JL McClellan: P51 draft Copyright 2005 p 1 of 32

Editorsnote:The Design Analysis article was originally

publishedintheJuly,1944issue,Volume43,number7, of Aviation magazine, published by McGrawHillPublishingCompanyofNewYork,NY,USA.

The article on design refinements was originallypublishedintheJuly,1945issue,Volume44,number7, of Aviation magazine, published by McGrawHillPublishingCompanyofNewYork,NY,USA.

Thisreconstructionisderivedfrommicrofilm.Thesource is University Microfilms International,Publication No. 364 (Aviation Week and SpaceTechnology), ReelNo. 20(January1944December1944) and Reel No. 21 (January 1945 December1945). Thesourcewastightlyboundvolumes,sothatthereissomedistortionoftheimages,especiallynearthe binding. It has not been practical to remove orcompensate for all the distortions, so none of theillustrationsinthisreconstructionshouldbeconsideredreliablesourcesastofinedetailsofshape,proportionorspatial relationship. The distortions are, in general,small, and should not detract from a generalappreciationofarrangementandrelationship.

The editor has attempted to represent the originallayout of the article, but there are some exceptions.Limitationsinthecompositingtoolscauseadifferenceinthetextflowrelativetotheillustrations,comparedtotheoriginal,sothatsomechangeshavebeenmade,tocompensatepartiallyforthateffect,andthetabulardatahavebeenremovedfromtheflowoftextandbrought

togetheronasinglepageafterthetext,partlytomakethemmoreaccessible,andpartlytosidestepproblemswithpagelayout.

TheDesignAnalysisarticlewasoneina series ofdesign analyses published in Aviation during the waryears, betweenMay1943andNovember1945. Thesubjects were the Bell P39 Airacobra, Curtis C46Commando, Fleetwing BT12, Douglas A20 Havoc,Bristol Beaufighter (British), deHavilland Mosquito(British),NorthAmericanP51Mustang,LockheedP38Lightning,FockeWulfFW190(capturedGerman),Boeing B17 Flying Fortress, North American B25Mitchell (specifically, the B25HandB25J models),Mitsubishi Zeke 32 Hamp (captured Japanese),Consolidated Vultee B24 Liberator, Fairchild C82Packet,andMesserschmittMe262(capturedGerman),withonearticledealingspecificallywiththeMe262'sJumo 004 jet engine. Some of the analyses wereauthoredbyseniormembersofthedesignteamsattheoriginal manufacturers, while others were written bystaffeditorsofAviationmagazine.

The original articles were copyright to theirrespective sources the employers of the authors,followinggeneralpracticeofthetime.

This reconstruction is compilation copyright JLMcClellan,2005.

RIORTOWORLDWARIIitwasgenerally agreed amongaeronautical engineers and

military aviation authorities that itwas impracticable, if notimpossible, to design an airplanecapableofaccomplishingmorethanonetypeofmilitaryoperation.

PThe record of North American's

P51 Mustang fighter proves,however,thatitisbothpossibleandpractical to create a single basicdesign that can be modified, as

military needs dictate, to keepabreast of requirements. Amongsingleseat, single engine fighters,the Mustang has been credited asthe best lowaltitude cooperationalcraft, the most versatile divebomber, the fastest highaltitudefighter, and the plane with thegreatestrange.All this has beenachieved by a

planewhosebasicdesignandmostof its original specificationsremainedunchanged. Newmodels

incorporatedequipmentanddesignrefinements but retained thedesirable advantages of precedingversions.The original Mustang, designed

andbuiltfortheBritishinlessthan120days,wasintendedforlowandmedium altitude work. It was alowwing allmetal monoplanepowered by a 12cyl., VtypeAllisonengineof1,150hp.,anditwascreditedwithcloseto400mph.speed. RAF pilots said it washighly maneuverable, had nocranky characteristics; and, forthose early days, it was heavilyarmed, with .50cal. guns, one oneachsideoftheengine,andone.50andtwo.30cal.gunsineachwing.Aguncamerawasmountedin theleftwing.

JL McClellan: P51 draft Copyright 2005 p 2 of 32

DESIGN ANALYSIS NO. 7

The North American P-51 MustangBy WILLIAM R. NELSON, West Coast Editor, AviationAVIATION'S graphic and thoroughly detailed engineering dissec-tion of NAA's great fighter initially completed less than fourmonths after design inception, then fourfoldly hailed for low-altitude cooperation, dive-bombing versatility, high-altitudefighting speed, and long-range prowess.

In its P51 version for theUSAAF, the Mustang retainingits high maneuverability withsomewhatincreasedspeedquicklyacquiredfameasatrainbusterbyvirtueofitstwo20mm.cannonineach wing. Stripped of guns andwith a K24 camera, it became awidely used scouting andreconnaissanceplane.The invasion of Sicily was

highlighted by reports of aphenomenal new secret fighterdive bomber. This craft whichcombat men quickly dubbed theInvader wastheA36versionofthe Mustang. Retaining thecharacteristics of its fighter andlevelbomberforbears,theA36wasequippedwithdivebrakes,two500lb.bombs, andsix50cal. machineguns.Next revision retained the basic

designandusesofpreviousmodels,butincreasedthespeedwithsinglestage, singlespeed supercharger.Auxiliary fuel tanks gaveconsiderably increased range.Carriedwerewingbombracksandfour50cal.guns,twoineachwing,maintaining striking effectivenessagainstgroundtargets.

JL McClellan: P51 draft Copyright 2005 p 3 of 32

Tabulated weights ofprincipal assemblies.

Packard-built Rolls-Royce Merlin1,500 hp. engine used in Mustang.

Another revision introduced the1,500 hp. Packardbuilt, RollsRoyce Merlin engine with twospeedtwostagesupercharger. Alsoaddedwereremovablebombracks,

depthcharges,chemicaltanks,andauxiliary fuel tanks. Armamentwasfour50cal.guns. Speedandceiling both went up, whereupontheMustangwasofficiallycredited

with the highest ceiling (over40,000 ft.) and the greatest speed(over425mph.)ofanyfighterinexistence. Soon the Mustang wasaccompanying our heavy bombers

JL McClellan: P51 draft Copyright 2005 p 4 of 32

1. Radiatorforwardairscoop2. Radiatorforwardairduct3. Coolantradiatorassembly4 Oilradiatorcover5. Oilradiator6. Oilcoolerairinletdoor7. Spinnerassembly8. Enginemountfrontframeassembly9. Enginemountassembly10. EnginetopcowlingRH11. EnginetopcowlingLH12. Wingnoseassembly13. WingpanelRH14. WingtipRH15. AileronRH16. Ailerontrimtab17.Windshield18. Cockpitexithatch19. CockpitexithatchpanelLH20. CockpitexithatchpanelRH21. RadioaccesswindowRH22. RadioaccesswindowLH23. Oxygenaccessdoor24. Oxygenreardoor25. Fillet

