Two enthusiasts have extended their world record for UAV speed, writes Nick Flaherty.

The air-cooled Blackbird UAV achieved a speed of 626.4 kph (389.2 mph), breaking their previous record of 580 kph (360 mph). The peak speed was actually higher at 655 kph (407 mph). The speed was recorded over four runs using four battery sets.

The first run at an altitude of 100 m into the wind with a standard battery at 4.20 V achieved 588 kph (365 mph), while the second run achieved 621 kph (386 mph). Boosting the voltage to 4.30 V produced a speed of 599 kph (372 mph) into the wind and 655 kph (407 mph) with the wind. This created the average value that set the record.

The UAV was built with 3D printed elements using polyethylene terephthalate glycol (PETG) with carbon fibre. PETG is a durable, clear thermoplastic polyester that combines the best of polyethylene terephthalate and acrylonitrile butadiene styrene. This resulted in a weight reduction of 80 g, down to 320 from 400 g, as well as a stronger structure.

This allowed improved aerodynamics with custom-printed components.

The UAV uses air cooling rather than water cooling to save weight. The motors were operating at 40–60 C with the batteries at 50–60 C for the standard packs and 92 C for the higher-voltage operation.

The propellers were cut down from 177 mm (7 in) to 152 mm (6 in) to obtain higher rpm for a more efficient thrust-to-weight ratio.