A recent report from CNN discusses a new flying boat concept that could transport up to 2,000 people across the Atlantic Ocean while reducing airport congestion and noise. This could be an amazing aircraft, unlike anything that’s ever flown before, but don’t be fooled into thinking the idea is commercially viable.

Designed by Drs. Errikos Levis and Varnavas Serghides of Imperial College London and Frederick University, the idea is a scalable flying boat design that could eventually produce several aircraft in varying sizes. Their concept has up to eight engines and uses a blended wing body planform. It also has a V-shaped hull to allow takeoffs and landings from water, and could be powered by environmentally-friendly hydrogen fuel.

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The designers describe an aircraft capable of transonic flight, with a cruise speed of Mach .80 and a cruising altitude of 35,000 feet. This would maximize flight efficiency and minimize specific fuel consumption while voiding the need for a vertical tail. Their aircraft would use high-bypass turbofan engines like those found on modern airliners, only installed atop the aircraft’s trailing edge instead of under the wings.

The History Of The Flying Wing

Blended wing body aircraft are not new, having evolved from flying wing designs in the early 20th century. The flying wing concept (which has no explicit fuselage) dates back to the golden age of flight, when the Nazis developed the idea to a high degree during and before World War II. The jet-powered Horten Ho 229 flew in 1944 and was capable of delivering 2,200 lbs. of ordnance across the Atlantic Ocean before returning to base in Germany, although it never did.

Northrop YB-49 flying wing in flight.

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American Jack Northrop also demonstrated the idea with the propeller-driven XB-35 in 1946, which eventually became the jet-powered YB-49. Due to development and flight control issues, Northrop abandoned flying wing designs shortly thereafter (but not before considering a passenger version of the YB-49 complete with aft-facing observation lounge), only to reinvigorate the idea for the Air Force’s Advanced Technology Bomber competition in the 1980’s. That competition lead to the B-2A Spirit production aircraft, more commonly known as the “stealth bomber.”

Today, Northrop Grumman is one of two teams (the other is a combined effort by Lockheed Martin and Boeing) competing for the Air Force’s shadowy LRS-B competition. Both entries are purported to be flying wings, and one of them may have been spotted over Texas and Kansas last year. A winner of the LRS-B competition is expected to be announced later this year.

Unmanned combat aerial vehicle designers have long gravitated towards flying wing designs. Blended wing bodies such as the proposed flying boat differ from flying wings by having a distinct body structure, their wings blended (hence the name) into the fuselage.

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A 1994 feasibility study by NASA, industry and academia investigated blended wing body airliners, ultimately producing a Boeing concept called BWB-450, which was theoretically capable of carrying 450 passengers and scalable up to 800. The BWB-450 was purported to have 32 percent lower fuel burn per seat than an Airbus A380, along with a 30 percent reduction in total parts count. Further, the BWB-450 was said to offer “the potential for a significant reduction in environmental emissions and noise.”

The flying boat concept somewhat resembles Boeing’s unmanned X-48B Blended Wing Body (which was never designed for takeoff and landing on water and should not be mistaken for a flying boat) aircraft from 2007, a product of Boeing’s Phantom Works advanced technology division.

Where It Works

The 400 pound X-48B demonstrator featured three jet engines producing 50 pounds of thrust each and had winglets that served as rudders for roll and yaw control, a trait the flying boat concept appears to share based on the available schematics. Both the X-48B and the proposed flying boat feature engines situated on top of the aircraft, which would better deflect noise from and reduce water ingestion into the engines during takeoff, landing and taxiing.

A 2010 NASA study found that a hybrid wing body aircraft model based on Boeing’s Blended Wing Body concept “had the potential for a significant step change reduction in aircraft noise.” However, testing also noted that on configurations of hybrid wing body test articles that had engine exhaust aft of the trailing edge offered limited potential for noise reduction, as the trailing edge prevented shielding of the engine noise being radiated rearward. The flying boat concept appears to have engines aligned flush with the trailing edge, so it remains to be seen if this is a real advantage.

