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DLR developing four-passenger fuel cell aircraft

The German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) is developing a four-passenger aircraft powered solely by a hydrogen fuel cell battery system. DLR presented the HY4 project at the International Trade Fair World of Energy Solutions this week in Stuttgart.

HY4 uses a hybrid system: the main power source is a low-temperature Proton Exchange Membrane (PEM) fuel cell, which continuously supplies the electric motor with durable and reliable power. A high-performance lithium battery covers peak power loads during take-off and when climbing.

The HY4’s electric motor has an output of 80 kW and allows for a maximum speed of approximately 200 km/h (124 mph) and a cruising speed of 145 kmh/h (90 mph). Depending on velocity, altitude and load, a range of between 750 and 1500 kilometers (466 to 932 miles) is possible.

The most striking feature of the HY4 is its two fuselages, which are firmly connected to each other by the wing. This twin fuselage design allows an optimal distribution of the drive components and a higher total loading capacity. Each one can seat two occupants. The maximum weight of the HY4 is 1500 kilograms (3,300 lbs). Click to enlarge.

The first flight of the HY4 is planned for the summer of 2016 at Stuttgart Airport. The development of the drive system is based on DLR’s extensive aviation and energy research activities in the areas of batteries, fuel cells and hydrogen technology.

Regional transport as an entry scenario. The DLR researchers see application possibilities in European regional traffic. Electric drives are well suited for shorter distances due to their low noise and emission levels, as well as their capability to take off and land on short runways thanks to their high torque. With more than 60 regional and international airports, Germany has a well-developed, extensively distributed network and already possesses the appropriate infrastructure for the implementation of this approach.

Our goal is to use aircraft such as the HY4 as an Electric Air Taxi to connect destinations more flexibly and offer faster alternatives to existing routes and means of transport.

—Josef Kallo

Under the auspices of the DLR Institute of Engineering Thermodynamics, which is responsible for the overall integration of the power train, the following partners have joined forces to achieve the world's first fuel cell passenger aircraft: the fuel cell manufacturer Hydrogenics; the aircraft manufacturer Pipistrel; the University of Ulm as a scientific partner; and Stuttgart Airport as the home airport for the HY4. The DLR spin-off H2FLY will operate the HY4 and will be responsible for the certification process.



My comment has been eaten.
I was saying this is a really practical range, and I did not expect something like this to happen so soon.

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This unlike ground vehicles might be a useful application for hydrogen fuel cells. A liquid hydrogen tank is low weight which is important for range in an airplane. Agree that cruising speed of 145 kmh/h (90 mph) and a range of between 750 and 1500 kilometres seems practical. Make the plane autonomous so that it can take 4 passengers with a little luggage. Then have a taxi service with numerous of flights every minute between mayor cities. Might work for pollution free aviation transport.


I applaud the R&D effort, but am very skeptical about the range claims.

> A liquid hydrogen tank is low weight.

Actually, no. Hydrogen storage systems are very heavy and volumetrically, very difficult to make work on an airplane.

90 mph is very slow for an airplane, revealing the limitations of the energy density of the system.


Reform methanol.

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A cryogenic tank does not need to be heavy and the fuel is definitely not heavy. A compressed hydrogen tank is more heavy. I can't see what they use but I think it is cryogenic.

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The slow speed is because the fuel cell is heavy so they have to make it small so little power low speed. Same problem with cars. A 500kw fuel cell would be a ton of stuff. So they do 80k watt and get a boring car. This is a first try on such an airplane. It will get better. Maybe make it bigger with 16 passengers and it could get better specks. But money developing the first thing is always an issue.



Lets see your numbers to back up your claims.

Perhaps you are confused, as you were when you confounded figures for the cost of running electric vehicles without equalising taxation.

Perhaps you would be more productively employed trying to move your website to some minimal standards of journalistic integrity, such as you and your writers declaring what financial interest you have in the shares of the companies you so uncritically boost, such as Tesla, rather than relentlessly trolling other more impartial sites.

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SJC reforming methanol will not work. The reformer is heavy and making hydrogen by reforming hydrocarbons in a small scale setting leaves a ton of impurities in the reformed hydrogen that will drastically shorten the life of the fuel cell. It will not work in cars as well for the same reasons.
We know hydrogen is an excellent rocket fuel but a lousy vehicle fuel. However, we might get it to work as an aviation fuel. It is worth trying I think. Batteries may one day also be used for short-distance aviation but the gravimetric energy density needs to improve a lot. I would say over 400wh/kg in a stable durable and safe battery (for aviation they need to be more reliable than cars where you can stop and get out and away if something bad happens). We are probably 10 or 20 years away from such a battery.


