He's rich, many times a millionaire, a famous pilot, a designer, a man with a penchant for sleek airplanes and stylish women, a self-described arch-conservative, and the most powerful industralist in this desert state. Still, Bill Lear is more Tom Swift than Howard Hughes.

At the age of 75, Lear also may be the world's best argument against forced retirement. His round face is often flushed and puffy at the jowls. He walks slowly through the machine shop and engineering departments of his Lear Avia aircraft plant. With some difficulty, he negotiates the steep stairs that lead into the plywood, full-scale mockup of his new plane, the Lear-fan.

But nestled in the pilot's seat, Bill Lear is a kid again, and Lear, who is a betting man, wagers that his new toy will set the industry back on its collective aileroons and win back his reputation as the living prophet of modern aviation.

In 1963, when the light-airplane industry was content to produce propeller-driven aircraft, Lear introduced the Lear Jet, which continues to be the world's most successful business jet and a benchmark in the field.

In 1967, before the auto industry was particularly worried about exhaust pollution, Lear invested $17 million of his own money to develop an old idea, a pollution-free steam bus, and came away with "blue-prints and memories."

Today, with jet travel the norm. Lear is about to unveil an airplane that synthesizes both very old and extremely advanced technology, a propeller-driven plastic plane.

Nothing like it has ever gotten off the ground.

The plane is unmistakably Lear. From the rakish, sharp-edged nose to the contoured fuselage, it bears his signature.

Otherwise, the Learfan defies easy description. The traditional aluminum skin is replaced by a lightweight composite material called Kelvar, which is baked and molded in huge autoclaves.

And rivets - it took 30,000 to hold the Lear Jet together - are gone. The skin is absolutely smooth, with main sections bonded together with expoxy glue.

The Learfan is powered by a pair of gas turbine Lycoming helicopter engines, turning a single four-bladed rear propeller, a design that takes aircraft back 75 years to the "pusher" prop of Orville and Wilbur Wright.

The wing is low and passes aft of all passenger seats. The tail is an inverte "vee," which Lear claims add stability and affords ground protection for the propeller.

Lear says the Learfan is the safest plane ever built. He claims that, while the two inboard engines ensure against engine failure, the Learfan easily can take off and land on just one. To underscore his point, Lear says he will fly the plane on one engine from New York to Paris on June 26, 1979, his 77th birthday.

He claims the aircraft is so reliable that it can fly on one engine without refueling for up to 15 hours. He says this range makes feasible use of the Learfan as a reconnaissance aircraft in patroling the new, 200-mile fishing limit or as a flying television transmission station.

Although the Learfan has its engines in the rear, it is hardly the Volkswagen of airplanes. The list price is $925,000, complete. But the Lear organization said it will sell the plane on its economy in the air.

Empty, the 8-passenger craft weighs only 3,400 pounds, less than an intermediate-size automobile. According to the company's performance specifications, the Learfan will cruise at 400 miles an hour while consuming fuel at the rate of 12 miles a gallon - 25 percent of the fuel consumption of the Lear Jet. Officials say the Learfan will be able to fly coast to coast on 250 gallons of fuel compared with 1,200 for large business jets.

But will executives forsake their jets for economy alone? Lear says they will, particularly for a high-performance airplane like his Learfan. He says business jets were designed when aviation fuel was relatively cheap, but now both public and stockholder pressure is going to force large companies to re-evaluate their need for sleek, but expensive jets.

Moreover, Lear says that a recent Securities and Exchange Commission decision declaring that private use of company planes must be reported as income - and thus is taxable - makes an economical aircraft that much more attractive.

LearAvia expects Federal Aviation Administration certification of the Learfan by January. Lear says his company will be producing 1,000 a year by 1983.

After a decade in the aviation doldrums, the Lear organization is convinced that it again is on the leading edge of aircraft technology. "This heralds a new generation of airplanes," says Lear. "It will set the style that other companies are going to have to go to. But by the time they get their first plane in the air, we're going to be on to other projects." LearAvia has a four-place Learfan on the drawing board with a projected sales price of $250,000, and a 30-passenger commuter craft planned, which it hopes to have in production by 1980.

"I'm not a tinkerer," says Lear. "In fact, I'm not very good with tools. My outstanding ability is to recognize a market and to fill it."

