Rate of Climb of Electric Multicopter

Abstract

The aim of the research is to study the dependence of the ascensional rate of electric multicopter from the height. Ascent rate is calculated for the operation of electric drive with 100 % of the throttle. The following facts are considered: brushless electric motors, which functioning does not depend on the air density and height, are used; fixed geometry rotors are used; the weight of the aircraft during the flight remains unchanged; the battery voltage decreases as its charge runs down; except for the time of start, the inertial forces do not play a significant role in a vertical flight. Rate of climb on the ground and hovering ceiling are determined. The dependence of the multicopter vertical velocity on the altitude was discovered. The calculation takes into account thrust-weight ratio, electric motor characteristics and drag force. Dependence is defined as a parametric function with advance ratio as a parameter. The formula of the hovering ceiling is proposed. Approximated aerodynamic characteristics of propellers used in multicopters are provided. The dependence of the rate of climb of the aerodynamic characteristics of the propeller is examined. A method of adaptation of the results for different propellers is proposed. The calculation of the rate of climb on the ground requires a numerical solution of the equation with advance ratio as the unknown. Solution results for several parameters values are presented as a table. These data can be used for calculation of climb as an interpolation of table values. The method of calculation of the rate of climb and hovering ceiling with changing supply voltage is proposed. Instead of increasing the dimension of the problem, it’s proposed to perform the calculation of the thrust-weight coefficients and inflexibility of the engine characteristics for altered supply voltage. Examples of calculation per the method proposed are provided for a quadcopter built by the author.