sheet metal notes day 1

8/11/2019 Sheet Metal Notes Day 1

1/15

UNIVERSITI KUALA LUMPUR MALAYSIAN INSTITUTE OF

AVIATION TECHNOLOGY

I. Evolution of Airr!ft Strutur"

- So many people dream of flying.

- From Daedalus to the Wright Brothers

- Until now many types of plane roars our sky. From the big 747 to the smallest ultralight plane.- an has fulfill their dreams

- !he in"rease knowledge of flight and e#perien"e has bring to the building a strong$ lightweight

plane.- !o minimi%e wind resistan"e and strength pro&ided by the truss stru"ture$ the designers atta"hed a

super stru"ture of wooden formers and stringers o&er the truss to gi&e the angular form a smooth

streamlined shape.- a'or breakthrough$ during WW($ welded thin wall steel tubing was first used for fuselage truss.

- !hen stru"tural de&elopment "ame with the dis"o&ery of a form of "onstru"tion without the truss but

had a streamlined form that had pre&iously furnished by the superstru"ture. )nown as stressed skin

superstru"ture.

- !he *o"kheed "ompany populari%es this type of "onstru"tion on the +ega models. !hin sheets ofwood &eneer were held under heat and pressure in large "on"rete mold and formed into a plywood

eggshell-like stru"ture.- *aminated wood rings were built into this shell for support at "riti"al spots. ,tta"hment points for the

engine$ the wing$ the tail and landing gear.

- !hin aluminum alloy sheets were ne#t used for the skin of stressed skin air"raft stru"ture.- !his sheets are formed with their "ompound "ur&es either in hydropresses or by drop hammers.

- !he formed skins are then ri&eted onto thin sheet metal formers and ribs.

- ono"oue stru"ture has no internal frame work

- odern air"raft uses semi-mono"oue in whi"h an internal arrangement of formers and stringers isused to pro&ide additional rigidity and strength to the skin.

II. T#$"% of !irr!ft %trutur"

A. Strutur"% T&!t Pro'u" Lift

(. T&" Airfoil S"tion

- ,erodynami" lift , for"e produ"ed by air mo&ing o&er a spe"ially shaped surfa"e

"alled an airfoil. /t is an a"tion that is perpendi"ular to the dire"tion- !he airfoil has more "ur&ature on the top rather than the bottom. Use an assymetri"al

airfoil

- !he airfoil for a supersoni" air"raft usually a symmetri"al airfoil$ whi"h is both the

top and bottom "ur&ature$ is the same.- For lift to produ"e there must be an angle between the "hord of the wing to the

relati&e wind. !his is "alled angle of atta"k.

- ,s air passes below the airfoil$ it is defle"ted downward and slowed down slightly.- !his will produ"e a differential lift$ where the pressure at the upper wing is de"reased.

- !he air abo&e the surfa"e will be pulled down into this low pressure0 as a result$ air is

for"ed down as the airfoil mo&es through it. !his is "alled downwash$ whi"hprodu"es lift.

- /n 1hysi"s$ for an air"raft to fly$ the lift must be greater than the weight of the air"raft

and the ,o, must be high.

1g - (


2/15


AVIATION TECHNOLOGY

- But this is not always true$ as the "riti"al angle of atta"k is a"hie&ed$ the air will break

away that "auses the air to stall.- !he airflow o&er the leading edge of an airfoil is "riti"al.

- Usually the flush ri&ets are used on some all metal wings in the areas where the

airflow must be smooth to produ"e the ma#imum pressure drop.- 1rotruding head ri&ets are used in the rest of the wing for e"onomy "onstru"tion.

). Tr!n%*ittin+ t&" Lift into t&" Strutur"

- !he defle"tion of the wind produ"es the lift$ and this lift must be eually transmitted

to the air"raft.

- ,nd the stru"ture "an support all loads without damaging the wind defle"tion.- !he wing is mounted on the airplane in a lo"ation that pla"es "enter of lift$ where lift

is "on"entrated. /t is slightly behind the "enter of gra&ity.

