72 Engine dossier | UAVE 120 cc four-stroke Air cooling Minimising weight means the DS120 does not have water jackets or an oil sump. Instead, the engine’s fuel contains a small amount of two-stroke oil, with the unburned oil vapour passing down the piston’s sides to lubricate the bearings; fins about the block dissipate heat. Several parameters are also controlled via the ECU, such as cooling the engine internally by running the fuel slightly richer (if thermal efficiency should occasionally take precedence over fuel saving). To further moderate the engine’s temperature, UAVE developed a bolt-on heatsink, which affixes to the exhaust port, sitting in the airflow aside the engine bulkhead, to draw away and dissipate considerable heat from the cylinder head. These techniques and other optimisations to the finning were first developed to suit a number of meteorological flight services performed in India, not long after the management buyout, as temperatures on the tarmac and in the engine bay were naturally far higher in India than they had been in Britain, and especially the Arctic. “We also designed a big air scoop on the side of the aircraft, which feeds onto the airbox, so any air which doesn’t get drawn into the throttle body passes along the airbox and flows onto the cylinder head,” Slater adds. “West Wales Airport was where we first reached 10,000 ft, with a very aggressive climb. We took that experience to India, where we achieved the same target altitude. The customer there was very demanding, wanting to continually load the aircraft with more and more payload weight. “Eventually, there were 11 different instruments on the Prion, which meant a variety of complex integration challenges. We were also flying at our MTOW in hot, thin air – basically everything an aircraft hates for take-off conditions. But the project was successful, and it really helped us push our power plant further and harder than ever before.” Control and operation Also, after the buyout, the company sought to establish a testbed to cycle, measure and experiment with the UAV engine in a sophisticated manner, bringing in some new staff, including former racecar engineers to optimise its performance, efficiency and reliability against its weight and cost. “They diversified the test suite, and started working with different kinds of injectors, CFD approaches and exhaust types in a highly controlled test environment. Based on their findings, we started designing our own fuel-delivery systems, and went with an ECU from GEMS to control fuel-injection quantities and timings more precisely than before,” Slater says. “With our ecosystem of suppliers around Daventry and in Wales, we wanted to use an ECU from within the UK too, and GEMS have seen a lot of success in performance and rally cars. I also know of at least one other UAV in the UK that they supply ECUs to.” UAVE worked closely with GEMS to produce and optimise new ECU code vital to the precise monitoring and timing of the DS120’s injectors, and it has since been redeployed in other applications with the company’s blessing. December/January 2025 | Uncrewed Systems Technology The Prion Mk.3 and DS120 have operated in both the freezing climes of the Arctic and far hotter environments such as India; the latter meriting significant thermal-management optimisations (Image courtesy of Will Clark & Carson McAfee, British Antarctic Survey) The Prion Mk.3 is a STOL, fixed-wing, 3.8 m wingspan UAV, measuring 3 m long, with a typical operating weight of 30 kg and a standard payload capacity of 15 kg (hence a 45 kg MTOW). It is also referred to as the Dragon when marketed or flown in a defence context, or coded as the D15 when flying the standard payload capacity. UAVE also developed a new, wider wing for the UAV, with a 4.65 m wingspan, which has enabled a 25 kg maximum payload capacity. The aircraft is coded as the D25 for military customers when this wing is installed. A future D50 is in development, which will have a 100 kg MTOW. All three variations of the Prion or Dragon will run on the DS120 engine. Fuel capacity, depending on aircraft configuration, runs from 6.5 L to 15 L, with a cruising consumption of 1.1 L/hour at 80 kph airspeed. The UAV typically features a 28x14 three-blade, carbon-composite propeller, mounted at the upper rear of the fuselage. UAVE’s UAVs
RkJQdWJsaXNoZXIy MjI2Mzk4