FORMER Health and Human Services Secretary Richard Schweiker loves to tell the story of the night he and the woman nominated to succeed him were on a red-eye flight to London. Schweiker, then a senator from Pennsylvania, and Margaret Heckler were part of the same congressional delegation heading for an exchange with the British Parliament.

"Just about everyone was sound asleep and they were showing this movie. It was something like 'The Towering Inferno,' where a big building burns down . . . The screen was tremendous. It took up the whole front of the tourist cabin . . .

"Well, right at the part where the whole building dramatically goes up in flames, Peggy woke up, saw the explosion and started screaming. She thought the plane was burning up and she kept yelling "Fire! Fire!" . . . She alarmed everyone. It was the funniest thing I'd ever seen . . . We finally did calm her down . . ."

Little wonder she is often portrayed as excitable and impulsive. As an eight-term moderate congresswoman, Heckler acquired a reputation for being both shrill in her arguments and tenacious in her aims, often grandstanding on issues. She is known as a shrewd, tough political pro. But she is not remembered for her legislative victories; rather, she was considered a nervous voter with a scattered committee history.

Last month President Reagan nominated Margaret Mary O'Shaughnessy Heckler of Massachusetts, who lost her 1982 reelection bid, to be secretary of the Department of Health and Human Services. If confirmed by the Senate, Heckler, 51, will assume control of the third-largest budget in the world--$276 billion--after those of the United States and the Soviet Union.

One problem remaining as she awaits her confirmation hearings, however, is her $190,000 campaign debt, which the White House has asked her to clear up. "I told her that that condition had to be met before the nomination went to the Hill," said White House counsel Fred Fielding. "We wanted to be sure that had been done so if anyone had any questions about the contributions, they would have the opportunity to ask." Heckler made a large dent in her debt on Thursday night, when she raised about $150,000 at a $500-to-$1,000-a-ticket dinner at Boston's Harvard Club.

Although her boosters tout her as gutsy and energetic, Heckler's appointment has caused some White House aides to wince. She has little administrative experience, and her committee service has not provided much exposure to health and welfare issues.

Moreover, former staffers cite her high office turnover as evidence of poor management abilities.

"It's a terrible appointment," said one White House aide. "It was done much too quickly and she doesn't have the background . . . They wanted a woman--I could have found them a woman . . . What qualifies her? She needed a job."

"What qualifies her?" says Edwin Meese, counselor to the president. "The fact that she's had a career in government, she's well-educated and the president thought she could do the job."

Within days of her nomination, the White House named as her deputy John Svahn, the no-nonsense commissioner of the Social Security Administration. Svahn is known as a Reaganite insider. Heckler's detractors maintain that he will actually be running the agency.

"You always need nuts-and-bolts people to run an agency," says another White House source. "The point is that she is articulate and one of the top qualifications for a Cabinet secretary is to have someone out front who can speak for the agency."

Indeed, Heckler is accustomed to publicity.

A Debbie Reynolds look-alike, she was elected to Congress at 35 after defeating a political landmark (21-term Rep. Joe Martin) and became an instant media favorite. At the same time, her colleagues and friends acknowledge, she's petrified of the press. Neither she nor her schedule was readily available during her recent campaign. Her office declined several requests to be interviewed for this article, citing "time constraints."

Yet she loves the attention, the same people say. Last year the cameras swooped in and she planted a big kiss on President Reagan's cheek as he left the House chamber after the State of the Union address. "She would invariably stake out the aisle at 6 or 6:30 if the address was at 9 . . . and wear something very bright to pick up the cameras," says one congressman.

Her ability always to surface moments before the flashes pop has earned her a nickname on Capitol Hill: "Peggy I'd-Walk-a-Mile-for-a-Camera Heckler."

For years, the Massachusetts delegation on the Hill has snickered about Heckler's languid pace in casting her vote. As one of only two Republicans from a liberal state, it was no secret that Heckler feared the political consequences of being on the wrong side of an issue. According to several members, she would normally wait until the entire delegation voted before committing herself.

Sometimes they played little practical jokes on her.

Once, a number of them voted, and after she followed suit, changed their votes. Another time, according to two members, several members of the delegation stood in the back of the chamber and watched her come in and look up at the lit board that would indicate how her colleagues from Massachusetts had voted.

They hadn't.

"She would get all flustered when we hadn't voted . . . She wasn't known for being decisive," says one Democrat from the delegation. "She would sit on the floor and just watch the board to see how everyone voted. It was kind of a joke . . ."

"That has been a standard joke about her voting," said Rep. Silvio Conte, the other Republican in the delegation. "But this is altogether different. She doesn't have to worry about getting votes any more. I think she'll change . . . She's worked very hard and earned her spurs . . . It's a good appointment."

Last year Heckler cosponsored a controversial bill on drug patents and then voted against it. The House fight against the bill--which would have protected patents for brand-name drug companies as opposed to the generics--was led by her liberal congressional opponent, Democrat Barney Frank. It was widely believed she switched her vote because of him.

But what her detractors on Capitol Hill label as indecisive and shallow, supporters defend as deliberative and cunning. When she finally does come to a decision, several say, she won't be budged. As proof, they cite her unbending support of women's issues.

