TOD,
EPR on a fan engine should really be called IEPR cos it's an integrated EPR value from three sources.
The back end of your Trent has only two 'holes' has it not...the jet pipe and the fan exhaust.
If we take a pressure reading in these two areas and multiply them electronically by the area of the associated outlet and then divide by the total area of the exhaust voila' we have an integrated exhaust pressure which we can now compare to the inlet pressurex inle area.
This is how I visualise it. Technically could be completely wrong but not too far off I suspect!
Our engine in descent also reads less than 1.00 EPR which I am able to rationalise but how you could still be getting positive thrust at 0.98 does seem a bit strange!!
