Flight Stability & Dynamics, Control

(1)

(2)

Flight Stability & Dynamics, Control

• Airplane Axes

• Flight Stability and Control – Static Stability

– Dynamic Stability

• Flight Control Surfaces

– Control along the Longitudinal Axis – Control along the Vertical Axis

– Control along the Lateral Axis

– (Ref. AC 65-15A)

(3)

Airplane Axes

(Sumbu Pesawat Udara)

 Longitudinal Axis (sumbu memanjang)

 Lateral Axis (sumbu melintang)

(4)

AXES OF AN AIRCRAFT

Aircraft is completely free to move in any direction Manoeuvre  dive, climb, turn and roll, or perform

combinations of these.

Whenever an aircraft changes its attitude in flight, it must turn about one or all of these axes.

Axes – imaginary lines passing through the centre of the aircraft.

(5)

 Sumbu Pesawat Udara – adalah Tiga (3) garis khayal (imajiner) yang melalui titik berat (C.G) pesawat.

• Ketiga sumbu - dapat dipandang sbg sumbu/poros khayal dimana pesawat bebas berputar seperti roda.

(6)



Ada Tiga (3) Sumbu pesawat udara

,

yaitu :

1. Sumbu Memanjang /

Longitudinal Axis

(Roll Axis)

2. Sumbu Melintang / Lateral Axis (Pitch

Axis) /

Cross-wing Axis

3. Sumbu Vertikal /

Vertical Axis (Yaw Axis)

Sumbu Pesawat Udara

Axes of an Aircraft

(7)

Ke Tiga (3) Sumbu Pesawat –



Melalui titik berat (

Center of Gravity

, CG)

pesawat dan



Berpotongan tegak lurus satu sama

lainnya membentuk sudut 90°.

• Apabila pesawat mengubah

Sikap Terbang

atau

Posisi-nya

sewaktu terbang (

Flight Attitude or

Position in flight

), – ia berputar/rotasi terhadap

satu atau lebih dari ketiga sumbu-sumbu tsb.

Sumbu Pesawat Udara

(8)

Aircraft Rotations

Body Axes

(9)

Center of Gravity (CG)

Gravitasi (Gravity) – adalah gaya tarik-menarik yang cenderung menarik semua benda di-dalam

medan gravitasi bumi – menuju pusat bumi.

• CG atau Titik Berat – dapat dipandang sebagai Titik dimana seluruh berat pesawat,W, terpusat

(ter-konsentrasi) padanya.

• Jika pesawat udara - ditumpu tepat pada titik beratnya (its exact CG), ia akan seimbang di posisi manapun.

• CG (titik berat) – merupakan hal yang utama bagi sebuah pesawat udara, karena posisi-/letak-nya berperan penting bagi kestabilan pesawat.

(10)

• The CG is determined by the general design of

the aircraft.

• The designers estimate how far the CP travels.

• They then

fix the CG in front of the CP

for the

corresponding flight speed

in order to provide

an adequate restoring moment for flight

equilibrium.

10

Center of Gravity (CG)

(11)

(12)

(Center of Pressure, Cp)

12

• Center of Pressure (CP

) -

The point of

intersection of

the

Resultant force line

with

the Chord line

of the airfoil is called

the

center of pressure (CP

).

• The CP – moves along the airfoil chord as the

AOA changes.

(13)

(14)

Perputaran (rotasi) Pesawat Udara

Axes of an Aircraft Rotation

(15)



Sumbu MEMANJANG

(Longitudinal Axis) :

– Adalah garis lurus khayal yang membentang

sepanjang (lengthwise) fuselage, dari hidung (nose)-ke-ekor (tail) pesawat udara.

– Gerakan berputar terhadap sumbu

memanjang (longitudinal axis) – adalah

Berguling

(Roll)

dan dihasilkan oleh

pergerakan

Ailerons yang terletak di Trailing

Edges dari Wing.

• Longitudinal Axis – sering disebut sebagai Roll-Axis (Sumbu-Guling).

15

Sumbu Pesawat Udara

(16)

Gerakan berputar thd Sumbu Guling

Roll around

Longitudinal Axis

–

ROLL Axis

16

(17)

Figure 1-29 : The Ailerons cause an airplane to Roll about the Longitudinal Axis. The Primary Purpose of the Ailerons is to

Bank the wing, causing the airplane to Turn.

(18)



_{Sumbu MELINTANG (}

_{Lateral Axis}

₎

_:

– Adalah garis khayal yang melintang sepanjang bentangan sayap (crosswise), dari ujung sayap kiri-ke-ujung sayap kanan (from wing tip - to-

wing tip), tegak lurus terhadap sumbu memanjang (longitudinal axis).

