The DARPA Wing-in-Ground (WIG) cargo aircraft Request for Information (RFI), released on 18 August, 2021, can also be described as an Russian Ekranoplan (Russian – “screenglider”), essentially a plane that flies over a surface by gaining support from the reactions of the air against the surface of the earth or water to lift up the bottom of the wings, or a “hoverplane.” A WIG plane can be characterized as more of a very low-flying “hoverplane” (think sea-skimming at Anti-ship cruise missile’s altitude compared to a supersonic fighter plane’s high-flying altitude) that can skim over rough seas and yet stay low enough on the horizon for tactical and potential radar and certain missile evading purposes.
The DARPA Tactical Technology Office’s (TTO) WIG RFI states that, “Conventional strategic airlift platforms provide high speed, but require long prepared runways and have limited capability to support maritime operations. Vertical Takeoff and Landing (VTOL) and other maritime aircraft have limited range / payload capacities and are dependent on shipboard or shore-based servicing and launch and recovery infrastructure. WIG vehicles achieve increased aerodynamic efficiencies and address many of the operational limitations of traditional sea and air lift platforms in maritime theaters, but they are unable to operate in high sea states and have limited capability to avoid collisions in congested environments. DARPA is interested in the design of a new class of vehicle that addresses the major operational limitations of traditional air and sea lift platforms.”
The DARPA WIG aircraft RFI has these requirements:
- “Takeoff and land in the water (up to Sea State 3) for runway independence
- Maximize flight time in ground effect for increased range, endurance, and
- Extended out of ground effect flight capability for obstacle avoidance, flight over
land, weather avoidance, etc.
- High sea state operation for in-ground effect flight as well as takeoff and landing
and extended on water operations
- Low-cost manufacturing techniques and design choices (e.g. unpressurized
- Large operational payload (100+ tons) and capability of carrying multiple
Potential mission applications include:
- “Expeditionary Advanced Base Operations (EABO)
- Distributed Maritime Operations (DMO)
- Distributed logistics and logistics under threat operations
- Combat Search and Rescue (CSAR), on-site triage, mass casualty rescue
- Amphibious operations
- Unmanned vehicle operations
- Low payload, long duration Arctic patrol flights.”
Naval News Comments
For purely speculative analysis purposes for this article, DARPA’s RFI did not mention if this concept is open to national, academia, and international contenders, so one can assume that the RFI applies to all interested and qualified parties.
Naval News reached out the DARPA asking for more information regarding the RFI such as additional requirements, performance specifications (speed, range, ceiling), artwork, data, models, possible examples, intended users and participants. A DARPA Public Affairs spokesperson replied, “This is just an RFI at this point, so the goal is to seek ideas without prejudicing them with our own. Therefore, everything we want to say right now is in the RFI.”
DARPA did not respond to Naval News’ questions on if the WIG can be an amphibious seaplane that can fly at higher altitudes or is restrained to a WIG sea-skimming aircraft, or if the WIG can have a floodable well deck, or even be armed; the spokesperson reiterated that DARPA did not want to bias the RFI.
A good WIG aircraft example is Boeing Phantom Work’s Pelican, designed around early 2002. The Boeing Pelican concept shows how massive such a WIG aircraft can exist (see graphic comparing the Pelican to a Boeing 747 commercial airliner) to ferry U.S. Marines and their armored Amphibious Combat Vehicles (ACVs) to shore, or even to launch and retrieve the ACVs in calm waters if the WIG is equipped with a floodable cargo well deck.
The BAE Systems’ U.S. Marine Corps’ (U.S.M.C.) ACV can carry 10-13 Marines in the passenger compartment in addition to a crew of three, launch from twelve miles off shore, and swim in at 8 knots. The Marines intend to purchase around 573 ACVs. With a gross weight of 67,500 pounds (30,617 kilograms) or 33.75 tons, a single DARPA WIG RFI aircraft can carry three ACVs if cargo-rated at over 100+ tons. (Note that the Boeing Phantom Works’ Pelican WIG concept was theoretically meant to carry a payload of 2,700 tons!).
If DARPA’s WIG RFI is seeking a cargo carrying capacity of over 100+ tons, or 200,000-plus pounds (90,718 kilograms), this Duotech shareware graphic showing U.S. Air Force’s cargo plane payload weight comparison comes in handy to determine the possible fuselage size of the DARPA WIG.
Thus, DARPA, in theory, seeks a WIG plane fuselage longer than the C-17’s 174 feet (53 meters) in length. Wingspan length cannot be predetermined because the WIG aircraft requires a different wing configuration for flying in “ground-effect.” Also, do note that the U.S.M.C.’s ACV each weighs a lot less than the 71.2 tons each for the U.S. Army’s M1A2SEPv2 Main Battle Tanks (MBTs), respectively. The U.S. Marines have since divested of their M1A1 MBTs that are not amphibious.
While the DARPA RFI allows much speculation at this early concept design stage, some design features derived from other in-service Ekranoplans and amphibious seaplanes around the world can provide insight and glimpse into a U.S. WIG aircraft design. For propulsion, propellers or turbofan engines will have to be mounted in such a way (higher up for jet engines) as to prevent seawater and sea spray from entering the intakes and fouling the combustion process. A boat hull and floodable cargo deck is preferred for landing on the water to disembark amphibious vehicles and small boats, but the FY2021 DARPA WIG RFI made no mention of amphibious operations, just to land and take-off from water so hull floats might suffice.
DARPA also declined to comment to Naval News on if this WIG RFI is the same or different request from the U.S. Special Operations Command’s (USSOCOM) Virtual SOFIC 2021’s interest in an amphibious cargo plane. Furthermore, the end user service branch (U.S. Navy, U.S.M.C., U.S. Air Force, U.S. Special Forces, and U.S. Coast Guard) is unknown although this WIG plane design can theoretically serve many U.S. military branches. Also undetermined is if the received DARPA WIG RFI concept designs will be distributed with some concepts going towards the USSOCOM amphibious seaplane concept, the U.S. Coast Guard CSAR, and other designs to the conventional airlift forces for more than one WIG aircraft prototype.
The DARPA WIG RFI can, in theory, be armed, similar to the U.S.M.C.’s KC-130J “Harvest Hawk” with rockets, smart missiles and bombs, or like the USSOCOM AC-130 attack gunship with autocannon, (future) laser, and a howitzer. Again, DARPA declined to comment to Naval News’ question on if this is a design possibility, citing DARPA’s WIG RFI neutrality towards incoming concepts. In terms of survivability, the DARPA WIG RFI made no mention of engine exhaust suppression, Chaff/Flare dispensers, Early Warning and Electronic Countermeasure sensors and jammers, communications, night vision, armor plating for the cockpit and vital systems, government, HVAC and deicing for Arctic operations, furnished equipment, Anti-Missile Missiles and situational awareness. External and internal 360-degree situational awareness fuselage cameras might be a benefit for amphibious operations if the WIG can indeed land and conduct amphibious operations, especially at night.
Although still very preliminary and in the nascent concept and research stages, if the DARPA WIG RFI does become an official U.S. government Program of Record and the Wing-in-Ground Effect aircraft is indeed produced, the Department of Defense (DoD) would most likely need WIG aircraft infrastructure such as new WIG hangars, WIG seaports, shoreline ramps, new piers, WIG maintenance depots, new WIG bases, and/or potential WIG ship tenders.