Definition
A condition in which a turboprop or turboshaft engine's output is restricted by the maximum allowable torque the engine or gearbox can safely transmit, rather than by other limits such as turbine temperature, fuel flow, or rotor speed. In a torque-limited operating condition, the pilot must reduce power as needed to keep torque within the published maximum, even if other engine parameters are still below their limits.
Plain English
The engine could produce more power, but it would twist the shaft and gearbox harder than they're built to handle. So the limit you have to respect right now is torque, not anything else.
Context Anchor
Seen in turbine-engine performance charts, power-setting procedures, and turboprop operations where torque is a primary engine limit.
Derivation
Torque comes from Latin torquere, meaning 'to twist.' Torque is literally the twisting force the engine applies to the propeller or rotor shaft. 'Torque limited' simply means the twisting force is what's holding you back.
Why Pilots Care
Tells the pilot exactly how much power can be set without risking damage to the propeller, gearbox, or airframe structure.
Analogy
It is like tightening a bolt with a wrench: once you reach the safe twisting force, you stop, even if you could physically pull harder.
Intuition Check
Do not read torque limited as simply “low on power.” It means the safe twisting-force limit has been reached before some other engine limit.
Example Sentence 1
On a cool day at low altitude, the PT6 is torque limited on takeoff, so we set power to the torque redline rather than pushing the levers fully forward.
Example Sentence 2
As altitude increases we shift from torque limited to temperature limited operation and begin to reduce torque to stay within limits.