– Gerakan turun-naik terhadap sumbu lateral

(lateral axis) – adalah Mengangguk (Pitch) dan dihasilkan oleh pergerakan dari Elevators di

belakang (T.E) dari Ekor Mendatar (Horizontal

tail assembly).

– Lateral Axis – sering disebut sebagai Pitch-axis

(Sumbu-Angguk). 19

Sumbu Pesawat Udara

(19)

Gerakan Mengangguk thd Sumbu Angguk

Pitch around the

Lateral Axis

–

PITCH Axis

(20)

Figure 1-30 : The Elevators cause an airplane to Pitch about the Lateral Axis. The Primary Purpose of the Elevators is to change

the angle of attack (AOA), and thereby control the airspeed.

Gerakan Mengangguk thd Sumbu Angguk

(21)



Sumbu TEGAK

( Vertical Axis ) :

– Adalah garis khayal yang secara vertikal

melalui titik berat {center of gravity (C.G)} pesawat udara.

– Gerakan berputar terhadap sumbu tegak

(Vertical axis) – adalah Menggeleng (Yaw) dan ini dihasilkan oleh pergerakan dari Rudder

yang terletak dibagian belakang (T.E) dari ekor tegak (Vertical tail /Fin assembly).

– Vertical Axis – sering disebut sebagai Yaw-axis

(Sumbu-Geleng).

23

Sumbu Pesawat Udara

(22)

Gerakan Menggeleng thd Sumbu Geleng

Yaw around the

Vertical Axis

–

YAW Axis

24

(23)

Figure 1-31 : The Rudder causes an airplane to Yaw about the Vertical

Axis. The Primary Purpose of the Rudder is to counteract Aileron Drag

and keep the fuselage streamlined with the Relative Wind.

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Ringkasan - Gerakan Pesawat Udara

terhadap Sumbu Putar

[1] Gerakan thd sumbu Longitudinal (memanjang)

pesawat (sumbu-x) – adalah “ber-guling (roll)”; [2] Gerakan thd sumbu Lateral (melintang) pesawat

(sumbu-y) – adalah “meng-angguk (pitch)”, dan

[3] Gerakan thd sumbu vertikal (tegak) pesawat (sumbu-z) – adalah “meng-geleng (yaw)”.

Yaw – adalah gerakan mendatar atau horizontal

(ke kiri & ke kanan) dari hidung pesawat (aircraft’s nose).

(25)

Ringkasan - Gerakan Pesawat Udara

terhadap Sumbu Putar

[1] ROLL

[2] PITCH

(26)



(27)

Aircraft Design Characteristics

• Each aircraft handles somewhat differently

because each resists or responds to control pressures in its own way.

For example :

– A Training aircraft – is quick to respond to control applications, while

– A Transport aircraft – feels heavy on the controls and responds to control pressures more slowly.

• These features can be designed into an aircraft to facilitate the particular purpose of the aircraft by considering certain stability and maneuvering requirements.

(28)

Stability :

• Types of Stability

– Static Stability – Dynamic Stability

• Conditions of Stability

– Positive, Negative, and Neutral

• Stability about the Axes

– Longitudinal Stability (Pitching) – Lateral Stability (Rolling)

– Vertical Stability (Yawing)

31

(29)

Stability and Control: - is the study of how to

control the speed, direction, altitude and other

conditions that affect how a airplane flies. • The engineers - :

– Design The controls that are needed in order

to fly, and instruments are provided for the pilot in the cockpit of the airplane.

• The pilot - uses these instruments to control the

stability of the plane during flight.

(30)

Instruments used by the Pilot

to

Controls

the airplane

(31)

STABILITY and CONTROL

♨

_{Tiga kata yang semuanya merujuk kepada}

Pergerakan Pesawat Udara terhadap satu

atau lebih dari ketiga sumbu rotasi – yaitu:

(1) Stability

(Stabilitas / kestabilan),

(2) Maneuverability

(kemampuan untuk

melakukan gerakan), dan

(3) Controllability

(kemampuan

mengendalikan / mengemudikan)

(32)

(Kestabilan)

♨ STABILITY (Stabilitas / kestabilan) – adalah karakteristik design utama dari pesawat udara yang :

– Menyebabkan pesawat kembali ke posisi

kesetimbangan penerbangan semula (initial

equilibrium flight conditions) , atau kondisi

terbang stabil (steady flight), sesudah terjadi gangguan.

– Cenderung menyebabkan pesawat udara (tanpa dikemudikan /hands-off) terbang didalam lintasan lurus dan mendatar (straight and level flight).

