The B-2 development program was initiated in 1981, and the Air Force was granted approval in 1987 to begin procurement of 132 operational B-2 aircraft, principally for strategic bombing missions. With the demise of the Soviet Union, the emphasis of B-2 development was changed to conventional operations and the number was reduced to 20 operational aircraft, plus 1 test aircraft that was not planned to be upgraded to an operational configuration. Production of these aircraft was concurrent with development and testing.
Although the B-2's flying wing outline seems unusual today, aeronautical engineers have long known about the potential advantages of the basic design. As far back as World War I, all-wing airplanes were highly regarded as being stable and forgiving in the air-too stable, as it turned out, to make a good warplane. Engineers like John Northrop knew that such a design, not needing a conventional fuselage and tail assembly, would produce much less drag as it moved through the air. The air resistance thus saved could in turn be traded for significant advantages: higher speed, or the ability to carry a greater load at much greater ranges. There were other benefits as well. With no need to confine most of the payload within a narrow and heavily-stressed fuselage, that weight can be evenly distributed across most of the lifting surface, resulting in a lighter and more efficient structure. Northrop devoted much of his career to proving that the all-wing concept could be used in a practical aircraft.
The Northrop Aircraft Company's XB-35 Flying Wing bomber, powered by four Pratt and Whitney Wasp reciprocating engines driving eight contra-rotating propellers, made its first appearance in 1946. Plagued with engine and gearbox problems, the design was adapted for jet power and the eight-jet YB-49 took to the air on 21 October 1947. In the months that followed, a strange anomaly was noticed as the big plane flew about the country: it was often hard to see in the air, and under some conditions it nearly disappeared from the radar screens of the day. For a number of reasons, the YB-49 never went into production. Too advanced to be effectively maneuvered by the control systems of their day, the giant wings nevertheless went a long way toward validating Jack Northrop's faith in the basic design. Other planes were selected for operational use by the Air Force, however, and the flying wing concept was relegated to the future.
Designing a new warplane became far more than a matter of developing a new and improved airframe. The systems approach meant that new weapons suites and swiftly-evolving electronic capabilities had to be blended into an integrated design in order to end up with an airplane capable of doing numerous complex tasks well. The use of lightweight composite materials was also becoming common, and new electronic flight controls meant that long-known aerodynamic concepts were on the verge of becoming practical.
By the 1970s, yet another factor was coming into play: stealth technology. This promised to make an airplane hard for an enemy to detect, and even harder to attack. The new airplane, soon to become known as the Advanced Technology Bomber (ATB) would have to cope with an exacting set of requirements in order to survive in future combat scenarios. Along with its radar-deflecting shape, it would have to have a low infrared signature in order to evade heat-seeking missiles, and to carry a sophisticated electronic suite. It would resist detection by visual and acoustical means as well as by enemy radar. With massed bomber attacks a thing of the past, the ATB would have to be capable of carrying out its mission alone and without fighter escort: one airplane, carrying out precision attacks, in the absence of many.
And, of course, the new design would also have to be aerodynamically efficient in order to carry a meaningful payload over intercontinental ranges. With all of these demanding constraints in mind, it was perhaps inevitable that Northrop designers would call to mind the sleek all-wing monsters of the past.
The sophistication of the electronic flight control system, mated to the excellent flight dynamics of the basic airframe, resulted in an airplane which was especially easy to fly. Most pilots say that you cannot tell you are in a flying wing, there is no sensation of the unusual, and you forget that you are in a short-coupled aircraft with no tail. One pilot described it as a "real feet-on-the-floor airplane," with controls so well harmonised that there was no need for continual rudder inputs during in-flight maneuvers. According to another pilot, "You put the nose right where you want it, and it stays there-there's no hunting, or oscillating, or overshooting like when you are refuelling a B-52. You don't have to fight with this plane."