- So as the air"raft maneu&er$ the torsion and bending will be imposed on the wing.

- !he wing spar whi"h are the main spanwise members of the stru"ture$ are designed to

"arry these bending loads.

,. Tru%%-T#$" in+ Con%trution

- Usually found in a fabri" "o&ered air"raft

- ain stru"ture is the sparsgoes lengthwise

- Wood spars are made from Sitka Spru"e either solid or laminated.

- Usually use laminated wood$ to get a near perfe"t wood.

1g - 2

Solid Wood *aminated WoodBuilt-up wood bo#

spar

Built-up wood

/- Beam3#truded ,luminum ,lloy

Built-up metal /-

Beam


3/15


AVIATION TECHNOLOGY

- /t is a strip of wood glue together and the strength is almost the same as the solid

spars e#"ept less e#pensi&e.- !he spars are separated by "ompression members or "ompression struts that may be

either steel tubing or hea&y-wall aluminum alloy tubing.

- ompression ribs are designed to spe"ially to take "ompressi&e loads.- !he truss is held together with high strength solid steel wires that "ross the bays

formed by the "ompression struts.

- Drag wire$ is a wire that e#tend from spar inboard to the rear spar outboard oppose thefor"es that tends to drag against the wing and pull it ba"kwards.

- ,nti-drag wire is a wire that atta"hed to the rear spar inboard and goes to the front

spar outboard$ to oppose any for"e that tends to mo&e the tip of the wing forward.

- ,ll these "riteria pro&ides lightweight.

- During WW($ a bo# spar "onstru"tion is used.

- /t is a"tually a bo# stru"ture built between the spars stiffens the spars so they "an"arry all of the bending and torsional loads to whi"h the wing is sub'e"ted in flight.

- !he former ribs will gi&e the wing aerodynami" shape it needs to produ"e lift when

air flows o&er its fabri" "o&ering.

1g - 5

, built up bo# spar a""epts torsional as well as

bending loads., built up wing rib made of wood

Front Spar

6ear Spar,nti Drag Wire

Drag Wire

ompression

Strut

Sheet etal *eading 3dge

!ip Bow

in+ on%trution u%in+ /oo'


4/15


AVIATION TECHNOLOGY

- !he strips that form the top and bottom of the rib are "alled "ap strips$ and those

between the "ap strips are "alled "ross members.

- !he end-grain glue 'oint ha&e &ery little strength ea"h interse"tion of a "ap strip and a"ross members has a gusset of thin mahogany plywood glued to the strips of wood to

"arry the stresses from one strip to the other.

- etal wing ribs may be either built up by ri&eting together "ap strips and "ross

members made of formed$ thin sheet aluminum alloy$ or may be pressed fromaluminum alloy sheets in a hydropress.

- !he most "riti"al part of the wing is the leading edge$ be"ause it will determine the

flow of the wind.

0. Str"%%"'-%1in in+ Con%trution

- Semi-mono"oue "onstru"tion is generally used for the main portion of the wing$while simple mono"oue form is often used for "ontrol surfa"e.

- ,d&antage of all metal wings is it "an built to "arry all the flight loads within the

stru"ture so it does not need any e#ternal struts or bra"es.- Su"h an internally bra"ed wing is "alled a "antile&er wing.

- Su""essfully used in D-2 air"raft. as a strong wing due to thi"kness at the "enterse"tion that built into the fuselage.

- as a multi spar "onstru"tion in whi"h se&eral spars "arry the flight loads$ and spanwise stiffeners run between the spars to pro&ide e&en greater strength.

- /n the new era of airplane$ a thi"k aluminum slab is used to pro&ide stiffness and

strength.- !wo ma'or impro&ements o&er "on&entional method of ma"hining wing skins.

a8 hemi"al milling

- ,n a"id-resisting "oating is treated on the aluminum alloy where the fullthi"kness of thi"kness of the material is needed.

- !he slab is then immersed in a &at of a"id and the aluminum that is not needed

is eaten away.- 9ood for remo&ing large amounts of material$b8 3le"tro"hemi"al ma"hining.

