This paper presents a sensor data acquisition unmanned aerial system (SDAC-UAS) for flight state monitoring and aerodynamic data collection research on small to mid-sized unmanned aerial vehicles (UAVs). The SDAC-UAS was developed to provide the ground-based human (safety) pilot an easily discernible display of sensor and state data for aircraft monitoring along with providing the ability to remotely start and stop on-board logging. The system is composed of three elements: an unmanned aerial vehicle, the sensor data acquisition system (SDAC), and ground interface. The SDAC is a low power and low weight unit that is fitted onto the UAV and acts as the sensor data distribution hub—the SDAC combines at 100 Hz a large variety of sensor streams into a unified high-fidelity state data stream that is simultaneously: recorded for post-flight analysis, transmitted to the ground to provide telemetry, and forwarded to a separate processing unit, such as an autopilot. Commands are given to the SDAC either locally using a simple interface or remotely using the down-link transceiver connected to the ground interface. The ground interface is a portable computer setup that runs a custom graphical user interface (GUI), which displays the sensor and state data and is used to transmit commands to the SDAC. The entire SDAC-UAS is completely fabricated from commercial-off-the-shelf (COTS) components, which reduced cost and implementation time; and it is designed such that it can be used with almost any small to mid-sized UAVs.