primary flight conrol.doc

8/14/2019 PRIMARY FLIGHT CONROL.doc

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PRIMARY FLIGHT CONROL

Control System

The primary flight control of an aircraft do no more than modify the camer! or

aerodynamic "hape! of the "#rface to $hich they are attached% Thi" change in chamer

create" a change in the lift and drag prod#ced y the "#rface! $ith the immediate re"#lt ofrotating the airplane ao#t one of it" a&e"% Thi" rotation prod#ce" the de"ired change" in

the flight path of the aircraft% Control "y"tem con"i"t" of longit#dinal control! lateral

control and directional control%An aircraft i" e'#ipped $ith mo(ale "#rface" or airfoil $hich pro(ide" "taility

and control d#ring flight% The"e control" are normally di(ided into t$o categorie"! the

primary flight control and the "econdary flight control% In thi" a""ignment $e are foc#"ingon primary flight control%

The three primary flight control" for an airplane are the aileron! ele(ator andr#dder% All the"e control" are re"pon"ile for mane#(ering the aircraft ao#t it" three

a&e"%


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Aircraft movement about the axes


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Boeing 747 Flight Control System

Primary control" of airplane flight attit#de are aileron"! ele(ator"! and r#dder"%

The"e flight control "#rface" in"talled to allo$ the flight cre$ to mane#(er the airplane

ao#t the lateral! (ertical and longit#dinal a&i"% The"e primary control "#rface" arepo"itioned y hydra#lic act#ator" po$ered y the airplane)" fo#r independent hydra#lic

"y"tem"% The "#rface" are controlled from the flight compartment $ith aileron control

$heel"! ele(ator control col#mn"! and r#dder pedal"%


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The fig#re in the pre(io#" page "ho$" all of the flight control "#rface"% *tarting

$ith the left $ing o"er(e the o#toard and inoard aileron% The (ie$ of the empennage

"ho$" the "taili+er $ith it" inoard and o#toard ele(ator and the (ertical fin "ho$" thelo$er r#dder and a portion of the #pper r#dder%

Longitudinal control

Longit#dinal control con"i"t" of a fi&ed hori+ontal "taili+er on the rear end of thef#"elage! $ith mo(ale ele(ator" hinged to it" trailing edge% The"e ele(ator" are the

control "#rface" that go(ern the mo(ement ,pitch- of the aircraft along thi" longit#dinal

a&i"% They are normally attached to hinge" on the rear "par of the hori+ontal "taili+er%The con"tr#ction of an ele(ator i" "imilar to that other control "#rface"! and the de"ign of

ele(ator may e #nalance or alance aerodynamically and.or "tatically%

The ele(ator i" the "mall mo(ing "ection at the rear of the "taili+er that i"

attached to the fi&ed "ection" y hinge"% /eca#"e the ele(ator mo(e"! it (arie" the amo#ntof force generated y the tail "#rface and i" #"ed to generate and control the pitching

motion of the aircraft% There i" an ele(ator attached to each "ide of the f#"elage% Theele(ator" $or0 in pair"1 $hen the right ele(ator goe" #p! the left ele(ator al"o goe" #p%

The ele(ator i" #"ed to control the po"ition of the no"e of the aircraft and the angle of

attac0 of the $ing% Changing the inclination of the $ing to the local flight path change"the amo#nt of lift $hich the $ing generate"% Thi"! in t#rn! ca#"e" the aircraft to clim or

di(e% 2#ring ta0e off the ele(ator" are #"ed to ring the no"e of the aircraft #p to egin

the clim o#t% 2#ring a an0ed t#rn! ele(ator inp#t" can increa"e the lift and ca#"e a

tighter t#rn% That i" $hy ele(ator performance i" "o important for aircraft% 3hen anele(ator goe" #p! it $ill increa"e angle of attac0% It $ill mo(e the no"e #p% 3hen

ele(ator" goe" do$n! it $ill decrea"e angle of attac0 $hich made the no"e of aircraft goe"do$n%


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elevator raised, reduced lift, tail goes down,

nose goes u

elevator neutral !centered"

elevator lowered, increased lift, tail goes u,

nose goes down

#levator $osition

!As viewed from the side"

In 454 aircraft! the ele(ator control "y"tem pro(ide" primary control of the

airplane ao#t it" pitch a&i"% The "y"tem con"i"t of fo#r ele(ator" attach to rear "par of the

hori+ontal "taili+er! fo#r hydra#lic act#ator"! control and ele(ator feel "y"tem% Hydra#licpo$er dri(e" the ele(ator in re"pon"e to control inp#t% There are t$o ele(ator" on each

"ide of the airplane! each po$ered y hydra#lic po$er control #nit" or act#ator% The

ele(ator ne&t to the f#"elage are called inoard ele(ator and tho"e o#t farther on the"taili+er rear "par are called o#toard ele(ator"%


