Aerodynamics - UniKL Malaysian Institute of Aviation Technology PDF

10. AERODYNAMICS! May$17,$2016$  LEARNING$OUTCOMES! On$comple>on$of$this$topic$you$should$be$able$to:$ Describe$about$aerodynamics.$ 1. Airflow$around$a$body.$ 2. Basic$aerodynamics$terminology.$ a. Boundary$layer.$ b. Laminar$and$turbulent$flow.$ c. Free$stream...

10. AERODYNAMICS! May$17,$2016$  LEARNING$OUTCOMES! On$comple>on$of$this$topic$you$should$be$able$to:$ Describe$about$aerodynamics.$ 1. Airflow$around$a$body.$ 2. Basic$aerodynamics$terminology.$ a. Boundary$layer.$ b. Laminar$and$turbulent$flow.$ c. Free$stream$flow.$ d. Rela>ve$airflow.$ e. Upwash$and$downwash.$ f. Vor>ces.$ g. Stagna>on$point.$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 2!  LEARNING$OUTCOMES! On$comple>on$of$this$topic$you$should$be$able$to:$ Describe$about$aerodynamics.$ 3. Characteris>cs$of$airfoil.$ a. Camber.$ b. Chord$ c. Mean$aerodynamics$chord.$ d. Profile$(parasite)$drag.$ e. Induced$drag.$ f. Centre$of$pressure.$ g. Angle$of$aWack.$ h. Wash$in$and$wash$out.$ i. Fineness$ra>o.$ j. Wing$shape.$ k. Aspect$ra>o.$ $ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! 3! Abdul!Razak!  10.1 AIRFLOW AROUND A BODY! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 4!  The$Atmosphere$ 1. Before$ we$ can$ consider$ how$ an$ aeroplane$ flies$ we$ must$ first$ look$ at$ the$ medium$in$which$it$operates$–$air.$ 2. The$ICAO$standard$atmosphere$states$that:$ a) The$air$is$assumed$to$be$dry.$ b) The$pressure$at$sea$level$is$1013.25$mb$(milibar).$ zo Profe c) The$ temperature$ is$ 15oC$ and$ the$ temperature$ lapse$ rate$ is$ 1.98$ oC$ per$ 1000$ _$ up$ to$ a$ height$ of$ 36,000$ _$ where$ the$ temperature$ remain$ constant.$ d) The$value$for$gravity$is$uniform$given$at$9.81$m/s2$at$sea$level.$ e) Heights$above$65800_$the$ICAO$law$states$that$the$temperature$lapse$rate$ approximately$+0.33$oC$per$1000$_$to$d44.6$oC$at$105000$_.$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 5! 1. The! graph! shows! how! the! atmosphere! has! been! divided! into!layers.! 2. For! those! working! on! large! aircraI! the! atmosphere! is! of! interest! up! to! 60,000I,! and! for! those! working! on! small! aircraI! the! atmosphere! is! not! of! much! interest! aIer! 20,000I.! ! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 6!  Pressure$ 7 psi 14. i. Defined!as!force!per!unit!area!and!measured!in!Pa!or!psi!or!mb.! ii. Starts!at!1013.25!mb!(14.7!psi)!at!sea!level,!and!falls!at!a!non!linear!rate! with!alStude.! iii. These!pressure!readings!are!absolute!pressure!readings.! iv. Example:!if!a!pressure!gauge!is!used!to!check!Sre!pressure!of!say!30!psi!it! will!read!30!psi,!but!the!pressure!in!the!Sre!is!in!fact!30!psi!above! atmospheric!(30!+!14.7!=!44.7!psi)! ! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 7!  Density$ 1219/m2 i. Defined!as!mass!per!unit!volume!(kg/m3)! ii. Starts!at!1.2!kg!per!cubic!meter!at!sea!level!and!falls!at!a!similar!rate!to!pressure.! iii. Density!can!change!depending!on!the!temperature!and!the!relaSve!humidity!(RH).! iv. If!the!temperature!drops!density!will!increase!and!if!the!RH!increase!the!density!will! decrease.! Temp dental Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 8!  Temperature$ i. Starts!at!15!oC!at!sea!level!and!falls!at!a!rate!of!about!2!oC!(1.987!actual)!per!1000!I! to!36,000!I!(11!km)! Temp 2 02. per04to capsee Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 9!  Humidity$hygrometer $ i. The!relaSve!humidity!(RH)!falls!with!alStude.! ii. RH!is!the!amount!of!moisture!that!is!in!a!volume!(m3)!of!air!compared!to! the!maximum!amount!it!will!hold!(ie!when!it!saturated).! iii. The!higher!the!humidity!the!less!dense!the!air!and!as!density!is!a!funcSon! of!liI,!so!liI!decreases!with!an!increase!in!humidity.! iv. RH!can!be!measured!using!the!wet!bulb!method!or!a!hygrometer.!The!wet! bulb!method!uses!two!temperature!thermometers.!–!one!that!is!kept!wet! and!one!that!is!kept!dry.! v. Their!readings!are!taken!and!their!differences!are!compared!on!tables!to! give!the!relaSve!humidity.! vi. Hygrometer!can!be!mechanical!or!electronic.! