In 1921, in an experiment in Ohio, lead arsenate dust was spread over catalpa trees in order to kill sphinx moth larvae. The importance of this application lie not in the application, but in the means of application. For this was the first instance in which insecticides were applied by aircraft. During this blog, we will follow the development of agricultural aviation from its early techniques to the technology of today.
In the early days of agricultural aviation, the crops were sprayed by modified military aircraft under government control. For example, the 1921 flight was conducted with a modified Curtiss JN-6 Jenny flown by Lt. John A. Macready of the U.S. Army. With successful aerial applications in Ohio, the government began to concentrate aerial applications in the Southern states, primarily spraying cotton crops. By 1923 several private contractors were available for dedicated spraying operations, Huff-Daland Dusters, Inc. was the first private crop dusting contractor with its own dedicated aircraft. Huff-Daland was highly successful in that role with a fleet of eighteen duster aircraft by 1925, eventually evolving into Delta Airlines. In the 1920's the term crop dusting came into being, since all of the insecticides were dry powder applications. A two-seater aircraft, the Jenny was ideal for the crop dusting role, modified with a metal hopper attached to the side of the fuselage, the rear crewmember turned a crank which released the dust. The Jenny used in the Macready flight had a thirty-two gallon hopper. After World War II a number of surplus Stearman biplane trainers were converted to agricultural use. Until purpose built crop dusting aircraft came into use during the 1950's, many crop dusters were modified military surplus planes, cost being the major factor.
The first such aircraft was the Ag-1, developed under the guidance of Fred Weick at the Texas A&M aviation center. The Ag-1 had a thirty-nine foot wingspan and was powered by a Continental E-225 engine, which cruised between 60 to 90 mph, with a maximum speed of 115 mph. Since the Ag-1 was not a two-seat aircraft, pilots in training had to familiarize themselves with both the technical and flight aspects of the plane. The Ag-1 first flew in December 1950 and began a nationwide tour the following summer with about 650 different pilots test flying the plane. The tour was a notable success with the Ag-1, proving its value under varying conditions, though the single prototype was the only aircraft produced. Known for its ruggedness, the Ag-1 was designed as a prototype to demonstrate both the practicality and potential of aerial crop spraying. That same year, Leland Snow, the pioneer of modern ag aircraft began design work on his first ag aircraft, the S1. Once test flights were completed in 1953, Snow began dusting and spraying flights in the Rio Grand Valley and in Nicaragua until 1957. In 1958 Snow built a dedicated factory in Olney, Texas for the production of the more advanced S-2A and S-2B models. Piper also began to enter the ag aircraft market in 1952, with the introduction of the PA-18 Super Cub series. The series was designated as an agricultural model, which was equipped with a hopper. The Super Cub series made excellent trainers as they were relatively slow and easy to fly. All of these aircraft shared the characteristic raised cockpit, sloped nose and low wing which became standard for ag-aircraft design. However, Grumman reverted back to the biplane concept when it produced the G-164 Ag-Cat, a radial-engine biplane, in 1957. The 164 was the first agricultural aircraft produced from a major manufacturer, increasing standards for reliability and safety.
Farmers and ranchers utilize aerial application for a number of reasons. The most basic are to protect crops from disease, weed and pest damage, as well as deliver vital plant nutrients and seed cover crops. Aerial application can treat larger, more remote areas with less disruption to fields or where the use of ground rigs could be difficult. In addition to agricultural uses, aerial application is a valuable tool in managing forests, fighting wildfires and controlling insects. Futuristic applications of this technology could be used to feed an increasing global population and the challenges related to climate change. Though Pratt & Whitney developed the first PT6 turbine engine in 1957, they weren't utilized on ag aircraft until 1976. Turbine engines proved to be about sixty per cent more efficient than comparable piston aircraft. Safety features were updated on ag aircraft in the 1970's as well. For example, the AT-300, which first flew in 1973, was equipped with a cockpit roll cage, similar to that on racing cars. The AT-300 also had a wearable inflatable air bag restraint harness for pilot safety. The 300 aircraft also segregated fuel lines and electrical wiring to reduce fire hazards. Although the trend since the 1950's went toward the design of larger aircraft with more powerful engines, ag aircraft in the 1970's also became more efficient with the use of larger hoppers and more aircraft types incorporating turbine engines.
By the early 2010's, two technology innovations increased the effectiveness of ag aviation, the global positioning system and the advent of drones. The global positioning system or GPS, as it is known, is an accurate worldwide navigational and surveying facility based on the reception of signals from an array of orbiting satellites. When the GPS technology first became commercially available in 1993, many operators in ag aviation appreciated the potential of the device, but were deterred from using it due to its excessive cost, above $10,000 per system at the time. Those pilots using GPS were achieving such a great increase in crop efficiency due to its use that twenty-five per cent of crop sprayers were using it at the end of its first year of operation. It was so accurate that it stemmed many of the objections to aerial applications from environmental groups at the time, encouraged by the publication of Rachael Carson's book Silent Spring in 1962. The use of GPS is as common to ag aviation today as the use of turbine powered aircraft. While ag aviation is tasked with the ever expanding need of feeding the global population, it is clear the factors of cost, reliability and viability are concerns for both current and future crop delivery systems. Current ag drones are easily as efficient as ag aircraft of a few decades ago. While unmanned crop delivery systems have been in use for a number of years, the question remains: are they merely an aid to ag pilots, or a replacement?