Although I know what constant speed propellers are and how they work, I'm still a little confused how to use them correctly.Sure, there are tables describing the relationship between RPM and torque/MP for different flight stages, but what do I have to set between?E.g. I did some flights with the Aerosoft DHC-2, and though for most flight phases the numbers are really helpful, there are times when I need to greatly deviate from them - and I don't have any numbers for these situations.My understanding is that e.g. one doesn't have a sensible impression (through 'feeling' or 'hearing') if an RPM is too low for a given torque, which would ruin the engine in the long term.So what tells me when I'm 'out of the tables' what RPM-to-torque ratios are 'safe' so I don't overstress the engine?If I'm not wrong here I guess one can always increase RPM to be sure, but what about 'flying efficiently'

Some basic information here:http://www.avweb.com/news/maint/185020-1.htmlThis is quoted from a Hartzell brochure I had lying around"Unlike fixed-pitch props which force you to choose between a 'climb' or 'cruise' design, a constant-speed prop enables you to optimize both"SO that's the benefit. As for actual use, that can depend on BOTH engine and propeller combination - Big radials like the ones used in the Beaver will need pulling back a long way from full power for cruise, and it is quite likely that the prop needs a rpm reduction of similar order. By contrast, the Mooney seems to work best (IRL and in the sim) by having the prop rpm close to max all the time.Some engines (Lycoming flat fours particularly) don't like being `oversquare` - that is the prop rpm greater than the engine rpm, but that's because there is a danger that the prop could drive the engine, rather than the other way round. But don't try that with a Rotax! Radial engines require careful husbandry in landing phase with gentle power reductions matched to prop speed reduction.Amnd yes, because all this adds to pilot workload and increases the chances of errors ion settings, some of the most modern aeroengine desigs include FADEC - full authority digital engine control, with only a single power lever. The computer works everything else out for you. Diamond DA42 and the new Cirrus are two examples, from memory.Hope this helpsAllcott