Nanjing Airfly Electronic Technology Co., Ltd.

Tethered Power Solutions for Lightweight eVTOL Flight Testing Kitefly Tethered Technical White Paper Abstract The rapid advancement of Urban Air Mobility (UAM) and the low-altitude economy has placed lightweight eVTOL aircraft at the center of global aviation innovation. Ensuring safe flight testing, long-duration hover capability, and propulsion-system validation remains a major challenge for developers. This white paper presents Kitefly Tethered’s high-voltage tethered power architecture—combining a ground high-power supply, high-strength HV cable, and onboard DC/DC regulation module—to enable controlled, continuous, and energy-stable eVTOL testing. Through a complete solution featuring the G40pro Ground Power System and WF24 Onboard Regulation Module, this document demonstrates how teams can perform extended hover tests, redundancy simulations, thrust verification, and flight-control tuning with enhanced safety and repeatability. The architecture offers high efficiency, reduced operating cost, and compatibility with next-generation lightweight eVTOL power platforms. 1. Background: UAM Development and eVTOL Testing Challenges Lightweight eVTOL aircraft face multiple constraints during early-stage development: l Limited endurance during hover l Incomplete propulsion-system reliability verification l Uncertain battery safety margins l Risk of loss-of-control events With test frequency increasing, R&D teams urgently need a solution that ensures: l Safe fixed-area testing l High-voltage, high-power endurance capability l Repeatable aerodynamic and flight-control experiments l Permission to conduct tests in urban or regulated airspace Tethered power systems have therefore become a crucial tool for eVTOL developers.   2. Role of Tethered Systems in Lightweight eVTOL R&D 2.1 Reducing Flight Risk in Early Development A tethered system restricts the aircraft’s altitude and radius, keeping it in a controlled test environment.Even in cases of: l Power interruption l Thrust instability l Flight-control anomalies …the aircraft cannot drift or escape the designated zone—dramatically improving safety. 2.2 Enabling Long-Duration Hover & High-Power Tests Traditional batteries limit test duration to just minutes.This restricts: l Motor efficiency curve mapping l Thrust-stability measurements l Redundant propulsion switching tests l Long-duration vibration/noise evaluation With tethered power providing tens of kilowatts of stable DC output, tests can run for hours, yielding far more reliable data. 2.3 Allowing Safe Testing in Urban or Restricted Areas Free-flight testing often requires strict regulatory approval. By contrast, tethered testing is more easily authorized, since altitude and flight envelope are constrained.This enables testing in: l Factory test halls l Airport R&D zones l Urban-edge industrial areas l Enclosed eVTOL proving grounds 3. Typical Application Scenarios 1. Motor endurance and peak-output testing 2. Aerodynamic, blade, and vibration research 3. Flight-control algorithm tuning 4. Redundant propulsion system switching 5. Emergency-condition simulation 6. Controlled testing in regulated low-altitude airspace Tethered systems ensure testing is safe, continuous, repeatable, and controlled. 4. Kitefly Tethered’s Lightweight eVTOL Testing Solution A recent overseas lightweight eVTOL R&D project required: l Extended hover testing l High-voltage 1000 V DC input l Secondary regulation to 14S (60V) onboard power bus l Continuous, uninterrupted endurance tests Kitefly Tethered supplied a dedicated test architecture.   4.1 Ground Power System — G40pro Designed for High-Power eVTOL Testing Input: 380 V AC (three-phase)Output: 1000 V DCPeak Power: 30 kW Key Capabilities l Stable HV output for direct-drive propulsion systems l 30 kW peak for hover, pitch change, and acceleration loads l Industrial-grade isolation for safety l Compatible with high-voltage tether cables for long-duration tests   4.2 Onboard Regulation Module — WF24 High-Voltage → 14S Power Bus Conversion Peak Power: 24 kWInput: 800–1000 V DCOutput: 60 V (14S) WF24 Enables l High-efficiency voltage conversion l Stable 24 kW output for heavy-load flight l Continuous power for motors & avionics l Zero voltage drop or fluctuation under high thrust   5. Advantages of Kitefly Tethered’s eVTOL Test Architecture l High