THE JUNKERS (GERMAN) TOURING MONOPLANE : Three-quarter front view. This machine, which is built of metal throughout, is oi the " wireless " type, having no external lift bracing. The wings are built up of tubes and covered with corrugated aluminium sheet, as is also the fuselage. On September 13 last this machine is said to have reached an altitude of 6,750 metres (about 22,200 ft.)*with eight people on board. The engine is a 185 h.p. BJM.W. ("Bavarian Motor Works).

The pilot sits in front of the cabin, immediately behind the engine

THE JUNKERS TOURING MONOPLANE : Three-quarter rear view

O O O O O O O O

O

O

O

O

T h e J u n k e r s Touring Mono­plane : The cabin and the eight passengers with w h i c h t h e machine reached

22,200 ft.

O O O O O O O

O

o o o o o o o 0 o o c o o o o

•434

JANUARY I I , 1923

METAL AEROPLANESResume of Professor Junkers' Paper read before R.Ae.Soc.

CONSIDERABLE disappointment was lelt at the Royal Aero-nautical Society on January 4, when it was announced that,unfortunately, Professor Hugo Junkers would not be able toread his paper personally as, owing to illness, he was preventedfrom travelling to this country. He had, however, sent asspecial messenger with the manuscript and lantern slides ofhis paper, Herr Ingenieur Mierzinsky, who is consultingengineer at the Dessau works of Professor Junkers, andconfidential secretary to the well-known German constructor.The paper had been translated into English by Mr. W. J. Stern,of the Air Ministry Laboratory, South Kensington, who alsoread the paper. Considering that Mr. Stern had only receivedthe original German manuscript the day before the lecture,he acquitted himself very creditably indeed of a very difficulttask, especially in view of the fact that, as he pointed out,he was not an expert on metal construction. ProfessorLeonard Bairstow was in the chair, and after a brief statementof the reasons which had prevented Professor Junkers frombeing present called on Mr. Stern to read his paper.

In his introductory remarks, Mr. Stern stated that hethought the best plan would be for him to confine himselfmainly to the matter relating to the illustrations, as the paperwould be published in full in the Aeronautical Journal. Hethought, however, that the introductory remarks of ProfessorJunkers would be of interest, and consequently read them.Professor Junkers in his lecture attributed to the invitationto him to read a paper before the Royal Aeronautical Societythe deeper meaning of a token of amiable disposition asbetween nation and nation, and saw in it an effort to renewthe ties of genuine humanity and to extinguish the sadtraces of a devastating war by hoisting the flag of peacefulcompetition.

In describing the method by which he had arrived athis all-metal aeroplane, Professor Junkers pointed outthe importance of close co-operation between research andproduction, and between science and commerce. Beforeproceeding to the construction of all-metal machines,Professor Junkers had a number of experiments carried outin the wind tunnels at Aachen and Dessau, among the subjectsbeing wing sections of varying camber, but of the samethickness, different angles of trail, thin sections and thicksections. A number of slides were shown, from which theresult was arrived at that a certain thick section was, atsmall angles, equal to a thin section in efficiency, and at largeangles equal to a deeply cambered thin section, forming, soto speak, an envelope curve around the curves representingthe other two types of section.

Slides were shown illustrating the first Junkers all-metalmachine, the J.I, which was built in six months. In thismachine, Mr. Stern said, iron tubes were used, and also ironcovering. Presumably, this was merely a slip on the partof the translator, and should have been steel tube. Slides werealso shown of loading tests of a number of tubes, from whichit was found that short thick-walled Duralumin tubes reachedthe theoretical figure, while thin-walled long tubes did not,until Professor Junkers had some tubes made in whichlongitudinal corrugations reduced the tendency to secondaryflexure and a figure approaching the theoretical was reached.

