About 27,000 federal employes classified as "special-rate" workers, most of them engineers and medical personnel, would get pay raises next year ranging from 2 to 15 percent under a proposal from the Office of Personnel Management.

Right now there are 39,000 civil servants who, because their jobs are hard to fill, are paid more than civil servants in the same grades in other occupations. OPM controls the salaries of that classification.

The increase OPM is proposing would have no effect on salaries paid most of the government's 1.4 million white-collar civil servants. Their basic pay rate has been frozen by the White House and Congress. Although those civil servants may still qualify for longevity raises and promotions that would give them pay raises, they cannot get a general pay increase until January 1987 under the terms of the freeze.

OPM advised federal agencies last month that it was planning to authorize the raises for most of the special-rate workers. It asked for agency comments, and that comment period ended yesterday. A decision on the raises for the special rate employes is expected within a few weeks.

The government has authority to pay special rates to employes to make Uncle Sam more competitive with the private sector.

In some cases, OPM has authorized the special rates for entire occupational groups. In others, the higher salaries are limited to employes in high-cost cities or remote areas where the government has a recruiting problem.

Most of the special-rate employes are in Grades 5 through 13. Depending on their jobs and rates, they are paid from several hundred to several thousand dollars a year more than regular civil servants in the same grades.

Each year OPM makes a survey to learn what kind of pay raise, if any, is necessary to keep the government competitive. Last year more than half of the special-rate workers got pay raises.