Unmanned Systems Technology 020 | Alpha 800 I Additive Manufacturing focus I USVs insight I Pegasus GE70 I GuardBot I AUVSI Xponential 2018 show report I Solar Power focus I CUAV Expo Europe 2018 show report

23 including the spark plug, drive belt, the ‘silent block’ vibration-absorbing mounts for equipment, and the fuel filter, all at intervals of 50 flying hours. The rotor blades only need to be tracked and balanced after assembly. “We do that before delivery,” Escarpenter says. “Then, during the life of the aircraft, if there is no disassembly of the rotor and links, the configuration will not change.” The engine is replaced after 100 flying hours and requires no scheduled maintenance during its service life, Escarpenter says. He adds that the engine is fixed to the structure with eight bolts, and swapping it for a new one takes about 30 minutes. At 200 hours, some deeper maintenance is carried out by Alpha itself, and involves replacing components such as bearings and servos. The Futaba Industrial servos that Alpha uses, for example, have a mean time between failure of 300 hours, so changing them at the 200 mark is a means of building in a large safety margin. Rotor system design The semi-rigid, two-blade main rotor head features glass-reinforced plastic (GRP) blade grips, into which the blades are fixed through lead-lag hinges. The grips themselves are mounted on a spindle that passes through the hub at the top of the main rotor shaft and accommodates pitch changes. There are no flapping hinges. Each blade grip has an integral pitch horn, the position of which is controlled by a pitch link that is attached to the rotating (upper) half of the swash plate with ball joints. The non-rotating (lower) half of the swash plate is free to tilt in any direction around the main rotor shaft to provide cyclic pitch changes, and vertically up and down to provide collective pitch changes. The blades are made from carbon fibre with a high-density foam core. They are covered with a ‘shark skin’ drag-reducing coating and have mildly swept tips. They also feature a standard (undisclosed) Alpha Unmanned Systems Alpha 800 | Dossier Unmanned Systems Technology | June/July 2018 Main rotor controls include the fixed lower and rotating upper portions of the swash plate, and links from the redundant servos beneath and to the pitch links above (Author’s image) Alpha chose a conventional helicopter configuration for its greater aerodynamic efficiency over multi-copter alternatives (Courtesy of Alpha)