(33)

(Stabilitas / Kestabilan)

Stabilitas – adalah suatu kualitas penting dari pesawat udara

untuk memperbaiki kondisi yang mungkin mengganggu

kesetimbangan-nya, dan untuk kembali ke- atau melanjutkan pada lintasan terbang semula (the original flightpath).

Apabila pesawat tersebut stabil, maka pesawat tersebut akan

(34)

(35)

:

♨

_{MANEUVERABILITY –}

Adalah :

• Karakteristik dari pesawat terbang yang memungkinkan

Pilot dengan mudah menggerakkan pesawat terbang

terhadap ketiga sumbunya, dan

• menahan tegangan (stresses) yang terjadi akibat dari

maneuver tsb.

Maneuverability Tergantung kepada :

• Weight (bobot pesawat), Inertia (inersia pesawat), Size

& Location of Flight Controls (ukuran & letak pengendali terbang), Structural strength (kekuatan struktur), dan

Powerplant (mesin).

Kemampuan Maneuver juga merupakan karakteristik dari

(36)

:

♨ CONTROLLABILITY— adalah kemampuan Pesawat untuk me-respon/-nanggapi thd

pengendalian pilot, terutama yang berkaitan

dengan lintasan terbang (flight-path) dan sikap

(attitude).

 Dapat dikendalikan (controllability) – adalah

kualitas / mutu dari respon pesawat terhadap aplikasi pengendalian pilot ketika menggerakan /maneuvering pesawat udara, terlepas dari

karakteristik kestabilan pesawat.

(37)

TYPES OF STABILITY

ADA DUA (2) JENIS (TIPE) KESTABILAN :

 Kestabilan Statis (Static Stability)

 Kestabilan Dinamis (Dynamic Stability)

KESETIMBANGAN (EQUILIBRIUM) - adalah:

 Suatu kondisi dimana penjumlahan semua Gaya

dan Momen yang bekerja pada benda adalah Nol.

(38)

 Pesawat Terbang dalam keadaan

Setimbang:

 Jumlah Semua Gaya dan Momen yang bekerja

pada pesawat = 0

 Tidak mengalami Percepatan (no acceleration),  Pesawat melaju dengan kondisi terbang stabil

(steady state of flight ).

 Hembusan Angin (wind gust) atau defleksi dari

Bidang-bidang Kendali (controls) mengusik

kesetimbangan (equilibrium), dan pesawat udara mengalami percepatan akibat ketidak- seimbangan (unbalanced) Momen atau Gaya (forces).

TYPES OF STABILITY

(39)

 There are

Two Main Types of Aircraft

INSTABILITY

(KETIDAK STABILAN)

:

 An aircraft with Static Instability uniformly departs from an equilibrium condition

 An aircraft with Dynamic Instability oscillates about the equilibrium condition with increasing amplitude.

•There are Two Modes of Aircraft CONTROL :

▪One moves the aircraft between equilibrium states, ▪The other takes the aircraft into a non-equilibrium

(accelerating) state.

►Control is directly opposed to stability.

(40)

TYPES OF STABILITY :

A. STATIC STABILITY (STABILITAS / KESTABILAN

STATIS) :

• Tendensi / kecenderungan awal, atau arah gerakan, untuk kembali ke sikap semula (original attitude), y.i ke kondisi setimbang (equilibrium).

• Dalam penerbangan, hal yang berkenaan dengan

respon awal pesawat udara ketika ketika diusik dari AOA (sudut serangan), slip, atau membelok (bank). B. DYNAMIC STABILITY (STABILITAS / KESTABILAN

DINAMIK) :

 Menentukan bagaimana caranya kembali.

 Mencakup cara bekerjanya gaya restoratif dalam kaitannya dengan waktu.

(41)

A. STATIC STABILITY

• Static stability deals with the tendency of a

displaced body

to return to equilibrium

, that

the aircraft displays after being disturbed from

its trimmed condition.

• The three types (conditions) of static stability

are

defined by the character of movement

following some disturbance from equilibrium.

(42)

OF STABILITY

 ADA TIGA MACAM KEADAAN / KONDISI

KESTABILAN :

1. POSITIVE Stability

2. NEUTRAL Stability 3. NEGATIVE Stability

• (Lihat Figures 4-18 dan 2-11, untuk jenis/tipe

Stabilitas/kestabilan Statik)

(43)

OF STABILITY

 KEADAAN / KONDISI KESTABILAN – (samb):

• Kadang-kala turbulensi atau gerakan yang

tidak konsistesten menyebabkan

Buffeting

pada pesawat .

