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50 Show report | Commercial UAV Show London 2019 fixing the prop onto the motor shaft and twisting it to lock it in place. The parts are CNC-machined from 7075 aluminium in order to achieve the micron-level tolerances required for an accurate and secure installation. “The mechanism was originally designed by Vulcan UAV, with functional improvements from us. We have also focused on testing and the key work of calculating the tolerances of the system,” explained Raam Sundhar from Mejzlik. “Downtime between flights can be significantly reduced by cutting the time spent replacing propellers, and since the mechanism allows you to rapidly remove props to shrink a UAV’s footprint before stowing it in a transport vehicle, folding propellers can be swapped out for fixed props. “That’s important because folding propellers are prone to problems with vibration and aerodynamic efficiency. We ran a study on folding propellers, and found the blades tended to deviate by around 7 º from their hubs, which contributes greatly to those aforementioned issues as well as other problems. “Folding propellers also tend to be heavier, and their weight distribution tends to be further from the centre of rotation. That increases the load during the acceleration and deceleration of the motors as the aircraft is stabilised. “The rate at which these rotational speed changes can be made is key to the performance and overall stability of a multi-copter. Also, the ultra-light propeller design from Mejzlik, combined with the low-radius quick-release hub, offers significantly reduced inertia, meaning great improvement in this area. “When compared to folding propellers, the reactivity improvements have been shown to be so great that using our quick-release mechanism can improve flight controller stability by as much as 25%, enhancing the performance as well as efficiency of the drive system.” Wings For Aid is a Netherlands- based company working to develop the required technologies for large- scale automated aerial logistics, to help communities that need humanitarian aid and disaster relief. The company exhibited its patented drop-box, which is designed to provide aerial deliveries of critical supplies such as blankets, water, purification tools, food, medicine and radios, without the UAV needing to land. “Humanitarian aid groups find last-mile delivery very problematic, so we’re aiming to bridge that gap with this box,” said Barry Koperberg. “It works without a parachute, which is important because parachute materials are non-biodegradable and would cause environmental damage in vulnerable areas. “The cardboard box has four air brakes – chute-like flaps – that extend from the top, and a crumple zone in its base, to help the cargo touch down safely, precisely and softly. That is critical, as each one needs to carry 20 kg of supplies.” Different box designs were built and tested in order to arrive at a biodegradable unit that would keep supplies undamaged while landing them in a target landing zone no larger than a tennis court. When released from the underbelly of an aircraft, the air brakes serve to reduce the terminal velocity of the box and stabilise its path through the air, to ensure that it lands precisely and on its crumple zone. The company also plans to operate its own eight-box/160 kg cargo UAV, as well as swarm-capable fleet management software to coordinate last-mile aid distribution on a massive scale. Both systems are on track for deployment this year. “The UAV will incorporate a release mechanism designed in-house to ensure that the cargo bay drops aid boxes exactly where we want them, accounting for wind patterns and other variables in real time,” Koperberg noted. “We tested our release and delivery technologies on an optionally piloted microlight aircraft to mature them before integrating them into the UAV, which has been developed through a coalition of industrial designers, technical universities and manufacturing partners. It will have February/March 2020 | Unmanned Systems Technology The Mejzlik propeller quick-release system Wings For Aid humanitarian air-drop