For six minutes and 20 seconds of his life - sweating, gasping and grimacing as he frantically pumped the bicycle pedals to keep his 77-pound makeshift aircraft aloft - Bryan Allen felt better than a bird.

"birds are superbly adapted for flying." said the 24-year-old, lanky Californian. "but they don't seem to fully appreciate what they're doing."

Now, two years after he became the first human being to pilot a completely man-powered airplane in a sustained and controlled voyage, Allen is readying himself for another entry in the Guinness Book of World Records, and a possible $200,000 prize.

Sometime around May 1, Allen plans to take off in the Gossamer Albatross and try to pedal the aircraft across the English Channel at a speed of 11 m.p.h., and at an average altitude of 20 feet.

The 21-mile trip will keep Allen, whose longest previous flight has been 16 minutes, pedaling for more than two hours.

In one of his last jet-propelled trips before setting off the Eng- lish coast, Allen came to Washington yesterday to speak to a group of "aviation educators," including elementary school teachers and NASA specialists, who have come to the 4-H Center in Chevy Chase from every state in the country for their first convention.

Allen's historic plane, an aluminium, cardboard, and balsa wood contraption covered with cellophane, and held together with adhesive tape hangs above the Wright Brother's plane in the National Air and Space Museum. Called the Gossamer Condor, the plane became the subject of a documentary film that won an Academy Award this year.

Its succesor, a more complicated, more finely constructed version of the same pedal-driven model, is called the Gossamer Albatross. It is named after a bird which "flies low over the waves, is big and ponderous and brings good luck," said Allen.

Both planes are based on a simple principle, inspired by the hang glider, which for years eluded more than 20 designers who couldn't get their own planes off the ground.

"the less weight on a plane, the less the puny muscles of the human have to work to raise it into the air," Allen explained.

The Gossamer Albatross weighs 62 pounds, 15 less than its predecessor. It has a wingspan of about 95 feet, "larger than a DC-9," but has never travelled faster than 10 m.p.h.

The simple design, by Dr. Paul MacCready, the man who organized the project, is propelled by a set of bicycle pedals inside a small pilot's compartment, attached to a long bicycle chain. When Allen pedals, the chain turns a 10-foot horizontal pole above the wing, which in turn moves the rear-end propeller.

Enlisted to pilot the first plane "because I had experience with hang gliders, I was on the track team, and I happened to be in the area," Allen trained for five months and made over 400 flights before finally conquering the 10-foot high, 1 1/4 mile figure-eight course. As the first person to successfully complete the course, Allen and the plane's designers won a prize of about $100,000, which had been set up by British industrialist Henry Kremer in 1959.

Since December, Allen has bicycled about 5 miles a day, while a team of about 25 people work to complete the three planes to be used in the channel crossing attempts.

The entire project will cost about $200,000. This time, however the group is being backed by the E.I. DuPont de Nemours chemical company. The original project cost $3,500, which the designers anted up them-

Allen said yesterday he is more interested in the excitement of the challenge and in the possibility of practical applications than he is in a new entry in Guiness'.

"i'd be more thrilled if I'm not in Guiness. As it is, I'm in there with all the underwater monopoly players and spaghetti consumers." CAPTION: Picture, BRYAN ALLEN . . . wingspan "larger than a DC-9"