Yeoman Cropmaster

Infobox Aircraft
name=Yeoman Cropmaster YA-1


caption=
type=agricultural aircraft
manufacturer=Yeoman Aviation
designer=C. W. (Bill) Smith
first flight=1960
introduced=1960
retired=
status=One aircraft registered in NZ
primary user=
more users=
produced=1960-1966
number built=21
unit cost=£9,425
variants with their own articles=CAC WackettThe Yeoman Cropmaster was an Australian agricultural aircraft developed from the CAC Wackett trainer of World War II.

Design and development

The type was developed by Yeoman Aviation, a company set up by Kingsford Smith Aviation Services Pty. Ltd. (KSA) to engage in agricultural aircraft production. KSA had obtained a number of Wacketts following the type's retirement from Royal Australian Air Force service and had converted several for agricultural use as KS-3 Cropmasters. The conversion involved little more than the installation of a hopper located in the rear cockpit of the Wackett.

By contrast the YA-1 Cropmaster involved major modifications to the Wackett airframe. The Wackett fuselage structure of steel tube was retained but had a 23 cubic ft. (650 litre) capacity hopper "in lieu" of the Wackett's rear cockpit and different external panels of metal and fibreglass (the Wackett fuselage was fabric covered); the Wackett's wooden wing was replaced by a new metal wing. The first five aircraft retained the Wackett's wooden tail, but subsequent aircraft had a metal tail that featured a swept-back fin and larger rudder. The Wackett's fixed tailwheel undercarriage was retained. The Warner Scarab radial engine of the Wackett was replaced by a horizontally-opposed engine, the YA-1 250 being fitted with a Lycoming O-540 engine of 250hp driving a Hartzell propeller, while the YA-1 250R was fitted with a Continental IO-470 also developing 250hp, driving a Hartzell or McCauley propeller.

The first Cropmaster, a YA-1 250, took to the air for the first time in early 1960 (sources disagree on whether it was in January or February). Twenty further aircraft were converted at Bankstown Airport before production ceased in 1966, by which time the company was known as Cropmaster Aircraft. Like it's contemporary the CAC Ceres the Cropmaster was unable to compete with more modern types of agricultural aircraft. Six of the twenty-one aircraft were the YA-1 250R model and the final three aircraft produced featured relocated main landing gear to counteract a tendency for the type to nose over on the ground. Six Cropmasters were exported to New Zealand where one example is still on the civil aircraft register. Several other Cropmasters reportedly still exist in Australia and New Zealand. One example is registered in Australia and is under rebuild at Wagga.

Four pilots were killed in Cropmasters. In 1961 at Deniliquin, Ralph Dennis ran a tank dry in Marshall's VH-MSS and spun in. In 1964 John Waddell pranged VH-BAQ near Boorowa while doing low level aerobatics. In 1965 Air-Culture's VH-CXQ, with Richard Adams flying, struck a tree whilst entering a spray run at Highbury near Narrogin. Also in 1965 Bill Pearson flying Bender's VH-RPB at Kempton went in from a hundred feet or so, just after lift-off. Non-fatal misadventures included wire strike, jammed elevators after fence strike, getting trapped in a blind gully, Hartzell propeller blade failures and nose-overs.

An intermediate type was the single Yeoman 175; this had the swept fin of later Cropmasters but retained the Warner Scarab engine. A proposed variant with tricycle undercarriage was the YA-1B, none were built. Another variant was the YA-1 285 with a 285hp Continental engine, sources disagree as to whether any of this variant were produced. At the time manufacture ceased, metal had been cut on the next evolution, this being the Cropmaster 300. The existing wing was to be retained with the span increased to 37 ft (11.28 m). The tail group was to remain unchanged. The tailwheel configuration was retained (pilots prefer) although new oleo legs to handle the heavier take-off weight were required. New plastic fuel tanks, still mounted between the front and rear wing spars, were of 21.5 imperial gallons capacity each, giving a total capacity of 43 gallons (195 lit.). Therefore, the practical working endurance remained at two hours or so. The fuselage was an all new design optimized for the topdressing role. The hopper remained in the same position but was of considerably increased capacity. Hopper load on topdressing would have varied between 12 and 17 cwt. (611/865 kg). The area from the hopper to the tail was to be of monocoque construction with an access hatch to permit loading of cargo/work equipment or (no doubt) the odd passenger. The cockpit section forward of the hopper was to be built on a steel tube frame and featured side by side seating for the pilot and a passenger (typically the landholder or the loader driver).

pecifications (Yeoman YA-1 250R Cropmaster)

Aircraft specifications

plane or copter?=plane
jet or prop?=prop

crew=1
length main=26 ft 4in
length alt=8.02 m
span main=35 ft 0 in
span alt=10.67 m
height main=9 ft
height alt=2.74 m
area main=
area alt=
empty weight main=1,801 lb
empty weight alt=817 kg
loaded weight main=
loaded weight alt=
max takeoff weight main=3,528 lb
max takeoff weight alt=1,600 kg
more general=

engine (prop)=Continental IO-470-R
type of prop=horizontally-opposed engine
number of props=1
power main=250 hp
power alt=187 kW

max speed main=133 knots
max speed alt=152 mph, 245 km/h
cruise speed main=
cruise speed alt=
range main=456 miles
range alt=400 nm, 735 km
ceiling main=
ceiling alt=
climb rate main=900ft/min
climb rate alt=4.56m/s
loading main=
loading alt=
power/mass main=
power/mass alt=
more performance=

References

* "Tiger Moth, CT-4, Wackett & Winjeel in Australian Service" Stewart Wilson. Aerospace Publications Pty. Ltd. ISBN 1 875671 16 1
* "The Observer's Book of Civil Aircraft of Australia and New Zealand" Timothy & Elizabeth Hall. Methuen of Australia Pty. Ltd. ISBN 0 454 00075 8
* original company documents and plans held by Fred Burke
* research material compiled by Allyn Eckford

External links

* http://dbdesignbureau.buckmasterfamily.id.au/aus_aircraft.htm
* http://www.kiwiaircraftimages.com/yeoman.html

ee also

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