Hydrogen-Powered HY4 Rolled Out


A consortium of European companies and organizations rolled out a hydrogen-powered research aircraft Friday that they hope will provide the technical bedrock for commercial transport aircraft carrying up to 40 passengers. The airplane is called the HY4 and was displayed briefly at a hangar at the Stuttgart Airport.

Although few details were offered in the German-only press materials, the HY4 appears to be based on Pipistrel Aircraft’s innovative Taurus G4 which married two of the company’s electric gliders into a twin-boom planform with a single electric motor in the center section wing. The G4 won the $1.35 million NASA Green Flight Challenge award in 2011. Pipistrel, which leads the world in the production of electric aircraft, is part of the HY4 consortium.

Project leader Josef Kallo called the HY4 a sixth-generation hydrogen drive that uses a fuel cell to drive a single 160-HP electric motor for a top speed of 108 knots. Claimed range is up to 900 miles, according to technical specs provided by the HY4 group.

Test flights began last month and more than 30 takeoffs and flights of up to two hours have been completed. The HY4 has been approved for Europe-wide flight and will remain in Stuttgart through May for further testing. Other participants in the program include the German DLR, the Europe-wide Modular Approach to Hybrid Electric Propulsion Architecture (MAHEPA), Diehl Aerospace, Cummins and Uni Ulm. Find more information the HY4 website.

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  1. In general I am against electric vehicles but I think hydrogen has better future potential than batteries, especially for aviation, trains, trucking, shipping, and probably cars as well.

    Spare the Hindenburg jokes, safety technology has come a long way since the 1930’s.

    Only hydrogen can promise a half decent power to weight ratio, and the endurance that airplanes and long haul vehicles need.

    Battery weight is obviously prohibitive.

    H2 infrastructure needs to be built, but if Big Government succeeds if pushing us off inexpensive and plentiful fossil fuels, fuel cells are our best bet.

    Also, the design of this thing is pretty cool, like an inverse P-38. Not related to propulsion, but I like the thinking.

    • The question is “why”. This is old technology and it also requires more energy to make the fuel than you get from using it.

  2. I’ve been driving a FCEV for 4.5 years. There are 8,000 of them in the road in California and there has never been a fire in any of them. One was burned in the wolsey fire in 2018 and the vehicles glass was completely melted and the paint burned off but the hydrogen tank was intact (it had vented the hydrogen through the PRV).

  3. Ingenious design using familiar aircraft and their respective components married together for test and evaluation. Those sponsor decals reveal a lot about who will benefit from this new marriage of existing technology. Sort of a new recipe using proven ingredients.

    Cummins is not going to get into aviation propulsion, at least not right now or the near future. But what is being learned will translate well for heavy, OTR trucks, and the heavy pick up industry. And those two industries produce vehicles that we regularly buy as consumers and depend on for our day to day living needs. Ford figured out there is a significant performance increase including fuel economy when you shed 700 pounds off the pickup body by using aluminum rather than steel. Now add the potential benefits of hybrid technology. The benefits of lightweight, high strength, long range with the safety requirements inherent to aircraft development, will be a huge advantage when it comes to trucks especially.

    I am glad that Pipistrel is taking this kind of interest and participating in the collaboration of these ideas through aviation. That takes vision and courage in addition to big bucks investment. As aviators, we get to see development within our collective passion with big benefits down the road ( no pun intended) for improvements in delivery of what we use in daily life.

    Great video. Imaginative aircraft design. Kudos to all the participants and sponsors!

  4. Electric airplanes are great. It’s just that damned extension cord that is such a pain! 😉

    Seriously, electric aircraft design today is kind of where the Wright Flyers were compared to modern internal combustion engine technology. This aircraft appears to be a good technology demonstrator with an intriguing design, but it’s practical application for even basic flight is quite limited. I can’t really see it working as a trainer, with the student in one cockpit and the instructor seven feet away in the other.

    Ironically, the issue with electrically powered airplanes is not with the propulsion systems, but with the fuel storage and delivery systems. With a full electric airplane the main motor, motor controls and energy management systems are already designed to a high level. But, the fuel storage is the problem. If you think of electrons as the fuel, batteries are the equivalent of the fuel tank, and we are all familiar with those shortcomings. With a fuel cell, the fuel becomes the hydrogen that feeds the cell to generate the electrons. Again, fuel cell technology is pretty well developed, but fuel storage is once more the issue. Ignoring the infrastructure issue for hydrogen generation, the on-board storage is a major problem. Hydrogen gas can be stored in one of three ways: high pressure vapor tanks, storing the H2 adsorbed in a metal hydride matrix, or storing it as a cryogenic liquid. High pressure tanks may work fine in land vehicles, but use in aircraft could be difficult, due to their size, weight and the high internal pressure (approx. 3,000 psi). Hydride storage overcomes the high pressure issue, but their capacity is lower than pure storage. That leaves cryogenic storage. Since liquid H2 is about 600 times more dense than the gas, or maybe 300 times more than high pressure cylinders, it can store the volume of fuel for good flying range within a reasonably sized tank. However, that means building an airport infrastructure capable of handling a liquid at -423 degrees F, and constructing highly insulated tanks on the aircraft. One major problem with cryogenic storage is that you cannot fill your plane’s cryo tank and then park it in a hangar for days or weeks as you can with Avgas. Even in the insulated tanks, the liquid will constantly offgas. Come back two weeks later and the tank may be almost empty. Fortunately, the safety issue with hydrogen is a non issue compared with Avgas or Jet A. Spill Avgas or Jet A on the ground and light it off, and it will burn with a highly luminous flame until it is all burned up. Spill liquid H2 on the ground and it will instantly begin vaporizing into a gas that, being much lighter than air, will quickly dissipate. And, even if the H2 burns, the flame has a low radiant heat component, which means that your are less likely to be burned. Most people do not realize that many passengers in the Hindenburg disaster survived in spite of being exposed to the huge fire. Yeah, it is still dangerous, but no more so than conventional fuels. As Rennie A says, fuel cell powered cars have an excellent safety record.

    I would much prefer an electric motor in my plane rather than the Avgas burning engine I now have. Unfortunately, we have a whole lot of issues to overcome before that day arrives. Sorry to be so long-winded.