Crop-dusting was an often hazardous occupation, until a maverick entrepreneur and pilot designed the right airplanes for the job.
“It’s the last frontier in aviation,” Leland Snow told an interviewer in 1966. “You do your own flying. And you don’t have to answer to anyone except a farmer if you goof on a job. The ag pilot has more freedom than anyone else in the air.”
In an era when astronauts were striving to reach the moon, Snow blazed a lower-altitude frontier: agricultural aircraft, more commonly known as crop-dusters. A precise, efficient flight path eight feet above the crop canopy was Snow’s consuming interest and lifetime endeavor.
Over a 60-year career, Snow conceived 30 original designs of agricultural aircraft, beginning in the 1950s with the Snow Aeronautical S-2, the first purpose-built ag-plane manufactured for commercial sale. He fast-tracked research and development of agricultural aircraft and standardized build quality. He tirelessly upgraded new models with improved efficiency and increased safety. In 1970, Snow founded Air Tractor, the Olney, Texas-based company that now dominates the global market for agricultural aviation.
“He had a passion, and he had a mission,” says Kristin Edwards, Leland Snow’s daughter and a vice president at Air Tractor. “He never wanted to just get a job at some aviation company and work nine to five.”
Early Experiments
The U.S. Department of Agriculture had begun using aircraft in 1919 to scout for outlaw cotton fields—part of an effort by the state of Texas to prevent the spread of pink bollworms from Mexico. But entomologists were quick to recognize the potential of airplanes for dispensing insecticides: two people in a cockpit could accomplish in a few minutes what would otherwise require several people using handheld sprayers over a period of days. And an aircraft could more effectively reach the tall canopies of orchards.
Initial experiments with crop-dusting (so-named because the insecticides were typically dry powders) relied upon surplus World War I aircraft, notably the Curtiss JN-6H and the Airco DH.4. The very first crop-dusting experiment was conducted 100 years ago in Ohio by U.S. Army pilot Lieutenant John A. Macready, who flew a modified JN-4 to release lead arsenate dust over catalpa trees to kill sphinx moth larvae.
But it soon became clear that, even with clever tinkering, these aircraft weren’t up to the task. They weren’t powerful and stable enough to be used safely at the low altitudes required for agriculture. And they were too fast for the optimal spread of insecticide powders—a problem that even inspired brief experimentation with dirigibles as a slower-moving alternative. “We cannot get pilots from our Air Service to fly under such conditions,” a Canadian entomologist lamented in 1923, regarding the dangers of crop-dusting with existing aircraft designs. “They will not take the chances. There is great danger, and if your engine fails, a serious accident will result. Flying a few feet above the treetops is altogether too risky.”
Leland Snow (in 1956) was an independent thinker. Prior to the 1950s, conventional wisdom was that ag-planes had to be biplanes. Snow bucked that trend.
The ideal crop-dusting aircraft would need to fly at more moderate cruising speeds while also being capable of steep climbs to avoid obstacles. “It should have good load carrying capacity both from the standpoint of weight and cubic capacity, which should be located as near the center of gravity as possible,” entomologist C.E. Woolman once wrote in a letter to an aircraft designer.
By 1925, the Huff-Daland Company in Georgia had morphed an existing Petrel 5 biplane into a configuration called the Duster, which could fly at low speeds close to the ground and was equipped with a large hopper for chemicals and spraying equipment. (A restored Huff-Daland Duster will go on display in the renovated America by Air gallery at the National Air and Space Museum in Washington, D.C.) The airplanes were never sold commercially, but the private fleet eventually totaled 18 as service extended across southern and southwestern farmland.
But by the time Leland Snow was born in Texas in 1930, Huff-Daland was transitioning into carrying mail and passengers—it would later become Delta Air Lines—and most crop-dusting planes were still relics from World War I.
In the mid-1920s, the Huff-Daland Company modified an existing Petrel 5 biplane into a configuration called the Duster. In 1968, the aircraft became part of the Museum’s general-aviation collection.
