Two Virginia members of Congress called yesterday for an investigation into the taxi service at Dulles International Airport, following cabdrivers' complaints that they are barely making a living wage because of the high rates they pay to the owner of the cab concession.

Nearly 250 drivers of the Washington Flyer cabs at Dulles each pay $500 a week to rent a cab at the airport, and they say they must work as much as 18 or even 24 hours a day to earn enough money to feed their families. A story on the concession arrangement appeared in yesterday's Washington Post.

U.S. Rep. Frank R. Wolf (R-Va.) said he will ask the Transportation Department's inspector general to investigate the taxi service at Dulles, but only after the next contract for the taxicab concession is awarded. "I think it's very troubling," Wolf said of the drivers' complaints.

Farouq Massoud, who operates the cab concession at Dulles, defends the rental rates that drivers are required to pay him. He contends that the drivers, almost all of whom are recent immigrants, underreport the number of trips they make and actually earn a comfortable living. He also says he has a long waiting list of applicants for Washington Flyer driver jobs.

Massoud's contract expires Oct. 31, and the Metropolitan Washington Airports Authority expects to solicit new proposals later this month. Massoud has held the contract since 1989.

Wolf, who is on the transportation subcommittee of the House Appropriations Committee, said he did not want to inject an investigation into the bidding process. But he said he wanted to place prospective bidders on notice that they would be subject to a federal investigation after the contract was awarded. "We'll have the [inspector general] look at it," Wolf said, "to make sure these conditions do not take place in the future."

U.S. Rep. James P. Moran Jr. (D-Va.) endorsed Wolf's call for an investigation.

"I think a good case could be made for doing it right away," Moran said. Moran's brother, lawyer Brian Moran, recently began representing the drivers.

Rep. Moran said he had been urging the airports authority to investigate the drivers' complaints for years. "There's a certain amount of indentured servitude when he controls the whole operation," he said, referring to Massoud. "But the airports authority is more than willing to tolerate it as long as the trains run on time."

Both the drivers and Massoud also welcomed an investigation. Robert B. Nealon, a lawyer for the Washington Flyer Taxi Drivers Association, said, "Any investigation of this matter should commence immediately, prior to the completion of the request for proposals."

Massoud said, "They should investigate prior to giving the contract. I will go along with Frank Wolf's proposal, that's fine. There's nothing wrong with [the Department of Transportation] getting involved. They should get involved in why we are not allowed to pick up in D.C."

Washington Flyer cabs are banned from picking up passengers in the District, causing many Flyer taxis to return to Dulles empty. But when District passengers call Washington Flyer for a ride to Dulles, Massoud said he dispatches cabs from another of his companies, Arlington Blue Top.

George Crawford, head of the D.C. Taxicab Commission, said suburban cabs may take D.C. passengers only to the taxi company's county of origin. "Any Blue Top taxicab operator picking up in the District of Columbia for a trip to Dulles is in violation of the law," Crawford said yesterday. He said such trips take valuable fares away from D.C. drivers, and that he would ask city hack inspectors to enforce the law.

Tara Hamilton, an airports authority spokeswoman, said the authority would cooperate fully with any investigation of the next concession contract.

CAPTION: Cab company operator Farouq Massoud says he would welcome an investigation.