• Buffeting -

Turbulent movement of the air

over an aerodynamic surface.

(44)

A. STATIC STABILITY

1. POSITIVE STATIC STABILITY – exists when the disturbed

object tends to return to equilibrium.

2. NEGATIVE STATIC STABILITY, or STATIC INSTABILITY, - exists

when the disturbed object tends to continue in the direction of disturbance.

3. NEUTRAL STATIC STABILITY – exists when the disturbed

object has neither tendency, but remains in equilibrium in the direction of disturbance.

• These three types of stability are illustrated in Figures

4-18 & 2-11.

47

TYPES OF STABILITY :

(45)

Types of STATIC Stability

(46)

Figure 2-11. STATIC Stability

(47)

Penerapan di Pesawat Terbang

(a) Equilibrium Flight = Neutral Static Stability

(b) Statically Unstable airplane = Negative Static Stability

(c) Neutral Static Stability

(48)

C

ONDITIONS

OF

S

TABILITY

:

1. POSITIVE STABILITY /stabilitas Positif [Fig. 1-32] :

– POSITIVE STATIC STABILITY —the initial tendency of the aircraft TO RETURN TO THE ORIGINAL STATE OF EQUILIBRIUM

after being disturbed [Figure 4-18.A &2-11.A.].

• Fig. 1-32 : Positive Static and Dynamic Stability, as illustrated by the ball in a trough, is a desirable

characteristic for most airplanes.

• Most airplanes are designed to exhibit the damped

oscillation form of stability when disturbed from pitch equilibrium.

(49)

C

ONDITIONS

OF

S

TABILITY

• Pada kondisi Stabilitas Positif – pesawat udara akan kembali ke keadaan semula sesudah

turbulensi reda.

• Kondisi stabil positif – merupakan hal yang

diharapkan oleh hampir semua pesawat terbang,

• Kecuali pesawat tempur mutakhir yg dilengkapi dgn computer augmented flight controls mungkin memilih menggunakan stabilitas negatif atau

netral untuk meningkatkan kelincahan

maneouver-nya.

(50)

1. P

OSITIVE

Stability

Figure 4-18. Type of STATIC Stability

(51)

C

ONDITIONS

OF

S

TABILITY

:

2. NEUTRAL STABILITY / stabilitas Netral [Fig. 1-34]:

• Neutral static stability—the initial tendency of the aircraft to remain in a new condition after its

equilibrium has been disturbed.

[Figures 4-18 & 2-11.C.].

• Fig. 1-34: An object that has Neutral stability

remain displaced from its original state whenever a force is applied. A neutrally stable airplane would be difficult to control and would probably require computer-augmented flight controls.

(52)

2. N

EUTRAL

Stability

Figure 4-18. Type of STATIC Stability

(53)

C

ONDITIONS

OF

S

TABILITY

:

3. NEGATIVE STABILITY _{/stabilitas Negatif [Fig. 1-33] :}

 Negative Static Stability (statically Unstable)—the initial tendency of the aircraft to continue away from the

original state of equilibrium after being disturbed [Figures

4-18 & 2-11.B.].

 Fig. 1-33: Negative Stability, as illustrated by a ball rolling

off the crest of a hill, is an undesirable characteristic in airplanes. A pilot would be very likely to loose control of an airplane with negative stability.

 If the corrective forces increase with time, the body has

(54)

3. N

EGATIVE

Stability

Figure 4-18. Type of STATIC Stability

(55)

(56)

B. DYNAMIC STABILITY

• Static stability deals with the tendency of an a/c

(a displaced body) to return to equilibrium

Occasionally, the initial tendency is different or

opposite from the overall tendency, so a

distinction must be made between the two.

Dynamic stability – refers to the aircraft

response over time when disturbed from a given AOA, slip, or bank.

• Dynamic stability deals with the resulting motion with time.

TYPES OF STABILITY

( Jenis Kestabilan )

(57)

• Pesawat udara apa saja – harus menunjukkan tingkat kestabilan statik dan dinamik yang diperlukan.

• Jika pesawat udara dirancang (designed) – dengan ketidak stabilan statik (static instability) dan tingkat ketidak-stabilan dinamik yang cepat, pesawat akan sangat sulit, jika tidak mustahil, untuk terbang.

• Biasanya, stabilitas dinamik positif diperlukan

dalam suatu rancang-bangun pesawat udara - untuk mencegah osilasi /goyangan terus-menerus yang

tidak disukai dari pesawat.

(58)

• Any aircraft must demonstrate – the required

degrees of static and dynamic stability.

