Flight Control. How airplanes are controlled.

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FLIGHT CONTROL

HOW AIRPLANES ARE CONTROLLED

By

Robert Reser


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R. Reser Publishing, LLC

Phoenix, AZ

FLIGHT CONTROL

Copyright TXu 1-736-2942011 by Robert Reser

THIS BOOK IS PROTECTED BY COPYRIGHT LAWS OF THE UNITED STATES AND

INTERNATIONAL TREATIES AND MAY ONLY BE USED PURSUANT TO A PURCHASE

AGREEMENT. ANY REPRODUCTION, COPYING, OR REDISTRIBUTION (PAPER, PRINT,

ELECTRONIC, WORLDWIDE WEB OR OTHERWISE), IN WHOLE OR IN PART, IS STRICTLY

PROHIBITED WITHOUT THE EXPRESS WRITTEN PERMISSION OF:

ROBERT RESER,[email protected],2030E.CAIRO DR.,TEMPE,AZ85282

ISBN: 00-0000000-0
mailto:[email protected]:[email protected]:[email protected]:[email protected]


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Table of Contents

PREFACE ........................................................................................................... IX

INTRODUCTION ................................................................................................. XICHAPTER 1----------------FLIGHT CONTROL ....................................................... 1

Machines and Control.................................................................................... 3Operation in Three Dimensions ..................................................................... 3

Attitude....................................................................................................... 3Forces and Direction .................................................................................. 4Direction in Space Defined ........................................................................ 6

Vectors .......................................................................................................... 7Lift Forces .................................................................................................. 9Thrust Force ............................................................................................ 10Drag Forces ............................................................................................. 10Gravity Effect ........................................................................................... 10Center of GravityEffective Center of Gravity ........................................ 11Balance .................................................................................................... 12Axes of Control ........................................................................................ 13

Flight Controls ............................................................................................. 14Ailerons .................................................................................................... 15Rudder ..................................................................................................... 16Elevator .................................................................................................... 16Horizontal Stabilizer and Elevator Trim .................................................... 20

Engine and Gravity Power ........................................................................... 22Engine-power ........................................................................................... 22

Gravity-power .......................................................................................... 22Summary ..................................................................................................... 22

CHAPTER 2-------INDICATED-AIRSPEED ........................................................ 25

Body-Angle .............................................................................................. 27Angle-of-Incidence ................................................................................... 27Angle-of-Attack ........................................................................................ 27Relative-Wind, Direction of Motion ........................................................... 28Frontal Plate Area .................................................................................... 28Volumetric-Displacement ......................................................................... 28

Attaining Flight ............................................................................................. 29

Indicated-airspeed in Flight ...................................................................... 29What takes place? ................................................................................... 30Indicated-airspeed ................................................................................... 31Attaining and Sustaining Indicated-airspeed ............................................ 32What is speed? ........................................................................................ 33Control of indicated-Airspeed ................................................................... 34Tail and Thrust Loading ........................................................................... 35g Forces/Load Factor............................................................................ 35


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Acceleration or Deceleration .................................................................... 36Cruise Control .......................................................................................... 36Operating Limitations ............................................................................... 37

Summary ..................................................................................................... 37

CHAPTER 3------ENERGYPOWERTHRUST .............................................. 41

Energy and energy sources ......................................................................... 43

How airplanes fly ..................................................................................... 43Transference of energy (Energy Management) ....................................... 44Now what is going to happen? ................................................................. 44Becoming airborne; space flight ............................................................... 44What goes on in space? .......................................................................... 45Sustaining-thrust ...................................................................................... 46Excess-thrust ........................................................................................... 46How do the Controls Work In-flight? ........................................................ 46Maneuvering with coordinated thrust ....................................................... 47Elevator Control in Turns ......................................................................... 48Why do you have to do that? ................................................................... 48

How to do that? ........................................................................................ 48Gravity power effects ............................................................................... 49

Summary ..................................................................................................... 50

CHAPTER 4---------------ATTITUDE .................................................................... 53

Attitude ........................................................................................................ 56Operation in Space .................................................................................. 56What are Attitudes? ................................................................................. 56Attitude Axes ............................................................................................ 57Dimensional Axes .................................................................................... 57Pitch ......................................................................................................... 57

Engine-Pitch! ........................................................................................... 58Elevator-Pitch! ......................................................................................... 58Climb-Pitch! ............................................................................................. 58Climb........................................................................................................ 59Descent .................................................................................................... 60

Pitch Attitude ............................................................................................... 62Maneuvering for Attitude Change ............................................................ 62Maneuvering with Excess and Decreased Thrust .................................... 63Maneuvering from Vy Indicated-Airspeed ................................................ 63Thrust Placement Effects ......................................................................... 63Descending Flight Maneuvering .............................................................. 64

Maneuvering with Gravity ........................................................................ 65Summary: .................................................................................................... 66


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CHAPTER 5------------ATMOSPHERE ................................................................ 69

Atmosphere ................................................................................................. 71Flight and the Atmosphere ....................................................................... 71Air Density and Your Aircraft .................................................................... 71Air Density and the Engine ...................................................................... 72

Engine Power! ............................................................................................. 73

What has happened? ............................................................................... 73Engine Fuel/Air-Induction ......................................................................... 73Small Aircraft Thrust Performance ........................................................... 74

Summary ..................................................................................................... 75

CHAPTER 6-------------VISUAL FLIGHT ............................................................. 79

Visual Flight ................................................................................................. 81Directed Course Visual Flight Control....................................................... 81

Vertical Attitude ........................................................................................ 82Normal Roll/Bank-Turns ........................................................................... 83

Visual Flight Attitudes .................................................................................. 85

Takeoff attitude ........................................................................................ 85Climb attitude ........................................................................................... 85Cruise attitude .......................................................................................... 86Descent attitude ....................................................................................... 87

Approach and Landing Attitudes ................................................................. 88Approach Descent Attitude ...................................................................... 88Roundout Attitude .................................................................................... 89Flare Attitude ........................................................................................... 90Landing/Ground Roll ................................................................................ 90

Summary ..................................................................................................... 90

CHAPTER 7--VISUAL APPROACH AND GO-AROUND .................................. 93

Visual Approach .......................................................................................... 95Base Leg to Final Approach ..................................................................... 96Base Leg to Final Turn Overshoot ........................................................... 96

The Normal Approach ................................................................................. 97Idle-Power Approach ............................................................................... 98Straight-in Idle-Power Approaches ........................................................ 100Crosswind Landing Approach ................................................................ 101Approach Over an Obstacle ................................................................... 102Ground-effect ......................................................................................... 102

The Go-Around .......................................................................................... 103Aborting ................................................................................................. 103Preparing for Abort................................................................................. 103Initiating an Abort ................................................................................... 103Go-Around Situation .............................................................................. 104Abort Procedure ..................................................................................... 104When to Abort ........................................................................................ 105Abort after Touchdown........................................................................... 106The Mindset ........................................................................................... 106

Summary ................................................................................................... 106


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CHAPTER 8---------------LANDINGS ................................................................. 109

Considerations .......................................................................................... 111Roundout and Flare ............................................................................... 111Landing .................................................................................................. 111Normal Landings .................................................................................... 112Touchdown ............................................................................................ 112

