Quadcopters are the smallest of the usually used drones. Although, there are also tricopters, but they are not so common. Four engines mean better stability of this kind of UAV, they can flight steadily and be stay airborne for efficient time. Multicopters, based on this type of design, may become useful helpers in such areas like precision agriculture, aerial thermography, aerial photography, surveillance, terrain mapping and others. Quadrocopters are not usually so heavy like more complicated configurations, such as hexacopter or octocopters. That means they don´t need so much battery power as bigger aircrafts. Moreover, they might be also cheaper, which is certainly pleasant for small companies or private persons. On the other hand, they have no engine out capability. If a single engine fails, a whole UAS goes down.
Quadcopters are a perfect solution for small cameras or multispectral and infra devices, because of their limited lifting capability. The four propellers design is not used only for the Unmanned Aircraft Systems, there is Bell Boeing Quad TiltRotor project and others, mainly for military purposes. Apparently, the advantages of this configuration seem to have a promising future. Current UAV development is focused on increasing of the manoeuvrability, flight economy, better, smarter and more precise cameras and thermography devices and the recent progress is really quite impressing. Drones are becoming now a part of human life, they are no longer just hi-tech weapons or something from sci-fi movies. They are real, more accesible for common folks, more helpful in a daily life. Smart and swift quadrocopters can be even nowadays a way useful companion and helper for agriculturalists, directors, photographs, environmentalists, rescuers, engineers and many others.