New technology reduces aircraft noise

Citation

(1999), "New technology reduces aircraft noise", Aircraft Engineering and Aerospace Technology, Vol. 71 No. 4. https://doi.org/10.1108/aeat.1999.12771dab.001

New technology reduces aircraft noise

New technology reduces aircraft noise

Keywords: Aeroengines, Aircraft, Sulzer, Noise levels

A breakthrough in the production of quieter and more efficient aircraft engines has, it is reported, been made possible by a new plasma-spray bore technology from Sulzer Metco.

In small two-to-four-seater aircraft, the engine accounts for a large proportion of the total weight (Plate 1). So if the engine is made of a lighter material, the aircraft is lighter, requiring less power, making less noise and using less fuel with fewer harmful emissions. The material used to achieve this lightness with strength is an aluminium and silicon alloy, but there has been a problem of friction between the cylinder bore and the piston rings (Plate 2). The traditional solution has been to insert cast iron rings between the aluminium block and the piston rings, but this adds back weight and cost. Other solutions have been tried, but either cost more or create environmental difficulties (Plate 3).

Plate 1 An engine mounted in an aircraft

Plate 2 A close up of the cylinder bores and pistons

Plate 3 Engine cylinder bores being checked for dimensions

So the solution offered by Sulzer Metco was to plasma-spray the internal diameter of the aluminium bore with a coating which resists wear and eases friction. This, we are informed, was made possible by a device called Rota-Plasma-500 which rotates the head of the spray gun up to 200 times a minute. Internal diameters as small as 35mm can be given a consistent surface and repeated automatically for series production.

Now MDB Flugtechnik of Langenthal, Switzerland, have used this technology successfully to produce four-cylinder aluminium engines, with liquid cooling, in the power range of 160 to 220bhp, using unleaded fuel. By eliminating the weight of a conventional cylinder liner altogether, the engine is lighter, so the aircraft designer can use a marginally smaller, less powerful engine to achieve the same lift and thrust. Consequently, for the same payload, the aircraft is more friendly to the environment as it is quieter, uses less fuel a mile and makes less exhaust emission.

Details from Sulzer Metco. Tel: +44 (0) 1252 525336.