The Future of Advanced Air Mobility

Apus Wins Strategic Funding for Family of Hydrogen-powered Aircraft

Software entrepreneur Rolf-Jürgen Moll is joining Germany's Apus Group as a strategic investor in its plans to develop hydrogen-powered aircraft. The company’s January 18 announcement did not disclose the amount of the new funding, but APUS founder and CEO Phillip Scheffel said that it has now raised €40 million ($43 million)—enough to support work to have an initial prototype flying in the first half of 2024.

Apus, which is based at Strausberg Airport near Berlin, is developing a four-seat aircraft called the i-2 and the larger i-5, which is a 14-passenger commuter model. Both will feature Apus’s own design for a fuel-cell-based powertrain burning gaseous hydrogen, and are expected to be priced at €1.4 million and €3.8 million, respectively.

The Berlin-based founder of the LucaNet financial software provider, who is a pilot and aviation enthusiast, will be involved in supporting the Apus team as it works toward a goal of certifying its first aircraft in 2025. The company has been working on its technology since 2015 and expects to have an initial prototype of the i-2 design ready to start ground testing by the end of 2023.

The hybrid configuration features a combination of fuel cells and batteries, with the latter providing additional power during takeoffs. The i-2 will have a pair of nacelle-mounted electric motors and there will be four 150-kW motors on the larger i-5 model. For safety, each set of motors, fuel cells, 40-kW batteries, and all associated components and systems will be able to operate independently in the event of a failure in part of the powertrain. 

Both aircraft designs feature integrated fuel tanks for the gaseous hydrogen that are built into the wing, and these essentially serve as spars, reducing overall airframe weight in the process. This design, patented by Apus under the trademark Tubestruct, is expected to support an impressive energy density of 3,000 Wh/kg. The fuel cells will be installed in the nose of the aircraft.

Green Options for Private Fliers and Regional Airlines

Scheffel told FutureFlight that he expects the i-2 to attract private individuals and companies seeking convenient transportation options but without the environmental impact of aircraft that depend on fossil fuels. It will have a range of around 500 nm and a cruise speed of 160 knots, which he believes will make it competitive with aircraft such as the Cirrus SR20 piston single, which has more range at just over 700 nm.

The i-5 is intended for roles including both passenger and cargo services, and could also be configured for a variety of multi-mission applications. The distinctive twin-boom design, which will have two motors on each side of the wing, is expected to deliver a payload of 1,770 kg (3,894 pounds), a range of 800 nm, and a cruise speed of 160 knots.

Apus Group's i-5 hydrogen-powered commuter aircraft.
Apus Group is also developing a 14-passenger hydrogen-powered aircraft called the i-5 that could be used for cargo and utility applications. (Image: Apus Group)

One factor in Apus’s choice of gaseous hydrogen over liquid fuel is that the company sees the former being more available at airports and airfields in the near to medium term since it can be more readily delivered in mobile tanks. Based on current hydrogen gas prices of around €5 per kilogram, the company is projecting seat-mile costs for the i-5 of just €0.13 and ton-mile costs for freight of €0.99.

Lower Operating Costs

Another anticipated saving in operating costs is based on the longer mean time between overhauls for fuel cells, which Apus sales and business development manager Laurent Altenburger said will result in significantly lower maintenance costs. The company has estimated that the overall operating cost will be 40 percent less than for a Cessna 208B Grand Caravan turboprop single, which is one aircraft the i-5 could potentially replace. The i-2 would have operating costs that are around 20 percent lower than those of the SR20.

Still to be determined—and a significant unknown factor in the timeline for service entry of the first hydrogen aircraft—is the basis on which aviation regulators will certify the new propulsion technology. According to Apus, it is the only hydrogen pioneer to have formally started the type certification application process with EASA, with an application having been filed with the European air safety agency. For the i-5 model, the company has made a type certificate application with Germany's LBA regulator.

The company, which has also received funding from the German government and the European Union, already holds both design and production organization approvals from the EASA. It has existing revenue streams from its work supporting other aircraft manufacturers as an engineering subcontractor and also from flight services support.

Apus had intended to source the electric motors from aircraft engine manufacturer Rolls-Royce, but the 135 kW to 150 kW units it had specified are no longer available. It has now turned to France's Safran group for the motors.

Garmin is expected to provide its G1000 avionics suite for the i-2 and i-5 aircraft. Other existing program partners include fuel-cell manufacturer Power Cell, high-voltage-converter specialist Fraunhofer, and aircraft-structures supplier Heggemann, which is assisting with the hydrogen storage tanks.

Apus, which takes its name from the Latin word for the Swift bird, exhibited a mockup of the i-2 at last year’s Aero Friedrichshafen show in Germany. Flight controls for it and the i-5 are conventional cables for ailerons and rods for elevators, actuated by two side yokes on the outboard sides of the cockpit. The landing gear is retractable and will be electro-hydraulically actuated.

According to Scheffel, who was formerly with German motor glider manufacturer Stemme, Apus’s focus on the general aviation and regional airline markets is based on its belief that these are the most attainable goals with the current state of hydrogen propulsion capability. “The stairway to heaven [i.e. larger zero-emissions aircraft] has a lot of steps," he commented, "and you can’t jump over the first of these so you first have to design the basic technology and make it reliable with the lowest amount of money and risk." From the start, the company ruled out battery-based propulsion on the basis that it can’t deliver the endurance and payload that it feels is necessary to be commercially viable in an aviation context.

Apus intends to manufacture both aircraft at its existing site in Strausberg. It currently employs 40 people and intends to increase the payroll to 55 this year with multiple new positions now being advertised.