Editing Messerschmitt Me 262 (section)

==Design and development==

===Origins===
Before World War II, the Germans saw the potential for aircraft powered by the [[jet engine]] constructed by [[Hans von Ohain]] in 1936.{{sfn|Bauduin|2014|p=66}}{{sfn|Davies|1980|p=572}} 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 (or P.1065) before the start of the war. The project had originated with a request by the ''[[Ministry of Aviation (Nazi Germany)|Reichsluftfahrtministerium]]'' (RLM, Ministry of Aviation) for a jet aircraft capable of one hour's endurance and a speed of at least {{convert|850|km/h|mph kn|abbr=on}}.{{sfn|Christopher|2013|p=59}}{{sfn|LePage|2009|p=183}} [[Woldemar Voigt (engineer)|Woldemar Voigt]] headed the design team, with Messerschmitt's chief of development, [[Robert Lusser]], overseeing.{{sfn|Christopher|2013|p=59}}{{sfn|Dorr|2013|p=54}}

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,{{sfn|Christopher|2013|p=59}} rather than podded ones.{{sfn|Christopher|2013|p=59}} The progression of the original design was delayed greatly by technical problems with the new jet engine. 
Originally designed with straight wings, problems arose when the long delayed engines proved heavier than originally promised. While waiting for the engines, 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.{{sfn|Christopher|2013|p=60}}{{sfn|Dorr|2013|p=61}}

When it became apparent that the BMW 003 jets would be significantly heavier than anticipated, on 1 March 1940, it was decided that instead of moving the wing backward on its mount, the outer wing would be swept slightly rearwards to 18.5 degrees, to accommodate the change in the centre of gravity{{sfn|Christopher|2013|p=60}} and to position the centre of lift properly relative to the centre of mass. (The original 35° sweep, proposed by [[Adolf Busemann]], was not adopted.){{sfn|Christopher|2013|p=48}}

Initially the inboard leading edge retained the straight profile as did the trailing edge of the midsection of the wing.{{sfn|Radinger|Schick|1996|p=18}}

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.{{sfn|Radinger|Schick|1996|pp=12–13}}

The shallow [[leading edge]] sweep of 18.5°  may have inadvertently provided an advantage by slightly increasing the [[critical Mach number]]{{sfn|Loftin|2004}} however, its Tactical (useable) Mach number remained a relatively modest at Mach 0.82 and both German and British test pilots found that it suffered severe controllability problems as it approached Mach 0.86.{{sfn|Brown|2006|p={{pn|date=January 2024}}}}<ref>"A Pilot's Story DVD QUANTA productions</ref>

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.{{sfn|Boyne|1994|pp=58–61}}{{sfn|Heath|2022|p=217}} 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).{{sfn|Christopher|2013|p=59}} The aeronautical engineer [[Willy Messerschmitt]] sought to maintain [[mass production]] of the piston-powered, 1935-origin [[Messerschmitt Bf 109|Bf 109]] and the projected [[Messerschmitt Me 209-II|Me 209]].{{sfn|LePage|2009|p=219}} [[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.{{sfn|Boyne|1994|pp=58–61}} 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.{{sfn|Christopher|2013|p=61}}

[[File:Messerschmitt Me 262.jpg|thumb|left|[[Hans Guido Mutke]]'s Me 262 A-1a/R7 on display at the [[Deutsches Museum]] in [[Munich]]]]

[[Ludwig Bölkow]] was the principal [[Aerodynamics|aerodynamicist]] assigned to work on the design of the Me 262. He initially designed the wing using [[National Advisory Committee for Aeronautics|NACA]] [[airfoil]]s modified with an elliptical nose section.{{sfn|Bölkow|1989|pp=225–287}} 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.<ref>{{Cite web |last=Lednicer |first=David |title=The Incomplete Guide to Airfoil Usage |url=https://m-selig.ae.illinois.edu/ads/aircraft.html |access-date=4 November 2023 |website=UIUC Airfoil Data Site |publisher=Department of Aerospace Engineering, University of Illinois at Urbana-Champaign}}</ref> The elliptical nose derivatives of the NACA airfoils were used on the horizontal and vertical [[empennage|tail surfaces]]. Wings were of single-spar cantilever construction, with [[stressed skin]]s, varying from {{convert|3|mm|in|abbr=on}} skin thickness at the root to {{convert|1|mm|in|abbr=on}} at the tip.{{sfn|Stapfer|2006|p=30}} To expedite construction, save weight, and use fewer [[strategic material]]s late in the war, the wing interiors were not painted.{{sfn|Stapfer|2006|p=34}} The wings were fastened to the fuselage at four points, using a pair of {{convert|20|mm|in|abbr=on}} and forty-two {{convert|8|mm|in|abbr=on}} bolts.{{sfn|Stapfer|2006|p=34}}

