Definition
A turbine engine instrument that displays the ratio of turbine discharge pressure to compressor inlet pressure, providing a direct indication of the thrust being produced by the engine. The indicator receives pressure signals from probes at the engine inlet and at the turbine exhaust, and shows the resulting ratio on a single gauge used by the pilot to set and monitor engine power.
Plain English
A cockpit gauge on a jet engine that shows how much thrust the engine is making by comparing the air pressure leaving the engine to the air pressure entering it.
Context Anchor
Seen in turbine-engine aircraft when setting, monitoring, or checking power during takeoff, climb, cruise, and instrument flight.
Derivation
From the engineering term 'pressure ratio' — a ratio comparing one pressure to another. In a jet engine, the ratio between exhaust and inlet pressure is a direct stand-in for thrust, so the gauge that displays it is named after what it measures.
Why Pilots Care
It lets pilots monitor engine thrust output and confirm the engine is delivering the expected power for takeoff, climb, and cruise.
Analogy
It is like comparing pressure before and after a pump to see how much work the pump is doing, rather than looking at only one pressure reading.
Intuition Check
Do not read this as a simple engine pressure gauge. It shows a ratio between two pressures, and that comparison is what makes it useful for judging engine power.
Example Sentence 1
On the takeoff roll, the captain advanced the throttles until the engine pressure ratio indicator showed the target value from the performance chart.
Example Sentence 2
In level cruise the engine pressure ratio indicator remained steady, showing the engines were maintaining consistent output.