Spokesman for the Federal Aviation Administration and Trans World Airlines said today that preliminary analysis of in-flight recorder data suggests that a TWA airliner which went into a supersonic nosedive April 4 may never have rolled over as was first believed.

"Instead of rolling over, we think the plane may have banked steeply to the right and then to the left," said Jerry Cosley, a TWA vice president.

"We're not sure the plane rolled over." said Grant Dillman, deputy assistant chief counsel for the FAA.

The two men made their comments in separate interviews following extensive testimony of the TWA pilot, Harvey (Hoot) Gibson, at a public proceeding of the National Transportation Safety Board.

In his testimony Gibson said he rolled over not once but twice and dropped from 39,000 feet to an estimated 15,000 feet before finally righting his plane in the clouds by dropping his landing gear.

Gibson said the high-speed dropping of the gear sounded "like a freight train" and touched off cockpit warning lights indicating that the gear was not properly locked into place. As a result, he said, before landing he flew at low altitude over Detroit Metropolitan Airport to enable ground crews to see if the landing gear was still on the plane.

The Boeing 727 airliner, enroute from New York to Minneapolis, then made an emergency landing at the Detroit airport. Only three of the 87 persons aboard were injured, none seriously. At the proceeding today, Gibson and other crew members gave depositions and were questioned by lawyers for the FAA, TWA and the Air Line Pilots Association.

But the testimony failed to unravel the two central mysteries of the incident - its cause and the reason for the erasure of the cockpit voice recording made on the flight.

The prevailing theory among safety investigators is that the plane went into its steep and nearly fatal dive because of a malfunction of a six-foot retractable flap on the forward edge of the right wing known as a "slat."

Gibson met with reporters after the testimony and discussed his actions in detail but on the advice of his attorney declined to sepculate on reasons for the mishap.

The veteran pilot, who has flown for TWA for 16 years and logged 23,000 hours of air time, appeared to resent the persistent questioning of FAA lawyer Dillman on the reason for the tape erasure.

Gibson, who repeatedly said he had no recollection of earsing the recording, said that Dillman was trying to insinuate that he erased it deliberately.

"We had an emergency," said Gibson. "I never thought about the cockpit voice recorder."

FAA regulations require that cockpit voice recordings be preserved after any incident or accident. But Gibson said the recordings are erased routinely by pilots when they land and that he has always followed this practice. Asked why, he replied:

"I might say something unkind about some of the people in management and they might take the tape out and send it someplace."

Gibson said the recording would have shed no light on the incident beyond showing what a "highly professional" job his crew had done in the aftermath. The mishap occurred 45 minutes before landing, he said, and the recording is for only the final 30 minutes of the flight.

The cockpit voice recorded is separate from another device that records electronic readings on the plane's altitude, speed, attitude and other critical in-flight information. These readings were not erased. They have not been analyzed in detail, but a preliminary study of them led the investigators to doubt that the 727 rolled over.

Whether the plane actually rolled over, it is the general belief among industry and federal aviation observers here that the pilot did a remarkable job to bring it under control after a dive in which it apparently reached speeds of up to 625 miles an hour. Gibson said that there was so much noise in the cockpit that neither he nor the crew heard the over-speed indicator.

Recounting the incident, Gibson said he first felt "a buzz, and then a gentle buffeting" and noticed that the plane was banking to the right while on automatic pilot. He then took over the controls manually.

Gibson credited his off-duty hobby of acrobatic flying with helping him in the emergency. He seemed at times today to regard the board proceedings as an even greater ordeal than the high-speed dive as he answered questions tersely and sometimes questioned Dillman about the purpose of his interrogation.

"Asked his age by a reporter during an interlude in this cross-examination, Gibson replied: 44, going on 60." CAPTION: Picture, TWA Capt. Harvey Gibson: "I never thought about the cockpit voice recorder." AP