Definition
A turbine engine in which the compressor and the turbine are mounted on the same shaft and rotate together as a single unit at the same speed. All compressor stages are driven by all turbine stages through this one common shaft.
Plain English
An engine where the spinning part that pulls air in and the spinning part that gets pushed by the hot gas are joined to one shaft, so they always turn together at the same speed.
Context Anchor
Seen in turbine engine design, maintenance, and engine operating discussions, especially when comparing engine layouts and how power is transferred inside the engine.
Derivation
Shaft refers to the rotating rod that links the compressor and turbine. Single-shaft simply means there is only one such rod tying the rotating parts together, rather than two or more independent ones.
Why Pilots Care
Engine layout affects how the engine accelerates, how it responds to throttle changes, and how power is taken off for a propeller or rotor. Knowing it is single-shaft tells a pilot or technician that the compressor and turbine cannot spin at different speeds.
Analogy
Think of several wheels mounted on the same axle: when the axle turns, the wheels tied to it turn together. A single-shaft turbine engine works in that same basic way inside the engine.
Intuition Check
Single-shaft does not mean the airplane has only one engine. Here, “single” means the turbine engine’s main rotating parts share one common shaft inside the engine.
Example Sentence 1
In a single-shaft turbine engine, the compressor cannot spool up independently of the turbine because they are mechanically locked together.
Example Sentence 2
During preflight inspection the mechanic verified that the single-shaft turbine engine showed no signs of shaft misalignment.