Definition
A machined ring or rim at the base of an aircraft engine cylinder, drilled with bolt holes, used to mount the cylinder securely to the crankcase.
Plain English
The flat, ringed base of a cylinder that bolts it onto the engine. It is what holds the cylinder in place on the crankcase.
Context Anchor
Seen during engine maintenance, cylinder removal or installation, and inspections for leaks, looseness, or cracks around the cylinder base.
Derivation
Flange comes from an old word meaning a projecting rim or edge. The cylinder flange is exactly that — the projecting rim at the bottom of the cylinder that gives it something to bolt through.
Why Pilots Care
A damaged or improperly secured cylinder flange can lead to engine leaks, loss of compression, or in-flight engine failure.
Intuition Check
Do not picture the whole cylinder. The cylinder flange is only the rim or ledge at the base of the cylinder where it fastens to the engine case.
Example Sentence 1
During the inspection, the mechanic checked the cylinder flange for cracks before reinstalling the cylinder on the crankcase.
Example Sentence 2
Even torque on the cylinder flange bolts prevents warping and ensures a tight seal with the crankcase.