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Clip-Air project envisages modular aircraft you can board at a railway station


June 11, 2013

The Clip-Air combines air and rail transport elements

The Clip-Air combines air and rail transport elements

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Air travel today is a nightmare of long drives to crowded airports, long queues that move at a snail's pace, and long, boring waits in identical lobbies drinking overpriced coffee. It would be so much easier and less frustrating if catching a plane were like catching a train. If Switzerland’s École Polytechnique Fédérale de Lausanne (EPFL) has its way, its Clip-Air project will one day produce modular aircraft that will allow you to board a plane at a London railway station and disembark in the middle of Rome without ever setting foot in an air terminal.

Under development since 2009, the Clip-Air project aims to merge the speed of air travel with the flexibility of rail transport. Airplanes are specialized vehicles made for particular tasks, so a passenger plane can’t be used as a cargo plane without extensive modification. On the other hand, a train is a collection of modules with a locomotive “module” providing propulsion. Put passenger cars behind a locomotive and you have a passenger train, put goods wagons there and you have a goods train. You can also add specialist cars, such as buffet cars, sleepers, guards vans, tankers, ore carriers, car carriers and many more.

Clip-Air does the same thing with airplanes. Instead of a locomotive, it uses a flying wing containing the engines, cockpit, fuel and landing gear. And instead of cars, there are up to three modules or capsules that are self-contained airplane fuselages. The capsules can be mixed and matched to suit the purpose at hand. A plane can carry all cargo or all passengers, first class or coach capsules, or any combination along with specialized versions. Another benefit of Clip-Air is that the capsules also increase capacity for an aircraft of a given size, with three passenger capsules carrying 450 people, yet the plane can still operate from a conventional airport.

EPFL has designed the capsules so that they are 30 m (98 ft) long and weigh 30 tonnes (29.5 tons). The clever bit about this is that it makes the capsules suitable for rail transport, which provides the potential to alter the design of airports and how they’re used. Instead of going to the airport and boarding planes, passengers could go to railway stations and board capsules as easily as a commuter train, which on reaching the airport would be attached to the flying wing, so passengers never need to go inside a terminal. The same principle applies to industry, with freight loading moved to railway yards or factories.

EPFL claims that this configuration allows for more efficient and flexible fleet management and reduces the likelihood of empty flights. The modular design also provides savings in maintenance, storage and management. In addition, EPFL claims that the design is greener because the Clip-Air can carry as many passengers as three Airbus A320s with only half the engines. It can also be adapted to run on a variety of biofuels or liquid hydrogen thanks to the ability to swap out a regular capsule for the large tanks that hydrogen requires.

Though EPFL is confident about the future of Clip-Air, it admits that the technology has a long way to go before it’s practical.

"We still have to break down several barriers but we do believe that it is worth to work in such a concept, at odds with current aircraft technology and which can have a huge impact on society," says Claudio Leonardi, leader of the Clip-Air project. “The development of the concept requires performing more advanced aerodynamic simulations and testing a six-meters (20 ft) long flying model powered by mini-reactors in order to continue to explore the concept’s flight performance and to demonstrate its overall feasibility.”

A 1.2-m (3.9-ft) model of the Clip-Air plane will be exhibited from June 17 to 19 at the Normandy Aerospace stand at the Paris Air Show. Gizmag will be attending the show and will take a closer look at the concept.

The video below shows an animation of the proposed Clip-Air plane.

Source: EPFL

About the Author
David Szondy David Szondy is a freelance writer based in Monroe, Washington. An award-winning playwright, he has contributed to Charged and iQ magazine and is the author of the website Tales of Future Past. All articles by David Szondy

Powered by mini-reactors?? What do you mean "mini-reactors"?


If they can make this concept work then it is a brilliant idea. Not sure if it would be all that practical for long haul flights (which need more facilities eg catering, etc) but for short haul, eg trans Europe, this might well work, and could take advantage of quieter regional airports (provided they have or can be adapted to be rail served).

I would hope that it wouldn't be used for flying to cities that already have superb high speed rail links, eg London-Paris, London-Brussels, but for longer 'short haul' (if that makes sense) such as, for instance, London-Marbella, where high speed rail is less practical due to distance, and the need to change trains.


I don't see why this couldn't work on the aeronautical side. On the railway side, a lot of prejudice and established practice stands in the way of getting a flight-weight article permitted to operate on rails. At the very least, there will have to be detachable bogies to keep the modules light enough to fly efficiently.


Personally I'd be a little worried about travelling at 30,000ft in a pressurized fuselage that had been exposed to a railway environment, rather than the relative safety and caution of an airport.

I'd also be skeptical that those three little engines could move such a huge beast, given the enormous drag penalty of suspending three separate fuselages under a lifting body wing.


That might work in Europe, but here in "the land of the free" the TSA is going to insist on those long lines and other security theater measures.


I agree with piolenc, I think having it sit on a 'train dolley' would make it lighter since that part would not be lifted when it is hoisted up to the plane. It would make it lighter in weight. In comparison, it is like the containers that they put on specialized rail cars that can have them without having to add the wheels to the container itself.

