Our second day flying over Tasman Glacier was, unfortunately, not as successful as our first. We moved our ground control site a few kilometers downglacier, with the goal of finishing surveying the glacier with 3 more flights. The winds were calm near our site, so we felt confident that we would have a good flying day. Our first flight was largely successful, although we had to call the Sky Hunter home before it finished its last two transects across the glacier due to low battery. We suspected that our batteries were draining faster than usual because the plane was flying faster than its airspeed indicator suggested -- our groundspeed was 10m/s faster than our airspeed regardless of the direction we were flying, and it seemed unlikely that the winds were shifting direction at the same time that our plane was! After doing a quick airspeed sensor calibration, we were ready to send the Sky Hunter on its next mission.
After a beautiful launch, we sent the Sky Hunter diagonally across the glacier to the farthest point of the mission, which was almost 3km past our ground control station. The flight seemed smooth, although a strong gust of wind threw the Sky Hunter off-path in the middle of its first transect. Since the drone recovered without losing elevation, we continued on the mission. After flying two more transects across the glacier, the Sky Hunter was again thrown off its path, but this time it started rapidly descending. With autopilot staying on track but not staying at elevation, we took over the controls, and attempted to regain elevation. However, we had the additional problem that the Sky Hunter had been near the end of its transect, so steering it full speed ahead would have led to it crashing into a steep moraine wall. As we tried to steer away from the cliff and give the drone full throttle in an attempt to gain elevation, the drone instead started spiraling down towards the surface. Too soon, it became clear that we had crashed into the ground.
Because the drone maintained telemetry, RC, and GPS signal during its entire flight (and crash), we could identify its crash location. Unfortunately, we believe that the drone is sitting at the base of a steep, unstable moraine wall, and at the top of an unstable scree slope. The location is at extremely high risk for a rock avalanche, and is one that even the best mountaineers would do their best to avoid. Thus, we decided that rescue attempts would be ill-advised, and went home for the day.
Between the two days of flying, we now have 1,655 geotagged images (like the one below!) that span around 6km of Tasman Glacier, which we are currently processing into a DEM. Despite this setback of the crash, we hope to be back in action with a different plane soon. We'll keep you updated!