Born to Fly
Growing up in the Rio Grande Valley, Snow had always had his eyes on the sky. He built balsa-wood model airplanes. He took flying lessons and soloed on his 16th birthday. After high school, Snow bought a wrecked single-engine Aeronca Chief for $200 and rebuilt it in the family garage. He flew it from his Harlingen home to Texas A&M, where he began classes in aeronautical engineering in 1948. During his sophomore year, Snow’s father died and finances were scarce. When he heard about seasonal crop-dusting jobs, he obtained a commercial pilot’s license to qualify.
After World War II, surplus training aircraft, such as this Boeing-Stearman biplane, were modified for crop-dusting.
During this time, thousands of surplus trainer aircraft manufactured during World War II were available for as little as $250. Combat pilots who had learned to fly with the Boeing-Stearman Model 75 and the Piper J-3 Cub were now flying modified versions of these airplanes over America’s farm fields.
While flying a Cub, Snow noted inherent shortcomings in its performance. “I very quickly became aware of the fact that an airplane designed specifically for agricultural work was badly needed,” he wrote in his 2008 autobiography, Putting Dreams to Flight. The Stearman biplanes, in his view, were also sorely lacking. “With these thoughts in mind,” he recalled, “I begin laying lines in my spare time for the design of my first airplane, the Snow S-1.”
A pilot fills his Boeing-Stearman biplane’s hopper with agricultural lime to spread on fields.
“Early on, I think Leland just knew that he could build a better ag airplane,” says Pat Kornegay. A veteran south Texas ag operator and former president of the National Agricultural Aviation Association, Kornegay has flown all models of the Snow Aeronautical S-series and knew Snow well. “Prior to the 1950s, the conventional wisdom was that an agricultural plane had to be a biplane,” he says. “Leland was the guy who bucked that trend and cut straight to the monoplane.” Monoplanes improved forward visibility because “you don’t have struts and other things sticking up,” says Kornegay.
“No preliminary engineering computations were done,” Snow wrote of the S-1 prototype in his autobiography. “I merely operated on the premise that, since it looked just like a big model airplane, I’d proceed accordingly.” Fundamentals of the wood-and-fabric structure included a non-tapered wing directly attached to the base of the fuselage for superior strength, plus a more elevated pilot’s seat for a wider-angle perspective. First test flights of the S-1 occurred in 1953, and the Federal Aviation Administration issued Snow an experimental license.
Nicaraguan crops attracted idle U.S. ag pilots to Central America during the off-season. Snow first dusted there in 1952, flying a modified Piper PA-12.
Two years later, he flew south in his Snow Aeronautical S-1. The 220-horsepower, low-wing monoplane prototype was an odd duck among the flocks of expatriate Piper Cubs and rejuvenated Stearman biplanes. But the S-1 excelled by carrying the same load of insecticide as a 450-horsepower Stearman and at a lower operating cost. Enhanced downwash from the low wing applied dust more accurately with deeper penetration into crops. Nicaraguan ag operators began requesting this strange-looking airplane to dust their fields.
Quantum Leap
Snow began diverting profits from the experimental S-1 into design and construction of the S-2. In a rented space in downtown Harlingen with two employees, he conceived the more refined, all-metal S-2, which was powered by a 220-hp Continental engine. At the 1955 Texas Agricultural Aviation Association Convention, his demo flight in the S-2 included dispersing 1,100 pounds of dust and pulling concise aerial turnarounds (known as “ag turns”) at the end of each swath. Upon landing, a group of ag operators awaited, eager to put $500 deposits on the new airplane.
“It was a quantum leap,” says Kornegay of the S-2. “It had more power, it had more capacity, a much better swath, and it was more comfortable.” And, he says, “it could outwork two Stearmans.”