Slip ......................................................................................................... 113Accuracy of the Landing Point ............................................................... 113Soft-Field Landing .................................................................................. 113Short-Field Landing................................................................................ 113Landing over an obstacle ....................................................................... 114

Crosswind Landings .................................................................................. 114Crosswind Landing Approach ................................................................ 114Crosswind Landing Touchdown ............................................................. 117Crosswind Landing Control .................................................................... 117Crosswind Landing Rollout .................................................................... 118Crosswind and Tailwind Landing Considerations .................................. 118

Extreme Crosswind Landing Situations ................................................. 118Emergency Crosswind Landing ............................................................. 119High Wind Taxi Operations .................................................................... 119

Summary ................................................................................................... 120

CHAPTER 9-----------------STALLS ................................................................... 123

Stall ........................................................................................................... 125Critical Elevator-Pitched Angle .............................................................. 125Aircraft Pitch Control .............................................................................. 126Stalling ................................................................................................... 126Stall Situations ....................................................................................... 127Common Stall Scenarios ....................................................................... 127Elevator-pitch Trim Stall! ........................................................................ 128Accelerated and Secondary Stall ........................................................... 129Disturbed Air Encounter ......................................................................... 129Upset ..................................................................................................... 130Microburst .............................................................................................. 130Wake Turbulence Avoidance ................................................................. 130Practice Stalls ........................................................................................ 132Stall Training .......................................................................................... 132Stall Recovery ........................................................................................ 134

Summary ................................................................................................... 135


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CHAPTER 10-----EMERGENCY LANDINGS................................................... 139

Acceptance ............................................................................................ 141Select a Site ........................................................................................... 141The Approach ........................................................................................ 141Preparation for Landing ......................................................................... 142The Mental Anxiety ................................................................................ 143

What is Experience? .............................................................................. 143Technique .............................................................................................. 144

LANDING VS CRASHING ......................................................................... 144Continuing the Approach ....................................................................... 145Landing .................................................................................................. 145Extreme Landing Surface ...................................................................... 145Landing on Relatively Smooth Surface .................................................. 146Touchdown ............................................................................................ 146Landing Roll ........................................................................................... 147

Survival...................................................................................................... 147Staying Conscious ................................................................................. 147

Time ....................................................................................................... 147After Stopping ........................................................................................ 148What do you think just happened? ......................................................... 148

Flight into IMC and Visual Disorientation ................................................... 148Lets Review Real Life ............................................................................... 149Summary ................................................................................................... 150

CHAPTER 11------------------------LETS GO FLY .............................................. 153

Taxi for Takeoff ...................................................................................... 155Takeoff Flight ......................................................................................... 155Climbing Flight ....................................................................................... 156Level Flight ............................................................................................ 156Turning Flight ......................................................................................... 157

Changing Altitudes .................................................................................... 157Climb...................................................................................................... 157Descent .................................................................................................. 157Leveling ................................................................................................. 158Descending Flight .................................................................................. 158Approach ............................................................................................... 159Landing .................................................................................................. 159Crosswind Landings............................................................................... 160Emergency Landings ............................................................................. 161

So, How Are Airplanes Controlled? ........................................................... 162Altitude Control: ..................................................................................... 162Indicated-Airspeed Control: ................................................................... 162Acceleration and Deceleration: .............................................................. 163Climb/Descent Control: .......................................................................... 163Landing Control: .................................................................................... 163All Flight: ................................................................................................ 163


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APPENDIX-1-----RECIPROCATING ENGINES ............................................... 167

The Engine ................................................................................................ 167Operating the Machine........................................................................... 167Flight Preparation .................................................................................. 167Airplane Limitations................................................................................ 168Power System ........................................................................................ 169

Ignition System ...................................................................................... 169Engine Fuel Supply ................................................................................ 169Fuel/Air Mixture ...................................................................................... 169Carburetor .............................................................................................. 170Butterfly Valve ........................................................................................ 170Mixture Control ...................................................................................... 170Throttle ................................................................................................... 171Accelerator Pump .................................................................................. 171Carburetor Ice ........................................................................................ 171Carburetor Heat ..................................................................................... 172Oil Temperature and Pressure ............................................................... 172

Engine Cranking and Starting .................................................................... 173Engine Cranking .................................................................................... 173Ignition ................................................................................................... 174Starting Fuel .......................................................................................... 174Accelerator Pump .................................................................................. 175Engine Fire While Starting ..................................................................... 175Fuel Conditions for Starting ................................................................... 175Conditions for Starting ........................................................................... 176

Summary ................................................................................................... 176

GLOSSARY ..................................................................................................... 179

INDEX .............................................................................................................. 195


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FIGURE TITLE Page

1-1 Which way is up? --------------------------------------------- 4

1-2 Lift forces acting on the aircraft.----------------------------- 5

1-3 Force Diagram---------------------------------------------------- 7

1-4 Vector Forces as components of right triangles--------- 8

1-5 Vectors; Forces with Direction-------------------------------- 9

1-6 Forces; Level Cruise Flight------------------------------------ 11

1-7 Elevator-Lift; Balance Forces--------------------------------- 12

1-8 Aircraft Axis; Dimension of Rotation------------------------ 14

1-9 Aileron Controls-------------------------------------------------- 15

1-10 Empennage------------------------------------------------------- 17

1-11 Frontal Plate Area; Vy Cruise-------------------------------- 17

1-12 Frontal Plate Area; Slow IAS--------------------------------- 18

1-13 Frontal Plate Area; Normal Climb--------------------------- 181-14 Wing Profile; Cruise Air Mass Displacement------------- 19

1-15 Wing Profile; Stall Air Mass Displacement---------------- 19

1-16 Wing Profile; High IAS Air Mass Displacement---------- 20

1-17 Elevator-Pitch Trim---------------------------------------------- 21

4-1 Vy Climb from Excess Thrust--------------------------------- 57

4-2 Sustained Climbing Flight------------------------------------- 58

4-3 Sustained Engine-out Gliding--------------------------------- 59

4-4 Engine Mounting Thrust Effect------------------------------- 62

5-1 Aircraft Climb Data---------------------------------------------- 72

6-1 Directed Course Visual Flight Cruise----------------------- 79

6-2 Directed Course Visual Flight Turn------------------------- 82

6-3 Directed Course Visual Flight Takeoff-------------------- 83

6-4 Directed Course Visual Flight High Speed---------------- 84

6-5 Visual Descent--------------------------------------------------- 85

6-6 Directed Course Visual Flight Descent--------------------- 86

6-7 Directed Course Visual Flight Landing--------------------- 87

7-1 Standard Visual Traffic Pattern------------------------------- 93

7-2 Idle Power Approach Pattern--------------------------------- 97

8-1 Crosswind Vector Components------------------------------ 1138-2 Estimating Wind Effect----------------------------------------- 114

8-3 Estimating Wind Effect----------------------------------------- 114

10-1 Engine Failure Landing Pattern------------------------------ 138


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PREFACEThis book does not purport to cover all aspects of required training for a pilot license. It

only presents basic flight control. Some additional information covers a few procedures

not always emphasized in beginning flight training.

It is the opinion of the author that the lack of understanding of basic flight control

and related training to proficiency is a primary cause of the continued fatality rates fromincidents and accidents. Additionally, review of incidents and accidents should go

beyond the cause but the continued control through any cautionary or emergency

approach and landing. It is the landing that causes fatalities, not necessarily the cause

of the incident.

