Kingsford Smith Aviation Services of Bankstown Sydney undertook to convert the CA-6 Wackett Trainer into an agricultural aircraft in the late 1950s. After the completion of five of of these conversions, the Company was informed by the Department of Civil Aviation (DCA) they would no longer certificate agricultural aircraft with glued wooden wing structures.
A new company, Yeoman Aviation Pty Ltd was formed in August 1958 to develop the basic Wackett design into a modern agricultural aircraft designated YA-1, with metal wings and tail plane, powered with a Lycoming or Continental engine. The new wing was of the same dimensions as the Wackett's minus the slots and rounded wingtips. Extensive use was made of fibre glass including the engine cowls, lower fuselage, upper fuselage turtledecking and dorsal fin. A 145 gallon (450 litre) fibre glass hopper was installed, and stainless steel augmenter exhaust tubes became a distinctive feature of the new aircraft.
The DCA having approved it's entry into service, the first YA-1 was flown in January 1960 with a wooden tailplane pending the building of a new metal tail plane and empenage section featuring a stabilator, swept fin and large rudder surface. DCA granted a Type Certificate for the new aircraft in June 1962.
Twenty Yeoman YA-1 Cropmasters had been constructed at Bankstown by the mid 1960s and as production proceeded the use of Wackett parts were reduced and replaced with new components. By 1966, the only Wackett components still in use was the undercarriage structure which represented only 3% of the total airframe.
A hoped for New Zealand market did not eventuate due to problems arising with franchisees, and with the Australian Government failing to grant tariff protection against imported agricultural aircraft in 1966 a move to shift Cropmaster production to the US also failed, and that left total production of the YA-1 Yeoman Cropmaster aircraft at twenty units.
For many years these aircraft operated successfully in the agricultural scene.
Currently, the Museum has the remains of several Cropmasters in storage.
Crew : 1 pilot.
Power plant : 1 x 250hp Continental I0-470, 6 cylinder fuel injected, horizontally opposed air cooled engine.
Length : 26'04'' (8.03m) Wingspan : 35'00'' (10.67m) Height : 9'09'' (2.97m)
Weights : empty - 1,800lbs (816kg) maximum - 3,530lbs (1,601kg)
Speeds : maximum - 132kt (158mph) (245km/hr) cruise - 112kt (134mph) (208km/hr)