Definition
The moment of ignition in a turbine engine when fuel introduced into the combustion chamber is ignited by the igniters and begins sustained burning. Light-up is confirmed by a rise in exhaust gas temperature (EGT) and an increase in engine RPM during the start sequence.
Plain English
The point during a jet engine start when the fuel actually catches fire and the engine starts running on its own combustion. The pilot sees this as the temperature gauge climbing and the engine spooling up.
Context Anchor
Encountered during turbine engine starting, engine start checklists, and maintenance discussions about normal or failed starts.
Derivation
From the everyday phrase 'to light up,' meaning to ignite or catch fire. In turbine engines, it refers literally to the fuel-air mixture lighting inside the combustion chamber.
Why Pilots Care
A successful light-up confirms normal combustion; delayed or absent light-up can indicate a hung start or hot start requiring immediate action.
Grounding Statement
During start, Light-Up is the first clear sign that fuel is burning inside the turbine engine.
Intuition Check
Light-Up does not mean the cockpit lights came on. Here it means the engine’s fuel has ignited during start.
Example Sentence 1
After introducing fuel, the pilot watched for light-up by monitoring the EGT for a steady rise.
Example Sentence 2
If light-up does not happen within the required time, the start must be aborted to avoid damage.