The Fairfax County Board of Supervisors supported yesterday the proposed financial plans for completing the full 101-mile Metro subway system with the condition that Metro raise subway fares commensurate with cost-of-living increases.

The board adopted a position paper on Metro by an 8-to-1 vote, with Supervisor Audrey Moore (D-Annandale) voting against the financial plan. She supported the provision that Metro raise subway fares to meet inflationary costs.

In the paper, the board said its support is contingent upon:

Approval by Fairfax County voters of bond sales and/or appropriation of state aid to meet all additional construction contributions in the financial plan, which calls for the county to pay $52 million as its share of completing the system.

The federal government supplying at least 80 percent of additional funds needed to complete the system.

Completion of the Metro subway stations planned for the county.

Metro considering accelerated construction of the parking lot at the Vienna subway station.

In adopting the position paper, several of the supervisors expressed dissatisfaction with the rising Metrorail and Metrobus operating subsidies.

Board Chairman John Herrity (R) said the county ought to explore operating its own bus system.

All Washington area local governments except those of Prince George's County and the District of Columbia, have now formally voted to support the metro financial plan, according to Metro General Manager, Theodore C. Lutz, who attended yesterday's board meeting.

In another action, the Board defered until Feb. 12 a hearing on a proposal to construct a 240-foot-tall microwave tower inthe Franconia area.