Former White House deputy chief of staff Michael K. Deaver was employed by Trans World Airlines for the primary purpose of contacting then-Transportation Secretary Elizabeth Hanford Dole and was asked to do little else under a $250,000-a-year retainer, the former head of the company's Washington office said yesterday.

Testifying at Deaver's trial on perjury charges, Jon F. Ash, formerly TWA's vice president for governmental and international affairs, said the company turned to the former White House aide for help in the spring of 1985 as it was desperately fighting a corporate takeover.

Deaver was recruited for "the team" Ash had assembled in Washington to thwart investor Carl Icahn, the airline executive said. "We believed he could give us a hand with contacts at the White House and with others in the executive branch," Ash said.

The airline was especially eager to make what a company memo called "a direct contact" with Dole, who had authority to support a TWA petition that alleged Icahn was unfit to run TWA. Contacting Dole was Deaver's primary assignment, Ash said.

Deaver volunteered at their first meeting to help with White House contacts and said "something to the effect {that} 'I know Elizabeth and I can give Elizabeth Dole a call,' " Ash said.

Ash, now an airline consultant, was the 17th witness to testify at the trial of the longtime confidant to President and Mrs. Reagan. Deaver is accused of five counts of lying to a congressional subcommittee and a federal grand jury about contacts he made with high administration officials, including Dole, on behalf of the lobbying clients he secured after leaving the White House in May of 1985.

Although Ash's testimony seemed to buttress the prosecutorial claims that Deaver did little for his large lobbying fees, there were new indications yesterday that some key aspects of the case against Deaver are weak.

Spokeswomen for Dole and Craig L. Fuller, chief of staff to Vice President Bush, said yesterday that neither is likely to testify at the trial although both are named in the indictment as among the officials Deaver contacted.

A lawyer for Deaver hinted during Wednesday's court session that Dole does not have any memory of being called by Deaver. Fuller, who at one time was planning to leave the White House with Deaver to form a jointly owned lobbying firm, supposedly was contacted by Deaver on behalf of Puerto Rico and also apparently has too poor a recollection of the incident to be considered a good prosecution witness.

Fuller was travelling with Bush yesterday and could not be reached for comment, but a Bush spokeswoman said, "At this time we have no indication that Mr. Fuller will be called by either side."

Dole, who was campaigning on behalf of her husband, Sen. Robert J. Dole (R-Kan.), a candidate for the 1988 Republican presidential nomination, also said through a spokeswoman that "both sides have determined that it is not necessary that she testify."

Katie Boyle, the Dole spokeswoman, said the former transportation secretary did not want to discuss the matter with reporters.

Ash's statements yesterday about the extent of Deaver's work for the airline were more detailed than the earlier testimony of former TWA president and chief executive officer Edward Meyer.

But Ash, who was in charge of the company's lobbying efforts, said he was unable to give details of work, other than the Dole contact, that Deaver's firm contributed to the unsuccessful TWA fight.

He said he was aware that Deaver's firm may have attempted to contact a Cabinet committee staff worker about the Icahn matter and that William F. Sittman, a top Deaver associate, later attempted to help the airline recover a Boeing 727 jet that was hijacked to Beirut by Middle Eastern terrorists.

Sittman called back after working on the problem and told Ash, "You've got a tough problem," Ash said. "I knew that," he added as the courtroom burst into laughter.