Crop dusting expanded considerably after the Second World War with a surplus of pilots, aircraft and engines. Most crop dusting operations used the Boeing/Stearman Kaydet training biplane as it was rugged to deal with the ham fisted flying of students and it was cheap being war surplus as the US military modernized its training fleets in the postwar period. Though plentiful and relatively easy to maintain, a fully loaded Stearman for crop dusting was in most cases underpowered. One of the qualities that made the aircraft so ideal for training was that it required a lot of coordination to minimize its yaw tendencies. It wasn't unusual for a Stearman student to find operational combat aircraft less demanding to fly! That's not to say it was a difficult aircraft in the training environment, but if you were to add a heavy load of chemicals and associated spray equipment, then the Stearman was definitely a handful for crop duster pilots who were flying just a few feet above the ground and then having to climb to avoid treelines and whatever obstacles surrounded most agricultural fields. In 1956, two members of Grumman Aircraft's preliminary design group, Joe Lippert and Arthur Koch, had been touring the Gulf Coast talking to oil industry executives and operators on their requirements for proposed amphibian they were considering. They had a second aircraft in mind as well, a purpose-built crop duster, but the amphibian was their priority at the time of their visit to the Gulf Coast. What Lippert and Koch found was that there was a broad range of needs by the oil industry that they weren't sure a single design could meet all the demands they discussed with prospective customers. Shelving the amphibian project, they then visited farming communities and observed crop dusting operations with considerable interest. Discussions with crop duster pilots revealed some of the problems pilots faced with the near-ubiquitous Stearmans that were the bulk of the crop dusting fleet of the day. While Grumman was not alone in its considerations of a custom-designed crop dusting aircraft, they certainly chose a different design philosophy than other aircraft manufacturers like Piper and Cessna took in their crop dusting designs.
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| The Smithsonian's Gruman Ag-Cat (NASM Udvar-Hazy Center) |
Lippert in particular was fascinated with how crop duster operations were getting war surplus radial engines for only $25 to replace the existing worn out Continental R-670 seven-cylinder radial engines for their Stearmans. He astutely realized that the best approach for Grumman was a design that used the 220-hp radial engine as they were inexpensive and plentiful on the aftermarket. This would make acquisitions costs more reasonable and potential owners and operators already had experience operating and maintaining the R-670 engine. Lippert and Koch went back to Leroy Grumman and presented their preliminary specification for what would become the Grumman Ag-Cat. However, Grumman was tied up with a lot of military business in the later half of the 1950s and Grumman told the two men that the new project would have to carried out on a shoestring budget. An empty hangar was secured as a workshop and design space along with tooling that was to be scrapped that they thought might be of use. The entire engineering team for the aircraft consisted of only eight people, two of which were Joe Lippert and Arthur Koch. They borrowed craftsmen from the production floor as needed based on who was available- most of these craftsmen were on the verge of retirement but their skills dating back from the 1920s and 1930s would prove valuable to the Lippert and Koch. While the number of craftsmen working varied based on who was available, it usually averaged about thirty individuals. With the craftsmen working right next to the engineers and draftsmen, a tight-knit group that hearkened back to the Grumman's early days formed.