- Used to ma"hine deep groo&es or "omple# shapes.

- !he skin is immersed in a salty ele"trolyte$ and an ele"trode "utting tool ofsoft "opper$ "arrying a large amount of "urrent$ is passed near the surfa"e of

the skin.

- !his will "ause the metal is eaten away at a rapid rate without tou"hing thematerial.

- ,d&antage$ there will be no marking that "an "ause stress "on"entration.

1g - 4

Wing rib made of pressed sheet metal


5/15


AVIATION TECHNOLOGY

- hemi"al milling pro"ess produ"ed mu"h stronger wing skin that had a redu"ed

tenden"y to "ra"k.

- !o gain ma#imum amount of stiffness for the weight$ some air"raft ha&e wing skins

made of laminated stru"ture in whi"h thin sheets of metal are bonded to a "ore offiberglass$ paper or metal honey"omb material.

- Some supersoni" air"raft ha&e their outer skins made of stainless steel bra%e to "oresof stainless steel honey"omb.

- Wing leading edges and e&en bo# spar se"tion made of bonded honey "omb material

and the inside of these stru"tures used to "arry fuel.

- !he ad&antage is for the "onstru"tion of an integral fuel tanks$ be"ause no need to sealat all the ri&ets.

- Some of the e#tremely light wing stru"tures su"h as high performan"e sail planes and

for e#perimental airplanes$ are built using a "omposite stru"ture "onsisting of apolystyrene foam "ore "o&ered with layers of reinfor"ing material and bonded to the

foam with a matri# of epo#y or polyester resin.

2. Strutur" t&!t Pro'u" Control

- !here are three a#es when an air"raft rotates.

(. Pit& Control

- 1it"h is the rotation of the air"raft about the lateral a#is.

- *ateral a#is is an imaginary line parallel to the span of the airplane and passes through

the "enter of gra&ity.- !he mo&ement of pit"h is produ"ed by the ele&ator.

- !he stability of this mo&ement is known as longitudinal stability.

1g - :

oney "omb stru"ture perform well when

"ompressi&e stress is applied

Wing skin after "hemi"al milling pro"ess


6/15


AVIATION TECHNOLOGY

- /t is a"hie&ed by the balan"ed hori%ontal stabili%er whi"h tends to rotate the nose up

that "ountera"ting the nose down effe"t- !he ele&ator is "ontrolled by the "ontrol wheel. When the "ontrol wheel is pulled up$

the trailing edge of the ele&ator mo&es upward the tail pushes down and the nose up.

- When the "ontrol wheel is push down$ the trailing edge of the ele&ator mo&es downand the tail will be pushes up$ and the nose down.

). Roll Control

- 6oll is the rotation of the air"raft about the longitudinal a#is.

- *ongitudinal a#is is an imaginary line parallel from nose to tail and passes throughthe "enter of gra&ity.

- !he mo&ement of roll is produ"ed by the aileron.

- !he stability of this mo&ement is known as lateral stability.

- /t is a"hie&ed by the dihedral angle of the wing to the lateral a#is

- !he aileron is "ontrolled by the "ontrol wheel. When the "ontrol wheel is turned left.left aileron will raise and lowering the right aileron.

- !his will "ause air defle"ted upward on the left aileron and lowering the wing$ whilethe air passing o&er the right aileron is defle"ted downward$ whi"h raises the right

wing.

- When the "ontrol wheel is turned right$ the right aileron will raise$ and lowering theleft aileron.

- Sin"e in"rease in lift will in"rease the drag$ that this drag is far from the wing$ it will

yaw the airplane and pulls the nose of the airplane around toward the raised wing.

- !his "ondition is known as ad&erse yaw that "an "ause the airplane to enter aninad&ertent spin.

- !o minimi%e ad&erse yaw$ differential aileron is used.- !he aileron that mo&es upward tra&els further than the aileron tra&els downward.- !his will in"rease the parasite drag on the aileron that tra&els upward thus "ompensate

the ad&erse yaw "ondition.

