An Arlington citizens advisory committee, created two years ago to develop a cohesive policy to guide the county in its position on National Airport, found the task impossible and released two contradictory reports yesterday.

The committee, some of whose 12 members have long been vocal critics or boosters of the airport in Arlington, split into two subcommittees with two divergent 100-page reports.

Thomas H. Floyd Jr., the committee chairman, said yesterday that he was disappointed the committee did not reach a consensus, but that the reports reflect the feelings in the community.

"The committee was exceptionally representative of sentiments in Arlington," Floyd said. "There is a very wide divergence of opinion on this."

However, Floyd said, both subcommittees did agree on the need to reduce noise and improve safety.

In addition to noise and safety, each report focused on the economic impact of the airport on Arlington and problems arising from the antiquated road network and the physical condition of airline terminals.

The report from subcommittee A, which four members signed, is highly critical of the airport. In general, it advocates a gradual but significant reduction in daily flights and the annual ceiling on passengers and earlier night curfews for airplanes.

It also says the safety margin at National is "too narrow" and expresses skepticism that a shift of many of National operations to Dulles International would seriously affect Arlington's economy.

The report from subcommittee B, signed by six members, is generally supportive of National while recognizing the facility's many flaws, such as the airport's "deplorable and intolerable" ground facilities.

It contends the airport provides "indispensable" economic benefits to Arlington, that the airport on balance has a very high safety record and noise-abatement proecedures not tied to a significant reduction in daily operations or the passenger cap.

The committee, whose role is strictly advisory, recommended that the County Board use its influence as a governing body to lobby for recommended changes in National Airport policy with other area jurisdictions, with regional organizations such as the Metropolitan Washington Council of Governments, or with the Federal Aviation Administration, which owns and operates National; and Congress.

County Board Chairman John G. Milliken said yesterday that he had not yet read the reports, but expects that, despite the divergent opinions and recommendations, they will prove very useful to the board in shaping its airport policy decisions.

Both reports agreed that the county should establish a permanent committee on airport problems aided by an expanded county staff. Both also endorsed, with qualifications, the proposed transfer of ownership of National and Dulles International from the FAA to a regional independent authority.