26. Fillet27. Fillet28. Elevator29. Elevatortrimtab30. Verticalstabilizer31. Verticalstabilizertip32. Ruddertrimtab33. Rudder34. Elevatortrimtab35. Elevator36. Horizontalstabilizer37. Fillet38. Tailwheelunitassembly39. TailwheeldoorLH40. TailwheeldoorRH41. Radiatoraftairscoop42. Cover43. Fuselageforwardsection44. Coolantradiatoraccesscover45. Wingflap46. Wingcenterrib47. Wingtofuselagefillet48. Wingtofuselagefillet49. Gunbaydoor50. Ammunitionbaydoor

51. Bombrack52 AilerontrimtabLH53. AileronLH54. WingtipLH55. WingpanelLH56. Landinglight57. Landinglightcover58. Landinggearfairing59. 27smoothcontourwheel60. Mainlandinggearshockstrut61. Wingtofuselagefairing62. Wingnoseassembly63. Mainlandinggearaccesscover64. Intermediaterearenginecowling65. Wingcenterbulkhead66. Exhauststackfairing67. Firewallassembly68. Maingearfairingdoor69. Fueltankdoor70. Fueltank71. Engineloweraftcowling72. Enginelowerintermediatecowling73. Enginelowerforwardcowling74. EngineintermediatecowlingLH75. EngineintermediatecowlingRH

JL McClellan: P51 draft Copyright 2005 p 5 of 32

Three-view drawing of P-51 Mustang , with leading dimensions.

on their longest missions, since itpossessed the longest range of anysingleenginefighterinthewar.Theseachievementsare, froman

engineering standpoint, remarkable because they were accomplishedby a plane that does not to anyextentembodypreviouslyunknownengineering features, but ratheremployed refinements of knowacceptedpractices.Such performance is attained by

close attention to aerodynamiccleanness of design, employing anefficient, lowdrag, laminarflowairfoil,amodificationofanNACAdesign. Seconddegree curves,calculated as mathematicalexpressions, are employed forexternal lines of fuselage, fillets,ducting,andairscoop.The air scoop is located below

and just aft of the center of thefuselage, where it was found bywindtunnelteststocreatelessdrag,whileoperatingefficiently.Bothoiland coolant radiators are containedintheairscoop.An identifying feature of the

Mustang isthesquarewingand tailsurfacetips,whichtendedtopreventstalling and to maintain excellentaileroncontrol.Thefuselage,ofsemimonocoque

construction, is divided into threemain sections:Enginemount,main,and rear section, all joined withbolts. With exception of cockpitarmor fore and aft, fuselage isentirelyAlcladandaluminumalloyextrusions.Engine mount is a box beamof

Alclad sheet and extruded parts,designedsothat theenginecanberemoved as a unit. Mount isattachedatthefirewallbyfourbolts.Main fuselage section is

constructed around four 24STextruded longerons, intermediateframes, Alclad covering, andstringers. Stainless steel sheet andarmor plate firewall form forwardbulkhead.Aturnovertrussof24STextrusionsandformedsheet protectthe pilot. Upper longerons areextruded Hsections which extendaft from firewall, tapering to Tsection and terminating near rearsection. Lower longeron, Hbeamand Uchannel, extends full lengthofsection.Eight riveted and bolted

assemblies which comprise mainfuselage section may be removed

JL McClellan: P51 draft Copyright 2005 p 6 of 32

Five main sections of P-51

Exploded drawing of enginecowling and framework.

and replaced as units. They are:Firewall, turnover truss, upperdeck, left and right side panelsubassemblies, radio shelf, webassembly,andlowersectionwithairscoop.Comfort and safety are given

consideration in the design of thecockpit seat, which accommodatesthe seattype parachute and has akapok backcushion life preserver,provisions for heatingand cooling,and protecting armor plate at thefirewallandseat.The combination armorplate

firewall protectsthepilot fromlineof level flight to approximately 20deg.belowit,alsoagainstfirefromthe engine. Firewall is facehardened steel armor, except asectionatcenterofstainlesssteeltoprovide room for oil tank. Aftprotectionisprovidedbytwoplatesof facehardened steel behind theseat.Protection and visibility are

afforded by windshield, rearwindow, and cockpit enclosure.Forwardflatsectionofwindshieldisbulletproof, 5ply laminated glass,11/2in.thick,slanted31deg.fromvertical,beingthebestcompromise

JL McClellan: P51 draft Copyright 2005 p 7 of 32

Main air scoop,situated beneath fuselage, is fitted with adjustable discharge flaps orscoops to regulate airflow through both oil and engine coolers.

Engine controls. (1) Engine throttle control;(2) throttle stop release; (3) throttle nameplate; (4) adjustable throttle stop; (5) quad-rant to bellcrank flexible control; (6), (11),(12), (15), (16), (25) fairleads; (7) flexiblecontrol; (8) propeller control bracket; (9)propeller control bellcrank; (10) emergencyboost control handle; (13), (14), (17), &(18) control rods to jackshaft; (19) carbure-tor air control; (20) flexible air control; (21)air control support; (22) jackshaft, hot aircontrol; (23) hot air door actuating rod; (24)air shut-off control rod; and (25) shut-off rodsupport.

Exhaust system and vent lines. (1) Exhaustshroud to keep heat from sparkplugs; (2)gasket, with lockplate (3) and nut (4) whichhold jet exhaust stacks (5) in place infairing (6); (7) drain from mixture boost (8);(9), (10), & (11) blast tubes for coolingsparkplugs situated on exhaust side ofcylinders; and (12) & (13) parts forminggenerator blast system for coolingpurposes.

JL McClellan: P51 draft Copyright 2005 p 8 of 32

Fuel system. (1) Fuel strainer; (2) Parker primer pump' (3) engine driven fuelpump; (4) selector valve with handle; (5) booster pumps on tanks; (6) fuelgages; Outer streamlined tanks, used for ferrying or for long distance flights,are droppable via the bomb release. Primer, operated manually, draws fuelfrom strainer and injects it directly into engine.

Engine mount. Detail A is Lord shear rubber bushing;B, front Lord mounts; C, carburetor air inlet

JL McClellan: P51 draft Copyright 2005 p 9 of 32

Engine coolant system. Here (1) is cool-ant header tank, vented at 2, which con-nects through pipe 3 to radiator 4,returning liquid by pipe 5, to pump 6.Supercharger cooler is supplied by 7 and8. System is filled at plug 9.

