APRIL 1ST, 1943 FLIGHT 337 ENGINE PROGRESS 1918-43 REFLECTIONS UPON 25 YEARS OF DEVELOPMENT : IMMENSE STRIDES DURING LIFE OF R.A.F.

• By G. GEOFFREY SMITH, M.B.E. lKING back over the 25 years' existence of the Royal becoming outmoded, but there were several notable Air Force reveals the immense strides that have been examples even in 1918, including the Clerget manufactured E made in the design and performance of aircraft power by Gwynnes and the BR 2 made by Humber, Ltd., and units. From every aspect, be it quality, volumetric effi- developed by W. O. Bentley, now designer for Lagonda ciency, power output, specific weight per horse-power and, Motors. Also considerable numbers of the Gnome above all, reliability, progress has been so marked that Monosoupape engine still existed. As the name implies, to compare them with the simple types that were employed this engine had only one valve per cylinder ; this was the a quarter of a century ago is most impressive. exhaust valve, located in the head. Air was admitted via Such has been the technical progress in aircraft engines the hollow stationary crankshaft and mixed with iuel over the past quarter of a century that it has only been injected from a nozzle into the crankcase. Ports cast in possible in a brief space the skirt of the cylinder pro- to compare • their general jecting into the crankcase features. From simple two- TO attempt to review in brief space the broad subject of were uncovered by the valve engines largely de- aircraft engine development over 25 years is ambitious, and at the bottom of the , veloped from racing cat- in a way unsatisfactory, as so much must remain un- so admitting mixture to the practice and weighing 3 lb. chronicled. In this summary of the trend of design the writer, who was a captain in the R.A.F. engaged upon cylinder. A favourite engine per h.p., to-day much larger engines in the last war, touches upon the salient changes of the time was the fiii?Sunbeam Arab (two exhaust and one inlet valve per cylinder, simple in design, with a direct-drive per cylinder), and the 180 h.p. .eight-cylinder 90 (leg. airscrew. It took only about 1,380 man-hours,to produce, Hispano Suiza (two valves per cylinder), known as the according to records of that time, and cost about ^900. A Wolseley Viper, produced by Wolseleys, of Birmingham. modern supercharged engine with 12, 18 or 24 cylinders, In common use was the R.A.F. V-type eight-cylinder air- far and away more complex in its equipment, costs some cooled engine on the same general lines as the Renault. At £3,000 and occupies fully 3,000 man-hours in production that period, too, Napiers were manufacturing the Arab, and by the most modern machine tools and factory technique. gradually transferring their energies to the 450 h.p. twelve- After a wonderful career, rotary radial engines were cylinder three-row (broad arrow) Lion. This engine,

j

ARMSTRONG SIDDELEY HIGH SPOTS : Top row (left), Seven-cylinder Lynx, 150 h.p, in 1922, 235 h.p. in 1929. (Centre) Fourteen-cylinder Jaguar, 300 h.p. in 1922, 500 h.p. in 1929- (Right) The 340 h.p. Cheetah X fitted to the Oxfords and Alisons. At the bottom is a production store of 240 h.p. Pumas in 1918. •338 FLIGHT APRIL IST, 1943

ENCINE PROGRESS, 1918-1943 designed by A. J. Rowledge, was rapidly coming into favour although some firms were able considerably to improve as the biggest unit then available for aircraft, and it re- upon this figure. As in the present war, car manufacturers mained in service for many years ; a high-speed type Lion were pressed into service to produce aircraft power units. in 1926 developed 500 h.p. at 2,250 r.p.m. and scaled In addition to the companies already named, Arrol-John- 950 lb. dry. Three years' research prdduced the super- ston, Daimler, Crossley, Swift and Lanchester were so charged Schneider engine which gave 1,320 b.h.p. for employed. 1,170 1b. weight. In the summer of 1918, the nine-cylinder radial A.B.C. Twenty-five years ago the average time expended in air-cooled engine of 340 h.p., designed by Granville Brad- producing an engine of simple specification, such as shaw, was adopted for large-scale production in many to-day would suit training aircraft only, was 2,500 hours, factories, but the arrival of peace cancelled the plan, although a number of prototypes were manufactured. Supercharging was in its infancy in the Great War, but engines were fitted experimentally with engine-driven or exhaust-turbo blowers, and certain designs embodied multi- stage blowers even in those early days. Following the peace of 1918, engine development was inevitably slowed down. It is a sad commentary that it needs a war to stimulate intensive development and pro- gress. A distinct fillip to aircraft engine development occurred when the Bristol Co. acquired the Cosmos Engineering Company and concentrated attention upon various types of air-cooled poppet valve radials, among them being the. Lucifer and Jupiter. In later years the Bristol Co. perfected the single patented by Burt and MacCullum, which led to the introduction of the now familiar Perseus, Hercules and Taurus, the two latter being twin-row types. The poppet valve Bristol Mercury was selected in 1936 for mass production under the shadow factory expansion scheme. Rolls-Royce Vee Twelves The famous Rolls-Royce firm never ceased research and development of aircraft engines subsequent to their entry A 375 H.P. RC^LS-ROYCE EAGLE VIII : This type powered into the aircraft arena in the great war, with a vertical single, and twin-engined bombers and flying boats of 1918. six-cylinder- Hawk. In the interim they have produced a