There are numerous ways to present and discuss the different aspects of flight

and flight control. It is usual for a pilot to be able to fly quite well, even without an

understanding of the real cause and effect of the aircraft controls.

There are many excellent books and articles written for pilots about methods and

techniques for conducting safe flight, but the industry continues to have the same basic

accidents and incidents.

The most highly trained and proficient authors, publishers, and instructors can

only profess safe flight conduct. Students rely on those actually teaching to attain that

standard of proficiency. It is unlikely more than a small percentage of instructors have

that ability.

Something is missing! I suspect it is the initial flight training. The majority of

Students are taught by instructors who themselves have been trained by minimum

schooled instructors. Training to minimum standards is the basis of the system!

Most private pilot training directs to passing the checkride. Its just the way it is,

but private pilots are the majority of pilots and are those flying single engine aircraft.So, who should know how to make engine out landings??

Attempts to regulate away accidents have been futile. There appears to be

unintended consequences of increased and stricter regulation from the past few

decades. In the past, most students initially learned landings using idle-power.

Deeming it safer, the power-on approach became the standard.

The safer approach was an attempt to regulate safety. The cause of the

unsafe approach was not determined. Even today, forty years later, the unsafe

approaches have no solution and the safer approaches continue having the same

problems as the unsafe procedures.

Demonstration of the idle-power approach is no longer required for a private

pilot. That just happens to be the technique for engine out landing. Note, teaching of

idle-power approaches is encouraged, they are not required to be demonstrated by the

private pilot so are often left out of proficiency training. The procedure has died, and

now not required before the commercial license.

This book emphasizes understanding control and development of technique the

author deems often missing in current flight training. Few pilots understand the basic


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effects of pitch, the elevator, and elevator control for indicated-airspeed, engine thrust

for lift, and proper control input for attitude control.

The procedures necessary for making emergency landings are not well understood,

especially for private pilots. The statistics of stall crashes confirms this every day. If

this book saves one life, then it was worth it!


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INTRODUCTION

In this book, the emphasis is on how aircraft are controlled and safe flight from proper

control. It is from study of proper control, all pilots will better understand the control

input and response required for flight. Specific procedures and individual operational

technique are not considered. There is little reference to aircraft design theory. The

pilot deals with the aircraft as built.

All aircraft operate in the same manner and the same physics applies. Although

this book is generally directed to the Private Pilot and Student Pilot, the theory of flight

control applies to all aircraft, and will answer basic questions about aircraft control for

any level of piloting.

All professions have their language. It is important all pilots be familiar with the

same terminology of flight. In this book, there is corrected terminology, such as pitch

and indicated-airspeed, as well as new terms such as directed course, sustained

thrust, and excess thrust, which more adequately explain most functions of flight

control. All new terminology is included in the expanded glossary.There is continued use of certain terms to insure complete understanding. Used

inter-changeably are the terms for motivation, power, thrust, thrust force, and

power thrust. Also used throughout is indicated-airspeed, it is not speed or

airspeed; those are measurements of distance over time. Flight and structural

limitation control are Indicated-airspeed, pressure-speed, indicated pressure-

speed. There is a huge difference, just an unfortunate name.

The conduct of most flight is at some recommended cruise flight or above. This

allows pitch control response from the engine or the elevator to be similar when

initiating a maneuver (attitude change). For this reason it is common for a Pilot to think

in terms that the elevator causes climb and increased power causes acceleration.

The actual control response required is that response obtained when operating at Vy

indicated-airspeed.

This book is written initiating attitude change or maneuvering from a wings level,

Vy constant indicated-airspeed, and constant altitude flight.

The significance of this indicated-airspeed is that it is an optimum starting point.

It is the most efficient attitude of the aircraft at its current coordinated condition. Any

change of attitude or altitude other than descent will require increased engine thrust. It

will require added thrust to reduce indicated-airspeed in level flight as well as added

power to increase indicated-airspeed.From this starting point, we will discuss how to utilize the flight controls, engine

thrust, and elevator trim.


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The first five to ten hours of flight training should teach a pilot how to control an

aircraft safely. After that, training becomes what to do with the aircraft while

continuing practice and gaining of experiences from the different aspects of the flight

training.

Chapter one introduces flight control and related control and force effects.Chapter two is discussion of indicated-airspeed, how it is determined, what it

means, and how it is controlled.

Chapter three discusses energy, power, thrust and how they apply to flight

control.

Chapter four discusses operation in space, flight attitudes and orientation.

Chapter five discusses atmosphere and its effect on engines in flight.

Chapter six is discussion of visual flight with directed attitude control.

Chapter seven presents visual flight final approach and go-around.

Chapter eight is about landing and different types of approaches to landings.

Chapter nine presents stall scenarios, avoidance, practice and recovery.Chapter ten discusses emergency landings and surviving the landing.

Chapter eleven discusses operation of typical aircraft in flight. What can a pilot

do?


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Chapter 1----------------Flight Control

This chapter discusses basic aircraft controls and concepts of flight.

The Machine

The Flight Controls

Angle-of-attack

Horizontal Stabilizer and Elevator Trim

Engine and Gravity Power

Summary


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Machines and Control

Flying aircraft is not a science. It is simply operating a machine. There has been a lot

of discussion about how an aircraft flies, but designers and manufacturers built it to do

just that...fly! We want to control the flight.

An operator of any machine must learn its specific procedures, methods, and

limitations. Aircraft have their operational requirements just as any other machine.

It is during the learning process of how to use the machine one must understand

why things happen. When understanding, you have then learned when and how safely

to apply the required controlling inputs.

Development of operational techniques and habits takes place during the

process of flight training. Instructors have their own techniques for input of control.

You will develop and learn those techniques that work for you. Technique is an

individual thing, which changes with experiences throughout a career as you gain

increased knowledge, understanding, and proficiency.

Operation in Three Dimensions

An airplane is a machine operated by a pilot. The pilot doesn't really fly the plane

because that is its design. It is operational control and direction by the pilot that allows

flight.

In the air or on the ground, there are some different basic concepts to

understand.

Attitude

On the ground, steering a plane is similar to driving an automobile. It is just that control

is opposite; you steer with your feet and accelerate pushing a hand throttle.

Upon attaining flight, you are in the dimensions of space; this is a new concept.Suspended in the air, the aircraft can move in three directions. The attitude of the

aircraft can be in any orientation relative to the earth; however, no matter that attitude,

sensing of flight control response is relative to you, the pilot, sitting in the machine.

It is a new sensation to be able to move within the three dimensions of space,

but easily accommodated after the first few flights. All normal flight is in general upright

attitudes. Introduction of extreme attitude flight occurs after attaining proficiency in

basic upright maneuvering.

The aircraft responds to control with changed attitude relative to the earths

surface. Your control inputs are to or away relative to the cockpit.

The aircraft could be in a nose high climbing turn, or even inverted, yet thecontrol response will always be to or away between the machine and you sitting in the

cockpit.

There will always be a small pitch-up angle called angle-of-attack of the attitude

relative to the direction of motion. The angle-of-attack and aerodynamic form with

velocity through the airmass cause reactive lifting forces and resulting attitudes,

indicated-airspeeds, and altitudes the aircraft will fly.


