Radial Design

• A "radial" engine is so-called because its pistons are set in a circle around a center point, "radiating" out from the crankshaft centerline in an "X" or "+" configuration.
  
  

Competing Designs

• Other, more "standard" engine designs include the straight-configuration (where the cylinders run in a single line from back to front), V-configuration (also known as a "double-inline," where the cylinders come in two separate banks connected to each other at an angle) and flat-configured (like the V-engine, but the banks are directly opposed to each other).
  
  

Radial Function

• A radial engine uses a single multipart connecting rod to link the pistons to the crankshaft. When the crankshaft moves, the pistons move together in a sort of coordinated "wobble."
  
  

Radial Benefits

• The radial's engine relatively compact size and inherent simplicity made it a favorite for World War II fighter pilots because it performed well even when damaged by enemy fire. Additionally, its radial shape helped ensure adequate airflow to cool the cylinders.
  
  

Standard Benefits

• Because of their firing order and "wobbling" function, radial engines ran very rough and were limited to a fairly low rpm. Inline, V-configured and flat engines offered much higher power levels and smoother running, and their smaller size allowed engineers to make the aircraft more streamlined.