Country of origin:

Australia

Description:

Single-seat agricultural monoplane

Power Plant:

One 108 kw (145 hp) de Havilland Gipsy Major 10 Mk 1 four-cylinder in-line air-cooled engine

Specifications:

History:

During the 1960s some conversion work was carried out on a number of de Havilland DHC-1 Chipmunks in Australia to increase their performance. Several aircraft were involved, the engines of a couple being changed to four or six-cylinder American-built horizontally-opposed air-cooled models. Aerostructures of Bankstown, NSW, was foremost in this area and amongst its modifications of Chipmunks it designed a single-seat agricultural conversion initially powered by a Gipsy Major engine, known as the Spraymaster Mk 1, but also proposed another variant powered by a 157 kw (210 hp) Continental (to be known as the Spraymaster Mk 2).  Some interest was shown in a Gipsy Major powered version and three aircraft were constructed with this engine.

The Model SA-29 was basically a completely rebuilt and modified Mk 10 or Mk 21 Chipmunk. Work was commenced by Mieczyslaw Sasin at Goulburn, NSW in June 1963, a local agricultural operator, but was moved to the Aerostructure’s facility at Bankstown for completion. It seems work performed on the fuselage of VH-AMB was rejected by the Department of Civil Aviation and a replacement fuselage was obtained.  All major components were dismantled and reconditioned.  Fatigue modifications were incorporated so that the aircraft would commence service with no flying hours recorded.

Modifications to the mainplanes included removing the root leading-edge stall warning strips, drooping the trailing-edge and replacing the wingtips with end plates. These changes reduced stalling speed to 64 km/h (40 mph) with full flap.  A small dorsal fin and two horizontal anti-spin strakes were fitted to the fuselage to assist stability and improve spin recovery. A 227 litre (50 Imp gal) hopper was located in the position of the old front cockpit; and the rear cockpit was redesigned, the seat being raised, and a turn-over truss being built in.  A Gipsy 10 Mk 2 engine showing nil hours was installed.

The prototype (VH-SJD – c/n CI-0383[1] – ex VH-AMB) was built as a joint venture between Sasin Aircraft Services of Goulburn, NSW, and Aerostructures using the engine, wings, tailplane and undercarriage from VH-AMB but, as noted above, the fuselage was not suitable, and that of an ex-New Caledonia aircraft (F-OAOL – c/n CI-0438, ex WG351) from the Tamataus Aero Club was used in the conversion. The Certificate of Airworthiness and registration were received on 1 September 1965.  It seems several pilots had been performing circuits at Goulburn on 2 September familiarising themselves with the aircraft when the aircraft ran out of fuel and the prototype was destroyed in the ensuing landing just outside the aerodrome.

The second aircraft (VH-BCA – c/n HF/46) was delivered to Bob Couper Pty Ltd of Cunerdin, WA, as was the third aircraft (VH-GEB – c/n DHB/F/370). VH-BCA operated in the agricultural role until 1969 when it was leased to the Gliding Club of Western Australia.  In July 1972 it returned to the agricultural role, based at Kellerberrin.  In October 1976 it was ferried from Perth to Mareeba, QLD where it was to be used as a glider tug but saw little use and remained at the airstrip for about eight years where its condition deteriorated. Eventually it was restored to airworthy condition by Cliff Douglas at the Chewing Gum Field at Tullabudgera, QLD and offered for sale. In more recent times it has been based at Cairns, QLD and there has been conjecture as to whether it would be returned to Chipmunk configuration.

VH-GEB, the third aircraft completed, was built for Tonair Pty Ltd of Tintinara, SA which also operated a Percival EP-9C.  It only had a short life in the agricultural role, some three months, before it was badly damaged in a forced landing at Tintinara. It was rebuilt by the Royal Aero Club of South Australia. It returned to service in 1967, and by May 1969 was operating with the Adelaide Soaring Club but was damaged again on 29 March 1970. It was later exported to the United States as N7DW where it remained as a single-seat aircraft but converted to take a 194 kw (260 hp) engine and a new canopy.

In the event the cost of conversion of the Chipmunk aircraft was too much to make it a viable proposition as a long-term conversion programme. By the time it entered service it was being overtaken by the Callair A-9 and Piper Pawnee and, like the Aerostructures’ other Chipmunk conversions, the Sundowner and the Musterer, did not proceed further.

Company advertising of the Spraymaster said “£4000 buys you…handling characteristics known and accepted by pilots throughout the world. Guaranteed spare parts backing – major assemblies on an exchange basis. Low insurance – low depreciation – low maintenance cost. Maximum pilot comfort – sliding canopy – adjustable rudder pedals – rollover truss – wire cutters – collapsing instrument panel – 85 gallon fibreglass hopper – Agavenco Pump and valve – 2-second dump – full span spray boom – and many other features to match its excellent performance.”

The Mk 2 version of the Spraymaster was not built. This model was to have a 156 kw (210 hp) Continental IO-360-D engine, a 500 litre (110 Imp gal) spray tank and a max weight of 1,270 kg (2,800 lb).  The Company also considered building a larger example to seat four, which in the agricultural role could carry one ton of superphosphate.