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It is not usual, but possible, to fly inverted. Level inverted flight will only happen

with specially designed and powered aircraft. This is a special case of the attitude

being nose down relative to the pilot, but being upside down the pitch angle will still be

up relative to the direction of gravity. The aircraft will be causing lift upward from the

bottom of the aircraft and the pilot experiencing negative gravity force will be hanging

by the seat belt.

No matter the attitude, pulling

the elevator control pitches

the nose to the Pilot!

Which Way is UP?

Figure 1-1

It is possible to attain unusual or inverted attitudes in any aircraft, but without

sufficient power, these attitudes will be momentary while controlling back to an upright

attitude. Since there would likely not be enough engine power, or control response

available to recover during the time required for this maneuvering to take place, expect

considerable altitude loss and rapid acceleration from gravity. These attitudes would

be unusual, and seldom, if ever, experienced in small aircraft.

Forces and Direction

An aircraft moving through space is displacing its volume of that airmass. The resulting

pressures of rapid displacement of mass-of-the-air, from motion, causes a reaction

from the aerodynamic form of the machine creating lift forces directed outward from the

top of the machine. This is aerodynamic lifting. In all flight, direction of aerodynamic lift

is outward from the top of the machine and negative aerodynamic lift outward from the


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bottom. The direction of aircraft lift relative to the earth will change with any attitude

change.

Your aircraft forward motion through an airmass generates reactive lift forces

due to its aerodynamic form. It then requires a continuous sustained velocity to

maintain flight.

Mass, Weight due to Gravity Force

Weight Force acts toward the Center of the Earth.

Elevator Aerodynamic Lift

can be positive or negative,

upward or downward

LIFT FORCES ACTING ON THE AIRCRAFTAll Lift Forces act outward from the Top of the Structure, no matter the Attitude.

Engine Lift Acts Perpendicular to the Direction of Motion

Aerodynamic Form Lift Acts Perpendicular to the Longitudinal Axis

Elevator Lift Acts Perpendicular from Elevator Position, Directed Positive or Negative

Direction of Motion

Fig: 1-2

Drag

Analysis of the forces considers them acting on the aircraft as if all originated at

a point. Aerodynamic lift is reactive force from airmass displacement around the form

directed outward from the top and considered acting from a point called the center of

aerodynamic lift. Engine-lift acts outward from the top at its point of attachment, and

aerodynamic lift from elevator

position acts outward from the top or bottom of the horizontal stabilizer.

The aircraft has the continuous downward vertical force of gravity acting upon itat the center of mass. Gravity force is always vertically downward, directed toward the

center of the earth. A vertical component of total aircraft lift must always balance the

gravity force to sustain flight.


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Direction in Space Defined

When operating an aircraft it requires understanding the meanings of specific terms. A

few common terms are considered.

Consideration of flight control forces will be toward or away from the aircraft.

The aircraft attitude can be in any orientation so forces related to the aircraft will be

forward, rearward, and outward from the top or bottom. Reference to the machine or

the earth requires careful distinction.

up/down is direction or travel away from or toward the surface of the earth.

Now we will say the directionup/down is not only vertical, but also related to

any component of travel away from the top or bottom of the aircraft when referring to

the machine.

Aircraft pitch control is causing movement of the nose up or down relative to the

pilot. Pitch controlling is To (toward) and can be engine powered pitch increase or

elevator-pitch by pulling the elevator control, causing the nose of the aircraft to pitch up

outward toward you. Away is when reducing engine powered pitch, or pushing the

elevator control causing decreased pitch. The nose moves outward away or downrelative to you sitting in the cockpit.

Outward is direction away from the aircraft top or bottom, and Upward is

direction away from the earths surface, while Downward is direction toward from the

earths surface.

Vertical is a positive direction perpendicular away from or negative direction as

a reference to the aircraft or the center of the earth. Exercise care to assure proper

reference.

Upright is an attitude at which all lift force is directed above the horizon, and

Inverted is with the lift force directed below the horizon.

Gravity (g Force) is the negative vertical force of potential energy acting onthe aircraft mass and directed toward the center of the earth. All reference to gravity

force effect on mass is toward the center of the earth. When related to the aircraft it is

from the aircrafts center of mass.

Load Factor is the change of induced loading as related to the mass of one

g, the weight of the aircraft. Airborne maneuvering can cause structural loading in

excess of the mass weight. For instance, the 1.4 g aerodynamic loading on the

structure in a 45-degree turn is a load factor 1.4 times the mass weight of the aircraft

and directed opposite the direction of aerodynamic lift. In addition, direction of elevator-

pitched aerodynamic loading can be outward from either the top or bottom of the

horizontal stabilizer.


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VERTICAL COMPONENT OFAERODYNAMIC LIFT FORCE

THRUSTFORCE

DRAGFORCE

Level Constant Speed Flight

Thrust equals Drag and Lift equals Load

The depicted vectors are not proportioned relative to actual aerodynamic forces involved.(Approximately one lb. thrust will generate ten lbs. of lift,

i.e. approximately 200 lbs. of thrust sustains a 2,000 lb. aircraft @ Vy airspeed)

MASS LOAD

Fig. 1-3

AERODYNAMIC LIFT FORCE

Vectors

Flight requires sufficient continuous forward motion of the aircraft to cause enough

vertical lift to balance the opposing continuous negative directed force of gravity.

No matter the attitude, the direction of all aerodynamic lift, and engine thrust

component lift, outward away from the top of the aircraft, in some way must

continuously balance the mass weight to avoid descent.

The forward directed, horizontal component of engine thrust causes the required

motion to sustain level flight. This sustaining thrust force will equal the opposing drag

forces for constant indicated-airspeed flight.

The language for understanding how the different thrust, drag, lift, and load

forces act on the aircraft requires understanding and consideration of force vectors.

Reference to flight forces will have components, both vertical and horizontal,

related to aerodynamic lift, to the aircraft thrust, or the direction of the gravity force.A Vector is a force in a direction considered as a combination of two smaller

component forces acting 90 degrees from each other or conversely, two forces, acting

90 degrees from each other causing a resultant total force in another direction.


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VECTOR FORCES as COMPONENTS of RIGHT TRIANGLES

The forces acting on the airplane: A force can be considered as the effect of two separate

component forces acting ninety degrees to each other.

Common values used by pilots for wind component calculations are rounded to the nearest

tenth and include the 30/60/90 triangle with long leg .9 and short leg .5. The 45/45/90

triangle has two legs of the same length at .7. In all cases the third or resultant leg is 1.0 as thebase value.

Common values for load and lift considerations to understand flight forces are 6/84/90

triangle of a 6 degree angle of attack normal cruise. The short leg is .1 and the long leg is .995.

Slow flight 12 degree legs are .2 and .978.

Fig. 1-4

All triangles have three inside angles

which always total to 180 degrees.

Vector analysis is based on the legs of right

triangles. A right triangle always has an

inside angle of 90 degrees. The other two

angles add to another 90 degrees. The 30/60

right triangle is a 30/60/90 triangle when

adding the sum of the included angles.

There are fixed ratios of the two smaller legs

of right triangles, which allows computing

any leg if the two others are known or a leg

and its included angle.

30

6090.5

.9 .7

Component of Vector Force

ComponentofVectorForce

45

4590

.7

Most consideration of the forces acting on your aircraft is of component forces in

horizontal and vertical directions. The sustained horizontal and vertical components

from engine angled thrust force, the aerodynamic lift forces, and retarding drag forces

maintain the resultant aircraft attitude, and motion in flight.