TWELVES AND A TWENTY-FOUR

(Top left) The unsupercharged 12-cylinder 480 h.p. Kestrel of 1927. It was also available as a moderately supercharged engine er with full supercha/ging. (Top right) The 2,300 h.p. Racing engine for the Schneider contest in 1931. (Bottom left) The 1,960 h.p. 24-cvlinder Vulture X engine, and (Bottom right) The Merlin LXI with two-speed two-stage supercharger fitted in the Spitfire IX height-cover fighter. APRIL IST, 1943 FLIGHT 339

remarkable range of twelve- cylinder 60 deg. V types, notably the Falcon, Eagle, Kestrel, Con- BRISTOL FASHION: Top Row dor and Buzzard, their efforts (Left) The Mark II Jupiter ol culminating in the twelve-cylin- 400 h.p. which was developed der Merlin in 1934, which engine with a standardised power egg mounting in 1922. It developed in its varying forms has won 595 h.p. in 1932. (Centre) The fame the world over. Of 27 litres 840 h.p. Mercury which has been capacity, the engine has pro- produced in thousands in our gressed through many stages of shadow factories. (Right) The improvement, mainly connected 1,000 h.p. Pegasus, Bristol's h'gh- with the supercharger, and is est powered poppet valve eng-'ne. now able to attain the strato- (Bottom) The 14 cyl. two-row sphere, the latest Mark 61 hav- sleeve valved Hercules of i,425h.p. ing a two-stage two-speed super- in its complete power egg. charger to provide higher power at high altitudes. Armstrong Siddeleys produced several first-rate single- that aircraft design as a whole was governed by the slow row radials, the Lynx and Genet Major, also an advanced rate of progress with airscrews, When, in 1928, Dr. Hele type of double-row radial known as the Jaguar. The Shaw and T. E. Beecham introduced their hydraulic- Cheetah seven-cylinder radial is a standardised type to-day. governor to provide variable pitch for the blades, the In the years prior to 1930, epicyclic reduction gearing prospect was opened for further big advances both in air- for airscrew drive was applied to air-cooled engines—liquid- craft and engine design. At that time ability to take oil cooled engines already had spur gearing. This general a heavy aircraft was a governing factor, and a successful adoption of geared-down airscrews enabled an increase in variable-pitch airscrew to provide greater thrust by enabling crankshaft revolutions and a.more suitable speed for the engine r.p.m. to be maintained was a crying need. Not- airscrew, which at that time almost exclusively had two withstanding that fact, the feared complication of a v.p. blades of fixed pitch. Further major changes in engine airscrew checked adoption, and it took the inventors years design followed the introduction of variable-pitch airscrews. before their design was finally accepted. About that time Aircraft engine design is very closely associated with air- a number of other airscrew designs appeared with the blade screw progress. For years engine development was retarded pitch governed by hydraulic, electrical or mechanical means. by the form of airscrew available. Indeed, it can be said To-day three- or four-bladed airscrews have displaced the fixed-pitch two-blade type, and variable-pitch, constant- speed, full-feathering and even reversible-pitch airscrews are now standardised R.A.F. equipment. Contra-rotating airscrews with variable-pitch blades is the latest develop- ment in anticipation of the larger power units coming into service. Technical Progress The lean years in aircraft production were those follow- ing the Great War until about 1930, when outstanding achievements in the air began to attract universal atten- tion. Despite meagre financial allocations, technical pro- gress during these lean years was never allowed by the Air Staff to lapse, and one or two firms were busily en gaged upon the development of engines in collaboration with the Royal Aircraft Establishment. Unobtrusively, painstaking research and experiment 011 the part of aero- nautical and metallurgical specialists made possible larger diameter cylinders fitted with four valves of noncorrodible material, higher piston speeds and higher compression ratios. Ethylene-glycol cooling enabled smaller radiators of compact form. For air-cooled radial engines greatly improved cowling was devised. Low pressure super- A Rolls-Royce Merlin standardised power egg as fitted on the chargers had become the vogue the great benefits of pres Avro Lancaster. sure charging of the cylinders having, by this time, been 34O FLIGHT APRIL IST, 1943

