englishal (I am sure you know this already but just answering your rhetorical question)
there are typically three power settings a pilot (of a carbureted basically instrumented aircraft ) can use.
1 - leave the red knob fully forward (this will typically achieve less than book power except at near sea level density altitudes - particularly unfortunate from a back country airport during the summer in the Rockies)
2 - pull the red knob back to achieve best power and the black one to set the desired rpm
3 - pull the red knob back some more to achieve best economy and don't pull the black one quite as far.
2 and 3 can achieve the same power output, however,
3 will result in a lower ceiling as for each power setting you need more air (I.e. are less throttled)
3 will also typically result in higher CHT and internal pressures. At the high end of power output, combined with a hot day and low cooling airflow can result in pre-ignition.
obviously those who fly injected and instrumented aircraft have a 4th option which is to generate the power LOP, which has the benefit of low CHT and internal pressures coupled with low fuel consumption (of option 3)
Last edited by mm_flynn; 3rd Jan 2012 at 12:36.
Reason: clarify option 4 gives same economy as option 3