Mr. Stern also quoted from the paper references to theearly conviction of Professor Junkers that for efficiency alldetrimental resistance should be suppressed, and slidesmade from patent specifications showed some rather unusualdesigns in which the passengers were accommodated insidethe wings. A number of suggested designs were shown,mostly very large machines, as Professor Junkers was of theopinion that only in large sizes could the combination of all-metal construction and the suppression of ordinary fuselagesbe successfully attained.

A large number of slides were then shown, illustratingvarious Junkers machines, most of which were, however,familiar to all who follow aviation at all closely, as they hadbeen published in various journals from time to time duringthe last three or four years. Among them was a picture ofthe Junkers armoured biplane, a specimen of which was atone time on view at the Agricultural Hall, Islington. Othersillustrated the " Annelise " type, which has become knownchiefly owing to the activities of John Larsen in America.Similar Junkers monoplanes fitted with floats were alsoshown.

The Chairman (Professor Bairstow), before opening thediscussion, said that the paper and illustrations had been ofvery great interest, and had certainly shown several things

which were unconventional from our point of view. He wasreferring chiefly to the aerodynamic features, about which heknew more than he did about constructional principles.He then declared the paper open for discussion, and hoped thatmany would take part in it.

Mr. F. Handley Page expressed his thanks to ProfessorJunkers for having agreed to come ov$r here and give usthe benefit of his experience. He (Mr. Handley Page) causedconsiderable amusement by stating that the first Junkersmachine which he saw was one which had crashed in landing,the fuselage having broken in a rather unfortunate place.The name Junkers had been painted on its sides, and thebreak had occurred just behind the k, so that when he walkedaround the machine to attempt to find out what it was heread the letters " Junk." A closer inspection, however,revealed the fact that the machine had, in the main, stoodup to the crash fairly well. As regards the paper therewere one or two things in it which had surprised him. Thus,he was somewhat astonished to find the curve representingthe thick aerofoil forming an envelope to the curves of thinsections and deeply cambered sections. This did not appearto tally with our results, and he would like to know somethingmore about the manner in which the result had been arrivedat, where the tests were carried out, what was the size of themodel, and at what air speed was the test run.

As regards the statement made in the paper that theDuralumin covering did not deteriorate, Mr. Handley Pagestated that some time ago he had an opportunity of examiningsome Junkers machines in America, and there the coveringwas certainly showing signs of corrosion. Turning to thestatement that the Junkers machines in Colombia werefitted with Duralumin floats, he rather thought that thepictures indicated that the floats were wood, and he had anidea that, as a matter of fact, it was found that the Duraluminfloats gave trouble owing to water leaking in between joints,and so forth. He concluded by thanking Professor Junkersfor his paper.

Major F. M. Green said he was very interested to learnabout the use Professor Junkers had made of Duralumin, andpointed out that in this country we had less faith in thatmaterial, and that, as a matter of fact, our constructors wereforbidden by the Air Ministry to use Duralumin for anyparts likely to be highly stressed. As most of the parts of an

' aeroplane were highly stressed, this meant that to all intentsand purposes we were not using Duralumin in the con-struction, preferring to use instead high-tensile steel. Hewas sorry that so few data had been given in the paper, or, atany rate, in that portion of it which Mr. Stern had read,and hoped that more data would be found in the completepaper. With regard to the statement made that the climbof the Junkers J.13, with six passengers, was a record per-formance, he would like to know what engine was fitted, as hedid not think the performance was anything out of theordinary.

Mr. Stern, in replying, stated that with regard to Mr.Handley Page's questions, the tests on aerofoils were carriedout by Prandtl at Gottingen, and that, no doubt, the figurescould be verified. As regards the question of the use of woodfloats on the Junkers machines in Colombia, he did notthink it was specifically stated in the paper that these wereof Duralumin. He himself had thought that they were.He had no doubt that Professor Junkers would be pleased tofurnish any additional data desired. The engine fitted in theJ.13 was a B.M.W. over-dimensioned super-compressedengine of 185 h.p.

A hearty vote of thanks was then passed, both to ProfessorJunkers and to Mr. Stern and Herr Ingenieur Mierzinsky.

