Final Test for B-2 Also the Costliest: Break One : Aerospace: Engineers will use hydraulic jacks to snap the wings off the most expensive plane ever built.
In the costliest industrial test in history, Northrop engineers were preparing Tuesday to break the wings off one of the firm’s B-2 Stealth bombers.
Northrop and its subcontractors loaded one of the bat-wing bombers into a huge iron test rig in Palmdale, where 200 massive hydraulic jacks will exert tons of pressure on the B-2’s wings to determine their breaking point.
Afterward, the crippled aircraft will be branded with red paint and relegated to a “boneyard” for grounded airplanes.
The Stealth bomber slated for destruction cost less than the average model--it does not have engines, wiring or electronic systems, but is complete in every other way. B-2s cost $2.4 billion each, including the program’s research and development, and $1.1 billion excluding those charges. Northrop officials declined to say how much the actual test costs to perform.
The test is a crucial milestone in the use of reinforced plastic composites for advanced aircraft, a technology in which the B-2 has played a pioneering role during the 1980s and which is now spreading rapidly into commercial aircraft, said Jorge Diaz, Northrop’s deputy program manager for the B-2.
Diaz recalled that when Northrop began B-2 development in 1981, knowledge about designing and building aircraft with composite materials was still crude and engineers were “biting their nails” over the risks.
The controversial nuclear bomber is the first large aircraft whose primary structure contains more than 50% fiber-reinforced plastics. The materials were selected to help the aircraft operate undetected by enemy radars and to reduce its weight.
Aircraft technology is typically pioneered on military jets and later used in commercial aircraft. Boeing, a B-2 subcontractor, will use composite plastics for the floor beams, horizontal tail and vertical tail on its new 777 jetliner, representing about 10% of the aircraft’s structural weight. While that is far short of the 50% usage on the B-2, it is up from 3% composites on prior Boeing jets.
“We had a big switch from wood to metal construction in the 1930s, and now we are at the same stage with composites,” said Wolfgang Kanauss, a Caltech aeronautics expert. “This is a big advance.”
The test to break the B-2’s wings, which is being conducted by Lockheed under subcontract to Northrop, is the last of a series of required government tests that began in October, 1989.
The B-2 passed the prior tests two months ahead of schedule, showing that the aircraft can withstand 150% of the most severe expected flight conditions, and that it can withstand twice the expected stresses that will accumulate over its projected 20-year lifetime.
Andy Anderson, Northrop manager for structures technology, said the aircraft passed the tests without any failures of primary structures, the parts that bear the flying loads. Minor cracks and other damage did occur on fasteners, brackets and clips, he said.
Still, that is a stark contrast to the McDonnell Douglas C-17 cargo jet, which has met with several serious structural failures during testing. Most recently, the wings broke well short of requirements.
As a final test of the B-2, engineers want to see how much margin above 150% the aircraft has. If the wings stand up to even higher loads, the aircraft may eventually be able to carry more weight or perform more stressful maneuvers, Diaz said.
In past tests in which aircraft are broken, pieces have been known to shoot through the roof, Anderson said. In the B-2 test, engineers will be safely shielded by a ballistic curtain and a cinder-block wall.