Lear found his first big market in 1925 when he designed a car radio that would fit into a car. "That was so people wouldn't have to rush home and listen to Amos and Andy," he said.

His boss, Paul Gavin, was against it. "They'll never be allowed in cars; there'll be a law against it," Gavin argued. But within a month, Lear and Gavin formed the Motorola Co.

Those were heady days for young Lear, who fell in and out of three marriages before settling down in 1942 with Moya Olsen, daughter of vaudeville comedian Ole Olsen. For Lear's 50th birthday, she gave him a needlepoint pillow inscribed with the names of his former mistresses.

Electronics brought Lear into aviation, where he developed such devices as the direction finder and the automatic pilot. Lear holds 300 U.S. patents. Electronics also took him out of the aircraft business. The popular 8-track car stereo tape player was a Lear invention. But continuing losses in a subsidiary division forced him to sell his Lear Jet Corp. to the Gates Rubber Co. in 1967, Gates continues to manufacture the plane under the name Gates/Lear Jet, and it continues to be the best-selling executive jet, with double the sales of its closest competitor.

Gates paid Lear $28 million for both the jet and electronics divisions. Within a year, Lear bought the surplus 3000-acre Stead Air Force Base near Reno, buildings and all, for $1.3 million.

Reno was then playing a very dreary second fiddle to Las Vegas, its glamorous sister city to the south, but the absence of both state income and inventory taxes quickly is turning northern Nevada into the warehouse center for neighboring California industries.

Lear recently sold off a hundred-acre section of the Stead property to J.C. Penney for its major West Coast warehouse. Lear will not disclose the exact price, but it is understood that he more than doubled the amount that he paid for the entire property.

Lear is depending on land sales of both industrial and residential development from the Stead property to carry his privately held Lear-Avia enterprise - and the Learfan.

From the factory, it's five miles to the nearest cafe at Bordertown, a cowboy bar where rows of slot machines divide the restaurant from a liquor store.

But the Lear staff generally eats in, with the boss often preparing his patented Learburgers. Lear adds some special ingredients to the mix, but the patties are reported to be of a rather conventional design.

LearAvia is littered with reminders of Lear's past economic adventures. Two bright red and yellow city buses, his steam coaches, sit idle in the company yard. The machines were powerful, quiet and emitted little air pollution, but they actually used more diesel fuel than conventional buses.

A three-quarters-built Indianapolis 500 racing car, which Lear is going to equip with a steam engine, is pushed against a partition behind the Learfan.

Next to it sits a perfectly restored Mercedes gullwing coupe, covered by a white sheet, "Mr. Lear doesn't drive it any more," confides an aide. "He can't keep it under 55."

Lear uses the word iconoclast a lot to describe both himself and his new plane. "When you're an iconoclast, you have to be thre in front," he says of himself.

"This is an iconoclastic airplane," he says of the Learfan. "Far more advanced than my jet."

Lear is more a doer than a talker, but he gets his point across. "This airplane is not the result of my genius, but more of other peoples' genius," he says. "I can recognize genius in other people and use it. That's better than being a one-horse genius."

No rich recluse, Lear openly welcomes visits from friends and strangers alike. He'll talk by telephone to a newspaper reporter while sitting on the toilet. His aides admit that one of their most difficult tasks is screening their boss from the constant stream of would-be inventors who seek his advice and cooperation.

Often Lear's willingness to test a new idea pays off. Within the past month, LearAvia has made a decision to develop an electronic gyroscope that contains no moving parts, a catalytic converter for automobile exhausts that does not need expensive platinum, and a carburetor that Lear claims increases fuel economy enormously.

All these ideas were brought in by inventors outside the Lear organization. "People come to me because others would run them out," explains Lear. "Not me; I give them a good shake and sometimes it just works out."

Lear admits that he shuns outside investors, bank loans and government interference. "I'm after accomplishment, and I'd rather do something worthwhile than have somebody say that son of a bitch is a millionaire. He'd probably never find me with more than $100 in my pocket.

"I do support some causes," he says. "Like the Republican Party."

Lear runs his company like he flies his planes, from the left side, the pilot's seat. "It's my own money," he says. "And I can do what I want with it."