Definition
A short, flexible electrical lead, often coiled or spiraled, used to connect a component to a wiring system. In aircraft ignition systems, the pigtail is the flexible insulated lead that carries high-tension current from the magneto distributor or ignition harness terminal to the spark plug.
Plain English
A short, springy wire that connects one electrical part to another. On a piston engine, it's the flexible lead that carries the spark from the ignition harness to the top of the spark plug.
Context Anchor
Seen in aircraft maintenance manuals, wiring diagrams, avionics installations, lighting repairs, and electrical troubleshooting.
Derivation
Named for its resemblance to the curled tail of a pig. The coiled or spiraled shape gives the wire flexibility and slack, which is why the everyday word stuck as the technical name.
Why Pilots Care
A loose, cracked, or burned pigtail at the spark plug end is a common cause of rough running and ignition problems. Pilots and mechanics check pigtails during inspections because a bad one can cause a single cylinder to misfire even when the rest of the system looks fine.
Analogy
A pigtail is like the short cord coming out of a lamp before it plugs into the wall wiring. It is not the whole electrical system; it is the short connecting lead.
Intuition Check
Do not read pigtail as a hairstyle here. In aircraft maintenance, it means a short wire lead used for an electrical connection.
Example Sentence 1
The mechanic traced the rough magneto check to a cracked pigtail at the number three spark plug.
Example Sentence 2
Inspect all pigtails for chafing before closing the avionics bay after maintenance.