Definition
An initial test run of a newly built or freshly overhauled engine, conducted under controlled conditions to verify that it operates within specified limits before it is released for service. The run-up checks parameters such as oil pressure, fuel flow, temperatures, and power output, and is used to seat new components and confirm there are no leaks, abnormal vibrations, or performance defects.
Plain English
The first proper run of a brand-new or rebuilt engine to make sure it works correctly before anyone uses it.
Context Anchor
Seen in aircraft maintenance records, engine overhaul discussions, and ground testing after engine installation or major engine work.
Derivation
From the long-standing use of 'green' to mean new, untested, or not yet broken in. A 'green run' is the run performed while the engine is still in that fresh, unproven state.
Why Pilots Care
A proper green run seats the rings correctly, reduces future oil consumption, and catches assembly problems before the engine enters service.
Grounding Statement
The key idea is simple: run the engine in a controlled setting before relying on it in flight.
Intuition Check
Green does not mean the engine is environmentally friendly or marked with a green color here. It means the engine is fresh from work and still needs to be proven by a careful test run.
Example Sentence 1
Before the overhauled engine was shipped to the shop, it completed a green run on the manufacturer's test stand.
Example Sentence 2
After the green run the engine was installed and the pilot flew the first hours at moderate power to finish the break-in.