• If an aircraft were designed with static

instability and a rapid rate of dynamic

instability, the aircraft would be very difficult,

if not impossible, to fly.

• Usually, positive dynamic stability is required

in an aircraft design to prevent objectionable

continued oscillation of aircraft.

61

(59)

DYNAMIC STABILITY also has Three Subtypes:

[Figure 4-19]

1. POSITIVE DYNAMIC STABILITY— the motion of the

displaced object decreases in amplitude with time and, because it is positive, the object displaced returns

toward the equilibrium state.

2. NEUTRAL DYNAMIC STABILITY— once displaced, the displaced object neither decreases nor increases in

amplitude. A worn automobile shock absorber exhibits this tendency.

3. NEGATIVE DYNAMIC STABILITY (or DYNAMIC INSTABILITY)—

the motion of the displaced object increases with time, and becomes more divergent.

(60)

63

D

YNAMIC

S

TABILITY

:

Dinamik Positif Dinamik Netral Dinamik Negatif

(61)

Conditions of Dynamic Stability :

(62)

Damped vs Undamped Stability :

Static Stability Dynamic Stability Oscillation

Positive Static Positive Dynamic Damped Oscillation

Positive Static Neutral Dynamic Undamped Oscillation

Positive Static Negative Dynamic

(Dynamic Instability)

Divergent

Oscillation

65

(63)

(64)

67

(65)

S

TABILITAS

DAN

G

ERAKAN

P

ESAWAT

U

DARA

,

(Stability and Motions of an Aircraft)

•Stabilitas terhadap Sumbu

Pesawat Udara

(66)

Motion of an Aircraft about its Axes

69

(67)

Stabilitas & Gerakan Pesawat Udara

 S

TABILITAS

(S

TABILITY

)

– adalah kemampuan

pesawat memperbaiki sendiri gerakan

penyimpangan yang disebabkan oleh turbulensi

udara tanpa pengendalian oleh Pilot.

• Apabila pesawat tersebut stabil, maka pesawat

tersebut akan kembali ke posisi

kesetimbangan-nya (

Trim Position

).

• Stabilitas pesawat sangat ditentukan oleh posisi

(68)

Stabilitas & Gerakan Pesawat Udara

 Tiga (3) jenis Gerakan - yang perlu diperbaiki sendiri oleh KESTABILAN / STABILITAS pesawat, y.i :

1. Mengangguk (Pitch)

– rotasi terhadap

sumbu-Y (Sumbu Lateral)

2. Berguling (Roll)

– rotasi terhadap

sumbu-X (Sumbu Longitudinal)

3. Berputar (Yaw) – rotasi terhadap

sumbu-Z (sumbu Vertikal / Vertical)

(69)

 Stabilitas terhadap sumbu pesawat udara

(stability about the Axes of the aircraft),

ada

Tiga:

– Longitudinal Stability (pitch)

/ stabilitas

membujur;

– Lateral Stability

(roll)

/ Stabilitas melintang;

– Directional Stability (yaw) / Stabilitas arah.

(70)

 Stabilitas terhadap sumbu pesawat udara

(stability about the Axes of the aircraft),

kombinasi gerakan :

– Dutch Roll – stability

:

A Dutch Roll is an

aircraft motion consisting of an

out-of-phase combination of yaw and roll.

• Dutch roll stability can be artificially increased

by the installation of a yaw damper.

73

(71)

Motion of an Aircraft about its Axes

(72)

Motion of an aircraft about its axes.

75

A. Banking (roll) control affected by Aileron movement

(73)

Motion of an Aircraft about its Axes

(74)

77

Motion of an aircraft about its axes.

(75)

FIGURE 2-10 : View C

(76)

79

Motion of an aircraft about its axes.

(77)

Stabilitas & Gerakan Pesawat Udara

Illustrates the roll, pitch, and yaw motion of the aircraft along the longitudinal, lateral, and vertical axes, respectively.

[1] ROLL

[2] PITCH

(78)

 Kesetimbangan ditentukan dari letak Pusat

Massa Pesawat (CG).

• Posisi pusat massa ditentukan dari

bagaimana berbagai macam kontributor ke

berat pesawat diletakkan di dalam pesawat.

Dalam hal ini berarti pengaturan siapa

duduk di mana, juga pengaturan letak

muatan bagasi.

Stabilitas & Gerakan Pesawat Udara

(79)

 Kondisi kesetimbangan yang

stabil dipenuhi apabila pusat massa pesawat di depan titik

yang disebut Titik Netral

(Neutral Point) .

