The review examines electrified aircraft propulsion through four interconnected lenses: propulsion architecture, certification frameworks, system safety assessment methods, and the certification-critical technical challenges that emerge when the two former elements collide. This structure reflects a key insight of the analysis: the way a propulsion system is architected fundamentally determines how difficult it will be to certify. An all-electric design with a single high-capacity battery pack presents a fundamentally different regulatory problem than a hybrid-electric arrangement that couples a turbine engine with electric machines, power electronics, and a transmission network, or a turboelectric concept in which gas turbines generate electricity for distributed motors. Each configuration distributes failure modes, redundancy, and power flows differently, and regulators must evaluate each accordingly.

The authors analyze the major configurations in detail. All-electric propulsion, exemplified by NASA’s X-57 Maxwell program, replaces fuel with batteries and electric motors, promising zero in-flight emissions and radically simplified drivetrains. Hybrid-electric propulsion blends battery and turbine power, offering extended range while retaining some of the operational flexibility of conventional aircraft. Turboelectric systems use generators driven by gas turbines to supply electric motors without onboard energy storage, sidestepping some battery limitations at the cost of added conversion losses. Distributed electric propulsion, or DEP, spreads many smaller motors across the wing or airframe, enabling aerodynamic benefits such as higher lift coefficients and shorter takeoff distances, but introducing complex fault-tolerance questions when any single motor or its power electronics fails. The review shows that certification complexity grows in a strongly architecture-dependent way: DEP, for instance, requires demonstrating that the aircraft can safely tolerate motor failures and power distribution faults across an interconnected network, something conventional single-engine certification rules never anticipated.

On the regulatory side, the review surveys the approaches of the three major airworthiness authorities: the European Union Aviation Safety Agency (EASA), the Federal Aviation Administration (FAA), and the Civil Aviation Administration of China (CAAC). EASA has pioneered special conditions for electric and hybrid propulsion systems, including Special Condition SC E-19 for electric and hybrid propulsion systems and SC-VTOL-02 for small-category VTOL-capable aircraft. The FAA has issued advisory circulars for powered-lift type certification and maintains standards for rechargeable lithium cells and batteries under TSO-C179b, drawing on RTCA’s DO-311A minimum operational performance standards. CAAC has published special conditions for unmanned aircraft systems and, notably, has released airworthiness standards for powered-lift aircraft. These frameworks share a common philosophy: because existing regulations were written around combustion engines, novel propulsion requires applicants to demonstrate, through special conditions and means of compliance, that equivalent levels of safety are achieved even where prescriptive rules do not yet exist.

At the heart of the safety substantiation process lies system safety assessment, formalized in industry standards such as SAE ARP4761A for safety assessment and ARP4754A for civil aircraft and systems development. These methodologies require identifying failure conditions, classifying their severity from catastrophic to minor, and demonstrating that the probability of catastrophic events falls below stringent numerical thresholds, typically on the order of one in a billion flight hours. The review highlights how model-based safety analysis and newer techniques such as System-Theoretic Process Analysis (STPA) are being integrated into this process to handle the systemic and software-driven failure modes that electrified architectures introduce. Digital twin technology, which creates high-fidelity virtual replicas of physical systems, is emerging as a complementary tool, supporting condition monitoring, prognostics and health management, and fleet-level surveillance of battery and electric drivetrain health throughout an aircraft’s service life.

Battery safety emerges from the review as perhaps the single most consequential certification-critical challenge. Lithium-ion cells can undergo thermal runaway, a self-accelerating exothermic failure in which a overheating cell ignites neighboring cells and propagates through the pack. In an aircraft, where batteries constitute a large fraction of the vehicle’s mass and sit close to passengers and critical structure, a thermal runaway event is treated as a design condition that must be contained. EASA has published dedicated guidance on thermal runaway for propulsion batteries, and the review traces the mitigation hierarchy: preventing cell-level failure through cell chemistry and quality control, arresting propagation through physical barriers and thermal management, and ensuring the aircraft can tolerate a complete loss of one battery segment. Recent research on battery thermal runaway prevention and on safety assessment for propagation mitigation, cited in the review, shows that containment design must be substantiated analytically and experimentally, a demanding requirement for packs large enough to propel transport-category aircraft.

High-voltage integration poses its own distinct set of hazards. Electrified aircraft will operate power networks at voltage levels far above those in conventional avionics, in an environment subject to altitude-induced low pressure, temperature extremes, vibration, and electromagnetic interference. Insulation degradation, partial discharge, arcing, and electromagnetic compatibility failures all threaten both the propulsion system and neighboring aircraft systems. The review points to environmental qualification standards such as RTCA DO-160G and software and hardware assurance frameworks including DO-178C and DO-254 as the established means of demonstrating that power electronics, controllers, and cabling can survive the airborne environment and that their software performs to the assurance levels that catastrophic failure conditions demand. Fault tolerance adds another layer: propulsion systems must detect failures rapidly and reconfigure, and in distributed architectures the loss of a motor changes not only thrust but flight dynamics, requiring coordinated control allocation strategies that themselves must be certified.

A recurring theme in the review is that architecture decisions made at the conceptual design stage ripple forward into every certification document an applicant will ever file. Redundancy provisions, segregation requirements, failure detection latency, and the sheer number of system interfaces all scale with architectural complexity. The authors therefore advocate architecture-aware certification strategies, in which certification implications are evaluated early and systematically as part of the design process rather than retrofitted after an aircraft configuration is frozen. They argue that this integration of certification thinking into architecture selection is now the primary challenge facing the sector, more so than improving any individual component, because today’s batteries, motors, and power electronics are increasingly technically viable while the pathway to proving whole-system safety remains immature and expensive.

The stakes of solving this challenge are considerable. International commitments, including the International Civil Aviation Organization’s long-term aspirational goal for international aviation, and the rapid growth of the advanced air mobility sector depend on certifiable electric propulsion. Programs such as NASA’s X-57, which documented its electric aircraft certification and airworthiness approach in detail, offer early lessons on how novel propulsion can be substantiated under existing frameworks, and scaled flight testing of distributed propulsion concepts continues to generate evidence on failure detection and control reconfiguration. But the review’s message is sobering and, at the same time, constructive: electrified flight will reach the market not simply when the technology works, but when the industry and regulators together can demonstrate, architecture by architecture, that it is safe. Bridging that gap, the authors conclude, will require certification strategies designed hand in hand with the propulsion architectures of the future.

Subject of Research: Airworthiness certification and safety assessment of electric and hybrid-electric aircraft propulsion systems

Article Title: Airworthiness certification and safety assessment of electric and hybrid-electric aircraft propulsion systems: architectures, frameworks, and critical challenges

Article References: Wang, X., Cao, A., Liu, Y., Hong, L., Zhou, B., Yuan, X., Liu, B., Bao, W., & Guo, J. (2026). Airworthiness certification and safety assessment of electric and hybrid-electric aircraft propulsion systems: architectures, frameworks, and critical challenges. Aerospace Systems. https://doi.org/10.1007/s42401-026-00526-6

Image Credits: AI Generated

DOI: 10.1007/s42401-026-00526-6

Keywords: electric aircraft, hybrid-electric propulsion, airworthiness certification, system safety assessment, distributed electric propulsion, battery thermal runaway, high-voltage integration, fault tolerance, EASA, FAA, CAAC, digital twin