As the paper as read on January 4 was considerablyabbreviated, we would advise readers desiring to read thecomplete paper, as well as any discussion in writing thereof,to obtain a copy of the Aeronautical Journal for February, inwhich the paper will be published in full. •

In connection with Professor Junkers' paper, it is ofinterest to note that permission has been obtained for one ofthe latest types of Junkers machines to fly to Croydon, inorder to give an opportunity for detailed inspection of theconstruction. The machine is expected to arrive in the courseof the next few days, and persons wishing to visit Croydonfor the purpose of inspecting the machine should applyto the Secretary, Royal Aeronautical Society, 7, AlbemarleStreet, Piccadilly, London, W. 1.

JANUARY I I , 1923

LONDON TERMINAL AERODROMEMonday Evening, January 8, 1923

PASSENGERS have fallen-ofl again now that the holidaysare definitely over, and this week's total has fallen to quite alow level in comparison with recent weeks. This is particularlytnarked on the Manchester-London-Amsterdam route, andalso on the London-Cologne air line, while even the HandleyPage service to Paris has not been as well patronised as isusual on this line.

The weather has interfered, to some extent, with theregularity of the services, and on Tuesday the only serviceto be run was the Daimler line from Manchester to London—all the continental services being cancelled owing to fog atLympne. In spite of the progress made in civil aviation,we are not yet past the stage when a small patch of fogover one portion of the route shuts down the servicescompletely—although the rest of the route may be normalfrom a weather point of view.

On Thursday, Maj.-Gen. Brancker, Brig.-Gen. Festing andCol. Edwards arrived at the aerodrome, and went for a flightin the all-metal German Dornier machine. The GermanAmbassador was also in evidence, and several other notabilities.As usual with General Brancker, the flight was arranged for9 a.m. and the first Press photographer arrived on the sceneabout 11 o'clock, just in time to get pictures of the departureof the machine on its way back to Germany.

Rumours that Failed to MaterialiseTHERE were persistent rumours during the week that we

were to have a visit from another German all-metal machine—in this case one of Herr Junker's monoplanes, which, it wasstated, was to fly to London in connection with Herr Junker'slecture to the Royal Aeronautical Society. At the time ofwriting, however, this machine has not materialised.

I understand that Messrs. Vickers are fitting one of theVickers " Vulcans " of the Instone Air Line with a Napier" Lion " engine, in place of the present engine, in order togive the machine a bit more speed, and to enable it to get off,when fully loaded, with a shorter run. In the meantime,the Instone service between London and Cologne is beingrun entirely with De Havilland stock. In view of the factthat the aerodromes at Brussels are in such a bad state, a stopis now made at Ostend for the convenience of passengers forBelgium. This makes the journey to Cologne slightlylonger, but the extra mileage is insufficient to interfere to anygreat extent with the time-table.

The Big French Airway CombineTHE amalgamation of the French firms is now complete, and

the entire French service is being run under the control ofthe C.M.A. air lines, although the personnel of the GrandsExpress is still giving a helping hand. I am told that theFranco-Roumanian Co. are also in the amalgamation, which,if so, makes the French combine probably the biggest andmost powerful in existence.

The strong winds and gales are continuing to play havocwith the time-tables, making some journeys remarkablyrapid, and flights in the opposite direction long-drawn-out.On Friday, Mr. Shaw, who was flying the Marconi Co.'sexperimental " Avro," which is fitted with a 90 h.p. R.A.F.engine, was up in a gale of wind, and, while attempting tofly over Purley, head-to-wind, he was unable to make anyheadway for half an hour. In fact, at the end of 30 mins., heestimated that he had been blown back a distance of about25 yards. As the wind was increasing, he decided to alight,and, diving down, he succeeded in gaining enough headwayto turn and alight on the aerodrome with his engine full on.

Further additions have been made to the departure andarrival platform by pushing out a couple of concrete pathwaysinto the sea of mud, and making two square platforms at thehead of these paths for passengers to alight on. If we getmuch more rain, and all machines make for these platforms,it may be necessary to dig out the machines after they areloaded, for the mud around them is already like a quagmire.

