Manual reference EPR setting B757
Pulling out the manual EPR knob below the lower EICAS screen causes the reference thrust annunciator to change to "MAN" and the green EPR bug goes to 1.55. In VNAV PTH mode, this does nothing, as one would expect. Pressing "EPR" on the MCP causes the autothrottle to set this manually selected EPR (the vertical navigation changes to V/S). This has caused some trainers at my airline to scratch their heads a bit as they were under the impression that the autothrottle system would not drive to this manually set reference, but it clearly did on a flight the other day where we tried it.
Any pointer? The systems manual is useless (although haven't checked the old, more useful one)