Unusually for an aircraft program, the design and build of the Ag-Cat began simultaneously on 30 October 1956. Some of the workers came in on weekends and evenings on their own time to help with the project- after all, the last Grumman biplane was the F3F from the 1930s, so there was considerable interest among the "old hands" at Grumman in the Ag-Cat project (which had yet to get the Ag-Cat name at the time). The fuselage mock up was built in Joe Lippert's garage much to his wife's consternation. Ideas from the mock up then went to the hangar in the morning for incorporation in the aircraft as it came together. To keep things simple, a welded tube fuselage was used with removable aluminum panels to allow the interior to be washed out of any chemical residue from crop dusting. The two wings were staggered with the lower wing 35% aft of the top wing to give the aircraft very benign stall characteristics. This way one wing stalled before the other which insured the pilot would always have some level of control in a stall situation. The four wing panels- left and right top and bottom wings, were all interchangeable which eased maintenance and production costs. The aileron on a top wing panel became a flap if that wing panel were used on the lower wing. The nose sloped downward to improve the pilot's vision during low level flying and the airspeed indicator and engine tachometer were put right at the pilot's eye level to avoid having to look down at the instrument panel. The fuselage structure around the cockpit was designed to absorb a 40G crash- given that 10% of crop duster pilots crashed each year of their careers, making the aircraft survivable in the event of a crash was to be a prime selling point- in fact, from the first delivery in 1959, nine years elapsed before the first Ag-Cat crash. The chemical hopper was installed in the fuselage ahead of the cockpit right at the center of gravity to prevent there being any shifts in the center of gravity as the load was expended. The hopper had a 217 gallon capacity for liquids or 1,200 lbs for dry product. The price was established at $12,995 without the engine and propeller, $13,995 if a power plant package was factory installed.
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| N10291, the Grumman Ag-Cat prototype (Wikipedia/Rene Francillon Collection) |
The first flight took place on 27 May 1957, just seven months after design/fabrication of the prototype, N10291, began! Lippert and Koch requested that all the workers who worked on the project bring their wives to the first flight- as many of them had worked additional hours on top of their existing jobs on the project, they thought that the wives should see "the other woman" in their husbands' lives!
With a successful first flight that revealed no major issues, the second prototype joined the test program a month later. Grumman himself invited crop duster pilots from around the country to try out the prototypes and every single one was enthusiastic about the aircraft's handing and tight turning capability given that most crop duster pilots that stalled did so during turns to make another pass. The two prototypes were then taken on a nationwide tour by Lippert and Koch with over 150 pilots trying out the aircraft. One of the crop duster pilots that tried out the aircraft, Dick Reade, suggested the name Ag-Cat to the Grumman team as it was in line with Grumman's naming of its fighter aircraft with feline names (Dick Reade's name is below the cockpit of the Ag-Cat on display at the National Air & Space Museum's Udvar-Hazy Center). While on tour in Texas, Joe Lippert began to take flying lessons and on the day he earned his pilot's license, the first thing he did was try out the Ag-Cat- one of those few occasions where an aircraft's designer got to fly their own aircraft- common in the early days, but increasingly rare as aircraft grew in complexity and performance.
Leroy Grumman had planned on building the Ag-Cat at the Bethpage facility on Long Island in the event that military sales slowed, but this wasn't to be the case and space was lacking for the production of the Ag-Cat. Grumman had the entire production sub-contracted to Schweizer Aircraft in Elmira, New York, who had the production space and the experience in building welded tube aircraft from their long line of gliders. The first production Ag-Cat was delivered in 1959- Schweizer would build 1,730 Ag-Cats from Grumman until 1980. In 1981, Schweizer purchased the design rights outright from Gulfstream (which was the spin off of Grumman's civilian aircraft business) and would build another 617 Ag-Cats until production ended in 1995. Over its production life, more powerful engines and even turbine power was offered which allowed even greater load carrying capability. In 1995, the Ag-Cat Corporation of Missouri purchased the design rights from Schweizer and a further five Ag-Cats were built before they went bankrupt. A large Ag-Cat operator in Arkansas then bought the design, but I haven't been able to determine who currently holds the design rights to one of the most iconic agricultural aircraft. I did come across an online article from 2011 in the Columbus Telegram in Nebraska about an individual named Jared Storm who owned an agricultural flying service and was in negotiations at the time about relaunching Ag-Cat production at David City Municipal Airport in Nebraska (93Y), but haven't found anything further from that news item. If any of my readers has any information, please do add it in the comments section of this article.
Further reading:
Sources: Ironworks: The Story of Grumman and Its Aircraft by Terry Treadwell. Tempus Publishing, 2000, pp 160-164. The Smithsonian National Air & Space Museum's entry on the Ag-Cat (http://airandspace.si.edu/collections/artifact.cfm?object=nasm_A20080395000).
Interesting story. I never knew about the origins of this design.
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