Me 262

The Messerschmitt Me 262, nicknamed ''Schwalbe'' (German: "Swallow") in fighter versions, or ''Sturmvogel'' (German: " Storm Bird") in fighter-bomber versions, is a fighter aircraft and fighter-bomber that was designed and produced by the German aircraft manufacturer Messerschmitt. It was the world's first operational jet-powered fighter aircraft.

The initial design of what would become the Me 262 started in April 1939, prior to the start of the Second World War. While the aircraft performed its maiden flight on 18 April 1941, this was using piston engine instead of jet propulsion; it was not until 18 July 1942 that the first jet-powered flight was performed. Progress on the project was delayed by problems with engines, metallurgy and top-level interference from figures such as Hermann Göring, head of the Luftwaffe, and Adolf Hitler. The latter advocated from the Me 262 to be operated as a ground-attack/bomber aircraft rather than a defensive interceptor, thus necessitating a redesign. Accordingly, the aircraft was eventually brought into operational status with the Luftwaffe during mid-1944. In its operational configuration, the Me 262 was both faster and more heavily armed than any Allied fighter, including the British jet-powered Gloster Meteor. The Allies countered its effectiveness in the air by frequently attacking the aircraft while on the ground and during takeoff and landing.

Being one of the most advanced aviation designs to attain operational status during the Second World War, the Me 262's roles included light bomber, reconnaissance, and experimental night fighter versions. The Me 262 proved to be an effective dogfighter against Allied fighters; German pilots claimed a total of 542 Allied aircraft shot down, although higher claims have sometimes been made. Operations were plagued with reliability issues, which were largely a result of widespread strategic materials shortages as well as design compromises on the Junkers Jumo 004 axial-flow turbojet engines that powered it. Attacks by Allied forces on fuel supplies during the deteriorating late-war situation also reduced the effectiveness of the Me 262 as a fighting force. Armament production within Germany was focused on more easily manufactured aircraft. 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 entered operational service.

While German use of the Me 262 ended with the close of the Second World War, a small number were operated by the Czechoslovak Air Force until 1951. Also, Israel was allegedly counted as a user of a handful (between two and eight) of Me 262s, which were supposedly built by Avia and supplied covertly, although there have been no official confirmations of such use.
It also heavily influenced several designs, such as the Sukhoi Su-9 (1946) and Nakajima Kikka. Numerous captured Me 262s were studied and flight-tested by the major powers, and ultimately influenced the designs of post-war aircraft such as the North American F-86 Sabre, MiG-15 and Boeing B-47 Stratojet. Several aircraft have survived on static display in museums, while multiple privately built flying reproductions have also been produced; these are commonly powered by modern General Electric CJ610 engines.

Design and development

Origins

Several years prior to the Second World War, the Germans foresaw the great potential for aircraft powered by the jet engine constructed by Hans von Ohain in 1936. After the successful test flights of the world's first jet aircraft—the Heinkel He 178—within a week of the invasion of Poland which started the conflict, they adopted the jet engine for an advanced fighter aircraft. As a result, the Me 262 was already under development as ''Projekt'' 1065 (P.1065) before the start of the war. The project had originated with a request by the ''Reichsluftfahrtministerium'' (RLM, Ministry of Aviation) for a jet aircraft capable of one hour's endurance and a speed of at least . Woldemar Voigt headed the design team, with Messerschmitt's chief of development, Robert Lusser, overseeing.

During April 1939, initial plans were drawn up and, following their submission in June 1939, the original design was very different from the aircraft that eventually entered service. Specifically, it featured wing-root-mounted engines, rather than podded ones. The progression of the original design was delayed greatly by technical problems with the new jet engine. Because the engines were slow to arrive, Messerschmitt moved the engines from the wing roots to underwing pods, allowing them to be changed more readily if needed. That turned out to be important, both for availability and maintenance. Since the BMW 003 jets proved heavier than anticipated, the wing was swept slightly, by 18.5°, to accommodate a change in the center of gravity.

The jet engine program was waylaid by a lack of funding, which was primarily due to a prevailing attitude amongst high-ranking officials that the conflict could be won easily with conventional aircraft. Among these was Hermann Göring, head of the Luftwaffe, who cut the engine development program to just 35 engineers in February 1940 (the month before the first wooden mock-up was completed). The aeronautical engineer Willy Messerschmitt sought to maintain mass production of the piston-powered, 1935-origin Bf 109 and the projected Me 209. Major General Adolf Galland had supported Messerschmitt through the early development years, flying the Me 262 himself on 22 April 1943. By that time, the problems with engine development had slowed production of the aircraft considerably. One particularly acute problem was the lack of an alloy with a melting point high enough to endure the temperatures involved, a problem that had not been adequately resolved by the end of the war. After a November 1941 flight (with BMW 003s) ended in a double flameout, the aircraft made its first successful flight entirely on jet power on 18 July 1942, propelled by a pair of Jumo 004 engines.

