Blue-collar federal workers in Wichita, Kan., (with a little help from Republican Sen. Nancy Kassebaum) have blown a very big hole in President Reagan's otherwise successful attempt to limit fiscal 1982 federal pay raises to 4.8 percent.

Thanks to special language in the Defense money package--put there by the junior senator from the Sunflower State--the 560-plus government carpenters, mechanics and laborers in greater Wichita will be getting raises averaging 28 percent--up to $4,700 a year--while their counterparts in Washington, San Francisco, New York and other high-cost areas make do with a 4.8 percent adjustment.

Last Oct. 1, Reagan put a 4.8 percent limit on pay raises for the government's million-plus white-collar civilians. Congress followed suit by limiting catch-up-with-industry raises for 400,000 blue-collar workers nationwide (about 21,000 in the Washington area) to the same amount on grounds that government pay is pretty good, and the nation simply couldn't afford more.

But Sen. Kassebaum--whose state has some major aircraft manufacturers--got a lot of heat from her blue-collar federal employe constitutents who said they were paid peanuts compared with welders at Boeing and specialists with Cessna. Kassebaum said she would see what she could do. What she did was persuade Senate colleagues to make Wichita feds a special case, and exempt them from the 4.8 percent pay cap.

Hardly anybody noticed it at the time. But the bill has come due now that the Defense Department (grumbling all the way because of the precedent this could set) has announced (as quietly as possible) new pay schedules for the wage board (blue-collar) people in Wichita. It is waiting for the heat--which ought to be intense--when government workers in other parts of the country, and white-collar feds in Wichita for that matter, find out what has happened.