In this paper, a new MAC protocol is proposed for the communication system between a large wireless sensors network (WSN) and a small unmanned aerial vehicle (UAV). In this system, the direct communication between the sensor and the UAV replaces the conventional multi hop communication among the sensor nodes. The key factor of this system is to ensure the concurrent transmission from the sensor to the UAV. The idea is to divide the active sensors into several sub groups which each is assigned with a proper priority via the proposed PFS scheme (Prioritized Frame Selection). For effective reason, TDMA has been validated for those multiple data transmissions in each sub group. However, the number of sensors is unknown which is a challenging of this scheme in the first flight. This problem has been solved by another proposed FRA scheme (Frame based Random Access). The findings of this MAC protocol are the optimal number of sub groups, data packet size, and altitude of the UAV under an acceptable ratio of packet error rate (PER) and the number of sensors in the network.