When a federal judge recently blocked the Federal Aviation Administration from dispatching a small group of employes to its Atlantic City facility, the workers thought they had won their argument that they had been singled out for the shift because they are older people who might retire rather than move.

Now they think their victory has a distinctly hollow ring to it.

Thanks to the wording of the judge's order, the agency has decided that while it cannot order its people to transfer now, it is not prohibited from transferring the workers' job functions to the New Jersey office and has already shipped the bulk of the employes' work papers there.

The FAA began nudging employes to move anyway and has sent letters to supervisory employes in the two affected divisions - those dealing with airport planning and aircraft safety and noise abatement - telling them that "you can understand that your reporting as scheduled [on Sunday] is considered vital."

Supervisory employes, most of them long-term FAA workers who are in their late 40s and older, also have received memos saying, "As you can appreciate, we hope that all persons associated with the transfer of functions proceed as scheduled to Atlantic City in order that we may get on with our mission."

The sudden apparent turn in their fates has left some employes puzzled.

"I think they have either misunderstood the injunction or decided to ignore it," said Stephen A. Cannistra, 64, a $40,000-a-year, 20-year FAA employe and one of four men who filed suit to block the transfers.

"Everybody in both divisions felt that management was sending us letters in hopes we'd panic, and go ahead and move," said Cannistra, who monitors research and development involving airport runway pavement.

"We try to keep up with the work," he said, "but soon we're going to need our files."

So far, only a handful of the workers have begun packing their bags for the trip to Atlantic City. The FAA says that seven of its employes have decided to go to their new offices at the National Aviation Facilities Experimental Center, a testing plant for airport equipment, while another five have opted to retire. Cannistra says that 20 to 24 are still fighting the FAA directive ordering the transfer.

In late July, U.S. District Court Judge Harold H. Greene ruled that the FAA "has not demonstrated that its [transfer] decision was based on reasonable factors other than age" and that there is "at least a substantial likelihood" that the workers will be able to prove their age discrimination claims when the case goes to trial.

He granted the workers' request for a preliminary injunction blocking the transfer of the two divisions, but said that the FAA could allow "those individuals who have already relied on its directive who prefer to be transferred to make the move."

Greene wrote in his opinion that the suit was seeking to block the transfer of "functions and personnel." But he only mentioned "personnel" in his actual preliminary injunction order.

In his letter to the affected workers, A. P. Albrecht, the FAA's associate administrator for engineering and development, notes that "the preliminary injunction did not involve the transfer of functions which was approved by the Secretary of Transportation on March 28, 1979."

The FAA said it is not circumventing Greene's order because the job functions were transferred immediately after then transportation secretary Brock Adams gave his approval, four months before Greene's ruling.

Harvey M. Katz, the workers' lawyer, has asked Greene for a clarification of his order, saying that the transfer of the job functions and memo telling supervisors how "vital" it is that they go to Atlantic City "were designed by the FAA to subvert the court's order and to further the objectives of the initial transfer directive."

Katz said the FAA is trying to "tip-toe between the words of the court's order" and is exhibiting a ""we'll show you" attitude toward the [affected workers] and the court."

Greene has not acted on the request for a clarification.