Unmanned Systems Technology 007 | UMEX 2016 report | Navya ARMA | Launch & recovery systems | AIE 225CS | AUVs | Electric motors | Lethal autonomous weapons

44 Nets are among the simplest UAV- catching systems and also effectively provide zero-length recoveries. However, they can cause entanglement and damage, and tend to require additional energy-absorbing mechanisms such as tearaways. Propellers tend to suffer most damage, although pusher propellers are much less vulnerable. Under arrest Arrestor wires have been used for decades to stop heavy manned aircraft on carriers, with three or more wires stretched across the deck at the stern to catch the tail hook. This also works with unmanned combat air vehicles (UCAVs), as the US Navy proved in 2015. However, arrestor wires can be deployed vertically as well, a solution that has been proved practical in many naval operations over recent years as it takes up far less deck space. Using differential GPS and a data link, perhaps enhanced by Real Time Kinematics algorithms, the UAV catches the wire with a wingtip-mounted hook. This is a very rapid zero-length recovery, if rather a rough one, and requires a crane or boom and a means of paying out some line under tension to soften the impact. This solution is also restricted to fairly small UAVs. The vertical arrestor wire has also recently been successfully demonstrated as part of a novel system in which a large quadcopter UAV is used to launch and recover a fixed-wing UAV. For launch, the quadcopter lifts its passenger to a suitable launch altitude and releases it, while for recovery it suspends the arrestor wire underneath, waits for the UAV to snag it, then lowers it gently to the ground. Flying aircraft carrier Re-purposing proven technologies is a well-established route to successful innovation, and adapting aerial refuelling technologies to enable large aircraft to launch and recover small UAVs is one that fits this category. There are two main engineering challenges involved – the speed difference between the mothership and the UAV, and the turbulent air behind the larger aircraft caused by its wake and its propeller/jet wash. The first might restrict the technique to faster UAVs, although helicopters regularly refuel from C-130s, and many UAVs can achieve similar speeds. Paying a long hose out behind the tanker aircraft with the fuel connection in the centre of a drogue, into which the receiving aircraft inserts a probe, is one of two time-honoured solutions to the second. (The other involves a rigid boom that an operator aboard the tanker guides into a receptacle on the receiving aircraft.) UAVs can refuel by the probe-and- drogue method autonomously now, as proved last year by the US Navy’s X-47B UCAV demonstrator and a Boeing 707 tanker. Using a cable and a drogue, small UAVs could be drawn into underwing April/May 2016 | Unmanned Systems Technology The Boeing Insitu SkyHook takes the arrestor wire idea and turns it through 90° to produce a near-zero length recovery system for small UAVs (Courtesy of US DoD) Taking techniques and technologies from probe-and-drogue air-to-air refuelling, Armin Strobel has proposed a means of enabling launch and recovery of UAVs from transport aircraft (Courtesy of Armin Strobel)