Unusual agplanes: Bug bombers

Flight Journal, Jun 1998 by Lert, Peter

Today, those of us who live in civilized countries tend to take things like adequate food and freedom from insect pests for granted. This hasn't always been the case, however, and it still isn't in much of the world. One of the main reasons we enjoy these benefits is aerial application-the science (and, in many cases, art) of delivering pesticides and growth enhancers directly to field crops, and even seeding the crops themselves by air. This technology has been around for quite a while, and over the years, some remarkable aircraft have been employed for the purpose.

It's hard to determine exactly when aerial application got its start While opposing forces in WW I did not publicize their efforts, it's likely that both experimented with aircraft as a means of dispensing poison gas over enemy positions. It wasn't until some years after the War that aerial application started to take off, driven both by advances in pesticide chemistry and by the availability of aircraft Predictably, this occurred in the USA Not only were machines like War-surplus Curtiss JN4 "Jennys" readily available and dirt cheap (as were replacement engines), but American mid-western agriculture-with its huge, flat fields-lent itself much better to aircraft operations (and could benefit more from them) than the cramped, irregular, stone-walled fields of Europe. (The Soviets, with equally huge fields in the Ukraine, and with millions of folks to feed in their various five-year plans, soon followed suit) The era of "crop dusters" had begun.

Why were they called "dusters"? Because, in many cases, the early insecticides and fertilizers were finely powdered materials like sulfur or phosphates-in other words, "dust" Compared to later products, these often had to be dispensed in considerable volume. Those few Jennys that first entered service were soon superseded by larger and more powerful aircraft, such as Standards and WACOs, which could carry heavier loads. Even so, the image of the times was of a biplane trailing an immense, choking cloud of dust across a field and landing nearby to reload after every few passes.

The Postwar Boom

If WW I provided the initial impetus, it was WW II and the period immediately thereafter that really got aerial application off the ground. Once again, a major impetus was the availability of suitable War-surplus airplanes and engines at rock-bottom prices. Another was the sudden return, at War's end, of thousands of trained pilots, many of whom came from farming backgrounds. These guys wanted to get back to their communities and to agriculture, but they hardly wanted to go back to plowing and hoeing. It was a case of, "How're you gonna keep 'em down on the farm after they've seen the Eighth Air Force? ...."

Perhaps the most significant change, though, was a very small itemalthough pretty good-sized, as molecules go. This was dichlorodiphenyltrichloroethane (say that three times fast!), commonly known by its initials, "DDT." Discovered by a German chemist as long ago as 1873, it wasn't recognized as a potent insecticide until 1939, but for the next 30-odd years, until its detrimental environmental effects became widely known, it was the insecticide of choice for almost every purpose. Not only did it kill just about every bug under the sun, but it did so when used in relatively small quantities (as did its various successors, like Malathion). Suddenly, aerial application became a lot more economically feasible for both farmers and applicators.

One airplane that dominated the industry during those postwar years was the Boeing PT-17 "Kaydet" trainer, known universally as the Stearman. In those simple pre-EPA, pre-OSHAheck, pre-FAA days (it was still the CAA back then) just about anyone who wanted could go to a surplus yard, latch on to a couple of Stearmans and a pickup load of spare engines, yank out the front seat, kludge in a hopper and be in business. Although there may be many exceptions, for the most part, ag pilots were (and still are) a lot more "down home" than most other aviators; they drive pickups instead of Porsches, drink beer (Miller or Bud-none of those pansy imports) rather than wine and wear jeans and "gimme" hats from the feed store rather than designer shirts. Basically, they're farmers, and anyone who has ever tried to make it in that business knows that there's not much romance in it They regard their airplanes in about the same way as their earthbound colleagues look at tractors; in fact, one of the most successful modern ag planes is even called the Air Tractor!

They're also some of the best stickand-rudder pilots around. Aerial application is, perhaps, the last bastion of true seat-of-the-pants flying. No wonder those WW II fighter jocks liked it; it was just like those low-level sweeps across northern France, but no one was shooting at you, except maybe on a rowdy Saturday night.

Over the next few years, most ag planes remained "variations on a theme by Stearman," with the main additions being ever bigger engines and greater load-hauling capabilities. It wasn't long before the 220hp Continentals were replaced by 450hp Pratt & Whitney R985s-in those days still available very cheaply-to make "Bull Stearmans."