Northrop XB-35
In the darkest days of World War II, when it appeared that Nazi Germany might well conquer Great Britain and the Soviet Union, the Army Air Forces saw the need for a large bomber with intercontinental range. Such a plane, based in the United States, must be able to cross the Atlantic and hit Germany with a large bomb load. Jack Northrop saw this formidable requirement as made-to-order for his flying wing concept. Only a flying wing, freed of the weight and drag of a conventional fuselage and tail, could have the performance necessary to meet that need. Northrop began work on a full-scale version of his earlier designs. At about the same time, the rival Consolidated Aircraft Corporation began work on its own design, destined to become the Convair B-36.
Jack Northrop’s XB-35 was a marvelous aircraft. Required to carry a 10,000-pound bomb load a distance of 10,000 miles, the futuristic plane was huge for its day: with a wing span of 172 feet and a length of only 53 feet, it stood 20 feet off the ground.
The Northrop plant was too small to build these airframes indoors so most of the manufacturing happened outside if at all possible
Its dramatically-swept shape (the same span and degree of sweepback of today’s B-2 bomber) was thrilling to see in the skies, particularly to a generation raised on aircraft of the 1930s and '40s. Seen from the side, it resembled a silver teardrop; viewed directly from the front, it nearly disappeared.
Four Pratt & Whitney R-4360 engines mounted internally, close to the leading edge. Each engine drove a pair of counter-rotating four-bladed propellers by means of a long extension shaft and a complex gearbox. Engines roaring and propellers churning, the bomber was a majestic sight in the air, but the complicated drive train proved to be its undoing.
The XB-35’s first flight, on June 25, 1946, was a success and Max Stanley later said that he would never have known that he was piloting a flying wing if he hadn’t looked behind him.
But that was about the only trouble-free flight the bomber was ever to have. Numerous equipment failures had already delayed the plane’s development by more than a year, and a host of gearbox and drive train problems plagued the flight test program. Only three B-35s were completed (two X-model and one Y-), and they accumulated only a modest number of hours in the air. In order to save the program, the government ordered the remainder of the initial service test models to be converted to jet power.
Popular folklore among aviation enthusiasts holds that Northrop’s futuristic Flying Wing was a wonder plane which was smothered in its cradle — a jet-powered marvel of fantastic performance which could have revolutionized postwar aviation "if only" it had been given a fair chance.
Northrop YB-49
The fact that the plane was canceled amid rumors of high-level conspiracy, and replaced by the more conventional — if equally awesome — B-36, only added to the legend.
In point of fact, the YB-49 had great promise, but flight testing soon revealed that it also had a lot of things wrong with it.
Most prototypes do, particularly those designs that push hard against the boundaries of aeronautical possibilities. And it was certainly true that the concept of a jet powered flying wing offered many possibilities: increased range and speed for the same power; more efficient airframe; substantial weight-lifting capability; and smaller aircrew. Its payload could be distributed evenly along the entire span, eliminating heavy internal bracing. Similarly, bomb bays no longer had to be confined to a narrow fuselage tube, but could be spread across the underside of the wing. From a strictly design standpoint, these advantages are indisputable.
Convair B-36
Many of the YB-49’s problems lay in its engineering design, and the compromises necessary in converting a piston engine design to jet propulsion. The Flying Wing’s basic airfoil section might have been optimum for the XB-35, but was clearly inadequate for the higher speeds needed for a jet bomber. Thus, the YB-49 cruised nearly 100 mph slower than the XB-47. The XB-35 never achieved its hoped-for bomb load, and its jet derivative fared no better.
Even worse, the bomb bays were simply too small for the nuclear weapons of the day. The cockpit layout was horrible: the pilot had a one-man bubble affording good visibility, but it could not be opened. There were no ejection seats. To leave his position, the pilot had to rotate his seat 90 degrees, lower it several feet, and walk to a hatch 15 feet away. The co-pilot’s position was buried in the leading edge; he had a very poor view that prevented him from taking off or landing the aircraft.
The YB-49 had eight Allison J35-A-5 engines with 4000lbs of thrust each. Pilot's position was in the bubble canopy. He sat three feet higher than the copilot.
Some of these problems could have been corrected, but others could not be. The designers had not been able to anticipate the critical control requirements needed for a large all-wing airplane, especially for a system that could anticipate and correct problems before the pilot was aware of them. That, of course, would have to wait for the computer age. The Air Force’s flight evaluators soon found that the YB-49 was sloppy in turns, and took too long to steady up for an effective bombing run. Its 1940s control technology was inadequate to the big plane’s needs. Worse, it could not provide the necessary margin of flight safety.
YB-49 was 53 feet and one inch from nose to the vertical fin. Bomb load was 16,000lbs
Perhaps it is fair to say that Northrop’s design concepts were solid, but the means to implement them were still several decades away. The YB-49 was simply a generation ahead of its time.
Additional Sources:
www.kstope.ang.af.mil
www.check-six.com
home.att.net/~jbaugher2
www.yourzagi.com
www.globalaircraft.org
www.volny.cz
www.hobby.fbi.cz
www.pilotfriend.com
www.military.cz
1000aircraftphotos.com
www.fleetairarmarchive.net
