Plato E. Papps, 62, general counsel of the International Association of Machinists and Aerospace Workers for nearly 30 years, died Thursday at his Chevy Chase home, where he was recuperating from surgery for an aneurysm.

A nationally known labor attorney, Mr. Papps won numerous landmark decisions, including a U.S. Supreme Court decision protecting the seniority of IAM members.

He considered his greatest victory to be a $6.5 million settlement by National Airlines for IAM-represented airline mechanics. In that case, which involved 1,200 mechanics who lost their jobs because of a work rules dispute, Mr. Papps won reinstatement and back pay for the 1,200 workers.

Mr. Papps began his legal career as an attorney in the Department of Justice's anti-trust division. He also was a legal assistant for the National Labor Relations Board for two years before joining IAM in 1951. n

He was a member of the Advisory Panel on Labor-Management Relations Law for the Senate and, in 1970 and 1971, was chairman of the American Bar Association's section on labor relations law.

Mr. Papps was born in Detroit, Mich., and earned a law degree from Columbus University School of Law here, now part of Catholic University.

A first lieutenant in the Army during World War I, he served in the Pacific and took part in the invasion of Okinawa.

Suvivors include his wife, Helen, of Chevy Chase; two sons, Harrison, of San Francisco and Christoper, of Montgomery County, and a sister, Mrs. John Kirkwood of Washington.

The family suggests that expressions of sympathy be in the form of contributions in his name to the American Heart Association.