Accuracy of Smartphone-Based Barometry for Altitude Determination in Aircraft Flight Testing

Low-cost digital data acquisition systems have substantially transformed how aircraft flight testing is taught at The Ohio State University. With the advent of smartphones with built-in sensor suites, students now have access to modern data acquisition techniques and an expanded envelope of aircraft characteristics that can be measured in flight, and with much greater fidelity. A recent AIAA conference paper (Gregory and Jensen, AIAA-2012883) details the initial implementation of digital data acquisition techniques for flight testing education, with a specific focus on smartphone-based systems. However, that work showed that altitude measurement with smartphone-based GPS was highly erroneous. This work seeks to assess the accuracy of barometric pressure sensors on smartphones for measurement of altitude in flight, and how well cabin pressure may be used as a proxy for freestream static pressure. Results presented here indicate a measurement accuracy of ±40 ft, which improves to ±15 if the difference between freestream static and cabin pressures is calibrated and accounted for.