Your principal concern is maintaining the operational lift forces within the

indicated-airspeed pressure limitations imposed by the aircraft manufacturer. This is

the only reference you have of lift.

At a specific trimmed indicated-airspeed, if the airplane is flying, you have

sufficient lift. If you are climbing, you have some excess thrust applied shown in the

cockpit as increasing altitude and positive climb rate. If you are descending, you have

reduced power to less than the level flight sustaining engine thrust with decreasing

altitude and negative climb rate.The aircraft continues to fly with reduced power by using a horizontal component

of gravity force to sustain the required velocity for lift. However, it requires descent to

do this. Available altitude then limits your descent.


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Lift Forces

It requires vertical lift components of the total aerodynamic, and engine force vectors,

equal to and opposite the downward vertically directed negative gravity force, to enable

maintaining constant altitude flight.

The aircraft lift, created by the wings and fuselage, is always directly out the top

of the machine, but your aircraft attitude is always flying at some small angle to the

surface.

The top of the aircraft, the direction from which the aerodynamic lift acts, has

force components of lift, both vertical and horizontal, acting 90 degrees to each other.

There is a large vertical component of lift holding the weight of the aircraft mass with a

smaller horizontal component, representing the drag forces, directed toward the rear of

the aircraft opposite the direction of motion.

The engine thrust is also at this small angle from horizontal. Therefore, there

are force components, vertical and horizontal, acting 90 degrees from each other there.

This results in a small outward force from the top, contributing to the total lift, and the

larger horizontal thrust opposing the drag force.

12

.97815

.2

VECTORS

FORCES with DIRECTION

Figure 1-5

sine 6=.1

cosine 6=.9945

6525

.9 In-flight AircraftLevel, Constant Indicated-Airspeed

1,599# Aerodynamic Lift

159 Horizontal

Thrust

1,590#

Vertical Lift

16# Thrust

Vertical Lift160# Engine

Thrust

6 angle of attack

159# Drag

1,600# Mass

Weight

-8#

8# NegativeAerodynamic

Elevator Lift

Thrust equals Drag, no net change ofIndicated-Airspeed.

Lift equals Load, no net change of

Altitude

10 Moment Arm

20 Moment Arm


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The elevator and horizontal stabilizer trims control pitch for longitudinal balance

of the total aircraft attitude. This creates small upward or downward aerodynamic lift

components lever moments on the tail as necessary to maintain the aircraft balance

around the center of gravity. Change of elevator aerodynamic loading is generation of

a force, often negative, adding some small load force lever moment or if positive adding

some small lift force lever moment.

Thrust Force

The engine power provides thrust force for motivation. Thrust is always in the forward

direction the aircraft is facing. Flight control maneuvering of aircraft attitude with rudder

and pitch steers this thrust force. Gravity provides a continuous thrust force directed

from the center of mass toward the center of the earth.

Reducing below sustaining engine power or maneuvering to a descending

attitude will allow gravity thrust to add back to the sustaining thrust for maintaining the

trimmed indicated-airspeed.

There will always be a continuous thrust force sustaining the motion causing the

required mass-of-the-air displacement for lift generation at any given indicated-airspeed

and configuration. At all times, in flight, there will be sustaining engine thrust to cause

continued level or climbing flight or thrust added by gravity with descent.

The actual thrust required for a specific aircraft varies considerably depending

on the designed aerodynamic form. Smaller aircraft sustain flight at approximately one

pound of engine thrust for each 10 pounds of weight (1:10 ratio). A 1,600-pound

aircraft will then require approximately 160 pounds of engine thrust to sustain itself at

its optimum level indicated-airspeed.

This aircraft at that optimum indicated-airspeed will be at an upward

encountering angle of at least 6 degrees angle of attack, so will have a continuous 16-pound or more outward force acting from this power source as a component of thrust

(sine 6= .1) and contributing to the total lifting forces. This engine-lifting will act as a

moment-lever around the center of gravity balanced with the elevator-pitch setting to

maintain the angle of attack. Some understand this as teeter-totter balancing.

Drag Forces

Drag force results from the different pressure and frictional forces of the airmass

resisting the aircraft forward motion. For sustained constant indicated-airspeed flight,

engine thrust will equal drag. When thrust and drag are equal, there is no net increase

or decrease of indicated-airspeed.Attitude change redirects aerodynamic lift, so the retarding component force,

drag, will change when maneuvering.

Gravity Effect

For all flight, there is always a specific velocity for causing sufficient aerodynamic lift at

an indicated-airspeed. When airborne, it is not possible to stop, so attempting to slow


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by reducing below the level flight sustaining engine thrust, there will be descent.

Gravity will always cause continued motion, either sustaining the lifted flight with

controlled descent, or if stalled, uncontrolled falling until reaching the surface.

6

Level Cruise Flight6 Aircraft Angle of Attack160# Sustaining Thrust

Engine Vertical Thrust 16#Total Aerodynamic Lift

Vertical Component of

Aerodynamic Lift at a

Center of Pressure

Mass Weight

Aircraft Load

Aerodynamic

Tail Loading

H o r i z o n

Relative WindDirection of Motion

Vertical Component

of Thrust = 16#

Drag

Figure 1-6

Horizontal

Thrust

Center of GravityEffective Center of Gravity

A center of gravity is the point on a system that all the mass is equally balanced and for

discussion of vector forces, the point from which the force of gravity acts on the total

mass.

The aircraft is loaded with a static center of gravity (center of mass) deliberately

placed slightly ahead of a theoretical center of total aerodynamic lift. Once in flight,

control of the elevator directs aerodynamic loading moments at the tail and the

coordinated engine vertical lift component moments of thrust, to balance the aircraft at

a desired indicated-airspeed.

Elevator loading and engine-lifting change the total aircraft loading, thereby

creating an changed or effective center of gravity necessary to maintain aircraft

balance. Change of elevator aerodynamic loading and engine-lift cause this change of

the center of gravity just as if it were a position change of mass.


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These effects are a small change of the location to an in-flight effective center of

gravity, so there becomes a slightly different center of vertical lift anytime the elevator

loading is changed.

There is no way for you to know specifically where the total aerodynamic lift will

occur. You load the aircraft according to weight moments originally calculated by

design engineers. Once in flight, controlling elevator-pitch to a desired indicated-

airspeed sets an effective center of gravity.Pitch control changes the attitude of the aircraft with a corresponding change of

the location of the effective center of gravity. The result is an angle-of-attack change

for a new indicated-airspeed while the direction of motion remains constant.

= Static Center of MassCG = Center of Gravity

W = Mass Weight

CP = Airborne Effective CG

E = Elevator Aerodynamic Lift

A = Body and Wing Form

Aerodynamic Lift

V = Vertical Lift Component

T = Engine-Thrust Vertical Lift

= Airborne effective Center

of Gravity.

T

W

W

W

CP

CP

CP

CG

CG

CG

T

T

E

E

E

Fig: 1-7

ELEVATOR-LIFT

BALANCE FORCES

A

A

A

Increased Elevator Aerodynamic

Lift Decreases Angle of Attack

while moving the effective Center

of Gravity Forward.

