The experimental X29 jet with the forward-swept wing took flight for the first time yesterday, with the pilot gingerly testing the computerized controls as he rocked the plane back and forth over Edwards Air Force Base in southern California.

Grumman test pilot Chuck Sewell kept the landing gear extended and held the plane to 270 miles an hour for this first flight. The idea was to make sure that everything worked properly, not to see how fast or high the radically different-looking plane could fly.

All went well, Sewell said after he climbed out of the X29. "My only complaint is that I didn't have enough fuel to stay up longer," he said. The flight lasted 58 minutes and was confined to the area around Edwards and an altitude of 15,000 feet.

The X29, which has the nose of an F5 fighter, will never take to the sky as a fighter in its own right. Instead, it is supposed to help the United States design fighter planes of the future. Not until space age materials like graphite become practical for aircraft construction could wings be built light and strong enough to reach into the oncoming flow of air as the plane sped along.

It is hoped that the forward sweep will give the X29 and its successors advantages in maneuvering for the kill in a dogfight. The Defense Advanced Research Projects Agency and Grumman were intrigued enough with the possibilities of the forward-swept wing to put up $92 million and $40 million respectively to build two X29s.

The X29 is scheduled to fly again next week. Grumman will fly the plane twice more after Christmas, then turn it over to the Air Force and NASA for a separate series of tests.

If its computerized controls failed, the X29 would not glide to the ground but fall like a rock. The computer keeps the inherently unstable plane in the air by checking every move of the flight control surfaces 40 times a second.

Before yesterday's flight, Sewell spent 400 hours on the ground in an Atari-like device that simulates the feel of the X29 in flight. "It flies better than the simulator," he said yesterday after flying the real thing for the first time.

In August, when the X29 was rolled out, Sewell said he would be at the mercy of the three computers on board once he got the plane in the air. "If I lose all the computers, the airplane self-destructs in two-tenths of a second," Sewell said then. "That's a tad faster than my reaction time to reach down, find the emergency handle and pull it."

Testing new planes is something like learning to ski. Sewell was kept on the equivalent of the bunny slope yesterday. Every flight from now on that he and fellow test pilots make will be riskier, eventually reaching a speed of about 900 miles an hour, if all goes well. The plane also will be maneuvered to its limits to test the dogfighting potential.

The X29 represents a return to the X series of aircraft made legendary by Chuck Yeager and other test pilots. The race for the moon eclipsed their efforts and budgets in the 1960s and 1970s.

While the X series is being revived with much attention, another school of thought holds that missiles are becoming so lethal from all angles of fire that they, not radically different fighter designs, will determine who wins the dogfights of the future.

The United States has developed missiles that can hit enemy planes while they are 50 miles away, half that distance or close up. The close-up missiles home in on the heat of the enemy plane, exploding near enough to destory it even when the two planes are flying head to head.