Narrative:

I was flying a small uas. During the flight; the aircraft passed in front of the sun and I lost visual contact for approx. 10 seconds. Afterwards; I could not reacquire visual contact. I could hear the propeller and executed what I estimated was a 180 degree turn with the throttle at mid-position to bring the plane back to my location. After waiting approximately the time the plane had been flying away from me; I scanned the likely area of sky but could not see it. I then executed a 90-degree banked turns to put the increase the visibility of the plane (the plane was flying in a stabilized mode with a roll limit of 90 degrees; so full aileron stick-deflection would cause a consistent 90-degree bank angle). When I was unable to see the plane (I could still hear the propeller at this point) I executed a series of turns while monitoring the rssi (receiver signal level transmitted from the plane back to the transmitter) and tried to find a course that would increase the rssi level indicating the plane was flying closer. Unfortunately; the rssi telemetry system is not very accurate at this range and I was unable to get a stable enough signal. At this point the telemetry link was lost (the transmitted signal has a substantially longer range). To minimize any potential damage on landing; I closed the throttle and applied full back elevator to slow the forward speed and descent rate until I estimated the plane would have landed (approximately one minute). The primary initiation of this event was a brief loss in awareness of the plane's path relative to the sun. Normally I avoid flying near the sun but in this case I misjudged.

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Original NASA ASRS Text

Title: UAV operator reported losing sight of the drone while controlling it in-flight.

Narrative: I was flying a small UAS. During the flight; the aircraft passed in front of the sun and I lost visual contact for approx. 10 seconds. Afterwards; I could not reacquire visual contact. I could hear the propeller and executed what I estimated was a 180 degree turn with the throttle at mid-position to bring the plane back to my location. After waiting approximately the time the plane had been flying away from me; I scanned the likely area of sky but could not see it. I then executed a 90-degree banked turns to put the increase the visibility of the plane (the plane was flying in a stabilized mode with a roll limit of 90 degrees; so full aileron stick-deflection would cause a consistent 90-degree bank angle). When I was unable to see the plane (I could still hear the propeller at this point) I executed a series of turns while monitoring the RSSI (receiver signal level transmitted from the plane back to the transmitter) and tried to find a course that would increase the RSSI level indicating the plane was flying closer. Unfortunately; the RSSI telemetry system is not very accurate at this range and I was unable to get a stable enough signal. At this point the telemetry link was lost (the transmitted signal has a substantially longer range). To minimize any potential damage on landing; I closed the throttle and applied full back elevator to slow the forward speed and descent rate until I estimated the plane would have landed (approximately one minute). The primary initiation of this event was a brief loss in awareness of the plane's path relative to the sun. Normally I avoid flying near the sun but in this case I misjudged.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.