FAA certification of the S-2 required static load tests of critical structure. Since Snow lacked advanced testing methods in his modest Harlingen shop, he improvised his own DIY protocol: He stacked 280 50-pound bags of insecticide atop the S-2 wingspan, tip-to-tip, applying 14,000 pounds of stress to the wing structure—the equivalent of 4.2 Gs in flight. A few rivets popped as the wing flexed, but the structure survived. Snow likewise applied the bag method to the horizontal stabilizer and the elevators.
When a wing sheared off in a later high-speed dive test (the defect was traced to a misplaced decimal point in wing-stress calculations), Snow had to bail out and the S-2 prototype was destroyed. Local Harlingen banks got nervous and cut off financing.
Snow, next to his S-2D, in 1965. ”It’s strong as hell, carries more load than a Northrop F-5, and can remain over a target area for more than four hours,” he told an interviewer.
However, the north central Texas town of Olney was soliciting new industry to boost the local economy. Snow met with the chamber of commerce and prominent businessmen. Funding was arranged to relocate Snow Aeronautical to Olney and continue production in a vacant hangar at the airport. Leland’s manufacturing tools were transferred from Harlingen north in a convoy of cattle trucks aromatic with cow manure. Two flatbeds carried a pair of unfinished S-2B fuselages, displayed on Main Street for Olney citizens to ogle. Certain locals expressed doubts about this youthful entrepreneur wearing the worn leather flight jacket.
For safety’s sake—and probably appearances, too—it was suggested that Snow give up the war-surplus Harley-Davidson motorcycle that was his principal mode of transportation around town. He declined.
It’s Just Business
While Leland Snow advanced the low-wing monoplane, the Grumman Aircraft Engineering Corporation, famed for legendary World War II fighters, instead doubled back into biplane design. Grumman’s concept, the Ag Cat, was based on a rugged, over-built airframe integrated into the biplane platform to form a highly durable, safe agricultural aircraft.
With about 1,800 of the more than 2,600 Ag Cats manufactured between 1959 and 1980 still in use today, worldwide—plus the best pilot safety record in ag aviation—the statistics speak for themselves. Yet Pat Kornegay, who flew both Ag Cats and Air Tractors, feels any rivalry with Snow’s designs was ultimately a non-event. “As we became more focused on operational efficiency and spray-pattern quality, the contest was conclusively over,” he asserts.
Piper Aircraft, another major aviation brand name, entered the ag plane sweepstakes in 1959 with the PA-25 Pawnee, a high-volume Snow competitor initially priced at just $9,000. Piper hired Fred Weick, a Texas A&M aeronautical engineering professor, to design the low-wing, single-seat monoplane. (Coincidentally, Snow was one of Weick’s students.) Weick had earlier constructed a proof-of-concept monoplane prototype, the AG-1. He incorporated many of its features into the Pawnee, including constant chord wings transplanted from Piper’s Super Cub model, an elevated cockpit for superior visibility, and welded steel tube and fabric construction.
For his part, in order to stay in business, Snow was eventually compelled to incorporate and take on partners. “He did have some financial failures,” says Snow’s daughter, Kristin Edwards. “Initially, he didn’t really pay attention to the business side of things. I think he finally realized then that making money is also important.” The self-made, single-minded visionary was now obliged to consult multiple partners before making decisions in a company he himself had founded. Tensions arose almost immediately. In 1965, realizing their relationship was dysfunctional beyond repair, Snow and his partners arranged to sell Snow Aeronautical to Rockwell-Standard. The deal included hiring Snow as vice president and general manager of the newly established Olney division of Rockwell Aero Commander.
From the outset, Snow’s maverick nature was not a good fit for Rockwell’s multi-level corporate bureaucracy. The company’s convoluted accounting procedures also made it difficult for his small Olney division to show a profit. New designs nevertheless continued to flow from Snow’s drafting table, including the S-2R—eventually to be known as the Thrush.