ENGINE PROGRESS, 1918-194 3

(Top left) The broad arrow substantiated. By this con- Napier Lion of 450 h.p. in 1920. centrated attention British de- It had a reduction gear for the signers and research engineers airscrew. succeeded in keeping the com- paratively small engine in- (Top right) The supercharged racing type Lion produced for dustry in the van of progress. the of 1929. In 1928 Rolls-Royce tested an It developed 1,320 b.h.p. exhaust-driven turbo super- charger with two stages for (Below) The H type 24-cylinder the compressor on a 12-cylinder Dagger was the precursor of the Condor of 650 h.p., but finally . 700 b.h.p. at 3,500 adopted a geared centrifugal r.p.m. blower driven from the crank- shaft. The Napier Lion, Bristol and Liberty engines were A spell of activity with diesel type engines, both air- also tested with exhaust-driven superchargers many years and liquid-cooled, brought forth no revolutionary engine, ago. A notable design of this era was the Napier but at one time the altitude record was held by a Westland 16-cylinder X type Cub engine. biplane fitted with a Bristol Phoenix diesel engine. The Royal Air Force pilots or ex-pilots had over a period set advent of petrol of 87 and later 100 octane ratings offset up many world's records, Capt. John Alcock and Lt. Whit- many of the advantages that a C.I. oil engine offered, par- ten Brown making the first direct crossing of the Atlantic ticularly for Service flying. Actually fuel improvements by air in June, 1919, on a Vickers-Vimy biplane with two and supercharger progress permitting higher boost and Rolls-Royce Eagle engines. In 1933 a Fairey monoplane cylinder working pressure, constitute the major advances with a Napier Lion engine flew from Cranwell to Walvis of the period. These developments set problems for the Bay, a distance of 5,341 miles, in J52hrs. 25 min., in the metallurgical industry and plug manufacturers which were hands of Sqn. Ldr, O. R, Gayford and Fit. Lt. G. E. successfully surmounted by research and experiment. Nicholetts. Altitude records were achieved and broken Names prominent in the development of aircraft engines again as engine development proceeded, until Fit. Lt. over the years include E. W. Hives and A. G. Elliott (Rolls- M. J. Adam attained 53,937ft. in 1937 on a Bristol Pegasus- Royce) ; Sir Roy H. Fedden and L. F. Butler (Bristol); engined monoplane. In 1938 long-distance records were Frank B. Halford ( and Napier), and H. R. achieved by a trio of Vickers-Wellesley monoplanes with Ricardo, the noted research engineer. special Bristol Pegasus XXII engines, which flew from In the development of special fuels of high octane rating Ismailia to Darwin non-stop, a distance of 7,162 miles. Grp. Capt. F. R. Banks played a leading part durijj That remarkable record of endurance has never been term with the Ethyl Corporation. broken. Less than ten years ago the production of aircraft engines was mainly centred around tt Rolls-Royce, Bristol and Napier. Trainer type eilfJUR! were manufactured by Armstrong Siddeley, de Havilland and

1922 28 1930 32 34 36 38 I94O YEAR (Above) Showing the steady increase in piston speed, 1922 POTENTIAL H.R AT SEA LEVEL to 1940. The dotted line illustrates the effect of dynamic loading for any given stroke, showing how engines have developed in the capacity of their moving parts, bearing surfaces, lubrication, etc. (Right) Showing increase with time in the theoretical full throttle potential power at sea level of standardised engines. The curve is plotted on the basis of horse power per square 1922 24 1930 32 840 inch of piston area. YtAR APRIL 1ST, 1943 FLIGHT 341