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 10!  speed Airspeed$ air grounded tried a) The$speed$of$the$aircra_$through$the$air.$ b) Airspeed$are$not$usually$the$same$as$ground$speed.$ c) Example:$if$the$aircra_$is$flying$through$the$air$at$140$knots$ with$a$tail$wind$of$30$knots,$then$its$ground$speed$will$be$ 140+30$=$170$knots.$ d) This$explains$why$aircra_$land$into$wind$–$the$actual$landing$ speed$is$reduced$by$the$amount$of$head$wind.$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 11!  Airflow$Around$a$Body$ When$an$object$moves$through$a$fluid$(air),$the$ molecules$of$the$fluid$are$disturbed$by$the$ object$and$move$around$the$object.$ The$studies$of$how$$ $$$$the$fluid$flow$around$$ $$$$a$body$will$be$the$$ $$$$basis$of$understanding$$ $$$$how$the$aircra_$flies.$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 12!  10.2 BASIC AERODYNAMICS TERMINOLOGY! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 13!  Streamline$ ! Streamline!–!shape!or!contour!that!presents!a!minimum!resistance!to!the!air.! ! An!imaginary!line!marking!the!path!of!a!parScle!of!fluid!from!one!point!to! another!especially!in!laminar!flow.! ! Usually!shown!as!a!line!with!an!arrow!indicaSng!direcSon!of!flow.! ! A!perfect!streamlined!form!is!similar!to!the!top!view!of!a!fish.! ! Air!flows!around!nonbstreamlined!object!"!air!swirls!into!eddies!+!streamline! distorted!"!disappear.! ! Airstream!becomes!turbulent.! ! Streamline!air!appears!as!smooth!parallel!lines.! Smoke!jets!–!introduce!smoke!into!air!"!to! observe!and!illustrate!movement!of!air! around!object! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 14! Effect$of$shapes$on$Streamlined$ Flow$ (a)$$Flat$Plate$100%$Resistance $ $$$$(b)$$Sphere$50%$Resistance! $(c)$$Ovoid$15%$Resistance $ $$$$$$$$(d)$$Streamlined$5%$Resistance$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 15! Effect$of$shapes$on$Streamlined$ Flow$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 16!  Boundary$Layer$ # A$boundary$layer$is$that$layer$of$fluid$in$the$immediate$vicinity$of$a$bounding$surface.$ # In$rela>on$to$an$aircra_,$the$boundary$layer$is$the$part$of$the$airflow$closest$to$the$ surface$of$the$aircra_.$$ # The$molecules$just$above$the$surface$are$slowed$down$in$their$collisions$with$the$ molecules$s>cking$to$the$surface.$$ # These$molecules$in$turn$slow$down$the$flow$just$above$them.$$ # Each$layer$of$molecules$in$the$boundary$layer$moves$faster$than$the$layer$closer$to$the$ surface.$ boundadeteyeVot is Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 17! # This$thin$layer$of$sluggish$air$that$clings$to$the$surface$of$ the$object$and$in$which$the$speed$change$of$the$airflow$ takes$place$is$the$boundary$layer.$ thin fluid layer above I surface · boundary = ler X cause by frictiotween muviny our face a fluid Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 18! Boundary$Layer$ Unaffected!airflow! Each!layer!experience!retardaSon!unSl! some!distance!away!from!surface! Next!layer!slowed!down!but!not!stop! Airflow!nearest!the!surface!come!to!rest! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 19! Boundary$Layer$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 20!  to parallel streamline Laminar$Flow$ of ↑ Laminar$flow$means$that$the$boundary$layer$ follows$the$shape$of$the$object$smoothly$and$ without$any$separa>on$from$the$surface$of$the$ object.$ The$airspeed$changes$gradually$$ $$$$with$increasing$distance$$ $$$$from$the$surface$$ $$$$of$the$aerofoil.$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 21!  pretparallel Turbulent$Flow$ Turbulent$flow$is$where$the$boundary$layer$is$no$ longer$smooth$and$becomes$separated.$$ The$flow$becomes$$ $$$$random$and$$ $$$$no$longer$$ $$$$follows$the$shape$$ $$$$of$an$object$.$$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 22!  Boundary$Layer$ e reduct & Laminar! mur Turbulent! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 23! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 24!  Laminar$and$Turbulent$Flow$ Transi>on$ The$point$at$which$the$change$from$laminar$flow$ to$turbulent$flow$is$complete.