What is the function/purpose of the EPR button

[Guest]

EPR button: What is it's function & when am I supposed to use it, & when should I use the "Speed" button instead?Thanks,Chris

[Jet Tech 31]

Chris,The basic funtion of EPR mode is to maintain a specific EPR target selected by the Thrust Mode Select Panel near the Gear Handle. The procedure I have seen used on the 757 was as followsFlight Crew would select a Thrust Rating from the TMSP (ie: T/O or Derate 1 or 2) prior to taking the runway.After lining up for Take-off, Captain depresses EPR button and autothrottles accelerate Engines to selected EPR limit. After take-off and above 400' Radio Altitude, Captain selects Climb thrust on TMSP and autothrottle system pulls back throttles to Climb EPR limit until crew selects VNAV function or Speed Mode. RegardsPaul :-cool

[Guest]

Paul... Why not use the to/ga button which is on the TMSP instead of the EPR....?At what times would you use the TO/GA button....it seems that the EPR, SPD and CLB are the ones to use instead...Thanks for your help here...we are all in a learning mode once again..!

[Guest chmitch]

All the TO/GA button does is set the target EPR for that particular flight mode. You still must activate this mode via the EPR button.

[Jet Tech 31]

Chris,The Thrust Management System on the 757 is a bit primitive when compared with the 777. Amazing what 15 years can change. The TO/GA, CLB, CRZ and Derate buttons on the Thrust Mode Select Panel (TMSP) are used to set a max EPR indication on the EICAS. It is supposed to limit the maximum thrust allowed for a specific phase of flight when EPR mode is in use. The EPR button actually engages the Auto Throttle System (ATS) EPR mode and is supposed to set the throttles to the specified EPR target selected on the TMSP. This is modeled well for Take-Off, but while the CRZ and CLB buttons change the EPR target, the PMDG A/T doesn't obey the thrust limits when CLB or CRZ is selected. I'm sure that Robert or Lefteris are working on this since they have nothing better to do with there time ;-) My guess is that it might be addressed in a patch or might be something to live with. It does work well for it main purpose which was to set T/O thrust and allow the pilot to concentrate on Flying the A/C instead of adjusting power to maintain maximum EPR during the T/O roll.Hope this helpsRegardsPaul:-cool

[Guest]

I think if it's a bug, this helps me a great deal! Do you find that the speed management works well for you all the time, even when descending below 10000 ft?Chris

[Jet Tech 31]

Chris,Absolutely, I use FL CH for almost all of my climbs and descents simply because I don't care for the way the VNAV mode handles Airspeed. In FL CH I can dial in a speed and the A/T will fly it perfectly of the way to the deck . Unfortunately, I am kind of lazy with the throttles as I allow the ATS to run the throttles from the time I line up on the runway til I touchdown at the end of the flight for most flights and I can honestly say from experience that this ATS model is Very close to the real 757 ATS. Once the minor MCP annunciation issues are resolved I think it will be darn near perfect. While flying Jumpseat on the 757, I actually found that a lot of the Captains didn't use VNAV all that much until cruise at least before the Pegasus FMC upgrade. Not as much of an issue with the Pegasus FMC system due to the major memory upgrade. RegardsPaul :-cool