The fighters in the Second World War

The nations went to war in 1939 with the aeroplanes they had first flown in 1936. Britain had pinned her faith in the eightgun fighter, the French and the Germans believed in the 20 mm. cannon—particularly the moteur-canon.

When the 300 m.p.h. fighter arrived many old pilots felt that the "dogfight was dead". It seemed incredible that pilots could mix in combat at such speeds and it seemed certain that head-on attacks on 250 m.p.h. bombers must be out of the question. Experience in the Spanish Civil War of 1937 suggested that the forecasters might be right. This struggle, backed on one side by the German Nazis and the Italian Fascists and on the other by the Russian Communists, was a proving ground for the men and war materials of these nations. Although a small-scale struggle, it was very bitter and the backers, who started by sending along obsolescent biplanes, ended by throwing in their latest fighters and bombers.

Fortunately, the belligerents did not draw as many correct conclusions as they might because, for one thing, distances in this campaign were short and, for another, the Russian equipment was generally much inferior to the German and Italian. There was a tiny, fat, highly manoeuvrable Russian four-gun fighter, the I-16, which with its 700 h.p. radial engine was too slow to worry the Italian Savoia bombers or the German Me 109 fighters very much. It was, however, interesting as a design because it was so like the American Gee-Bee racers, with a large radial engine, behind which were fuel and pilot, a small tapered wing housing the four machine-guns and the retractable undercarriage. Like most Russian aeroplanes of those days it was made of wood, was not very up-to-date, but was rugged and stood up well to rough handling in the air or on the ground.

The Germans did discover that their vaunted Me 109 was not all it should have been and that it suffered from wing flutter and tail buffeting—vibration of the tail caused by disturbed air from the wing hitting it. What all countries had by now realized was that high-speed fighting meant rapid sighting and the ability to deliver a hard punch in a short time. The Germans felt the best way to do this was to use the 20 mm. cannon, two fuselage machine-guns and two wing machineguns , all of rifle calibre. The cannon was included because the Me 109 was originally envisaged mainly as a bomber destroyer and the extra weight of these explosive shells was intended to damage the more massive and larger aeroplane.

Before the War started the reflector sight had been invented to replace the old external ring-and-bead or Aldis tube sight. The reflector sight was mounted inside the cockpit above the dash and all it needed was an optically-flat panel in front of it. This flat panel is a distinctive feature of the wind-screens of this period. On British fighters it was made of armoured glass capable of protecting the pilot from splinter or machinegun hits. The R.A.F. also fitted armour to the back of the pilot's seat. The weight of this armour was eschewed at first by the Luftwaffe for its fighters, but it was one of the decisive factors in the Battle of Britain because of the pilots it saved. The devastating effect of the eight-gun strikes at 1,300 rounds per minute was another key issue. The British fighters were also easier to fly and land (the Me 109 had a higher wing loading and shorter span) and were generally more manoeuvrable.

The marked difference in the noses of the British and German fighters was due to their engines. Both liquid-cooled, the Merlin was a vee-twelve with a spur-type reduction gear which brought the propeller shaft up on a level with the exhaust ports; while the German Daimler-Benz was an inverted veetwelve in which the spur gearing kept the hollow airscrew shaft down between the cylinders, where the cannon was mounted, so that the shells could pass through it. The Merlin was a marvel of compactness and was housed in a neat, tight-fitting cowling with only the exhaust pipes and the air-intake scoop below to break the smooth lines. The DB cowling was untidy, for there were troughs for the two guns on top, the fat, dumpy spinner for the cannon barrel, various small cooling air scoops, the exhaust pipes and a large air intake scoop on the port side.

The reason for the latter is interesting. While British engine designers used, at that time, a carburettor through the venturi of which the supercharger at the back of the engine drew its air, the Germans preferred to use direct fuel injection into the cylinders and they mounted their supercharger on the port side of the engine. This resulted in the large air scoop which considerably impeded the pilot's view on the ground, since this is the side out of which he normally looks, because the nose of a piston-engined fighter completely blankets his forward view when the tail is down.

The lines of the Me 109 were straight and the corners sharp, giving a general effect of ruthless efficiency in keeping with the Nazi character. In fact, although a good aeroplane, as its continued use throughout the War proved, it was not so outstanding as our own Spitfire, having, for instance, a poorer fire power. It had, however, been designed for rapid quantity production and so many factories had been tooled for its manufacture that the Germans found it difficult to make a change.

It is an interesting fact that one way in which the Me 109 had been "productionized" contributed to its weakness. The rear fuselage had "top-hat" section stringers attached to the skin by a single row of rivets along the "crown"—as opposed to the more usual method of riveting along the two "brims". The result of this was that, although there was sufficient metal present to carry the loads of high-speed manoeuvring, the skin and stringers were not fixed together firmly enough, so that the unstabilized sheet metal sometimes buckled when overloaded, such as when pulling out of a dive too quickly. Features of the Me 109 were the use of automatic leadingedge slots to give aileron control near the stall and slotted flaps to reduce landing speed. The slots were unusual for a fighter, since most designers are afraid of the ill-effect of the slats opening during aerobatic manoeuvres. It was actually because of his previous experience when designing light aeroplanes for competitions that Messerschmitt chose to have slots.

