Dornier Do 635 (Zwilling) / (He 635 / Ju 635) Long-Range Reconnaissance Aircraft Proposal
The Dornier Do 635 was a proposed long-range reconnaissance platform centered around the joining of two Do 335 heavy fighter aircraft.
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Several German aircraft makers of World War 2 were convinced of the merits inherent in joining two aircraft by way of a common center wing section. This was most famously attempted by Heinkel with their He 111 medium bomber to produce the He 111Z "Zwilling" ("Twin") and the idea found even more success in America with the post-war North American F-82 "Twin Mustang" which saw combat service in the Korean War. The Dornier Do 635 existed as another short-lived attempt by German engineers to create a new "super aircraft" from an existing design.
The Do 635 was proposed during 1944 and the idea was simple enough on paper - join two examples of the promising Do 335 heavy fighter with a common center wing section while retaining all other original aspects of the high-performance fighter. The Do 335 was a unique fighter design in the grand scope of World War 2 as it showcased a pair of engines seated in line across a well-streamlined, cylindrical airframe. One engine was installed at the nose in a traditional "puller" arrangement and the other was fitted in the aft section of the fuselage in a "pusher" arrangement (behind the pilot's position). This combination of power made the Do 335 the fastest German prop-driven aircraft of the war but delays in acquiring the necessary engines led to fewer than forty examples delivered before the end of the conflict in Europe in May of 1945.
In the Do 335 "Zwilling" design, designated as Do 635, the aircraft was to retain the services of all four engines in their respective locations about the airframes. Each engine outputted 1,777 horsepower for a combined output of 7,108 horsepower. A crew of two was natural as each airframe was designed to hold one under their respective framed canopies. The combined fuselages generated a wingspan of 90 feet but more or less retained the same overall length (45.4 feet) and height (16.4 feet) of the original heavy fighter. Gross weight was estimated to be 72,532 pounds and performance specs included a top speed of 447 miles per hour with an impressive range out to 4,722 miles.