Definition
Heavily insulated wires that carry the high-voltage electrical pulses from the magneto to each spark plug in a piston aircraft engine's ignition system.
Plain English
The thick wires that deliver the spark from the magneto to each spark plug.
Context Anchor
Seen in aircraft ignition system discussions, engine inspections, and troubleshooting for rough engine operation.
Derivation
Tension' here is the older electrical term for voltage. 'High-tension' simply means 'high-voltage.' So a high-tension lead is a wire built to handle high-voltage current without arcing through its insulation.
Why Pilots Care
Damaged or improperly routed leads can cause misfires, rough running, or complete ignition failure.
Analogy
They are much like spark plug wires on a car engine, but made and installed for aircraft engine conditions and high reliability.
Intuition Check
“High-tension” does not mean the wires are physically tight or under stress. Here, “tension” means high electrical voltage.
Example Sentence 1
During the preflight, the mechanic showed the student a chafed high-tension lead that had been causing a rough magneto check.
Example Sentence 2
A break in one high-tension lead can cause the engine to run rough at high power settings.