"I suppose that's all true," said one longtime former aide about her vacillations. "Her colleagues make fun of her, but she did survive in a district that rightfully should have had a Democrat as representative. And she did it by very close calculations on how to vote. She's an astute, careful politician."

"There's a difference between being deliberate and indecisive. She's indecisive," said Joshua Resnick, who served as Heckler's campaign press aide in 1982 and also worked for her in 1969. "Once during the campaign she wasn't satisified with the shade of pink in the bumper stickers. Then campaign manager Joe Rayball became dissatisfied. In the meantime, we had no bumper stickers . . . There was no willingness to say 'Who cares what color? We need bumper stickers.' All she worried about was the color. It was ridiculous."

Friends and colleagues agree that she has a short attention span and little patience with the tedium of the legislative process. Staffers in her office thereby devised the Rule of III.

"If she wanted you to do something and you could stand up to her nagging you three times about it, she'd usually forget what she wanted after that . . . and you wouldn't have to do it," says a former aide.

"She's impatient in the sense that you really have to get the message across to her in 10 minutes," says Rayball, longtime friend and aide and her last campaign manager. "If not, you're not going to impress her because after 10 minutes she's already advancing three other things. If you stretch it out any longer, she starts slipping."

Fueling this reputation is her House committee record, which one Democrat referred to as "musical chairs."

In her 16 years, she built up seniority on only one commitee, Veterans' Affairs. She started out on Government Operations for two years, moved to Banking, Housing and Currency for another six, switched to Agriculture, and wound up on Science and Technology for her last term.

Her last congressional race was a mudslinging contest between a quick-witted Jewish bachelor from New Jersey and a prim Irish Catholic mother of three. His suits always look rumpled. She is always perfectly coiffed, usually in colorful, highly tailored clothes.

The 1980 census made it clear that Massachusetts would lose one seat. The redistricting pitted Heckler against Frank, who had served one term in the House. Heckler was expected to walk away with it.

She had been a relentless politician during her Hill years, always attending that dance for the elderly, this fireman's ball, the out-of-the-way ribbon-cutting ceremony or the smallest parade. And up until the last election, she won them all with around 60 percent of the vote.

Her district stretched from the affluent town of Wellesley to the working man's Fall River. All her focus went to the underdog.

Once she learned that a young man from her district, who had worked his way through high school, was rejected from the Naval Academy. She called in officials from the school and berated them. He was accepted shortly afterward.

Another time, when some of her towns were being overwhelmed by a vicious blizzard, she phoned the secretary of the Army in the middle of the night to get some government bulldozers to plow the area. "She would never take no for an answer when it came to her constituents," said Jack Horner, a former staff aide.

It always came back in votes. But this time, sources close to the race say, she ignored Barney Frank's savvy and his grasp of the issues. She refused to give her campaign schedule to the press, while Frank's visibility skyrocketed. While she belabored the issues of prostitution and crime, he was hitting her head-on with the district's economic woes: unemployment, Social Security, inflation.

One of the more closely watched races in the country, it became a referendum on Reaganomics. The more Heckler tried to distance herself from the president, the more Frank glued her to him.

She often voted with Reagan on budget resolutions in 1981, Frank would remind everyone. "And in case you're all having trouble distinguishing us," he would repeatedly tell the voters, "I'm the one who did not kiss the president on the way down the aisle last year."

Some say the key to understanding Heckler lies in understanding the career difficulties of women coming out of school in the 1950s. She told a friend once that she and her husband had both been accepted to Harvard Law School, but that the dean suggested it would be better if she went to another school. She went on to become the only woman in her graduating class at Boston College Law School in 1956.

"People don't give her credit for being a woman in a man's world, a Republican in a Democratic state, a moderate in liberal country," said one Democratic member. "She's never been in the mainstream, always an outsider . . . Yes, she's shrill and she doesn't work well with people. But she had to be all those things to get where she is. She came out of a different era. She had to fight for what she wanted."

"Ice runs through her veins," says Resnick.

Heckler was raised in East Elmhurst, Long Island, by strict Irish Catholic parents. Her father was a doorman at a New York City hotel. She graduated from Albertus Magnus College, where she got her first mouthful of politics. Heckler became the first woman to run for and win the speakership of the Connecticut student legislature. She met her husband, John Heckler, during the election.

They had a dual-city marriage for years, commuting between Wellesley, Mass., and McLean. Last year they gave up the McLean home. John Heckler, a Boston banker, managed most of his wife's campaigns. They are devoted to their three grown children, and in their spare time, she plays the piano and he foxhunts.

Her campaign slogan was "unbossed and unbought." Couple her penchant for favoring the underdog with her outspoken, feisty nature, and many observers are predicting that she'll stand up to David Stockman and the social budget cuts.

Although she is against abortion, she has been committed to women's issues throughout her career. She helped form the Women's Congressional Caucus, and fought hard to get the 1974 Equal Credit Opportunity Act, which prohibits discrimination in acquiring credit based on sex or marital status. In 1981 she inserted a statement in the Congressional Record explaining how the proposed budget cuts in housing assistance would affect needy women.

"It really depends on how she sees her role--spokesman or policymaker," said an aide of a decade. "If that's what the White House hired her for, to be a spokesman, that was a sad misjudgment. I've never known anyone to tell her what to do."

"I think if the White House thinks they have got this little tiny itty bitty thing from Massachusetts who doesn't know anything," says Ra