An intensive battle by a group of Potomac residents to prevent Montgomery County from placing a garbage landfill site on a 370-acre piece of property at Bradley Boulevard and Persimmon Tree Road has expanded to include the Federal Aviation Administration, three aeronautics associations and a congressman.

The residents, calling themselves the Committee to Save Our Land, will meet at 10 a.m. today with county executive James P. Gleason to discuss what may be their strongest trump card in the fight against the landfill.

According to Sally Kanchuger, a member of the committee, the residents will inform Gleason that the proposed Potomac site lies beneath a flight path for planes entering and leaving Washington National Airport, and they will produce an FAA report that says landfills located near flight corridors pose hazards to aircraft.

For support, they are bringing representatives from the Air Transport Association, the Airline Pilots Association International, the Aircraft Owners and Pilots Association and the FAA, Kanchuger said.

In addition, the Potomac residents have hired their own attorney and an engineering consulting firm to aid them in fighting the landfill proposal.

Kanchuger, who also is president of the West Montgomery Civic Association, said the meeting was set up because Gleason has thus far failed to respond to letters he has received from the Air Transport Association, Rep. Olin E. Teague, chairman of the House Committee on Science and Technology, and James Murphy, director of the Washington area airports, expressing their concern about the possibility of placing the landfill beneath a flight corridor.

The problem with trash landfills, according to an FAA report, is that they attract high-flying birds which could interfere with aircraft approaching or leaving an airport. Birds which strike at aircraft in mid-flight could cause a crash.

Walter A. Jensen, vice president of the Air Transport Association, has called on the FAA to conduct a "thorough study of the possible affects of the dump and its attraction to birds."

Murphy said he is sending a representative to the meeting because the agency needs to know more about the type of landfill the county plans to operate before it can determine if there actually will be any hazards to aircraft.

"If there is a potential hazard to flight safety we will make that perfectly clear to the montgomery County government," Murphy said.

The proposed landfill is on a 900-acres site known as Avenel Farm and is one of three sites the county is considering. The others sites are at Rte. 108 and Dorsey Rd. and at Rte. 108 and Riggs rd., both in Laytonsville.

Kanchuger called Gleason's decision to include Potomac in the three final sites "a political move" to show residents he did not give special consideration to the area that is one of the wealthiest in Montgomery County.

The final site will not be selected until a county-hired consultant evaluates each site to determine which would have the least hazardous impact on the environment. The site then must be approved by the state health department.

The health department ordered the county last month to find a landfill site by June 1 to replace the Gude-Southlawn landfill in Rockville, which will reach its maximum capacity in 1982.

Citizens from Laytonsville also are fighting the possibility of a landfill there. They have presented citizen's petitions against the landfill to county officials and have sent angry delegation to present their views to the county execuitive.