ORIGINAL: 1bwana1
I still have never seen a logical explanation as to why the difference in weighing planes with or without fuel (batteries) exist at all. From the outside it appears to be just a way to protect a legacy. Take-off weight, is take-off weight, a very simple concept.
Both the FAI sporting code and the AMA regulations use the following wording...
Propulsion source limitations:
Any suitable propulsion source may be used except those requiring solid expendable propellants, gaseous fuels (at room temperature and atmospheric pressure), or liquefied gaseous fuels. Electrically-powered model aircraft are limited to a maximum of 42.56 volts for the propulsion circuit, measured prior to flight while the competitor is in the ready box.
One way to enforce the 42.56 max volts is to have a weight rule that includes weighting an e-powered aircraft with motor batteries intended for flight. During the weight-in process an official has the opportunity to inspect and tag the batteries intended for flight. If necessary immediately following an official flight tag batteries can be easily verified.
Curious, is max volts monitored/checked at the US NATS AMA or FAI classes?