Only one company now remains in the US military’s effort to develop a heavy-lift transport aircraft capable of taking off from and landing on water.

Boeing subsidiary Aurora Flight Sciences is now the sole participant in the Liberty Lifter programme, an effort managed by the secretive Defense Advanced Research Projects Agency (DARPA) to develop a new logistics support capability.

On 9 May, Aurora won an $8.3 million extension contract covering continued work on a Liberty Lifter prototype.

Competitor General Atomics Aeronautical Systems was not selected to continue with the programme, after previously being chosen as a finalist by DARPA in February 2023. The agency confirmed General Atomics’ elimination to FlightGlobal on 15 May.

“Aurora Flight Sciences is the only performer remaining on Liberty Lifter,” says Christopher Kent, the naval engineer and DARPA programme manager overseeing the Liberty Lifter initiative.

“When we reached the point where we realised only one performer was meeting our aggressive schedule and technical goals, we streamlined the programme to continue to deliver innovation as soon as possible,” Kent adds.

Both General Atomics and Aurora had received a fresh round of development funding in July 2023, with each firm getting around $20 million to continue advancing Liberty Lifter designs.

Liberty Lifter - Aurora design - 16x9-960

Source: Defense Advanced Research Projects Agency

The latest Liberty Lifter concept sketch from Aurora shows some design changes, but the concept maintains core elements of a high-wing airframe powered by eight turboprops

Following its elimination, General Atomics described its Liberty Lifter submission as a “strong proposal” and wished DARPA success in continuing the programme.

“You always want to win and keep working on these things but, more than that, we just want to see the programme thrive and deliver a unique capability for the war fighter and the nation,” says C. Mark Brinkley, General Atomics’ director of communications.

Unlike traditional US military procurement programmes based around a competitive “down-selection” between two finalists, DARPA’s experimental development efforts are more flexibly structured.


Source: Defense Advanced Research Projects Agency

Aurora’s earlier concept was an aircraft with a canted high-wing and T-tail

Multiple participants can advance through the multi-phase process if they continue demonstrating technical promise and meet progress targets outlined by DARPA. If more than one proposal shows feasibility, and funding is available, the agency can opt to build more than one prototype.

“Efficiency is baked into the DARPA model, which maximises our opportunity to create transformational change,” Kent notes.

Successful technologies developed under DARPA research and prototyping programmes are not automatically moved into full-scale production and procurement, but can be made available for the USA’s uniformed military services to purchase separately, or adapted into subsequent offerings. The agency is credited with contributing to the invention of the internet and technology behind the Global Positioning System.


Source: Defense Advanced Research Projects Agency

General Atomics’ proposal featured a twin-hull and mid-wing aerostructure

DARPA also developed the first radar-evading stealth aircraft.

In the case of Liberty Lifter, the Pentagon’s technology incubator hopes to demonstrate “a leap in operational logistics capabilities” by delivering a prototype amphibious aircraft combining the versatility of seaplanes with the cargo-hauling capacity of maritime vessels.

“Although current sealift is very efficient in transporting large amounts of payload, it is vulnerable to threats, requires functional ports and results in long transit times,” DARPA noted in 2022 when it launched the Liberty Lifter effort. “Traditional airlift is much faster, but has limited ability to support maritime operations.”

Concept sketches of Aurora’s Liberty Lifter design depict a high-wing, mono-hull airframe powered by eight turboprops. While the core concept seems to have remained intact, there do appear to have been some changes since Aurora was selected as a finalist in February 2023.

While an earlier concept sketch depicted an aircraft with a canted wing and T-tail, the latest illustration shows an aircraft with a flat wing and hybrid tail design featuring elements of both a V- and T-shaped configuration.

The latest depiction also shows substantially larger vertical stabilisers extending downward from the wing tips, presumably for stability on the water.

By contrast, General Atomics had been pursuing a twin-hull, mid-wing concept using rear-facing propellers.

DARPA says Aurora is currently focused on design refinement and risk reduction activities ahead of a formal review in 2025. If that assessment – called a preliminary design review – is successful, Aurora will create a final aircraft design and begin constructing an airworthy prototype.

The test programme for the Liberty Lifter X-plane is to include static evaluations on land, float testing and eventually flight trials.

Assuming no insurmountable obstacles emerge, first flight of the Aurora prototype is targeted for late 2027 or early 2028, DARPA tells FlightGlobal.