NASA’s ongoing Environmentally Responsible Aviation program seeks to neutralize adverse environmental impacts (namely, noise and emissions) from expanded aviation activity in the next two decades. Northrop Grumman submitted a flying wing airliner concept to the ERA program in late 2011 that bears some resemblance to their B-2 bomber. Boeing also submitted a blended wing body design evolved from the X-48 program. These concept aircraft may reveal what airliners look like 20 years from now, but the ERA program does not take into consideration any aircraft taking off or landing from water.

Aircraft noise has been an issue for decades and has been shown to negatively impact human health. Groups such as the International Civil Aviation Organization (ICAO), European Aviation Safety Agency (EASA) and the FAA aim to reduce aircraft noise through regulation.

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As a result, modern airliners have become remarkably quiet, especially when compared to older aircraft. The flying boat designers acknowledge that the aviation industry is under constant pressure to reduce noise, citing this as a reason for moving airports offshore. However, a flying boat with eight engines operating off the coast surely will not be quiet, and could actually add noise to coastal communities that were previously sheltered.

Where It Doesn’t Work

While the proposed flying boat would not be limited by traditional runways and could conceivably land anywhere with calm seas, one of the stated goals in the proposal is to reduce the need for extensive infrastructure. An aircraft large enough to carry 2,000 people plus luggage disembarking in an organized fashion while on the water would certainly involve extensive infrastructure. Any floating terminal and related apparatus for these proposed flying boats would no doubt be mammoth structures, and would need to be placed immediately along or directly offshore from some of the world’s most valuable coastal real estate.

Landing on water is itself a major challenge. A liquid landing surface is quite literally a fluid environment, and everything from floating obstacles to currents become crucial variables to which a pilot must attend. The proposed flying boat designers note that, “coastal areas are often congested and it is fair to assume that seaplanes will be operating from some predefined area, kept off limits to maritime traffic in the interest of safety.” Their flying boat would likely have a highly advanced cockpit with a radar altimeter and many automated functions, and could benefit from virtual runways visible from the aircraft’s synthetic Enhanced Vision System. However, the ability to detect sub-surface debris and other obstacles is not addressed, and could be a major concern.

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Modern airport operating areas are highly secured, and for good reason. Threats made against airliners and transportation infrastructure are constant and taken extremely seriously. To ensure safe operation of the proposed flying boat airliner, an enormous body of water would need to be safeguarded from threats.

How many areas in the world could persistently safeguard a giant circle in the water? If a threat did suddenly emerge, how would security forces prosecute the threat in time to protect a flying boat airliner? Or, suppose an errant disabled boat strayed into the protected area: What would be the protocols for firing on it if it did not (or could not) respond to warnings? Maintaining a maritime exclusion zone broad enough to facilitate colossal flying boat takeoffs and landings will be a logistical nightmare.

The flying boat concept aims to move noise and congestion away from population centers, but moving aircraft activity too far away to coastal destinations would add time to reaching a traveler’s final destination. Also, the flying boats could only serve a limited number of city pairs with an equally limited number of connecting flight options. This would allow only a very few potential airline customers to consider including the aircraft in their fleets, a questionable business strategy at best.

Using the Airbus A380 as a benchmark, an aircraft capable of carrying 2,000 passengers is very unlikely to be commercially viable. Airbus has struggled to find buyers for the A380 superjumbo widebody, with the last sale over two years ago. United Airlines recently declined the type altogether and Malaysia Airlines is offloading its entire fleet of six aircraft, causing some speculation that the world’s largest airliner may need an infusion of new technology (such as improved engines) in order to remain competitive.

