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jetsflier

Not Understanding Thrust Reading

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I'm flying my CLS A330 for long haul currently. The thrust/throttle whatever readings are all in decimals.

 

The Airbus X Extended uses numbers like 56.9 etc. The CLS A330 has 0.804 or 1.096 etc. 

 

I don't understand why they are different.

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It's the difference between :

N1 (turbine rotation speed expressed in percent): http://en.wikipedia.org/wiki/Airbreathing_jet_engine#Terminology

And EPR http://en.wikipedia.org/wiki/Engine_pressure_ratio

 

Both are used to express engine power, over the internet you can find lengthy discussions which one is better.

 

The choice of N1 or EPR to express engine power depends on the engine manufacturer. Most modern General Electric engines use N1 as primary, while P&W or Rolls-Royce use EPR (N1 is a secondary indicator in case EPR probe fails). You can find that the same type of aircraft will have different engine indicators depending on the engines installed. 737NGs always use N1, because CFM engines are the only option. But A320s use either N1 or EPR, depending on the engine installed, whether it's manufactured by CFM or IAE.

 

Here's a photo of a CFM A320 with two rows of indicators on ECAM: N1 and EGT

http://3.bp.blogspot.com/-FeNZkrKEujo/T0V29c6lUkI/AAAAAAAAAHo/CaIdW0MfTzg/s1600/Airbus-319-cockpit.jpg

 

And a IAE A320, with three rows of indicators: EPR, N1, EGT:

http://cdn-www.airliners.net/aviation-photos/photos/4/3/6/1553634.jpg

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It's the difference between :

N1 (turbine rotation speed expressed in percent): http://en.wikipedia.org/wiki/Airbreathing_jet_engine#Terminology

And EPR http://en.wikipedia.org/wiki/Engine_pressure_ratio

 

Both are used to express engine power, over the internet you can find lengthy discussions which one is better.

 

The choice of N1 or EPR to express engine power depends on the engine manufacturer. Most modern General Electric engines use N1 as primary, while P&W or Rolls-Royce use EPR (N1 is a secondary indicator in case EPR probe fails). You can find that the same type of aircraft will have different engine indicators depending on the engines installed. 737NGs always use N1, because CFM engines are the only option. But A320s use either N1 or EPR, depending on the engine installed, whether it's manufactured by CFM or IAE.

 

Here's a photo of a CFM A320 with two rows of indicators on ECAM: N1 and EGT

http://3.bp.blogspot.com/-FeNZkrKEujo/T0V29c6lUkI/AAAAAAAAAHo/CaIdW0MfTzg/s1600/Airbus-319-cockpit.jpg

 

And a IAE A320, with three rows of indicators: EPR, N1, EGT:

http://cdn-www.airliners.net/aviation-photos/photos/4/3/6/1553634.jpg

 

Thanks, that's perfect.

 

The Rolls Royce engine on an A330 is the only aircraft using exclusively EPR. That makes sense now. 

 

Thanks!

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