Rolls-Royce low-emission combustion system enters flight test phase

Rolls-Royce has entered the final phase of testing its ALECSys (Advanced Low Emissions Combustion System) demonstrator engine, this time at altitude.

ALECSys is part of the UltraFan engine demonstrator programme, which offers a 25% fuel saving over the first generation of Trent engines. UltraFan, which is scalable for narrowbody or widebody aircraft that may be developed from the 2030s, is a key element of Rolls-Royce’s commitment to making aviation more sustainable. The UK engine maker believes gas turbines will continue to be the bedrock certainly of long-haul aviation for many years, although it will be able to run on 100% Sustainable Aviation Fuel from day one of service. In parallel, the engine maker said it is actively exploring potential options for hybrid-electric and hydrogen power solutions.


The demonstrator took to the skies attached to the Rolls-Royce Boeing 747 Flying Test Bed in Tucson, Arizona. The test programme has included flights up to 40,000 feet as well as a number of engine relights at different conditions, all of which have been successful.

The lean-burn combustion system improves the pre-mixing of fuel and air prior to ignition, enabling cleaner combustion of the fuel, which results in lower NOX and particulate emissions.

The ALECSys engine demonstrator has previously completed a comprehensive set of ground tests, including icing, water ingestion, ground operability, emissions and running on 100% Sustainable Aviation Fuel (SAF).

Simon Burr, director of product development and technology, civil aerospace, Rolls-Royce, said: “This flight testing is a key part of our drive to not only improve engine efficiency but all aspects of environmental performance. It is part of the wider Rolls Royce sustainability strategy, which also includes support for the increased use of sustainable aviation fuels (SAF) and intensive research into alternative propulsion architectures and technologies.”

The ability to test ALECSys low-emissions technology in flight will allow the verification of altitude operability performance and provides experience of operating a lean-burn system to maximise maturity ahead of a future entry into service.


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