An empirical method for the catapult performance assessment of the BPPT-developed UAVs

Abstract

This paper provides an empiric method in estimating the UAV's launched speed from the catapult. Besides its practicality, the method is applicable to validate the UAV performance in its development or configuration modification. Thus, using this method, a faster and accurate estimation of launch speed can be obtained from the catapult before launching the real UAV. Recently, the Indonesian Agency for The Assessment and Application of Technology (BPPT) has prototyped a launchable backpack UAV using the experience in the predecessors’ landing-geared UAV. Such sequence was preferable, since any failure of the landing-geared take off prevented severe damage compared to the gearless UAV. Thus, after the prototypes of the backpack version of UAV were ready for first flight, the flight test crew needed to ensure that the launcher produces an adequate launch speed.The initial idea is building a dummy prototype equipped with flight telemetry module and measuring the speed directly. But “crashing” the dummy with embedded electronic module will be risky and causing severe damage to the electronics. Another method proposed was by using a stopwatch to measure the elapsed time between the start to the release point of launching. Although preferable since it excludes electronics on board, it will suffer low accuracy.Thus, the solution carried out by performing generalization and transformation of the problem into the energy balance case. Using the conservation of energy, the equation of catapult releasing speed can be derived by launching the dummy UAV. Thus, the method only requires practical measurement device to obtain sophisticated result. Using this prior knowledge of the catapult performance, the BPPT successfully launched the backpack UAV by 4.86% of difference between the estimated and real launch speed.