Pilots, by the way, flying between London and Manchester,are now reporting—from their point-view aloft—furthervery evident extensions of the flooded areas.

* * * m :',." :'-,;-. .:-Air Mail Stamps and Correspondence ^

THE Editor of FLIGHT invites correspondents throughoutthe world to send him letters (addressed to 36, Great QueenStreet, Kingsway, London) by their national or local airmails. These will have special and personal acknowledgmentin the Editorial columns of FLIGHT, and help to encouragethe more general use of the air for mail carrying. TheEditor would also greatly appreciate any items of interest ornews relating to air mail services and air stamps.

Night Flying TestsIT is probable that next month the Air Ministry will

carry out further night-flying experiments on the London-Paris route, this time under regular service conditions. Weunderstand a D.H. 9 will be used for these trials.American World's Speed Record Homologated

THE speed record made by General Mitchell, of theAmerican Air Service, on October 18 last year, when heattained a speed of 224 • 58 m.p.h. has now been homologatedby the International Aeronautical Federation.

PUBLICATIONS RECEIVEDWar and Peace. No. 4. " Phalanx " Verlag, Schillstr. 15,

Berlin.Malaises des Aviateurs. By Dr. Perrin de Brichambaut

and P. Behague. Librairie Gauthier-Villars, 55, Quai desGrands-Augustins, Paris. Price 1 fr.

Report on the Economic Conditions in Cuba, September, 1922.By G. Haggard, O.B.E. H.M. Stationery Office, Kingsway,W.C. 2. Price 9d. net. By post lOd.

Report on Economic and Financial Conditions in the BritishWest Indies, June 30, 1922. By A. W. H. Hall. H.M.Stationery Office, Kingsway, W.C. 2. Price Is. net. Bypost Is. l^d.

Report on the Financial and Economic Conditions of theArgentine Republic, September, 1922. By H. O. Chalkley.H.M. Stationery Office, Kingsway, W.C. 2. Price Is. 6d. net.By post Is. 7id.

m m m mAERONAUTICAL PATENT SPECIFICATIONS

Abbreviations : cyl. = cylinder; I.C. = internal combustion ; m. •• motorThe numbers in brackets are tbose under vshicb the Specifications will

be printed and abridged, etc.APPLIED FOR IN 1921Published January 11, 1923

24,065. ENGLISH ELECTRIC CO., LTD., and W. O. MANNING. Seaplanes.(190,211.)

24,220. M. GOLEIN. Aeroplanes. (190,220.)25,009. D. J. MOONEY. Metal aeroplane wings. (190,254.)

Published January 18, 1923 . "17,601. J. C. BARKER. Supporting-planes. (190,506.) / "24,807. W. HAUPT. Flying-machines. (169,966.)25,046. B. B. KEITH. Toy Airships. (190,530.)27,278. H. O. SHORT. Aeroplanes. (190,576.)27,521. D. J. MOONEY, E. E. BROWN and D. H. EMBY. Metal framework to r

aircraft. (190,579.)APPLIED FOR IN 1922Published January 18, 1923

4,160. R. LEPARMENTffiR. Variable-pitch screw propellers. (190,663.)

NOTICE TO ADVERTISERSAll Advertisement Copy and Blocks must be

delivered at the Offices of " FLIGHT," 36, GreatQueen Street, Kingsway, W.C. 2, not later than12 o'clock on Saturday in each week for the followingweek's~~issue.

FLIGHTThe Aircraft Engineer and Airships

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26

JANUARY 18, 1923

THE JUNKERS ALL-METAL MONOPLANE180 H.P. B.M.W. Low-Compression Engine ...

IN our issue of last week we published a brief resumd of thepaper on " Metal Aeroplanes " read before the Royal Aero-nautical Society by Mr. Stern on behalf of Professor Junkers,who was prevented by illness from being present. At theconclusion of the lecture it was announced that permissionhad been obtained for one of the Junkers machines to flyto this country in order to give members of the R.Ae. Soc. anopportunity of examining Professor Junkers' method ofmetal construction.

