Thursday, September 13, 2012
Messerschmitt ME 262 A 1a
The Messerschmitt Me 262 Schwalbe ("Swallow") was the world's first operational jet-powered fighter aircraft. Design work started before World War II began but engine problems prevented the aircraft from attaining operational status with the Luftwaffe until mid-1944. Compared with Allied fighters of its day, including the British jet-powered Gloster Meteor, it was much faster and better armed One of the most advanced aviation designs in operational use during World War II, the Me 262 was used in a variety of roles, including light bomber, reconnaissance and even experimental night fighter versions.
Me 262 pilots claimed a total of 542 Allied kills (although higher claims are sometimes made) against the loss of only about 100 Me 262s in the air. The Allies countered its potential effectiveness in the air by relentlessly attacking the aircraft on the ground and while they were taking off or landing. Maintenance problems and a lack of fuel during the deteriorating late-war situation also reduced the effectiveness of the aircraft as a fighting force. In the end, the Me 262 had a negligible impact on the course of the war as a result of its late introduction and the consequently small numbers that were deployed in operational service. The Me 262 influenced the designs of post-war aircraft such as the North American F-86 Sabre and Boeing B-47 Stratojet.
Several years before World War II, the Germans foresaw the great potential for aircraft of a British invention: the jet engine, invented by Frank Whittle in 1928. As they were in the middle of a great military build up which would lead to war, they ignored the various patents that Whittle had in effect and simply took the idea and developed it into a very advanced fighter aircraft. As a result, the Me 262 was already being developed as Projekt 1065 (P.1065) before the start of World War II. Plans were first drawn up in April 1939, and the original design was very similar to the plane that eventually entered service. The progression of the original design into service was delayed greatly by technical issues involving the new jet engine. Funding for the jet program was also initially lacking as many high-ranking officials thought the war could easily be won with conventional aircraft. Among those were: Hermann Göring, head of the Luftwaffe, who cut the engine development program to just 35 engineers in February 1940; Willy Messerschmitt, who desired to maintain mass production of the piston-powered Bf 109 and the projected Me 209; and Major General Adolf Galland, who supported Messerschmitt through the early development years, flying the Me 262 himself on 22 April 1943. By that time, problems with engine development had slowed production of the aircraft considerably. One particularly acute problem arose with the lack of an alloy with a melting point high enough to endure the high temperatures involved, a problem that by the end of the war had not been adequately resolved.
The project aerodynamicist on the design of the Me 262 was Ludwig Bölkow, later a prominent figure in the post-World War II development of the German aircraft industry. He initially designed the wing using NACA airfoils modified with an elliptical nose section. Later in the design process, these were changed to AVL derivatives of NACA airfoils, the NACA 00011-0.825-35 being used at the root and the NACA 00009-1.1-40 at the tip. The elliptical nose derivatives of the NACA airfoils were used on the horizontal and vertical tail surfaces. Wings were single-spar cantilever construction, with stressed skins, varying from 3 mm (0.12 in) thick at the root to 1 mm (0.039 in) at the tip. The wings were fastened to the fuselage at four points, using a pair of 20 mm (0.79 in) and forty-two 8 mm (0.31 in) bolts.
In mid-1943, Adolf Hitler envisioned the Me 262 as an offensive ground-attack/bomber rather than a defensive interceptor. The configuration of a high-speed, light-payload Schnellbomber ("Fast Bomber") was intended to penetrate enemy airspace during the expected Allied invasion of France. His edict resulted in the development of (and concentration on) the Sturmvogel variant. It is debatable to what extent Hitler's interference extended the delay in bringing the Schwalbe into operation. Albert Speer, then Minister of Armaments and War Production, claimed in his memoirs that Hitler originally had blocked mass production of the Me 262 before agreeing in early 1944. He rejected arguments that the aircraft would be more effective as a fighter against Allied bombers destroying large parts of Germany, and wanted it as a bomber for revenge attacks. According to Speer, Hitler felt its superior speed compared to other fighters of the era meant it could not be attacked and so preferred it for high altitude straight flying.
Although the Me 262 is often referred to as a "swept wing" design, the production Me 262 had a leading edge sweep of only 18.5°, too slight to achieve any significant advantage in increasing the critical Mach number Sweep was added after the initial design of the aircraft, when the engines proved to be heavier than originally expected, primarily to position the center of lift properly relative to the centre of mass. On 1 March 1940, instead of moving the wing backward on its mount, the outer wing was repositioned slightly aft; the trailing edge of the midsection of the wing remained unswept. Based on data from the AVA Göttingen and wind tunnel results, the middle section's leading edge was later swept to the same angle as the outer panels.