Having tried everyone’s patience with two Me 163 model variants, I thought I’d finish you off by adding this short bio on the aircraft’s final development phase. Although the Me 163 had a very short flight endurance even after RLM demanded the throttle facility, something not included in the original ‘full power’ envelope setting, all the aircraft’s fuel was still expended after a few minutes.
This problem was addressed in part by the slightly updated Me 163C. This featured the same HWK 509B or -C dual chamber rocket engine already trialled on the Me 163B V6 and V18 prototypes; the main upper chamber was tuned for high thrust while the lower Marschofen combustion chamber was designed for a much lower thrust output (about 400 kgf maximum) for a more economic cruise. In operation, throttling was accomplished by starting or stopping the main engine which was about four times as powerful as the smaller one. This change greatly simplified the engine, while also retaining much higher efficiency during cruise. Along with slightly increased fuel tankage, the powered endurance rose to about 12 minutes, a 50% improvement. As the aircraft spent only a short time climbing, this meant the time at combat altitude would be more than doubled.
Throughout its development, the RLM proved unhappy with the progress on 163 projects and eventually decided to transfer development to Heinrich Hertel at Junkers. However, Lippisch remained at Messerschmitt and retained the support of Waldemar Voigt, continuing development of the 163C.
At Junkers, the basic plan of the 163C was followed to produce an even larger design, the Ju 248. Retaining the new pressurized cockpit and bubble canopy of the 163C this aircraft would have considerable more fuel capacity and a new retractable landing gear design. On 25 September 1944 a wooden mock-up was shown to officials. The production version was intended to be powered by the more powerful BMW 109-708 rocket engine in place of the Walter power plant.
Prior to the actual building of the Ju 248, two Me 163Bs, V13 and V18, were slated to be rebuilt. Unfortunately, V13 had deteriorated due to weather exposure so only V18 was rebuilt and eventually flown by test pilot Heini Dittmar at a record-setting 1,130 km/h (702 mph) velocity on July 6, 1944. This flight resulted in the near-total destruction of its rudder surface (and the aircraft). Curiously, it is this aircraft that is often identified as the Me 163D but in fact there was no Me 163D as this aircraft was re-built after the Ju 248 project had started.
Hertel had hoped to install Lorin ramjet engines, but this technology was still far ahead of its time. As a stop gap measure, they decided to build the aircraft with a Sondergerät (special equipment) in the form of a Zusatztreibstoffbehälter (auxiliary fuel tank) and two 160 l (35 imp gal) (42.2 US gal) external T-Stoff oxidizer tanks installed under the wings. This would lead to a 10% speed decrease but no negative flight characteristics. Although Junkers claimed the Ju 248 used a standard Me 163B wing, they actually modified the wing internally to hold more C-Stoff fuel. This modification was carried out by the Puklitsch firm.
In November 1944, the aircraft was again re-designated as the Me 263 to show its connection with the Me 163. Both projects were in fact renamed as the Ju 248 Flunder (Flounder) and the Me 263 Scholle (Plaice). In early 1945, Junkers proposed its own project, the EF 127 Walli rocket fighter as a competitor to the Me 163C and Me 263.
The first unpowered flight of the Me 263 V1 was in February 1945. Several more unpowered flights took place that month. The biggest problem had to do with the centre of gravity which was restored with the addition of counterweights. Eventually, the production aircraft would have repositioned the engine or the landing gear installation to solve this problem. The landing gear at this stage was still non-retractable. The results of those first flights however was the aircraft was given a "ziemlich fertigen Eindruck" label meaning that it ‘seemed’ to be ready.
Test flights were eventually stopped because of fuel shortages for the Bf 110 tow-planes. As the Me 263 was not a part of the Jägernotprogramm (Emergency Fighter Program), it was difficult to get the resources it needed. For the time being the plane was not expected to enter production but further development was allowed. The V2 and V3 were not yet ready. The V2 was to get the first fully retractable landing gear and the V3 would have the proposed armament added. Both the V1 and the V2 had the two-chambered HWK 109-509C installed, correcting the center-of-gravity problems but when the opportunity allowed, they nevertheless flew only as gliders.
In April ‘45 the Americans occupied the plant and captured the three prototypes and the mock-up. The V2 was destroyed but another prototype ended up in the USA. The rest was handed over to the Russians, who then created their own Mikoyan-Gurevich I-270 interceptor aircraft from the Me 263 design.
At Messerschmitt the development of the 163 series became seriously impaired by the failing war effort. A two-seat night interceptor as well as the ‘V’ tail versions got no further than wind-tunnel or mock-up stages and the most promising development that would have allowed the 163 to be launched from existing (or new) V-1 ramps was also shelved for lack of resources.
The Me 163 may have accomplished little in the way of being an effective interceptor but like the later and more effective 262 paved the way for post war design and application to say nothing of its appeal to our modelling fraternity.