- Frise aileron is also use to "ompensate this ad&erse yaw "ondition.- When the aileron mo&es down$ there is a portion of the leading edge aileron that

protrudes out from the wing.

- !his will produ"e additional parasite drag on the lowering wing and will balan"e theindu"ed drag on the wing that is mo&ing up.

,. Y!/ Control

- ;aw is the rotation of the air"raft about the &erti"al a#is.- +erti"al a#is is an imaginary line goes through from the top to bottom of the airplane

and passes through the "enter of gra&ity.

- !he mo&ement of yaw is produ"ed by the rudder.- !he stability of this mo&ement is known as dire"tional stability.

- /t is a"hie&ed by the balan"ed &erti"al stabili%er whi"h will point the air"raft nose

towards the relati&e wind dire"tion$ 'ust like the weather &ane- !he rudder is "ontrolled by the rudder pedal wheel.

- When the air"raft wants to turn to the right$ the right pedal is pressed$ and the left

pedal is release slightly and &i"e &ersa.

1g -


7/15


AVIATION TECHNOLOGY

- ,"tually air"raft is not turned by the rudder$ when it wants to turn0 the "ontrol wheel

must turn to the desired turn.- !his will make the lift a"ting on the air"raft will be tilted$ sin"e it a"ts in line with the

&erti"al a#is of the plane.

- !his lift for"e not only supports the airplane against the for"e of gra&ity$ but also pullsthe nose around in "ur&ed flight.

- But then the ad&erse yaw takes into effe"t. !herefore to pre&ent this e&ent$ the nose of

the air"raft is pointed to the dire"tion of the desired turn by pressing the pedal.- !his defle"ts the air to the right$ "reating a for"e that mo&es the tail to the left and the

nose of the airplane to the right.

- =n"e the turn mo&es to the desired dire"tion the pedal is released

0. Control Surf!" Con%trution

!. Surf!"% for F!3ri-Cov"r"' Air$l!n"%

- Use a simpler truss-type fabri"-"o&ered airplanes ha&e all of their tail surfa"esmade of welded thin wall steel tubing.

- !he &erti"al fin of this type airplane is built as an integral part of the fuselage$

and the rudder atta"hes to the fin with hinge pins through steel tubes weldedto both the fin and the rudder.

- !he hori%ontal stabili%er bolts to the fuselage and is held rigid with high

strength steel wires.- !he ele&ators hinge to its trailing edge in the same way as the rudder hinges to

the &erti"al fin.

1g - 7

1it"h

*ateral a#is6oll

;aw

+erti"al a#is

*ongitudinal a#is

,ileron

6udder

3le&ator


8/15


AVIATION TECHNOLOGY

- !he of the fabri" air"raft is made the same as the "onstru"tion of the wing.

- !he aileron "onforms to the shape of the trailing edge of the wing.

- !he aileron leading edge is normally "o&ered with thin sheet aluminum alloy

so it will retain its shape under all flight loads.- !he aileron is hinge a little far from the leading edge due to minimi%e the

effe"t of ad&erse yaw.

3. Surf!"% for !ll *"t!l $l!n"%

- ontrol surfa"e flutter is a serious problem in high speed airplanes- !he "ontrol surfa"e must be balan"ed at all time by designing the "enter of

gra&ity does not fall behind their hinge line.

- Usually they keep their weight down espe"ially at the "ontrol surfa"e

- >owadays they use "orrugated "ontrol surfa"e to minimi%e the weight sin"e italso has the stiffness and strength.

4. Control Confi+ur!tion

!. Ail"ron%

- e#tend from midpoint$ outward to the tip0 part of wing trailing edge.- 6ight ? left mo&es differently. 3.g.6ight aileron up$ *eft aileron down and

&i"e &ersa

- *arge transport air"raft has two sets of aileron-@ on&entional lo"ation

@ /nboard lo"ation

- Slow speed all four ailerons used to pro&ide lateral "ontrol

- igh speed only inboard fun"tioning to pro&ide lateral "ontrol.

