The new chairman of the Civil Acronautics Board yesterday said he will be considering ideas that others may think are "impossible" in his effort to rid the agency of provisions he now believes are "arbitrary," "stupid" or "irrational."

In fact, Alfred E. Kahn told a "bring-your-own-lunch" press conference, that he had not read the full statute under which the board operates. "I'm trying not to," he said. He plans instead to propose "rational" solutions to problems, and make the lawyers on the board's staff convince him solutions can't be implemented under the current law.

The economist, a college professor turned regulatory, explained his operating philosophy at some length while discussing the board's pending probe of overbooking, a common industry practive in which more passengers than can be accomodated on any given flight nevertheless are given "confirmed reservations." The airlines contend the practice is necessary to account for no-shows.

"There are obvious things an economist think about overbooking that everyone in the industry thinks is impossible," Kahn said. "Well, I damn well want to be convinced that it's impossible to get a system in which you have some rational way of choosing who gets bumped and who doesn't.

He expressed distaste for "some arbitrary standard, justified on some ground of 'equity.'"

Currently, the airlines are required by the CAB to warn travelers through ticket notices and counter signs of the possibility that flights may be overbooked and that they may be "bumped." Also under current rules, an airline must take a passenger who has been bumped to his destination within two hours of the original flight's arrival, or reimburse him for the ticket price, up to $200, in addition to letting him keep and use it.

"An economist looks for ways to minimize social damage," Kahn said yesterday. "It does not make sense that somebody to whom . . . being bumped or not being bumped is a matter practically of indifference should automatically stay on a flight while somebody to whom it may be a matter of life and death is bumped from a flight."

What he would like to see is a solution is which "every bumpee is voluntary" so that "nobody gets bumped who's unwilling to be bumped" and "those who get bumped are satisfied with the compensation."

What he envisions is something like an "auction" in bumping situations. The airline might announce that the CAB requires that nobody who gets bumped be compensated in the following way, and asks, "Who is willing to take it?" In that way, there is "self-selection," he suggested.

He noted that he did not regard overbooking itself as "morally outrageous" but found the provisions to deal with the results unsatisfactory.

In a wide-ranging question-and-answer session, Kahn also:

Complained of the "niggling questions" the board is called on to decide. "I already know that if the statue requires the board to do everything it does now, it has to be changed . . . Why should I have to decide whether Pan Am should fly horses from one point to another?" he asked. The board has the authority to fix rates for transporting commodities from one point to another. There are an infinite number of commodities and pairs of points, he lamented.

Said that seeing to it that would-be travelers who cannot now afford to fly will have the opportunity in the future was "almost my primary goal . . . I'm interested in getting rates down . . ."

Admitted he couldn't give his "unqualified endorsement" to Donald Tucker, President Carter's nominee for the board, because "I'm not acquainted with him . . . or his qualifications . . . or with the questions that have been raised publicly about him."

A brief conversation with Tucker, however, convinced Kahn that he generally favors more competitions in the airline industry and supports legislation to insure it.

Hopes to get together with the chairman of other regulatory agencies to discuss regulation in general ans procedures. He specifically said he would like to talk with Interstate Commerce Commission Chairman Daniel O'Neal to tell about something "rediculous" the ICCI is doing.