Dan Edwards, a grad student at North Carolina State University, has set a new world's record for an autonomous glider flying without power from thermal to thermal. On April 18th, his 5m glider flew 29.4 miles cross country
in a flight that lasted 68 minutes, entirely without power or manual control.
The glider uses a Cloudcap Piccolo off-the-shelf autopilot, but the really smart stuff was the thermal seeking algorithm, which you can read more about here
Dan narrates the record-setting flight:
"The first flights were quite uneventful and downright disappointing. Perhaps with the low humidity and low wind, the thermals were just not organized. Adam tried valiently to catch just one medium thermal to maintain altitude and break through the low-level stuff. No birds were out flying and the completely blue sky was an ominous omen that the air just wasn't moving up today. But Blipmaps predicted today would be a 400ft/min thermal day at 2pm, so were holding our breath.
Finally around 1:30 we had success catching a single good thermal. Almost immediately, we moved over to auto-soaring and Adam watched as the plane climbed out on its own to over 3000ft. At this point, we decided it was time to get in the truck and move out. The first turn is a roughly 2mi flight over a swamp, but 3000ft is about appropriate to safely make it beyond the swamp even if we found no other thermals. I set the aircraft to track waypoint 0, officially starting the flight around the XC course. The plane crossed the start road at 1:47pm.
Off we darted in the little pickup. The plane had worked itself now to over 4000ft, so we were quite confident starting down the first leg. Adam coordinated with Craig to drive ~45mph in order to get in front and stay in front of the plane (we like looking backwards to the plane). After moving through waypoint 0, the vario was calling mostly sink and dutifully speed to fly let the plane move out and stretch its speed legs. What seemed very quick, we made the first turn at 1:51pm and the plane was cooking. It cruised downwind East for leg 2 also without stopping, blowing down the course and hitting turn 2 at 1:55pm, completing the first 4.0 miles in 8 minutes.
At this point, we were a bit nervous, hoping the plane would be able to find another thermal to gain some of the altitude back. From last flight test, we tweaked values on a curve that defined what strength thermal the plane would stop for at various altitudes. This curve was designed to keep the aircraft over 2500ft and cap out a bit over 4000ft. As the plane descended after turn 2, the minimum strength threshold came down and the ALOFT code saw a small upcoming thermal, then latched into it, and then proceeded to start orbiting. The thermal did get better as the plane got higher, so it stayed above the up-moving minimum threshold as the plane climbed higher. At once again over 4000ft, the thermal finally was mighty strong still, but the moving threshold said it was time to move on, so the plane turned out of the thermal and started along the course again.
This is how it went ... stop and watch the plane thermal, see the soaring mode unlatch, hear the plane leave the lift and start hitting sink, watch the plane start picking up speed and moving quickly to the next thermal, hear the lift getting better and check what the current minimum threshold was, stop and watch the plane thermal.
After completing lap 1, the plane was way in the sky at over 3000ft, so we decided it was safe to commence another lap. And then we completed another lap and realized we were still carrying 3000ft at the end and decided to go for yet another! Batteries were holding steady.
On lap 3 about 1/3 of the way through, the plane went through a monster hole of sink and sped up to between 35 and 45kts airspeed. This was also the downwind leg, so we had to chase forward at 65mph in the truck. The plane lost a whole lot of its altitude and was the lowest yet, around 2300ft. I started having visions of landing out. But then the plane made a little lurch, the vario stopped drooping low tones, and speed to fly slowed up a bit. Almost all of a sudden, we heard the vario start chirping. The plane pulled into an orbit and the vario was happy, very happy. In fact, the energy rate readings I was getting were off-scale high, pegging my meter over 19.7ft/s (6m/s) climb-rate! It only held this rate for several seconds, but now I know I need to up my limit! This thermal put us well back up to 4300ft and we knew we had lap 3 in the bag.
It was also about this time we made a call that we knew we had enough altitude to make the field. So, I hit the "soaring off" button, still leaving speed to fly and other stuff active. This allowed the plane to not worry about stopping to orbit, but created a dolphin-soaring type cruise. A few minutes later, we were back to the start/finish line and crossed the threshold at 2:55pm exactly. Whew!
I need to clarify and state for the record I did not touch the soaring computer this ENTIRE flight except for two times: 1. activate soaring mode; 2. deactivate soaring mode. The ENTIRE flight was on autopilot control, all 29.4 miles. On the Piccolo Command Center, the most I did was remove the hold waypoints as we approached them, because they were not needed for this version of flying the course. This did not affect the aircraft's flying and certainly would not have helped anyway. For the record, 29.4miles was autonomous and fully computer-controlled soaring. "