Definition
A reciprocating-engine oil tank shaped to fit closely around the upper portion of a radial engine's crankcase, mounted directly on the engine rather than remotely in the airframe. Its curved lower surface conforms to the engine's nose case, giving it the appearance of a saddle sitting on a horse's back.
Plain English
An oil tank that is curved on the bottom so it fits snugly on top of the engine, instead of being mounted somewhere else in the aircraft.
Context Anchor
Seen in aircraft maintenance, engine installation, and oil system descriptions, especially when identifying where the engine oil tank is mounted.
Derivation
Named for its shape. A saddle is curved on the bottom to sit on a horse's back, and this oil tank is curved on the bottom to sit on the engine the same way.
Why Pilots Care
Ensures a steady supply of oil reaches the engine during flight; leaks or improper mounting can lead to oil starvation and engine damage.
Intuition Check
“Saddle” does not mean a seat for a person here. It means the oil tank is shaped to sit over or straddle part of the engine installation.
Example Sentence 1
The mechanic drained the saddle-mount oil tank before removing it for inspection.
Example Sentence 2
The restoration team chose a saddle-mount oil tank to keep the radial engine's lubrication system compact and true to the original design.