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Surrey Sensors has launched a low-cost, high-precision Micro Air Data System (MADS) for UAVs down to about 7 kg in gross weight (writes Peter Donaldson). Designed to feed accurate information on local airspeed to the flight control system, it promises benefits including greater range and endurance thanks to better trim, and could be used to generate environmental information, said research director Dr David Birch. MADS is essentially a pitot-static probe that measures three directions of velocity (x, y and z) together with pressure, altitude, air temperature and humidity, along with an accelerometer for calibration. Probe and case heaters to prevent icing and keep electronics warm, and armour to protect it from bird strikes, can also be included. The system uses off-the-shelf differential pressure transducers packaged by Surrey Sensors with its own firmware and calibration data reduction techniques. A typical probe tip has seven holes, with one in the centre and six arranged around it to record pressures at different points. Multiple pressure channels in the same probe measure both magnitude and direction of airflow. “This is particularly important if you are flying at relatively low speed,” said Dr Birch. “We are also working on systems that are omnidirectional, so they will work in hover.” While MADS is self-contained, customisable packaging options are available. With heaters and armour, the probe is about 11 mm in diameter, but without them the probe diameter can be as small as 2 mm, while the sensor package is about the size of a deck of playing cards. The bolt-on encapsulated version fits in a 25 mm diameter pipe 80 mm long, with the probe extending further. There is also a version consisting of the board with the sensors on it for embedding in the airframe. Flight control Air data system for UAVs announced The MADS sensor board with differential air pressure transducers