Throughout the 1920s and early 1930s, most air forces were equipped with biplane fighters that were little more advanced than their twin-gunned ancestors that had fought on the Western Front in World War I. By the mid-1930s, aero-engine design and airframe construction techniques had advanced dramatically, and newer prototypes were appearing with stressed-skin construction, retractable undercarriages, and top speeds of over 300 mph. These aircraft entered service in the late 1930s, just in time for World War II.
Many of these new designs had flush-fitting cockpit canopies (e.g., Bf-109, Spitfire), partly for reasons of aerodynamic efficiency but also because it was thought (incorrectly) that the classic World War I dogfight would be impossible at speeds of over 300 mph. Visibility from the cockpit turned out to be very important; about 80 percent of pilots shot down during the war never saw their attackers. Bulged cockpit hoods were fitted to some fighters to alleviate the problem, but later aircraft were fitted with clear Perspex canopies that gave unrestricted rearward vision.
Most fighters are defined by performance and maneuverability. Of the two, performance was probably more important during World War II. A speed advantage over an opponent (ignoring surprise attacks and tactical advantage) enabled a fighter to dictate the terms on which combat was joined and also enabled an easy escape if the fight was not going well. Comparisons tend to be problematic since performance varied dramatically with altitude; an aircraft that had a significant advantage against an opponent at sea level could find the position dramatically reversed at 30,000 ft. In any case, in-service improvements could change performance characteristics, and new aircraft usually had the latest equipment and engine variants, further complicating the issue.
Maneuverability is essentially a measure of the ability of an aircraft to change direction and is dictated to a large extent by the wing loading of the aircraft. Some lightly loaded aircraft (particularly the early Japanese fighters) were capable of remarkably tight turns, but the ability of the aircraft to roll and establish the turn also played a part. Some fighters, such as the Focke-Wulf FW 190, had an excellent rate of roll that to some extent compensated for their average rate of turn. An aircraft's handling qualities degrade to a greater or lesser extent as the weight inevitably increases with each new version, and heavier aircraft tend to be less agile than lighter ones. Twin-engine aircraft are particularly disadvantaged in roll as more mass is distributed around the centerline than with a single-engine aircraft.
Many early fighters had tactical limitations because of control difficulties. There is a relationship between the size and shape of a control surface and the effort required to move it; it becomes progressively more difficult to deflect as speed increases and may in some cases exceed the ability of the pilot to apply sufficient force. For example, the Messerschmitt Bf-109 had very heavy stick forces at normal speeds; Spitfires had metal-covered ailerons fitted late in 1940 to make high-speed rolls easier; and the Mitsubishi Zero had (in common with most other Japanese fighters) huge control surfaces that gave outstanding agility below about 200 mph (as with the F4U Corsair and Tempest) but almost none above 300 mph. Much later in the war, new designs had spring-tabs fitted on control surfaces to balance the extra air resistance at high speeds.
In 1939 few, if any, aircraft had self-sealing fuel tanks or armor. Operational experience in the European Theater showed that aircraft were very vulnerable unless so equipped, and in 1940 crash programs were instituted to retrofit fuel tank liners and armor plate to most aircraft. This added weight reduced performance slightly, but most air arms were prepared to accept the price. However, the Japanese army and navy were not. As a result, most Japanese aircraft, which were lightly constructed anyway, were extremely vulnerable even to machine-gun fire, and cannon hits caused immediate and catastrophic damage. The use of armor and other protection on bombers had already obliged designers to fit heavier weapons, and continuing development encouraged the adoption of cannon. The Messerschmitt Me-262 was probably the ultimate World War II bomber-killer with four 30 mm cannon, only three hits from which were usually required to down a four-engine bomber.
The increased performance of fighters brought compressibility effects into play. As speeds increased at high altitude, airflow over parts of the structure could reach the speed of sound (Mach 1.0) even in quite shallow dives, leading to buffeting, nose-down trim changes, and eventually loss of control of the aircraft. Recovery from the dive was difficult, and reducing power usually led to the nose dropping further! Sometimes the only solution was to wait until the aircraft reached warmer air at lower altitudes and the local speed of sound increased above the critical value. These effects were not well understood at the time and caused tactical limitations to some aircraft: the Lockheed P-38 ran into serious compressibility effects above Mach 0.68, and the Messerschmitt Me-262 could reach its limit of Mach 0.83 only in a very shallow dive.