 Neutral Point (Aerodynamic

Center atau Center of

Pressure). Angka tipikal untuk titik netral adalah sekitar 0.25 (sekitar 1/4 panjang chord

sayap).

(80)

1. Logitudinal Stability

(

Pitching)

(81)

1. Logitudinal (

Pitch)

Stability

Illustrates the pitch motion of the aircraft along the lateral axis

(82)

1. Longitudinal Stability or

Pitching

(Stabilitas Membujur)

1. Mengangguk (Pitch): ini adalah gerakan hidung pesawat (nose) naik atau turun oleh gangguan udara.

• Pesawat harus memiliki Stabilitas

Membujur (Logitudinal Stability atau Pitching) – untuk

mengembalikan hidung pesawat ke posisi datar seperti semestinya,

• Ekor pesawat (Elevator/Horizontal

Tail)- adalah bagian utama yang bertugas melakukan pekerjaan ini.

(83)

• Fig. 4-20: Karena wing’s center of lift (CL)/center

pressure berada dibelakang titik berat (center of

gravity CG), wing pesawat terbang menghasilkan

nose-down pitching moment.

• Pitching moment tsb di-imbangi/lawan

(counter-acted) oleh gaya kebawah (down-load) yang

dihasilkan oleh horizontail tail surface.

• Elevator trim dapat diatur oleh pilot untuk

menghasilkan down-load yang diinginkan pada sembarang kecepatan, dengan demikian

mengimbangi pesawat agar tetap terbang lurus dengan sedikit atau tanpa dikemudikan.

(84)

 The Horizontal Stabilizer – is the Primary Surface

which Controls Longitudinal Stability.

• The action of stabilizer depends upon – ♦ The Speed and

♦ The Angle of Attack (AOA) of the aircraft.

A longitudinally unstable aircraft - has a tendency to dive or climb progressively into a very steep dive or climb, or even a stall.

• Thus, an aircraft with longitudinal instability

becomes difficult and sometimes dangerous to fly.

1. Logitudinal Stability (

Pitching

)

(85)

 The aircraft is said to have Longitudinal Stability : • When an a/c has a tendency to keep a constant an

angle of attack (AOA) with reference to the

relative wind – that is, when it does not tend to put its nose down and dive, or Lift its nose and stall.

• Longitudinal stability – is the quality that makes an aircraft stable about its lateral axis.

• Longitudinal Stability – refers to Motion in Pitch

as the aircraft’s nose moves up and down in flight.

(86)

 S

TATIC

L

ONGITUDINAL

S

TABILITY OR

I

NSTABILITY

in an aircraft, is

Dependent upon

Three

Factors

:

1. Location of the wing with respect to the CG;

2. Location of the horizontal tail surfaces with

respect to the CG;

3. Area or size of the tail surfaces.

89

(87)

Fig.2-12 :

• Illustrates the

contribution of Tail Lift to stability. If the a/c changes its AOA, a change in Lift takes place at aerodynamic center (center of

pressure, Cp) of the Horizontal Stabilizer.

(88)

91

(89)

• Under certain conditions of Speed, Load, and

Angle of Attack (AOA), – the flow of air over

the Horiz. Stabilizer creates a Force which

pushes the Tail Up or Down.

• When conditions are such that the airflow

creates Force Up = Force Down, the forces are

said to be in Equilibrium.

• This condition is found in Level Flight in calm

air.

(90)

The ELEVATOR

controls PITCH.

On the horizontal tail surface, the Elevator tilts up or down,

decreasing or

increasing lift on the tail. This tilts the nose of the airplane up and down.

Elevator Controls Pitch

(91)

(92)

Lateral Stability

 Stability about longitudinal axis  rolling motion

 Laterally stable aircraft tend to return to the original attitude from rolling motion

 Lateral stability is maintained by the wing

(design)

a. Dihedral – the upward inclination of the wings

from their point of attachment

b. Sweepback – wing leading edges are inclined

backwards from their points of attachment

(93)

Lateral Stability

(94)

2. Lateral or

Roll

Stability

2. Berguling ( Roll ): gerakan Pesawat Udara

berguling kalau ujung sayap dipaksa naik atau turun.

• Dalam gerakan ini pesawat akan slip /tergelincir kearah ujung sayap yang lebih rendah, kecuali

jika diperbaiki oleh stabilitas melintang (Lateral Stability).

• Kecenderungan (tendency) untuk kembali ke sikap/attitude semula dari gerakan berguling

(roll motion) thd sumbu longitudinal – disebut

Stabilitas Lateral (Lateral Stability).

