Our aircraft is one of only two airworthy radial engine powered Grumman Ag-Cats in New Zealand. The Ag-Cat has an interesting history, which is outlined here.


ZK-CAT over Lyttelton Harbour. Photo: Alex Mitchell

The Ag-Cat design goes back to 1955 when Grumman designers Joe Lippert and Arthur Koch put forward a proposal for a new agricultural aircraft. At this time, Grumman was heavily involved in building military aircraft, particularly for the US Navy, so the idea of building an agricultural aircraft was novel. Lippert and Koch saw a need for a strong aircraft for crop dusting and spraying as there were no good purpose-built aircraft and the accident rate with surplus WWII trainers adapted for ag work (such as the Boeing Stearman) was high. The two designers asked the industry what they wanted and then proceeded to build the aircraft around a 220 horsepower R-670 Continental engine. These war surplus engines could be bought for just $25.00 each!

The original production model was built with surplus tools in a small hangar and with engineers who were on the verge of retirement. One of the unusual aspects of the construction was that the aircraft was designed and built at the same time! This started on 30 October 1956 and the first flight was on 27 May 1957. To save time, parts of the fuselage were built in Joe's garage.


An early Ag-Cat with open-cockpit and smaller wingspan


Some interesting features of the design included the fuselage being of welded chrome-steel tubing covered by removable panels so the interior could be washed out after spraying. The cockpit was built to withstand a +40 G impact. Each wing was interchangeable, as were the ailerons. The two wings had a 35 degree stagger which gave superb stall characteristics because one wing would always stall before the other and this enabled the pilot to retain control. The pilot was positioned high in the fuselage to provide excellent forward visibility, not normal for many biplanes. Purchase price in 1958 was just $13,995.00.


This photo clearly illustrates how easy the aircraft is for maintenance as all fuselage panels come off in minutes.

When the time came for the first flight, Joe asked Roy Grumman if he could invite their wives to the ceremony. This was a most unusual request but Joe explained that as all the men involved in the project had given large amounts of free overtime, they thought it would be a nice gesture so their wives could see what their husbands had been getting up to late at night. Roy Grumman agreed, so on the evening of the first flight, all the wives got to see "the other woman" in their husband's lives!

The resulting aircraft was a huge success and quickly liked by all pilots who flew it. They particularly enjoyed the slow handling capability. Due to Grumman being very busy with building military aircraft, it was decided to sub-contract construction of the aircraft to Schweizer, who completed their first production aircraft in 1959. The original aircraft had an open cockpit but this changed in 1962 as pilots wanted to be protected from toxic pesticides. Up to five different engine types were used on early aircraft but after one Californian owner fitted a 450 hp Pratt and Whitney Wasp Junior engine, Grumman and Schweizer realised this was a good combination, particularly given the increased loads that were being carried. This created the Super Ag-Cat. Some months later the wing was increased by four feet.


An early production Ag-Cat with enclosed cockpit.


One little unknown fact about the Ag-Cat was that it was considered for use in Vietnam! Options that were looked at included dropping bombs, fitting light machine guns to the wings, using it as a field ambulance with pods strapped to the wings, or operating it as an observation aircraft at extremely low level. One Ag-Cat was sent to the Army for evaluation and the pilots thought it had tremendous potential, particularly given it could turn in areas only 200 feet in diameter! However, they felt that, in the end, they could not recommend the purchase of an old-fashioned biplane to the Pentagon when they were in a jet-orientated world!

Aviation Adventures Ag-Cat was built in 1975. Manufactured by Schweizer, it is a Model 6-164A Super Ag-Cat, Serial Number 1418. It initially worked in the USA spraying crops but was then imported into New Zealand by Brian Stewart and registered here in 1997. Brian had it fitted with two passenger seats where the hopper would normally be located so that it could be used for scenic flights. It was operated by Adventure Aviation and the Rotorua Aero Club with Neville Worsley being the main pilot. In recent years, the aircraft was owned by Brent Esler and operated by Mainland Air out of Dunedin, as well as being used for banner towing over Christchurch. We purchased the aircraft in April 2009.


A close up of the 450 hp Pratt and Whitney Wasp Junior

Being a Super Ag-Cat, our aircraft is powered by a Pratt and Whitney R-985 Wasp Junior engine rated at 450 horsepower. This type of engine is also used on famous aircraft such as the Beech Model 18, the Beechcraft Staggerwing, the Avro Anson, CAC Winjeel,  the Grumman Goose, the Lockheed L-10A Electra (early version of the aircraft flown my Amelia Earhart), the Vought Kingfisher, as well as the famous de Havilland Canada DHC-2 Beaver.

Our Ag-Cat also features a number of refinements. These include longer wings than standard, smooth fuselage panels (most are corrugated), landing lights, some flush riveting, a lockable tail wheel and a tow hook for towing gliders or banners.


ZK-CAT's instrument panel


Specifications:

Engine - 450 hp Pratt & Whitney R-985 Wasp Junior
Wingspan - 35 ft. 8 in.
Wing area - 326 sq. ft.
Length - 24 ft. 4 in.
Height - 10 ft. 9 in.
Max. speed - 147 mph
Stall speed (loaded) - 67 mph (58 knots)
Climb rate - 1600 ft./min.
Fuel capacity - 46.3 gallons, 255 litres
Oil capacity - 7 gallons
Hopper capacity (when fitted) - 2000 lb.