The Poles and the French also entered the War with fighters of their own design, but the former were overwhelmed in a few days and the latter were somewhat undistinguished. One French type, the Dewoitine D-520, had a performance comparable with our aeroplanes and was in large-scale production at Toulouse when France capitulated in 1940. It was, perhaps, fortunate that the Germans decided to suspend production and put this factory on to making their own bombers, of which the first was not completed until 1943—and then the R.A.F. destroyed the factory.

But to return to the D-520, which was an aeroplane of individualistic design. The Hispano-Suiza moteur-canon was not as compact as the Merlin and was trickier to cowl. It was heavier, too, so that the cockpit had to be placed rather far aft to balance the extra weight. The D-520 had the slick lines of a racer rather than a fighter and one can imagine its being flown with Gallic dash. Somewhat handicapped by an engine of rather under 1,000 h.p., the D-520 yet had a maximum speed of 330 m.p.h. at 13,000 feet, and climbed to that height in just under four minutes. With the 20 mm. engine-mounted cannon, two rifle-calibre machine-guns in the fuselage and two more in the wing, armament was comparable with the Me 109 and the weight and span were about the same.

It is clear that in the early stages of the War, Britain was the only country determined to achieve performance without extreme wing loadings. The reasoning behind this viewpoint was important. The Air Ministry realized that in an emergency our small country would have to train pilots quickly and also that in war improvised aerodromes would have to be used. Therefore, the greatest emphasis was placed upon having aeroplanes that were easy to fly and, in fact, pilots have on occasion been sent solo on both the Spitfire and the Hurricane direct from primary trainers. The Me 109, on the other hand, was a delicate instrument designed for professional pilots, and was just that much more tricky to handle. Of the American fighters at the outbreak of the War, the less said the better. They lacked engine power, performance and armament, while those few (obtained expensively on Lease-Lend terms) that reached the R.A.F. were unfit for operational use—even during the most hard-pressed period of the Battle of Britain.

Not all fighters of the Second World War were singleseaters , the multi-seat fighter reappeared. In Britain was evolved an interesting, if short-lived type, the turret fighter, of which the Boulton Paul Defiant is the best example. Encouraged by the excellent four-gun power-operated turrets being made for the bombers, the R.A.F. decided to try the effect of having them in a small, fast, single-engined aeroplane. The Defiant, whose turret was also designed and made by Boulton Paul, was superficially rather like the Hurricane and was about the same size. The crew of two were over the wing and a retractable fairing was fitted behind the turret which, when lowered, allowed a wide rearward field of fire. There were no fixed front, guns. The Defiant was, naturally, more heavily loaded than the single-seater fighters, but it had excellent handling qualities and a speed of about 310 m.p.h.

A squadron of Defiants went into action over Dunkirk for the first time on May 29th, 1940 and had the amazing record of destroying 37 enemy aeroplanes. The Germans mistook the squadron for twelve exceptionally careless Hurricanes and dived on their supposedly defenceless tails, only to be destroyed by a withering concentration of fire. Tragically for the R.A.F., the Germans learned rapidly by their mistake and a few days later decimated the squadron by attacking from the front. The Defiant was then transferred to night fighter work, in which it had a moderate success. It is surprising that no advantage was taken of the similarity of the Hurricane and Defiant to operate in mixed formations. Possibly this would have been done if our fighters had been wanted for patrols over a battle line as in the First World War, instead of being thrown against bomber formations attacking our cities.

The more common form of the multi-seat fighter was that required to escort bombers or to make long-standing patrols off the coast looking for stray enemies. The French had one, the Potez 63, and the Germans another, the Me 110—which were somewhat alike in appearance, although very different in performance.

To obtain enough power for a performance comparable with the single-seaters two engines were required, even so, the weight of extra fuel to feed two engines and give the extra range resulted in aeroplanes about the size of the Blenheim light bomber. The Me 11o had the same slim, straight lines as the 109 and a long "conservatory" on top of the fuselage above the wing, with the pilot in the front and the gunner at the rear. In this design, unlike the Defiant, the pilot was the aggressor, being armed with two 20 mm. cannon and four machine-guns mounted in the nose. The rear gunner had two hand-operated flexible machine-guns which were not of much use against multi-gun fighters, although they must have helped the man's morale. The second crew member's main duty was to assist with radio and navigation and act as look-out on behalf of the relatively unwieldy aeroplane. Like the Me 109, the Me no had some structural faults, but these were cured and it was used throughout the War, with various armament, as a fighter/ bomber and night fighter, in which duties it proved much more successful than as a bomber escort.

The two-seater fighter, because of its size and weight, must always be at a disadvantage to the single-seater once a dogfight has begun—perhaps that is why the R.A.F. had no longrange fighters when the War started. This fact, however, proved a severe embarrassment, particularly for night defence, since the Hurricanes and Spitfires had not the endurance to go up on standing patr61s. Fighters were also needed to protect shipping round our coasts from hit-and-run raids. This shortage was met by true British improvisation. A box of four machineguns was mounted under the bomb bay of the Bristol Blenheim. This combination proved reasonably effective as a night fighter, although its speed of under 300 m.p.h. was low for intercepting bombers unless they were fairly close.

Despite improvisation, work was in hand to make a real night bomber destroyer. The R.A.F.'s secret weapon, radiolocation had surprised the Luftwaffe in the Battle of Britain because ground control could place our limited fighter strength exactly where it would do most good and could keep the fighters on the ground until the last possible moment, so conserving fuel and increasing their effective endurance. A compact light-weight radar (it was then called radio-location) set was being made for night fighters called A.I., Airborne Interception. To carry A.I. the first production R.A.F. twinengined fighter was on the way—also an adaptation!