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Airbus admitted earlier this year that it would never recoup the $25 billion invested in the A380 project, although they no longer lose money on every delivery. This grim outlook is for an airplane that uses existing infrastructure and airline planning tools while relying on the same hub-and-spoke architecture on which the flying boat will also depend. The Airbus A380 does not have the added complexity and cost of being a flying boat, much less all of the corrosion issues that come along with it.

Hughes H-4 Hercules flying boat.

This proposal isn’t the first massive aircraft with eight engines designed to transport people and cargo en masse across the Atlantic Ocean. On November 2nd, 1947, the Hughes H-4 Hercules (more commonly known as the “Spruce Goose”) briefly achieved first (and only) flight off the coast of Los Angeles, California. Howard Hughes’ monstrous flying boat was never put into service with the military as intended because the mission it was designed for (ferrying very large amounts of people and cargo across the ocean) dissolved after the conclusion of World War II.

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Flying boats fell out of favor long ago, and for good reason. Long runways were constructed all over the world during World War II to facilitate long-range bomber and cargo flights, negating the advantage of a flying boat not needing a runway. But maintenance costs of flying boats also gave traditional aircraft a significant competitive advantage. Saltwater corrosion wreaks havoc on systems and “can cause eventual structural failure,” according to the FAA. Maintenance expenses for a flying boat carrying up to 2,000 passengers at a time would be stratospheric.

Loading and unloading an aircraft as large as the Airbus A380 is no small task, with new terminals being constructed or planned for construction in Dubai, Chicago and many other cities just to accommodate the superjumbo. As a result of the high position of the wing, the designers state that their flying boat concept could allow “emergency exits to be placed not only along the leading edge but also along the side of the aircraft,” although there is no mention of cabin door placement for loading and unloading passengers and their luggage. With the flying boat pitching and rolling in the water independently of a terminal structure, loading and unloading up to 2,000 passengers would be a very lengthy process.

In the event of an emergency, the FAA requires that all passengers and crew be unloaded in under 90 seconds. In a ground test, Airbus was able to successfully de-plane 853 passengers and 20 crew in 78 seconds. When US Airways Flight 1549 made a historic water landing on the Hudson River in 2009, 15 seconds elapsed from the time of impact to the first emergency exit door opening, allowing the first of 155 passengers and crew to evacuate.

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Even under ideal conditions such as a staged test, evacuating 2,000 people in under 90 seconds while floating on uncertain seas, no matter how many emergency exits are available and how strategically they are located, is highly unlikely and probably impossible. In an actual crash scenario, the added element of chaos (perhaps the reason why it took 15 seconds for the first passenger to escape Flight 1549) could make blended wing body airliners markedly less safe than traditional aircraft.

US Airways Flight 1549 floating in the Hudson River with emergency exit slides deployed.

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The BWB-450 airliner concept mentioned previously did account for emergency egress on paper. The cabin design called for six longitudinal aisles with main cabin doors at the front and emergency exits at the back of each. Four aisles spanning across the aircraft would also assist in de-planing, with a horseshoe-shaped aisle along the leading edge. However, the study also acknowledged that regulatory bodies would need to develop new evacuation criteria for the blended wing body airliner’s new class of interior configuration. If that criteria mandated all passengers and crew be able to evacuate the aircraft in more than 90 seconds, would passengers be willing to travel on something that was more difficult to escape than a traditional airliner? Would airlines accept this risk?

Environmental variables must be also taken into account when considering the flying boat proposal. What would be the impact of an enormous flying boat landing near a coastline on fragile marine ecosystems? Would these flying boats further exacerbate ocean acidification and the overall declining health of the oceans? What impact would saltwater have on their engines and structure? We simply don’t have enough information at this point to assess these considerations, but surely these questions (among many others) will need to be answered before the concept could ever be commercialized.

The flying boat designers state that their proposal could be powered by hydrogen fuel, which produces no emissions and would therefore lessen the aircraft’s environmental impact. However, the production of hydrogen fuel requires more energy to manufacture than can be extracted from the fuel when it is consumed. While the aircraft itself may not be a polluter, the supply chain feeding it most certainly is.