World War II was a fascinating period for fighter development; the following aircraft were the most significant fighters of the conflict.
GermanyThe Messerschmitt Bf-109 entered service in its earliest form (Bf-109B) in 1937 and remained in service throughout the war. It continued to be modified during the conflict. It received progressively more powerful engines, and in common with many other aircraft, its handling qualities and maneuverability degraded with successive versions. The Bf-109 could not turn tightly (although the 109E and 109F models were better than commonly supposed), but it was a very effective fighter when handled correctly, possessing excellent dive and zoom climb capabilities. The later versions in particular were better at high altitude, but the controls became very stiff at high speeds, and visibility from the cockpit was poor. Approximately 35,000 examples were built.
The Messerschmitt Bf-110 was designed as a long-range escort fighter, entering service with the Luftwaffe in 1939. It had a useful top speed and was well armed, but it could not meet contemporary single-engine fighters on equal terms. It was not a success as an escort fighter, but it was first used as a fighter-bomber during the Battle of Britain, and from 1943 the Bf-110 G-4 enjoyed much success as a radar-equipped night fighter. Approximately 6,150 were built.
ItalyThe Fiat CR-42 entered service with the Italian air force in 1939 and was exported to Belgium, Sweden, and Hungary. It was a highly maneuverable fighter with (for a biplane) good dive acceleration. However, it was lightly armed and quite vulnerable to enemy fire and was not really capable of taking on modern fighters on equal terms. A total of 1,781 were built.
The Macchi Mc 200 first entered service during 1940. A well-built and extremely maneuverable fighter with finger-light controls, it could outturn most of its opponents. It was, however, lightly armed with only two machine guns. The Macchi Mc 202 was a Mc 200 airframe with a license-built Daimler-Benz DB601 engine. It was probably the most effective Italian fighter of the war, retaining most of its predecessor's maneuverability, and was able to meet the Spitfire Mk V on at least equal terms. A total of 2,251 Mc 200 and Mc 202 aircraft were built.
JapanThe Nakajima Ki.43 ("Oscar" by the Allied identification system) entered service late in 1941 and was highly maneuverable but not particularly fast (304 mph at 13,120 ft). It had extremely sensitive controls that unfortunately stiffened significantly at speed. Allied fighters found that they could not turn with the Oscar but could outdive and outzoom it. Its armament was weak; pilot armor and self-sealing tanks were introduced with the more powerful Ki.43-IIa late in 1942, but the Oscar remained vulnerable to enemy fire. It continued to undergo development throughout the Pacific war, 5,751 examples being built.
The Kawasaki Ki.45 ("Nick") was designed to a 1937 specification for a long-range escort fighter and entered service early in 1942. The Ki.45 was increasingly used as a night fighter from early 1944 using two 12.7 mm or 20 mm weapons firing obliquely upward. It was relatively successful against U.S. B-29 night raids, and it later became the first Japanese army air force type to be used on a kamikaze mission. A total of 1,701 were built.
The Nakajima Ki.44 interceptor ("Tojo") first appeared in service late in 1942, although some of the 10 prototypes were evaluated on operations during 1941 and early 1942. The Tojo was reasonably maneuverable with a good climb, but its high takeoff and landing speeds made it unpopular with pilots. The Ki.44-IIc appeared in mid-1943; armed with two 40 mm cannon and two machine guns, it was quite effective against high-flying U.S. B-24 and later B-29 bombers. A total of 1,233 were built.
The Kawasaki Ki.61 ("Tony") appeared early in 1943 and was the only Japanese fighter powered by a liquid-cooled engine to see operational service. It carried self-sealing fuel tanks and armor and was more maneuverable than were heavier opponents. Its dive characteristics were also very good indeed, comparable to the best U.S. fighters. The Ki.61 was one of very few Japanese fighters able to engage the U.S. B-29 bombers at high altitude. A total of 3,078 Ki.61s were built. Engine production was slow and the power plant gave problems in service, so early in 1945 many Ki.61 airframes were reengined with a 1,500 hp Mitsubishi Ha 112 radial to produce the Ki.100. Only 272 were built by war's end, but it was the best Japanese fighter during the conflict.
