Backers of House legislation setting a 15-year limit on liability of general aviation manufacturers' aircraft design and parts are confident Congress will move this year on the measure.

The confidence is based on several factors - nearly 250 House members have signed on as co-sponsors, meaning the measure should pass easily once it gets to the House floor; support for the idea by the recent presidential commission on aviation issues; and the presence of a similar bill in the Senate.But, in past years, when other aviation product liability bills have been introduced, the House Judiciary Committee has been the chief hurdle. The Association of Trial Lawyers of America has been effective in blocking such bills before that committee, arguing that the rights of injured people to sue for damages should not be limited.

New House rules that make it easier to bypass a committee when a majority of members sign a "discharge petition" to bring a bill directly to the floor could come into play this year. Rep. Steve Horn, R-Calif., a member of the House Public Works and Transportation Committee's Aviation Subcommittee, raised that possibility Wednesday.

"Now that we have the discharge petition in the open, we'll get this," he said.

"People recognize we're doing the right thing. I believe President Clinton would sign the bill," said Rep. Dan Glickman, D-Kan., a chief sponsor of the bill.

The 15-year limit is a response to the "astonishingly precipitous decline in the manufacture and sale of general aviation aircraft," caused in large measure by the huge costs that manufacturers must incur to protect themselves

from liability claims, said Rep. James Oberstar, D-Minn., chairman of the subcommittee.

Proponents of the bill say liability costs are the single largest cost component in the construction of an airplane. New aircraft sales dropped from 18,000 units in 1978 to 899 last year. Cessna Aircraft has not made a piston- engine plane since 1986, Piper Aircraft is in bankruptcy and Beech Aircraft no longer produces training aircraft.

Edward W. Stimpson, president of the General Aviation Manufacturers Association, said that under the current legal system, "if the Wright brothers' first aircraft was flying today - after 90 years - the Wright brothers could still be found legally responsible for accidents allegedly caused by the original design of their aircraft."

They could be sued even though the plane may have been maintained by hundreds of different people, modified many times over its life, and if the accident was not related to a design problem but the failure of a component that had been replaced many times, he said.

The average age of a single-engine airplane is 27 years, and one-third of the U.S. fleet is over 32 years old.

"We have spent $20 million to $25 million each year to defend hundreds of product liability cases" since 1986, said Russel W. Meyer Jr., chairman and chief executive of Cessna.

He said Cessna is committed to "restart piston aircraft production as quickly as possible after enactment" of the bill.