Charles W. Cheng, a top leader and contract negotiator for the Washington Teachers' Union during its first years as bargaining agent for the city's teachers, was among the 270 persons who died in the DC10 airplane crash Friday in Chicago.

Cheng, 42, a familiar figure at District school board meetings and the union's representative at demonstrations in the late 1960s and early 1970s, changed his ticket reservations only a few hours before the flight to get a seat on the plane that crashed on takeoff, according to his relatives.

Cheng was flying to his home in Los Angeles from Madison, Wis. He had gone to Madison for a teacher's conference and had decided on Friday morning to take an earlier flight home.

Cheng, who left Washington in 1972 to study for a doctoral degree in education at Harvard University, was a professor of education at the University of California at Los Angeles, specializing in collective bargaining.

Cheng was one of five persons known to have Washington-area connections who died in the crash. The other four are: Kerry D. Tims, 19, a student at Howard University who was on his way to visit his parents in Monrovia, Calif.; Robert Lamar Cannon, 46, who lived in the Washington area between 1955 and 1976 and was travelling to his current home in Santa Monica, Calif.; and two persons, Michael R. Smith and R. Griego, identified only as Washington area residents by American Airlines.

Cheng came to Washington in 1967 to help William Simons, president of the Washington Teachers' Union, campaign to win the right for the WTU to be the sole bargaining representative for the city's teachers. After the union won the election Cheng became the number two man in the union with the title of executive assistant to Simons.

"Charles was recommended to me by the national AFT (American Federation of Teachers)," said William Simons. "They said he would be the kind of person who would be very valuable in the embryonic stages of the union. He certainly was that. He brought with him a sense of dedication as a tireless worker and prolific writer. He had the ability to organize people and get things done."

Simons said Cheng had written to him during the recent teachers' strike to suggest possible solutions to the impasse that caused the strike.

"He was still interested in what was happening in Washington," said Simons.

Cheng gained a reputation in Washington as a tough negotiator at the contract table and a bold, dramatic character in public. In 1970 he was arrested with four other persons, including former city councilman Douglas Moore, for disrupting a school board meeting. In the same year he wrote a resolution calling for the resignation of Spiro Agnew, then vice president, and John Mitchell, then attorney general, for allegedly "regressive statements and actions" that Cheng said they made against Washington school children.

By 1972 had changed his views on the teachers' union. He told an interviewer that the union needed more active teachers and he said, he was concerned about "institutionalized leadership." After spending a year at Harvard Cheng went to UCLA to accept a teaching position.

Kerry Tims, a 19-year-old California resident who had just finished his freshman year at Howard University was also on the American Airlines jumbo jet taking off from O'Hare on Friday.

After completing courses for the year at Howard, Tims had gone to Hartford, Conn. for a two-week seminar for majors in business insurance. He was headed home to Monrovia, Calif. on Friday for a brief stay with his parents before leaving again for a summer job.

Maurice Williams, one of Tims' Howard professors described the freshman as "A youngster ready to burst out.He was the kind of kid that made you wonder what he would be doing in five years . . . he was quiet, with a solid strength and a reservoir of talent waiting for someone to tap it."

Williams said Tims was the president of his high school senior class at a private school in California. According to Williams Tims was one of the few black students at that school. He distinguished himself as an athlete and a scholar, Williams said.

Another person with Washington connections on the flight was Robert L. Cannon, who lived in Bethesda between 1955, after graduating from Duke University, and 1976 when he moved to California. While in Washington Cannon worked for the ITEL Corp. in Georgetown Square and IBM.

The son of the late Gen. Robert M. Cannon, Cannon was born in the Philippine Islands.

"I don't know that he loved to fly," said a friend of his family, "but he did it all the time. It was just part of his business."

Also aboard flight 191 were: Sheldon Wax, managing editor of Playboy Magazine, and his wife Judith Wax, a well-known Chicago writer; Henry F. Regnery, 34, of South Bend, Ind., vice president of Regnery/Gateway Inc., a publishing house and son of the company's founder Henry Regnery. CAPTION: Picture, CHARLES CHENG . . . former union organizer