Pratt & Whitney says it has completed testing a three-stream fan in an engine with an F135 core as part of the U.S. Air Force Research Laboratory's Adaptive Engine Technology Development (AETD) program.

Modern military turbofan engines have two airstreams, one that passes through the core of the engine, and another that bypasses the core. Development of a third stream provides an extra source of air flow to improve propulsive efficiency and lower fuel burn, or to deliver additional air flow through the core for higher thrust and cooling air.

Using a third stream of air that can be modulated provides a balance for scenarios requiring both high-end acceleration and increased range, the company says.

The goal of the AETD program is to provide a 25 percent reduction in fuel consumption and a 10 percent improvement in thrust levels compared to today's combat aircraft engines.

The AETD fan test was conducted at the Arnold Engineering Development Complex, located on Arnold Air Force Base in Tullahoma, Tenn. Later in 2017, Pratt & Whitney plans to conduct additional testing on a new high efficiency engine core developed under the AETD program.