The Vertical Take-Off Energy Problem and UAM Propulsion Architecture Responses

The fundamental propulsion challenge for UAM aircraft is that 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 metres requires enormous energy just to ascend vertically, and increasing battery capacity to compensate compounds the problem by adding airframe weight — which in turn demands yet more battery capacity. This compounding mass penalty, documented in a 2023 Hyundai Motor Company patent, fundamentally constrains range and has driven multiple architectural approaches aimed at offloading peak energy demand to external systems rather than enlarging onboard packs.

One architectural response is tethered power delivery during take-off. A 2023 Hyundai Motor Company 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 approach decouples take-off energy from onboard storage, allowing smaller and lighter battery systems to be carried for cruise and landing.

A 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. This 2024 Hyundai Motor Company patent represents one of the first documented architectural solutions to the low-battery emergency landing problem in UAM operations, a scenario that conventional aviation emergency procedures do not cover.

The alternative to managing the all-electric energy bottleneck is to avoid it entirely through a hybrid distributed propulsion system. As disclosed in a 2023 Thinkware Corporation patent, this architecture 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.

“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.”

Battery standardisation represents a further structural dimension of propulsion architecture. A 2025 Rihai Co., Ltd. patent proposes an operating system that bridges standardised and non-standardised battery packs, enabling mass production economics and simplified logistics for UAM operators. Standardisation directly affects the certification pathway, as regulators require consistent, repeatable energy system behaviour across the operational fleet. A 2025 V-Space Co., Ltd. patent adds a battery management method that uses 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.

Avionics Architecture and Vertiport Energy Replenishment: New Engineering Frontiers

The avionics system architecture for eVTOL aircraft operating in UAM scenarios differs fundamentally from both conventional commercial aviation and consumer drone platforms, requiring a purpose-built framework. A 2024 Beihang University 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. Non-safety-critical functions are offloaded to the cloud, and the entire system interconnects via wireless networks. The paper explicitly observes that no unified regulatory framework yet governs UAM avionics, making the architecture research itself a prerequisite for certification standardisation.

Navigation precision is a direct certification requirement. A 2023 Korea Airports Corporation 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 inter-dependency between ground infrastructure standards and airworthiness of the vehicle itself, a challenge that bodies such as ICAO and EASA are only beginning to address.

Terrain awareness is one of the most challenging avionics certification domains for UAM, given the density of urban obstacles at low altitudes. A 2021 Honeywell International 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, and represents a new product category requiring novel regulatory means of compliance under existing DO-161 and TAWS regulatory categories.

Energy replenishment infrastructure at vertiports is a second major engineering challenge tightly linked to certification. A 2024 Hyundai Motor Company 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: a 2023 Hyundai Mobis 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.

Operational Safety, Airspace Management, and Communication Certification

UAM certification challenges extend well beyond the aircraft itself into the operational ecosystem. A 2024 Korea Atomic Energy Research Institute 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. A 2025 LG Uplus 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, a 2025 SK Telecom 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 referenced in guidance published by the FAA.

A 2025 Korea Institute of Civil Engineering and Building Technology 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.

Communication network security constitutes a further certification frontier. A 2024 patent from Jeon Sang-hun 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. Guidance from RTCA and standards bodies including EUROCAE is expected to evolve significantly as UAM operations approach commercial scale.

A 2025 Hanwha Systems patent 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 metres. This is a direct response to the failure mode where terrestrial network outages could compromise command-and-control links for UAM aircraft — a failure mode that must be mitigated before regulatory approval of beyond-visual-line-of-sight UAM operations. Ground-based automated flight management also emerges as a certification-relevant architecture choice: a 2022 Honeywell International patent discloses a ground control system that automatically and remotely controls UAM vehicles using localised temporal data, raising the regulatory question of where pilot certification obligations reside when a ground system assumes command authority during critical flight phases.

Patent Landscape: Who Is Building the UAM Technology Stack

The UAM patent landscape analysed here spans jurisdictions including the United States, Korea, China, Europe, and Japan, with Korean-origin filings comprising the majority of active and pending 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. 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.

Key Assignee Profiles

Hyundai Motor Company is the single most active assignee in UAM propulsion and energy management within this dataset, 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. 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 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 — placing them at the intersection of avionics certification and UAM infrastructure. 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. KT (Korea Telecom) contributes through UAM traffic environment simulation systems and airborne communication relay patents, supporting both network design validation and operational connectivity.

Beihang University represents the academic-research contribution with a foundational 2024 patent on eVTOL avionics system architecture for UAM scenarios — directly addressing the absence of a unified avionics framework. Thinkware Corporation holds the primary hybrid distributed propulsion system patent. Hanwha Systems contributes the satellite-5GHz hybrid communication architecture critical for communication link certification above urban ground station coverage zones. The PatSnap IP intelligence platform enables analysts to track these assignee portfolios across all five jurisdictions in real time, while PatSnap R&D intelligence tools map the technical convergence between propulsion, avionics, and communications domains that defines the current UAM innovation frontier.

“The trend across the dataset is a clear shift from vehicle-level propulsion patents toward ecosystem-level integration patents — signalling that the industry perceives the certification bottleneck as increasingly systemic rather than purely aircraft-level.”