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Boeing Prepares Fuel Cell Demonstrator Airplane for Flight Testing

Cutaway drawing of Boeing fuel cell demonstrator plane. Click to enlarge.

Boeing researchers and industry partners throughout Europe plan to conduct experimental flight tests this year of a manned airplane powered only by a 20 kW fuel cell and a lithium-ion battery pack.

The systems integration phase of the Fuel Cell Demonstrator Airplane research project, under way since 2003 at Boeing Research and Technology-Europe (BR&TE), was completed recently. (Earlier post.) Thorough systems integration testing is now under way in preparation for upcoming ground and flight testing.

The Boeing demonstrator uses a Proton Exchange Membrane (PEM) fuel cell/lithium-ion battery hybrid system to power an electric motor, which is coupled to a conventional propeller. The fuel cell provides all power for the cruise phase of flight. During takeoff and climb, the flight segment that requires the most power, the system draws on lightweight lithium-ion batteries.

Flight tests, which will take place in Spain, will demonstrate for the first time that a manned airplane can maintain a straight level flight with fuel cells as the only power source.

While Boeing does not envision that fuel cells will provide primary power for future commercial passenger airplanes, demonstrations like this help pave the way for potentially using this technology in small manned and unmanned air vehicles. It also gives us hands-on experience to complement other fuel-cell studies being carried out throughout the company.

—Francisco Escarti, BR&TE managing director

Boeing researchers see promise in other types of fuel cell technology as well as the PEM system. An example is a Solid Oxide Fuel Cell that could be applied to secondary power-generating systems, such as auxiliary power units. This technology could be mature enough in 10 to 15 years for potential use in commercial aviation.

BR&TE, part of the Boeing Phantom Works advanced R&D unit, which is chartered to provide innovative technology and system solutions to meet future aerospace needs, has worked closely with its colleagues in Boeing Commercial Airplanes, its Spanish partners, and with companies in Austria, France, Germany, the United Kingdom and the United States to design and assemble the experimental airplane.

The PEM fuel-cell system used on the flight demonstrator, for instance, was designed and built by the UK-based firm Intelligent Energy.

The demonstrator aircraft is a Dimona motor glider, built by Diamond Aircraft Industries of Austria, which also performed major structural modifications to the aircraft. With a wing span of 16.3 meters (53.5 feet), the airplane will be able to cruise at approximately 100 kilometers per hour (62 miles per hour) using fuel cell-provided power.

The Madrid-based avionics group Aerlyper performed airframe modifications, as well as the mounting and wiring of all components; SAFT France designed and assembled the auxiliary batteries and the backup battery; Air Liquide Spain performed the detailed design and assembly of the onboard fuel system and the refueling station; the Electronic Engineering Division of the Polytechnic University of Madrid (School of Industrial Engineering) collaborated in the design and construction of the power management and distribution box; post-integration bench testing is being conducted in a facility that belongs to the Polytechnic University of Madrid (INSIA); and SENASA (Spain) will provide a test pilot and facilities for flight tests.

Other suppliers for the Fuel Cell Demonstrator Airplane include UQM Technologies Inc. (United States), MT Propeller (Germany), Tecnicas Aeronauticas de Madrid (Spain), Ingenieria de Instrumentacion y Control (Spain), GORE (Germany), Indra (Spain) and Inventia (Spain).


Rafael Seidl

Liquid H2 has the highest gravimetric energy density of any fuel, so if hydrogen makes sense in any mobile application at all - which is debatable - it would be in an aircraft.

The use of a fuel cell and electric motor also sounds appealing in terms of efficiency. However, aircraft need a lot of power to get off the ground and make their ascent. PEM fuel cells are not yet good at high power and, using several in parallel would be even more expensive. A good compromise might be a parallel hybrid drive featuring a small ICE plus a beefy electric motor. Both would run off H2 but once the aircraft is at cruising altitude, the dry friction clutch would be disengaged and the ICE shut off.

Lugging traction batteries around in a light aircraft does not make a lot of sense to me, their low energy density would completely negate the benefit of using expensive H2 in the first place. You'd be a lot better off with a straight aviation diesel engine.


This is pretty impressive. I wonder if ultracapacitors could replace the Li-Ion batteries at some point.


Lithium-ion - 220 Wh/kg. Ultracapacitor - 10 Wh/kg. The ultracapacitors would be 22 times heavier, so not ideal for aircraft.

Incidentally, for anyone interested in real lithium-ion powered flight, check this out - it's amazing!

Click on the video links near the top of the page.

Mridul Kashatria

How about burning hydrogen directly in aircraft engine?
How much of h2 would be required for this?


One big problem I see with an airplane using hydrogen is that it would require a lot of room that planes just don't have. Or else massive amounts of pressure, and just hoping you don't hit a bird and explode. Either way, I don't see it working in a plane, but it's good to see them experimenting anyway.

Shannon Sheldon

I never heard that electricity was being used in any aircraft, even smaller planes. It is something to watch and wait for.



It is worth checking what the model aircraft people are doing with electric flight. Some enormous advances are being made with LiPo batteries and brushless motors. Maybe some of this technology will transfer to full sized aircraft.

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