Jetrader - Summer 2018 - 50

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Martin XB-48 prototype.

the first to go supersonic, but it had straight, unswept wings.
Perhaps that was still the better way forward. Only flight testing
of Boeing's new bomber would settle the question.
The first XB-47 was rolled out in September 1947 and in December
made its first flight, taking off from Boeing Field in Seattle. From
earlier engine test runs, Boeing knew the six-engine takeoff would
cause probably the most horrendous noise ever heard in Seattle, so
the landing was made at the Moses Lake Air Force Base in central
Washington State where much of Boeing's test flying took place and
where noise was likely to be less troublesome. It was said that the
B-47's engines achieved the direct conversion of jet fuel into decibels.
To placate the neighbors, only a small number of B-47s were manufactured at Boeing Field, and most of them made the same one-time
maiden flight to Moses Lake to get out of Seattle and never came back.
Overall, not counting the two XB-47 prototypes, the production
run eventually amounted to 2,030 Stratojets. Most of Boeing's
production of B-47s took place at Wichita, Kansas, in the factory
where Boeing had produced many B-29s during the war, and several hundred of the B-47s were also manufactured under license
by Douglas and Lockheed. Besides the nuclear bomber versions,
a large number were used for weather research as well as photographic and electronic reconnaissance around the perimeter for
the Soviet Union.

The B-47's Unique Features
and Design Compromises

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In the interest of speed, the B-47's wings were very thin, so
fuel had to be carried in the fuselage or in drop tanks under each
wing. There was also no room in the wings for landing gear, so a
bicycle configuration was adopted with the main wheels in pairs
in the forward and aft fuselage and small wheels on outrigger
struts that retracted into the engine pods.
With the bicycle landing gear arrangement, it was not possible
to rotate the nose so it could be raised for takeoff, so when the
B-47 rested on the ground it sat nose-high and tail-low at just
the right angle for taking off. Landing was also touchy because
the touchdown had to be made at that same body angle to avoid
porpoising or slamming down on the nose or tail at any other angle.
The original General Electric engines were rated to only 3,750
pounds, so the B-47 was sluggish on takeoff, and without speed
brakes it was fast on landing. For some missions JATO rockets
provided boost for takeoffs, and a drogue parachute helped to
slow the landing touchdown.
The B-47 also pioneered fully powered, irreversible controls
with manual reversion, a system used on the Boeing 727 some
15 years later. At the same time, a full-time yaw damper device

50 The official publication of the International Society 30/12/17
of Transport
Aircraft Trading
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Jetrader - Summer 2018

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