The Air Force has dismissed ice buildup on the wings as the cause of a crash Nov. 17 of a B-1B bomber in South Dakota, and says there is no need to consider adding wing de-icing equipment to the long-range aircraft. ``We do not have any evidence that icing was a contributor to the B-1B crash at Ellsworth (Air Force Base),'' Pentagon spokesman Fred Hoffman said, downplaying a published report last week in the Chicago Tribune. The report said the B-1B ``may have been downed by excessive ice on its wings.'' Pentagon officials, speaking on condition they not be named, told The Associated Press on Tuesday that the ice detection system on the plane did not indicate the bomber had experienced a dangerous build-up of ice. ``There was some icing,'' one source said. ``There was ice on the wings of another B-1B that landed just before this one. But it wasn't a problem.'' ``Wing icing was not considered a potential problem when designing the aircraft and there never has been any operational evidence that wing icing is a problem,'' Hoffman added. ``We have no plans to study the addition of de-icing equipment,'' added Lt. Col. Rick Oborn, an Air Force officer and Pentagon spokesman. ``That hasn't even been considered.'' The $280 million B-1B, like many types of military aircraft, does not have any built-in de-icing equipment for its wings. It does, however, carry an anti-icing system for its four engines and an ice detection system for the wings. Capt. Jay DeFrank, an Air Force spokesman, said the rationale for leaving de-icing equipment off the B-1B was simple. ``The B-1B can fly at such high speeds at low altitude that it normally melts what would buildup on (the wings,)'' he said. ``And if you know you're facing icing conditions, you normally fly to another base or move to a different altitude. The plane has an ice detection system for the wings.'' The B-1B that crashed Nov. 17 was practicing instrument landing approaches. It was attempting to land shortly after another B-1B made a successful approach and for reasons unknown, came in too low and clipped a utility pole and power lines. The four crewmen survived after ejecting from the plane. In a related development, Hoffman said the Air Force would look into allegations by some Rockwell International Corp. employees that flawed parts might have been used in building the B-1B bombers. ``But the Air Force does not have any evidence at this time which corroborates the assertions by former Rockwell employees that substandard parts were used in the construction of B-1s,'' Hoffman said. ``However, the Air Force is investigating or is looking into these allegations.'' A copyright report Monday by WBNS-TV in Columbus, Ohio, quoted workers as saying substandard parts disappeared after being rejected by plant inspectors. The employees said they believe those parts subsequently were used in building the bombers to meet production schedules.