Air ram scoop for carburetor. Byoperating shutter at left and blast gateat right, pilot can regulate bothtemperature and pressure of air goinginto carburetor. Detail (upper left)shows construction of vibration-absorbing connection to base ofcarburetor.

JL McClellan: P51 draft Copyright 2005 p 10 of 32

Oil system showing hopper tank at center with dilution solenoid aboveand radiator at rear. Oil leaves engine by upper of two pipes (lower left),going directly to radiator, thence to top of tank, through hopper in tank,and back to engine oil pump through large pipe from bottom of tank.Small pipe leading into deliver pipe at lower left is for oil dilution.

for visibility, protection, andaerodynamiccontouring. Sideandupper panels of windshield are of3/16in.safetyplateandtransparentplastic.Windshieldcowlingextendsfromlowerforwardendofglasstofirewall and down to upperlongeron.Over instrument panel a shroud,

integralwithwindshield,extendsaftwith a circular rubber extrusion to

protectpilot.Thisshroudsupportswindshield defroster, optical gunsight, and handholds, and it alsoeliminates instrument glare in thewindowglass.Cockpit enclosure consists of

upperandsideplasticpanels,eachin two sections, forward oneforming a sliding window withlockinghandle. Rightupperpanelhinges upward; left panel hinges

downward against fuselage. Bothhave locks controlled from insideand outside. Hood is attached byfourhingesonupperlongerons.Anemergencyreleasepermitsenclosureto be removed or jettisoned inemergency.AftwindowsofmoldedLucitefit

fuselage contour andareremovableforaccesstoradiobehindpilot.Aftofradio,plywoodbulkheadprevents

JL McClellan: P51 draft Copyright 2005 p 11 of 32

Wing panel is built up on 19 pressed ribs and two spars of 24STAlclad. Insert shows proportion of wing surface taken up by flapand aileron. Wing tip has single spar and pressed end. Details are

forgings. Detail A is front spar-to-fuselage bracket; B is pilot's foot-rest and seat bracket and C is rear spar-to-fuselage connectingbracket. Others are aileron and flap hinge brackets.

draftandkeepsobjectsfromrollingaftandfoulingcontrols. Nutplatesatcenterofbulkheadsecureoxygenbottles.Therearfuselagesectionconsists

oftwo24STlongerons,ashelfandfive formers of 24ST, three solidbulkheads,andAlcladskin.Wing is cantilever stressedskin

design in two sections, bolted atcenter.Eachconsistsofmainpanel,removable tip, aileron, and fulltrailingedgeflap. Winghasangleofincidenceofapproximately1deg.atrootanddihedralof5deg.along25 percent chord line, to givestability.The 25 percent chord line is

perpendiculartolongitudinalaxisofairplane. Wing area, includingailerons,is233.19sq.ft.,withspanof36ft. 5/16 in. anda taper ratioof.499.Main wing panel consists of a

main spar, rear spar, pressed ribs,andextrudedstringerscoveredwithalloy sheet. Space is provided atinboardendforselfsealingfuelcell,partofwhichislocatedinfuselage.Agunbayisineachwingpaneltoaccommodate guns, ammunitioncontainers, and chutes. Mainlandinggearretractsintowheelbayintheinboardleadingedge.Main structural member of wing

is forward or main spar, of twosections of of 24ST sheet splicedtogether. Inboard spar section isfabricated of .129in. thick 24ST,withangleflangesalongbothupperandloweredgesforsparcaps. A.25in. thick24ST bar is riveted toinner side of upper cap betweenstations0and85.5.Rearsparisformedoftwosheets

of 24ST spliced at station 128.6.Upper cap is reinforced by a .09124SOanglebetweenstations0and92.5. Ribs and formers areapproximately12.5in.apartandareof24SO,heattreatedafterformingto24ST.Atleadingedge,winghassweepbackof3deg.35min.32sec.Aspectratiois5.815.Each aileron has two spars and

twelve flanged ribs covered with

JL McClellan: P51 draft Copyright 2005 p 12 of 32

Flaps are made of 24ST with Alcladskin. Stiffness is provided by 15main ribs and 13 nose ribs.

Ailerons are built of 24ST withplastic tab. A metal diaphragmretains aerodynamic smoothness ofjoint with wing.

24ST. The forward spar is Ushaped 24ST Alclad, and ribs are24SOhattreatedto24ST. Trailingedgeis24STsheetreinforcedwithaluminumsupportsandplasticribs.Threeaileronhingebracketsboltedtotheforwardsparprovidebearingattachmentpoints.Ailerons are dynamically and

statically balanced. Internalaerodynamicbalanceisobtainedbya diaphragm attached to forwardedgeofaileronandsealedtotherearsparbyfabricstrip.

Phenolfiber trim tabs aremounted in each aileron by threehingebearings. Ametalhorntabprovides attachment for actuatingrod. Lefttab,adjustableinflight,is operated by a knob on controlpedestal. Angular travel, 10deg.upand10deg.down,islimitedbystopsoncables.Ailerons are conventionally

controlledbythestick,andtomeetvariationsinspecificationstheycanbeconnectedforangulartravelof10,12,or15deg.

Structure of the 24ST Alcladcovered wing flaps is two Alcladspars, 13 nose ribs of 24SO heattreated after forming to 24ST, 15main ribs, and a series of rolledsectionstringers, all of24ST. Theflaptrailingedgeisformedfromasingle24STsheetreinforcedwith27tapered hatsection supports. Theflapsarehingedonthreesealedballbearings, and are hydraulicallycontrolled by a lever selects andholdsanycorrespondingpositionoftheflaps.

JL McClellan: P51 draft Copyright 2005 p 13 of 32

Main fuselage with firewall, front and rear wing attachment fittings,and airscoop underneath. Details A and B are forged fittingsthrough which pass bolts holding engine mount and firewall.

Fuselage wing fittings are forgings carrying bolts for attachment ofwings.