The machine arrived on Thursday of last week (January 11),and by permission of the Junkers representatives (and greatlyassisted by Mr. Stern, of the Air Ministry Laboratory, SouthKensington, who acted as interpreter), our representativeswere allowed to examine the machine in detail for the purpose

purposes. We have always understood that the experiencewith these machines was not a very happy one, but we wereinformed by the Junkers representatives that the originalmakers had nothing to do with the machines after they leftthe Dessau works, and that alterations were made to them,so that the J unkers firm feel that they should not be blamedfor anything that went wrong. They stated that of themachines used in Germany, under the supervision of theoriginal makers, not a single one gave any trouble.

Fundamentally the Junkers monoplane is a cantileverwing machine, with the wing placed low on the fuselage(" tiefdecker " is the German name) in the place usuallyoccupied by the lower plane of a biplane. The reasons forthis arrangement were outlined in Professor Junkers' paper,

THE JUNKERS MONOPLANE : Three-quarter front view.

of compiling the following notes, and in order to obtain theaccompanying sketches and photographs.

The particular machine which visited Croydon was onetaken from the regular service. So far as could be ascertainedit was built in 1921, but had not been in constant use all thetime since, having, apparently, spent some of the time as oneof many " confiscated " by the Inter-Allied Commission.Certainly the metal showed no signs whatever of corrosionexternally, but as the length of time during which the machinehas been in actual service is not known, this fact does not reallyenable one to form an opinion. We were informed by thepilot that one of these machines which had been in servicein Sweden for over a year had been left out in the open habitu-ally, had been in the sea (it was a seaplane), and generally hadbeen very far from receiving careful treatment, yet the metalnowhere appeared to have suffered from corrosion, in spiteof the fact that it was built of Duralumin throughout. Theexact treatment of the metal is not known, but it appearsthat some form of aluminium paint is coated on all the partsbefore they are assembled, and the whole structure thengiven one or two coats of varnish.

In type the Junkers monoplane which visited Croydon isnot new, a considerable number having been in use inGermany, while others were purchased for America by Mr.John Larsen, and were used in that country for various

the wing roots, fuselage, etc., forming one solid unit to whichall the heavy loads and the wings themselves are attached.Aerodynamically this arrangement has been found to "i>eslightly inferior to the more usual arrangement in which thewing is placed above or on the top of the fuselage, butProfessor Junkers considers that the slight loss is more thanmade up for by the rigid structure resulting from the lowposition.

During the War a few all-metal Junkers machines werecaptured, and one or two were, at one time, on view at theexhibition of enemy aircraft at the Agricultural Hall,Islington. The armoured biplane was briefly described andillustrated in FLIGHT of November 28, 1918. The monoplane,the Junkers D.I, was described and illustrated in our issuesof April 1 and April 8, 1920, while a commercial machine,very similar to the present specimen, was illustrated in FLIGHTof October 30, 1919. The latter machine was the one whichreached an altitude of 6,750 metres with eight people onboard, as mentioned in Professor Junkers' lecture. The engineused on that occasion was one of the 185 h.p. B.M.W. over-dimensioned, high-compression engines, which maintaintheir power up to a height of about 15,000 ft. The machineat present under review is fitted with one of the low-compres-sion B.M.W. engines, as the high-compression type was notpermitted by the Inter-Allied Commission.

1

THE JUNKERS MONOPLANE : Three-quarter rear view.35

JANUARY 18, 1923

THE JUNKERS MONOPLANE : Side view.

The Cantilever WingAlthough the Junkers monoplane will not be a novelty to

readers of FLIGHT, it is thought that a few notes dealing withthe construction may not be without interest, as it waspossible, on our visit to Croydon, to ascertain certain con-structional features which were not published in previousarticles. The cantilever wings are characterised by the same

Thus the whole wing structure is perfectly triangulated,except for the bays in the plane of the covering. These arenot braced by strips, the corrugated covering being evidentlyrelied upon for this purpose as well as for covering.

