ZeroAvia is celebrating a “major step” towards certification of its ZA600 hydrogen-electric powertrain, after the U.S. Federal Aviation Administration (FAA) published special conditions to certify the system’s electric engine component.
The FAA published 33 special conditions for ZeroAvia’s ZA601 electric propulsion unit as a Final Rule to the Federal Register on 18 March.
“Having special conditions for our electric propulsion system published by the FAA is an enormous achievement that underscores the aerospace maturity of our organization and illuminates our path forwards towards type certification,” said ZeroAvia founder and chief executive Val Miftakov in a 2 April statement announcing the development.
The 600kW electric motor is a key part of ZeroAvia’s planned ZA600 hydrogen-electric powertrain, which is designed to power regional turboprops with up to 20 seats.
The UK- and US-based company recently confirmed that funding constraints had forced it to halve its workforce and push back its certification timeline. It now aims to certify just its fuel cell system by 2027, with certification of the entire ZA600 hydrogen-electric powertrain not expected until up to two years after that.
Nevertheless, the FAA’s publication of special conditions for the electric engine component is a “major step” forward, says ZeroAvia, coming as it does after the UK Civil Aviation Authority (CAA) awarded the company design organization approval late last year.
Miftakov says there is now “real momentum” in the race to develop emissions-free hydrogen-electric aircraft, noting: “The fundamentals have not changed — electric aircraft are better aircraft with zero emissions, less noise and better operating economics, and hydrogen is key to unlocking practical range and endurance.”
While the Z601 can partially be certified against the FAA’s existing Part 33 aircraft engine airworthiness standards, those standards were originally developed for gas-powered turbine engines. The electric engine must, therefore, also meet the additional safety requirements detailed under the FAA’s special conditions.
“Although [ZeroAvia’s] electric aircraft engines use a novel or unusual design feature that the FAA did not envisage during the development of its existing Part 33 airworthiness standards, these engines share some basic similarities, in configuration and function, to engines that use the combustion of air and fuel, and therefore require similar provisions to prevent common hazards (for example, fire, uncontained high energy debris and loss of thrust control),” explains the FAA in its final special conditions document.
“However, the primary failure concerns and the probability of exposure to these common hazards are different for the ZeroAvia Model ZA601 electric engine. This creates a need to develop special conditions to ensure the engine’s safety and reliability.”
Among the additional safety requirements that ZeroAvia’s engine must meet are the establishment of ZA601-specific engine operating limits related to power, torque, speed and duty cycles. ZeroAvia must also ensure the high-voltage electrical wiring systems that connect the controller to the motor are protected against arc faults. The FAA describes arc faults as the “high-power discharge of electricity between two or more conductors” that can trigger electrical fires.
The engine must also be designed in such a way that “if the main rotating systems continue to rotate after the engine is shut down while in-flight, this continued rotation will not result in any hazardous engine effects,” the FAA document goes on to say.
For the eventual full hydrogen-electric powertrain, ZeroAvia’s electric propulsion system will be powered by the 200kW fuel cell modules on which the company is currently focused. This power generation system is also being marketed, however, as “a discreet product for UAV, eVTOL [electric take-off and landing vehicle] and general aviation applications,” says ZeroAvia.
The company’s chief strategy officer, James McMicking, noted during ZeroAvia’s recent Hydrogen Aviation Summit that it had found, over the last year, “some interesting applications for the technology…in smaller categories of air vehicles and in different market segments that create opportunities to mature the technology and start to build up the industrial base you need to eventually scale to more commercial applications.”
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Featured image credited to ZeroAvia
