Testing flights continued all over 1942, but the engines proved to be problematic as the Junkers Jumo 004 was just marginally better than the BMW 003. The airframe was ready and tested by late 1942 but the lack of engines delyaed its mass production until 1944 and even then, deliveries were low with only 28 Me.262s in June, 59 in July and only 20 in August.
During the summer 1943 the Jumo 004A engine was counting with over 100 test-hours, with a time between overhauls of 50. Anyway, it proved not suitable for mass production due to its size and weight and its need of strategical materials like nickel, copper and molybdenum which were running short. Therefore, the Jumo 004B was designed to take as minimum amount of strategic materials as possible. Every heat-resistant metal parts, including the combustion chamber, were changed to mild steel and included an aluminium coating to give protection against oxidation. The whole engine represented a design compromise to minimize the use of strategic materials and simplify manufacture. With lower-quality steels of the Jumo 004B the engine required overhaul just after 25 hours for metallurgical test on the turbine. If the test was passed, it required an additional 10 hours run-test making it 35 hours the absolute limit for the turbine test.
When BMW's and Junkers' axial compressor turbojet engines were characterized by a sophisticated design that could offer a considerable advantage, the lack of rare materials put it into disadvantage when compared to the 'partly axial-flow' of both British and American jet engines which in spite of their simpler design, they had a longer operational life span. Sir Frank Whittle, pioneer of British turbojet technology, concludes in one of his report that "it was in the quality of high temperature materials that the difference between German and British was most marked".
The aircraft could carry 2000L of fuel (440imp gall/530 US gall) in two 900L tanks, one each fore and aft of the cockpit plus an additional 200L ventral fuselage tank beneath. The expected flight endurance of the Me.262 was of 60-90 minutes. It was operated on J2 fuel (which was derived from brown coal), with the option of diesel and the option of oil and high octane B4 aviation petrol. As the fuel consumption doubled the rate of any typical twin-engined fighter of the era, a low-fuel warning indicator was placed in the cockpit that remained pilots when the fuel amount was below 250L.
The Messerschmitt Me.262 V8 was the first one to be armed with four 30mm Mk.108 cannons in the nose.
The Me.262 V9 was the ninth prototype which was used as a test platform for both communications gear and electrically operated acoustic homing and detection devices. It was probably used to examine the adaptation into a night-fighter. On 1st October 1944 it was fitted with a new streamlined canopy and tests gave excellent aerodynamical improvements over the regular versions which were already at the frontlines. However, it came too late to make any impact in the war.
The Me.262 V-10 was a bomber prototype with a towed bomb which would be the prototype for the bomber variants of the Me.262.
Sources:
1. https://en.wikipedia.org/wiki/Messerschmitt_Me_262
2. https://www.valka.cz/Messerschmitt-Me-262-t15721 (translated)
3. http://www.luftwaffe39-45.historia.nom.br/aero/me262.htm (translated)
4. The Me.262 Stormbird: From the pilots who flew, fought and survived it.
5. Salamander Books - The Complete Book of Fighters
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