THE LIGHT STUFF.(Jon Conrad)

"Starting one, clear one!"Jon Conrad called out. As the port-side propeller of the Spirit of America, the Goodyear Tire and Rubber Company's newest blimp, whirred to life, Conrad sat up straight in his high-backed pilot's chair. His goal this afternoon, he said, was to "wear the airship"--which meant handling the blimp in a particularly unhurried, laid-back fashion. Conrad, who had recently been named Goodyear's only pilot-in-training, sat to the left of his instructor, John Crayton. After Crayton gave him a nod, the young pilot looked through the cabin windshield and signalled to the ground crew, who stood alert on the wide, grassy airfield. He held up two fingers and made a rotary motion, then started the second prop. After pausing for several seconds, he spread one palm wide and punched the air with his other hand, communicating his readiness for takeoff. The Spirit of America rolled across the airfield, bounced once, then sailed serenely up into the fading blue sky above Carson, California.

Conrad was dressed in a white short-sleeved pilot's shirt and a Stars and Stripes tie. His right hand rested on a large wooden wheel, which he moved gently back and forth to adjust the altitude of the ship. He inched the blimp right or left by using two foot pedals, which he worked as if he were a church organist, minutely flexing toes, heels, and calves to counter the shifting air currents.

The metal cabin of the Spirit of America, which seats six and resembles a ski gondola, offered spectacular, two-hundred-and-seventy-degree views of suburban Los Angeles. As the blimp glided upward, the student chatted amiably with his teacher. A thirty-three-year-old native of Scottsbluff, Nebraska, Conrad is an even-tempered, pleasant fellow whose conversation is punctuated by exclamations like ''I'm as chipper as a blue jay."Well over six feet tall, he has 20/400 eyesight (a debility that would disqualify him from becoming a pilot in the Air Force). He resembles a grownup version of the cheerful lad in overalls who appears on cans of Dutch Boy paint. In the three months since accepting Goodyear's offer and moving to Hermosa Beach, California, he had yet to ask a woman out on a date. Instead, he spent his evenings between Wednesday and Sunday--blimp pilots have Monday and Tuesday off--floating a thousand feet above the freeways between Los Angeles and San Diego.

Blimp pilots prefer to think of themselves as captains of airships; indeed, blimp flight has an oddly nautical feel. The ship rises upward like a balloon, yet it feels supported underneath, too, as if it were floating on water. Equipped with motorized propellers and a set of steering controls, blimps are easier to navigate than hot-air balloons, which lack thrust. The two hundred thousand cubic feet of helium trapped inside a Goodyear blimp can lift about twelve thousand pounds. The aircraft's two side engines provide aerodynamic control, allowing a pilot to fly precise figure eights or box patterns over a sports stadium.

The derivation of the word ''blimp'' is unclear. One common explanation is that it was coined in 1915 by Lieutenant A. D. Cunningham, of the British Navy. During an inspection at a landing strip in Capel, England, legend has it, the lieutenant playfully poked one airship's balloon with his thumb; an amusing sound was produced when the bag's fabric snapped back into shape, and Cunningham responded with a verbal imitation: ''Blimp!''

The spongy exterior of a Goodyear airship, Conrad explained, is made of polyester fabric coated with rubber. The envelope contains a central helium balloon, along with fore and aft air bags, or ballonets, which help control the ship's pitch. He pointed to two white toggles mounted on the ceiling above his chair; by pulling them, he could adjust the inflation level of the ballonets. Since air is heavier than helium, pumping air into the fore ballonet caused the nose of the blimp to dip; air in the aft ballonet caused the nose to rise. A red toggle allowed for the emergency dumping of fuel. Blue and yellow toggles operated the blimp's helium vents, which were situated on either side of the airship, inside the letter "y"in "goodyear."Helium could be vented in an emergency, Conrad said--if, for instance, the blimp soared dangerously above its ten-thousand-foot flight ceiling.

There are three Goodyear blimps currently operating in the United States: one is based in Carson, California; one in Pompano Beach, Florida; and the third at the company's headquarters, in Akron, Ohio. Each blimp has four pilots. Conrad's mentor, John Crayton, is known as the P.I.C. of the Spirit of America; those initials stand for ''pilot in charge.'' He is a courtly, old-school gentleman with a walrus mustache and an easy manner, whose twin mantras are "Get lower"and "Get slower."As Conrad curved the blimp northward, Crayton said, "I have a basic theory of blimp pilots. It's all about getting used to where the buttons are, and learning patience."