The Kawanishi N1K1-J ("George") evolved from a floatplane and was one of the best fighters of the Pacific Theater. Entering service early in 1944, it had automatic combat flaps and was outstandingly maneuverable, its pilots coming to regard even the F6F Hellcat as an easy kill. Its climb rate was, however, relatively poor for an interceptor, and the engine was unreliable. The later N1K2-J was redesigned to simplify production, and limited numbers entered service early in 1945. A total of 1,435 aircraft of the N1K series were built.
The Nakajima Ki.84 ("Frank") was one of the best Japanese fighters of the war. It entered service late in 1944. The Ki.84 could outmaneuver and outclimb late-model P-51 and P-47 fighters and had excellent maneuverability. It was well armed, strong, and well protected, and it was easy for novice pilots to fly. Production examples were beset with manufacturing faults and engine difficulties, causing performance to suffer, particularly at high altitude. A total of 3,470 Ki.84 aircraft were built.
FranceThe Dewotine D.520 was designed as a private venture and entered service with the French air force in 1940. It was probably the most effective French-designed fighter of the war, shooting down 100-plus enemy aircraft in exchange for 54 losses during the Battle of France. After the fall of France, the D.520 continued in Vichy French service and was encountered by the Allies in Vichy North Africa. A total of 905 were built.
Great BritainThe Hawker Hurricane entered service in 1937 and was the first monoplane fighter of the Royal Air Force (RAF), serving on all fronts. The Hurricane Mk I was the major RAF fighter during the Battle of Britain. On paper it was average, but it had hidden strengths; it was an excellent gun platform and was more maneuverable than the Spitfire. Its controls did not stiffen appreciably at high speed, and it was very strong, being able to withstand maneuvers that would literally pull the wings off its contemporaries. Later versions (MK IID, Mk IV) were mainly built as fighter-bombers. A total of 14,233 Hurricanes were built.
The Supermarine Spitfire was a very advanced design when the Mk I entered service in 1938, and it was able to accept progressively more powerful engines and heavier armament as the war progressed, with only a slight reduction in handling qualities. The "Spit" was fast and very maneuverable and was widely regarded as a pilot's aircraft. In performance terms, it was usually considered superior to its direct opponents, although the FW-190 gave Spitfire Mk V pilots a hard time until the Mk IX redressed the balance in mid-1942. The Spitfire was continuously updated and revised with many specialist high- and low-altitude versions, and the late-war marks had a particularly impressive performance. It remained in production until after the war. A total of 20,351 were built.
The Bristol Beaufighter was designed as a private venture using components from the Beaufort torpedo-bomber. The Mk IF entered service as a radar-equipped night fighter late in 1940. It operated successfully in Europe, the Western Desert, the Mediterranean, the Far East, and the Pacific as a night fighter, long-range fighter, ground-attack aircraft, and torpedo-bomber. It was a big, heavy aircraft with a good performance at low level and a very heavy armament. A total of 5,562 Beaufighters were built.
The Hawker Typhoon was rushed into service late in 1941 to combat the German FW-190 menace, but it suffered from teething troubles. Its performance at low altitude was very good, particularly its acceleration and dive, but its performance above about 20,000 ft was poor because of its thick wing. The Typhoon was used later in the war as a ground-attack aircraft. The Hawker Tempest appeared early in 1944 and was an aerodynamically cleaner Typhoon with a thinner, laminar-flow wing. The Tempest was very fast and was one of the best late-war fighters. It could be maneuvered easily at high speed and had outstanding dive acceleration and zoom climb capabilities. It was, however, not easy to fly to its limits. A total of 3,300 Typhoons and 800 Tempests were built.
The De Havilland Mosquito was conceived as a bomber but was also produced in radar-equipped night-fighter and fighter-bomber versions. The NF.II entered service with the RAF in May 1942 and was very successful on night-intruder missions; Mosquito night fighters were used over Germany from late 1944 onward and seriously hampered German night-fighter operations. A total of 1,053 Mosquito night fighters of all versions were built; the most numerous fighter version was the FB.VI, of which 2,718 were built.
Soviet UnionThe Polikarpov I-16 Rata entered service late in 1934, the first of the new generation of monoplane fighters. More than 450 machines were operationally tested in the Spanish Civil War, and I-16s bore the brunt of the initial German assault on the Soviet Union. The Rata was marginally stable at best but was outstandingly maneuverable; it had a very good zoom climb but poor diving characteristics. Approximately 20,000 were built, the type remaining in service until 1943.