ENGINE PROGRESS, 1918-1943 \ Cirrus. When in 1934 war clouds began to be discernible, the Government was urged in these columns to expand facilities for engine production, and in 1935 Flight addressed an appeal to Lord Weir urging the need for immediate expansion of engine production facilities, and particularly stressed claims for a Scottish factory. In March, 1936, the Government announced that two com- panies, i.e., Austin and Rootes, had agreed to give the Government the benefit of their production experience, and in October, 1936, the shadow factory scheme was outlined and extended to six engine factories in the Mid- lands. The Bristol Mercury was the engine selected. This was a timely move which ensured the quantity of engine equipment which was to be so badly needed when the crisis came, as well as works personnel skilled in the prac- tice of engine production. Inverted 4-cylinder in-line de Havilland Gipsy Major of All-round progress in design has enabled the power 130 h.p. which has powered so many trainers of the R.A.F. developed for a specific capacity to be more than doubled 1,260 hours are allowed between complete overhauls. during the lifetime of the R.A.F. To-day a normal-sized .unit develops 1,000 h.p., and many engines exist which brought forward the remarkable S6B seaplane develop nearer 2,000 h.p. Progress proceeds apace on still —the basis of the redoubtable R.A.F. Spitfire. Applied larger sizes in multi-bank radials of eighteen or more cylin- to it was the Rolls-Royce " R " engine which developed ders, and H-, V- and X-types with twenty-four cylinders. 2,300 h.p. at 3,200 r.p.m. for a weight of 1,630 lb. = n ozs. Looking ahead, the 3,500 to 5,000 h.p. engine units with per h.p.—the best result ever achieved. It had the same contra-rotating airscrews will be needed for the larger air- and stroke, 6in. x 6Jin. as the Buzzard engine from craft of the future. As an important competitor to the which it was developed. reciprocating engine the combustion gas turbine enters the The racing version was too light and frail for regular aircraft arena in an advanced stage of development. Service operation but for the specific purpose of the contest it proved ideal and succeeded in annexing the Trophy out- The Increase of Eiigine Power right as well as beating world's speed records at 408.8 Thus from six-cylinder in-line engines, seven-cylinder m.p.h. in the hands of R.A.F. pilots in I93r. It is ques- radials and eight-cylinder V type unsupercharged units, tionable if the late Lady Houston was ever sufficiently the R.A.F. equipment has progressed to fully supercharged credited for the immense technical progress her beneficence 9-, 14- and 18-cylinder air-cooled radials and twelve or brought al>out in aircraft and engine design. Officialdom twenty-four cylinder liquid-cooled engines of either V- or had decided against support for this event, and by stepping H-type. Moreover, apart from the great increase in unit into the breach with financial aid, Lady Houston enabled size and power, four engines have become the rule on concentration upon a major task which in a comparatively to-day's heavy bombers, in place of the single- or twin- brief period was the means of advancing the science and engined installations fitted to bombers in the last war, a progress of aeronautical design by several years. jump of something like 5,800 h.p. ; that is from 700 h.p. In 1934 the London-Melbourne race for the MacArthur to 6,500 h.p. A modern single-engined fighter actually Trophy brought forward, among other notable aircraft and has ten times the power that was available in the fighters engines, the de Havilland Comet with two Gipsy engines of.the year 1918. which won the event comfortably. The present Mosquito In performance, operational reliability and the length with two Merlins is the direct descendant of the racing of period between routine overhauls, the modern engine is machine, having many design features in common. far and away superior to earlier types despite its higher Modern achievement will be more familiar to readers, the stressing and reduced weight per h.p. Engines were never names of British aircraft and engines having become house- so complete as they are to-day. A manufacturer supplies hold words. a self-contained unit equipped with all auxiliary drives and In view of the record of quality and achievement of connections, arranged in an interchangeable mounting with British engines in every sphere, one may look forward with efficient cowling ready for easy installation on the aircraft. confidence to the future. Many important design innova- ^v Ms often been said with truth that racing improves tions are being actively developed to-day and must remain *»*- L "••*. Unquestionably aircraft and engine design have subjects for future discussion. British technicians may be ^"•s L jrom competitive events. To quote two in- relied upon to maintain the proud position already attained stant.' Pr' y to prove the point. The Schneider Cup Trophy in the aeronautical world.