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Lateral control

Aileron" are primary flight control "#rface" #tili+e to pro(ide lateral ,rolling-

control of aircraft% They control aircraft mo(ement along the lateral a&i"% Lo$ering the

aileron on one $ing rai"e" the aileron on the other% The $ing $ith the lo$ered aileron

goe" #p eca#"e of it" increa"ed lift! and the $ing $ith the rai"ed aileron goe" do$neca#"e of it" decrea"ed lift% Th#"! the effect of mo(ing either aileron i" aided y the

"im#ltaneo#" and oppo"ite mo(ement of the aileron on the other $ing% Large 6et aircraft

often employ t$o "et" of aileron! one "et eing appro&imately mid$ing or immediatelyo#toard of the inoard flap! and the other "et eing in the con(entional location near the

$ingtip"%

In /454 aircraft! each $ing ha" t$o aileron"! one inoard! one o#toard and "i& "poiler"

$hich con"i"t of fi(e flight "poiler" and one gro#nd "poiler% 7ach of the aileron and

"poiler i" operated y a hydra#lic act#ator% The aileron po$er #nit i" "#pplied $ith

hydra#lic po$er from t$o independent "o#rce"% The o#toard aileron i" operational onlyd#ring lo$ "peed condition! $ith loc0 o#t eing control y the po"ition of the trailing

edge flap%


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%irectional Control

An airplane i" e'#ipped $ith certain fi&ed and mo(ale "#rface" or airfoil $hich

pro(ide" for "taility and control d#ring flight% R#dder i" a (ertical control "#rface#"#ally hinged to the tail po"t aft of the (ertical "taili+er and de"igned to apply ya$ing

mo(ement to the airplane that i" to ma0e it t#rn to the right or left ao#t the (ertical a&i"%

The r#dder i" attached to the (ertical "taili+er% Controlled y the r#dder pedal"! ther#dder i" #"ed y the pilot to control the direction left or right of ya$ ao#t the airplane8"

(ertical a&i" for minor ad6#"tment"% It i" not #"ed to ma0e the airplane t#rn! #t an0ing

the airplane to ma0e" it t#rn% 3hen the foot pre""#re on the left r#dder pedal mo(e" ther#dder to the left! ca#"ing the no"e of the airplane to mo(e to the left% 3hen the foot

pre""#re on the right r#dder pedal mo(e" the r#dder to the right! ca#"ing the no"e of the

airplane to mo(e to the right%

In /454 aircraft! the r#dder pro(ide" ya$ control for the airplane% The #pper and lo$er

r#dder i" "imilar in de"ign $ith appro&imately e'#al capaility% The"e r#dder" ha(e nota" and are po"ition y d#al tendem hydra#lic act#ator"% Hydra#lic "y"tem 9 and :

"#pply the #pper r#dder and ; and 5 "#pply the lo$er r#dder% The "y"tem con"i"t" ofpedal control and cale" ya$ damper! hydra#lic act#ator and #pper and lo$er r#dder"%


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Secondary Flight Control System

The "econdary flight control al"o called a#&iliary ha" een de(eloped eca#"e the

aircraft" are often capale of operating o(er a $ide "peed range and $ith different $eight

di"tri#tion% The n#mer and comple&ity of the "econdary control "#rface" on a partic#lar

aircraft depend on the type of the operation and flight "peed for $hich the aircraft i"de"ign% The"e are the e&ample of "econdary flight control red#ce y "poiler on top "#rface of $ing in front of aileron

= normally fl#"h $ith $ing #t $hen aileron i" rai"e! "poiler al"o mo(e #p= thi" inc drag on inner $ing in t#rn

= On "ome aircraft no aileron are fitted% "poiler #"ed for roll control

= "poiler etter than aileron


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B& Fla

= fitted to trailing edge of the $ing= pro(ide mean" of increa"ing lift of $ing at all angle

= y #"ing flap


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al"o 0no$n a" lift flap! e""entially "lotted flap

main intention and effect > inc lift

pro(ide "im#ltaneo#"ly an increa"e in $ing area and

chamer

"light increa"e in drag

increa"e ma& lift of DB

angle of a"ic airfoil at ma& 9@ deg

increa"e chamer and $ing area

e"t flap for lift

complicated mechani"m

no"e do$n pitching mo(ement

increa"e lift . inc $ing area

Leading edge fla ' (ruger fla

Mainly on high "peed airfoil and pre(ent o#ndary"eparation at lo$ "peed

In(arialy #"ed in con6#nction $ith T7 flap

Commonly #"ed i" Er#ger flap

Increa"e of ma& lift @B

Angle of a"ic airfoil at ma& lift" ;@ deg

No"e flip hinge at leading edge

Increa"e lift at "mall deflection

No"e #p pitching mo(ement

Increa"e leading edge chamer


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primary flight conrol.doc

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