Let me begin by expressing my surprise for the fact that such a request doesn’t exist already, hence why I am here today…
EPR gauges on a Cathay Pacific B777-300.
What is EPR?
EPR, or Engine Pressure Ratio, is a measure of thrust output by a jet engine - it is the ratio between the turbine discharge pressure at the back of the engine and the compressor inlet pressure at the front, expressed as a decimal.
An EPR of 1.0 would therefore suggest that no net thrust is being produced.
Why EPR?
EPR is a direct measurement of the thrust being produced, unlike N1 which simply indicates the rotational speed of the low-pressure spool in a jet engine and is not directly proportional to the actual amount of thrust generated. It is therefore seen as a more accurate representation of engine output by some manufacturers and pilots alike (as it reflects the effect of engine wear and potential damage in real life on thrust output unlike N1) as a measure of engine thrust (despite some drawbacks associated with blocked inlet/outlet probes that may deliver erroneous readings therefore impacting the reliability of the measurements); and is used as a primary measure of thrust on most RR and PW engines.
So... why have EPR in IF?
Now you may be thinking, why do we actually need this?
The real-life counterparts of a large number of aircraft in IF across both Airbus and Boeing use EPR as a primary measure of thrust as opposed to N1 - e.g. A320 family (bar the A318) with IAEs, A330-300 with RR, all B757s, B777-200ERs powered by RR and PW.
Having EPR in addition to existing EGT and N1 measurements where appropriate, would definitely be a massive boost for realism and make performance calculations far easier to do - where assumed/FLEX temperatures and derates in these aircraft are all expressed in EPR and suitable N1 conversion graphs are very hard to come by, if even existent.
*Why is all this relevant, you may ask? With Simbrief integration and increasing accessibility to performance calculators, gone are the days of people being OK with simply firewalling the thrust at every takeoff - there is a noticeable increase in interest in adhering to realistic procedures which inevitably includes the use of reduced thrust on takeoff whenever possible. How these values for reduced thrust can be obtained reliably, however, continues to be an issue for IF users and having EPR on aircraft that use it as a primary measure of thrust will be a prudent first step in the right direction, short of having integrated assumed temperature and derated thrust calculations [to and within IF].)
Considering how the synthetic linear thrust indication has already found its way onto the A350 and A380, and the increasing attention to detail with each aircraft release, it is my sincere hope that this will too one day make its way into the IF fleet.
Furthermore, this will add even more variety to an existing fleet of aircraft (and certainly make some aircraft feel more “unique” than they are right now, by reflecting such differences between manufacturers and variants) - something that has always been appreciated by the community; and it is only through attention to details like this, that the flying experience can be truly elevated by giving every aspect of the model the attention it deserves, and differentiate IF from its potential competitors.
How would this work out in IF?
It could be exactly the same layout as in real life, i.e. EPR gauges at the top of the engine displays, followed by N1 and EGT below (in either order depending on aircraft type.)
Don't aircraft that use EPR as a primary measure of thrust also have N1 gauges?
Technically, yes, but…
Having EPR in addition to existing EGT and N1 measurements where appropriate, would definitely be a massive boost for realism and make performance calculations far easier to do - where assumed/FLEX temperatures and derates in these aircraft are all expressed in EPR and suitable N1 conversion graphs are very hard to come by, if even existent - which is exactly why I made this request in the first place.
i.e. overall, it’s just better for realism, something I hope we are all aiming for.
Thank you very much for your time - I would be especially grateful if you could spare a vote for this!