Securities, Ltd., had been appointed technical adviser to Mr. FHHTION Layton-Bennett. AST week several announcements were made which caused While all this was going on, there came the announcement L some consternation in the aviation world. The first was by Sir Archibald Sinclair that three directors had resigned from that Mr. K. A. Layton-Bennett had been appointed controller the board of British Overseas Airways Corporation. They were of Short Brothers, following upon the recent retirement of Mr. Give Pearson (chairman), Mr. I. C. Geddes (deputy- Mr. Oswald Short from the chairmanship, and the appointment chairman), and Mr. \V. L. Runciman (director-general). The of Sir Frederick Heaton to that post. trouble arose through the refusal of the Air Ministry to allocate Then came the somewhat startling announcement that '' an to the Corporation all the' trunk routes except those carrying order had been made under Regulation 78 of the Defence exclusively R.A.F. loads. The Corporation directors considered (General) Regulations, 1939, whereby all shares of every class this essential, but the Air Ministry did not consider that the in Short Brothers (Rochester and Bedford), Ltd., were on necessary flexibility in working with the newly formed Air March 23, 1943, transferred to and vested in nominees of the Transport Command could be achieved in that way. As we go Ministry of Aircraft Production." to press it is reported that employees of the Corporation have On April 25th it was announced that Mr. Layton-Bennett requested that Sir John Reith should be recalled to his old post- had been appointed controller of General Aircraft, Ltd. In of chairman. Previously, Sir Archibald had announced that making the M.A.P. decision known to employees of General Sir Harold Hewitt was to be temporary chairman, and had Aircraft, Ltd., Mr. E. C. Gordon England, managing director, appointed Mr. Simon Marks and Mr. John Marchbank to the announced that Mr. R. C. Rootes, deputy-chairman of Rootes board. 342 FLIGHT APRIL IST, 1943

