ARGYLE, Minn. (AP) - The sight of a banged-up Thrush S2R ag plane sitting unused at an Arkansas airstrip may not stir up any emotion in most people, but to Lindley Johnson's eyes, it is a bird that can take to the skies again, faster and more reliably than ever.

He is the owner and president of Johnson Airspray Inc., a small but successful family firm near Argyle that takes worn-out or banged-up ag planes and completely refurbishes them, hangs freshly overhauled Walters turbines on their beaks and then sells them for about half the price of a new one.

They call their planes "Walters conversions," but to the ag-flying public, they are known as "Johnson conversions." The planes spray crops throughout the Red River Valley, various states of the Union, and even in Australia.

Johnson began flying as an aerial applicator in 1959. In 1973, he partnered with aircraft mechanic Rodney Peterson, and they began buying used two-seat Bell helicopters to convert into ag sprayer platforms.

"We bought them military surplus and then built them up," Johnson said. "They were just the small ones like the G3B1s" bubble-canopied helicopters.

They sold these to spray outfits until 1984, when Johnson bought Peterson out and renamed the outfit Johnson Airspray Inc.

Today, with Johnson children and grandchildren working at Johnson Airspray and Argyle Chemical, another of his businesses, he's a busy man. Among his offspring are ag pilots, plant managers, chemical loaders and one plane fabricator, his granddaughter, Chelsey, whom he calls "Rosie the Riveter."

In the early 1990s, Johnson decided on a major engine upgrade, called a "re-power," for his own spray plane.

"We got tired of the radial engines quitting, so we decided to go to turbines," he said.

The turbines that are available in the United States, such as the Pratt & Whitney, would sell for around $400,000, he said. The Walters, made in the Czech Republic, has a long-lived and sound reputation.

Johnson has used them to re-power several other aerial applicators' aircraft as well as his own five-plane spray squadron, based in Argyle and Grafton, N.D.

Turbines basically are jet engines that turn propellers. Planes with these engines are commonly referred to as "turboprop" aircraft. Their power plants have far fewer moving parts and therefore are more reliable and require less maintenance than the old radial piston engines, which have not been manufactured for several decades.

In aircraft engines, especially those in ground-hugging ag aircraft, reliability equates to the safety of the pilot, a key selling point for the Walters conversions.

Another is maintenance intervals. An aircraft engine's age is gauged by operating hours instead of miles driven. The Federal Aviation Administration has strict requirements for the number of hours an aircraft engine can run before it must be pulled from the plane and completely torn down and overhauled. This is an expensive proposition for any flier, including Johnson, so the longer an engine can go between overhauls, the better. A radial engine requires rebuild every 1,000 to 1,200 hours.

"With a turbine, we have to start doing something with them at about 2,500 hours," Johnson said. "So you're doubling the life. Of course, the overall costs are more for the turbine than they are for the radial, but the radials are getting spendy also."

A Walters turbine overhaul runs about $100,000, while a radial overhaul runs nearer $40,000, he said.

The Walters turbine also turns out more than 650 horsepower, a valuable commodity to ag pilots when they have to haul back on the stick to clear the trees at the edge of a field.

"You can use the whole seat, you don't have to sit on the edge," he said, laughing. "You don't have to work to keep the airplane up in the air. You're not fighting the airplane, and so you're a lot more relaxed and you don't get as fatigued."

Johnson either sells the old engine as is or has it overhauled and then sells it. Johnson is certified to install Walter turbines on Thrushes, Air Tractors and Ag Cats, and Johnson Airspray is a certified installation center for the Walters turbines.