86 FLIGHT JANUARY 24TH, 1946

T H E D . H . K O R N E T

the tail control surfaces were ineffective on take-off speedsunder 80 m,p.h. While there was no inherent tendencyto swing on take-off or even a likelihood of it with thisarrangement, the possibility of the aircraft being deflectedfrom its course by an external influence, and the subse-quent difficulty in correcting, could not be overlooked.Handed engines turning " down and in " were, therefore,fitted, and, although the stabilising effect of the arrange-ment was lost, directional control on take-off and landingwas satisfactory." There was a considerable delay after the mock-up,stagewas reached on the prototype Hornet, but once approvalwas given (in August, 1943) work went ahead rapidly, andthe first flight was made in July of the following year.

During the production period the prototype was sub-jected to a weekly C. of G. check, and a log was kept oneach component weight.The estimates proved veryaccurate, and the final

weight was within 200 lb. and, unusually, on the right side!In view of the high performance expected of the Hornet,

it was apparent that a safety factor of ten would be re-quired, so while the Mosquito type of construction wasquite suitable for the fuselage, the wing called for differenttreatment.

The N.P.L. were behind the design for the wing section,which is similar to that of the Vampire, but with ratherless camber. It is understood to have proved satisfactoryup to very high diving speeds, with Mach numbers in theregion of 0.78 at altitudes and 0.72 lower down.

In a wing of reasonable depth, it was not possible toobtain the requisite strength and rigidity from all-woodconstruction, and it is in the ingenious combination ofwood and metal in the design of the Hornet wing that themain structural interest lies. Wide use is made of theRedux bonding process introduced some three years ago

FUEL TANKS

HO I RIB

WINC ATTACHMENT

The radiators and air intakewith filter are shown in posi-tion in this sectioned view of

the wing.

RADIATORS

7-INTERCCOLER

OILsC0OLANT

CONTROLLABLE EXIT FLAP

WINC ATTACHMENT JOINTS

VENEER REDUXEDT0,DURAl

VENEER REDUXEDTO DURAl.

VENEER REDUXED TODURAL EXTRUSION

REAR SPAR

fROHT SPAfl

The composition of the front and rear wing spars is clearlyshown in this drawing.

by Aero Research, Ltd., under the directionof Dr. N. A. de Bruyne.Very briefly summarised, the wing is a two-

spar structure of 45ft. span and is made in onepiece. Light-alloy extrusions are embodied in spars

of mixed construction; ribs are either of wood, alloyor a mixture of the two, and the skin is a wood sandwich

on top and metal below. In the main, wood is used in com-pression and shear, and metal in tension.

Wood and DuraluminThe lower booms of the spars are dural extrusions,

the top booms are of spruce and the webs com-pressed plywood. Details of construction are shown inthe illustrations. It will be seen that the bottom boomcomprises two duralumin right-angle extrusions to each ofwhich is bonded a wood veneer. The- two are cold-gluedand bolted to the compressed ply web, arid the joint isfinished off with a layer of Chatterton's compound as aprotection. At the top, the ply veneers of the web areseparated and the thicker section curved over at r gangles to meet the under surface of the top boom. Theremaining thinner section of the web is glued to the frontface of the boom.

Between front and rear spars, the double top skin ofthe wing is reinforced by Kpanwisi- stringers narrower thanbut similar to the spruce top boom. The skin is of glueand screw construction and is attached to the top boomsin this manner. The bottom skin, which is of alcladreinforced with dural stringers, has detachable panels to;>ive access to the tanks. These panels are a part of thestressed skin.

Various t}^pes of ribs are used and, as will be seen fromthe drawings, there are fifteen in each main plane. Thecentre fuselage pair are composed of compressed plywoodsandwiched between alloy sheet. The lower booms areduralumin extrusions of inverted " T " section, the upright

JANUARY 24TH, 1946 F L I G H T 87

limb being riveted between the alloy sheets of the web,which overlap the edge of the plywood for this purpose.The top boom is of spruce, glued and screwed like themain spar. Number six rib's are a scaled-down version ofthe number ones. Numbers two, five, seven and elevenrite are each built up from plywood sheet screwed andglued to spruce frames. Two and five carry pick-up fit-tings for the tank doors, while seven and eleven havemetal flanges.

Metal-cladThe engine ribs, numbers three and four, are alloy/ply/

alloy sandwiches rather similar to the fuselage ribs buthaving " T " section extrusions for both top and bottombooms. The top skin is glued, to the top booms after athin veneer has been Eeduxed to them. With the excep-tion of number fifteen, which is an all-metal pressing, theremaining ribs are built up with single plywood webs

j r screwed and glued to spruce booms.An example of inter-rib strengthening members in thewing for attachment of drop tanks or R.P. gear.