which the Iris III had three Rolls-Royce Condor water- RAF. AIRCRAFT, 1918-1943 cooled engines, the Iris IV three Siddeley Leopard radial air-cooled, and the Iris V three Rolls-Royce Buzzard liquid- cooled. stage. Since then it has, of course, come into extensive . The connection of Short Brothers with flying-boat work use both as a fighter and as a fighter-bomber. The Bristol goes back to early days. During the period here reviewed Beaufighter, with two 1,400 h.p. Hercules engines, is of that firm produced an impressive series, of which three more recent design, and is credited with a nominal maxi- went into fairly large-scale production: The Singapore II mum speed of 330 m.p.h. at 14,000ft. Quite recently refer- had four Rolls-Royce Kestrel engines in two tandem pairs; ence has been made to the De Havilland Mosquito as a the Rangoon three Bristol Jupiters ; and, finally, the Sun- fighter, but no details may be divulged. derland monoplane flying boat of modern times, with Army co-operation is a subject much to the fore nowa- four Bristol Pegasus engines. days, although its character has changed considerably from Saunders-Roe contributed the Saro London and Ler- that visualised in peacetime, which dictated policy before wick, the former a biplane and the latter a monoplane. the war. Mention has already been made of the fact that From Supermarines came the Scapa and the Stranraer, there were many variations of the Hawker Hart day both biplanes. bomber. These included the Audax biplane with Kestrel Although the Fleet Air Arm has now reverted to com- engine. This machine was used for many years on Army plete Admiralty control, and its aircraft are thus not, co-operation work. In more recent times a variant having strictly speaking, any part of the Royal Air Force, the the Napier Dagger 24-cylinder air-cooled engine was pro- types produced during the early 'thirties were R.A.F., duced and used fairly extensively. and should receive a brief mention. The Westland firm has for many years been closely asso- The Fairey Seal was a three-seater version of the Gordon /' ciated with Army co-operation aircraft, the types ranging day bomber, the crew of three being deemed necessary in from the old Wapiti biplane with Jupiter engine, through naval reconnaissance aircraft. The engine was an Arm- V the Wallace biplane with Pegasus, to the Lysander mono- strong Siddeley Panther radial air-cooled. The Seal had plane of the present day. its Blackburn counterpart in the Shark, a T.S.R. (Torpedo- The link between the Royal Air Force and the Navy Spotter-Reconnaissance) type with Armstrong Siddcl.y is formed by Coastal Command, which Mr. Churchill put Tiger engine. The Shark remained in service for many years. under the operational control of the Admiralty some years Then followed the Fairey Swordfish, again a T.S.R. type, ago. That Command has become one of our most impor- with Bristol Pegasus engine. The Swordfish is still in use. tant, and from using flying boats in the earlier days has Chronologically, the Blackburn Skua followed next. It added landplanes for much of its work. was a two-seater naval dive-bomber with Bristol Perseus Many different types are in use by Coastal Command, sleeve-valve engine, and was the first monoplane produced including some American. The British type designed for naval use. It was designed to operate from carriers. specifically for torpedo-bomber-reconnaissance work is the A development of it was the Roc two-seater fleet fighter, Bristol Beaufort, a twin-engine monoplane with two equipped with a Boulton Paul multi-gun turret. The 1,000 h.p. Bristol Taurus sleeve-valve engines. Other types engine was the Perseus. have, however, been converted for torpedo carrying, in- Reverting to the Fairey Company,, the Albacore is a cluding the Handley-Page Hampden and the Vickers Wel- more modern type ^han the Swordfish, in that it has a lington, which were originally bombers. A still more recent cabin for its crew of two or thrte. It is a biplane, and is adaptation to torpedo-carrying is the Beaufighter men- a T.S.R. type. The engine is a Bristol Taurus 14-cylinder tioned above. sleeve-valve of about goo b.p. The Fairey Fulmar is a Four firms have contributed to the development of the monoplane two-seater fleet fighter developed from the flying boat—Blackburn, Short, Saro and Supermarine. Fairey P.4/34. It has the Rolls-Royce Merlin X engine of The Blackburn contribution comprised the Iris series, of 1,145 h.p. CORRESPONDENCE The Editor does not hold himself responsible for the. views expressed by correspondents. The names and addresses of the writers, not necessarily for publication, must in all cases accompany letters. BOMBER ESCORT provement in directional stability, and offers, in part, a solution to this take-off difficulty. Again, a very obvious advantage Snags in the Glider Fuel Tank Idea is apparent in the case of marine aircraft when the dihcd- ' AJ. G. GREEN'S letter in your issue of March 18th is lifts the tailplane (and outboard rudders, if any) M of much interest, but the plan proposed seems rather take-off spray. impracticable when examined in any detail. The chief disadvantage would appear to be th Not a great deal would be gained either, and there are many complication in the elevator interconnection. g disadvantages in the scheme. The cost of such a glider would connection of the elevators is an essential precaution against also be considerable, no matter how simply it was constructed. a particularly dangerous mode of tail-flutter in which differ- As a bomoer escort the tug and glider would be subjected ential movement x>t the elevators is coupled with torsion of to the usual A.A. fire, and having a flying petrol tank just the fuselage. Thus the usual light-alloy stiff tube connection behind one is hardly conducive to good moral, to say the least. must be replaced by some type of universal joint. Difficulties in formation flying would also arise»which, in them- I should not imagine that there is any - case against the selves, would be sufficient to condemn the idea. dihedralled tailplane from the production point of view. It might be useful for ferrying purposes and special long- However, the decision as to whether it is worth while must range work at sea, but that is about all. " Vic." lie with each individual designer. G. SIM.

TAILPLANE DIHEDRAL It Improves Directional Stability NOW READY N reply to " Interested's" letter in your Correspondence AIRCRAFT IDENTIFICATION I columns (Flight. March 18th), I should like to state my views concerning the recent tendency towards the dihedralled A/reprint of a highly effective and successful tailplane. series of articles from FLIGHT delineating and The higher-powered motors, now in common "use, with their describing Service types and their characteristics. consequent large torque, make "swing" .during take-off a 3/6 (or 3 9 post free) matter of increasing importance. The dihedralled tailpla'ne, with Flight Publishing Co. Ltd., Dorset House, Stamford Street, London, S.£' its increased "lateral area" at the tail, gives an all-rcund im-