Grumman Ag Cat
Single-seat biplane crop duster designed by Grumman in the 1950s, the first purpose-built agricultural aircraft from a major manufacturer, and built in quantity not by Grumman but by Schweizer Aircraft of Elmira, New York: on the Smithsonian's accounting Schweizer built 2,646, most of them for Grumman. Later models added larger hoppers and PT6 turboprops, the design passed through several owners after Schweizer, and radial and turbine Ag Cats remain at work in agricultural aviation.
Why It Mattered
The National Air and Space Museum describes the Ag Cat as the first aircraft a major manufacturer ever designed specifically for agricultural aviation. It appeared just as aerial application was expanding after the Second World War, when the work still fell to war-surplus trainers such as the Stearman, pressed into service as improvised dusters. Grumman shaped the design around the job itself, consulting agricultural pilots and operating companies across the country before committing to it. The museum counts nearly 2,700 built and ranks the type among the most successful agricultural aircraft.
Design Notes
Two Grumman preliminary-design engineers, Joe Lippert and Arthur Koch, proposed the aircraft in 1955: a duster designed from the outset for the work, not adapted to it. The result was a single-seat, strut-braced biplane with a 35 percent wing stagger and a stall speed of just 67 mph, qualities suited to the low, slow turns of application flying. Its fuselage was a welded steel-tube truss skinned with removable aluminum panels, so chemical residue could be washed out after flight. The hopper sat ahead of the pilot, over the center of gravity, and the reinforced cockpit was designed to withstand a 40 g impact. All four outer wing panels were identical and interchangeable in the field, which cut the spares an operator had to carry. Power grew steadily: the original G-164 used engines of 220 to 300 hp, while the Super Ag-Cat raised that to 600 hp with a 247-gallon hopper.
Operational History
The Ag-Cat's first flight came on 27 May 1957, and a second prototype followed a month later. In the summer of 1958 the two prototypes toured the east coast, and well over 100 working duster pilots flew them and reported on the handling. A surge of military orders left no room at Grumman's Bethpage plant, so the board handed the whole program to Schweizer Aircraft of Elmira, New York, under subcontract. Schweizer's first production Ag-Cat flew in 1959. On the National Air and Space Museum's accounting, Schweizer built 2,646 Ag-Cats in total, of which 1,730 were G-164s and G-164As built for Grumman between 1959 and 1980. Wikipedia's accounting is differently scoped, counting 2,455 aircraft built by Schweizer under contract from the start of production through 1981. Variants grew in capacity over the run, up to the Turbo Ag-Cat D, whose PT6A turboprop drove a 500-gallon hopper. The type also served in uniform: the Hellenic Air Force's No. 359 Squadron flew Ag Cats for Greece's Ministry of Agriculture on crop-spraying, pest-control and firefighting work.
Afterlife
Schweizer bought the type certificate from Gulfstream, Grumman's successor company, in 1981, and introduced subsequent models with longer wings and fuselages, including PT6 turbine versions. Ag-Cat Corp bought the certificate in 1995 and built about five more aircraft; Allied Ag-Cat later purchased the design but built none. Ethiopian Airlines built 15 Super-B turbines under licence in the 1990s. Radial and turbine conversions have kept the design working: on the museum's account, most Ag-Cats remain in commercial agricultural business, with others flown for firefighting and banner towing. The Smithsonian's own example, a Schweizer-built aircraft that rolled off the line in May 1963 and was later converted to Super Ag-Cat standard, is on display at the Steven F. Udvar-Hazy Center in Chantilly, Virginia.