An apparatus designed to help paraplegics work and drive has earned some Upper St. Clair High School science students a trip to a national engineering competition next week.

The 19 juniors and seniors in Marjorie Heins' engineering design and fabrication course will be in Washington, D.C., next Thursday through Feb. 18 for the National Engineering Design Challenge finals. The Junior Engineering Technical Society, a nonprofit based in Alexandria, Va., hosts the contest annually.

This year, there is a co-sponsor, the federal Javits-Wagner-O'Day Program, which organizes government purchases of products and services from severely disabled people.

The school, which won the competition in 2004, is one of five finalists nationwide this year. One other Pennsylvania team, from Wilkes-Barre, also will attend.

"I think it is challenging, even for the most highly gifted students," said Mrs. Heins, who is the school's gifted program coordinator.

This year's assignment is to find a way for a 45-year-old woman paralyzed from the chest down to use a riding mower for her grounds maintenance job. Because she has weak shoulders, she must be able to do this without strenuous arm movement. The students weren't told whether the woman is real or hypothetical, Mrs. Heins said.

The group's solution is the EA, short for "easy access," Chair, which comprises a souped-up wheelchair and a sliding board with a stadium seat and a seat belt. The board can be bracketed to the wheelchair so a person can slide from the seat on the board into the riding mower seat.

Senior John Uhl, 18, said the seat improved on plain sliding boards, which can make people feel as if they're going to fall off. For extra safety, the seat runs on a track.

A drill powers a car jack which can raise the wheelchair seat to 35 inches, about the height of the riding mower seat. People using the wheelchair can press a button on one of the arms to change the height of the seat, enabling them to enter other vehicles as well, said senior Christopher Shawn Gilbert, 17.

Senior Raksha Kumar, 17, is the president of the "corporation" the students had to form to develop a marketing plan for their product. She said the most challenging part of designing the EA Chair was visualizing it without having a real riding mower at hand. Computers helped the class design.

"The kids are constantly redesigning," she said. "I've got metal shavings all over the rug all the time."

The students also had to figure out how the driver of the mower could adjust its blade assembly without arm strain. Senior Benjamin Burns, 17, thought up a ramp which will move the blade closer to the driver's arm. Such a ramp, Mrs. Heins said, is the only accommodation an employer would have to make for the paraplegic to do her maintenance job.

Mrs. Heins and math and physics teacher Thomas Smedley will accompany the students to Washington with financial support from the competition's sponsors and the school district. The winning school gets $3,000 and a $50 Discovery Store gift certificate for each participating student.