• This type of engine has cylinders lined up in one row. It typically has an even number of cylinders, but there are instances of three- and five- cylinder engines. The biggestadvantage of an inline engine is that it allows the aircraft to be designed with a narrow frontal area for low drag. If the engine crankshaft is located above the cylinders, it is called an inverted inlineengine, which allows the propeller to be mounted up high for ground clearance even with short landing gear. The disadvantages of an inline engine include a poor powerto-weight ratio, because thecrankcase and crankshaft are long and thus heavy. • In aviation, the term "inline engine" is used more broadly, for any non-radial, reciprocating, cylinder engine.
• A rotary engine isessentially a standard Otto cycle engine, but instead of having a fixed cylinder block with rotating crankshaft as with a conventional radial engine, the crankshaft remains stationary and the entirecylinder block rotates around it. In the most common form, the crankshaft was fixed solidly to an aircraft frame, and the propeller simply bolted onto the front of the crankcase. • Three key factorscontributed to the rotary engines success at the time: • Smooth running: Rotaries delivered power very smoothly because (relative to the engine mounting point) there are no reciprocating parts, and therelatively large rotating mass of the cylinders acted as a flywheel. •
• Weight advantage: many conventional engines had to have heavy flywheels added to smooth out power impulses and reducevibration. Rotary engines gained a substantial power-to-weight ratio advantage by having no need for an added flywheel. • Improved cooling: when the engine was running the rotating cylinder block createdits own fast-moving cooling airflow, even with the aircraft at rest. • Most rotary engines were arranged with the cylinders pointing outwards from a single crankshaft, in the same general form as a...