What happens when the head of the most powerful nation on earth lands in your country and announces that he has come to stay, and wants to be very, very intimate with all your citizens?

It happened the other day in Poland. And President Carter is getting letters at the White House from American civil servants. They are reminding him that they are on his payroll and would like to serve, and maybe keep him out of trouble, in the future.

Some of the letters are bitter, some written with tongue in cheek. The White House apparently isn't too crazy about any of them. But they will be answered.

What the U.S. federal workers are referring to is the embarrassing Dec. 29 mixup at Warsaw airport. It was meant to be a good-will visit to a powerful Soviet Bloc nation that is the ethnic home of millions of Americans.

A miskake in translation made it appear that President Carter had left the U.S. for good, and had arrived in chilly Poland with lust in his heart. It was not, diplomats agree, the best way to kick off a trip to any country.

The point the federal workers are making its that the language problem might not have come up, if one of them had been along.

At the airport, Carter told the welcoming crowd of VIPs that he had come to their country to "learn your opinions and understand your desires for the future . . ." His $150-a-day interpreter, however, spoke into the microphones that the President had said . . . I desire the Poles carnally . . ."

Later, the President pointed out that he had just left the U.S., the intent being to underscore the importance he attaches to Poland. Instead, that came out that Carter had left he U.S., never to return."

Some in the crowd were amused, some insulted and others figured they had a real problem on their hands.

Later on, the President praised the 1701 Polish constitution as one of the premier documents in the struggle for human rights. When it came out over the microphones, however, the interpreter made it appear that President Carter was ridiculing the F link constitution.

(The free-lance interpreter, it should be pointed out, has outstanding credentials and a top reputation in the tough field. He has worked for the government before as an interpreter. He explained that the mistakes resulted in part from fatigue, poor cordination with White House aides, and others factors).

Government employees from the Navy, the Department of Health, Education and Welfare and the State Department have written the President asking that he consider the recent past next time the issue of contracting out government work comes up.

The State Department explained that it doesn't have any full-time England-Polish interpreters, and that it is cheaper to hire free-lancers when top Americans go to Poland.

The argument that things can be done better, or cheaper, is the keystone of the government's contracting out policy. Some administrations throw more business to private industry to boost the economy and court business. Others bring more work in-house, on the grounds that the government needs the capability to do certain things free in-house, and that it has more control over government workers in time of need.

It may be that the Poland trip will cause a revision of contracting-out policies as they apply to interpreters.

At the Office of Education, the AFGE union newspaper "The Word" has a front page editorial this week dealing with the Polish problem.

It says: "The Word thought you would like to know that the interpreter who fouled up President Carter's speech in Poland recently was a highly recommended and expensive ($150 a day) consultant.

"After the fiasco he was replaced by a regular State Department employee who was apparently much better qualified for that particular task. The moral? Look to your own employees first, Mr. President."

At any rate, the President sent his first interpreter a "thank you" note, telling him not to be disturbed by "exaggerated criticism." The note ended with the line. "You helped to make my visit to Poland every enjoyable and successful. Thanks. Your friend, Jimmy Carter."