(95)

2. Berguling (Roll) . . . .

• Stabilitas melintang (Lateral atau Roll Stability)

– dipasok terutama oleh wing dihedral (Fig.2-14

& Fig. 4-25).

• Lateral or roll stability – biasanya diperoleh dengan memiringkan sayap sedikit keatas dari tubuh pesawat ke ujung sayap, pada waktu

pesawat dibuat.

• Sudut pemasangan sayap demikian disebut

Sudut Dihedral dan tidak dapat diubah oleh

pilot.

(96)

• Motion about its longitudinal (fore and aft) axis is – a

Lateral or Rolling motion.

• Lateral stability of an airplane – involves consideration of rolling moments due to sideslips. A sideslip – tends to produce both a Rolling and a Yawing motion.

• If an airplane has a favorable rolling moment, a Sideslip will tend to return the airplane to a level-flight attitude. • The Principal Surface contributing to the Lateral Stability

of an airplane is the Wing.

• The Effect of the geometric Dihedral of a Wing (Fig. 2-14) – is a powerful contribution to Lateral Stability.

2. Lateral Stability atau

Rolling

(97)

• With the Relative Wind from the side, the

Wing

into

the wind is subject to –

an increase

in AOA and develops an increase in Lift.

• The Wing

away from the wind is subject to –

a decrease in AOA and develops less Lift.

• The Changes in Lift – effect a rolling moment

tending to

raise the windward wing

.

(98)



D

IHEDRAL

(F

IGURES

2-14 & 4-25)

• The most common procedure for producing

lateral stability is to build the wings with an angle of one (1°) to three (3°) degrees above

perpendicular to the longitudinal axis. (Fig. 2-14). • The wings on either side of the aircraft join the

fuselage to form a slight V or angle called “dihedral.”

• The amount of dihedral is measured by the angle made by each wing above a line parallel to the lateral axis.

101

Fig. 2-14.

Contribution of Dihedral to

(99)

Fig. 2-14.

Contribution of Dihedral to

Lateral Stability

atau

Rolling

Fiigure: RIGHT – Aileron DOWN

(100)

• Dihedral involves a balance of lift created by

the wings’ AOA on each side of the aircraft’s

longitudinal axis.

• If a momentary gust of wind forces one wing to

rise and the other to lower, the aircraft banks.

• When the aircraft is banked without turning,

the tendency to sideslip

or slide downward

toward the lowered wing occurs. [Figure 4-25].

103

Fig. 2-14.

Contribution of Dihedral to

(101)

104

2. Lateral Stability atau

Rolling

Illustrates the rolling motion of the aircraft along the longitudinal axis

(102)

105

Ailerons

Figure: LEFT – Aileron- DOWN

(103)

(104)

 Sweepback

• Sweepback is an addition to the dihedral that increases the lift created when a wing drops from the level

position.

• A sweptback wing is one in which the leading edge slopes backward.

• When a disturbance causes an aircraft with sweepback to slip or drop a wing, the low wing presents its leading edge at an angle that is perpendicular to the relative airflow.

• As a result, the low wing acquires more lift, rises, and

the aircraft is restored to its original flight attitude.

107

Effect of Sweepback on Lateral

Stability

(105)

 Sweepback – (continued)

• Sweepback also contributes to directional (yaw) stability.

• When turbulence or rudder application causes the aircraft to yaw to one side, the right wing presents a longer leading edge perpendicular to the relative airflow.

• The airspeed of the right wing increases and it acquires more drag than the left wing.

• The additional drag on the right wing pulls it

back, turning the aircraft back to its original path.

Effect of Sweepback on Lateral

Stability

(106)

Ailerons Control Roll

The AILERONS control

ROLL.

On the outer rear edge of each wing, the two

Ailerons move in

opposite directions, up

and down, decreasing lift on one wing while

increasing it on the other. This causes the airplane to roll to the left or right.

(107)

3. Directional Stability (Yawing)

(108)

Directional Stability



_{Stability about the vertical axis}



Directionally stable aircraft tends to remain on

its course in straight and level flight



Directional stability is maintained by keel

surface of the vertical stabilizer



Sweptback wings also aid in directional

stability (frontal area)

(109)

(110)

Effect of Sweepback on Directional

Stability

• When an airplane with swept-back wing is

flying straight into the wind, the Lift and Drag on both sides are equal.

• When an airplane yaws to the left, the right

wing produces more induced drag than the left, and the airplane tends to straighten into the relative wind.

(111)

3. Directional Stability (

Stabilitas Arah

)

Illustrates the yaw motion of the aircraft along the vertical axis

(112)

3. Directional

Stability (Stabilitas

Arah

)

3. Berputar (Yaw) :

dalam gerakan ini

hidung pesawat berputar kekiri atau

kekanan, dan pesawat akan Membelok.