3. S$oil"r%

- =n the top of the wing

1g - A


9/15


AVIATION TECHNOLOGY

@ Use to disrupt the airflow at top of the wing

@ 6edu"e lift- For larger airplane$ both spoilers are used to aid the ailerons in rolling the

air"raft while flying$ or as brake to slow during landing known as speed

brake8 and rollout.- For smaller plane su"h as the sailplane$ to allow rapid des"ent while still

retaining full "ontrol. !hey will pop out from the wing.

5 S$oil"ron%

- ombine spoiler and aileron

- Sometimes the spoiler "an be ba"k up for the aileron if theailerons fail through a mi#er system. !o pro&ide roll.

. E*$"nn!+"

- !ail se"tion assembly that fun"tion to "ontrol and stability of the airplane.

- *ongitudinal stability and "ontrol are pro&ided by the hori%ontal surfa"es- Dire"tional stability and "ontrol are pro&ided by &erti"al surfa"es.

- !he lo"ation of the hori%ontal tail surfa"e must "onsider the slipstreampropeller effe"t and the turbulen"e produ"e by the airflow o&er the wing.

- Sometimes the un"on&entional surfa"es "an be found in an air"raft su"h as

below-

5 St!3il!tor

- =ne pie"e hori%ontal stabili%er that pi&ots up ? down from a

"entral hinge point

- 6euires no ele&ator- o&ed by "ontrol wheel

5 Ru''"rv!tor

- ombination of rudder and ele&ator

- ount in a +-shape. an a"t as both rudder and ele&ator.

- o&es in the same dire"tion for pit"h "ontrol and in oppositedire"tions for yaw "ontrol

- e.g. Bee"h "raft Bonan%a

1g - C

,ir"raft turn left


10/15


AVIATION TECHNOLOGY

5 El"von%

- ombine wing ? ele&ator

- o&able "ontrol surfa"es on the trailing edge of a delta-shapedair"raft

- e.g. on"orde

- ,"ts together for pit"h "ontrol$ and differentially for aileron"ontrol

5 Fl!$"ron or Au6ili!r# Ail"ron

- ombines trailing edge flaps with aileron a"tion.

1g - (

,ir"raft turn right

,ir"raft "limb

,ir"raft di&e

3le&ons


11/15


AVIATION TECHNOLOGY

- !he entire trailing edge is lowered to in"rease lift by in"reasing

its "amber- ,ileron "ontrol is pro&ided by outer se"tions.

- !hese se"tions a"t 'ust like a normal aileron.

C. Strutur"% t&!t Mo'if# Lift

(. Fl!$%

- 3#tend outward from fuselage to midpoint$ to in"rease the wing "amber.

- 6ight ? left mo&es in same dire"tion- Use when land ? as speed brake

- =perate by a swit"h or handle in the "o"kpit.

!. Tr!ilin+ E'+" Fl!$%

- !he flap is set at ($ 2$ 5 and 4 degrees.- !he defle"tion of up to about 2in"reases the lift more than the drag.

- Usually this range is often use for takeoff.

- Beyond 2 normally produ"es more drag than lift$ use landing to pro&ide the

steepest des"ent path for a gi&en speed.- onfiguration of flap-

5 Pl!in Fl!$- When the flaps are lowered$ the trailing edge of the wingmo&es down and the "amber of the wing are in"reased

- !his in"reases the downwash effe"t from the wing and

in"reases both the lift and drag.

5 S$lit Tr!ilin+ E'+"

1g - ((


12/15


AVIATION TECHNOLOGY

- lowering the hinged se"tion of the under surfa"e of the trailing

edge.- /t allows the trailing edge flap in"reases drag enough to allow

the plane to ha&e mu"h steeper des"ent path.

5 Slott"' Fl!$

- , slot is formed when the flap is lower0 this will "reate highpressure area below the wing and low pressure area abo&e the

wing.

