The Battery Mass Penalty: Why eVTOL Propulsion Demands External Energy

The fundamental propulsion challenge for UAM aircraft is that electric vertical take-off and landing (eVTOL) operations consume disproportionately large amounts of energy during take-off and landing compared to cruise. A UAM device operating at altitudes of 500 to 600 meters requires enormous energy just to ascend vertically, and increasing battery capacity compounds the problem by adding airframe weight — which in turn demands yet more battery capacity. This compounding mass penalty fundamentally constrains range and has driven multiple patent approaches aimed at offloading peak energy demand to external systems rather than enlarging onboard battery packs.

One architectural response to the mass penalty is tethered power delivery during take-off. Hyundai Motor Company’s 2023 patent describes a system in which a ground-based charging station provides power via a cable managed by an auxiliary mobility device, supplying the UAM aircraft through its most energy-intensive flight phase and then disengaging cleanly. This decouples take-off energy from onboard storage, allowing smaller and lighter battery systems to be carried for cruise and landing. A closely related solution for the landing phase deploys a drone from a hub to autonomously dock with a UAM aircraft in landing mode and deliver supplemental power when onboard battery reserves are insufficient — addressing the safety-critical scenario of a depleted battery during final approach.

An alternative propulsion architecture entirely avoids the pure-electric energy bottleneck through hybrid distributed propulsion. As disclosed in Thinkware Corporation’s 2023 patent, the aircraft includes a fuel-burning power generation unit alongside a rechargeable battery unit, with a power supply path control unit dynamically selecting the energy source — generator, battery, or both — based on the current flight stage. Multiple fan modules receive power from this blended supply, enabling the system to optimise between fuel efficiency during cruise and maximum power availability during take-off and landing. This architecture explicitly addresses range limitations inherent in all-electric designs while preserving the distributed propulsion redundancy that is central to eVTOL safety philosophy.

Battery standardization represents a further structural dimension of propulsion architecture. Rihai Co., Ltd.’s 2025 patent proposes an operating system that bridges standardized and non-standardized battery packs, enabling mass production economics and simplified logistics for UAM operators. Standardization directly affects the certification pathway, as regulators require consistent, repeatable energy system behaviour across the operational fleet. Additionally, V-Space Co., Ltd.’s 2025 patent details a battery management method that uses operational status information — specifically take-off and landing signals — to individually control multiple battery pack modules, enabling phase-specific power optimisation and state-of-health monitoring critical for continued airworthiness.

“Increasing battery capacity compounds the problem by adding airframe weight, which in turn demands yet more battery capacity — a compounding mass penalty that fundamentally constrains range.”

Avionics Architecture and the Wireless Charging Certification Gap

The avionics system architecture for eVTOL aircraft operating in UAM scenarios differs fundamentally from both conventional commercial aviation and consumer drone platforms, and no unified regulatory framework yet governs it. Beihang University’s 2024 patent proposes a three-layer architecture comprising an onboard tier, a cloud tier, and a ground tier. Safety-critical functions — including the communication system, navigation system, surveillance system, flight management and control system, and energy and propulsion system — are consolidated in the onboard core system. Non-safety-critical functions are offloaded to the cloud, and the entire system interconnects via wireless networks.

Navigation precision is a direct certification requirement. Korea Airports Corporation’s 2023 patent addresses this through a dedicated UAM navigation device deployed in left-right sets along prescribed corridors, generating radio signal-based 3D flight paths with altitude inclusion. The UAM onboard payload identifies its current position as the intersection of the left and right radio signals on an instrument panel — a precision navigation capability analogous to instrument landing systems (ILS) in conventional aviation, adapted for low-altitude urban environments. This infrastructure-dependent navigation design raises important certification questions about the inter-dependency between ground infrastructure standards and the airworthiness of the vehicle itself.

Terrain awareness is one of the most challenging avionics certification domains for UAM, given the density of urban obstacles at low altitudes. According to the FAA, advanced avionics certification for novel aircraft categories requires new means of compliance that do not map onto existing frameworks. Honeywell International’s 2021 patent adapts traditional ground proximity warning systems for the urban environment by constructing a spatial buffer around the aircraft and applying an altitude-dependent vertical threshold to identify and visually distinguish objects in 3D map data that fall within the buffer. This close-object awareness indicator is designed for the specific threat model of UAM operations — lateral building clearance, power lines, and urban canyons — rather than the terrain-following scenario of conventional aviation TAW systems. As noted by EASA in its Special Condition for VTOL aircraft, novel categories require dedicated airworthiness standards rather than adaptation of fixed-wing rules.

Energy replenishment infrastructure at vertiports is a second major engineering challenge tightly linked to certification. Hyundai Motor Company’s 2024 patent implements magnetic resonance charging panels installed in airborne charging stations, transmitting power wirelessly to a compatible panel embedded in the UAM aircraft. Accurate pad alignment is the key engineering challenge: Hyundai Mobis’s 2023 patent achieves this through a two-stage process in which initial coarse positioning is followed by fine alignment based on measured charging efficiency, stopping the aircraft only when the alignment meets the threshold required for high-efficiency power transfer. Certifying such integrated airframe-infrastructure electrical systems will require both aircraft-side and ground-side standards to be developed and harmonised — a challenge for which no established precedent yet exists.

