Aerion’s next move in the development of the supersonic AS2 trijet aircraft is to select a propulsion systems supplier, says chief executive Doug Nichols.

The decision is the most pivotal step in the project since Aerion last year cancelled the original twinjet design powered by Pratt & Whitney JT8D engines and unveiled the larger and longer-range AS2.

The AS2 design imposes uniquely challenging requirements for a propulsion system, Nichols acknowledges.

While commercial turbofan engine manufacturers have focused on developing ever-higher-bypass and higher-pressure-ratio systems, a supersonic engine requires a comparatively low bypass ratio and low pressure ratio in the compressor, Nichols says.

That puts the engine architecture closer to the category of military turbofan engines, but the commercial Aerion application requires better fuel efficiency and significantly lower take-off noise than a typical military aircraft engine, he says.

Despite the design requirement challenges, Nichols is optimistic about signing a deal with an engine supplier by the end of the year. The company has several options with both commercial and military engine suppliers, Nichols says.

Each of the AS2 engines will be rated at a roughly 16,000lb-thrust, but the lower bypass ratio means the core will sized closer to 30,000lb-thrust level for a modern commercial turbofan.