•> PLYWOOD

NO.I RIB

VENEER REDUXED" DURAL

^PLYWOOD

VENEERSEDUXED TO

DURAL. EXTRUSION:

\PLYWOOD

VFNEER REDUXED TODURAL PRESSING

N0I5 RIB

NO 5 RI8

Details of rib construction can be followed in conjunction with the illustration on the facing page.

To ensure a smooth surface and torsional stiffness in thewing, the leading edges are of all-metal construction. Ex-rept for their attachment by Reduxing to the top of thefront spar they are quite conventional. The attachmentand construction of the all-metal flap and aileron shroudsis similar to that of the leading edge.

Six main bolts and fittings attach the wing to the fusel-age and, like the Mosquito, the Hornet has a balsa-plysandwich fuselage made in halves split vertically. Smalldifferences are the use of a thinner balsa core to the sand-

PRINCIPAL DATA AND PERFORMANCE FIGURESEngines. R.R. Merlins 130 (R.H. port) 131 (L.H. starboard).

45ft.'."screws. D.H. Narrow, 4-blade, 12ft. diameter.

Wing span,, area,, loading

LengthHeight—tail up ... ... ' ... ...

„ tail dowr ...Tail span««. tpeed.

j . ft.44.5ft.37ft16ft. 2in.14ft. 2in.I8fr Urn.

473 m.p.h. « 12,000ft.2,900 miles.„ range

„ climb 4,000ft. >in. to 15,000fc.Operational ceiling 35,OOOft.

Type

Fighter

PhotographicReconnaissance

Condition

Short-rangeLong-range

Short-rangeLong-range

WeightIb.

16,10020,900

15,90020,200

Total fuelcapacity

gal.

358928

418928

: .

wich, which saves about one-third of balsa weight, andthe use of duralumin strengthening plates on the fuselagewalls for the attachment of equipment and the like. Onthe Mosquito, plastic plates or attachment ferrules aregenerally used, and bolt holes are necessarily wide apartto prevent splitting. By the use of Redux bonding, smallmetal plates can be substituted for the plastic ones withconsiderable advantage. On the underside of the fuselagejust aft of the rear spar is a hatch giving access to equip-ment and control cables.

The Tail

The tailplant- is of conventional two-spar all-metal con-struction, with ribs from the rubber press. By virtue ofits attachment it is adjustable for rigging, two turnbuckle-type fittings being incorporated. Later marks of Hornethave two extra ribs in the tailplane, with a correspondingincrease in span. This modification followed the adop-tion of ' ' down and in ' ' airscrew rotation and to someextent offsets the de-stabilisiiig eftect of this arrangement.The area of the horn balances was also slightly increased.

The tail fin is of all-metal construction and does not callfor any special attention. The addition of a fairly longshallow dorsal fairing up to the fin is now under considera-tion.

All elevator and 1 udder control mechanisms on theHornet are placed behind the fin and are exposed for inspec-tion when the tail cone is removed.

Both frame and covering of the main controls are metal,and in each case they are noticeably flat-sided, no doubtto obviate any tendency towards reversal at high altitudes.

88 FLIGHT JANUARY 24TH, 1945

T H E D . H . H O R N E T

On the Mark III Hornet, the aileron shroudshave been redesigned, and an independenttrimming tab is now fitted to the starboardaileron. Aerodynamically the ailerons provedvery sensitive to shrouding, and although itwas not planned at first, a little nose balancehas been provided.

The spring-tab operating unit on the aileronsemploys the torsion-bar principle, and untilthe surface is under load the tab remains sta-tionary/ The torsion bar is located spanwisebetween two ribs and is some eighteen incheslong. As the aileron is loaded, the bar windsup until a stop is reached, and fromthat point the movement of the con-trol is positive.

35

Air IntakesAn interesting departure from con-

ventional arrangement is found in theinduction air intakes. These aresituated in the wing leading edges,outboard of the engines, and are con-nected with the supercharger intakesof the down-draught type by ducts,the whole layout being rather reminis-cent of the air-cooling system forGipsy Twelve engines. In addition,a rotating valve interconnected withthe undercarriage brings an air filterinto use when the wheels are lowered,that is, whenever the aircraft is on theground. A Vokes air filter is situatedin the lower wall of each duct, andsuction from the engine superchargeropens a series of hinged metal gills inthe lower surface of the wings belowthe filter. When the main air intakeis opened on retracting the landinggear the gills drop back flush with the

.wing surface and the filter no longeroperates. The layout of the system inthe wing is shown in a drawing on aprevious page.

3O

i> 25

2O

3.

o

110

I

XVIWOOLB.

r/.7OOLB.

O IOOO 2POO 3POO 4POO 5OOORATE OF CLIMB-FT/MIN.

