Due to the extremely different thrust requirements for vertical take-off/landing and forward flight modes, the BOP is equipped with eight drive units. In VTOL mode, all eight are engaged. When the BOP is switched to forward flight mode, four to six of the drive units disengage, allowing greater motor efficiency and thus substantially extending battery discharge time and therefore flight times. These motor/propeller drive units are arranged in a coaxial orientation, with two drive units being stacked together to minimize the number of holes through the body. The top/forward drive units will consist of a 2808 series motor running at 2400 kV and a standard 7 inch carbon fibre propeller. The bottom/rearward drive unit will consist of the same motor as top/forward, but the propellers will be folding props (like those used on gliders) and will fold back when drive unit is not engaged, reducing drag coefficients and increasing thrust effectiveness by a considerable amount. In instances where extreme amounts of power are needed, two or four of these drive units can be engaged (ie steep vertical climb, burst of speed).