When Boeing Co. beat out Lockheed Aircraft Corp. for the prize of building the U.S. supersonic jet transport, it was on the basis of a venturesome swing-wing concept that many aeronautical designers predicted would never work. Last week, 21 months and many millions later, the skeptics were proved right. Boeing is now scrapping its movable wing. To take its place, the company has decided on a stationary swept-back configuration that bears more than a passing resemblance to Lockheed's original "delta" wing design.
Beset by problems from its inception, the American SST will not go into service for at least two years after its originally scheduled takeoff date of mid-1974. Boeing, understandably red-faced, denies somewhat defensively that it has made a final decision. But the economics of its swing-wing B-2707 has forced the Seattle company to put practicality over pride. Although wind-tunnel tests showed that the movable wing could perform well aerodynamically, it developed an insuperable weight problem. Carrying the 313-passenger payload envisioned for it, the 375-ton swing-wing SST would have had about one-half of its planned range of 4,600 miles—meaning that it would have run out of fuel over the Atlantic on a flight from New York to Paris.
Less Time to Build. Boeing could see the difficulties coming. Even before President Johnson selected the company for the SST plum on New Year's Day of 1967, it had scrapped one movable wing design and substituted another. When new problems mounted, the company earlier this year ordered its engineers back to the drawing boards in an effort to salvage the original concept. Gradually, confided a Boeing executive, it became apparent that keeping the swing-wing would "reduce the payload to the point where the plane wouldn't be profitable."
Despite their basic similarity, Boeing's new SST design differs in some ways from the one advanced by Lockheed. Boeing's delta wing will not be swept back quite so dramatically as that of the Lockheed model, a fact that should make the B-2707 slightly more efficient at subsonic speeds, slightly less so at its maximum cruise speed of 1,800 m.p.h. And while Lockheed planned to build its plane without a horizontal tail, the Boeing version will have a relatively conventional tail configuration.
Even with its new model, Boeing will have to pare down the plane's passenger capacity to 250. That will still be a sufficient payload to make the plane profitable, however, and will enable the craft to achieve the designed range. The new version, employing the familiar fixed-wing concept, should also take less time to build. That is particularly important, since the slower (1,550 m.p.h.), delta-wing Anglo-French Concorde, a rival SST entry, is scheduled to make its first test flight this fall and start commercial service in mid-1971, five years earlier than the B-2707. Boeing's best hope at this stage is that if no more serious kinks develop, it may be able to accelerate its timetable. That way, at best, it could prevent the Concorde from getting an irreversible head start on the SST's global market.