Piston engine planes saw a spur of development in the second World War. This page shows more information on the technological innovations in this period.
Piston-engine power increased considerably during the war. The Curtiss P-36 Hawk had a 900 hp (670 kW) radial engine but was soon redesigned as the P-40 Warhawk with a 1100 hp (820 kW) in-line engine. By 1943, the latest P-40N had a 1300 hp (970 kW) Allison engine. At war's end, the German Focke-Wulf Ta 152 interceptor could achieve 2050 hp (1530 kW) with an MW-50 (methanol-water injection) supercharger and the American P-51H Mustang fitted with the Packard V-1650-9 could achieve 2218 hp (1650 kW) under war emergency power. The Spitfire Mk I of 1939 was powered by a 1030 hp (770 kW) Merlin II; its 1945 successor, the Spitfire F.Mk 21, was equipped with the 2035 hp (1520 kW) Griffon 61. Likewise, the radial engines favored for many fighters also grew from 1,100 hp (820 kW) to as much as 2090 hp (1560 kW) during the same timeframe.
The first turbojet-powered fighter designs became operational in 1944, and clearly outperformed their piston-engined counterparts. New designs such as the Messerschmitt Me 262 and Gloster Meteor demonstrated the effectiveness of the new propulsion system. Many of these fighters could do over 660 km/h (410 mph) in level flight, and were fast enough in a dive that they started encountering the transonic buffeting experienced near the speed of sound; such turbulence occasionally resulted in a jet breaking up in flight due to the heavy load placed on an aircraft near the so-called "sound barrier". Dive brakes were added to jet fighters late in World War II to minimize these problems and restore control to fighter pilots. Rocket-powered interceptors – most notable the Messerschmitt Me 163 – appeared at around the same time as jet fighters, but proved less effective.
More powerful armament became a priority early in the war, once it became apparent that newer stressed-skin monoplane fighters could not be easily shot down with rifle-caliber machine guns. The Germans' experiences in the Spanish Civil War led them to put 20 mm cannons on their fighters. The British soon followed suit, putting cannons in the wings of their Hurricanes and Spitfires which had previously featured up to twelve machine guns. The Americans, having problems with designing a native cannon design, instead chose to place multiple .50 caliber (12.7 mm) machine guns on their fighters. Armaments continued to increase over the course of the war, with the German Me 262 jet having four 30 mm cannons, capable of downing a heavy bomber with just a few hits. Cannons fired explosive shells, and could blast a hole in an enemy aircraft rather than relying on kinetic energy from a solid bullet striking a critical subsystem (fuel line, hydraulics, control cable, pilot, etc.). A debate existed over the merits of high rate-of-fire machine guns versus slower-firing, but more devastating, cannon.
With the increasing need for close air support on the battlefield, fighters were increasingly fitted with bomb racks and used as fighter-bombers. Some designs, such as the German Fw 190, proved extremely capable in this role – though the designer Kurt Tank had designed it as a pure interceptor. While carrying air-to-surface ordnance such as bombs or rockets beneath the aircraft's wing, its maneuverability is decreased because of lessened lift and increased drag, but once the ordnance is delivered (or jettisoned), the aircraft is again a fully capable fighter aircraft. By their flexible nature, fighter-bombers offer the command staff the freedom to assign a particular air group to air superiority or ground-attack missions, as need requires.Rapid technology advances in radar, which had been invented shortly prior to World War II, would permit their being fitted to some fighters, such as the Messerschmitt Bf 110, Bristol Beaufighter, de Havilland Mosquito, Grumman F6F Hellcat and Northrop P-61 Black Widow, to enable them to locate targets at night. The Germans developed several night-fighter types as they were under constant night bombardment by RAF Bomber Command. The British, who developed the first radar-equipped night fighters in 1940–1941, lost their technical lead to theLuftwaffe. Since the radar of the era was fairly primitive and difficult to use, larger two- or three-seat aircraft with dedicated radar operators were commonly adapted to this role.