Hank Irvine, a professional tennis teacher, and Herb FitzGibbon, a securities salesman, won the Middle Atlantic Platform Tennis Championship yesterday.

Trouncing Keita Jennings and Chum Steele, 7-6, 6-2, 6-0, Irvine and FitzGibbon picked up the $3,000 first prize with their second win in two weeks.

The four played before about 350 persons at Columbia Country Club in brisk but sunny weather. Washington was the seventh of nine stops in the pro tour, with the tournament sponsored by Tribuno Platform Tennis of Washington.

The closest Jennings and Steele, who were fourth, came to upsetting the third-seeded pair in the match, was during the seven-point tie breaker in the first set that FitzGibbon and Jennings won, 7-4.

From then on, the Boston-bosed Jennings and Steele, who picked up $1,400 for their efforts, were never really incontention as they were forced into defensive shots.

Irvine and FitzGibbon played almost all their points at the net, serving sharp returns that forced their opponents to play off the wire that encloses a platform court.

Irvine, a Davis Cup player on the Rhodesian team of 1968-69, and FitzGibbon, a member of the U.S. Davis Cup team in 1965-66, won the Tribuno Washington Tournament in 1975.

Both have been active for years in platform tennis, a game closely resembling regular tennis, but played with the features of paddleball.

The game is played on an elevated platform. The court is about half the size of a regulation tennis court and is fenced by wire. Only one serve is allowed.

We finally broke their serve (in the first set) and I suppose it took the wind out of their sails," and Irvine, 33, a teacher at the Short Hills, N.J., Country Club. "I had a good day at the net, which is a key to our offense. We like to keep them back as far as possible."

FitzGibbon, 34, a New Yorker who is considering taking up platform tennis full time, said an added factor was that, "We're playing like a team now," he said. "We never really worked together too well before, but it is only our second year together."

He said that their opponents' serve was off today. "They're usually much better."

Jennings and Steele started to show signs of a possible comeback in the seventh game of the second set. Although Irvine and FitzGibbon were ahead, 4-2, at the time, the Boston partners were shaking Irvine's serve at love-40. But the tennis pro forced the Boston duo into returning the next four serves into the net.

In the semifinals, Jennings and Steele defeated sixth-seeded Mike Ducey and Jim Symington, 3-6, 6-3, 6-3. Irvine and FitzGibbon advanced by taking second-seeded Steve and Chip Baird, 3-6, 6-2, 6-0.