I think this has a lot of potential. I think it could be a flying hotel for those traveling long distances. It could be the airplane version of 'shipping containers'.

I really like the blended wing design.

I think it could bring more people to train stations even if they are not really riding trains.


I can't see how the the join between the undercarriage and the wings can be made string enough in this configuration. Also, how can you ensure that the wight of the two under-wing modules are the same weight given potentially different cargoes?

You would also need to know the weight of every module before fueling the aircraft.

Walt Barker

In my country they have torn up most railways. Railway tie boneyards all over Saskatchewan :(

Lake House

Airplanes crumple and fall apart under the conditions railroad vehicles normally operate under. So the cargo/passenger compartments will have to be overweight.

If the airline wishes to be able to rapidly convert between passenger and cargo they can buy airliners in a convertible configuration. Configured for cargo they are a little heavy but not as bad as a rail capable fuselage.

The most efficient way to move passengers and mixed cargo is with a hub and spoke flight schedule, which is why you usually have to change planes one or twice on your journey. Overnight delivery services such, as FedEx could not afford to operate without it.

Do you want to get into an airline seat and then go to the airport wait until they load you on the plane then fly to your destination city and then wait to be put on a train then be transported to a train station before you can get up and stretch you legs without a real good excuse? I certainly don’t. Too many people die from sitting in airliner seats already.

It is a stupid idea that has failed before but there is always somebody who thinks "But if I was the one doing it, this time it will work."


This idea makes less sense than its developers claim. The problem with rail plus air travel or indeed anything plus air travel are the delays as we wait for the plane, crew, and enough passengers to arrive. This doesn't solve that problem. Those in the first passenger module to arrive, for instance, will still have to wait for modules 2 and 3 to arrive and get attached. They'll still have to wait when weather delays the plane.

What it does mean is that those who're crammed into these modules will have to spend a long time in that same cramped and unchanging environment. That they won't like.

Remember, people get very upset over a 30 minute delay on the tarmac. They're going to feel much angrier if that's joined, in the same limited space, to a 2-hour train travel and airport sorting wait, plus a half hour waiting for the plane, plus another half hour waiting for the other modules to arrive and get attached. Add that up, and it's three hours in that module before the plane even takes off. And keep in mind the added hassle of boarding passengers who came directly to the airport. With three modules, two on opposite sides of the plane, boarding won't be easy.

Yes, it's no fun waiting in an airport, where travelers can get up, stretch, go to a less cramped restroom, and even dine at a meal that's likely to be more varied and less inflated in price than that on the plane. But that's still better than being stuck in a train plus plane module the entire time, forced to use its limited services.

The aviation industry needs to do more to deal with all the frustrations and delays of air travel, but this approach is hardly the answer. At best, it might suggest a minor but helpful improvement--the ability to check your luggage through to your air destination from major rail stations. That'd mean less hassle and fewer waits in line.

Years ago, I remember taking a train from Copenhagen to Stockholm. Those who ran the train must have thought themselves clever by having my train load onto the ferry for the trip. Personally, I was disappointed. I'd have rather have exited the train with my luggage, ridden the ferry, and boarded another train, with all the movement and change that entailed. Spending that entire trip in one module/train car was a bore.

Michael Perry

It looks like it could do to what has already happened with shipping in containers, general cargo very feasible simple cylindrical containers.

But human transportation involves far more complex issues, security, sustenance, handling logistics, etc...

Bob Flint

Nothing special about the engines. Any other aircraft could do the same, if desired. Think it would have high drag, high fuel, unless slower. Doubt it would be a paying proposition. For a different take that uses standard shipping containers for fright, see When presented to AIAA no reason was put forward that it would not fly and be profitable.

Stephen Funck

Oops, sorry folks! I pulled the wrong lever. Oh well. Fly the friendly skies.

Doug Nutter

The drag would be intense - the wing, flight surfaces plus three fueslages? Obviously this was not designer by anyone with aeronautical understanding. As a concept, it's good. It might be used to suck a few million development dollars out of some stupid government so the designed can live his lifestyle by producing nothing. It isn't going to work! The design is so flawed it is useless. Weight and balance would be impossible to maintain between the envelope of the actual flight vehicle. I can see so many reasons why this pig won't ever fly - but some government might pony up dollars for it. Obama seems happy to throw a Billion at Solyndra, so maybe he'll put up tax money for this pig?



I work at a foundry that supplies undercarriage parts for freight railcars, and we make castings that go into some pretty heavy-duty cars. Gunderson makes a flat car that can handle 226,000 pounds which is 10% more than a fully-loaded A320. Take away everything except the fuselage, passengers, luggage, and climate control, and even a standard freight car should have plenty of capacity to hold one of these.

Justin Chamberlin

As usual, the devil will be in the fine detail as more design work is done. I would think all luggage checks, main restroom visits, dining etc. would be done at the rail station, leaving only the express train transport and 'hooking up' to the plane to be done quickly. Only big city stations could be used, stopping for a few passengers here and there along the way would be uneconomic.