In the wing roots, built as integral parts of the fuselageand extending about three feet out from the body, the diagonalmembers are of the same tubular form as the spars themselves,

THE JUNKERS MONOPLANE On the left, view of the engine housing and undercarriage. On the righta view of the tail.

construction as that employed in the D.I fighter, i.e., a numberof tubular Duralumin spars tied together by corrugated stripstriangulating the structure. The upper and lower spars arestaggered in relation to one another, i.e., the tube near theupper surface is placed over the space between two consecu-tive lower tubes. The diagonal ties then run from lower toupper tubes and vice versa, sloping outwards at the same time.

whereas in the wing end pieces the bracing is by corrugatedstrips. These strips are spread out towards their «nds, wherethey are flattened out to lie against the curve of the tubularspars, to which they are riveted. In this connection it is ofinterest to mention that the manner of " holding-up " whenriveting is done by a special tool designed for this purpose,and we believe, patented by Junkers. At the lecture a slide

THE JUNKERS MONOPLANE : Rear view. This illustration gives a good idea of the large span of themachine.

36

JANUARY 18, 1923

was shown of the manner in which this tool works. The toolis essentially a long rod, carrying an excentric. This rod ispushed into the tube until the excentric is opposite the holeinto which the rivet is being put. The rivet is inserted and therod turned until the excentric bears on the end of the rivet.One man then taps the rivet head while another slowly turnsthe rod so as to keep the excentric always in contact with therivet. In this manner the riveting proceeds fairly rapidly,

The manner of attaching the wing end pieces to the wingroots has already been described both in our article on thearmoured biplane and also in that dealing with the D.Isingle-seater fighter. It is in the form of pipe unions in eachtubular spar, steel liners being inserted in the end of the tubesto strengthen the joint. A special spanner is used for tighten-ing up the joints, and it is stated that the operation of detach-ing or attaching a wing is very quickly carried out.

THE Junkers Monoplane : Some sketches of constructional details. 1 shows the inspection door in the side ofthe fuselage which gives access to the tail skid. The large tube runs to the elevator crank. The trimming tankis just in front of the door, inside the body. 2, details of the fuselage construction. No longerons are used, thecorrugations of the covering taking the place of separate longitudinal members. 3 shows the aileron tube-and-crank control which takes the place of cables. 4 is a general view of the wing construction. The small inset isa diagram of the wing section, showing approximate location of spars and bracing strips. 5, the union joint in thefront spar. 6, a typical joint between wing root spars and the spars of the end pieces. In the wing roots the bracingmembers are tubular, whereas in the end pieces the spars only are tubular, the bracing members being made

from strip metal, crinkled as indicated in the two sections.

and it is stated that with a little practice the workmen canmake perfect riveted joints.

In the actual construction of the wings the internal struc-ture is built up on one set of jigs while the sheet covering isbent to shape on another. The framework is then slippedinto the covering, and the latter riveted to the tubular sparson top and bottom, using, presumably, the same tool for" holding-up." We were informed that in the monoplanewhich visited Croydon something like 85,000 rivets are used.

Owing to the fact that there is a change in the directionof the spars at the point of the junction of end pieces to wingroots, the unions have a slight cup shape, forming in fact asort of ball-and-socket joint. The gap between wing root andwing is covered afterwards by a Duralumin strip folded overthe trailing edge and secured on the leading edge by wingnuts. This strip has internally hooks formed of sheet alu-minium which slide over the spars as the strip is^being pulledinto place. The wing section appears to be bi-convex, with

37

JANUARY 18, 1923

a distinct " wash-out " or decrease in the angle of incidencetowards the tip.