• _{Untuk memperoleh}

_{Stabilitas Arah}

(Directional Stability)

dipasang sirip

ekor (vertical fin/ stabilizer), supaya

pesawat tetap pada arah lurus seperti

yang dikehendaki.

(113)

3. Directional

Stability

(Stabilitas

Arah

)

(114)

117

(115)

The RUDDER controls

YAW.

On the vertical tail fin, the

rudder swivels from side to side, pushing the tail in

a left or right direction. A pilot usually uses the

rudder along with the ailerons to turn the airplane.

(116)

Airplane Controls, Movements, Axes of Rotation, and Types of Stability

(117)

Airplane Controls, Movements, Axes of Rotation, and Types of

(118)

Mengendalikan Pesawat

Terbang

(119)

CONTROL

(Pengemudian/Pengendalian)

:

 Pengemudian /Pengendalian (Control)

–

adalah tindakan yang dilakukan untuk

membuat pesawat udara mengikuti lintasan

terbang yang diinginkan.

• Ketika pesawat terbang disebut “controllable”

(

dapat dikendalikan

) – artinya bahwa pesawat

menanggapinya/me-respon dengan mudah

dan cepat terhadap gerakan kemudi

(controls).

(120)

• Menggerakkan bidang kendali (control

surfaces) pada pesawat – akan mengubah

aliran udara diatas permukaan pesawat udara.

• Hal ini menimbulkan perubahan pada

keseimbangan gaya-gaya yang bekerja untuk

mempertahankan pesawat terbang lurus dan

mendatar (straight & level flight).

CONTROL (KENDALI) :

(121)

Mengendalikan Pesawat Terbang

• Pilot harus dapat mengendalikan pesawat

terbang – walaupun sebagaimana stabilnya

sebuah pesawat terbang.

• KONTROL MEMBUJUR (Lateral Control):

digunakan untuk menaikkan dan menurunkan

hidung (nose) pesawat, dan ini diperoleh

dengan

Elevator

terletak di bagian belakang

ekor mendatar (Horizontal Tailplane,

(122)

Mengendalikan Pesawat Terbang

• KONTROL MELINTANG (Longitudinal Control):

digunakan untuk memiringkan pesawat. Hal

ini diperoleh dengan kemudi guling

(Aileron)

pada trailing edge sayap.

• KONTROL ARAH (Directional Control):

• Digunakan untuk membelokkan kemudi

pesawat kekiri atau kekanan. Diperoleh dari

kemudi arah

(Rudder)

pada sirip ekor pada

Vertical Tail (Vertical Stabilizer/ Vertical Fin).

(123)

Bidang Kendali Terbang

(Flight Control Surfaces)

• PRIMARY (Utama) : Aileron, Elevator, Rudder • SECONDARY ( Kedua) :

(124)

Flight Control Surfaces

(Bidang Kemudi/Kendali Terbang)

• Bidang Kendali Terbang (Flight Control Surfaces) – adalah airfoil yang ber-engsel atau bergerak yang dirancang untuk mengubah sikap (attitude) pesawat udara selama penerbangan.

• Bidang /permukaan Kendali Terbang dibagi

menjadi tiga kelompok : – Primary

– Secondary – Auxiliary

(125)

(126)

Rolling

(berguling)

(127)

(128)

Definisi Pilihan

(129)

Selected Definitions :

• Buffeting – is a high-frequency instability, caused by airflow

separation or shock wave oscillations from one object striking another.

– It is caused by a sudden impulse of load increasing. – It is a random forced vibration.

– Generally it affects the tail unit of the aircraft structure due to air flow down stream of the wing.

• Slipping turn – An uncoordinated turn in which the aircraft

is banked too much for the rate of turn, so the horizontal lift component is greater than the centrifugal force, pulling the aircraft toward the inside of the turn.

• Sideslip — A slip in which the airplane’s longitudinal axis

remains parallel to the original flight-path, but the airplane no longer flies straight ahead. Instead, the horizontal

component of wing lift - forces the airplane to move

(130)

• Dihedral – The positive acute angle between the lateral

axis of an airplane and a line through the center of a wing or horizontal stabilizer. Dihedral contributes to the lateral stability of an airplane.

• Directional stability – Stability about the vertical axis

of an aircraft, whereby an aircraft tends to return, on its own, to flight aligned with the relative wind when disturbed from that equilibrium state.

The Vertical Tail is the primary contributor to

directional stability, causing an airplane in flight to align with the relative wind.