Diesel On Track To Replace Turboshafts On Light Helicopters
The diesel engine demonstrator, which may replace turboshafts in light helicopters, is on track for flight tests on a Eurocopter EC120 in the second half of next year. It will feature a power-to-weight ratio between those of a general aviation diesel and a turboshaft. The engine is part of the Green Rotorcraft integrated technology demonstrator (ITD), itself part of Clean Sky, the European Union’s €1.6 billion ($2.1 billion) joint technology initiative.
The project has passed technology readiness level 3 (TRL 3), meaning the proof-of-concept has been validated. The project is well funded, at €9.4 million ($12 million) over the 2010-2015 period. A first attempt, in 2009, had been notably underestimated, at just €3 million ($3.9 million).
The power-to-weight ratio is a critical requirement and thus the main challenge. Aviation uses turbine engines because they are light. According to project officer Sébastien Dubois, Green Rotorcraft’s diesel demonstrator will have a power-to-weight ratio of 0.9 kg/kW (1.48 lb/shp). This has to be compared to 1.5 kg/kW (2.47 lb/shp) for a diesel powering a light fixed-wing aircraft and 0.4 kg/kW (0.66 lb/shp) for a turboshaft.
France-based Teos Powertrain Engineering is employing its expertise in car racing to design a light power pack, including the engine itself and its cooling system. Meanwhile, Austria’s Austro Engine is handling installation and certification, because it has experience in diesels for light fixed-wing aircraft. The demonstrator engine’s power will be 330 kW (442 shp), below that of the EC120’s usual Turbomeca Arrius 2F at 504 shp.
Initial engine tests were planned to start last month. Eurocopter expects to receive the first engine in June. The critical design review on the modified EC120 airframe that is to support the flight tests, which took place in January, validated a TRL 3 level, Dubois told AIN.
In September, an engine will be integrated into an iron bird (in fact, an EC120 airframe). The iron bird will start working at TRL 4 (components in a laboratory environment) in January 2014. Then, ground testing with the modified EC120 is scheduled for the second quarter of 2014. This will validate TRL 5, in a representative environment (on the ground). At 39 months from launch to first ground test, the development cycle will have been very short, Dubois emphasized.
Flight testing should commence in the second half of 2014, culminating, at TRL 6, in a flying prototype in a representative environment.
The main benefit of diesel technology is expected to be in fuel burn, which should be lower by at least 30 percent compared to that of a turboshaft on a given mission. On a future helicopter optimized for advanced diesel engine technologies and incorporating exhaust-depolluting systems, the gain could exceed 40 percent, and NOx emissions would be cut by 50 percent.