During mid-1943, [[Adolf Hitler]] envisioned the Me 262 as a [[Ground-attack aircraft|ground-attack]]/[[bomber]] aircraft rather than a defensive interceptor.{{sfn|LePage|2009|p=9}}{{sfn|Dorr|2013|p=49}} 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;<ref name="Stormbirds History.">{{cite web |url = http://www.stormbirds.com/schwalbe/history/history2.htm |title = Stormbirds History |publisher = Stormbirds.com |access-date = 19 May 2011}}</ref>{{sfn|Roberts|2009|pp= 586, 446, 595}} (other factors contributed too; in particular, there were engine vibration problems which needed attention).{{sfn|Christopher|2013|p=61}} [[Inside the Third Reich|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.{{sfn|Galland|1954|loc=chptr. 28}}<ref name="Stormbirds History."/> 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.{{sfn|Speer|1997|p=363}}

===Test flights===

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]] [[turbojet]]s 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.{{sfn|Ford|2013|p=224}}{{sfn|Dorr|2013|p=28}} 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.{{sfn|Radinger|Schick|1996|p=23}} The V1 through V4 prototype airframes all possessed what would become an uncharacteristic feature for most later jet aircraft designs, a fully retracting [[Conventional landing gear|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 flew on jet power alone as early as the end of March 1941.{{sfn|Buttler|2019|loc=678-775}}

[[File:Messerschmitt Me 262 V3 side-view silhouette.png|thumb|left|Silhouette of the V3 prototype – V1 through V4 similar. Note retracting conventional tail wheel gear]]
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 (district)|Günzburg]], Germany, piloted by [[Fritz Wendel|test pilot Fritz Wendel]].{{sfn|Warsitz|2009|p=143}}{{sfn|Dorr|2013|pp=9, 55}} This was almost nine months ahead of the British [[Gloster Meteor]]'s first flight on 5 March 1943.{{sfn|LePage|2009|p=179}} 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 [[Elevator (aircraft)|elevator]]s, and the first takeoff attempt was cut short.{{sfn|Boyne|2008|p=60}}

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.{{sfn|Boyne|2008|p=60}} The first four [[prototype]]s (V1-V4) were built with the conventional gear configuration. Changing to a [[Tricycle gear|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.{{sfn|Dorr|2013|p=10}}{{refn|The nosewheel was a {{convert|66|x|16|cm|in|abbr=on}} item identical to the [[Messerschmitt Bf 109|Bf 109F]]'s main gear wheel, fitted with a [[Synthetic rubber#History|Buna rubber]] tire and pneumatic drum brake.{{sfn|Stapfer|2006|p=21}}|group="Note"}}

[[File:Me262cockpit color b.jpg|thumb|upright|Me 262 cockpit]]
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&nbsp;kN/1,760&nbsp;lbf) BMW 003. Early engines were so short-lived that they frequently needed replacement after only a single flight.{{sfn|Dorr|2013|p=70}} 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.{{sfn|Boyne|1994|p=}}{{page needed|date=July 2018}}

By mid-1943, the Jumo 004A engine had passed several 100-hour tests, with a time between overhauls of 50 hours being achieved.{{sfn|Meher-Homji|1997|p=785}} However, the Jumo 004A engine proved unsuitable for full-scale production because of its considerable weight and its high utilization of [[strategic material|strategic materials]] (nickel, cobalt, molybdenum), 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 engine represented a design compromise to minimize the use of strategic materials and to simplify manufacture.{{sfn|Meher-Homji|1997|p=785}} 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.<ref>CIOS XXIV-6. "Gas Turbine Development: BMW-Junkers-Daimler-Benz." London, 1946. p. 24.</ref> [[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"{{sfn|Whittle|1953|pp=92–93}}

Operationally, carrying {{convert|2000|litres|impgal usgal|abbr=off}} of fuel in two {{convert|900|litre|impgal usgal|abbr=off|adj=on}} tanks, one each fore and aft of the cockpit; and a {{convert|200|litre|impgal usgal|abbr=off|adj=on}} ventral fuselage tank beneath,{{refn|According to Stapfer, the smaller fuel tank had a capacity of up to {{convert|237.75|usgal|impgal l|abbr=off}}.{{sfn|Stapfer|2006|p=16}}|group="Note"}} the Me 262 would have a total flight [[endurance (aircraft)|endurance]] of 60 to 90 minutes. Fuel was usually J2 ([[Coal liquefaction|derived]] from [[brown coal]]), with the option of [[Diesel fuel|diesel]] or a mixture of oil and high [[octane]] B4 [[Aviation fuel|aviation petrol]].{{sfn|Stapfer|2006|p=16}} 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 {{convert|250|L|impgal usgal|abbr=on}}.{{sfn|Stapfer|2006|p=16}}

Unit cost for an Me 262 airframe, less engines, armament, and electronics, was {{Reichsmark|87,400|link=yes}}.{{sfn|Stapfer|2006|p=26}}{{refn|By comparison, a new [[Volkswagen Beetle|Volkswagen Type 1]] was priced at ''RM''990.{{sfn|Gilmore|1992|pp=36–40}}|group="Note"}} To build one airframe took around 6,400-man-hours.{{sfn|Stapfer|2006|p=26}}