Definition
A short, high-temperature electrical discharge that jumps across a small air gap between two electrodes when the voltage across the gap becomes high enough to ionize the air. In aircraft reciprocating engines, a spark is produced at the spark plug to ignite the compressed fuel-air mixture inside the cylinder.
Plain English
A tiny, fast electrical flash that jumps across a gap. In a piston engine, this flash is what lights the fuel and air inside each cylinder so the engine can run.
Context Anchor
Seen in aircraft piston-engine ignition discussions, spark plug checks, starting problems, and engine roughness troubleshooting.
Derivation
From the Old English 'spearca,' meaning a small glowing particle thrown off by a fire. The word kept that sense of a brief, bright flash and was carried over to electricity once people noticed that an electrical discharge across a gap looks the same.
Why Pilots Care
Ensures reliable combustion; faulty spark can cause engine roughness, power loss, or failure to start, directly affecting flight safety.
Intuition Check
Do not think of spark as just any flash or flame. In engine use, a spark is a controlled electrical jump at the spark plug that starts combustion at the right time.
Example Sentence 1
During the run-up, the pilot checked each magneto to confirm that the spark plugs on both ignition systems were firing properly.
Example Sentence 2
A fouled spark plug may prevent the spark needed for smooth engine operation on takeoff.