With the emergence of many commercial-off-the-shelf (COTS) and/or open-source hardware and software, we can now build cheap Unmanned Aerial Vehicles (UAVs). This will enable a broad spectrum of potential UAV based mobile applications. In this work, we propose a simple open UAV platform: Ard-μ-copter. Ard-μ-copter is a quadcopter built upon the open source ArduPilot [1] infrastructure library and hardware. Comparing to the many existing commercial quadcopters platforms and open source quadcopter platforms, Ard-μ-copter platform is fully open source, simple (i.e. what the "μ" stands for), and with good documentations.