Das ist ein Auszug aus der Panelbeschreibung von Richard Probst!
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EPR stands for engine pressure ratio and is the air pressure at the tailpipe divided by the air pressure of the engine inlet. Say for example the exhaust pressure is 1900 millibars and the inlet pressure is 950 millibars, then EPR can be found by:
1900 MB
950 MB
which is going to equal 2.0. Notice that the millibars cancel each other out, so EPR is a non-dimensional number. With the engines off, the inlet pressure will be at ambient air pressure and is going to equal the exhaust pressure:
1013 MB
1013 MB
which will be 1.0 using the above example of standard atmospheric pressure. So, any ratio over 1.0 is positive thrust, and anything under 1.0 is negative thrust. Can you have negative thrust? Yes. You'll see this in high speed descents at idle thrust because the ram air pressure at the engine inlet will exceed the pressure of the tailpipe. In other words, the engines are producing more drag than thrust. Do you have negative thrust during reverse thrust? No. Thrust is still being produced at the exhaust, it is just being directed forward by the vanes.
A bit of trivia - not every model of jet engine has sensors to report EPR, which is why you don't have EPR gauges on CFM56 powered planes such as the default 737-400.
On this panel, you'll see the EPR on the needle as well as the top digital readout. The lower readout is your bug setting. This bug setting is important as it serves as a reference for your autothrottles during takeoff.
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Ich denke, einfacher und besser lässt sich das nicht erklären.
edi
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