Stabilizer is full cantilever, noadjustable,withdetachabletips,andisfixedatapositive2deg.angleofincidencerelativetothelongitudinalaxisoftheairplane.Forwardandaftsparsareof24STAlclad. Flangedribs are formed of 24SO Alcladheattreated to 23ST, as are sixextruded stringers. Dual stringersare on the lower covering.Stabilizer tips are of 52S, 1/2Hstock on two ribs. Area isapproximately28sq.ft.,andspanis13ft.21/8in.Elevator incorporates 18 flanged

ribs,frontspar,trailingedge,andashort intercostal beam, all 24STAlclad. Covering is fabric withAlclad leading edge extending tomainspar,exceptforthatportioncutoutforelevatorhingefitting. Rightand left elevators areinterchangeable, fastened tostabilizer with five sealed ballbearing hinges, and are staticallyand dynamically balanced. Staticbalance is by a 131/4lb. leadweight attachedtooutboardendofleadingedge. Totalelevatorareaisapproximately13sq.ft.,andangularmovementbythecontrolstickis30deg. up and 20 deg. down. Each

elevatorhasanadjustabletrimtabapproximately 411/32 in. by 321/16in.Finiscomposedoffrontandrear

spars of 24ST Alclad and ribscovered with 24ST Alclad sheet.Tip is on two ribs, and skin isstiffened spanwise by light rolledstringers.Areaoffinis9.61sq.ft.,and it is set 1 deg. to the left ofcenterlineofrearbeam.Rudder consists of spar, 20

flanged Alclad ribs, V trailingedge,andashortbeaminfrontoftrim tab, which is covered withfabric, and 24ST sheet coversleading edge back to main spar,except cutout for rudder hingefitting.Therudderishingedtofinwiththreesealedballbearingsandisdynamicallybalancedbymeansof 16.6lb. lead at top. Anadditional balance weight atbottom of leading edge reducesstaticunbalance. Areais10.4sq.fr. and angular movement is 30deg. each side of neutral.Operation is by pedals throughcables.Phenolfiber trim tabs on

elevatorsandrudderarehingedbythree sealed needle bearings.

Rudder tab is controllable fromcockpit,andangulartravelis10deg.up and 25 deg. down, limited bystopsoncable.Landinggear is threepoint, with

two 27in. main wheels and fullswiveling, steerable 12.5 in. tailwheel, hydraulically retractable.Mainwheelsretractintowingwellsandtailwheelintofuselage,allfullyenclosed.Except for hydraulic main gear

downlock pin, landing gear locksareactuatedfromthecontrolhandlebellcrank. Cables from bellcrankactuatetailgearuplatchanddownlockpin. Apushpullrodfromthelower end of the control handleworks lock system in main wheelbay.Main landing gear magnesium

support casting is bolted to frontspar at the outboard end of thewheelwell. Hydraulicstrutsonthefront spar retract the gear inboard.A springloaded, hydraulicallycontrolled pin locks main geardown.Tail gear is mounted on a

magnesiumcasting bolted to lowerlongerons. Shock strut assemblyincludes cylinder, piston, torque

JL McClellan: P51 draft Copyright 2005 p 14 of 32

Main fuselage is built on four extruded 24STlongerons with heavy frames and a few lightstringers. Turnover truss is built of 24STextrusions and sheet for pilot protection. Webassembly is shown at bottom

tube, and post housing whichsupports axle. Gear is steered bycables from rudder bellcrank.Fairingdoorsarehingedatside,anda link pulls them up as gear isretracted. Tail wheel is unlockedwith stick in the forward positionduringtaxiingandparking.Emergency lowering of landing

gear is accomplished by pushingdowncontrolhandleatleftofseat,alsorelievinghydraulic pressure inretracting struts with emergencyknobincockpit, whichcausesdeartodropofitsownweight.Pilotthenyaws plane until gears engagedownlocks.Cylinder, connected to brake by

aluminum alloy tubing, furnishespressure for the Goodyear multipledisk brake, via separate hydraulicsystemcontrolled by pedals. Thispressure is relieved by a springwhen pedal is released. Parkingbrake is controlled by depressingbrakepedalsandpullingknobbelowinstrument panel. Pressure isretaineduntilreleasedbydepressingbothbrakepedals.LatestmodelofP51ispowered

by a 12cyl. Packardbuilt RollsRoyce 1,500 hp. V1650 liquidcooledenginehavinganaftercoolertoreducechargetemperature.Inductionsystememploysatwo

speed, twostage supercharger withlowgearratioof6.391:1andhighgear ratio of 8.095:1. Pilot may

JL McClellan: P51 draft Copyright 2005 p 15 of 32

Cockpit inclosure, with floating back cushion and armored seat back.Heavily framed center glass (top left) is bullet proof.

Fuselage rear frame, with diagram givingpositions of elevator and rudder controlframes and fin attachment forging.

JL McClellan: P51 draft Copyright 2005 p 16 of 32

Left: Rudder is fabric-covered 24ST leading edge under fabric.Plastic tab is carried on three hinges. Rudder-operating horn is aforging (shown at bottom of rudder, both views)

Right: Two views of fin. This is built of 24ST Alclad with rolledstringers and is covered with Alclad sheet.

Elevator is built of 24ST frame with fabric covering. Leading edgeis 24ST under fabric. Trim tab, made of plywood, is operated byhorn near center. Balance weights are concealed in stabilizer.Elevator control is through 3-bolt coupling at inside end.

Stabilizer is full cantilever type with Alclad frame and covering.Half-hard 52S is used for the tips, built on two ribs.

JL McClellan: P51 draft Copyright 2005 p 17 of 32

1. Cockpitfluorescentlight2. Crashpad3. Fluorescentlight4. Gunsight5. Throttle6. Compass7. Clock8. Suctiongage9. Manifoldpressuregage10. Remotecontactor11. Altimeter12. Directionalgyro13. Flightindicator

14. Tachometer15. Oxygenflowblinker16. Mixturecontrol17. Propellercontrol18. Boostcontrol19. Landinggearindicator20. Airspeedindicator21. Bankandturnindicator22. Rateofclimbindicator23. Coolanttemperatureindicator24. Oiltemperatureandfuelandoilgage25. Oxygenregulator26. Enclosureforemergencyreleasehandle

27. Engineinstructionplate28. Controlstickgrip29. Gunandbombcontrolpanel30. Parkingbrakecontrolhandle31. Parkingbrakeinstructionsplate32. Engineprimer33. Oxygenpressuregage34. Oxygensystemwarninglamp35. Bombcontrolswitch36. Landinggearcontrols37. Boosterpumpswitch38. Superchargercontrol39. Superchargerwarninglight40. Starterswitch41. Oildilutionswitch

P-51 Cockpit Layout

JL McClellan: P51 draft Copyright 2005 p 18 of 32

42. Ignitionswitch43. Compasslightcontrol44. Gunsightlightcontrol45. Lefthandfluorescentlightcontrol46. Fuelvalvecontrol47. Hydraulicpressuregage48. Emergencyfairingdoorcontrol49. Hydraulichandpump50. Airplanerestrictionplate(top)51. Cockpitenclosurehandle52. Generatordisconnectswitch53. Batterydisconnectswitch54. Pitotheaterswitch

55. Landinglightswitch56. Positionlightswitches57. Ammeter58. RHfluorescentlightswitch59. Circuitbreakerswitch60. SCR522radiocontrolbox61. Cockpitlight62. SCR535radiocontrolbox63. Mapcase64. (Restricted)65. Rightfueltankgage66. Hotaircontrol67. Pilot'srelieftube68. Slidingwindowlockhandle(below)

