Definition 1 of 2
Definition
The metal pipes that route burned gases out of the engine cylinders and discharge them overboard. On most piston aircraft engines, exhaust stacks also serve as the heat source for cabin heat and carburetor heat by passing fresh air through a shroud or muff surrounding the hot pipe.
Plain English
The pipes that carry hot exhaust gases out of the engine and dump them outside the airplane. They also act as a heater — fresh air flowing around the hot pipes is warmed up and sent into the cabin or to the carburetor.
Context Anchor
Seen during preflight inspection and in engine-compartment discussions, especially when checking for cracks, looseness, or signs of heat damage.
Derivation
‘Exhaust’ comes from Latin exhaurire, meaning ‘to draw out’ — fitting, since the pipes draw burned gases out of the cylinders. ‘Stack’ refers to a vertical pipe that vents gases, the same word used for a chimney stack.
Why Pilots Care
Cracked or leaking exhaust stacks can allow carbon monoxide to enter the cabin through the heater or vents, creating a serious safety hazard.
Intuition Check
Do not think of “stacks” as piles of parts. In this context, exhaust stacks are specific metal pipes that carry engine exhaust out of the airplane.
Example Sentence 1
During preflight, the pilot checked the exhaust stacks for cracks, looseness, and signs of leaking gases.
Example Sentence 2
A leaking exhaust stack allowed fumes to enter the cockpit when the cabin heat was turned on.