The Air Ministry were undoubtedly caught by surprise over the need for twin-engined long-range fighters and it was the enterprise and foresight of the Bristol Aeroplane Company that produced the Beaufighter at the right time. At the end of 1938, the firm decided that it would be possible to adapt their Beaufort torpedo-bomber into a fighter. The economy of such a scheme was, they felt, bound to appeal to the government , already hard pressed to meet the armament programme. In eight months, on July 17th, 1939, the prototype flew and the Beaufighter was actually operational as a night fighter by August 1940.

The "Beau" was a lineal descendant of the Blenheim and its wing plan was very similar—and it also had a very short nose. The reason for the retrousse effect was that the highpowered Bristol Hercules radials had to project a certain distance ahead of the wing to avoid vibration, and this meant cutting down on other weight ahead of the c.g. The wing was actually a strengthened version of the Beaufort's wing, as was also the undercarriage, so that there were many common parts. The pilot of the Beau had one of the roomiest cockpits ever to exist on a fighter. This was because the Beaufort had two seats, side-by-side, and the same wing/fuselage fittings were used for both aircraft. The result was a peculiarly triangular -sectioned, "tumblehome" fuselage, which was used to house cannon ammunition, radar operator, radar and radio. With four 20 mm. cannon in the fuselage and six .303 in. machine-guns in the wing the Beaufighter had terrific hitting power.

Although a very successful aeroplane the Beau was tricky. In particular there was trouble because of the guns being mounted in the bottom of the fuselage. When they were fired, the recoil caused the nose to dip enough for the pilot to lose his shadowy target in the dark. At one time this trouble was viewed so seriously that an experimental Beau was built with a fourgun top turret, but the bulk and weight ruined performance and the idea was dropped. There was also a strong tendency to swing on take-off and a danger of the aeroplane flick rolling if an engine cut suddenly. To improve stability a dihedral tail of larger area was introduced, which had the effect of increasing both fin and tail plane area in one stroke. Toward the end of the War, when it had been loaded up with a torpedo and rockets, a huge dorsal fin was also added to improve control in single-engined flight. Operationally, the Beau suffered from the large space dividing the pilot and radar operator—the cannon and ammunition filled the fuselage above the wing—and on all subsequent night fighters the crew has been close-grouped.

The desperate need of Coastal Command for a long-range fighter to counter the German shipping destroyers led to the adoption of variants for this work which carried extra navigational equipment, dinghies, etc. Most Beaufighters had Bristol Hercules radials of from 1,590 to 1,725 h.p., but the Mark II was fitted with the standard 1,280 h.p. Merlin XX power plants as used on the Lancaster. This Mark II was the fastest Beau because of the clean nacelles, having a maximum speed of about 350 m.p.h., but it also had more side area ahead of the c.g. and so was rather less stable directionally. The Mark VI was the most widely used both as a night fighter and for longrange work. It was very successful in Burma where the Japanese soldiers called it "Whispering Death" because of its quiet approach. When the Americans first came to Europe their night fighter squadrons were originally equipped with Beaufighters lent by the R.A.F. (it is not generally known that Britain also lent the U.S.A.A.F. many hundreds of Spitfires and Mosquitos).

While on the subject of two-seater fighters it is appropriate to mention the D.H.98, the Mosquito, although it actually was conceived by Captain de Havilland as a bomber. The idea, proposed even before the War in 1938, was to have a small unarmed bomber that was so fast that no fighter would be able to catch it. As a precaution against possible shortages in light alloys, it was to be made almost entirely of wood. When the War started Captain de Havilland put his scheme to the Air Ministry, which ordered a prototype that flew on November 25th, 1940. Flight tests were very successful and further prototypes were ordered—as fighters and for photographic reconnaissance.

The Mosquito F.Mk.II prototype flew on May 15th, 1941 and the first squadron became operational a year later. The essence of the Mosquito was to use two Merlin engines, thus doubling the power over the single-seater fighter, and to combine these with the smallest practicable wing and the smallest and cleanest possible fuselage and nacelles. Great care in design did, in fact, result in a speed and ceiling comparable with those of the Spitfire. It is fairly obvious that, however well streamlined they may be individually, a fuselage plus two nacelles must present a greater frontal area and overall drag than a single fuselage combined with its engine—which gives some idea of the skill with which the Mosquito was designed. Also, like most really beautiful aeroplanes which succeed in "looking right", the Mosquito was delightful to fly and land despite a stalling speed of over 100 m.p.h.—in those days an almost unheard-of figure.

With its high performance, built-in range (the bomber was designed to cover 1,500 miles) and manoeuvrability the Mosquito F.Mk.II was obviously destined to fill the R.A.F.'s desperate shortage of long-range fighters. Adaptation was simple; the cockpit was fitted with a straight, optically-flat armoured-glass windscreen for the gunsight and armour plate; the bomb-aimer's station in the nose was used for a "nest" of four .303 Browning guns; and four 20 mm. cannon were mounted in the bomb bay. The navigator helped the pilot considerably on long flights and, of course, since he sat close to the latter's right hand, communication was far better than in the Beau.

