Definition
The temperature of the gas measured between the stages of the turbine section in a turbine engine. ITT is sensed by thermocouples placed between turbine wheels and is displayed on a cockpit gauge as a primary indicator of engine operating temperature. It is used to monitor combustion conditions, set power, and detect abnormal heat that could damage turbine components.
Plain English
The temperature of the hot gases as they pass between the spinning sections of a turbine engine. Pilots watch this number to make sure the engine isn't running too hot.
Context Anchor
Seen on turbine-engine instrument panels and in operating limits for engine start, takeoff, climb, and other power settings.
Derivation
‘Interstage’ means ‘between stages.’ In a turbine engine the turbine section has multiple wheels (stages) stacked one behind the other, so ‘interstage’ literally means the temperature is measured between those wheels rather than at the very front or very back of the turbine.
Why Pilots Care
Exceeding published ITT limits can damage turbine blades and shorten engine life; pilots use the reading to manage power without over-stressing the engine.
Intuition Check
ITT is not outside air temperature, oil temperature, or cabin temperature. It is a temperature reading from inside the turbine engine, at a specific point between turbine sections.
Example Sentence 1
During the engine start, the pilot watched the ITT carefully to make sure it stayed below the starting limit.
Example Sentence 2
A sudden ITT spike prompted the pilot to reduce power and check the fuel control.