Safety Systems, Airspace Management, and the Regulatory Stack

UAM certification challenges extend well beyond the aircraft itself into the full operational ecosystem. The Korea Atomic Energy Research Institute’s 2024 patent explicitly addresses the unique inspection requirements of UAM as a multi-passenger air vehicle, developing a system that simultaneously inspects airframe structural defects and battery pack component degradation during every passenger transport flight. This represents a fundamental departure from conventional aviation maintenance intervals — proposing near-continuous structural health monitoring as a requirement for high-frequency urban operations, a paradigm that will require novel continuing airworthiness regulations incompatible with current scheduled maintenance frameworks.

Collision avoidance and conformance monitoring are central operational safety requirements with direct regulatory implications. LG Uplus’s 2025 patent describes a system-level approach in which a centralised UAM management system collects cooperative aircraft location data, detects aircraft entering UAM airspace, projects estimated flight paths to identify potential conflicts, and calculates and transmits alternative paths to affected UAM vehicles — establishing a functional architecture for UAM traffic separation services. Complementing this, SK Telecom’s 2025 patent provides a mechanism to detect when a UAM vehicle deviates from its approved flight plan by generating flight conformance regions from plan data and comparing them against actual route information — a function required by performance-based navigation regulations as defined by ICAO.

The Korea Institute of Civil Engineering and Building Technology’s 2025 patent introduces an extended reality framework in which virtual walls are placed in 3D spatial data around specific urban objects, and the UAM flight control system synchronises the real aircraft’s position with a simulated position in the extended reality application to enforce collision avoidance. This approach raises novel certification questions: the trustworthiness of the spatial data, the latency of synchronisation, and the behavioural certification of the extended reality application itself as a safety-critical software component — categories not yet addressed in existing RTCA software standards.

Communication network security constitutes a further certification frontier. Jeon Sang-hun’s 2024 patent establishes a multi-domain mutual authentication protocol requiring both vehicle-side and operator-side verification before command authority over a UAM device is granted to any external system. This type of security architecture must ultimately be certified against aviation cybersecurity standards such as RTCA DO-326A, which are currently undergoing adaptation for unmanned and urban air mobility platforms. Hanwha Systems’ 2025 patent further addresses operational continuity by combining 5 GHz band wireless networks with low-orbit satellite networks to provide connectivity independence from ground-based 5G infrastructure at operational altitudes of 300 to 600 meters — a direct response to the failure mode where terrestrial network outages could compromise command-and-control links for UAM aircraft.

Ground-based automated flight management also emerges as a certification-relevant architecture choice. Honeywell International’s 2022 patent discloses a ground control system that automatically and remotely controls UAM vehicles using localised temporal data, releasing control only when further intervention is deemed unnecessary. This remote-pilot-in-command architecture — where the ground system assumes responsibility during critical phases — requires regulatory determination of where pilot certification obligations reside and what minimum performance standards the automated ground system must meet to qualify as a command authority. According to WIPO‘s global IP data, the pace of UAM-related patent filings has accelerated significantly since 2021, reflecting the urgency with which industry is attempting to resolve these systemic challenges ahead of regulatory frameworks.

Who Holds the Patents: Key Players and Emerging Innovation Trends

The UAM patent landscape spans jurisdictions including the United States, Korea, China, Europe, and Japan, with Korean-origin filings comprising the majority of active and pending records in this dataset of over 40 patent records. The dominant technical themes cluster around three areas: electric and hybrid propulsion energy architectures; avionics system design for eVTOL platforms; and operational safety and airspace management.

Hyundai Motor Company is the single most active assignee in UAM propulsion and energy management, holding active patents in the US and EP on wired power supply during take-off and landing, drone-based supplemental power delivery systems, and unmanned ground robot integration for vertiport operations. Their filings span from 2023 through 2026, indicating sustained and expanding R&D investment. Their affiliate Hyundai Mobis holds the dominant position in wireless charging for UAM, with multiple active patents in the US and EP covering pad alignment, two-stage charging protocols, and sensor-based positioning.

Honeywell International Inc. is the leading avionics-focused assignee, with active US patents covering off-board recharge station display systems, terrain awareness and warning adapted for UAM, and ground-based automated flight management. Honeywell’s filings span 2021 to 2024, addressing both propulsion energy awareness and operational safety systems. LG Uplus and SK Telecom are the primary Korean telecommunications contributors, active in collision avoidance, traffic flow management, conformance monitoring, and flight path re-routing — collectively building the software infrastructure layer that UAM traffic services will depend upon. KT (Korea Telecom) contributes through UAM traffic environment simulation systems and airborne communication relay patents, supporting both network design validation and operational connectivity. You can explore the full assignee landscape using PatSnap’s IP intelligence platform.

Beihang University (Beijing University of Aeronautics and Astronautics) represents the academic-research contribution, with a foundational 2024 patent on eVTOL avionics system architecture — directly addressing the absence of a unified avionics framework and providing a conceptual model that could inform future regulatory standards. Thinkware Corporation holds the primary hybrid distributed propulsion system patent, covering the fuel-battery power blending architecture that extends range beyond all-electric limitations. Hanwha Systems contributes the satellite-5GHz hybrid communication architecture critical for communication link certification above urban ground station coverage zones.

“The trend across the dataset is a clear shift from vehicle-level propulsion patents toward ecosystem-level integration patents — charging infrastructure, traffic management, communication security, and conformance monitoring — signalling that the industry perceives the certification bottleneck as increasingly systemic rather than purely aircraft-level.”

This systemic shift has significant implications for how certification bodies approach UAM. Rather than certifying a single aircraft type, regulators will need to certify interoperable systems — vehicle, infrastructure, communication network, and traffic management — simultaneously. The PatSnap R&D intelligence platform enables aerospace engineers and certification specialists to track this evolving landscape across all active filing jurisdictions in real time.