Unmanned air vehicles are the favorite technology of recent years. The usage area of unmanned air vehicles is increasing day by day. Currently, the vehicles called drones are used in defense industry, cinema industry, cargo, fire extinguishing, observation, cartography etc.
These multi rotary unmanned air vehicles systems obtain the energy needs from lithium-based batteries and the number of engines are changing between 4-8 range according to usage area and needs.
The endurance is the most challenging subject for the drone manufacturers. There is a stagnation in lithium polymer and lithium-ion battery technology used in unmanned air vehicles.
Increasing the battery capacity is not a rational solution in aircrafts to increase the operating time.
The reason for this situation can be explained as; each engine used in an air vehicle is controlled by different driver. Each engine produces a thrust value in kilograms and this thrust value is directly proportional with the voltage value transmitted to the engine.
If the battery capacity increased, the weight will increase. Therefore, there will be a need for a new engine to provide this lifting force. The engines that have high thrust will naturally have higher current drawing capacity, increasing the capacity of the lithium-based battery used almost does not change the weight-efficiency ratio.
Some manufacturer companies in the world are designing hybrid drone systems. This type of systems has a diesel fuel generator on the vehicle and the energy that the engine needs provided by this generator. However, this type of rotary wing unmanned air vehicles is not user friendly in terms of transportation and usage.
Systems called tethered drones have been designed by drone manufacturers. Therefore, drones can stay in the air for much longer periods. These tethered drone systems can stay in the air at an average altitude of 100 meters. These systems, designed for specific job descriptions. For example, they are very useful for border security missions.
Shortly, it is still not possible to access a rotary wing unmanned air vehicle that combines features such as long range, high altitude, ease of use and long endurance
