on the raised wing, causing a yawing moment. Counteracting this requires adjusting the deflection of the ailerons to balance the drag forces and maintain coordinated flight.

💡Servo Tab

A servo tab is a small control surface on the main control surface that moves in the opposite direction to the main surface. The video explains that the servo tab helps to reduce the feel force on the control column by moving the main control surface, thus making it easier for the pilot to manipulate the control surfaces, especially at high speeds.

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