Definition
A spring-loaded valve at the lowest point of a turbine engine's combustion section that automatically drains residual fuel from the combustor and related manifolds after engine shutdown or following an aborted start. The valve is held closed by combustion-section pressure during engine operation and opens when that pressure drops, allowing trapped fuel to escape overboard rather than pool inside the engine.
Plain English
A small valve at the bottom of a jet engine's burner section that lets leftover fuel drip out after the engine is shut down or fails to start, so fuel doesn't sit inside the engine where it could cause a fire or damage on the next start.
Context Anchor
Seen in turbine engine systems, especially during engine start, shutdown, and troubleshooting after a failed start.
Derivation
Combustor comes from Latin 'comburere,' meaning 'to burn up,' and refers to the section of a turbine engine where fuel is burned. A drain valve simply lets fluid drain out. Together, the name describes exactly what the part does: it drains the burner section.
Why Pilots Care
Prevents unburned fuel from pooling in the combustor, which could cause a fire on restart or lead to corrosion.
Intuition Check
Do not think of this as a cockpit valve the pilot normally opens by hand. It is usually an automatic engine valve that drains leftover fuel from the combustor when the engine is not running.
Example Sentence 1
After the aborted start, the mechanic checked that the combustor drain valve had opened and released the trapped fuel before attempting another start.
Example Sentence 2
During the post-flight walk-around the pilot checks the ground beneath the engine for fuel stains indicating the combustor drain valve operated normally.