## 1 Introduction  
Many different types of devices are used nowadays in the starting procedures of Unmanned Aerial Vehicles (UAVs). The use of a UAV launcher can provide the following advantages:  
* energy savings (fuel, electricity);
* compensation for insufficient on board power reserves;
* enables the take-off of UAVs without chassis;
* can be used when runway is limited or inaccessible (muddy terrain, high grass, stones, etc. );
* increases the level of operator's safety;
* provides new possibilities for UAV design (location of wings and propulsion sources, chassis elimination);
* ensures special start conditions (acceleration, velocity, initial angle of attack, etc.). The most important argument among those mentioned above is operator safety. Aircraft with a mass less than 10 kg can be thrown by operators but that can expose them to injury since the wings or propellers sometimes have sharp edges. Another reason for using launchers is related to research concerning formation flight. A wide range of works within this field has been conducted for many years throughout the world [1; 2; 3] as well as in Poland [4]. Some concepts require small flying objectsto be located in a predetermined time and in precisely defined positions [5; 6]. This can be achieved by launching airplanes sequentially at certain speeds and at specified intervals. This task can be achieved through the use of launchers with controlled motion parameters. Numerous types of launchers are utilized depending on the class of a UAV [7] with rubber driven catapults being the most common in connection with small planes (up to 5 kg). Their design usually consists of a frame and a set of rubber ropes which act as the drive. However, for micro aerial vehicles (MAVs), for example, so-called \"bungee\" launchers constructed with only rubber elements without any frames are used. The size of a rubber launcher depends on the aircraft's dimensions as well as its mass with the possibility to apply these types of catapults to UAVs weighing from a few to over a dozen kilograms [7; 8]. Rubber launchers can have a modular structure and can be disassembled into smaller components making them easy to transport. Some very important disadvantages of these types of devices are their limited ability to control motion parameters and the relatively quick wear of their elastic elements which is the reason special systems are sometimes used to monitor the tension of their rubber drives. Work on the design and construction of rubber driven launchers is carried out, among others, at the Bialystok University of Technology (BUT) in Poland. Pneumatic launchers can be used for small and medium class of aircraft. In these types of catapults compressed air is utilized as the driving medium. Great energy stored through compressing air makes it possible to launch UAVs weighing several dozen or even hundreds of kilograms [7]. The construction of such devices requires the use of special carriage to which the airplane being launched can be attached during the starting phase. After UAV start it is necessary to initiate a controlled braking process of the carriage. In pneumatic launchers, maintaining motion parameters, both during the launching and the braking phase, can be quite complicated due to the system's high inertial forces and thermodynamic properties [9]. Steam driven devices are also used in starting procedures, especially in respect to large flying objects. They are most commonly used on aircraft carriers to assist the launch of big manned aircraft and unmanned tactical airplanes weighing up to several dozen tons [7]. Thermal energy generated by the ship's reactors is used to evaporate water into steam which is then used to power steam launchers. Rocket propulsion is also used to accelerate tactical objects such as the so-called \"smart\" missiles that are nothing more but flying unmanned aerial vehicles. These types of devices are most commonly used for military purposes.