More was involved here than just pilot convenience. A pilot who is struggling to anticipate what his plane will do, and to take corrective action before it responds, has little enough attention left over for emergencies, or for mission requirements. Bombers, by definition, fly very long missions and potential combat scenarios projected B-2 missions of up to 36 hours duration (later increased to 40, with a 50 hour mission tested in simulator). That is asking a lot from only two pilots. Another pilot maintains that the B-2 flies much like the C-141. "You know that you are in a heavy aircraft, but it is responsive. It has a real good roll rate, but of course you aren't allowed to try the manoeuvres that a fighter can," he said.
The flying wing reserves its most startling effect for when it is landing. As soon as that huge wing area snuggles down into ground effect, it wants to float along a cushion of air. "Your first couple of landings are always a thousand feet or so too long. You have to nudge the stick a little to make it settle. It's almost a 'push to flare' airplane. But its easy-the only plane easier to land is the F-15." People who fly the jet give most of the credit to the flight control system.
Fly-by-wire means that you are flying the computers (four of them, in this case), not the control surfaces themselves. Quadruple redundancy means that, in effect, the four computers "vote" on the result of any given control input by the pilot. At least three must agree, and any anomaly is automatically thrown out. The beauty of a system like this is that all sorts of conditions and compensations can be programmed in. For example, the B-2's bomb doors set up a huge amount of drag when they are opened. When a heavy bomb load is dropped, the plane will want to jump, yet the flight controls automatically compensate for both of these effects, and the pilot has only to operate the throttle. Similarly, the high-tech automatic pilot is theoretically capable of flying an entire mission profile, from takeoff to landing, with the pilot only providing the necessary power settings.
The first B-2 was publicly displayed on 22 November 1988, when it was rolled out of its hangar at Air Force Plant 42, Palmdale, California. The heavy force-projection aircraft was designed from the outset to be hard for an enemy to detect. Its smooth and rounded surfaces contrasted strongly with Lockheed's angular F-117, whose first photo had been released to the public only 12 days earlier. The bomber's design, in fact, demonstrated an advanced approach to low-observable technology.
A Northrop electrical engineer named Fred Oshira had first developed a "Source Distribution Technique" to predict the radar cross-sections of complex three-dimensional surfaces in 1963. It took a number of years to translate the new principle into the computer programs which could fully utilise them, but the result was an entirely new method for working with complicated curved surfaces. The electronic data base not only replaced conventional two-dimensional drawings, but could be encrypted and conveniently accessed by design teams at far-flung locations. Thus, engineers at Boeing in Seattle, Washington and LTV in Dallas, Texas, could easily work together to design the B-2's revolutionary airframe. The database also permitted engineering changes to be incorporated much faster, and, as a bonus, the precise geometry and parts measurements also allowed production tooling and inventory to be developed faster and with greater accuracy.
Not only was the bomber's basic shape inherently stealthy, but its smooth lifting surfaces had an excellent lift factor. Its lift-over-drag ratio, which approached that of the U-2 reconnaissance aircraft, could be translated into efficient long-range operation. The quadruple-redundant fly-by-wire flight control layout was teamed with a sophisticated air data system to eliminate the stability and control problems which plagued the large flying wings of the past.
Flight controls located on the trailing edge duplicated the functions of ailerons, elevators and rudders on conventional aircraft. Flaps on the wing tips were designed to open like dive brakes whenever the pilot inputs a course change, causing the big jet to pivot and change direction as needed. A "beaver tail" flap provided trim for the pitch axis and helped alleviate wind gust effects.
The B-2's first flight was July 17, 1989. The B-2 Combined Test Force, Air Force Flight Test Center, Edwards Air Force Base, California, was responsible for flight testing the engineering, manufacturing and development aircraft as they were produced. Three of the six developmental aircraft delivered at Edwards continued flight testing.
Whiteman AFB, Missouri, has been the B-2's only operational base. The first aircraft, Spirit of Missouri, was delivered on 17 December 1993. Depot maintenance responsibility for the B-2 was performed by Air Force contractor support and was managed at the Oklahoma City Air Logistics Center at Tinker AFB, Oklahoma.