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sink-me
100-Ton Flying Wing
Under construction for three years, the XB-35 was designed so that all external
surfaces contribute to lifting it.
Outstrips B-29
By Leon Shloss and Andrew R. Boone
Efforts to make tailless aircraft prac-tical began the year before Orville Wright
was born. At least 40 pioneers, of nearly as many nationalities, have contributed
to the science. Now an American, John K. Northrop, has done it with the Army's XB-35
bomber.
This plane, weighing 89,000 pounds empty, under overload conditions will lift
60 tons of bombs, gas, crew and cargo. The 209,000-pound gross weight is 78,000
pounds more than that of the Boeing B-29 Superfortress. The boomerang-shaped wing
is 4,000 square feet in area, more than double the B-29's; hence the great lifting
power. Most parasite drag went out with the fuselage, and higher speed came in.
The speed figure is undisclosed, but it is known that the plane is expected to outfly
the fastest conventional fighters, which approach 500 m.p.h. Four Pratt & Whitney
3,000-hp. engines turn Hamilton Standard coaxial pusher propellers. Fifteen Flying
Wings have been ordered, with jet power in prospect for future models. The plane
will be shown about the time this story appears. First flight depends on progress
of pilots who are preparing to fly the radical giant. Complicating the problem was
the death of the outstanding Flying Wing test pilot, and the short, 5,700-foot runway
from which the first take-off must be made.
Artist's conception (above) shows XB-35 in flight over Los Angeles. To
the right you see open section of wing that may hold cargo.
Wing slots on the N9M, 60-foot scale-model forerunner of the XB-35, were
added to increase stability at low flying speeds. Control is achieved by slots,
wing rudder and tabs, plus Northrop "elevons," which function as combined ailerons
and elevators.
This pseudo Flying Wing of 1929, with 30-ft., 6 -in. wing span, contributed
a lot of data to the plans of the XB·35.
The N9M was the last of four 60-foot scale models used to predetermine
the flight characteristics of the XB-35.
Built by the Northrop Aircraft Co., at Inglewood, Calif., of a ware developed
aluminum alloy - 75-S - the XB-35 has a theoretical range of 10,000 miles - from
New Orleans to Singapore. Everything is carried within the wings including the engines,
excepting gun turrets and a pilot-canopy bubble. All external surfaces contribute
to lift. "Elevons" installed in the trailing wing edges combine the functions of
elevators and ailerons. Landing flaps, trim flaps and rudders are also in the trailing
edges. To move the controls the pilot uses a so-called "feel" system coupled to
a full hydraulic boost system. The "feel" applies varying pneumatic forces to the
control system at different speeds to hold control movements within safety limits.
Further control is achieved by automatically operated long wing slots paralleling
the leading wing edge. These slots assure continued smooth laminar airflow at near-stalling
speeds.
Militarily, the XB-35 enjoys the unprecedented advantage of comprehensive fire
power aft, thus removing the airplane's greatest combat vulnerability - the hard-to-defend
tail. It also presents a smaller target-and can carry the atom bomb, a chore performed
heretofore only by the B-29.
Other advantages listed by Northrop will apply to cargo as well as fighting editions:
Low drag, high lift allowing transport of any weight faster, farther and cheaper;
simple construction; more even distribution of weight; spanwise compartments that
accommodate rectangular packing cases more neatly and can be loaded or unloaded
more quickly and easily than tubular holds.
Several foreign designers have built tailless airplanes that flew well, but they
encountered engineering obstacles, which Northrop presumably has whipped. There
is a transition phase in take-off and landing during which a tailless plane may
be hard to control. The biggest engineering hurdle, however, has been the tendency
of tailless planes to flat-spin, followed by inability to nose down in order to
recover. Until the wing was made thick enough to enclose engines, crew, payload
- everything, in fact - there was little aerodynamic justification for such a plane.
And a wing that thick meant a plane far larger than could be economically justified.
Military need in World War II for mammoth planes, and the current postwar demand
for volume and global air transport, brought about a wing large enough to increase
chord (depth of wing) to the point where the nose will go down.
Another shortcoming was the inability of tailless planes to glide to safety in
case of engine failure. This was ironed out along with the original problem when,
in the '30s, aircraft engines became so dependable that failures became virtually
unknown.
A great obstacle to Flying Wing development has been the timidity of industry
to delve into types untraditional and therefore hard to sell. It has usually been
the unconservative boss of the small shop who has waded into the lists of radical
design. That describes 50-year-old Jack Northrop, who has been designing radical
airplanes for 30 years. His first model of the Flying Wing, with a wing span of
30 feet, six inches, had twin booms and a tail, and so was not a true Flying Wing.
The first true Wing was flown in 1940, utilizing drooped wing-tip controllers, which
Northrop proved successful by experimentation with paper models. This plane was
built of wood, easily adaptable to changes in design. General H. H. Arnold, later
head of the Army Air Forces, saw this plane fly and ordered developmental work begun
on a huge Flying Wing bomber from which grew the XB-35.
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