Subsequent history of the Mosquito traces the wartime development of the multi-seater fighter. The F.Mk.II was used largely as an intruder, that is it was sent over enemy territory at night to attack their aerodromes as their bombers were taking off or landing. Coastal Command, beset in the Battle of the Atlantic by long-range, shore-based Focke-Wulf Condor bombers as well as having to deal with submarines, demanded Mosquitos. Their versions were the F.B.Mk VI and F.B.Mk VIII, F.B. indicating fighter-bomber. In the first, the rear part of the bomb bay was retained for two 500 lb. bombs, two more could be carried under the wings, or eight R.P. (rockets), or two 50 gallon drop tanks—the Christmas tree process had restarted! The second type carried a 6 pdr., 57 mm. anti-tank gun in place of the cannon and heavy armour, for attacking submarines and shipping, the .303 guns were retained as a means of discouraging counter-fire during the run in.

In parallel with these essentially long-range fighters there were, naturally, night fighter versions with A.I. radar in which, once again, the side-by-side crew stations proved a great advantage. The radar scanner was fitted in the nose under a di-electric plastic panel in place of the Browning guns. The first of these night fighters, the N.F.Mk.XII, had Rolls-Royce Merlin 21 or 23 engines with two-speed singlestage superchargers, but the latest marks (actually not in service until after the War) had two-stage supercharged Merlins.

The Germans did little to develop the multi-seat fighter. There were the Me 210 and Me 410, evolved from the Me 110, but they were adapted to fast bomber duties rather than their original role. The curious paradox was that German night fighters and intruders were mostly adapted bombers! The probable reason for this was that radar was an all-British invention and German airborne equipment was very bulky, having been developed from an early set captured by them. During the fighting in the Western Desert a Beaufighter was attacked on its way across the Mediterranean and forced to land in French African territory, at that time controlled by the traitor Admiral Darlan. The pilot was badly wounded and failed to explode the destruction charge in the A.I. set and the aircraft and equipment were given to the Germans by the collaborationists. It is curious that the German radar sets evolved from this captured equipment required a most complex array of di-pole aerials, in contrast to the neat internal ones developed in Great Britain.

Late in the War, the Americans put a night-fighter/intruder into service, the massive Northrop P-61 Black Widow, which was as large and heavy as a light bomber. This aeroplane is one of the few twin-boom types to go into service. Instead of mounting the tail plane and rudder on the end of the fuselage, the latter was cut short behind the wing and, instead, the engine nacelles were extended by nearly twenty feet, flattened to form fins and rudders and the tail plane mounted between them. This layout is a difficult one to design because there is no cross bracing to keep the open frame which it forms from distorting. Further1 See Chapter VIII for details of bomber and photographic reconnaissance Mosquitos and also performance and other data.

more, engine vibrations add to the troubles and so the resulting design is usually heavier than a conventional one. There is usually some very cogent reason for a designer adopting tail booms.

In the case of the Black Widow there was an unusual requirement for rear view. Experience with night fighters had shown that the quarry was often lost when the pilot over-ran his target, usually by passing under it. The Black Widow was an attempt to build this feature into a new aeroplane. The deep nacelle contained four 20 mm. cannon in the bottom and A.I. radar in the nose, behind which successive "steps" gave the pilot his forward view, then the radar operator, then a barbette of four .5 in. guns, and in the tail cone the rear gunner looking up and aft. The barbette was arranged so that it could be locked by the pilot and the guns fired forward with the cannon, or the rear gunner could aim and fire them by remote control should the aeroplane pass under its quarry.

Another twin-boom aeroplane used in quantity was the Lockheed Lightning, P-38. In this case the reasons behind the choice of booms were rather complex. The U.S. Air Corps specification dated from 1936 and called for a speed of at least 360 m.p.h. and for a very long range as a bomber escort. Long range meant a large amount of fuel, with big wings to lift it, and there was no single engine powerful enough to fulfil all these requirements. To keep down head resistance the Allison V-1710 liquid-cooled vee engine was chosen, rather than the radials that have been most commonly used by the Americans since 1930 or thereabouts. To obtain the very high ceiling necessary for escorting the new Air Corps Flying Fortress bombers the recently developed exhaust turbo-supercharger was required. Now the turbo-supercharger (in which the exhaust from the engine turned a turbine which drove the compressor) was a large contraption for mounting in a small nacelle, which would, in any case be almost fully occupied by the main undercarriage. So, by a process of elimination, the designer was driven to adopt the tail-boom layout.

The Lightning was a curious-looking aeroplane. It was large, the span being 52 ft., and the pilot was perched above the front spar of the wing inside a high glazed cupola with a long nose in front of him containing a 20 mm. cannon and four .5 in. machine-guns. The nacelle/boom layout was unique: in the nose the closely-cowled engine with a scoop under the spinner for the intercooler intake, then the undercarriage, under the wing, and the scoop for the engine air, which led into the supercharger. Above the trailing-edge of the wing the boom carried the turbine, fed by a collector pipe from the engine exhausts. Well down the boom there were ducts on each side for the radiators. To overcome some of the troubles associated with booms, the engines were geared to give opposite rotation to the airscrews a bad feature in wartime because of the duplication of spares which it causes. The Lightning was too large to be manoeuvrable enough to catch single-engined fighters, although an attempt was made to overcome this disadvantage by arranging the flaps so that they could be partly extended for combat, thus reducing the wing loading and allowing tighter turns. The Lightning was put through the usual gamut of wartime "development", that is the adding of tanks, bombs and rockets under the wings and adaptation for many duties for which it was never intended. Incidentally, although the P-38 prototype flew in January 1939, production versions were not delivered until the middle of 1941.