The reformer is light and small, they have been made and used for decades. It has been done for more than a decade by Daimler in the NECAR program and even drove across the U.S.


"The HY4’s electric motor has an output of 80 kW"
Where are you getting 500 kW, so it is too heavy?


Davemart as usual, full of personal attacks, but absolutely nothing of substance about the topic at hand.


It is way too clever clever.
It is too slow and the passengers can't talk to each other.
It also seems to have a very high wingspan, this making it large + it looks expensive to build.
Why not just build a hybrid aircraft and use the batteries when you are on the ground (for air and noise pollution) and a diesel engine for sustaining power.
Then, you could have a conventional aircraft with one cabin and decent speed and range and low local pollution.


You make some good points, Mahonj. Electric nosewheels are a recent innovation that appear to have commercial potential. The extra weight is justified by taxiway fuel
savings. There are some experimental propulsion hybrids, but extra mass that does not perform throughout the flight regime is inefficient.

The DLR HY4 has two fuselages, dual empennage, and one additional motor nacelle. There is no way around the fact that this increases the parasitic drag and construction cost vs a more conventional arrangement, which is one of the reasons why it is seen so infrequently in aircraft design.

There are some notable aircraft from Bert Rutan that have used a similar configuration, but in the evolutionary tree of aircraft design, it is not a branch with many progeny.

No doubt DLR chose this design because it provides extra volume for fuel
storage, but the performance specs speak directly to the viability of the concept.

If there were massive fuel cost savings, the low performance might be justified, but H2 fuel stations costing $2.5 - $4 million each, that is very unlikely to be the case. Except for training only use cases, or well-defined milk runs, lack of infrastructure will cripple H2 as an aviation fuel.

Regarding H2 fuel cost, here is a number for you Davemart. I was at Harris Ranch yesterday, where First Element has recently installed a hydrogen fueling station. Retail cost of H2 is $16.49 per kg.

Directly across the street, I refueled 200 miles additional range from the Supercharger for $0 (the fee had previouls been included in the purchase price of my car)

There is, by the way, also a Tesla battery swap station at that site. If you want that really fast refuel event, you can get it. It doesn't appear to get much use. Apparently after three hours of driving, most people would prefer to walk over to the fine dining restaurant and for about half the price of a swap, eat a premium steak dinner while the hoss feeds at the Supercharger trough.

Over the 15 year lifespan of an FCV (the 10,000 PSI fuel tanks are life-limited) a once per week 4 kg fueling stop at Harris Ranch ( ~12,000 miles per year) would cost $51,480. The first three years will be paid by Toyota or Hyundai, discount $10,296.

$41,184 H2 vs $0 Supercharger. There are some numbers for you Davemart.


btw, Davemart, I have posted this here on GCC many times before in response to your totally unfounded and irresponsible accusations: I have $0 (zero) financial interest in Tesla or any other automotive company. I don't have any investments of any kind in any transportation company, or any company I write about.

Bring it up as often as you'd like. I'll just keep copying and pasting this rebuttal and start incrementing the counter, and posting it, as often as you make your scurrilous accusations.

This is the fourth time.

It is too slow and the passengers can't talk to each other.

It looks like conjoined twin sailplanes, right down to the T-tails.  That is probably what it is, saving the cost of designing a new fuselage.  Only the wing center section needs to be new.

It also seems to have a very high wingspan, this making it large + it looks expensive to build.

You need the long wingspan to get the L/D required to fly 4 passengers on just 80 kW.


DaimlerChrysler's NECAR 5 Arrives at U.S. Capitol to Complete First Ever Fuel-Cell Powered Cross Country Trip

Ballard® fuel cell drive system -- including the methanol reformer



I'm always interested to see a good link, so thanks for posting SJC. I do have to ask though, without intending to be snarky in any way, what is the relevance of a link to a 13 year old story? ("DaimlerChrysler" was my first clue).

If no one has followed up and made a commercial vehicle in 13 years, how is that an indication that this technology is viable now?

Wiki> One of the potential drawbacks of using high concentrations of methanol (and other alcohols, such as ethanol) in fuel is the corrosivity to some metals of methanol, particularly to aluminium.