69. Carburetormixturecontrol70. Signalpistoldischargetube71. Coolantradiatorscoopcontrol72. Oilradiatorscoopcontrol73. Quadrantfrictioncontrol74. Flapcontrolhandle75. Carburetoraircontrol76. Ruddertrimtabcontrol77. Ailerontrimtabcontrol78. Elevatortrimtabcontrol79. Bombcontrolantisalvoguard80. Leftfueltankgage81. Defrostercontrol

select cold rammed air; cold,unrammedfilteredair;orunrammedhotair, asnecessary. TheBendixStrombergdoublethroated,injectiontype,updraftcarburetorisfittedwitha doublediaphragm accelerationpump, automatic mixture control,fuelpressureregulator, fuelcontrolunit,andthrottle.Automatic manifold pressure

regulator limits maximum boostwhen below full throttle andmaintains predetermined pressurefor any given position of throttlelever.Ignition is provided by two

magnetos of the rotating magnet

type, the right hand one beingconnected to booster coil whichsupplies high tension current whenstarting.EnginemountconsistsoftwoY

shaped24STboxbeamsstiffenedbybuiltup cross members of 24STAlclad.Forwardframeincorporatesleadingedge,andfrontductsectionofcarburetorairscoopandaftframeattaches to the twobeamsnearthecenter. Engine is supported onrubber mountings between sidebeams. Mount is attached tofirewallbyfourbolts.Cowling, providing maximum

accessibility to both engine andaccessories,consistsof24STAlcladformers and seven removablepanels.With adoption of RollsRoyce

engine, the Mustang was equippedwith11ft.2in.fourbladeHamiltonStandard Hydromatic propeller,controlled by a governor whichmaintains selected propeller speed.Spinner is a streamlined spunshellofaluminumalloy.Fuelissuppliedfromselfsealing

cells, one in each wing, and formauxiliary tanks when fitted. Fuelflows from tanks through asubmerged booster pump to dualcheck valve, then through selectorvalve and strainer to enginedrivenfuel pump and carburetor. Whenauxiliarytanksareused,fuelpassesthrough the selector valve to mainfuelline.Theboosterpumpswhichboost fuel to engine pumpat high

JL McClellan: P51 draft Copyright 2005 p 19 of 32

Rudder controls with rear wheel steering mechanism at A and wheel lock at B. C isheavy rear bracket for carrying rear steering stresses.

Guns and armor. (1) & (2) Ring sights;(3) & (5) ammunition boxes; (4) machineguns; (6) & (7) ammunition chutes; (8),(9), (11) & (13) armor plate; (10) bullet-proof windshield; (12) optical gun sight;(14) detachable Plexiglas side panels.

altitudes operate as emergencypumps in event of enginepumpfailure. Onlyonebooster pumpisoperatedatatime.Fuel strainer and handoperated

engineprimingpumpareprovided,and entire system is suitable foraromaticfuels. Droppable ferryingorcombatmaybeinstalledonbombracks when bombs are not beingcarried, fuel being withdrawn byenginedriven pump. Pressure issupplied to ferrying tanks byconnecting them to vacuum pumpexhaust.Oil flows from bottom of 12.3

gal.oiltank(forwardoffirewall)tooil pump which delivers throughCuno filter to moving parts ofengine. Scavenger pump in sumpdeliversittooiltank,eitherdirectlythroughathermostaticcontrolvalve,havingabypass,ortoradiatorandthenback to tank, dependinguponoiltemperature.Selfthawing oil radiator is

forward of coolant radiator insidescoop. Airflow through scoop isregulated by outlet flap,thermostatically controlled. Flap

JL McClellan: P51 draft Copyright 2005 p 20 of 32

Fuselage electrical installation, showing control above air scoop for automaticregulation of oil and coolant temperatures, storage batteries, navigation light(upper right) and (detail A) methods of making connections.

Left landing wheel of Mustang.(1) Shock strut; (2) fairing; (3)wheel with dust cap; and (4) 27-in. tire.

can be controlled form the cockpitfor emergency operation, and asurge valve, integral withthermostaticvalve,permitscoldoilat excessive pressure to bypassradiator completely and return totank.Three systems engine oil,

engine coolant, and aftercooler coolMustang'sRollsRoyceengine.Engine cooling systemutilizes a

centrifugal pump which deliverscoolantintojacketonlowerexhaustsideofeachcylinderblock,whenceit passes to cylinder head throughtransfer tubes and out throughmanifolds on intake side of head,discharginginto header onfront ofengine,fromwhichitflowsthroughradiator.Secondary aftercooling system,

which reduces temperature ofsupercharged fuelair mixture,consists of expansion tank, heatexchanger, and coolant pump.Coolantflowsfromexpansiontank

to pump, through radiator andsupercharger case, and through ajacket between superchargerimpellers, cooling air before itpasses into second stage impellerchamber. Coolant thenpasses intoheat exchanger and cools air fromthesecondstagebeforereturningtoexpansion tank. Scoop withthermostatic exit flaps provides airfor oil, engine, and aftercoolantradiators and is located beneathfuselage aft of cockpit, where itcauses less drag than if fartherforward. Athighspeed, jet actionfromtheheatedaircompensatestoalarge degree for internal air drag.Flamedampeningexhauststacksoneither side contribute to speed byexerting a jetpropulsion effect ofapproximately200hp.TheMustang'selectricalsystemis

24v. d.c., single wire, groundedtype, most of the wiring open,supportedbyclips. Enginewiring,because of possible radiointerferenceandvibrationalstress,isshieldedandsupportedbyconduit.

JL McClellan: P51 draft Copyright 2005 p 21 of 32

Control stick. Center connection operateselevators, while rocker with forked ends movesailerons.

Elevator and elevator tab controls are by cable from cockpit. Tab rear controls aredetailed at A. Cable to tabs is operated by handwheel, to which is connected anindicator driven by small gears, as shown in detail B.

Currentissuppliedbya34amp.hr. battery, aft of seat, charged byenginedriven generator.Connectionwithelectricalsystemisthrough solenoid switch. A 100amp. highspeedgenerator suppliescurrent through a relay, whichserves as generator cutout. Avoltageregulatormaintainspotentialat28.

Radioequipmentconsistsofsetsfor communication with otheraircraft or ground. Antenna is aforeandaft, verticalmast type.Receivers and transmitters are aftofseat.Gunnery equipment consists of

fourfixed.50cal.gunsinpairsinwings, in canted position, rotated60 deg. to prevent protuberances.

