Jos Heyman said:When you are talking about the 6 engined version of the XB-19, you are really talking about the XBLR-2.
Ordered on 9 July 1935 as XBLR-2, the design had initially 6 engines. In March 1938, by which time the design had evolved into a 4 engined aircraft, the designation was changed to XB-19. At that time no aircraft had yet been ordered. The 3-view is believed to be the XBLR-2. I do not know the source of this.
frank said:A bomber development of the DC-4E?
[It] retained the wing, powerplant installation and undercarriage of the American transport, but featured a new fuselage with glazed nose and ventral bomb-bay, new tail surfaces with twin fins and rudders, and was powered by four 1,870 hp Nakajima NK7A Mamoru 11 fourteen-cylinder radials.
Pica said:DC4E was developed into the Nakajima G5N Shinzan, I found a picture on http://en.wikipedia.org/wiki/Nakajima_G5N
According to René J, Francillon, Japanese Aircraft of the Pacific War, p. 423-425 six were built. Being overweight and fitted with unreliable engines they were not much of a success. Two G5N1s and the two G5N2s were converted to transports.[It] retained the wing, powerplant installation and undercarriage of the American transport, but featured a new fuselage with glazed nose and ventral bomb-bay, new tail surfaces with twin fins and rudders, and was powered by four 1,870 hp Nakajima NK7A Mamoru 11 fourteen-cylinder radials.
XB-70 Guy said:I'm with the understanding that the XBLR-1 became the XB-15, XBLR-2 the XB-19, and that the XBLR-3 was an offering from Sikorsky that was never proceeded with... -SP
Jos Heyman said:On 28 June 1934 a contract was placed for one XBLR-1 with serial 35-277. On 29 June 1935, and prior to the first flight of the aircraft, the designation was changed to XB-15. It is not clear if the XBLR-1 design was exactly the same as XB-15.
Jos Heyman said:Also known as project M5-35, a design for the XBLR-3 was submitted on 29 February 1936 whilst a wooden mock up was built in March 1936. The design was rejected in favour of the BLR-2. No aircraft were ordered.
Jos Heyman said:It has been suggested that the XBLR-4 designation was associated with the Martin 145 model that was re-designated as B-16 before the XBLR-4 designation was assigned.
Pica said:Both designs show obvious Douglas-features, but in my opininion this is more likely to stem from parallel development in a common environment rather than one design (XB-19) being derived from the other (DC-4E).
Francillon does not mention any six-engined XBLR-2 design, I was pleasantly surprised by the drawing.Finally, as funds were made available, construction of a prototype - now re-designated XB-19 - was authorized on 8 March, 1938.
Jos Heyman said:Sources for this? No idea. I have collected data over the past 45 years of all US military aircraft and did not and can not afford the storage space for all detailed references. Be assured that 'weird data' (such as the suggested XBLR-4) is labelled as such in my files.
lark said:...Douglas recommend on 30August 1938 to abandon the program for the benefit
of a less complex machine,the DB-4,derived from the first DC-4,the one with the 3tailfins
who would become the DC-4E. The Material Division opposed because the Army Air Corps
wanted the first machine as a flying testbank...
So far :Rene J.Francillon.
This is the book's caption of the picture I posted:The Martin Model 145, a very long-range bomber projected in 1936 as the XB-16, was initially similar to Boeing's XB-15; both were designed for four Allison V-1710 liquid-cooled engines. The XB-16's wingspan was to be 140 feet and the loaded weight 65,000 pounds. The following year Martin proposed the Model 145A, a most unconventional six-engine bomber with twin booms, a span of 173 feet and a weight of more than 100,000 pounds. It was expected to attain 256 mph. Neither design went past the drawing stage, although the Air Corps purchased the engineering data and later publicized a four-engine version of the 145A as one of its "Airplanes of the Future".
... so I understand the picture was produced by the Air Corps, not by Martin.This "4-engine bomber of the future" was based on the second XB-16 design, which had six engines rather than the nacelle guns shown.