Definition
A streamlined cowling ring fitted around a radial engine to reduce aerodynamic drag and direct cooling airflow over the cylinders. The speed ring is a short, ring-shaped fairing that smooths airflow around the exposed cylinders of a radial engine, lowering drag while still allowing enough air through to cool the engine.
Plain English
A round metal ring fitted around the front of a radial engine that smooths the air flowing past the cylinders. It cuts drag so the aircraft flies faster, while still letting cooling air reach the engine.
Context Anchor
Seen in maintenance and cowling discussions for radial-engine aircraft, especially older or vintage airplanes.
Derivation
Called a 'speed ring' because its original purpose was to increase the aircraft's speed by reducing the drag caused by the bare, exposed cylinders of a radial engine.
Why Pilots Care
Correct setting prevents engine overspeed or underspeed, protecting the powerplant and maintaining efficient flight performance.
Grounding Statement
Picture air meeting a round, exposed engine: the speed ring helps guide that air smoothly around the cylinders instead of letting it tumble into them.
Intuition Check
A speed ring is not a speed-measuring instrument. It is a physical ring-shaped cowling used to improve airflow around a radial engine.
Example Sentence 1
During the inspection, the technician checked the speed ring for cracks and secure attachment to the engine mount.
Example Sentence 2
During cruise the pilot reset the speed ring slightly lower to reduce fuel burn while keeping the engine within limits.