Slow Flight

Cruise Flight

High Airspeed

Flight

V

V

VNegative Lift

Neutral Lift

Positive Lift

Balance

When airborne, your aircraft is floating, suspended and balanced around an effective

center of gravity created by the elevator aerodynamic loading and engine-lifting. This

requires longitudinal balancing of the aircraft with elevator-pitch control and associated

coordination of thrust for any related indicated-airspeed.


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Placement of the initial mass loading is within designed limits at which the

aircraft controls can develop sufficient aerodynamic forces for maintaining the balance.

The outward directed forces in flight are the aircraft aerodynamic lift of the wings and

fuselage, the aerodynamic lift of the tail surfaces (elevator and horizontal stabilizer),

and the outward component of engine thrust force from its inflight pitched attitude.

When in a stabilized, constant indicated-airspeed, constant altitude condition, all

outward forces have been coordinated by adjustment of engine power/thrust andelevator-pitch to maintain the condition.

The engine is providing a coordinated constant thrust force with a horizontal

force component sustaining the motion forward and a small outward component force

from the top of the engine thrust location due to the slight pitched up angle-of-attack

attitude. The engine thrust component of lift acts at its source. This can be from an

area near or along the fuselage or tail with jet thrust and rear mounted engines.

The elevator-pitch aerodynamic load adjustment, with its longer moment arm,

maintains the desired indicated-airspeed with a small aerodynamic force, which can be

in a positive or negative direction. Stabilized flight occurs with coordination of thevertical component of lift from the engine powered sustaining thrust and the elevator-

pitch trimmed aerodynamic lift together establishing a desired angle-of-attack indicated-

airspeed.

Axes of Control

Control is for maneuvering and requires coordination of the thrust and flight-control

forces to cause change. All attitude change requires added power coordination for

maintaining the required vertical components of total lift force to prevent descent by

gravity.

When airborne, maneuvering is around axes of rotation, relative to a currentcenter of gravity. The maneuvering axes of rotation of your aircraft are three imaginary

lines, perpendicular to each other, referenced to the machine.

There is the longitudinal axis, which passes through the length of the fuselage in

direction of motion, the vertical axis up and down through the top and bottom of the

fuselage, and the lateral (transverse) axis, which passes through the sides of the

fuselage. These lines intersect at the current effective center of gravity, and relate to

the maneuvering of your airplane.

These things are nice to know. You have no idea where the effective center of

gravity is located at any time. You have no idea the aerodynamic load caused by the

elevator. You have no idea the outward lift of the engine. This is just how it happens.You fly the airplane with adjustment of power and controls to get the response

necessary to maintain safe and efficient indicated-airspeed as read on the IAS

indicator. You will never consider these elements of flight when actually inflight.


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AIRCRAFT AXISTHREE DIMENSIONS OF ROTATION

Vertical Axis--Yaw Axis

Rudder Control yaws (steers) the

nose side to side controlling thedirection of thrust.

x

y

z

An Aircraft can be maneuvered into any desired attitude.

If the power available cannot sustain an attitude, gravity

will add with descent to a new attitude !

Figure 1-8

Flight ControlsThe aircraft flight controls, the Ailerons, Rudder, and Elevator, maneuver the aircraft in

three dimensions with aerodynamically generated forces.

These flight controls are panel devices hinged to the backsides (trailing edges)

of the aircraft wings and empennage. The empennage is the tail of the aircraft and all

its components, consisting of the vertical and horizontal stabilizers with the rudder and

elevator. The stabilizers enable maintaining flight stability somewhat similar to feathers

on an arrow, but are controllable for inputting attitude change.

Pilot input to the flight control devices deflects the control panels into the

airstream. This deflection causes aerodynamic reactive force for moving the aircraft

attitude relative to the input direction.

The forward edges of the aircraft flight surfaces are the leading edges. The back

edges of surfaces are the trailing edges of the surfaces.


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Ailerons

The ailerons are movable surfaces mounted along the trailing edge toward the outer

end of the wings. Turning of the control wheel in the cockpit controls the rate and

extent of roll attitude change.

When turning the control wheel, the ailerons move in opposite directions into the

airflow to increase lift on one wing, and decrease lift on the opposite wing.

Turning the control wheel counter-clockwise will cause the aircraft attitude to

roll/bank to the left, and turning clockwise, the aircraft attitude will roll/bank to the right.

When your aircraft is flying at a wings level, constant altitude attitude, there is a

vertical lift component force out the top of the aircraft directly opposing gravity. A

rolled/banked attitude of your aircraft changes the direction of that lift force out the top

of the aircraft. This change causes a reduction of the vertical lift component forces, so

the aircraft will begin descent without added power to maintain a constant vertical

component lift force. The deflected aileron of the outer wing causes some retarding

drag to the turn. Coordinated rudder thrust steering is often required to compensate for

this drag while deflecting the aileron.

AILERON CONTROL

Aileron control allows maintaining the wings level and controlling

into rolled or banked attitudes by opposite deflection on the

wings to create changed lift.

Left Aileron Up reduces lift on the left wing

Right Aileron Down increases lift on the right wing

In this depiction the Control Wheel is turned counter clockwise to cause Roll

to the Left. The Ailerons move in opposite directions with control input.

Figure 1-9

.


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A 30 degree banked level turn will cause a 1,600-pound aircraft to respond as if

it weighs 1840 pounds (cosine 30= .866). This is an equivalent aerodynamic lift

requirement of 2,136 pounds requiring an increase of 54 pounds of engine thrust, so

the coordinating power must be increased while in this attitude.

The rolled/banked attitude of your aircraft, with the changed direction of the lift

has also created a horizontal component of the lift force. This horizontal force

component of lift turns the aircraft (sine 30= .5). In this case, 1155 pounds ofaerodynamic force is changing the direction of flight.

The thirty degree banked level turn has caused a 1.15 g structural load on the

aircraft.

Rudder

The rudder is a movable surface mounted on the trailing edge of the vertical stabilizer.

It deflects from side to side into the airflow by pilot input to foot pedals.

Most aircraft have individual main wheel braking and nose-wheel steering

associated with the rudder pedals for ground operation steering control and braking.

Pushing the left rudder pedal deflects the rudder control surface to yaw/steer the

nose to left, and pushing the right rudder pedal deflects the rudder control surface to

cause the nose to yaw/steer to the right.

The engine is always creating thrust in the forward direction the nose faces.

Changing the direction of the nose changes the direction of thrust force. Rudder

control is side-pitching of thrust.

The rudder then steers the aircraft by yaw. In a turn, caused by roll/banking with

aileron, rudder input coordinates any adverse forces by steering the thrust force

throughout the turn. In a rolled attitude, the rudder then creates a small pitching force

component if held in a deflected position.For ground operation, all taxiing from the ramp to lift-off and landing touchdown

to parking, rudder steering controls directional motion.

Elevator

The elevator is a movable control surface attached to the trailing edge of the horizontal

stabilizer. It deflects into the airflow by pulling and pushing the control wheel. This

causes the nose to move to and away from you as a pitch attitude change of the

forward movement of the aircraft. Pilot input to the elevator control is the elevator-pitch

attitude control.

Pulling the elevator control causes a small aerodynamic increased (negative lift)loading to occur on the tail surface. Changed loading changes both, the balance of the

aircraft and total effective loading. It causes a small rotation around the lateral axis to a

new lift pressure point (effective center of gravity).

