The Service-Drone Multirotor G4 Skycrane V2 octocopter is the German manufacturers top-of-the-line, heavy-duty lifter. From the factory this model lists a 14.4 lbs. max payload capacity. However, after experimenting with Skycrane load capacity, Hawk Aerial’s R&D team set out to find it’s true lift capabilities – manufacturer specs are many times lowered for safety reasons.
The test Service-Drone Skycrane was unmodified and powered by twin 5-cell, 8000 mAh, 18.5 volt LiPo batteries capable of a 150C discharge rate. In order to keep the test relevant to observers, we wanted to lift common, household items in the payload test. We selected a few standard red mason bricks weighing in at 5 lbs and 3 oz each plus the securing ratchet straps.
Initially, we secured two bricks to the airframe with high-tension lashing rope. On first attempt, all assists were enabled including GPS position hold, compass directional hold, bank/acceleration limitations and barometric altitude hold. However, as we throttled up, the altitude hold system was not accustomed to the heavy payload. The system rapidly increased motor RPM to lift off the ground, cut power once airborne (roughly 1 foot above the ground) and didn’t account for how quickly the aircraft would drop, allowing it to just barely touch the ground before throttling up again. This produced a pogo effect before we manually shut the motors down completely. To counteract this effect, we turned the altitude hold assist off and reattempted flight. This time the Service-Drone Skycrane lifted the payload off the ground with ease and still felt very nimble in the air.
Next, came a three brick payload, crossing the manufacture-recommended threshold. The three bricks and racketing strapping system securing the load to the airframe totaled just about 17 lbs. Just as before, we kept the altitude hold assistance system off and reattempted flight. Liftoff required quite a bit more throttle than in the previous test but the aircraft lifted off the ground very controllably.
Once airborne with the motors running at roughly 60% power, the Skycrane was still VERY maneuverable. We conducted aggressive lateral direction changes and steep, banked turns at an altitude of roughly 20 feet above the ground (manually modulated). The aircraft was very nimble, smooth and showed no signs of stress nor interrupted flight. Our 5-minute continuous flight tests hauling this 17 lb payload drained the batteries down to just over 60% of their capacity. From this, we calculate a flight time of roughly 8 minutes with this extreme payload while keeping the battery level in a safe zone (above 40% of capacity).
Next up 20 lbs. Stay Tuned.