“Knee-high by the Forth of July” is a saying that’s become obsolete out here in the Middle West, the heart of corn and soybean country in the USA. In fact, the corn’s usually pushing 6′ tall (1.8m) by July 4, and will often exceed 12′ (3.6m) in height at maturity. The more common saying these days (taken from the musical Oklahoma!) is “High as an elephant’s eye by the Forth of July.”
Technological improvements in agriculture have enabled much higher productivity over the past 70-80 years, with average corn yields in the US increasing from around 30 bushels/acre prior to the 1940s to 140 bushels/acre and even higher today (a farming friend is disappointed if he doesn’t get “200 bushel corn” off our excellent soil here in Illinois).
One of the tools a farmer uses to maximize yields is aerial application of herbicides, insecticides and fungicides, and this is a common sight around here in July and August as the corn has gotten too tall for ground-based sprayers. These aircraft are often referred to as ‘crop dusters,’ but that’s not accurate, as the product they apply these days is in liquid form.
I’d be remiss to not acknowledge the controversy over the use of chemicals in farming – personally, we use organic methods ourselves on our small farm, but I also recognize that large-scale grain and bean production wouldn’t be feasible without it. There are plenty of other forums out there if you’d like to debate that, so we’ll stick to the aircraft itself from here out.
The first documented aerial application happened in 1906, when a tethered hot-air balloon was used to sow seeds. The first heavier-than-air application of pesticide occurred in 1921, when a Curtiss JN-6 “Super Jenny” was used to apply lead arsenate dust on catalpa trees in Ohio to kill sphinx moth larvae. Deeming the experiment a success, Curtiss biplanes were again used to dust cotton fields near Tallulah, LA in 1922 for the control of boll-weevils. A year later, Huff-Daland Dusters, Inc. (eventually to become Delta Airlines) began offering aerial application services on a commercial basis. Unmanned aircraft like the Yamaha R-MAX remote-control helicopter are beginning to see use for spot aerial application today as the technology continues to improve.
On the cutting edge of technology are electrostatic spray systems (photo is of a ground-based system), which set up a magnetic field over the crop canopy, and the aircraft spray booms are configured with one wing’s boom having a negative charge and the other a positive charge. This is very similar to modern auto paint systems which use a similar technique to ensure thorough and even paint coverage, even in the nooks and crannies of a vehicle as it moves through the paint booth. Electrostatic spray systems are currently very expensive, but as they use roughly ⅓ the volume of spray, with substantially higher effectivity, they will certainly become more widespread in the future.
Most of the fixed-wing aircraft used for aerial application today are turboprop-powered, but one of our local applicators still operates our subject 1967 Aero Commander S-2D, powered by a Pratt & Whitney R1340 “Wasp” nine-cylinder radial engine of 1,340 c.i.d. (21.95l) displacement. Depending on which variant it is, it likely produces between 500-600hp. The engine design dates back to the 1920s and was used on aircraft such as the Ford Tri-motor, Lockheed Vega, and the North American T6 trainer. It has a very distinctive sound, so I always know when to run outside to grab photos. The S-2D can carry 400 gallons (1,514l) of product (enough to cover upwards of 200 acres), and modern GPS guidance systems can achieve 6″ accuracy on the spray pattern, which has helped dramatically reduce the number of spray drift complaints in recent years.
The Aero Commander has an interesting history, as its parent company and name have changed a number of times. LeLand Snow designed his first purpose-built crop duster in 1953 and called it the S-1, using it as his own personal aircraft for hire. A refined version called the S-2 was built around 1956, and Snow began manufacturing them for interested pilots in the area. Despite having two aircraft completed and orders for 39 more, Snow was financially strapped and needed capital to continue. After talking with city representatives and local businessmen in Olney, Texas, the townsfolk put up the cash he needed to continue, which in turn gave their town a boost in the middle of difficulties resulting from ranching and oil businesses being on the decline.
The bet made by the town paid off, and Snow produced over 370 aircraft through 1965 (by then called the Aero Commander), when he sold the business to Rockwell-Standard Corporation, staying on as General Manager at the Olney facility. The aircraft became known as the Rockwell Thrush Commander during this time, and was continually being improved. When Rockwell told Snow he would have to move to Albany, Georgia if he wanted to keep his job, he didn’t have to think long about his answer, and stayed in Texas, working on a new ag aircraft design that would become the Air Tractor.
Ayres Corporation acquired the production rights to the Aero Commander, along with the Albany facility in 1977 and produced the aircraft as the Ayres Thrush until filing for bankruptcy in 2001. The rights were subsequently sold to Thrush Aircraft, who still manufacture the aircraft today under the Thrush name in a number of specialized models.
Ag flying is demanding and fairly high risk – there have been two crashes (one fatal) in our area since we moved here 15 years ago. But it’s also one of the last old-school ‘stick and rudder’ forms of down-in-the-weeds flying one can legally do (often compared to flying a fighter jet), and I envy these pilots every summer as I enjoy my own private air show.