Uncle Sam's controversial merit pay system for managers and supervisors would be expanded to cover more people, and made more attractive for employes rated satisfactory or better and less so for U.S.-certified drones under a plan being quietly floated by the Defense Department.

Currently merit pay covers only supervisors and managers (about 60,000 here) in Grades 13, 14 and 15.

Under the DoD proposal, merit pay would cover all GS 13 through 15s in government, regardless of their job.

Defense's plan would restore regular within-grade (longevity) raises to merit pay folks, and make it possible for those with top marks to get annual lump sum cash "performance adjustments" or bonuses.

Persons under merit pay now get half of the regular October federal pay adjustment, even if their annual agency report cards give them the equivalent of Ds or Fs for performance.

The Defense proposal would make it possible for agencies to give zero increases to the relatively few Grade 13 ,14 and 15 workers who get less-than-satisfactory or unsatisfactory ratings each year.

The merit pay system set up by the Carter administration was designed to prod managers and supervisors to do their best. While other federal workers will get a 4 percent raise next month, managers and supervisors are guaranteed only 2 percent. Any additional amounts they get depends on performance ratings and the amount of money their agencies have available for merit raises.

In addition, supervisors and managers under merit pay -- there are nearly 150,000 nationwide -- do not get the regular longevity increases (which are worth 3 percent) that other employes get almost automatically. Those raises are due every one, two or three years, depending on the employe's time in grade.

Defense's proposal, which has been sent to the Office of Personnel Management for comment, would restore automatic in-grades to all merit pay people who get satisfactory or better ratings, and guarantee that anyone with those ratings would get the full October pay raise.

Employes who got better-than-satisfactory ratings would be eligible for lump sum payments over and above the regular raise.

The stick part of Defense's carrot-and-stick proposal would make it possible for agencies to deny pay raise to Grade 13, 14 or 15 personnel with poor ratings. Very few get poor ratings, but even those who are rated unsatisfactory by their agencies now get half the regular October pay raise.

The first merit pay raises were given out last year. Because of a last-minute dispute over how to handle the system, everybody got at least the minimum 4.8 percent raise. This year, OPM says, everyone covered by merit pay is guaranteed only 2 percent; more if they get good ratings.

Even employes who get larger percentage increases, based on top performance ratings, will have to forgo longevity raises again this year.

Reps. Steny Hoyer (D-Md.) and Frank Wolf (R-Va.) have both introduced bills to revise the merit pay system. Most employes covered by it were unhappy with the 1981 payouts, which, even if they got good marks, often did not make up for the value of longevity raises they are denied.

Because it has about half the federal civilian workforce (and about 70,000 of the area's 350,000 federal government employes), Defense has a lot of clout. Its merit pay proposal is expected to get support from other agencies that figure -- after last year's experience -- that almost anything is better than the present system. If the plan does pass muster at OPM and the White House, it would have to be cleared by Congress and could not go into effect until 1983 at the earliest.