Converting the engine to a fixed radial type has resulted in a marked decrease in fuel and oil consumption with a resulting increase in power output because the engine can be run faster with fixed cylinders and the horsepower formerly used in turning the cylinders through the air is now delivered to the crankshaft. Most of the American pursuit pilots who were instructed at. the Third Aviation Instruction Center of the A. E. F. at Issoudoun, Indre, France received their preliminary training on airplanes equipped with the Le Rhone engine.

The cylinders are of steel with circumferential flanges turned on the barrel and longitudinal flanges milled in the heads. In the rotary form, the gasoline was admitted through a hollow crankshaft, and castor oil was necessary for engine lubrication, and large quantities of oil were thrown out of the exhaust ports as the cylinder assembly revolved. This made this form of engine ail exceptionally dirty form to ride behind, which of course, was true of other rotary types such as the Gnome and Clerget. Cowling interfered with the cooling so pilots trained with the rotary engines know the taste and smell of partially burned castor oil very well. None of these faults are found in the Super Rhone.

From the nature of its construction, with its taper jointed counterbalanced crankshaft of single throw, complete disassembly can be accomplished by a mechanic of ordinary ability in thirty minutes time, thereby reducing lost flying time in schedule service to a minimum. The saving in weight through the elimination of the radiator and the water piping and connections, as well as the water itself, permits greater pay-load than with the water-cooled engine, and, at the same time, it removes a cause of frequent trouble with consequent forced landings. The absence of the radiator reduces head resistance, giving greater speed and maneuverability, and again reduces cost.

In the Super Rhone engine shown above, any complications in effective air-cooling have been. entirely overcome by a simple process which admits fresh air, under atmospheric pressure, to the crankcase, and which forces a complete change of air within the crankcase with each revolution. Thus, excessive accumulation of heat at the center is eliminated by the free passage of fresh cool air, this tending also, by regulation of temperature and pressure, to reduce oil consumption to a minimum.

The engine mounting which forms the basis of the conversion also serves as an intake manifold, is a strong, clean aluminum casting of tested strength. It carries on its rear and lower side, a flanged face opening to which the carburetor is attached and from which opening the explosive gases are carried to a central chamber from which they are conducted by individual ducts to apertures in the periphery of the casting where the intake pipes that lead to each cylinder are restened. Thus each cylinder draws its gases as needed from this central chamber, eliminating thereby the excessive amount of gas in anyone cylinder which is the most frequent cause of fouling in air-cooled engines and often attributed to lubrication faults. This engine mounting has two properly surfaced flanged extensions toward the rear, two inches wide and thirteen inches long, which form the means of fastening the engine to two engine beds as is the practice in water-cooled types. This cheapens installation costs by the elimination of expensive circular mounting brackets, and readily adapts the engine to installation in the usual manner. The engine mounting, also, carries the magneto and oil pump, and the scavenger pump, and it is to be noted that the engine proper may be withdrawn from this mounting without disturbing fuel, oil or electrical connections and controls.

The crankshaft of the Super Rhone has been carefully and efficiently counterbalanced, and vibration is reduced to a minimum. The rear end of the shaft extends backward about 16 inches, and from it are driven the magneto, oil pumps and distributor. The lubrication of the Super Rhone is effected with ordinary mineral oil of high viscosity, easily obtainable in any locality. Castor oil is not needed. Oil is supplied to the pump from which it is forced through a duct drilled through the length of the crankshaft to the working parts.