Italian and French Light Plane Engines

by Lucien Zacharoff

Compagnia Nazionale Aeronautica of Rome, the owner and operator of the famous Littorio Airport where a factory is maintained for building experimental airplanes and engines, has developed a four-cylinder engine designed for sports and training craft. The new power plant consists of two rows of two opposing cylinders each; it is rated at 60 hp.

The four-cylinder CNAD joins the same concern's family of engines. among the best known of which are the six-cylinder in-line type of 150 hp and a small two-cylinder opposed-type of 38 hp which weighs 42 kg empty.

Consisting of two halves, the crankcase has its lower part inverted underneath for cooling. Including the general lubrication, the oil capacity is sufficient for 25 hours in the air. An oil pump in front is provided with pressure-regulating apparatus.

Cooling rib and duralumin heads are to be found on the cylinders, each of which has one inlet and exhaust valve operated from overhead. The valve bar is worked by a camshaft located above the oil well and operated by spur wheels which are actuated by the crankshaft.

Crankshaft plain bearing is lubricated by pressure feed. There are two vertical ignition devices at the rear of the engine.

Carburetor connection is at the lowest part of the housing case. It is claimed that the carburetion tube is satisfactorily warmed because it runs through the oil well.

All oil pipes are inside the crankcase. Additional specifications include:

News of another European engine for light planes reached this writer about the time of the collapse of France. Although the two-stroke AVA 4 A-00 received publicity before the outbreak of hostilities as one of a crop of light-plane engines produced by L'Agence General des Moteurs AVA of Paris, it did not become known until recently that certain exemplars have completed over 1,000 hours in the air without any important part requiring replacement.

The AVA 4 A-00 develops 25 hp at 2,250 rpm. Its total weight (including attachment sheets and the hub of the propeller) is 37 kg. It was mounted with an interior pipe in the two-seater Gaucher. The design is built under a license granted by M Violet who is known for his years of work in developing two-stroke engines. Since the sponsor of the engine is M Jean Aubry, known to have been associated for some time with firms dealing in light alloys, it is not surprising that the design features the use of austenitic cast iron, tisalium and nitrided steels.

An obvious effort to create something mechanically strong yet simple, this French engine is based on the principle that the "two-stroke" reduces the number of moving parts and makes possible a reduction in weight, even of the essential parts. In corroboration it is pointed out that even the crankshaft (of nitrided steel) is of one piece.

The four offset cast-iron cylinders of this air-cooled opposed type have a 70 mm bore and stroke; cylinder displacement is 1,080 cubic cm. With the rated output as stated above, the maximum is said to be 28 hp. at 2,800 rpm. An American source informs us that fuel consumption is .66 to .715 lb per hp-hr, and the weight 81.5 lb, with overall dimensions of 21.65 in in width and 21.36 in in length. Reverting to our French data, we are told that the ground-plan of the engine occupies an area of 55 sq cm.

A special gas distributor of the rotary type, driven at one-half engine speed through gears from the rear end of the crankshaft, feeds the mixture to the cylinders in proper sequence. The mixture is produced in an Amal carburetor bolted to the manifold at the bottom of the crankcase. The carburetor is furnished with air control. The patented features include transfer ports through which the mixture passes. This particular scheme of mixture control, it is claimed, obviated one of the principal difficulties of the two-cycle principle of operation; the consumption figures above are cited as partial proof.

Also acting as an oil pump, the gas distributor forces the lubricant to all bearings. The crankshaft is made in a single piece of nitrided steel and is supported between the two halves of the vertically split light alloy crankcase. The connecting rods have shanks of H section, with roller bearings supported at their split ends. Ignition is provided by two magnetos mounted crosswise in the plane of the cylinders at the rear.

What the status of this engine and of its production has been since the German march into France is not known. Before the war, A B Gibbons of London had been licensed to produce the AVA engines in Britain.

This article was originally published in the November, 1940, issue of Aviation magazine, vol 39, no 11, pp 68, 122, 126.
The original article includes a line-drawing cutaway of the AVA engine and a photo of the CNAD engine.
Drawing by J Gaudefroy for L'Aeronautique; photo is not credited.