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B1701 Aero engine, 'Harkness Hornet' No.101, prototype, 4 cylinder, designed by Donald (Don) Harkness, built by Harkness & Hillier Ltd, Five Dock, New South Wales, Australia, 1929. Click to enlarge.

“Harkness Hornet” aero engine, 1929

Made by Harkness and Hillier Limited in Australia, Oceania, 1929.

This aero engine, called the “Harkness Hornet”, is the prototype for the first Australian-designed and made engine to pass the Commonwealth Government’s stringent Department of Civil Aviation airworthiness test in 1930 and receive a ‘type’ certificate. It was designed by Don Harkness, a well known local automotive engineer, designer and racing car driver, and made at his Five Dock engineering works, Harkness & Hillier Ltd in 1929. The engine design was used in two locally made and designed aircr...


Object No.


Object Statement

Aero engine, 'Harkness Hornet' No.101, prototype, 4 cylinder, designed by Donald (Don) Harkness, built by Harkness & Hillier Ltd, Five Dock, New South Wales, Australia, 1929

Physical Description

Aero engine, 'Harkness Hornet' No.101, prototype, 4 cylinder, designed by Donald (Don) Harkness, built by Harkness & Hillier Ltd, Five Dock, New South Wales, Australia, 1929

The "Harkness Hornet" is a 4-cylinder, in-line, single overhead cam, water-cooled aero engine designed for use in small aircraft. The four cylinders are bolted to the upper portion of the crankcase suggesting that they remain separate and not incorporated in a cylinder block. The upper portion of the cylinders and cylinder head are enclosed in a sheet metal water jacket. At the front and rear, lower, of the water jacket are two blanked off openings which may have been to permit drainage and cleaning of the jacket. The upper half of the crankcase is provide with brackets for attachment to the aircraft structure. The lower half of the crankcase is of sheet metal material and serves as a lubricating oil container. Two magnetos, in red, provided the electrical input to the spark plugs. Each magneto would probably be connected to each of the four spark plugs on their side of the engine. This duplication increased the reliability of ignition, and provided improved scope to ensure that the fuel combustion process was as complete as possible. The upstanding green tube houses the drive shaft to the camshaft. The drive shaft engaged with the crankshaft through bevel gears and may have run at half engine speed (if the engine operated as a four-stroke). At the top another pair of bevel gears driove the camshaft, running the length of the engine, which actuated the individual inlet and exhaust valves through rocker arms. The silver-coloured assembly contains the air supply, fuel dispensing means, inlet manifold and cooling water inlet pipe. There are four exhaust pipes. Engine operation would have been noisy without any connection to an exhaust muffler system. The pilot would also have been subjected to the smell of exhaust gases. Fresh air was drawn into the open-ended intake tube, supplied with fuel and thence through the adjustable throttle valve (to control engine speed), before passing to the cylinders via the inlet manifold.

Bore: 120 mm
Stroke: 130 mm
Normal B.H.P.: 104 at 1800 R.P.M.
Maximum B.H.P.: 115 at 2000 R.P.M.
Compression ratio: 5 to 1
Oil pressure: 60 p.s.i.
Weight: 300 lbs

There are some terms on the engine's plaque which may need definition, as follows.
"Right Hand Tractor": The propeller acts to pull the aircraft and the propeller rotates in a clockwise direction when viewed from the pilot seat.
"Firing order": The sequence of ignition initiation in each cylinder. No 1 is the front cylinder.
"Magneto advance": The spark initiated by the magneto occurs before top-dead-centre to assist the complete combustion of the fuel. (TDC occurs when the piston is at the top of its stroke, near the cylinder head)
"Valves, inlet and exhaust": In a four-stroke engine, on the inlet stroke the inlet valve opens 5 degrees (rotation of the crankshaft) before the piston reaches bottom-dead-centre (BDC) and closes 35 degrees after TDC. This is to achieve optimum air/fuel intake to the cylinder. On the exhaust stroke, the exhaust valve similarly opens 65 degrees before BDC and closes 5 degrees after TDC to achieve the maximum discharge of exhaust gases.
"Valve clearance": The clearance between tappet and valve stem, when the valves are closed is 2½ mm

Description provided by Noel Svensson.


Manufacturers plate on lower right hand side of engine, printed text stamped on plate, 'HARK (HORNET) NESS / AERO No 01 ENGINE / DIRECTION Right Hand Tractor / BHP Normal at 104 at 1800 R.P.M / BHP ....../ HARKNESS HILLIER LIMITED / SYDNEY / AUSTRALIA'.