Increased deflection of the elevator creates negative directed aerodynamic lift on

the tail outward away from the bottom of the aircraft. The direction of flight motion does


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The aircraft empennage is the tail of the aircraft and consists of the horizontal and vertical

stabilizers. Attached to the trailing edges are the elevator and rudder control surfaces.

These controls are used for stabilizing up and down pitch angle and side to side steering

yaw of the aircraft movement.Trim tabs are small adjustable controls which are used to balance individual control forces

for ease of operation for the pilot.

Figure 1-10

Horizontal

Stabilizer

Elevator

Rudder

Vertical

Stabilizer

Elevator

Trim Tab

Leading Edges

Trailing Edges

EMPENNAGE

Wing Frontal Plate AreaBody Frontal Plate Area

FRONTAL PLATE AREAVy INDICATED-AIRSPEED6 Degree Angle of Attack

The Frontal Plate Area is the equivalent flat plate area that encounters the airstream.

It consists of wings, fuselage and elevator. The Frontal Plate Area varies with the

angle (Angle of Attack) at which the aircraft meets the air mass .

Large frontal areas at slow airspeeds require less pressure per square inch to provide

required vertical lift. High airspeeds provide higher pressures so require less angle ofattack.

Relative Wind

Free Airstream

Fig. 1-11


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FRONTAL PLATE AREASLOW INDICATED-AIRSPEED

12-15 Degrees Angle of Attack

Body Frontal Plate Area

Wing Frontal

Plate Area

The Frontal Plate Area is the equivalent aircraft underside area that encounters the

airstream. It consists of wings, fuselage and elevator. The Frontal Plate Area varies

with the angle (Angle of Attack) at which the aircraft meets the air mass .

Large frontal areas at slow airspeeds require less pressure per square inch to provide

required vertical lift. High airspeeds cause higher pressures so require less angle of

attack to cause the same lift.

Elevator Frontal Plate Area

Positive or negative loadedRelative Wind

Free Airstream Fig: 1-12

Direction of Motion (Travel)

FRONTAL PLATE AREA NORMAL CLIMB INDICATED-AIRSPEED

Pitch Angle 12 Degrees; 6 Degrees Angle of Attack, 6 Degrees Climb Angle

Body Frontal

Plate Area

Wing Frontal

Plate Area

The Frontal Plate Area varies with the angle (Angle of Attack) at which the

aircraft meets the air mass .

Large frontal areas at slow airspeeds require less pressure per square inch to

provide required vertical lift. High airspeeds provide higher pressures so

require less angle of attack to cause the required reactive lift generation.

Relative Wind

Free-stream AirFig: 1-13

6

6

H O R I Z O N


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WING PROFILE

Frontal Area/Airmass Displacement Area

--OPTIMUM CRUISE

8 angle of attack

Fig 1.14

The larger amount of accumulated airmassdisplacing under the wing provides a riding

cushion for the aircraft.

The replacing airmass over the top of the wingresults in reduced pressure over the wing area.

WING PROFILE

Frontal Airmass Displacement Area

--APPROACHING STALL--

Large angle of attack

Fig. 1-15

.

Partial Void

Very high nose, angle of attack approaching a stall. The area of displaced air over the top of the wing is

too large to be completely replenished with displaced air. Induced drag from increased encountering

pressure of having to displace large volumes of airmass are more than the engine thrust available can

produce. The voided area gradually moves forward until no lift remainsa stall.

Large Cushion of Displacing Air

creates increased induced drag forces


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3 Angle of Attack

WING PROFILE

Frontal AreaAirmass Displacement Area

--HIGH INDICATED-AIRSPEED--

Fig. 1-16

not change significantly, though without coordinated adjustment of engine power,

altitude will change, as gravity force will do the power coordinating for you.

The new attitude of increased elevator-pitched angle is an increase in the front

profile of the fuselage and wings encountering the air-stream.

This increased frontal area of the aircraft results in an associated increased

volume of displaced airmass allowing the aircraft to decelerate as it will require less

airmass encountering pressure per square inch to develop total lift.

Elevator-pitch determines aircraft angle-of-attack, the angle of airmass

encounter, and a resultant indicated-airspeed flown.

A reduced indicated-airspeed allows maintaining the constant vertical lift as the

increased frontal area (square inches) and reduced airmass displacement pressure

(per square inch) are coordinated with thrust change.

Horizontal Stabilizer and Elevator Trim

The elevator itself has a manual trimming mechanism, which enables setting a constant

attitude elevator-pitch by changing the elevator control neutral position. That allows the

aircraft to fly at a constant indicated-airspeed with minor pilot elevator control input.

Elevator-pitch can be set manually with control wheel input, but is not convenient

since it would require you to hold the control in the same position for long periods.

Therefore, you can use adjustment of the elevator trim control to set a fixed elevator-


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pitch angle at the elevator control neutral position to maintain a desired indicated-

airspeed angle-of-attack.

Some aircraft have moveable horizontal stabilizers, which trim in a similar

manner as the elevator trim control. These systems change the angle-of-attack of the

horizontal stabilizer and result in the same control as trimmed elevator-pitch.

An interesting thing about an elevator-trim control setting is that it does not

change without the pilot resetting the control. If controlling the airplane with manualelevator-pitch control input and then releasing that manual input, the aircraft will attempt

to resume the indicated-airspeed related of the current elevator-pitch trimmed position.

It is like a cruise control.

Therefore, you have an indicated-airspeed set. The aircraft is doing just fine all

by itself. With a coordinated power setting maintaining a desired altitude, you can fly

essentially hands-free.

Elevator Trim Tab

Elevator-pitch (nose up)

Back Elevator Control rotates the elevator trailing edge up into the airstream causing

downward force on the stabilizer and resulting pitch up nose attitude as the aircraft

rotates around the lateral axis.

The Elevator trim tab moved down into the airstream causes added upward force on

the elevator to help hold the elevator up. The trim tab allows adjusting for a neutral,

hands-off, control setting for a specific airspeed angle of attack indicated-airspeed.

Fig: 1-17

Aircraft Aft Fuselage


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Engine and Gravity Power

Engine-power

Your engine provides the power, creating thrust force, causing acceleration to attain

flight. Thrust, being a force vector, directs the aircraft response in the forward direction

as steered with the rudder and pitch change.

When airborne in level or climbing flight there is sustaining thrust, thecomponent of engine thrust in direction of motion, and a small vertical component of

that engine thrust from the angled attitude into the encountered airmass.

Engine power input above that required to sustain level flight is excess power.

Excess power causes an increased vertical component of engine thrust resulting in a

moment arm increase to lift the nose, rotating around the effective center of gravity, so

your aircraft will climb.

Decreased engine thrust from the sustaining thrust will cause a negative excess,

so the aircraft will descend (negative climb) with the sustaining thrust now

supplemented by gravity thrust force.

The throttle controls the engine power/thrust output and a manual mixture

control adjusts fuel/air for proper burning, enabling optimum fuel combustion for power.

For the pilot, this is control of lift.

The rudder, ailerons, and elevator flight controls are directing the engine thrust-

force.

Gravity-power

The potential energy of altitude is gravity, so is available only when inflight. Gravity

thrust is a vector, acting from the center of mass vertically downward toward the center

of the earth, no matter the attitude. Gravity can sustain flight, but using gravity powerrequires descent.

There is no throttle for gravity. Gravity thrust force requires burning (descent)

altitude. It is a very large force requiring careful control to be contained.