$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 25!  Free$Stream$Flow$ Free$Stream$Flow$is$the$airflow$around$an$object$ which$is$clean$flow,$distant$enough$to$be$ unaffected,$and$does$not$change$direc>on.$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 26!  Upwash$and$Downwash$ Updwash$and$Downdwash$are$changes$of$airflow$ direc>on$at$the$leading$and$trailing$edges$due$to$ aerofoil$design$and$angle$of$aWack.$ failin air is airflow James ↑ a Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 27!  Upwash$and$Downwash$ The!Sp!vorSces!cause!addiSonal!down!flow!(or!downwash)!behind! the! wing! within! the! wingspan.! For! an! observer! fixed! in! the! air,! all! the!air!within!the!vortex!system!is!moving!downward!(called!downb wash)! whereas! all! the! air! outside! the! vortex! system! is! moving! upward!(called!upbwash).!! An! aircraI! flying! perpendicular! to! the! flight! path! of! the! airplane! creaSng!the!vortex!paeern!will!encounter!downbwash!and!upbwash! in! that! order.! The! gradient,! or! change! of! downbwash! to! upbwash,! can! become! very! large! at! the! Sp! vorSces! and! cause! extreme! moSons!in!the!airplane!flying!through!it.!! An!airplane!flying!into!a!Sp!vortex!also!has!a!large!tendency!to!roll! over.!If!the!control!surfaces!of!the!airplane!are!not!effecSve!enough! to!counteract!the!airplane!roll!tendency,!the!pilot!may!lose!control! or,!in!a!violent!case,!experience!structural!failure.! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 28!  Downwash$ In! aeronauScs,! downwash! is! the! change! in! or direcSon! of! air! deflected! by! the! aerodynamic! acSon!of!an!airfoil,!wing!or!helicopter!rotor!blade! in!moSon,!as!part!of!the!process!of!producing!liI.! - LiI! on! airfoil! is! an! example! of! applicaSon! of! Newton's!third!law!of!moSon!b!the!force!required! to! create! the! downwash! is! equal! in! magnitude! and! opposite! in! direcSon! to! the! liI! force! on! the! airfoil.! LiI!on!an!airfoil!is!also!an!example!of!the!Kueab Joukowski!theorem!b!the!Kuea!condiSon!explains! the!existence!of!downwash!at!the!trailing!edge!of! the!wing! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 29!  Wing>p$Vor>ces$ When$high$pressure$area$on$the$boWom$of$an$ aerofoil$pushes$around$the$>p$to$the$lowd pressure$area$on$the$top$of$the$aerofoil.$$ This$ac>on$creates$$ $$$$a$rota>ng$flow$$ $$$$called$a$>p$vortex.$$ reportive terkauft Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! 30! Abdul!Razak!  aa Airflow$over$the$wing$ Tere use Airflow$under$the$wing$ moves$from$>p$to$root.$ moves$from$root$to$>p! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! meane 31! Airflow$over$the$wing$ Airflow$under$the$wing$ undeent moves$from$>p$to$root.$ moves$from$root$to$>p! yes bu essure contain whe lift Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! -Even Abdul!Razak! 32!  A380$Wake$Turbulence$ our s n Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 33!  Stagna>on$Point$ A$minute$area$in$front$of$the$leading$edge$of$an$ aerofoil$where$the$airflow$is$brought$to$rest$and$ has$zero$velocity$in$rela>on$to$the$aerofoil.$ overi Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 34!  As$the$aerofoil$changes$angle$of$aWack,$the$ stagna>on$point$does$not$change$in$rela>on$to$ the$airflow.$$ Therefore$if$the$angle$of$aWack$increases$the$ stagna>on$point$moves$down%rela>ve$to$the$ aerofoil$leading$edge$and$vice$versa.$ APPLICATION$OF$STAGNATION$POINT$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 35!  Stagna>on$Pressure$ a)The!pressure!at!the!stagnaSon!point.!Normally!is! the!same!as!the!total!pressure!or!Pitot!pressure.! b)Pitot!pressure!=!dynamic!pressure!+!staSc! pressure! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 36!  10.3 CHARACTERISTICS OF AIRFOIL! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 37!  Airfoil$@$Aerofoil$ It$is$the$shape$of$a$wing$or$blade$(of$a$propeller,$rotor$or$turbine)$ or$sail$as$seen$in$crossdsec>on.