Issue 39 Unmanned Systems Technology August/September 2021 Maritime Robotics Mariner l Simulation tools focus l MRS MR-10 and MR-20 l UAVs insight l HFE International GenPod l Exotec Skypod l Autopilots focus l Aquaai Mazu

62 Dossier | HFE International GenPod all the time, 7-8 hours a day, so they’d rack up their TBOs pretty quickly. “That inspired me to think of ways to make a ‘quick-replacement’ engine system, one that went beyond simply making a modular architecture of ‘bolted-on’ parts, because modularity has been a key trend for years now but it hasn’t actually made maintenance that much easier. It still takes a lot of time to remove modular engines from aircraft and take them apart.” Every GenPod features two thumb-tabs on the rear dorsal section that can be pushed to unlatch the system from its host aircraft’s fuselage (tipping it forwards so that the fuel and electrical lines can be accessed and disconnected). A third tab is installed at the bottom, which the GenPod sits stably upon after being unclasped, holding it in place for disconnection. The remaining connectors and engine components have been selected, customised and positioned to package the system to optimise the aerodynamic, thermal, electrical and vibratory properties of the GenPods. As West explains, “These solutions and the others in development all fit and connect to the same bracket, so for example if a UAV operator wants to lift more weight or cross distances faster with the same platform, they could swap out a GenPod 70 for a 100 in less than a minute, as the latter would give you a bigger power output but with no noticeable change in the vehicle’s centre of gravity.” System layout and connections The GenPod is designed to encompass all the necessary IC engine powertrain components for a UAV in a single turnkey package. At the front is an aluminium spinner, a Mejzlik carbon fibre propeller, and a generator, all mounted onto (and directly driven via) the engine’s power take-off which forms the core of the system. A carbon cover affixes to the top of the engine to suspend it securely within the housing and provide an outer surface that is protective and aerodynamic. The rear cover is a moulded plastic design containing a much more complex arrangement of lines and connectors. At the top is a fuel filter, below which is a circular engine connector input for interfacing with the autopilot. Underneath the engine connector is a generator connector output for supplying electricity to the onboard systems. “The engine connector is a relatively new product from Amphenol, one of their lightweight fully plastic items with high- quality gold-plated contacts designed for really secure tolerances in the pins,” West says. “They’re bayonet-style as well, so when you’re attaching a GenPod to your UAV you twist-lock the connection to the autopilot so it can’t come loose.” Other electrical connections throughout the GenPod are Omnetics products, which are constructed from Kevlar shells (with a melting point of 320 C) and gold- plated contacts at the connector and high-temperature Teflon insulation. “We were introduced to Omnetics’ lightweight connectors by customers of ours at Honeywell,” West notes. “One thing we’ve found is that the bigger and stronger your connectors, the worse the impact on your engine’s TBO, because more weight means more severe shaking from vibration, so we’ve opted for lightness over strength wherever we could in our connectors.” Instead of bare copper wiring, HFE has opted for silver-plated stranded copper alloy wire, as it sees the former as too much of a corrosion hazard and too prone to resistance-induced losses. Jackets from semi-crystalline plastics are used in the outer insulations to enable temperature tolerances up to 260 C as well as optimise strength, stiffness and chemical resistance. Grommets have been placed throughout the GenPod’s wiring August/September 2021 | Unmanned Systems Technology The latching system mounts onto the aircraft and consists of three tabs that unclip without needing tools