Five Virginia legislators, including House Republican leader Vincent F. Callahan of Fairfax County, flew to Arizona this week on a two-day, expense-paid "inspection trip" courtesy of an energy firm that is seeking state approval for construction of a $650 million coal slurry pipeline across the state..

The lawmakers' journey to the 273-mile Black Mesa pipeline--the only slurry pipeline operating in the United States--was designed to give them a "fuller understanding of the issues surrounding" the proposal, according to a statement yesterday by the Transco Energy Co. of Houston.

Some opponents, including a senator allied with the railroads in opposing a Virginia pipeline, questioned the propriety of a private corporation picking up the tab for a handful of state legislators. "This is obviously a promotional and propoganda effort," said Sen. Ray Garland (R-Roanoke). "It raises troubling questions."

The trip represents the latest step in a lobbying campaign by Transco and its corporate partner, Virginia Electric and Power Co., on behalf of a controversial $650 million pipeline that would pump coal from Southwest Virginia to Tidewater. In the face of strong opposition from the railroads, William G. Thomas, the Alexandria lobbyist hired by Transco and Vepco, said yesterday he conceived of the trip to prove that the environmental and other objections raised by the pipeline's critics are groundless.

Thomas said that he selected the lawmakers according to their legislative assignments. Two--state Sen. Daniel W. Bird (D-Wythe) and Del. Ford C. Quillen (D-Gate City)--were chosen because they sit on the Virginia Coal and Energy Commission. Another--Del. Alson Smith (D-Winchester)--is expected to become chairman of the House Mining Committee, and two others--Sen. Elmon T. Gray (D-Sussex) and Callahan--sit on other committees that will have jurisdiction over the slurry issue, Thomas said.

The five legislators, accompanied by a Transco vice president and Vepco lobbyist E.L. Crump, left Richmond Sunday on a Transco corporate jet and, after an overnight stay in Flagstaff, Ariz., were due to return last night. Thomas said he had "no idea" how much the trip would cost. "It's not unusual for private industry to take public officials on legitimate investigative trips and that's exactly what this is," Thomas said. "And there ain't any more to it."

Thomas, a former Democratic Party chairman, said that earlier this year the Coal and Energy Commission had solicited funds from industry to pay for studies on the slurry issue. He also said that legislators on the commission's uranium subcommittee had taken trips to visit western uranium mines at the expense of uranium companies.

A commission staff member said yesterday, however, that the trips to the mines were paid for from a $100,000 grant from the National Science Foundation. When the commission discussed private funding for a coal slurry study, it solicited the monies from all parties in the dispute. "We approached the railroads, the utilities, we didn't pick one group," said state Del. A. Victor Thomas (D-Roanoke), the chairman of the commission's coal subcommittee. "We asked all of them."