The Skud

I can see several problems with the system. Let us say that you can make it work. How do you maintain schedule of these trains unless there was a final procedure of immigration and security check left for just before attaching the module to the airframe? If these procedures were to be completed at the time of boarding the time delay with varying passenger load would be absolutely unpredictable.

The biggest problem facing passengers is commuting to the airport. Europeans seem to have solved this to a very major degree and the US authorities simply refuse to learn the lesson of providing decent public transportation.

I remember going to the US to visit my daughter a few years ago. I had to go to Newark from Mumbai. I flew via Amsterdam. I took a 4 day break in Europe to see my sister in Antwerp. I caught a train right at the Amsterdam airport, underground. This took me straight into Antwerp Central. No hassles or delays anywhere.

By comparison for someone living on the south side of Chicago it would be a nightmare just reaching O'Hare.



Apply the concept to a ferry, so a 2-3 car rail vehicle can cross a river where the volume of people/location does not make it feasible to have a tunnel or airport.

Apply the above concept to a bus system, so a bus can drive on to a ferry platform, lock the wheels, and the bus driver can steer over the water to the other side.

If you insist on flying, why not an air ship. I love those things. Tethered Hindenburg like thing capable of lifting a few ore cars. Not fast, but a better payload than a plane.

Best of all for the above, with a few structural reinforcements, there may not be a need for complete re-engineering.


I see a very slick and fast way to insert a unit of soldiers, or supplies and equipment into an area quickly, even an assault. Imagine an air drop in force in armored containers instant fortifications.

John Sweet

Love this, now make plane VSTOL for pickup or take train cars to airport for PU via runway LAPES style,

Stephen Russell

Why not just fit out a sea container with seats and stuff, then just shove it in an AN-124?


Decades ago, Gerry and Sylvia Anderson used this design in the movie "Journey to the Far Side of the Sun" (1969); the passenger container unloaded from the aircraft to a wheeled base that took it directly to the terminal.


This looks like a logistical nightmare at each end of the trip--with a large infrastructure needed to support it.


This design looks like someone ran across the Luftwaffe 1946 website and saw the designs Daimler-Benz drew up in 1945 (Project A, B, and C) for a carrier aircraft (with the same kind of spatted landing gear under the wings) that would transport a jet bomber slung under the fuselage close to its target (early jet engines having high fuel consumption, and therefore limited range; the carrier aircraft had turboprop engines) -- the ancestor of designs like Scaled Composites' WhiteKnightOne and SpaceShipOne -- and envisioned something similar using modern materials.


re; nutcase

Because it is heavy and thus increases fuel consumption and makes it less efficient for getting passengers to get on a plane to their destination.


This colossally complex solution to a less than relevant problem will seem a lot better once someone figures out how to build a warp drive. Airplanes that assemble like LEGOs should be left on a drawing pad until warp drives are cheap & easy to build. That requirement should keep this lunatic idea out of the way of High Speed Light Rail, better regional airplanes, and just plain regular trains. All of these work pretty well now, except in countries like the USA where major corporations rule in their personal best interest.


re; StWils

There are a few places in the USofA where rail and High Speed rail make sense for passenger service but for the most part the distances are too great.

Americans on the whole don't like mass transit including over half the people who ride it on a daily basis. The trolly systems didn't die because the automotive giants bought them up and dismantled them. The automotive giants were just stupid enough to buy a corpse that had not stopped twitching.

I remember that last time the local mass transit bus drivers went on strike. The traffic and air quality improved.


Even without the other 4.5 gazillion problems how, in the world, would they be able to balance those loads? I love the part about using hydrogen. They could carry three modules full of goods and people as long as they replace those modules with huge hydrogen tanks before takeoff. They should consider other green fuels- like fairy farts, for example. Will somebody please send me a list of the investors? I have a project about which I'd like to speak to them.

Brian Mansell

On top of all the problems already pointed out in the comments, I'll just add; the train cars will be less streamlined than current straight sided cars due to the curvature of the nose and slant of the rear, a container light enough to be carriable by an aircraft is never going to be safe enough for railroad operations (it'd be crushed far too easily in a wreck), and the G-forces the passengers would feel at that distance from the center of gravity when the aircraft makes any kind of roll manuever would make for an uncomfortable flight, flight crews would be unlikely to be able to move from unit to unit in flight meaning they'd be unable to back each other up so you'd have to have larger crews, the aircraft with additional compartments appears to be one of the worst examples of aerodynamics by someone without a clue I've seen illustrated.

Finally I'll add that as a person often stuck riding coach (work won't pay for anything nicer) I want to spend the least amount of time possible in that cabin. Being stuck in for an extra hour or two on the ride to the airport sounds miserable, I'd much rather get to walk from the subway station to the terminal.

Keith Lamb

Given that to do this you have to move check-in, baggage-handling and security to train stations why not just have dedicated trains to move people from regional stations directly to airside waiting. If airlines can handle passengers and luggage going to multiple destinations within a single plane then a joined up train and plane system could do the same thing using largely existing infrastructure, rolling stock and airplanes.

Alex Richards
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