The requirements, posted on a federal website Wednesday, will drive the decisions of the five competing companies who hope to win the rights to build 350 advanced flight trainers and the associated systems to replace the legacy T-38 trainer. Interested parties must respond to the service by May 10.

The program is the first to issue requirements under the "Bending the Cost Curve"' initiative, a major staple in Air Force Secretary Deborah Lee James' plans for acquisition reform.

There are over 100 requirements included in the documents, but an Air Force news release said the emphasis is on three key components: sustained G, simulator visual acuity and performance, and aircraft sustainment.

Other capabilities include the need for in-flight refueling, a 10 percent reduction in fuel usage from the T-38, and a minimum of being able to take off at an 8000' runway length, 7400' density altitude, and 10 knot tailwind.

Notably, there is no requirement for a "Red Air" aggressor aircraft. While such a program was included in the out years of the fiscal 2016 budget request submitted by the service, Air Force officials have characterized that more as study money for future upgrades.

Which doesn't mean the service isn't looking at future capabilities for the T-X. Included in a series of questions posited to industry are "to what degree is your current design open/flexible to accommodation of future capability modifications" and another question asking whether there areany "limiting factors in your current design that would preclude future system modification" of wing pylons, radar systems, datalinks and defensive systems.

In February, Gen. Robin Rand, the head of Air Education and Training Command, said he was concerned about building in growth potential for the next trainer.

"We don't want buyer's remorse. It's a 50-year-plus aircraft," Rand said. "We think our requirements will allow the airplane to absolutely do those things. ... Will it have that capability [to upgrade in the future]? We think it will, but it's got to be done affordably."

There are five competitors aiming for the right to replace the aging T-38 fleet used by the service. The two clean-sheet designs are being put forth by a Boeing/Saab team and a Northrop Grumman-led coalition that includes BAE Systems and L-3.

The new designs will go up against a pair of legacy trainers in the form of Lockheed Martin's offering of Korean Aerospace Industries' T-50, and the T-100, a collaboration between General Dynamics and Italy's Alenia Aermacchi based on the latter's M-346 design.

The wildcard in the competition comes from Textron AirLand's Scorpion, a new aircraft designed for ISR and light-attack missions. Officials for the Scorpion program have said they plan to develop a trainer variant of their aircraft to compete in T-X.

The service marked $11.4 million for research-and-development funding for the T-X in fiscal 2016. That number rises escalates to $12.2 million in fiscal 2017, then jumps to $107.2 million in 2018, $262.8 million in 2019 and $275.9 million in 2020.

A contract award is planned for fall of 2017.

Twitter: @AaronMehta

Aaron Mehta was deputy editor and senior Pentagon correspondent for Defense News, covering policy, strategy and acquisition at the highest levels of the Defense Department and its international partners.

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