This article is a theoretical venture that aims to answer a series of practical questions, such as:

– given a certain electrical setup that can generate a certain power, what is the maximum thrust that we can achieve ?

– can a human-powered aircraft be built ?

– can I tell the expected thrust generated by a copter simply by knowing the power it consumes and vice-versa ?

– are larger propellers really more “efficient” ?

– which multicopter configuration is more efficient: tricopter , quadcopter , hexacopter or octacopter ?

– I heard that for every gram of mass I add to my multicopter, the flight time will decrease by 1 second, can you put any sense in this ?

*– and many more…*

*PLEASE NOTE THIS A REVISED ARTICLE ( 10/30/2015)*

## Comments

Bart, can you please elaborate on how you calculated that

battery-size-sweet-spot?I may disagree with Brat last answer. Battery power release is not linear with voltage drop (highly dependent on the electrode surface and quality of quasi-polymeric electrolyte) also the higher the copter weight (due to heavy battery) the more load no the motors. Thrust - power consumption curve is also not linear for any motor, so with increase of the battery size you may end up in a shorter flight time if motor - ESC efficiency low and if your battery have low grade polymer ionic permeability (no way that you can find it out from manufacturer).

- yes

- the one with the lowest disk loading

- depends, for the highest theoretical flight time, your battery should be 2x the mass of the copter without battery (so 66.6% of your total weight). Adding more battery from that point will decrease your flight time. In practice, about 50% of your total weight in battery will give you close to the longest flight time

Where are these answers?

– are larger propellers really more “efficient” ?– which multicopter configuration is more efficient: tricopter , quadcopter , hexacopter or octacopter ?– I heard that for every gram of mass I add to my multicopter, the flight time will decrease by 1 second, can you put any sense in this ?The article was revised 10/30/2015 the coefficients are now in line with classical theories.

Starlino, it's a good explanation but you may want to check your measurements or calculations again. Usually the ratio between electrical energy coming from the battery to kinetic energy into the air < 100%. Otherwise you may have found the perpetuum mobile :)

ESC+motor usually have an efficiency of around 60 to 80% and for the propeller the same. Perhaps one of your constants has an error?

Nice explanation. Good job. A online app or excel spreadsheet would be even more helpful.