MILWAUKEE (AP) _ The senior test pilot for the manufacturer of the Midwest Express Airlines DC-9 that crashed on takeoff last fall told a federal investigative panel Wednesday there might have been a breakdown of communications in the cockpit.

He was stopped abruptly, however, by James E. Burnett, chairman of the National Transportation Safety Board, who said the witness was engaging in speculation.

Investigation has shown that the right engine of the plane failed just after takeoff the afternoon of Sept. 6 from Milwaukee's Mitchell Field and the left engine lost power. The plane went down in a woods just south of the airport and explosed and burned, killing all 31 aboard.

Rudy Canto of Long Beach, Calif., senior pilot for flight standards for Douglas Aircraft Co., was asked what his response would be in a similar takeoff situation if he were the flight officer and the captain said, ''What have we got here?'' during an obvious engine failure.

''The pilot not flying should have responded, 'Engine failure,''' Canto replied. ''There was an obvious breakdown of communications. The fact the question had to be asked twice...''

Burnett then stopped the comment.

Investigation has shown that the captain of Flight 105 asked the co-pilot, ''What do we got here, Bill?'' and the first officer responded to the tower, ''Midex 105, Roger, we've got an emergency here.'' He did not respond to the captain and there was no further communication from the plane.

Danny Martin, 31, was the pilot and William Weiss, 37, the co-pilot.

The plane gained an altitude of only about 300 feet before rolling into a right steep bank and plunging nose first into the woods about one-half from the airport. The flight had originated in Madison and was headed for Atlanta, with one stop in Milwaukee.

Midwest Express Airlines, based in Appleton, is owned by Kimberly-Clark Corp., the paper products manufacturer.

Board members Wednesday spent time questioning Canto about rudder control. Asked if he had ever experienced uncontrolled rudder deflection in a DC-9, he said, ''No. I did not, and I have never heard of one.''

He said there was nothing in Douglas training manuals on the subject.

''If we thought it was a problem, we would have incorporated it,'' he said.

George Buddy, a Federal Aviation Administration pilot who certifies DC-9 pilots, disagreed with earlier testimony from Midwest Express Airlines' chief pilot that there is a critical time during takeoff when the first officer should remain silent even during engine failure because there is nothing at this point that could be done to make the plane fly any better.

''A crew member should call out a loss of engine, at any time,'' Buddy said.

''If there are procedures that need to be made or accomplished, there should be some callouts,'' he said.