In parallel, studies with the airframers will identify potential applications of the common core beyond 2020. “We will conduct quantitative assessments of AETD-derived propulsion systems,” says AFRL's Lewis.

GE, meanwhile, will begin high-pressure core tests this week under the Advent program. Rolls-Royce's LibertyWorks will begin testing its core in late November/early December, says Matt Meininger, AFRL's Advent program manager. GE's full engine is “75%-plus” complete and will go to test in July 2013, he says, while Rolls's engine is 90% complete and scheduled to begin tests in October next year. Pratt will deliver an adaptive-fan test rig—developed largely with company funds—to AFRL in February/March “to jump-start us [on AETD],” says Reed. Although Pratt lost the Advent competition, Meininger says AFRL was able to come up with more funding to help it modify an existing rig by adding a third stream to a two-stage fan, putting the company on a “fast track” to compete for AETD.

For Rolls, there was some consolation this week when it began tests of a high-pressure-ratio compressor demonstrator under AFRL's HEETE program, which aims to demonstrate technology to reduce specific fuel consumption by 35% for embedded engines in future subsonic transports and unmanned aircraft. GE has also delivered a HEETE compressor rig to AFRL, with testing expected next year.

Demonstration of a high-pressure core—compressor, combustor and turbine—is planned for 2016 under HEETE, with tests of a highly efficient turbine engine planned for 2019. Reducing SFC by 35% would increase transport-aircraft range by 50% and payload by 25%, and double the loiter time of intelligence, surveillance and reconnaissance UAVs, estimates AFRL.

Although funds are not available, the Air Force Research Lab would like to find a way to keep Rolls working on adaptive engine technology. “Each of the three companies has a unique architecture concept for the third stream,” says Jeff Stricker, AFRL Propulsion Directorate chief engineer. “They have three approaches to adaptive fans and how to vary the third stream with the two main flows.”

“We believe three-stream is the architecture for the next generation of aircraft,” says Lewis. “Of course we would like to keep all three approaches available to us.”