To combine long range with speed for the war against Japan, de Havillands were asked to develop a single-seater fighter from the Mosquito. They achieved what at first seemed impossible by making an aeroplane that was even more slender and graceful, the Hornet. The Japanese War ended before it went into action, but the type survived both in the R.A.F. and the Royal Navy as the fastest piston-engined fighter. As a naval night fighter a second cockpit was fitted aft of the wing where the observer's weight balanced that of the ugly proboscis containing the A.I. radar.

So important is the effect of increased frontal area to a twinengined fighter that several attempts have been made to mount the engines in tandem, despite the complications inevitable with such layouts. Before the war Antony Fokker made a tail boom fighter, the D.23, with an engine in the nose and tail of the nacelle, an arrangement that had the additional advantage of counteracting torque reaction without involving special gearboxes. During the War, working secretly under the occupation , General M. Vernisse of the Arsenal de I'Aeronautique evolved a fighter, the VB 10, having one liquid-cooled engine behind and another in front of the pilot and driving counterrotating airscrews through concentric shafts with the aid of special constant-torque couplings invented by General Vernisse himself. Another project was the Dornier 335 night fighter, although in this case the second engine was turned about to drive a propeller behind the tail.

In all these cases, the aeroplane became large and cumbersome , so defeating the object of the design. Another basic fault, and one shared by single-engined types with counterrotating airscrews intended to reduce torque, was the difficulty in adjusting the fin area to suit flight with one airscrew stopped. In any case, the advent of unlimited quantities of power in the form of the jet engine curtailed further work on these lines.

The American ideas on single-engined fighters during the War—and even today for that matter—have ever been toward size. With the solitary exception of the North American Mustang (designed to a British Air Ministry specification) they were heavy and had high wing loadings. For some reason during the thirties the Americans neglected the liquid-cooled engine and put all their energies into making high-powered radials. When war came they had to go on using radials and the large, deep cowlings involved set the pattern for the rest of the fuselage. The Republic Thunderbolt (P-47) was so fat that the R.A.F. used to say that the pilots took evasive action when attacked by undoing their harness and dodging about the fuselage. A measure of the weight of the U.S. fighters is that, whereas British types weighed around 8,000 lb., the German about the same, and the Japanese under 7,000 lb., the Americans were all 12,000 lb. or more fully loaded. Despite their greater weight, most of these U.S. fighters had little more wing area than their lighter counterparts in other air forces, so that their wing loading and, consequently, their powers of manoeuvre were impaired and they landed fast.

The depth of the American fuselages proved of great worth in ship-planes—more by luck than judgement one suspects. When the British Spitfire was adopted for carrier work, its fuselage skin was found to be lacking in rigidity for the harsh shock of deck landing when the arrester hook pulls the aeroplane sharply to a halt. On the other hand, the deep fuselages of aeroplanes like the Grumman Hellcat being in effect much fatter "tubes", stood up well to this rough treatment. The Mustang was ordered by the Air Ministry in 1940 when it was feared that British fighter production could not keep pace with the losses suffered in the fury of the German attack. It was a remarkable all-out effort on the part of the company, being designed and built in 100 days, accepted before the end of 1940, first deliveries reaching the R.A.F. in November of the following year. Unfortunately, the Allison V-1710 engine had no output at height without the turbo-supercharger and so

the Mustang was relegated to low-level, fighter-reconnaissance duties.

The limitations of the Mustang were a great disappointment and the Ministry of Aircraft Production decided to get RollsRoyce to fit the then new Merlin 61 two-stage supercharged engine into two airframes. The results were phenomenal, the Mustang exceeded 400 m.p.h. and behaved well at great heights. Encouraged by the success of this experiment, North American engineers re-designed the Mustang (or P-51 as it was now called having been adopted by the U.S.A.A.F.) to take the 1,520 h.p. Packard V-1650-3, the licence-built Merlin 68.

The Mustang closely followed British practice, lying somewhere between the Spitfire and the Hurricane in appearance— it combined the Spit's slimness with the Hurry's wide track undercarriage. The most unusual feature was the depth of the fuselage under the cockpit caused by the radiator duct. Early machines had a hinged cockpit hood, but when the Merlin version began to see action early in 1944 a British designed bulged sliding hood was fitted as a modification. The dangers of attack from the rear were by then fully realized and all belligerents were taking steps to improve rearward vision in fighters. This first change was followed by an extensive design revision: the whole top of the rear fuselage was lowered and a large sliding bubble canopy was fitted, the reduction in side area being compensated by the addition of a dorsal fin. Original armament consisted of two synchronized .5 in. guns in the fuselage (a trans-Atlantic touch), two further .5 in. and four .303 in. in the wings. Later all guns were put in the wings and mountings for bombs, rockets or drop tanks were provided.

It is, however, from the fighter progress of the principal belligerents, Britain and Germany, that most can be learned. Even in a War it takes so long to apply the lessons of experience to completely new designs that a late starter like the U.S.A. finished the War (apart from the Mustang and Hellcat) with versions of pre-war fighters. Even the R.A.F. and the Luftwaffe relied largely upon the latest Spitfires and Me 109s, by then close on ten years old.

In the Battle of Britain the Hurricane and Spitfire had proved to be outstanding, but the former was too slow to deal with the Luftwaffe's escorting fighter cover.1 However, the complete destruction of the Supermarine Works at Woolston 1 In his despatch on the Battle of Britain the Lord Dowding revealed that the average speed of production Hurricanes was only 305 m.p.h. meant that Spitfire replacements could scarcely be maintained, while Hurricane numbers were nearly doubled by the end of the action, so that the burden of the general fighting fell to the latter. Top cover, fighter-to-fighter combats were the responsibility of the Spit and its speed and agility led to the German fighter-pilot's warning cry "Achtung Spitfeuer!"

