Liberty Lifter X-Plane: The strategic heavy lift aircraft for US forces

DARPA's Liberty Lifter X-Plane Program enters Phase I
Ameya Paleja
The Twin Hull concept from General Atomics
The Twin Hull concept from General Atomics


Defense Advanced Research Projects Agency (DARPA), the U.S. Department of Defense's research and development agency, has picked General Atomics and Aurora Flight Sciences as two teams for the Phase I of its Liberty Lifter X-Plane program, a press release said.

The Liberty Lifter X-Plane program envisages a long-range, low-cost seaplane capable of strategic and tactical heavy-lift. The aircraft will be much like a flying boat with the size and capability of the C-17 Globemaster III but will be used independently of the runway using the Wing-in-Ground (WIG) Effect.

The WIG effect enables an aircraft to move over a surface by gaining support from the reactions of the air over a ground or water surface. The effect uses the forward velocity of the body to generate lift and experiences lesser drag, and the wing works closer to the level surface. This is the principle that makes hovercraft work but it can also be used to help airplanes fly.

The Liberty Lifter X-plane

The Liberty Lifter program intends to provide a leap in an operational capacity for U.S. forces as they acquire the capabilities of strategic and tactical heavy lift over water surfaces. This is rather important as China looks to flex its muscles in the South China Sea and has also demonstrated an amphibious cargo aircraft the size of a Boeing 737.

As per its recent press release, DARPA is looking at the Liberty Lifter to be boat sized plane with the ability to take off and land in Sea State 4 and sustained on-water operation in Sea State 5. In plain speak, this translates to small waves and moderate waves which go on to take more pronounced long forms.

Previously, DARPA has stated that it is also looking at its Liberty Lifter to be operational in the turbulent seas. However, in this phase, the agency is content with small-moderate waves, since the aircraft is also expected to demonstrate extended flight close to the water surface and fly out at altitudes up to 10,000 feet above sea level.

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Concepts for Liberty Lifter

Liberty Lifter X-Plane: The strategic heavy lift aircraft for US forces
One of the design concepts for the Liberty Lifter X-plane

The two teams selected for Phase I have showcased two different design concepts of the X-plane program. General Atomics, which is working with Maritime Applied Physics Corporation, has set a twin-hull, mid-wing design to optimize on-water stability and will be powered by twelve turboshaft engines.

Aurora Flight Sciences' design which it has developed working with Gibbs & Cox and ReconCraft is more conventional with a single hull, high wing, and eight turboprop engines.

During Phase I DARPA will work with both teams to refine the proposed designs by the operational needs. Out of the 18-month contract, six months have been reserved for conceptual design work and nine months for design maturation. A preliminary design review will be carried out at the end of this period. At the same time, an additional three months have been assigned for manufacturing planning and test/demonstration planning reviews, the press release said.

Mid-2024, Phase I will transition to Phase 2 with the teams working on manufacturing a full-scale demonstrator of the Liberty Lifter X-plane.

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