So don't spill it on the airplane wing while fueling. (the stuff on the wing surface would not be the problem. The stuff that seeps into the cracks and crevices from a spill would be the problem).

Toxicity does seem to be a problem, because it's possible to inhale fumes or absorb enough through the skin to cause blindness or death:


Roger Pham

The way to make Compressed H2-FC work in a personal plane is to make the H2 long cylindrical tanks part of the structure of the airplane, like the long wing spars and tail boom.

The wing can be on top of the fuselage, with two main spars made of carbon fiber H2 tanks supported by Nomex ribs and skin. The tail empennage can be supported by a central cylindrical tail boom that runs the entire length of the fuselage, that also doubles as H2 tank.
In this way, the wings and tail are super strong, while little weight penalty for having the H2 tanks. H2 fuel is super light. It takes only about 20-25 kg of H2 to fulfill a 1,000 nm range. By contrast, a ICE powered small plane needs about 550 lbs (250 kg) of Avgas to go the same distance.

Furthermore, with motor having up to 5 kW per kg and FC 3kW per kg, significant weight can be saved over ICE with under 1 kW per kg power to weight ratio.

Two motors, one on each wing, would make better aerodynamic and improve front visibility, while allowing luggage to be place in front of the aircraft, thus preventing dangerous tail-heavy situation when fully loaded.
In front-engine small aircraft, the luggage is loaded at the rear of the cabin, which can lead to dangerous tail-heavy situation that has claimed many lives.

Wing-mounted propellers or ducted fans propelled by e-motors have advantage of improve short take-off and landing ability, when the air can be blown over the wing with flaps down, significantly increasing lift.


It may seem possible to fit high pressure H2 tanks in the tail boom, but only until you actually do some weight & balance calculations. Then it becomes clear that it's a total nonstarter.

Even if you were to temporarily suspend rational thought and imagine it possible to make the tail boom into, or contain, a leakproof 10,000 psi pressure vessel (which weighs over 100 lbs to contain 5 kg of fuel) there is a really good reason no real aircraft stores fuel in the tail boom. Depleting the fuel over the course of the flight would unbalance the aircraft.

I admire your enthusiasm Roger, but kindly suggest you spend less time reading fantasy fiction, and more time reading science and engineering textbooks.

It's just not helpful (to you, or anyone else) to repeatedly demonstrate that you haven't the slightest idea how the things you are suggesting would really work.

Roger Pham

Not just the tail boom, but one long cylindrical H2 tank running from the nose to the tail of the aircraft, plus a shorter tank running from the nose to perhaps 1/2 way to the tail end. The weight of the H2 is so little that the change in Center of Gravity is minimum.

When the luggage is in the nose section, the aircraft will be balanced even when fully loaded, unlike current aircraft that have luggage compartment
You see, with two motors on the wings, the nose of the aircraft is free to contain those long and thin longitudinal tanks that also serve as structural members.

The pressure may be 5,000 psi instead of 10,000 psi if there is enough volumes from the wing tanks and fuselage tank.

Please be patient, ECI, and try to learn as much about Hydrogen-FC tech as you can. I'm here to facilitate this, since there are so much misconceptions in the public about H2-FC technologies.


Stacks and reformers have improved since 2002. Daimler ran reformed methanol for more than a decade successfully. This has been done, it is proven technology.


By the way, you can reform jet fuel as well. It has a higher BTU per gallon and is available at most airports.


Roger, i think you live in a lala land of your own creation. Instead of trying to "educate" people on a topic which you clearly do not understand yourself, why not spend your time getting a real education first, so that you have some credibility, and real value?

Have you ever even seen a hydrogen tank up close? Have you ever seen a cutaway of a hydrogen tank? What is the thickness of a typical 10,000 PSI hydrogen tank? (or for that matter even a 5,000 PSI hydrogen tank). None of this matters if you live in a fantasy land where reality is anything that springs from your keyboard.

But in the real world, it matters quite a bit.


SJC, I agree that much progress has been made on stacks and reformers in the past 13 years. But if the only answer to why we do not see any commercial solutions today is "the oil industry has prevented it" as you have mentioned in the past, it seems to beg another question: why then have BEVs been successfully brought to market?

I'm not opposed to FCs, especially if their fuel source is practical, economical, and can be low or zero carbon.

But I'm really curious to know how promoting them here advances anything if no manufacturer is actually building them.

What is the additional cost of on-board reforming? How durable is the system? Subject to contamination?


I never said the oil industry has prevented reforming.

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