Jetrader - Autumn 2018 - 55

SAN DIEGO AIR & SPACE MUSEUM

of 230 feet. Both aircraft would be powered by piston engines buried in the wings,
driving pusher propellers; there would be
four engines in the Northrop B-35 and six
in the Convair B-36.
Jack Northrop was a highly respected
aeronautical engineer, whose career
spanned from 1926 until his death in 1981.
He had worked for Douglas twice, Lockheed
twice, and was the chief engineer on the
Lockheed Vega family of aircraft described
in the Winter 2015 Jetrader, which can be
found in the archives on the ISTAT website.
Mr. Northrop eventually formed his own
company, Northrop Corporation, in 1939,
based in Hawthorne, California.
While his company manufactured a number of conventional aircraft, Jack Northrop
also developed several tailless designs.
He argued that with the elimination of
the fuselage and tail surfaces, and with
engines buried inside the wing, an aircraft would have greatly reduced drag and
would also be lighter. The expected result
would be a design that carried greater payload while flying faster and farther than
conventional designs.
In November 1941, only a month before
the Japanese attack on Pearl Harbor, the
U.S. Army Air Forces ordered Northrop to
build two flying-wing XB-35 prototypes,
with preliminary design work to begin
in early 1942. Subsequently, a Letter of
Intent was issued for the production of
200 B-35s. Northrop's factory in Hawthorne
was already filled to capacity manufacturing fighter aircraft, so the Glenn L.
Martin bomber factory in Omaha, Nebraska,
would be responsible for the mass production of the Flying Wing Bomber, with
engineering assistance provided by Otis
Elevator Company.
By January of 1943, the Northrop home
facility had been expanded and production
of the two XB-35 prototypes was begun
there, with plans for an initial batch of 13 to
follow. These were designated YB-35s. In
addition, the Army Air Forces had approved
Northrop to build four, 1/3-scale versions
to be used for aerodynamic research and as
pilot trainers. They were designated N-9M,
short for "Northrop's Ninth Model." All four

One of the first two piston-powered Northrop XB-35 Flying Wing Bombers in flight. The bulges
on the top surface of the wings outboard of the engines simulated remote-controlled machine
gun positions. Similar "blisters" were also on the bottom side. The chase plane is another
Northrop design: the P-61 Black Widow night-fighter.

N-9Ms were completed and flown, although
one crashed, and its pilot was killed while
exploring stability and control in aft center
of gravity testing.
With the U.S. fully committed to the war,
progress on the big Northrop flying-wing
project was slower than expected. Manpower
was a continual problem as many designers
and engineers were being drafted into the
armed forces or volunteering. And to make
things worse, engines with the eight-blade,
coaxial, counter-rotating propellers and gear
boxes, developed by Pratt & Whitney and
delivered to Northrop as government-provided material, were always troublesome
and running behind schedule. Consequently,
the war ended before the two full-scale prototypes were ready to fly. By then, Martin's
200-unit mass production program in
Nebraska was cancelled before it started.

Post-War Developments
The first of the two XB-35 prototypes
flew in June 1946, followed by the second one a year later. Both maiden flights
were from the Hawthorne factory to the
Muroc Army Air Base in the Mojave Desert.
By then, with the war over, everything
had changed. While the first Convair

B-36s also hadn't flown until 1946, these
long-range bombers did go into production, with 385 of them being produced
between 1948 and 1954. Also, jet-propelled
medium bombers and jet fighters were
quickly superseding the earlier piston aircraft; the future of the piston-powered
Northrop B-35s became precarious.

Jet Propulsion to the Rescue
Having foreseen the obsolescence of the
piston-powered B-35s, in January 1945 Jack
Northrop had recommended that future
models be jet-powered. Not only were
the jet engines much simpler than piston
engines to build, Northrop would no longer
need to deal with the unreliable, complex
gearboxes and coaxial propellers.
Two of the 13 huge YB-35s already in
production were fitted with eight jet
engines in place of their four sets of
piston-powered propellers. These former YB-35s were designated as YB-49s,
and the first of the pair was flown to
Muroc in October 1947, which was only
about four months after the second piston-powered XB-35 arrived. As expected,
the jet-propelled YB-49s were faster than
the piston-powered YB-35s, but the early
Jetrader * Autumn 2018 55

Jetrader - Autumn 2018

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