Further, the cost of producing hydrogen fuel is undefined in the proposal and could easily exceed that of traditional aviation fuel. Fuel is the largest variable cost to airlines, and a cost-effective hydrogen fuel supply would need to be absolutely guaranteed. Future aircraft may forego traditional and hydrogen fuels altogether in lieu of electric power from batteries, a technology that Airbus is investing in heavily.

A Big Flying Wing Seaplane Just Doesn’t Fly

Even if the flying boat concept were a land-based blended wing body, the design would buck all industry trends. Current state of the art airliners such as the Boeing 787, Boeing 777X and Airbus A350 (with a combined backlog of well over 1,800 orders as of this writing) represent the chosen path for a tumultuous industry that can’t afford such a radical departure from systems proven over the last 100 years of flight. These aircraft are designed to conform to existing infrastructure because the case for creating all-new infrastructure for one new aircraft type is insolvent.

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The oversized 777X has a folding wing mechanism that raises the last 11 feet of each wing so the aircraft will fit in gates designed for the original 777. The gargantuan Airbus A380 is so large that it requires an Airport Operations escort to shadow the wingtips during ground movements on the airfield at LAX. Airlines are willing to bet on innovative engineering solutions like folding wings on the 777X and escort protocols for the A380 because they preserve legacy infrastructure investments. The costs of designing, testing and building all new floating infrastructure to support an all new flying boat are far too burdensome when less disruptive solutions exist.

How much would a transonic flying boat seating 2,000 people and powered by eight engines cost? This year, an Airbus A380-800 costs $549.8 million. An aircraft with twice as many engines and able to carry more than twice as many people, all while operating in a maritime environment, could easily cost well over $1 billion per copy while being unable to serve inland destinations. Airlines cannot afford decreased capability and flexibility.

Ultimately, the success of the flying boat concept depends on a hub-and-spoke model. The authors note that 16 of the 32 largest airline hubs are located in a coastal area, with an additional eight situated within 50 miles of a coast. The hub-and-spoke model was also the major assumption of the Airbus A380 program, which has been nothing short of a sales disappointment. Travelers prefer the most direct route to a destination, a fact that is unlikely to change.

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Even with transonic speed capability, the flying boat would not travel fast enough to decrease the total time of a transatlantic voyage compared to land-based airliners. The time it would take for up to 2,000 passengers to travel to a floating airport, load onto the flying boat, fly across the ocean, unload at the next floating airport and then transfer to another (if not multiple) form(s) of transportation before reaching their final destination is not competitive.

It is possible that aircraft derived from Boeing’s BWB-450 and X-48 blended wing body designs or Northrop Grumman’s flying wing airliner concept could enter commercial service someday. As studies suggest, they could be quieter and more fuel efficient than traditional airliners, which would satisfy long-term goals from NASA, the FAA and others. However, new evacuation criteria would need to be established and integration issues with existing infrastructure would need to be resolved. Even then, these aircraft will not be taking off and landing on water.

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Like so many pie in the sky aviation concepts that have filled the pages of Popular Mechanics over the years, the reality always comes down to commercial viability, technical and political feasibility and non-glamorous metrics like emergency exiting times.

Although a super-sized flying wing seaplane sounds and looks cool, it just doesn’t float or fly when faced with the realities of modern commercial aviation.

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Photo credits: Concept image - Imperial College of London, Concept schematic - Imperial College of London, YB-49 in flight - Public Domain/Wikicommons, X-48B runway - Carla Thomas/Wikicommons, X-48B underwing - Carla Thomas/Wikicommons, Airbus A380 landing - LeGeôlier/Wikicommons, Hughes H-4 Hercules - Public Domain/Wikicommons, Airbus A380 terminal - Philippe Durand/Wikicommons, Flight 1459 in Hudson River - Gregory Lam/Wikicommons