The Fuselage.The fuselage of the Junkers is mainly of interest, apart

from its somewhat unusual shape, on account of the all-metalconstruction, in which no longitudinal members are used, thecorrugated Duralumin covering serving the purpose of long-erons. FundamentaHy«the, fuselage is built up of formersmainly constructed of channel sections, to which the sheet

appears to us doubtful whether the risk of having a petrolpipe running down the whole length of the fuselage, and liableto break in case of a crash, is an arrangement that should beadvocated. ._, - . .-

ControlsThe control column itself is of orthodox type, but an un-

usual feature is that both ailerons and elevators are controlledvia large diameter tubes, working both in tension and com-pression. Those to the ailerons run to crank levers, as shown

H H S H H

The Junkers Monoplane :This photograph, a slideof which was shown atProfessor J u n k e r s 'lecture, illustrates thewing construction. Notehow bracing strips aremerely riveted to sides

of tube.

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covering is riveted. One of the accompanying sketchesshows the details of the construction. The fuselage has fiatsides, but curved top and deeply curved bottom. In frontthe top covering sweeps down to the cockpits for pilot andengineer, which are of the open type and placed side by side,immediately aft of the engine.

The cabin itself has accommodation for four passengers.A " sofa " seat runs right across the rear wall of the cabin,while the two front seats are separate and are so hinged thatthey can be tilted forward in order to facilitate entrance toor exit from the cabin. Behind the rear seat is a compartmentfor luggage. There is a door in each side, but apparently thaton the starboard side is intended chiefly as an emergencyexit, as there are no steps on the wing root on that side.Windows in both sides admit light, and as there is no wingabove the cabin to obscure the light, the cabin appears tobe quite well lighted. The view downward is obstructed to aconsiderable extent by the large-chord wing placed low on thefuselage.

The EngineThe 180 h.p. low-compression B.M.W. engine is placed on

metal bearers in the nose of the fuselage. In front of it is acar-type radiator, with shutters for varying the cooling. Theengine is covered by a bonnet which hinges along its rear end,so that when it is raised and leaning back against the " hump ' 'of the fuselage the engine is quite exposed. A number ofcatches secure the cowl in place, so that the possibility of itblowing back during flight should be very remote. The petroltanks are placed one in each wing root. Owing to the internalbracing the shape of the tanks is rather complicated. A smallgravity tank is placed in the pilot's cockpit. I t is of interestto note that no water tank is fitted, the amount carried in thewater jackets and radiator being sufficient. The capacity ofthe two main petrol tanks is about 320 litres (70 gallons),which is sufficient for approximately 8 hours' flight at 1,200r.p.m., corresponding to a cruising speed of about 140 km.(87 miles) per hour. The two tanks are connected by a tubeof very small diameter, so that, although petrol will flow fromone tank to the other, it does so very slowly, and there is nodanger of one tank becoming empty while the other is full,which might upset the lateral stability.

The arrangement for trimming is unusual. In place of atrimming tail plane, such as is found on the majority of Britishaeroplanes, a small petrol tank, with a capacity of just undertwo gallons, is placed in the fuselage near the tail skid.Normally this tank is empty, but when the machine is flownwithout passengers, or with only one or two passengers, petrolis pumped, by a hand pump in the pilot's cockpit, into thetrimming tank until the machine is in the right trim. Althoughsimpler, mechanically, than a tail plane trimming gear, it

in one of our sketches, while that to the elevator runs firstto a crank on a lay shaft some distance back in the fuselage,another running from there to the elevator crank. Thelatter*tube can be seen in the sketch showing the inspectiondoors near the tail skid. An interesting feature of the aileroncontrol is that the single aileron crank is placed at the extremeinner end of the aileron, so that the torsion on the aileronleading edge must be considerable. The corrugated coveringhowever, makes the ailerons extremely stiff, and when theaileron was held in place and a lift applied at the outer endit was scarcely possible for a man to twist it to any perceptibleextent. The rudder controls are by foot bar and cables inthe ordinary way.

