Definition
An aircraft engine cylinder whose inside diameter is deliberately ground slightly smaller at the top (the closed end near the cylinder head) than at the bottom (the open end near the crankcase). When the engine reaches operating temperature, the cylinder head expands more than the barrel, and the choke disappears, leaving the bore straight and uniform along its full length.
Plain English
A cylinder that is made a little narrower at the top end on purpose, so that when the engine heats up and the top expands, the inside ends up perfectly straight.
Context Anchor
Seen in aircraft engine maintenance, cylinder inspection, and discussions of cylinder wear and engine overhaul.
Derivation
‘Choke’ here means a deliberate narrowing, the same sense as a choke in a shotgun barrel or a carburetor. ‘Ground’ refers to the precision grinding process used to shape the inside of the cylinder. So the name simply describes how the part is made: a cylinder ground with a choke in it.
Why Pilots Care
Proper choke grinding prevents scoring, ring leakage, and power loss by ensuring even contact as the cylinder expands in flight.
Analogy
It is like making one part of a metal part slightly undersized when cold because you know it will expand when hot. The cold shape is not the final working shape.
Grounding Statement
The top of the cylinder runs hotter than the lower part, so it is made slightly smaller when cold to allow for greater expansion when hot.
Intuition Check
Do not read “choke” as the engine control used for starting some engines. Here, “choke” means a deliberate slight narrowing in the cylinder bore.
Example Sentence 1
The overhaul shop measured the choke-ground cylinder at room temperature and confirmed the taper was within service limits.
Example Sentence 2
After overhaul, the choke-ground cylinders restored compression and eliminated the previous oil consumption problem.