Crédit : Nasa 

Engine PR

Crédit : Nasa 

WHAT IS EPR (Engine Pressure Ratio)?

Nowadays most aircrafts whether commercial or military are powered by a gas turbine engine also called jet engines. As the Air flow goes through the engine, it applies pressure, but there is a difference between the intake pressure and the exit pressure of the engine.

The engine pressure ratio (EPR) is the ratio of the turbine exit pressure to the engine intake pressure. It is also an indicator of thrust. The more the pilot pushes the stick the greater is the intake pressure.

An engine pressure ratio (EPR) indicator for each engine is installed in the main instrument panel so that the pilot can measure thrust for a control and performance technique.

As there is a finite limit on the amount of pressure that an engine is designed to produce, EPR can be used to provide feedback to the pilot as the thrust lever is moved or to the Full Authority Digital Engine Control (FADEC), when installed, to ensure that engine limitations are not exceeded. An alternate method of limiting engine thrust production is based on compressor/fan speed.

To determine EPR, pressure measurements are taken by probes installed in the engine inlet and at the turbine exhaust. The data from these sensors is sent to a differential pressure transducer which then indicates the ratio of the two pressures on a flight deck EPR gauge. EPR system design automatically compensates for the effects of airspeed and altitude.



As explained before the EPR gives indication on the aircraft thrust and gives precious information from the engine to the pilot in the cockpit.

As many other onboard instruments, EPR sensors need to be carefully checked for security. 

Air Data Test Instrument can simulate pressure and therefore test and control probes are working properly to give precise and accurate measurement to onboard instruments. They are used to control pitot / static port but are also used to control EPR probe sensors.

The Air Data Test instrument simulates the intake pressure and the pressure at the nozzle. As you can see ton the picture above,

PS => will measure the pressure at the entrance of the engine 

PT => will measure the pressure at the exit of the engine.

The ADSE is simulating the altitude and then the EPR is controlled both on the ADSE interface and on the cockpit instrument to make sure there is no variation which could indicate leakage in the process and would be a sign of dysfunction.

 Since 2008, ATEQ Aviation manufactures automated testers for all types of aircraft. We are recognised from the aviation industry and are providing aircraft manufacturers and MRO centers with Air Data Test Systems. With the greatest quality standard our solutions and services are trusted and adopted by thousands of customers worldwide.

We can support you in this EPR (Engine Pressure Ratio) check procedure.  So find out more about our ATEQ Aviation ADSE product range.

ATEQ Aviation Division has offices and Sales representatives across the globe ready to support you.
Find the right contact near your location.