Theyare adjusted to converge firewith center line of airplane at 300yd.Lateraladjustmentof1/2deg.isprovidedoneitherside,andgunsarequicklyremovablethroughdoorsinupperwingsurface.Ammunitionisfed to top sides of guns throughstainless steel chutes. Cases andlinks are ejected through metalchutesinlowerwingskin. Allfour

JL McClellan: P51 draft Copyright 2005 p 22 of 32

Aileron and trim tab controls. Detail A showsoperating mechanism of left hand tab, con-trolled from cockpit by turning knob. Travelof cables is restricted by stops, andadjustments are made by means ofturnbuckles. B is detail of right aileron tabadjustment, set on ground and showsmethod of attaching and actuating aileroncables by link from stick adjustment.

guns fire simultaneously, controlbeing by switch on control stick.Sightingisthroughopticalgunsightor auxiliary ringandbead sight.Electricheatersareattachedtoeachgun, permittingthemtofunctionattemperaturesaslowas70deg.A removable, streamlined bomb

rackisprovidedoneachouterwingpanelforbombsupto500lb.,depthcharges, chemical, orauxiliaryfueltanks. Fusing of bombs is

electrically controlled fromcockpit,andbombscanbedroppedin a dive, level flight, or 30deg.climb. Sway braces are integralwithracks.

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GENERALSpan.....................................................37.03ft.Length(overall)...................................32ft.23/8in.Length(tailwheelonground).............30ft.8in.Height(tailwheelonground,

propellerverticalattop)..............12ft.6in.

WINGSAirfoilsection......................................NAAlowdragChordatroot........................................8ft.8in.Chordneartop(215in.from

fuselagecenterline).....................4ft.2in.Incidence(variable).............................Approx1deg.Sweepback. ..........................................3deg.35min.32secDihedral(at25%line)........................5deg.

STABILIZERSpan.....................................................13ft.21/8in.Maximumchord...................................2ft.6in.Incidence..............................................2deg.Dihedral...............................................(none)

FUSELAGEWidth(max.)........................................2ft.11in.Height(max.).......................................6ft37/16in.Length(withoutenginemount,

frontofheatexchangertotipoftail).....................................24ft.2in.

Length(withenginemount,tipofpropellershafttotipoftail).........30ft.9in.

AREASWings(lessailerons)...........................220.55sq.ft.Ailerons(total).....................................12.64sq.ft.Flaps(total)..........................................32.6sq.ft.Stabilizer(includingelevators)............27.85sq.ft.Elevators(includingtabs)....................13.05sq.ft.Elevatortrimtabs(total)......................2.00sq.ft.Verticalstabilizer.................................8.83sq.ft.Rudder(includingtabs).......................10.25sq.ft.Ruddertrimtabs(total).........................82sq.ft.

LANDINGGEARType.....................................................Hydraulic,retracting,

conventional,3wheelTread....................................................11ft.10in.Shockstruts .........................................AiroilcombinationWheels(Magnesiumalloyconstruction)

diameter.......................................27in.Tires(allweathertread).......................27in.Brakes..................................................Disk,hydraulicOleotravel. ..........................................8in.

TAILGEARType.....................................................Hydraul.,retract.,steerableShockstrut. ..........................................AiroilcombinationWheeldia.............................................12.5x4.5in.Tire(channeltread)..............................12.5x4.5in.Oleotravel. ..........................................7.50in.

ENGINEType.....................................................PackardbuiltRollsRoyceDesignation..........................................V16503Numberofcylinders............................12Gearratio.............................................21:44Coolant(70%waterand30%ethylene

glycolbyvolume)........................TypeD:SpecANE2

PROPELLERType.....................................................HamiltonStandard

HydromaticDiameter..............................................11ft.2in.Blades..................................................4,paddletypePitchsetting(hydrauliccontrolled)

Low..............................................24deg.High.............................................65deg.

SETTINGS&RANGEOFMOVEMENTOFCONTROLSURFACES

Stabilizer,fixed....................................2deg.Verticalstabilizer,fixedoffset

(fromfuselagecenterline)............1deg.

In.atDeg. MaxChord

Ailerons,wing.Uptravel(fromneutral)...............10 2.2

.........................................12 2.7

.........................................15 3.3Downtravel(fromneutral)..........10 2.2

.........................................12 2.7

.........................................15 3.3Elevators

Uptravel......................................30 8.63Downtravel.................................20 5.9

RudderRight............................................30 13.5Left..............................................30 13.5

Flaps....................................................50 20.5TrimtabsElevator

Up................................................10Down. ..........................................25

Rudder Right............................................10

Left..............................................10Aileron

Up................................................10Down. ..........................................10

Toleranceoncontrolsurfacesmovements approx.deg.

Dimensions and Leading Particulars

ONTINUED ADVANCES inengineering of the Mustangreflect improvements of

specific interest to the aircraftdesigner. Among these arebetterments in such installations aslanding gear fairing door, landinglight, gun and ammunition chutes,andthearmoredfirewall.

C

Fairing DoorThis hydraulically operated

inboard unit, covering the wheelwell,ishingedclosetotheairplanecenterline, andis designed to opento permit extension of the landinggear and then close after the gearand then close after the gear isextended. Eliminating a sourceofdrag,thedoorhasanareainexcessof 4 sq. ft. and thus addsconsiderablytotheliftingareaofthewing an important factor astakeoffwithheavybombloadundereachwing.Also, gravel and dirt from the

propeller blast are prevented fromentering the wheel wellcompartment and coming intocontactwith landinggearanddoorlock mechanisms, hydraulic lines,coolant pipes, and wiring circuitsimmediately accessible through thedooropening.

Landing LightNAA engineers found that the

leading edge was not the mostdesirable location for the landinglight, since the Mustang wing iscomparativelythinnerbecauseofitslaminar flowdesign. Curvatureofthelensalsocausedrefraction.By relocating the light in the

wheel well, lighting efficiency hasbeenimprovedbyabout40percent.Initsnewlocation,theinstallation

is readily accessible for quickreplacement, the light beam is notobstructed,andintersectionwiththepropellerarcisbelowthepilot'slineofvision.Control switch for the light is

mountedonthepilot'sswitchpanel.A springloaded safety switch,actuatedbythesupportarmforthelight,isconnectedinserieswiththe

control switch, and breaks thecircuitwhenthelandinggearstrutfairingpushesthelightupwardintothewheelwell.