Combat experience proved that even eight guns did not give all the fire-power that could be desired, and the Hurricane was given two extra .303 in. guns in the outer part of the wing to bring the total up to a dozen. The thin Spitfire wing had no room for extra guns, but the wings were adapted to take two 20 mm. cannon in place of the four inboard machine-guns, while retaining the four outboard guns. The Mk. IIC Hurricane, introduced in 1941, had four 20 mm. cannon—which for over ten years was destined to be the British "classic" fighter armament.

Gradually, the Hurricane became the low-level fighter, used for general ground attack and in particular, as a "tank-buster" in the Western Desert. Its ruggedness and capacity for accepting multifarious loads, such as two 40 mm. anti-tank guns or two 500 lb. bombs made it an excellent fighter-bomber, a new class that had arisen out of the smoke of the desert battles and the fighter sweeps over occupied Europe that started in 1941. Fitted with catapult spools or arrester hook, there was the Sea Hurricane which served with the Royal Navy on catapult-armed merchant ships (C.A.M.S.) and aircraftcarriers .

During all its changes in duty the Hurricane altered little in shape. By contrast, the Spitfire changed a great deal during its development—and yet it always retained a recognizable resemblance to the original prototype. There is one way of improving a fighter which is inevitable, increasing the power— and that was done many times to the Spit until the original 1,030 h.p. of the Merlin had been replaced by the 2,035 h.p. of the Griffon 61. Almost everything else was also tried, wingtip, fuselage and tail shape all being altered successively. Even the method of fuselage construction was changed from the early intercostals to one with continuous stringers. Yet despite it all there seemed to be something about the Spit's character which survived indomitably to the end. Today, as I write, it is almost twenty years since the Spitfire design was started by R. J. Mitchell and there are still, in this jet age, a few flying as gunnery co-operation aeroplanes. It will be a sad day indeed when the last of those lovely elliptical wings leaves our skies, never to be seen again, save in the inappropriate atmosphere and dust of museums.

The various "operations" on the Spitfire serve as a perfect guide to the alterations in appearance which changing requirements during the last War were to make in the piston-engined fighter. Lower wing loading than the Me 109 gave the Spit the advantage of height and manoeuvrability, but when higherpowered Messerschmitts with rounded wingtips giving greater span and area, came into service, something had to be done to increase the operational ceiling. Pointed extensions were fitted to replace the normal elliptical tips, the increase in area was not great, but the span was raised to 40 ft. 2 in. and this improved the lift at great heights. A pressure cabin and a two-stage supercharged Merlin were also added, combining, in the Mark VII, to give a ceiling of 44,000 ft. and a speed of 416 m.p.h.

The two-stage supercharger, because of the intercooler and the double blower, made a longer engine, which naturally lengthened the nose of these new Spitfires. Higher power also meant a larger radiator duct, under the starboard wing, and an intercooler radiator, that was housed with the oil cooler under the port wing. Experience in the Western Desert led to a decision to fit sand filters on the air intakes of all aeroplanes, so that they would not be restricted in deployment. The first filter intake caused a most unaesthetic bulge under the nose costing several miles an hour, but later this was greatly improved and no drag penalty was paid.

Almost at the same time as wing extensions were being fitted for high altitude, the German pilots of the new Fw 190 discovered a way of avoiding Spitfires. They could not out-turn them, but they could, because of their smaller span, roll more quickly and so they used to tip smartly over on one wingtip and then slide neatly away from their pursuer. To meet these tactics, the wingtips were removed from some Spitfires. The "clipped Spit" had a span of only 32 ft. 7 in. and, because its ceiling and climb had been somewhat impaired, it was called a "low-altitude" fighter (L.F.)—although this was a relative term. It is noteworthy that when landing the extended wing gave a more gentle, and the clipped wing a more sudden, stall than did the standard shape. This is attributable to the "spilling " of the air from the tip and is closely connected with the performance near the ceiling where, although speeds are higher, the thin air behaves as if it were moving slowly. the last of those lovely elliptical wings leaves our skies, never to be seen again, save in the inappropriate atmosphere and dust of museums.

The various "operations" on the Spitfire serve as a perfect guide to the alterations in appearance which changing requirements during the last War were to make in the piston-engined fighter. Lower wing loading than the Me 109 gave the Spit the advantage of height and manoeuvrability, but when higherpowered Messerschmitts with rounded wingtips giving greater span and area, came into service, something had to be done to increase the operational ceiling. Pointed extensions were fitted to replace the normal elliptical tips, the increase in area was not great, but the span was raised to 40 ft. 2 in. and this improved the lift at great heights. A pressure cabin and a two-stage supercharged Merlin were also added, combining, in the Mark VII, to give a ceiling of 44,000 ft. and a speed of 416 m.p.h.

The two-stage supercharger, because of the intercooler and the double blower, made a longer engine, which naturally lengthened the nose of these new Spitfires. Higher power also meant a larger radiator duct, under the starboard wing, and an intercooler radiator, that was housed with the oil cooler under the port wing. Experience in the Western Desert led to a decision to fit sand filters on the air intakes of all aeroplanes, so that they would not be restricted in deployment. The first filter intake caused a most unaesthetic bulge under the nose costing several miles an hour, but later this was greatly improved and no drag penalty was paid.

