When William Spang steps down later this year as an assistant to the vice chairman of the Federal Reserve Board, he will return to the private sector with more than just firsthand knowledge of U.S. monetary policy and banking regulation.

The 33-year-old accountant says he also will leave the government with a greater appreciation for career federal managers than most of his private counterparts have.

Since last October, Spang has participated in a program, under the auspices of the President's Commission on Executive Exchange, that allows managers in private industry and government to swap places for a year.

"It gives the industry person and the federal person a chance to walk a mile in each other's moccasins," said Elizabeth Lucas-Stephens, who has worked this year as an aide to an administrator of the General Services Administration, evaluating telecommunications systems.

Originally geared toward young managers, the 16-year-old program is now open to executives young and old, provided they are "exceptional managers with unique qualifications and extremely high potential for policy-making positions."

This year, the program placed 10 federal executives in private jobs and 29 managers from the private sector in government jobs. The firms pay the commission $15,000 for each employe who participates, while agencies pay $3,000 for each of their employes. The agency or firm that employs the person for the year pays his salary, up to the Civil Service maximum.

The private-sector managers participate throughout the year in seminars with agency heads, members of Congress and other figures. Participants say the highlight of these is a trip to Europe in which both the private and public managers meet with national leaders there.

Spang said he believed that spending a year with the government turned out to be more useful than going back to school for an advanced degree or attending an executive seminar. "It is the experience factor, the hands-on dealing with the day-to-day decision-making policy that you can't get in a university setting," he said.

"While here at the Federal Reserve, I am giving input as well as receiving feedback, so it is a two-way street. The Fed benefits by my suggestions and ideas, and personally, I learn from being part of the decision-making process."

Virtually all of the past and present participants who were interviewed had favorable opinions of the program. One recent alumnus, however, had reservations.

"I don't want to be in a position to dump on this program . . . but many of these guys end up with rather menial jobs," said the participant, who asked not to be identified because the head of his company serves on the commission that guides the program. "An agency takes them in and gives them a desk and a phone but no input. The attrition rate was quite high the year I was in the program . . . . They just weren't challenged."

"Imagine you are a bureaucrat," he said, "and you are assigned someone who has never worked in government before. The bureaucracy has a tendency of rejecting folks who are interlopers. These guys are assigned to guys who really aren't their bosses."

Linda Long, a Chevron Corp. employe now working as an assistant to NASA's associate administrator for external affairs, said it took her about two months to get to know her coworkers and earn their respect. "I had to earn my spurs. I appreciate what they have done to help me learn the system."

Long, who used to direct a political-action committee and state lobbying affairs for Gulf Oil, said because of personnel cuts, the reaction from some of her coworkers "was 'what are you doing bringing this woman in here from the outside who doesn't know anything about our business when we need secretaries and other professionals?' "

The flip side of the program involves federal employes taking private-sector jobs for a year. For instance, Norman Achilles, a 22-year veteran of the State Department, was assigned last year to a job advising the senior management of IBM's American Far East Corp. Because Achilles had served in the economic division of the U.S. Embassy in Japan for seven years and had worked with IBM executives before, the company expressed interest in him after he was selected to participate in the program.

During his time with the firm, he advised senior managers on issues involving Japan. He said his participation had been useful to IBM because he could help his coworkers understand how the State Department operates. "For historical reasons, we (government and business) have had adversarial relations. That's why we suffer in facing foreign countries."

To prevent participants from using the program to shop for a new job, government employes must return to their agencies for at least three years, while private employes must return for at least one year.

Most private sector executives said they were unaware that the exchange program existed before their selection. In most cases, executives were nominated by their company's senior management.

And this government-sanctioned revolving door often helps provide a step up the corporate ladder for its participants. Spang, who has been with the accounting firm of Arthur Young and Co. for the past 11 years, is optimistic that he will be made a partner soon after his government assignment is up this fall.

And when Lucas-Stephens, an engineer, returns to United Technologies Corp., she expects to be promoted to a senior management post. "The program has helped me to personally see how a large complex organization works and works well. I will be able to use that."

Stephen Murphy, a vice president and regional manager of Bank of America, who has spent the past year at the Health and Human Services Department, said although he doesn't expect a promotion, his year in Washington could help his career: Samuel Armacost, who preceded Murphy in the program, is now president and chief executive officer of Bank of America.