$ The$airfoil$should$provide$this$reac>on$(li_),$whilst$having$a$shape$ which$presents$the$least$possible$resistance,$or$drag,$to$its$ passage$through$air$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 38!  Airfoil$Shape$ ! ! Symmetrical!–!no!liI!at!zero!angle!of!aeack!! ! Asymmetrical!–!liI!created!even!at!small!angle! of!aeack! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 39!  Airfoil$Shape$ Medium!and!high!speed!aircraI!–!much!less! curvature!"!liI!comes!from!their!addiSonal!speed! through!the!air.! Low!speed!aircraI!–!cambered!"!not!for!high!speed! (excess!liI!as!well!as!drag)! ! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 40! Airfoil$Terminology$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 41!  Camber$ Camber!"!curvature!of!an!aerofoil!(wing)! above!and!below!the!chord!line! Camber!(curvature)!of!an!aerofoil! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 42!  CAMBER! The$curve$surfaces,$that$gives$the$aerofoil$it’s$ shape$is$called$camber.$ Normally$is$divided$into$Upper$Camber$and$ Lower$Camber$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 43!  Mean$Camber$Line$ ~ tait tengaratus a) An!imaginary!line!drawn!from!the!centre!of!curvature!of!the!leading!edge!to!the! trailing!edge!of!an!airfoil,!but!equidistant!from!the!top!and!boeom!surfaces.! b) This!is!the!same!as!the!chord!line!on!a!symmetrical!airfoil!but!will!be!curved!on!an! asymmetric!airfoil!and!not!the!same!as!the!chord!line.! ! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 44!  MEAN$CAMBER$LINE! An$imaginary$line$from$center$curvature$of$the$ Leading$Edge$to$the$Trailing$Edge$and$equal$ distance$between$upper$and$boWom$of$the$ airfoil.$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 45!  betul2 CHORD$LINE! X middle of An$imaginary$straight$line$star>ng$from$Leading$ Edge$to$the$Trailing$Edge$ aerofoil) streight e Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 46!  leading CHORD! - -trailing ege The$distance$from$Leading$Edge$to$the$Trailing$ Edge$measured$along$the$chord$line$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 47!  MEAN$AERODYNAMIC$CHORD! Previously$you$have$learned$about$wing$chord.$$ For$rectangular$wing,$$ $$$$the$chord$will$be$the$same$$ $$$$from$root$to$>p.$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 48!  But$what$about$the$ellip>cal,$taper$and$swept$ wing,$what$is$the$chord$?.$ To$make$life$easier,$we$introduce$the$terms$ Mean$Aerodynamic$Chord.$ It$is$a$chord$for$an$imaginary$rectangular$wing$ that$has$the$same$area,$aerodynamic$force$and$ posi>on$of$the$centre$of$pressure$at$a$given$ angle$of$aWack$as$the$given$wing$has.$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 49! The$Mean%Aerodynamic%Chord$(MAC)$is$simply$a$concept$ that$provides$a$means$of$expressing$the$C$of$G$loca>on$ rela>ve$to$a$percentage%of%the%distance%between%$ ! the%maximum% forward%and% rearward%distance$ along$the$aircra_$ wing$chord.$$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 50!  Average!distance!between!leading!and!trailing! edge!of!wing! Mean!chord!=!Wing!Area! ! ! ! !Wing!Span! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 51! Mean$Aerodynamic$Chord$Video$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 52!  Centre$of$Pressure$(C$of$P)$ a) All!the!pressure!differences!between!the!top!and!boeom!surfaces!of!the!airfoil!can! be!added!together!to!produce!the!total!air!reacSon!which!can!be!considered!to!act! at!a!point!called!the!centre!of!pressure!(C!of!P).! b) As!the!angle!of!aeack!increases!and!the!pressure!distribuSon!changes!the!posiSon! of!the!C!of!P!moves!forward.!Usually!reaching!a!point!about!¼!chord!length!from!the! leading!edge.! Total!LiI! PosiSon!of!lines!denotes! direcSon!of!liI! Length!of!line!denote! magnitude!of!liI! DirecSon! of!airflow! nqua change con Center!of!Pressure! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 53! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 54!  Centre$of$Pressure$ o PosiSon!of!c.p!varies!during!flight!as!the!angle!of!aeack!(AOA)!altered! a. Increase!AOA!–!c!of!p!moves!forward! b. Decrease!AOA!–!c!of!p!moves!backward! o In!normal!flight!the!AOA!usually!between!2˚$and$4˚$(seldom!below!0˚!or! above!16˚)! Small!AOA! Medium!AOA! Large!AOA! Nose!Heavy! Balance!Flight! Tail!Heavy! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 55! WING!SHAPE! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 56!  WING$SHAPE$(PLANFORM)! Planform$refers$to$the$shape$of$the$airplane’s$ wing$when$viewed$from$above.$$ The$common$shape$are:$ $ Rectangular$$ $ Ellip>cal$ $ Tapered$$ $ Sweepback$ ! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 57!  Rectangular$Wing$$ Simple$to$make,$and$common$where$low$cost$is$ important.$$ Normally$used$on$older$aircra_$! $ Increases$the$stresses$on$the$$ $$$$$$root$structure$making$it$heavier.$ $$ Excellent$slow$flight$characteris>cs$because$ stalls$begins$at$the$wing$root.$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 58! Spirit$of$St.$Louis$ Video! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 59!  Ellip>cal$Wing$$ Aerodynamically$the$most$efficient,$but$difficult$ to$manufacture.$$ if broke To need ganzi Famously$used$on$the$ Supermarine$Spiqire$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 60!  $Supermarine$Spiqire! kalan portan e Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 61!  Taper$Wing$$ Structurally$and$aerodynamically$more$ efficient$than$a$rectangular$wing,$and$easier$ to$make$than$the$$ $$$$ellip>cal$type.$ $ It$is$the$most$commonly$used$ type$of$wing$planform$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 62! P$51$Mustang! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 63!  Sweepback$Wing$$ Used$for$high$speed$aircra_.$ Most$common$design$ for$transport$aircra_.$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 64! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 65!  Aspect$Ra>o$ Aspect!raSo!is!the!raSo!of!aircraI!wingspan!to!its!mean! chord!length! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 66! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 67! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 68!  Angle$of$AWack$ a. This!is!the!angle!between!the! chord!line!of!the!airfoil!and!the! free!stream!flow.! b. In!various!manuals!it!is!called! the!alpha!angle!(α).!If!a! symmetrical$airfoil$is!given!a! posiSve!angle!of!aeack!the! speed!of!the!airflow!over!the! top!surface!increases!and!the! speed!of!the!airflow!under!the! airfoil!decreases.!Hence! produced!liI.! c. For!an!asymmetric$airfoil$liI! can!be!generated!at!zero!angle! of!aeack!and!even!at!small! negaSves!angle!of!aeack.! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 69! Separa>on$and$Turbulent$at$ Various$AoA$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 70!  trailing = AOIC) leadinger tran hig Angle$of$Incident$ ↑ a) The! angle! the! chord! line! makes! with! the! longitudinal! datum! line! of! the! aircraI.! Fixed!for!most!aircraI!wings!but!variable!for!many!aircraI!tailplanes.! b) When!the!leading$edge$of$the$wing$is$higher$than$the$trailing$edge,$the$angle$of$ incidence$ is$ said$ to$ be$ posi>ve.! The! angle$ of$ incidence$ is$ nega>ve$ when$ the$ leading$edge$is$lower$than$the$trailing$edge$of$the$wing.!! c) The!angle!of!incidence!may!change!from!root!to!Sp.!If!it!increases!from!root!to!Sp!it! is!said!to!Washbin,!if!it!decreases!it!is!said!to!Washbout.! ↑ root tip = wash in Viceverse Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 71!  Wash$In$&$Wash$Out$ Most$ airplanes$ are$ designed$ so$ that$ the$ wings$ will$ stall$ progressively$ outward$ from$ the$ wing$ roots$(where$the$wing$aWaches$to$the$fuselage)$ to$the$wing>ps.$$ This$ is$ the$ result$ of$ designing$ the$ wings$ in$ a$ manner$ that$ the$ wing>ps$ have$ less$ angle$ of$ incidence$than$the$wing$roots.$$ Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 72!  Wash$In$&$Wash$Out$ Wash!in!:!! – Angle!of!incident!increase!from!root!to!Sp! – Tip!will!stall!1st! Wash!out!:!! – Angle!of!incident!decrease!from!root!to!Sp! – Root!will!stall!1st! ⑭. Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 73!  Fineness$Ra>o$ thinnesinfoil - The$fineness$ra>o$is$a$measure$of$how$thin$is$the$ aerofoil.$! Prepared!By:!Wan!Nur!Shaqella!Bte!Wan! Abdul!Razak! 74!