Variation in the rate of climb withchange of altitude. With maximuminternal fuel load, fighter or P.R.version of the Hornet are capable ofaveraging 3,500 ft./min. climb to20,000 ft. at combat rating and morethan 4,000 ft./min. in the case of the

short-range fighter version.

The Hornet cockpitis well arranged withengine instruments toport, blind flying panelahead and electrics to

starboard.

The folding wing hinge fittings arebolted to a metal " belt " composedas shown of alloy sheets let in be-tween the plywood sheets of the topskin. The top halves of the stringersand the outside skin have yet to be

replaced. See also Fig. C.

Another feature making for a clean,compact engine installation is theradiator arrangement. As in the Mos-quito, the radiators are placed in theinboard leading edges, but the super-charger intercooler radiators are addedto the main coolant and oil radiators.The order, counting from -front torear, is intercooler, main coolant,oil. The complicated plumbing issimplified as far as possible by bothinlet and outlet pipes leading directfrom the outboard side of the radiatorsto the appropriate points on the en-gines. The air outlet flap from theradiators are located on the underwing surface near the front spar likethose on the Mosquito and are auto-matically controlled through part oftheir travel.

Each main wheel is carried on asingle leg sprung by rubber blocks incompression. The retractable tail wheel

has r u b b e r compressionspringing and Ferodo frictiondisc dampers. Retractionnormally takes 7 seconds. Inthe event of hydraulic pumpfailure, a hand pump, also anemergency air system, areprovided to lower the wheels.

According to d u t i e s ,whether P.R.U. or standardfighter, up to twelve tankscan be carried, ten being in-ternal and of the self-sealia|^type. The main tankage"comprises two tanks in eachmain plane, inboard of theengines, and one fuselagetank behind and below thepilot. To these basic five canbe added another fuselagetank, four more wing tanksin pairs, outboard of each en-gine, and two drop tanks ofeither 100 or 200 gallonscapacity. •

All tanks feed to the com-mon central fuel gallery, andeither engine separately may

JANUARY 24TH, 1946 FLIGHT

T H E D . H . H O R N E T

be isolated from the fuel system. The pneumaticallyoperated balance-cock is spring-loaded for opening in theevent of pneumatic failure.

Of the two Merlin engines, the 130 has right-hand rota-tion and the 131 left, the difference being achieved simplyby the introduction of an idler gear in the reduction gearassembly. The engine bearers have "i four-point attach-ment at the bulkhead and are of a new D.H. design. Thecowling is quickly detachable,' and large over-centre catchesare used in place of the normal screw fasteners both onthese and the cannon inspection panels.

Cable operation is employed for the engine controls, and

•3,000

2.5OO

b 2.OOO

u, 15OO

UJ I.OOO

5OO

MOST ECONOMICALCRUISING SPEED

SEA LEVEL - 2O.OOOFT,/

< ^

o3OO

SEA LEVEL - H^OOOFT.

I IMAXIMUM CONTINUOUS

CRUISING POWER

4OO 5OO 6OO 7OO 8OO 9OOTOTAL FUEL CAPACITY GALLS

1.O0O

The six curves represent from top to bottom :—One and two,the most economical cruising range from sea level to 20,000ft.and at 30,000ft. respectively ; three and four (dotted), the same,but with allowance for |-hr. combat at the altitude ; five,the maximum continuous cruising range from sea level to27,000ft , and six the same with J-hr. combat allowance.Letters A, B, C and D indicate respectively the followingfuei loads :—Standard, maximum internal, maximuminternal plus 100 gall, drop tanks, maximum possible,

including 200 gall, drop tanks.

The folded Sea Hornet wing. The main locking mechanism may be seen betweenthe inboard spars and attention is drawn to the linkage between the folding jack andouter wing. Note also the two " flags " protruding above and below the wingat the front spar and indicating the withdrawal of the small mechanically operated

locking pins.

A hold back snap coupling is provided on the Sea Hornetin connection with accelerated take off. The tongue is here

seen attached to lugs on the tailwheel compression leg.

the throttle lever has a 50 per cent, increase in travel overthat of the Mosquito. This will give the finer movementrequired to meet the 100 per cent increase in, engine powerover early Merlins and will make for easier movement, over-stiff throttles being a slight fault of most Mosquitos.

The Cockpit and VisibilityVery properly the cockpit has received a great deal of

attention, and the aim of first-class view has been achieved.For long-range work a pilot must not be at all cramped forspace. On the other hand, for low weight and good per-formance, minimum dimensions are essential. The Hornetcockpit seems to be a fair compromise. Although thescreen is made in three panels, the joints are so arrangedoptically that the frame member at the joint cannot beseen from inside the cockpit, and view appears to be con-

tinuous. In fact, a thin strip, abouthalf an inch wide, is lost to view ateach joint of the front panel, but asthese strips are parallel-sided there isno increased loss due to divergent linesof vision, as is usually the case withframe members. The cockpit enclosureis a single transparent moulding whichwill slide far back down the fuselageto give access to equipment andammunition boxes located behindthe pilot's seat. A chain-and-crankmechanism is employed to open or shutthe enclosure.