- igh energy air flows through this slot and o&er the defle"ted

flap with su"h a high &elo"ity that it does not separate from thesurfa"e e&en at full flap defle"tion.

5 7ou3l" 8 Tri$l" Slott"' Fl!$%

- Flaps are lowered from the wing$ they will fold down also.

- Between the folded flaps$ there is also slot.- !his slot a"ts as the same as the slotted flap to deli&er high

energy of air defle"ted on the top of the folded slot.

- Usually use by the large air"raft.

1g - (2


13/15


AVIATION TECHNOLOGY

5 Fo/l"r Fl!$

- !o in"rease the wing surfa"e.

- When they are lowered down$ they will sti"k out uite behind

the wing- >ow they are repla"e by the slotted flap.

3. L"!'in+ E'+" Fl!$

- Droop leading edge flap is use to in"rease more "amber so that the wingdefle"t more air.

- )rueger flap is a hinged linkage e#tends out ahead of the leading edge.- !his produ"es a spe"ial high-lift leading edge shape.

). Slot% !n' %l!t%

5 Slot - !o allow lift at high angle of atta"k.

1g - (5

Drooped leading edge flap

)rueger-type leading edge flap


14/15


AVIATION TECHNOLOGY

- Flow of the air through the slot 'ust like the slotted flap prin"iple

- /t is to maintain the aileron effe"ti&eness and lateral "ontrol through the stall.

5Sl!t - ,utomati"ally e#tended and retra"ted due to "hanges in the "hanging in

aerodynami" for"e.

- When ,o, is in"reased$ the low pressure o&er the leading edge "auses the slatto e#tend out and form a high energy air from below the wing blows ba"k

a"ross the upper surfa"e.

- ,llow the air"raft to fly at high angle of atta"k without stalling.

- Some airliners use me"hani"al power to lower the slat.

,. St!ll Stri$

- /mportant that the stall progress from the root to the tip.

- So that the aileron "an be effe"ti&e throughout the stall

- Stall strip is a triangular strip of metal on the leading edge of the wing root area.- When ,o, is rea"hed$ the triangular stall strip will break the airflow o&er the root

se"tion$ and will stall while the airflow is still smooth o&er the aileron.

- !his will "ause turbulen"e at the wing root se"tion thus bring the nose of the air"raft

down again.

0. Vort"6 G"n"r!tor%

1g - (4

Stall strip at low ,o, Stall strip at high ,o,


15/15


AVIATION TECHNOLOGY

- ,t high speed tra&el$ when the "riti"al a"h number is a"hie&ed$ a spe"ial stall "alled

sho"k-indu"ed separation o""urs on the wing.- !his is where the airflow at surfa"e rea"hes the speed of sound and sho"k wa&e is

formed 'ust behind of the point at whi"h the air is mo&ing faster

- !his sho"kwa&e will mo&e ba"k and forth and "auses the air to separate from theupper surfa"e of the wing. /t will "ause buffeting to the "ontrol.

- , &orte# generator is pla"e at the top of the wing to bring a high energy air to the

surfa"e of the wing to pre&ent sho"k indu"ed separation.

4. in+l"t- Wing tip &orti"es sa"rifi"es air"raft aerodynami" effi"ien"ies and performan"e.

- Design to benefit at "ertain speed and "ertain angle of atta"k for most 'et.- For most turboprop air"raftto impro&e lift and redu"e drag.

- Downwash from the trailing edge of the winglet blo"ks the &orti"es.

- !he leading edges of many winglets are a"tually "anted outward 4 degrees$ butbe"ause the relati&e wind indu"ed by the wingtip$ the wingtip a"tually has a E&e

,o,.

- 1art of the lift is generated in a forward dire"tion$ adding thrust to the airplane.- =ther has winglet "anted around (: degrees. !his is to add &erti"al lift and in"reases

the aerodynami" effi"ien"ies and "ontribute to the dihedral effe"t.

- Winglet also "an in"rease the fuel effi"ien"y at high speed and altitudes.

1g - (:

+orte# 9enerator

Winglet

sheet metal notes day 1

Documents