The only aircraft control of gravity force is attitude control. Elevator pitch control

contains the force of gravity by diverting a component of the negative vertical force to a

horizontal component of thrust (gliding) to sustain the flight while the ailerons and

rudder maintain an upright attitude and direction.

Pilot input of elevator-pitch controls the horizontal component of gravitational

thrust, thereby sustaining an indicated-airspeed.

Summary

Control of aircraft attitude revolves about the pilot. All control is to or away,

no matter the aircraft attitude or orientation.

Ailerons turn an aircraft with a horizontal component of the lift when

maneuvering into a rolled attitude.


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Rudder steers the aircraft with yaw, directing the engine thrust, yawing the

nose left or right. In a turn, the rudder coordinates by correcting adverse

forces by direction of engine thrust force.

Change of thrust or elevator input steers the thrust with pitch to or from the

pilot.

The elevator-pitch and thrust-lift maintain the angle-of-attack encounter into

the air-stream.

Aerodynamic elevator loading and engine powered outward lift cause

location of the effective center of gravity to balance a given angle-of-attack

encounter into the airmass.

Indicated-airspeed change is allowed by changing the size of the frontal-plate

area encountering the air stream and the resulting outward reactive

pressures required to maintain constant lift.

Horizontal stabilizer or elevator trim and coordinated power allow setting a

fixed angle-of-attack airmass encounter for a constant indicated-airspeed

level flight. The engine provides the thrust for attainment and sustainment of flight.

Excess thrust causes increased lift for climb. Power is lift.

Gravity is a strong acceleration force and requires careful handling. The

elevator-pitch control is the only flight control that can control gravity effect.

Elevator-pitch control causes attainment of the horizontal component of

gravity thrust for sustaining (gliding) flight.


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Chapter 2-------INDICATED-AIRSPEED

Relative motion within an airmass is required to cause an aircraft to fly. The

design of the aircraft is to fly; it wants to fly. This chapter discusses:

Body-Angle

Angle-of-Incidence

Angle-of-Attack

Relative-Wind

Frontal-Plate Area

Volumetric-Displacement

Lift

Control of Indicated-Airspeed

Horizontal Stabilizer and Elevator tail and g Loading

How to Change Indicated-airspeed

Acceleration and Deceleration

Controlling the Flight

Attaining Flight

What is speed?

What is indicated-airspeed? How indicated-airspeed differs from speed.

Attaining and sustaining indicated-airspeed.

Criteria for maintaining safe indicated-airspeed flight.

Operating within design limits.

Summary


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Body-Angle

Body-Angle is the angle of airflow encounter of the aircraft fuselage measured between

the direction of the relative wind and the longitudinal axis. Body angle is also Angle-of-

attack of the aircraft.

Angle-of-Incidence

The angle of incidence is the wing angle of attachment to the fuselage, measuredbetween the chord line of the wing and the fuselage longitudinal axis of your aircraft.

During manufacture, most aircraft have wings installed at a few fixed degrees of

incidence. It is a small upward angle of the leading edge of the wing relative to the

longitudinal axis as an attachment to the fuselage. The attachment incidence angle is

often two to four degrees.

The angle of incidence is a small preset angle for airmass encounter built into

your aircraft. You have no control of this angle. It is just nice to know.

Angle-of-Attack

The angle of aircraft pitch attitude above the relative wind. The elevator-pitch control

sets angle-of-attack to the encountering wind (relative wind). Reference is often in

regard to wing angle-of-attack, but it is the total airplane, fuselage and wings,

encountering the airflow.

Wing angle-of-attack by definition is the angle of airflow encounter between the

wing chord and direction of encountered wind. If there is no angle of incidence, wing

angle-of-attack will be the same as the body angle-of-attack.

For the pilot, there is no way to measure the angle-of-attack. The different

angles of attack of the aircraft create frontal plate areas and related encounter of

airmass pressures for maintaining different indicated-airspeeds.Indicated-airspeed is an indirect measurement of angle-of-attack for operational

purpose. A pilot only knows angle-of-attack indirectly by reference to the indicated-

airspeed, so conduct of flight requires prior knowledge of the aircraft designed

operational indicated-airspeed limitations.

The wing angle-of-attack is often confused with the elevator-pitched attitude

angle, the body angle-of-attack of the airplane. In level flight, the two can appear the

same. When level, there is no angle of climb, so wing angle-of-attack, measured

between the wing and the oncoming free-airstream from the motion, within which it is

operating, differs only with any angle of incidence from the body-angle. Usual attitude

similarities of level flight often make the two terms seem the same.The fixed angle of incidence of the wing needs no consideration of a pilot. You

control the aircraft indicated-airspeed with elevator-pitch input and the related elevator-

pitched aircraft angle-of-attack (body-angle).

In this book, all reference to control of indicated-airspeed and related elevator

controlled pitch is elevator-pitch and elevator-pitched angle-of-attack.


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Angle-of-attack change is elevator-pitched or engine-powered rotation around

the lateral axis at a changing effective center of gravity. Horizontal stabilizer or elevator

control inputs, as part of elevator-pitch angle adjustment, set indicated-airspeed.

For clarification, the elevator-pitch sets angle-of-attack for level and climbing

flight while either elevator-pitch or reduced power can change angle-of-attack for

descent. Reduced engine power will reduce angle-of-attack to the extent of its part of

the level flight sustaining elevator trimmed indicated-airspeed setting.The elevator and engine are part of the fuselage body, and control these angles.

When referring to angle-of-attack settings or changes, it is a change of elevator-pitch

controlled by the elevator manual control, horizontal stabilizer-trim, elevator-trim, or

reduced power.

Relative-Wind, Direction of Motion

Your aircraft direction of motion creates an encountering wind as it moves into the free-

stream air ahead. This created wind called relative-wind, is always relative to, and

directly opposite, the direction of motion of your airplane.

The aircraft always flies with some angle-of-attack into the relative wind. In any

attitude, whether level, climbing, descending, or turning, any changed direction of

motion always opposes this directly opposite wind pressure force. This encountered

wind of motion will always be at some angle below the longitudinal axis.

Most reference in this book of relative wind will be as direction of motion.

Frontal Plate Area

The velocity of your aircraft motion causes the encountering pressure from the mass-of-

the-air experienced by your aircraft. The front-profile surface area of your aircraft, that

meets and diverts air relates directly to the velocity of the moving machine.

Your aircraft always flies with some small upward angle of the total machine as it

passes within the airmass. The inflight front profile of your aircraft has an area of the

underside of the fuselage and wings, which encounters and displaces the free-stream

air away from the underside, and a smaller area displacing the airflow away over the

top of the body and wings.

This total area or the aircraft surface that displaces free-stream air, called the

frontal plate area, changes with change of the angle-of-attack. The greater the angle-

of-attack, the greater the profile of the frontal plate area, so there becomes a larger

displaced volume of airmass moving over a greater distance around the aircrafts form.

This allows reduced pressure per square inch (slowing of indicated-airspeed) tomaintain the same constant reactive lift force outward from the top of the aircraft.

Volumetric-Displacement

Your aircraft occupies a certain volume of space. It continually displaces its own

volume of the airmass encountered, and that volume must flow to replace itself after

passage. There are certain retarding pressure and friction forces involved during this

8/6/2019 Flight Control. How airplanes are

Flight Control. How airplanes are controlled.

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