Ludwig Bölkow was the principal aerodynamicist assigned to work on the design of the Me 262. 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 of single-spar cantilever construction, with stressed skins, varying from skin thickness at the root to at the tip. To expedite construction, save weight, and use fewer strategic materials late in the war, the wing interiors were not painted. The wings were fastened to the fuselage at four points, using a pair of and forty-two bolts.

During mid-1943, Adolf Hitler envisioned the Me 262 as a ground-attack/bomber aircraft 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. Hitler's interference helped to extend the delay in bringing the ''Schwalbe'' into operation; (other factors contributed too; in particular, there were engine vibration problems which needed attention). In his memoirs, Albert Speer, then Minister of Armaments and War Production, claimed Hitler originally had blocked mass production of the Me 262, before agreeing in early 1944. Similar criticisms were voiced by Lieutenant General Adolf Galland. Hitler rejected arguments that the aircraft would be more effective as a fighter against the 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.

The Me 262 is often referred to as a " swept wing" design as the production aircraft had a small, but significant leading edge sweep of 18.5° which likely provided an advantage by increasing the critical Mach number. Sweep, uncommon at the time, was added after the initial design of the aircraft. The engines proved heavier than originally expected, and the sweep was added primarily to position the center of lift properly relative to the center of mass. (The original 35° sweep, proposed by Adolf Busemann, was not adopted.) On 1 March 1940, instead of moving the wing backward on its mount, the outer wing was re-positioned 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 inboard section's leading edge (between the nacelle and wing root) was later swept to the same angle as the outer panels, from the "V6" sixth prototype onward throughout volume production.

Test flights

Testing showed that the Me 262 handled much better than previous fighters, such as the Bf 109 or Fw 190. Handling was so improved over the previous aircraft that a report by Major Ernst Englander stated that any Bf 109 pilot could convert to the Me 262 with only an hour of instruction. According to his report, even bomber pilots who converted to fly the Me 262 only required three instruction flights, and less than 5% had any difficulty retraining. The Me 262 had a gentle stall and gentle landing characteristics compared to previous German fighters. Its handling improved with speed and would lose much less speed during turning. It had a cruising speed of 465 mph, which was faster than the top speed of most other fighters of the day. It also had far better visibility in every direction compared to previous German fighters. Due to lack of engine torque, if a single engine was lost the aircraft remained easily controlled and landed without issue. Its only major deficiency was that brakes could not be used until the nose wheel had touched down, because engaging them before would smash the nose wheel strongly into the runway, potentially destroying the nose wheel and even the aircraft. The quality of the aircraft was high, with only 10% of aircraft returned for minor defects such as wings being out of alignment by under 1 degree. It could reach 515 mph without issue, although because it could reach extreme speeds in dives, components such as bomb racks would sometimes tear off.

Test flights began on 18 April 1941, with the Me 262 V1 example, bearing its ''Stammkennzeichen'' radio code letters of PC+UA, but since its intended BMW 003 turbojets were not ready for fitting, a conventional Junkers Jumo 210 engine was mounted in the V1 prototype's nose, driving a propeller, to test the Me 262 V1 airframe. When the BMW 003 engines were installed, the Jumo was retained for safety, which proved wise as both 003s failed during the first flight and the pilot had to land using the nose-mounted engine alone. The V1 through V4 prototype airframes all possessed what would become an uncharacteristic feature for most later jet aircraft designs, a fully retracting conventional gear setup with a retracting tailwheel—indeed, the very first prospective German "jet fighter" airframe design ever flown, the Heinkel He 280, used a retractable tricycle landing gear from its beginnings and flying on jet power alone as early as the end of March 1941.

The V3 third prototype airframe, with the code PC+UC, became a true jet when it flew on 18 July 1942 in Leipheim near Günzburg, Germany, piloted by test pilot Fritz Wendel. This was almost nine months ahead of the British Gloster Meteor's first flight on 5 March 1943. Its retracting conventional tail wheel gear (similar to other contemporary piston-powered propeller aircraft), a feature shared with the first four Me 262 V-series airframes, caused its jet exhaust to deflect off the runway, with the wing's turbulence negating the effects of the elevators, and the first takeoff attempt was cut short.