Armament AccessGunandammunitionbaydoors

on the P51 embody good designfor quick and easy access toarmamentcompartments.Accesstothebaysineitherwing

is obtained by loosening two

fasteners which safety two coverlatchhandles,swingingthehandlesup,andopeningtheforwardcover.Rearcoverofthegunbaymaythenbeliftedouttofullyexposethethree.50cal.guns.Accesstotheammunitionbayis

providedbyraisingahandleinthegun bay to free one side of theammunition bay cover, which thenmaybeliftedout.Thisgivesaccesstothethreeammunitionbelts.The two removable doors are

JL McClellan: P51 draft Copyright 2005 p 24 of 32

Aerodynamic, Weight, and Servicing RefinementsFeatured in North American P-51

Providing additional lifting area ofover 44 sq. ft., P-51 landing gearinboard fairing door, seen at top innormal closed position when gear isextended, opens (as shown atright) to permit wheel to beretracted, then closes again, In-stallation protects gearmechanisms and plumbing fromgravel and dirt, and presents nointerference to flow to airscoop.Also visible is landing lightrelocated from wing. When gear isretracted, fairing on strut contactsroller under lamp housing andpushes unit into recess.

JL McClellan: P51 draft Copyright 2005 p 25 of 32

First steps for quick access to gun and ammunition bays ofMustang is loosening of two fasteners in the cover latch handles.This permits raising of cover over forward part of gun bay.

With hinged cover raised, rear cover of gun bay may then beremoved by pushing forward, Access to ammunition bay on right ishad by raising short lever to free one side of ammunition bay cover.

With ammunition bay cover unlocked, it is pulled backward and lifted out with aid ofhandhold at right. Note that rear cover of gun bay has been removed at the left.

In replacement procedure, rear cover of gun bay or ammunition bay cover may be installed first.

replaced first, and the hinged gunbay door is closed last. Thisinterlocking door arrangementgreatly speeds work of armamentmen when servicing the guns andreloadingbetweencombatmissions.

Shell-Ejection ChutesPhenolic fiber shellejection

chutes recently designed for theMustang have been found superiorto stainless steel for this purpose,afterexhaustivefiringtests.Impactof the .50cal. brassshell

cases against the ejection chuteedges caused warping of thestainless steel, which would notreturn to itsoriginal formedshape.Also, peening action of the emptycasesagainstrivetsontheinsideofthestrikingplatedamagedthemsoseverelythatttheendofsome4,230roundstheplatefelloff.Thefiberchuteactedasacushion

for the shell cases, andafter firingmore than 10,000 rounds,examination showed the newinstallationtobesuperior.Also, phenolic fiber chutes are

quicker to manufacturerequiringonly about 25 min. compared tomorethan1hr.forthestainlesssteelchutes.

FirewallDesigned to save weight and

material,thefirewallontheP51isfabricated of armor plate and doesdouble duty by serving as astructuralmemberattachingtoupperandlowerlongerons,andprovidingprotectionforthepilotfromfrontalenemygunfire.Theinstallationthuseliminates the need for the usualstainless steel firewall withadditionalbackingofarmorplate.

JL McClellan: P51 draft Copyright 2005 p 26 of 32

Here (left) is seen stainless steel shellejection chute after some thousands ofrounds had been fired. Note result ofpeening action of shell cases. Shown atright, at conclusion of same number ofrounds, is new phenolic fiber chute withsimilar material for striking plate. It exhibitssuperior characteristics.

Armor-plate firewall on P-51 takes place ofconventional stainless steel installationand serves structural purpose in additionto affording gunfire protection.

ONE HUNDRED ANDTWENTY DAYS from thebeginning of preliminary design todelivery of the first plane completely designed for quantityproduction. This was the recordestablished by North AmericanAviationonitsP51Mustang.

Although large numbers of thetypehave nowbeen inaction forsome time, and a dive bomberversion has already gone intoproduction, design andconstructiondetailshavejustbeenreleased.The race against time began in

Apr. 1940, when the BritishPurchasing Commission openednegotiations with North Americanfor production of a fighter planeincorporating all the combatknowledge gained to that time bythe RAF, the AAF, and thecompany. The commission

JL McClellan: P51 draft Copyright 2005 p 27 of 32

NorthAmericanP51HasNovelDesignFeatures

.

Laminar flow wing, structural aluminum engine mount, smallcross-sectional fuselage are all incorporated in fighter,prototype of which was test flown within 120-day schedule

Prototype of the North American P51 Mustangfighter (left)onwhichdesignandconstructiondetailshavejustbeenreleased,madeitsfirsttestflightwithin

120 days of beginning of preliminary design. Divebomber version (right) is being built on sameproductionlinesasfighter.

Despite design-production schedule allowingbut120days,NorthAmericanengineersdecidedonlaminar flowwing,neverbeforeused.Finalfoil,however,wasquitedifferentfromthatdevelopedbyNACA,towhichNAAengineers give full creditforresearchwork. Notflushriveting by which aluminum alloy skin is attached. Well for fullyretractablemainlandinggearisatlowerright.

P-51's full cantilever, stressed skin wing consists of two panelsbolted together at center. Main and rear spars are flanged aluminumalloy; remainder of wing structure consists of extruded stringers andpressedribs.Althoughdesignedinremarkablyshorttime,planewassetup for quantity production methods. Here fuselage is lowered intopositionformatingwithwingduringproduction.

originally asked that NorthAmerican build a fighter typealready in production, but J.L.Atwood, NAA vicepresident, solditsmembersonthenewcraft,whichdidn'tyetexist.Tocompletethedesign,forwhich

more than 2,800 original drawingswere made, Chief DesignEngineerEdgar Schmued divided the workamong specialized engineeringgroups, who worked with skeletonspecifications made up fromsketchesandverbalinstructions.Despite the time limit, North

Americandecidedtousea laminarflow wing, even though this typehad never been used before.Although the laminar flow sectiondesignedandwindtunneltestedbythe NACA to which NAAengineers give full credit forresearchwasusedasabasis,theP51 wing section, as finallyperfected,differedconsiderablyOf full cantilever, stressed skin

construction, the wing consists oftwo panels bolted together at thecenter plane of the fuselage. Bothmain and rear spars are flangedaluminum alloy sheet construction,withflapandaileronhingesupportsmounted on the rear spar.Remainder of the wing structureconsists of extruded stringers andpressed ribs, with skin coveringofaluminum alloy. Fuel tanks arelocated between the spars on bothsides of the centerline, with a

structuraldoorintheundersideofeachwingsectiontofacilitatetheirinstallationandremoval.Next to the laminar flowwont,

NorthAmericanengineersconsidertheoutstandingfactorintheP51'saerodynamic efficiency to be thefuselage, which has what isbelieved to be the smallest crosssectional area ever put behind an

Allisonengine.Inkeepingwithsizeandshapeof

thefuselage,anewideawastriedintheformofasemispherical,moldedplasticwindshield.Windtunneltestsdelighted the engineers, but flighttestprovedtoughonpilots, for thecurved glass distorted groundappearance and made landingsextremely difficult. A conventional

JL McClellan: P51 draft Copyright 2005 p 28 of 32

Mustang purportedly presents smallest crosssectional fuselageareaeverdesignedbehindAllisonengine.Sidepanel(left)offuselagemainsectionisactuallyabeam,thestructurecomprisingtwolongeronsformingthebeamcapsandskinformingthewebs,reinforcedbyvertical

frames. Behind cockpit, longerons extend into semimonocoquestructurereinforced by vertical frames, Inproduction, panels gointojigs (right) when turnover structure (inverted V unit at center) isinstalled.