It was to be the largest and—at $40,000—the most expensive design yet, featuring a 400-gallon hopper, electric flaps, and stainless-steel panels on the underside of the fuselage. The Thrush also has safety features that Snow had been developing in previous S-2 variants. He had once characterized the pilot’s precarious position between the engine and the dust hopper as the “meat in the middle of a sandwich” in the event of a crash. So Snow moved the cockpit behind the hopper and the engine.
Safely making steep climbs and sharp turns are hallmarks of an effective ag-plane—capabilities that Snow included in his designs.
“Another thing Leland introduced was sealing the cockpit,” says Kornegay. “In the Stearmans, the Grumman Ag Cats, and other older planes, your feet were sitting on rails and there was no floor in the cockpit. Any migrating dust or chemicals accumulated in the cockpit, and pilots would end up covered with it.” Alterations Snow made to the S-2 configuration were: “Basically the very first example of what we’re all still flying today,” says Kornegay. “You’ve got a powerful engine up front, then the hopper, and then the pilot behind it all, safe inside a sealed cockpit.”
Prior experience had convinced Snow that a proposal for this expensive new model would draw a lukewarm response from Rockwell at best. “In view of this,” Snow wrote in his autobiography, “the simplest solution seemed to be not to tell them about it.”
The Flying Tractor
The Thrush prototype was assembled in a former National Guard armory as the factory in Olney had not yet been built. When Rockwell executives visited, the finished prototype was shoved to an inconspicuous spot at the far end of a line of S-2Ds. “We kept the project hidden from management until the airplane was flown,” wrote Snow. “And even for some time after that.” Successful first flight tests commenced in December 1966. Deliveries of the new Thrush to customers began in early 1968. By the end of that year, the S-2D was phased out and the Olney factory was producing the Thrush exclusively.
For 18 months, Snow put in 10-hour days, six days a week, designing the first Air Tractor. Working by himself, he generated over 600 drawings and 700 pages of engineering reports required for certification.
Rockwell management then intervened with bad news. To consolidate aircraft production, the Olney factory would be shut down and manufacturing relocated to an Aero Commander facility in Georgia. Rather than leave Texas and accept a demotion and pay cut, Snow opted to resign in March 1970. Since production of the S-2 began in 1958, the Olney factory had rolled out 523 agricultural aircraft, including 100 Thrushes.
After cleaning out his desk, the very next morning Snow rented a one-room office in the Oil & Gas building in nearby Wichita Falls and set up his drafting table. “Tiny as it was, I felt like I was in heaven,” he wrote of his windowless workspace. By that afternoon, he was mulling over what company name to put on engineering drawings. The name he freehanded on his first drawing that day was “Air Tractor.”
“Leland knew exactly what he wanted to do,” says Jim Hirsch, CEO of Air Tractor today. “He already had specific design ideas in the back of his mind. He was smart enough from a business standpoint to not begin that work until after he had left Rockwell—so it would be his entirely.”
For 18 months, Snow put in 10-hour days, six days a week, designing the first Air Tractor, designated the AT-300. His initial goals were simple: make it light and keep costs low. Working by himself, he generated over 600 drawings and 700 pages of engineering reports required for certification.
From the outset, continuous improvement was inscribed in Air Tractor’s DNA. Fuselage configuration with cleaner lines and a lowered frontal area minimized drag. Turbine engines with ever more horsepower supported shorter loaded takeoff distance and faster climb response. Extending the rear fuselage segment enhanced aerodynamic stability, while the strict rectangular wing shape conferred forgiving stall characteristics, as well as producing maximum downwash to optimize spray deposition.
Snow’s longstanding concern with ag aviation safety also evolved during his time at Air Tractor. To protect the pilots who fly the AT-300, Snow designed two notable crash-protection features: a cockpit roll cage constructed of steel (similar to NASCAR requirements) and a wearable inflatable air bag restraint harness. Air Tractor also segregates fuel lines and electrical wiring to reduce fire hazard.
