72 [CMM]. Naturally, controlling and validating the tolerances and geometries of every engine component is important. In the past we’d outsource the coordinate measuring, but that took too much time due to having to request the service, book a timeslot for the CMM, and transport our parts back and forth. Our validation times are much faster now.” Testing Four propeller dynamometer cells populate Suter’s basement testing facility. Stepping into the first cell, where the firm previously performed a 1000-hour endurance test of the TOA 288, one finds (surrounding the dyno) a 400 kW brake, a HVAC system for controlling cell temperature and pressure, an in-house-developed power-generation system, and a motorbike speed tester on the ground (so the racing projects and aviation business can profit from the cell). Some minor variations exist between the cells, depending on specific testing applications. One dedicated to testing the HF TOA 288-SDI, for instance, is designed to deal appropriately with the emissions from burning kerosenes. All, however, serve to perform breakins (including the initial wear needed to mate each piston ring to its cylinder) and final testing on every unit coming from the manufacturing rooms upstairs, and also to analyse new engine designs and improvements, including any new calibrations of the ECU (a multi-core system supplied by an undisclosed partner in Italy). As Alessandro Giussani, CTO at Suter, explains: “The engine brakes we use are classical eddy current brakes, which let you test the engine in a wide range of rpm and throttle combinations. Once we get the basic calibrations from those, we can then move the engine onto the propeller dyno to fine-tune those calibrations for specific propellers. “The heavy fuel-testing cell incorporates a carbon ventilation and filtering system for health and safety compliance, and a special cooling arrangement of blowers pointed to the exhaust system, to compensate for the fact that it is running statically and not on a moving aircraft. But, aside from those two factors, there’s no drawback to running heavy fuel engines in our dyno cells.” The cooling system is vital for simulated thermal management, as the air drawn by the propeller is insufficient to recreate airborne cooling conditions. Additionally, the ventilation system often keeps the cell’s air pressure slightly lower than ambient, not only helping to simulate altitude conditions but also preventing harmful gases from ‘wanting’ to escape outside the cell, potentially to where the test engineers sit. As well as measuring all output parameters for engine performance, including fuel consumption, the sensor arrangements in the test cells typically also track the pressures and temperatures found in the cylinder, crankcase and oiling system used in the heavy fuel engine (discussed later). In addition to watching the engines through windows, the testing engineers monitor four to five computer displays per cell, each featuring a software interface covering a different task. One tracks standard engine operating parameters, including CHTs, exhaust gas temperatures, manifold air pressures, and so on. The second monitor shows the test profile under way, and how far an ongoing test may have progressed through the overall duration (enabling parameters to be tracked and compared over time). The third displays the ECU’s engine-management software, thereby tracking component functionality and February/March 2025 | Uncrewed Systems Technology Suter’s testing cells include high power braking systems, HVAC systems, power generation systems and more (Image courtesy of the author) We work in motorsport and uncrewed aviation, where you have to push the envelope… testing our engines beyond what has been done before
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