Structural aluminum engine mount, replacing conventional welded steel type, wasdesigned into P51to facilitate installation and removal as well as to save weight, simplifyconstruction,andprovideeasyaccessforfieldmaintenance.Enginecowlingconsistsofforwardringandsevendetachablepanelstoprovidemaximumaccessibilityformaintenance.

windshield, placed at a 40deg.angletohorizontallineofflight,wastheninstalled.Thecockpititselfisunderaflush

typecanopywithanupperandrightside section hinged to open forpilot's entrance and exit. Slidingwindows are built into both sidesections, and the entire enclosuremay be jettisoned as a unit foremergencyegressofthepilot.Thefuselageisdividedintothree

sections: engine, main, and tail, allofwhich are attachedbybolts. Atthe cockpit, or main section, thefuselageconstructionconsistsoftwobeams.Thestructurecomprisesfourlongerons, twooneachsideof thecockpitformingthebeamcapsandthe skin forming the webs,reinforcedbyverticalframes.Aftofthe cockpit, the longerons extendinto semimonocoque structurereinforcedbyverticalframes.The ethylene glycol engine

coolant andoil radiators are set inthebottomofthefuselage,aftofthecockpit,enclosedinaduetwithanadjustableairscoop.Oninitialflighttests the engine overheated, andwind tunnel tests shewed that thedisturbedboundariesofairunderthewingandfuselagepreventedacleanflow of air through the scoop.Lowering the entrance lip of thescoopapproximately1in.fromthefuselage bottom cured the troublewithoutaffectingperformance.Empennage is a full cantilever

structure with semimonocoque finand stabilizer. The full cantilever,metalcovered horizontal stabilizerconsists of two spars, aluminumalloy ribs, and extruded stringers,and it is built as one unit withdetachable tips. Elevators are offabric covered aluminum allowconstruction, consisting of a frontspar, short intercostal rear spar,flangedribs,andmetalleadingandtrailingedgesections.Bothelevators which are interchangeable arestatically balanced and fitted withtrim tabs controllable from thecockpit.Vertical stabilizer is a full

cantilever, semimonocoquestructurecomprisedofforwardandrearspar,flangedribs,andextrudedstringers.Power plane it one Allison V

1710F3R liquid cooled engineequipped with ramming type airintake for altitude operation,

swinging a threeblade Curtisselectricconstantspeedpropellerof10 ft. 9 in. dia. The closefittingcowling around the power plantconsists of a forward ring andseven detachable panels formaximumaccessibility.Tospeedengineinstallationand

removalandalsotoprovidecaseofaccess,lightweight,andsimplicityof construction, and originalstructural aluminum mount wasdesigned to replace theconventionalweldedsteel.To eliminate the chance of

enginefailurebecauseoflonglinesfromtheoiltanktotheenginethetank was located just above theengine ahead of the firewall. Oilpressure at any attitude of flightwasassured through aswivelunitarranged to be under oil at alltimes,sotheliquidwouldfeedinaverticalclimbeventhoughthetankwasonlyonequarterfull.In the ordinal design, the

carburetor air intake was set overtheengine, with theopeningwellbackfromthepropeller.Onflighttests, however, the enginecut outundercertainhighspeedconditionsand instruments indicated apeculiarpulsationeffect in the airscoop. Further flight and windtunneltestsindicatedarepetitionofthe old boundarylayerair troubleand revealed that an air beatfrom the propeller was beingtransmitted through the intake tothe carburetor. To overcome thefirst condition, the scoop wasraised slightly. the second troublewaseliminatedby lengthening thescoop to a point just behind thepropellerwhereairwaspickedupbefore the pulsation had been setup.All three units of the

hydraulicallyoperatedlandinggearrarefullyretractable,withthemainunits being fitted with hydraulicbrakes.Wheelwellsarecoveredbyhydraulically operated fairing toeliminatedragwhenthegearisindown position. The tail wheel,steerablewithintherangeofrudderpedaltravelcanswivel360deg.The tail wheel also employs a

simplesurgingorificereplacingthenormalmeteringpintoregulatetheamount of oil flowing from onestrut cylinder to the other underlanding impact. Its developmentwas brought about during design,

when it was found the originallyscheduled unit could not bedelivered on time by themanufacturer. NAA engineersdesigned and built the type nowused,thenturnedthedrawingsoverto the original producer. (Also seepages 147, 183, and 255 of Feb.Aviation.)

Specifications and Performance Data

Span.............................37ft.5/16in.Length........................32ft.27/8in.Height.................................8ft.8in.Totalwingarea.............233.19sq.ft.Weight.................................7,724lb.Highspeed(approx) 400mph.Engine.....................AllisonV1710F3RVtypeethyleneglycolcooled

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JL McClellan: P51 draft Copyright 2005 p 30 of 32

Exploded view of North American P-51 Mustang engine mount,shows how built-up box beam side member (A) is used inconjunction with extrusions, such as at (B) and (C). Carburetor airinlet (D) is casting. Engine is attached to mount at four points; thatis, at Lord mounts (E) which are also shown on small sketch ofcomplete unit and Lord shear rubber bushings (F). Mount isattached to armor plate firewall by four nickel steel bolts at points(G) and is so designed that engine can be removed as a unit.Lifting lugs (H) can be used either to lift engine and mount, orhoisting complete airplane

North American P-51 Mustang hasbeencalledoneofthemostaerodynamically advanced aircraft in service today. In this cutaway illustration, redrawn from Flight, many of interestingstructural details are revealed. Reading counterclockwise, theyinclude:RearshutterofairscoopA,containing oil andengineradiatorsBandC,respectively.WarmairistakentocockpitthroughpipeD.FrontshutterofscoopisatE,airenteringatF. G is 70gal. selfsealing gasoline tank, and three

ammunitioncontainersareatHformachinegunsI.AnotherammunitioncontainerisatJformachinegunK.CarburetorairintakeisatL,airbeingtakentodowndraftcarburetorthroughductM,justinfrontof10gal.oiltankN.BulletproofglassOispartofstandardarmor.OverturnstructureisatP.Ship'sbattery is depicted at Q, radio units are seen at R, and theoxygencontainersofthecraftareatS.

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