Definition
An aircraft engine ignition arrangement that uses two independent magnetos, each firing its own set of spark plugs, so that every cylinder has two spark plugs fired by two separate sources. The system provides redundancy if one magneto or plug fails, and produces more complete combustion by igniting the fuel/air mixture from two points in the cylinder at once.
Plain English
Each cylinder has two spark plugs, and each plug is powered by its own separate ignition source. If one source quits, the other keeps the engine running, and having two sparks per cylinder also makes the fuel burn more evenly.
Context Anchor
Seen in piston-engine aircraft system discussions and during the before-takeoff engine check, when the pilot checks each ignition side.
Derivation
‘Dual’ comes from the Latin duo, meaning two. The term simply tells you there are two of everything important in the ignition path — two magnetos, two sets of plugs, two wiring paths — so a single failure doesn’t stop the engine.
Why Pilots Care
Provides redundancy against ignition failure and improves combustion efficiency, both critical for safe flight.
Intuition Check
Dual does not mean the airplane has a second engine, and it does not make engine failure impossible. It means this one engine has two separate paths for making spark.
Example Sentence 1
During the runup, the pilot tested each side of the dual ignition system by switching from BOTH to LEFT and then to RIGHT, checking for an acceptable rpm drop on each.
Example Sentence 2
The dual ignition system kept the engine running smoothly even after one magneto began to fail in flight.