Recovery of an Unoccupied Aircraft System and Recommendations for Avoiding Communication Loss in a Forested Environment

Unoccupied aircraft systems (UAS) are increasingly used to create spatial databases for use in natural resource research and in other disciplines. We describe our experience with the recovery of an UAS platform that became lodged in a tree located next to a small river island after experiencing communication loss. The UAS platform was a DJI M200 series aircraft that we had used for remote sensing applications over several years without issue. During remote sensing of a riparian restoration project, the M200 descended vertically downward after communication loss, became lodged in a tree crown, and was suspended above the river. A tree climber was temporarily able to grasp the platform but a landing support released and the platform fell into the river. Although being submerged for less than 30 seconds, inspection of the internal chassis later revealed at least some moisture had infiltrated into the chassis likely impacting electrical components. The sensor escaped without noticeable damage and operated without apparent impact after being subjected to prolonged drying. We were unable to determine the specific reason for communication loss after examining digital flight logs but investigated other similar reported loss occurrences to better understand what may have transpired. We provide some recommendations for minimizing loss based on our analysis of reported incidents with similar UAS platforms and from our experiences in using UAS for remote sensing in forested environments.