UndercarriageThe undercarriage of the Junkers monoplane is of the Vee

type, but is remarkable for the fact that both front and rearstruts are sprung. The shock absorbers are in the form ofsteel springs, enclosed in streamline casings. One wheel can.rise without the other if the movement is a vertical one, butit appears that if one wheel is knocked back by a bump, theopposite one has to move forward. A lateral Vee carries atits apex the hinges for the axles, which move separately in avertical plane, but together in a horizontal plane. The lateralVee serves to locate the entire chassis in a lateral sense, butis hinged to the fuselage to allow a slight forward and aftmovement. As the machine did not fly on the day of ourvisit to Croydon, owing to the fog, we were not able to seehow the undercarriage behaves in taxying and landing, butwe were informed that it is entirely satisfactory. A tail skidsprung and swivelled in the usual way protects the tail planesagainst contact with the groun.d

But few particulars of the Junkers monoplane are available,but following are a few which are thought to be approximatelycorrect:—Span,. 17 • 1 metres (56 ft. 1 in.) ; wing area, approxi-mately 350 sq. ft. ; weight of machine empty, but with coolingwater, 1,155 kg. (2,540 1b.) ; useful load, 645 kg. (1,200 lb.) ;maximum permissible total weight, 1,800 kg. (3,635 lb.) ;power loading (180 h.p.) 20-2 lbs./h.p. ; wing loading 10'7lb./sq. ft. ; maximum speed, about 160 km. (100 miles) perhour ; cruising speed, 140 km. (87 m.p.h.) ; landing speed,80 km. (50 m.p.h.) ; duration, 8 hours at cruising speed,corresponding to a range of about 700 miles. .

Herr Patze, one of the directors of the Junkers air lines,visited this country in order to try to arrange with theDaimler and Instone lines for an extension of their servicesinto Germany, Junkers machines picking up the passengersand goods at Amsterdam and Cologne. Owing to the Frenchoccupation of the Ruhr the arrangements have had to bepostponed, but it is to be hoped that later on the suggestedconnection will come into being.

38 - -g;^7r/:-.

FLIGHT, APRIL 4, 1930

JUNKERS F13

THE Junkers F.13, though in the luxury class as a

private owner's machine, has already found oneowner in this country, as the Hon. F. E. Guest,the chairman of N.F.S., maintains one for hisown use.

Junkers machines are really too well knownto need much description and, structurally, the F.13 is justthe same as the Junkers Junior, which has already beendescribed. The same all-metal cantilever principles areadhered to and also all the other Junkers details which havegone so far in building up this form of machine. The F.13is a cabin machine with ample accommodation for fourpassengers, and in front of the cabin is the pilot's cock-pit, with two seats side bv side and with dual controlsfitted.

A similar version to this machine, but with the cabinstripped, is used for freight, and it was in a machine of thistype which Herr Kohl, Baron von Hiinefeld and MajorFitzmaurice flew from Dublin to Labrador in April,1928.

The pilot's cockpit is not enclosed, but so carefully has thedesign of the nose of the machine been carried out that there isno draught at all, and one has the added advantage of being

able to dispense with windows, which might possiblybecome fogged in bad weather.

The passengers' cockpit is extremely comfortable, andthis, added to the inherent advantages of the low wing type ofmachine, make the F. 13 certainly one of the most comfortablemachines we have ever flown in.

Large luggage accommodation is arranged behind the cabinin a compartment which has its own door on the side of thefuselage.

The engines fitted are either the Junkers 280-310 h.p. L5water-cooled or the Jupiter 425 h.p. air-cooled radial. Theformer is an exceptionally quiet running engine, and whentravelling in this machine so fitted there is no difficultyexperienced in conversation between the passengers.

Trost Bros., of Victoria Street, London, are the agents forthese machines over here, and they keep one or two at Croydonfor taxi work, where they have been doing quite a lot of workduring the last year.

The general equipment of the Junkers is very thoroughindeed, and many extra instruments are fitted as standard.There is a centralised fire-extinguisher system which hasnozzles directed to vital parts of the machines, so that a firecan be extinguished immediately.

379 G 2