About the Airco DH.2 Rotary Aircraft Engine
The rotary engine was an early type of internal-combustion engine, usually designed with an odd number of cylinders per row in a radial configuration, in which the crankshaft remained stationary in operation, with the entire crankcase and its attached cylinders rotating around it as a unit. Its main application was in aviation, although it also saw use before its primary aviation role in a few motorcycles and automobiles. This type of engine was widely used as an alternative to conventional inline engines (straight or V) during World War I and the years immediately preceding that conflict. It has been described as a very efficient solution to the problems of power output, weight, and reliability.When viewing the various World War I aircraft models in the museum you will discover that a large percentage of these early aircraft were powered by rotary engines. Although rotary engines physically look a whole lot like radial engines, they are actually in a separate classification all by themselves.
By the early 1920’s, however, the inherent limitations of this type of engine had rendered it obsolete, with the power output increasingly going into overcoming the air-resistance (drag) of the spinning engine itself. The rotating mass of the engine also caused significant gyroscopic precession: depending upon the type of aircraft, this produced stability and control problems especially for inexperienced pilots. Another factor in the demise of the rotary was the fundamentally inefficient total-loss oiling system, caused by the need to aspirate the fuel/air mixture through the hollow crankshaft and crankcase along with the lubricating medium, as in a two-stroke engine.