1650 mm


850 mm



The "Harkness Hornet" aero engine was designed, initially as air-cooled, by Don Harkness and built at his Sydney engineering works, Harkness & Hillier Ltd, Parramatta Road, Five Dock, New South Wales, in 1929. For its 'type' certificate test and aircraft use Harkness converted it to water-cooling by using the cylinder bank from a French-built Hispano-Suiza aero engine of 1914. This was a water-cooled V8 engine used in a number of allied aircraft during the First World War. To this cylinder bank he attached a crank case of his own design.

Donald (Don) James Harkness (1890-1972) was a well known Australian racing car driver and engineer. He was born in the inner-western Sydney suburb of Leichhardt and began his engineering career as a teenager repairing the Gnome aero engine fitted to the Bristol Boxkite of the early Australian aviator, William Ewart Hart. Just before WWI Harkness joined J. C. Hillier, a motor engineer, in Sydney and by 1921 was a full partner in Harkness & Hillier Ltd. For the next 40 years, this firm built a variety of stationary and marine engines, timber jinkers, gas producers and automotive components. The firm also made parts for the Australian Six automobile and in 1924 took over that enterprise.

The "Harkness Hornet" engine was to be used in the Genairco aircraft, a locally-built biplane made by the General Aircraft Co. who established a factory at Mascot Aerodrome, New South Wales in 1929. In all nine aircraft were built by the company between 1929 and their liquidation in 1933. The "Harkness Hornet" was used to test one of the early Genaircos VH-UOG, which was registered on 20 November 1930 and test flown by Captain E.W. Leggatt. (This aircraft is also in the Museum's collection, object number 2007/143/1). However, while the Hornet engine was considered to be good; its performance was comparable to readily available English engines, the fact that it was water-cooled complicated its installation in the Genairco relative to the ease of installation of an air-cooled engine and the English Cirrus and Gipsy engines were generally used in the production run instead. The Genaircos were significant because the General Aircraft Co. was the first to serial-build aircraft in Australia, made to an Australian design, rather than one-off models or aircraft made to an overseas design.

A "Harkness Hornet" was also fitted to the "Wonga" aircraft, designed by the Australian aeronautical engineer Leslie John Roberts Jones (1886-1970). After serving in the Australian Flying Corps during World War I, Jones worked for the aircraft manufacturer, A.V. Roe, in England before returning to Australia in 1921 and working with several early aviation companies. In 1927 he was commissioned to build an aircraft for the Australian market and an all-steel welded framework plane, named the "Wonga", was the result. It was successfully flown in test flights with a Curtiss OX-5 engine, but after storm damage in August 1930, it was rebuilt with a "Harkness Hornet" engine. A contemporary account of the design and construction of the aircraft appears in "The Australian Engineer", published on 6 December 1930 entitled, "An all steel aeroplane". It was read by Jones himself before the Institute of Engineers, Australia. (This paper is in the Museum's collection, object number P 2581). Unfortunately the "Wonga" crashed on 16 June 1932 killing both occupants, thus bringing the project to an end.

In 1933 Jones and T.D.J. Leech designed an aircraft to compete in the 1934 MacRobertson London to Sydney air race (MacRobertson International Air Races). The aircraft was to be powered by two high compression "Harkness Hornet" engines, each producing 150 hp. It was hoped that the project could be completed through public donations and the construction was begun in the sporting department of Grace Brothers department store in Sydney to ensure public awareness but insufficient public donations caused the end of the project.



Don Harkness lost track of his prototype Harkness Hornet aero engine No.101 but in the late 1960s realised its historical significance in Australian aviation development and spent three years tracking it down before donating it to the Museum in 1968. Four years before his death in 1972, he was elected an honorary member of the Museum because of his valuable assistance given over the years.


Credit Line

Gift of Mr Don Harkness, NSW, Australia, 1968

Acquisition Date

29 July 1968

Cite this Object


"Harkness Hornet" aero engine, 1929 2018, Museum of Applied Arts & Sciences, accessed 24 March 2019, <>


{{cite web |url= |title="Harkness Hornet" aero engine, 1929 |author=Museum of Applied Arts & Sciences |access-date=24 March 2019 |publisher=Museum of Applied Arts & Sciences, Australia}}


This object record is currently incomplete. Other information may exist in a non-digital form. The Museum continues to update and add new research to collection records.

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