Almost at the same time as wing extensions were being fitted for high altitude, the German pilots of the new Fw 190 discovered a way of avoiding Spitfires. They could not out-turn them, but they could, because of their smaller span, roll more quickly and so they used to tip smartly over on one wingtip and then slide neatly away from their pursuer. To meet these tactics, the wingtips were removed from some Spitfires. The "clipped Spit" had a span of only 32 ft. 7 in. and, because its ceiling and climb had been somewhat impaired, it was called a "low-altitude" fighter (L.F.)—although this was a relative term. It is noteworthy that when landing the extended wing gave a more gentle, and the clipped wing a more sudden, stall than did the standard shape. This is attributable to the "spilling " of the air from the tip and is closely connected with the performance near the ceiling where, although speeds are higher, the thin air behaves as if it were moving slowly.

The vicissitudes of the Spitfire give such a direct cause and effect to changes in shape that I have devoted a whole page of sketches showing some of the changes to supplement the pictures tracing its ancestry. The longer nose with the new Merlins upset the balance of the side areas and a larger rudder, with a pointed tip, was introduced to give increased rudder control, particularly at take-off, where the extra torque was also troublesome. A retractable tail wheel was adopted in the Mark VII and was standard on all the later types—except the IX, which was an "interim" version using an earlier airframe (Mk. V) with the new engine, an expedient due to production difficulties.

Improved performance of enemy fighters led to the installation of the larger and more powerful Rolls-Royce Griffon. The airscrew shaft of this engine was lower in relation to the cylinder block than was that of the Merlin and this gave the Roman nose that characterizes the later marks. Increased side area and torque led this time to a larger fin as well as rudder.' In order to avoid lengthening the undercarriage, which in turn would have meant altering the wing recesses, a five-bladed airscrew was used to give the required blade area without increasing diameter. Later still, after the War, a six-bladed counter-rotating airscrew was fitted to do the same job more effectively and, at the same time, to reduce the torque reaction.

Operationally, an improved rear view was considered necessary and, in consequence, the top of the fuselage was lowered and a "bubble" canopy was fitted. Finally, in the latter part of the War the Spitfire was flying over 100 m.p.h. faster than its original design speed and some curious things were occurring to the wings and, in particular, the ailerons. What was happening was that pilots were making their first encounters with "compressibility"—the unusual behaviour of air near the speed of sound. The troubles were countered by altering the outer part of'the wing, increasing the size of the ailerons and fitting them with tabs to help the pilot overcome the unusual forces. There is not space to deal with the various equipment changes, the fitting of drop tanks—always the "slipper" type under the fuselage because of the wing radiators—bombs and rockets; nor is it possible to describe the various marks, from i I to 24, with many sub-variants.1 The navalized Seafire must also be omitted, since the changes made there, apart from the catapult spools and arrester hook, were not externally obvious. The ingenious intricacies of the folding wings remained unnoticed to the casual observer.

One point, perhaps, is worth recording. At first the hook was fitted below the fuselage, just behind the wing where it was easy to install. It was soon found that this frequently led to the tail lifting as the aeroplane was pulled up sharply and the tip of the airscrew blades were broken against the deck. Because of this a "sting" hook which extended from the tail below the rudder was designed. Tragically this was not in time for the grim Anzio landing in Italy, where fighter cover was to have been provided by carrier-borne Seafires. The carrier could not steam because of minefields and there was no wind, so that landings were fast and within three days every airscrew had been broken.

Magnificent as it was, the Spitfire was to have had a successor, the Spiteful, built to a 1943 specification. This aeroplane had a fuselage very like the later Griffon Spitfires, but the pilot was raised to improve the forward view and the wing was completely re-designed. The aerodynamically refined semi-elliptical shape was replaced by a more easily built plan form with two straight tapers. A new laminar-flow low-drag aerofoil section was used (with special low-drag radiator ducts), and the undercarriage was arranged to retract inward. Thus the three chief criticisms of the Spitfire were met: bad ground view, narrow wheel track and difficult wing construction—but the Spiteful showed scarcely any performance increase over the Spitfires with the same engine.

Contemporaneously with the Spitfire's wartime evolution the rival Hawker company embarked on a new series of fighters to replace the Hurricane, the Typhoon and the Tempest, both of which had rather chequered careers. These were, incidentally, the first British fighters to approach the weight of the American ones. The Typhoon was an obvious development of the Hurricane , with the emphasis on the pilot's view, and based on the new 2,000 h.p.-plus Napier Sabre liquid-cooled engine. This was a remarkable power plant with twenty-four small sleevevalve cylinders arranged in a X. Compact, and an exquisite piece of precision machinery, it was far too refined for the rough-and-tumble of War. Nevertheless, it was our first 2,000 h.p. engine and as such it was pressed into service. Although the Typhoon did not go into action until the summer of 1942 it was built to a pre-war specification—the prototype flew on February 24th, 1940—concentration on the Hurricane for the Battle of Britain having delayed it.