On the second attempt, Wendel solved the problem by tapping the aircraft's brakes at takeoff speed, lifting the horizontal tail out of the wing's turbulence. The first four prototypes (V1-V4) were built with the conventional gear configuration. Changing to a tricycle arrangement—a permanently fixed undercarriage on the fifth prototype (V5, code PC+UE), with the definitive fully retractable nosewheel gear on the V6 (with ''Stammkennzeichen'' code VI+AA, from a new code block) and subsequent aircraft corrected this problem.

Test flights continued over the next year, but engine problems continued to plague the project, the Jumo 004 being only marginally more reliable than the lower-thrust (7.83 kN/1,760 lbf) BMW 003. Early engines were so short-lived that they frequently needed replacement after only a single flight. Airframe modifications were complete by 1942 but, hampered by the lack of engines, serial production did not begin until 1944, and deliveries were low, with 28 Me 262s in June, 59 in July, but only 20 in August.

By mid-1943, the Jumo 004A engine had passed several 100-hour tests, with a time between overhauls of 50 hours being achieved. However, the Jumo 004A engine proved unsuitable for full-scale production because of its considerable weight and its high utilization of strategic material (Ni, Co, Mo), which were in short supply. Consequently, the 004B engine was designed to use a minimum amount of strategic materials. All high heat-resistant metal parts, including the combustion chamber, were changed to mild steel (SAE 1010) and were protected only against oxidation by aluminum coating. The total engine represented a design compromise to minimize the use of strategic materials and to simplify manufacture. With the lower-quality steels used in the 004B, the engine required overhaul after just 25 hours for a metallurgical test on the turbine. If it passed the test, the engine was refitted for a further 10 hours of usage, but 35 hours marked the absolute limit for the turbine wheel. While BMW's and Junkers' axial compressor turbojet engines were characterised by a sophisticated design that could offer a considerable advantage – also used in a generalized form for the contemporary American Westinghouse J30 turbojet – the lack of rare materials for the Jumo 004 design put it at a disadvantage compared to the "partly axial-flow" Power Jets W.2/700 turbojet engine which, despite its own largely centrifugal compressor-influenced design, provided (between an operating overhaul interval of 60–65 hours) an operational life span of 125 hours. Frank Whittle concludes in his final assessment over the two engines: "it was in the quality of high temperature materials that the difference between German and British engines was most marked"

Operationally, carrying of fuel in two tanks, one each fore and aft of the cockpit; and a ventral fuselage tank beneath, the Me 262 would have a total flight endurance of 60 to 90 minutes. Fuel was usually J2 ( derived from brown coal), with the option of diesel or a mixture of oil and high octane B4 aviation petrol. Fuel consumption was double the rate of typical twin-engine fighter aircraft of the era, which led to the installation of a low-fuel warning indicator in the cockpit that notified pilots when remaining fuel fell below .

Unit cost for an Me 262 airframe, less engines, armament, and electronics, was . To build one airframe took around 6,400-man-hours.

Operational history

Introduction

On 19 April 1944, '' Erprobungskommando'' 262 was formed at Lechfeld just south of Augsburg, as a test unit (''Jäger Erprobungskommando Thierfelder'', commanded by ''Hauptmann'' Werner Thierfelder) to introduce the Me 262 into service and train a corps of pilots to fly it. On 26 July 1944, Leutnant Alfred Schreiber with the 262 A-1a W.Nr. 130 017 damaged a Mosquito reconnaissance aircraft of No. 540 Squadron RAF PR Squadron, which was allegedly lost in a crash upon landing at an air base in Italy. Other sources state the aircraft was damaged during evasive manoeuvres and escaped.

Major Walter Nowotny was assigned as commander after the death of Thierfelder in July 1944, and the unit redesignated '' Kommando Nowotny''. Essentially a trials and development unit, it mounted the world's first jet fighter operations. Trials progressed at a slow pace; it was not until August 1944 that initial operational missions were flown against the Allies; the unit made claims for 19 Allied aircraft in exchange for six Me 262s lost. Despite orders to stay grounded, Nowotny chose to fly a mission against an enemy bomber formation flying some above, on 8 November 1944. He claimed two P-51Ds destroyed before suffering engine failure at high altitude. Then, while diving and trying to restart his engines, he was attacked by other Mustangs, forced to bail out, and died. The ''Kommando'' was then withdrawn for further flight training and a revision of combat tactics to optimise the Me 262's strengths.

On 26 November 1944, a Me 262A-2a Sturmvogel of III.''Gruppe''/KG 51 'Edelweiß' based at Rheine-Hopsten Air Base near Osnabrück was the first confirmed ground-to-air kill of a jet combat aircraft. The Me 262 was shot down by a Bofors gun of B.11 Detachment of 2875 Squadron RAF Regiment at the RAF forward airfield of Helmond, near Eindhoven

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