and 30W per pound will fly like a GWS tigermoth :-)
Its not *quite* that simple tho. The wttas per pound does two things - overcomes the drag, and any surplus gets to lifte the mass of teh aircraft against gravity - a (in my day) O-level mechanics exercise in calculation. So heres one for you all. How many watts does it take to lift one pound at 1000 feet per minute in an ideal frictionless world?
The reason parkflyers get way with less than 50W/lb is that they fly SLOWLY. First order approximations have drag and lift roughly relaed - i.e. double the weight needs double teh lift which is double teh drag.
Similar maths from your O-level course will show you that the power needed is proportional to drag times speed. So to keep a lb of plane in the air at 30moph takes roughly twice as many watts as to keep one in the air (assuiming it doesn't stall) at 15mph.
The original '50W/lb' rule was formulated for sport planes with stall speeds in the upper teens and lo twenties, with overall battery/ESC/motor/gearbox/prop efficiences around 50% or less.
However broadly your original tables are correct..but I'll amplify tehm a little
30-40W/lb Slofly or parkfly, or other low wing loading scale plane (GWS Tiger moths etc) 40-60W/lb Good basic trainer, or draggy WWI biplane. Also parkfl;y warbirds like GWS. 60-80W/lb Warbirds or smooth aerobats, probably good enough to loop from level. This is where picojets and the like tend to start operating. Aklso entry level gutless ducted fans :-) 80-100W/lb. Fast models with almost unlimited vertiocal, and possibly hover potential with efficient setups, but not fully 3D. minimum for decnt ducted fan IMHO. 100W-130W/lb. Full 3D in the right plane with unlimited vertical. Ducted fand now starts to look like a jet.i have alos derived another formula, which isn't quite as useful as it was with the advent of LiPoly, and that is that the weight of motor and cells etc. and teh equivalent power delivered is such that without the airframe,. a typical setup is capable of delivering 200W/lb. That means that to get e.g. 100W/lb the airframe weight must be no more than equal to the weight of the flightpack and motor. For e.g. 66W/lb the airframe is twice the weight of the power train.
This is a useful rule of thumb for electric conversions.