The Typhoon was designed as a 400 m.p.h. fighter, but at the time the importance of a thin wing for high speed was not fully realized. The Air Ministry also had a scheme for interchangeable power plants at that time and the unfortunate Typhoon was designed to take either the Sabre I, the Bristol Centaurus air-cooled radial, or the Rolls-Royce Vulture liquidcooled X! Faced with this problem, the designer had to compress his whole engine installation into a "box" of closely defined cross-section and could make no strategic distribution of coolant weight. The result of this was that to preserve c.g. balance the engine was packed in too close to the leading edge of the thick wing and the aeroplane vibrated as the slipstream buffeted the wing root. Gradually troubles were overcome and the Typhoon did yeoman service as a ground attack fighter during the advance in Europe when its four 20 mm. cannon were supplemented by eight rockets or two 1,000 lb. bombs.

Sidney Camm realized the need for a thinner wing before the Typhoon went into service and he evolved a modified version. This had a Centaurus engine and a thinner, semielliptical wing and its name was changed to Tempest. Another version had the 2,400 h.p. Sabre IIB engine and it was this one, the Mark V, that saw service first—a little confusing. In the Tempest, apart from the new wing, the engine was moved forward, to cure the vibration, and the side areas adjusted by a forward extension of the fin. Altogether about 30 m.p.h. was gained. In 1943 work was started on a new fighter incorporating the lessons of the others and which was, in fact, a radialengined counterpart of the Spiteful. The Tempest wing was used, the span being reduced by omitting the centre section, and to it a completely new and refined fuselage was attached. Once again, the pilot's view had been carefully considered from the first and the way the fuselage rises to the cockpit is reminiscent of the original Fury, the biplane, after which it was named.

The Bristol Centaurus engine has a close pressure cowling developed from that on the Tempest II. This form of cooling , (like the ducted radiator) behaves like a jet engine at high speed. The principle is to take fast-moving air into the smallest possible space between spinner and cowling, expand and slow it in the larger space inside where it absorbs heat from the cylinders and is finally ejected through narrow outlets which increase its speed, giving some thrust. In the Fury the outlet slots are on each side of the fuselage and the hot gases from the tailpipes of the eighteen cylinders add further velocity and thrust. The Fury, modified with folding wings and arrester hook, became the Royal Navy's standard Sea Fury fighter, destined to be its mainstay in the Korean War.

The Luftwaffe's chief counter to the R.A.F.'s improved fighters was the Focke-Wulf Fw 190 with the BMW 801 fourteen -cylinder, air-cooled, radial engine. This was a beautifully proportioned aeroplane, which actually flew before the war but, perhaps fortunately for us, the German authorities were not convinced that a radial engine was appropriate for a fighter.

After the Battle of Britain had shown up the deficiencies of the Me 109, the Fw 190 was put into production and saw action in 1941. In June 1942 a German deserter kindly landed one intact in the South of England!

Although the BMW 801 engine was only three inches less in diameter than the Centaurus, by close cowling and very careful fuselage and canopy geometry the designer achieved an outstanding all-round view with the minimum head resistance and good streamlining. Behind the engine cowling the fuselage changed to a triangular section which blended well with the cockpit and gave a flat bottom that must have had a useful cushioning effect when landing. The flat, straight lines of the fuselage, and of the wing and tail also, were well suited to mass production—a characteristic of all German types.

Shortly before the War the Germans made serious efforts to evolve interchangeable power plants and they achieved more success than similar efforts did in this country. The result was (as in the Typhoon) a liquid-cooled motor with its radiator in the nose. One of these was fitted to the Fw 190D, which was first met by the Allies late in 1943. This power egg had a nose radiator in a short annular duct with "frill" outlet gills round the spinner, an arrangement that seems to have had a low drag, but as far as view was concerned combined the disadvantages of both radial and liquid-cooled, being both fat and long. To compensate for the nose, the rear fuselage was lengthened and about six inches were added to the leading edge of the fin. When the "long-nosed" Fw 190 had proved itself the designer, Kurt Tank, renamed it with his own instead of his company's initials and it became the Ta 152. It was developed, by adding fourteen feet to the span, and using a very highly supercharged engine with special chemical power boosters, into a high-altitude reconnaissance aeroplane. A speed of 472 m.p.h. at 41,000 feet was claimed.

Armament of the Fw 190 was varied: originally there were two synchronized rifle calibre guns on top of the fuselage, two more in the wing root and two 20 mm. guns in the wings. Later, cannon were put in the wing roots, then 13 mm. guns in the cowling, later still 30 mm. cannon could be fitted in the wings, and so on. . . . Drop tanks and up to 1,100 lb. of bombs could be carried, so that this part of its history followed that of other fighters.

The Messerschmitt Me 109, although undoubtedly a less effective aeroplane than the Fw 190 or its contemporary the Spitfire, remained in service throughout the War and was progressively developed. There were actually no less than fourteen sub-variants of the Me 109G, itself the third wartime main series, the others being the E and F. The main airframe suffered little change apart from the lowering of the cabin-top to reduce head resistance (and, incidentally, the view) and the addition of rounded wingtips to improve the altitude performance . Other variations were almost all connected with engine and armament. As more and more powerful engines were used to bolster up the performance, so the bumps and angles of the cowling changed and the size of the wing radiator ducts grew.

The engine carried either a 20 mm. or 30 mm. cannon and in the top cowling were two 13 mm. guns, while two more cannon could be carried under the wing.

An idea of the Messerschmitt's relative cleanness, bearing in mind that it was smaller than the Spitfire, may be had from

the fact that the fastest variant, the Me 109G-10 with a 2,000 h.p. DB 605D engine, could do 428 m.p.h. at 24,250 ft., compared with 450 m.p.h. for the Spitfire F.Mk.XIV or 460 m.p.h. for the P.R. XIX with similar power.