The Yakovlev series of fighters began with the Yak-1 in early 1942. It was fast at low altitude, but both the Yak-1 and the more powerful Yak-7 were slightly short on range. The Yak-9 appeared late in 1942 with a more powerful engine and particularly effective ailerons; it was capable of outturning all its opponents at low altitude. The Yak-3 was a specialized low-altitude fighter, entering service early in 1944. It had excellent performance below about 10,000 ft and was the preferred mount of the Normandie-Niemen Groupe de Chasse. Approximately 30,000 Yak fighters were produced, of which 16,700 were Yak-9s.
The Lavochkin La-5 was a very successful adaptation of the problematic LaGG-3 airframe to take a 1,330 hp Shvetsov M-82 radial engine. The La-5 entered service late in 1942 and was an immediate success as a highly maneuverable low-altitude fighter. The more powerful La-5FN appeared in mid-1943; it was faster and lighter with improved controls that gave better handling qualities. It is thought that about 15,000 Lavochkin fighters were built, although the total may well have been nearer 20,000.
United StatesThe Curtiss P-40 entered service in 1940. The aircraft was based on the Curtiss P-36, which was itself a reasonable fighter; French P-36 variants (Hawk 75A) accounted for approximately 70 percent of French air force kills during the Battle of France. The P-40 had reasonable dive acceleration but a poor ceiling and climb. It was average in most departments, its major attribute being that it was available in numbers when required. It was, however, continuously developed until December 1944, when the last of 13,738 P-40s, a P-40N, rolled off the production line.
The Bell P-39 Airacobra entered service in 1941. It was fast at low altitudes and pleasant to fly, but its performance fell away above 12,000 ft. Together with the P-40, the P-39 bore the brunt of the early fighting in the Pacific until later U.S. types appeared. The P-39 was rejected by the RAF but was used with some success as a low-altitude fighter by the Soviet Union, which took more than half the production total of 9,558 machines. The P-39 was used by at least 20 Soviet aces, including Aleksandr Pokryshkin (59 kills) and Grigorii Rechkalov (56 kills).
The Lockheed P-38 Lightning entered service in numbers early in 1942 and was possibly the ultimate long-range tactical fighter of the war. Its long range and twin engines made it the primary U.S. Army Air Corps fighter in the Pacific Theater. Not as maneuverable as a single-engine fighter, it was fast with very effective armament and an outstanding zoom climb. Compressibility problems handicapped diving maneuvers, however. A total of 9,923 Lightnings were built.
The North American P-51 Mustang was one of the most successful fighters of World War II. Offered to the British Air Purchasing Commission in April 1940 as an alternative to the Curtiss P-40, the P-51A entered service early in 1942. Using the same Allison engine as in the P-40, it was appreciably faster than the P-40 because of its laminar-flow wing and efficient cooling system. It had an excellent dive and zoom climb and was quite maneuverable, but it lacked performance at high altitude. The Mustang's performance was transformed by the substitution of a 1,620 hp Rolls-Royce Merlin engine in the P-51B, increasing the ceiling by nearly 10,000 ft and providing a marked performance advantage over Luftwaffe piston-engine fighters, particularly above 20,000 ft. A total of 15,686 P-51s were built.
The Republic P-47 Thunderbolt was designed for high-altitude combat and was the heaviest single-engine fighter of the war. Entering service early in 1943, the P-47B was at its best at high speed and altitude. Maneuverability was quite good at high speed, but it became ponderous at lower speeds. Although its climb rate was poor, it had exceptional dive acceleration and was very rugged. The major production model was the P-47D, which had provision for bombs and rockets and was a very effective ground-attack aircraft. A total of 15,683 Thunderbolts were built. Andy Blackburn
Green, William. Famous Fighters of the Second World War. 2d ed. London: Book Club Associates, 1979.; Jarrett, Philip, ed. Aircraft of the Second World War. London: Putnam, 1997.; Munson, Kenneth. Fighters, Attack and Training Aircraft, 1939–45. Poole, UK: Blandford Press, 1975.; Price, Alfred. World War II Fighter Conflict. London: Macdonald and Janes, 1975.