The first Air Tractor test flight with Snow himself at the controls took place in September 1973. The AT-300 prototype soon debuted at the National Agricultural Aviation Association Convention and, in April 1974, the first model was delivered to a buyer. “We did all this with only four employees and me,” Snow recalls in his autobiography. “And we did it for $175,000.” Snow also invested $60,000 of his own cash.
The original Air Tractor evolved into the AT-301, with a 600-hp Pratt & Whitney R-1340 radial piston engine. Meanwhile, Rockwell Standard’s Thrush production had by then been sold to Ayres Corporation based in Albany, Georgia (Ayres shut down in 2001). Snow designed the turbine-powered Air Tractor 502—with a 500-gallon spray capacity—as a head-to-head competitor with the Ayres Thrush which, ironically, he had designed at Rockwell.
Snow was always watching the horizon for the next advance. The development of lightweight, fuel-efficient turbine aircraft engines had been in his sights since the mid-1970s. Air Tractor was the first ag-plane manufacturer to offer factory-installed turbine powerplants beginning with the AT-302 in 1977. Today, all Air Tractor models are powered by Pratt & Whitney turbine engines.
“Each new model was a growth variant,” Hirsch says of the Air Tractor fleet. “Each offered some improvement: a bigger hopper, different aerodynamics, a new powerplant.” Today, while the big Air Tractor 802 (derived from a larger model built for fighting fires) comes close in sales, Hirsch says, “the 502 still remains the most popular agricultural airplane in the world—period. It’s the right size. It fits more operations.”
Hirsch recalls Snow’s hands-on approach: “He was certification test pilot on the 802A. He continued to fly well into his 70s. Sometimes he’d just grab a helmet and go out to the flight line and take an Air Tractor 502 or 802 around the patch.”
In 2011, Snow died at age 80 while out for a Sunday morning run.
“If there was a Mount Rushmore of agricultural aviation, Leland Snow would have to be on it,” says Andrew Moore, chief executive officer of the National Agricultural Aviation Association, which is based in Alexandria, Virginia.
Moore recites figures that reveal the extent of one man’s influence in the industry: There are 3,773 agricultural aircraft in the U.S. today, of which 1,658 are Air Tractors. Another 576 are Thrush models also designed by Snow. The balance are various orphaned ag models produced by general aviation companies who competed with Snow, then pulled the plug—the Piper Pawnee, the Cessna AGwagon, and the Grumman Ag Cat. “These competitors never really went up in size,” explains Moore. “Leland proved that bigger payload and more power is the trend in this business.”
Moore shares an anecdote: “I remember Leland telling me about the time he went wing-walking on an ag-plane to put a gas cap back on while he was flying over a lake in Nicaragua.”
Leland Snow made doing the impossible seem routine.
“If there was a Mount Rushmore of agricultural aviation, Leland Snow (in front of an AT-802U in 2009) would have to be on it,” says the NAAA’s Andrew Moore.
Stephen Joiner writes about aviation from his home in southern California.
In Dusty We Trust
An Air Tractor painted to resemble Dusty Crophopper heads to the Steven F. Udvar-Hazy Center in northern Virginia after landing at Dulles International Airport last August.
The Air Tractor has become a pop-culture icon, most notably in the form of Dusty Crophopper in Disney’s 2013 animated film Planes and its sequel, Planes: Fire and Rescue. Aiming for authenticity, Doug Thiel, an ag aviation operator in California, permitted Disney to record the sound of his AT-802’s Pratt & Whitney engine for the movies.
The starring role on the big screen has led to a more permanent celebrity: the National Air and Space Museum’s recent acquisition of an Air Tractor AT-400A—on display at the Museum’s Steven F. Udvar-Hazy Center—donated by Texas ag pilot Rusty Lindeman. “Rusty flew the plane on promo tours for the Dusty movies,” says Dorothy Cochrane, curator of the general aviation collection. “The aircraft’s operational and film history made it an ideal representative of agricultural aviation.”
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