Members of the recently elected Fairfax County Board of Supervisors expect economic realities of the 1980s -- rather than their political philosophies -- to play the major role in board decisions during the coming years.

Members of the new County Board will be sworn in Dec. 31. They will include three new supervisors plus the six members who were reelected last fall.

Growth, which has been at the heart of many board controversies in the past, is already being controlled -- less by zoning decisions than by high interest rates which have tightened mortgage money and slowed construction.

Dwindling energy supplies are dictating new approaches to such political issues as school closings, which can result in increased busing and higher fuel costs. Supervisors also say the cost of gasoline and a lack of public transportation may dissuade people from moving to the outer areas of the county and reduce suburban sprawl.

Yet in spite of these economic pressures, the supervisors say they remain confident about their ability to get things done.

Buoyed perhaps by the enthusiasm of the three new members, some supervisors say this term will see them build more roads, reduce the county's dependence on real estate taxes and tighten the reins on the Fairfax school board.

Several supervisors speculate that before the decade is over Fairfax will convert from a county to a city form of government -- a move which would decrease Richmond's influence over Northern Virginia and invest local officials with more authority.

The addition of the three new board members -- Thomas M. Davis III (R-Mason), Sandra L. Duckworth (D-Mt. Vernon) and Nancy K. Falck (R-Dranesville -- moves the board from a predominately Democratic body to a board which has four Republican and five Democratic members. Members of the board, both new and old, agree that the new supervisors will bring to the board a dash of conservatism.

Returning supervisors are familiar with two of the new members because of their involvement in public life. Flack is a former school board member and Duckworth is one of the county's most influential Democrats. But Tom Davis remains relatively unknown. Several members say Davis, who favors tighter control over the schools, may emerge as the board's 1980 "maverick."

"The three new members are extraordinarily capable people," said board Chairman John F. Herrity. "They are certainly not wet behind the ears.

"In fact, they probaby are better prepared than any other group of new members were in the past."

Each new supervisor has targeted an issue of major importance based on calls from constituents and personal concerns.

Falck is looking at transportation, and Duckworth says renewal of the Rte. 1 corridor is of primary importance to her.

Perhaps the most controversial concern is Davis' issue -- school closings. In neighboring jurisdictions, no issue has been more hotly debated than school consolidation. Fairfax County school administrators began cluster studies this month that will allow citizens to play a part in deciding which schools should be closed.

Davis says he is "appalled" by the authority given to the county school board in closing schools and other matters and is spearheading a move among the supervisors to see that no schools are closed at the end of the year. a

"I've talked to several management consultants and to a person they feel you don't save any money closing schools," Davis says emphatically. Davis said he thinks he can get Duckworth, Joseph Alexander (D-Lee), Audrey Moore (D-Annandale) "and maybe a fifth and somehow we will try to lay down the law to the school board."

While more than half of the supervisors say they agree in principle with Davis, they point out that legaly the supervisors have little control over the school board.

One of the first items on the agenda in January is the mid-year budget review. It is one time during the year when supervisors reexamine the financial needs of the county and are able to take money from one program to fund another.

The county's 7,000 teachers are waiting to see if the controversial 1.85 percent increase in teachers' salaries, which was passed by the school board in October, will be funded by the new board. Most supervisors said they are pessimistic about finding the funds.

Alan Magazine (D-Mason) who is leaving the board, refused to speculate on the future of the 1980 Board of Supervisors: "I really don't have any comment. I don't think it would be appropriate for me as an outgoing member to prejuge the new board. They deserve a honeymoon period."