Adjustment for both height and tiltis provided on the pilot's seat, andpedal-length adjustment is similar tothat of the Mosquito. No anti-" g "pedals are provided, but the normalposition is high with this purpose inmind. .

The Hornet carries four 20 mm.cannons grouped in the lower part ofthe fuselage nose, to which access isgiven by two large detachable pan'-ls.Full armour protection is provid'-d,and two 1,000 lb. bombs and fourrocket projectiles, all carried beneaththe wings, complete the Hornet's com-plement in this section.

FLIGHT JANUARY 24TH, 1946

T H E D . H . H O R N E T

Manufacture of the Sea Hornet and all associated draw-ing-office work are the job of the Heston Aircraft Com-pany. While this separation of parent and child is farfrom an ideal arrangement, good co-operation and under-standing, particularly between the two design staffs, hasenabled work to progress satisfactorily. Main units art-sent dry-screwed as required, from Hatfield to Heston,where modification and final assembly take place.

Navalising the Hornet

In addition to the folding wings, the Sea Hornet isequipped with arrester and accelerator gear, and these twocall for major modifications to the fuselage unit.

A property of the normal Hornet wing is the even dis-tribution of load throughout the frame members and skin.In direct contrast to this, the load for the folding wingmust be concentrated at the hinge point and then re-distributed through the outer and inner wing sections. Thisis achieved by increasing the number of spanwise stringers,particularly in the region of the front spar, by reinforcingthe spar webs (this is inherent strengthening in view of thejoint fittings) and by inserting sectionsof dural sheet between the plywoodsheets of the top skin near the wingjoint. This metal "be l t" is actuallyinserted between the stringers, whichare split horizontally to receive it.The sheetb are Reduxed to the wood,and the separated part of the stringersreplaced and scarf-jointed outboard ofthe alloy sheets. Bolts are then putthrough the reinforced skin in placeof screws.

The number seven ribs of theoriginal wing would lie at the foldingpoint, but are removed in favour oftwo new reinforced metal ribs, 7 and7a, which carry the joint fittings fortheir respective sections.

Two separate levers in the cockpitoperate the folding mechanism. Smalllocking pins must first be withdrawnmechanically by moving one control ;then the second brings the Lockheedhydraulic jacks into operation througha sequence valve, the main bolts beingwithdrawn first and the folding com-mencing afterwards. A small flag oneach wing shows at once if themechanical locks are withdrawn.. The

V

SCARFJOINT

PLYWOOD

(Top) In contrast to the normal wingtop skin construction and attachment,inset is a section through the reinforcedSea Hornet skin showing the splitstringer and the positioning of the

alloy sheets.

Inside the SeaHornet fuselage,two modified bulk-heads are seen,also part of thelongeron rein-f o r c e m e n t sto which (on theoutside) are boltedthe arrester hooka t t a c h m e

fittings.

wings can befolded in fiveseconds or spreadin twelve. Theycan be spreadwith a 1,000 lb.bomb in position,can be foldedseparately, and may be stopped at any position desired.

The arrester hook is attached at two points to the fuselage, and the fittings are bolted through to two heavylongerons ironically called "straights." These long curv-ing laminated wood members reach fprward to the lower

rear wing-attachment fittings, whichare of steel in place of the standardduralumin forgings. The hook attach-ment fittings are also screwed andReduxed to the fuselage. The steelhook itself is coated with Colmony towithstand the sawing of the cable.

Three fittings c o m p r i s e theaccelerator attachments which canbe used with twin, close-twin orAmerican-type single-track equipment.Two large hooks are located belowand bolted to the front-wing sparsbeside the attachment points, and thesnap coupling is attached to lugs whichare a part of a saddle-like addition tothe tail-wheel compression leg. Amodification which may be adopted onall Hornets is the provision for sling-ing, the pick-up points being on theinboard engine ribs.

it will be noticed that the externalaerial on the Hornet appears to stretchfrom tail fin to cockpit enclosure. Thisis, in fact, true, but the wire passesthrough a small hole in the enclosure,through two small pulleys inside thetop of it, and finally attaches to thearmour plate behind the pilot's head.

SPLIT SPRUCESTRINGER

The Sea Hornet with wings folded and arrester hook slung under the fuselage. The wing-folding modification has added 280 lb.to the total weight and the entire " navalising " including equipment, 550 lb.