More than 16,000 career federal executives, most of them based in the Washington area, are scheduled to get catch-up raises this October ranging from $6,000 to $8,000 in addition to the 4 percent increase President Reagan has approved for other federal workers.

But Congress probably will pull the rug out from under the career U.S. officials whose pay is capped at $57,500 and $58,500. They will be lucky if they get the same 4 percent as their subordinates.

Last year Congress approved a change in the executive-legislative pay mechanism that would give members of Congress the same percentage raise this year as rank-and-file civil servants. In addition, the package deal would allow senior executives to receive raises that have been denied them the past several years, plus the same raise as the rank-and-file receive.

Congress made the pay catch-ups automatic -- small ones for members, bigger ones for U.S. executives -- hoping to avoid the usual fights that top pay boosts always produce.

Under the automatic provision, the pay cap for GS (general schedule) civil servants would rise $6,330 from its current ceiling of $57,500. Members of the Senior Executive Service (most of them now capped at $58,500) would get a raise of $8,770 automatically. Both groups would also get the 4 percent general pay raise due other workers this fall.

But the automatic-pilot provisions of the pay plan got shaky as the economy faltered, and as the election got closer. Last month Congress threw up its hands in horror at a separate, unrelated plan to give members (who get $60,662) relatively modest increases to be set by President Reagan based on recommendations from an outside panel of blue-ribbon pay experts.

That action almost certainly set the stage for someone in Congress to step in now and upset the entire automatic pay package, and undo everything the Senate and House tried to do last year when they prepared for what they hoped would be quick, quiet, noncontroversial adjustments this year.

Key Reagan officials would dearly love to see an executive pay raise this year. Many of them are shocked by the government's top pay rates, and the difficulties they have had in hiring and keeping people they want. In many agencies the low (by industry standards) executive salaries have attracted many young (bright but inexperienced) helpers, not the seasoned executives the administration hoped to bring in for second- and third-tier jobs in government.

Backers of the executive pay raise say the less said about it the better. Some hope that lack of publicity about the impending raises will allow them to go into effect without a fight. But that isn't a very realistic reading of the situation.

Members of Congress know about the "sleeper" in the pay law, and they know they will have to deal with it. Many have said, privately, that they would support a modest catch-up, or at least a 4 percent raise for executives, if the Reagan administration will take the lead.

If the president comes out for some kind of executive pay raise -- and perhaps an increase to be effective next year for the new Congress -- a 4 percent adjustment is possible. However, barring strong White House support -- or perhaps a kind word from a cabinet officer speaking for the president--those big executive raises are bound to be shot down at the last minute, automatic pilot notwithstanding.