SafetyEliminates risk of runaway flights. l High-Power CapabilitySupports long-duration, high-load propulsion tests. l Lower Operational CostNo battery swapping, no degradation cycles. l Highly Repeatable DataEnables controlled, repeatable test conditions. l Roadmap CompatibilityFully aligned with modern lightweight eVTOL power levels (800–1000V). This architecture forms a foundation for large-scale future validation. Keywords:tethered eVTOL testing, 1000V DC ground power, G40pro, WF24, eVTOL hover endurance, Urban Air Mobility testing, lightweight eVTOL development, tethered power supply system Request a Customized eVTOL Test Solution Our engineering team can tailor a tethered-power architecture for your propulsion voltage, motor system, and testing roadmap.Email: susy@tetheredsystem.comWebsite: www.tetheredsystem.com  

As wind turbine dimensions continue to grow, the likelihood of lightning strikes increases significantly. Lightning may damage turbine control systems, electrical components, blades, and generators. It is estimated that lightning accounts for 80% of all wind turbine insurance claims, while lightning-related failures represent 60% of all blade losses. On average, each wind turbine suffers lightning-induced blade damage once every 8.4 years.For a typical 20-year turbine lifespan, this corresponds to 2–3 blade-damage incidents caused by lightning. To understand why wind turbines are frequently “targeted” by lightning, three key factors must be clarified: 1. Height and environmental exposure:Modern wind turbine tip heights exceed 150 meters, and greater height increases the probability of lightning attachment. 2. Rotational motion:Blade tip speeds reach 80–100 m/s, and such high-speed rotation intensifies electric charge accumulation, increasing lightning attraction. 3. Blade material characteristics:Blades are typically built from fiberglass or carbon fiber, which have poor conductivity.When lightning strikes, the electrical current has no direct path unless a dedicated lightning conduction path is embedded.   For this reason, blades must contain an internal Lightning Protection System (LPS) consisting of lightning receptors, down-conductors, and grounding terminals. Receptors are placed at blade tips and leading edges where strikes most commonly occur. They provide a low-resistance path to safely channel lightning current through the tower and into the ground. Traditional inspection methods rely on manual suspended baskets or aerial lift trucks. Inspecting a single wind turbine typically requires over 5 hours, allowing only 1–2 turbines to be inspected per day. Technicians must operate in suspended baskets tens of meters to over 100 meters above ground—facing extreme fall risks.Additionally: l Operations depend heavily on weather conditions (especially wind). l Large specialized equipment (cranes, aerial lifts) are required, causing very high inspection costs. l Bad weather suspends inspections, leading to schedule delays and increased risk. The industry urgently needs a new inspection method that dramatically enhances efficiency, reduces safety risks, and ensures measurement accuracy.This is the context in which UAV-based intelligent inspection technology has emerged—a revolutionary solution for the wind power industry. 2. Overall Technical Concept: Intelligent, Contact-Based, High-Efficiency Inspection To overcome the limitations of traditional methods, the wind power industry is moving toward intelligent and safer technologies.This solution uses a UAV as an aerial inspection platform.   The system uses a UAV to carry a specially designed contact-type detection module that remotely touches the lightning receptor/blade tip to complete the electrical loop. l A retractable conductive copper-mesh assembly is installed on top of the UAV. l When the UAV reaches the measurement area, the operator controls it to make physical contact with the blade receptor/tip. l A detection cable is fixed to the copper mesh and is automatically reeled in/out by a tether winch. l The winch connects to a ground micro-ohmmeter to measure conduction and resistance. This achieves direct measurement of blade tip continuity and grounding resistance without human high-altitude operations.   3. Core Advantages and Technological Innovations: Redefining the Wind Turbine Inspection Standard 3.1 Revolutionary Efficiency Improvement The UAV solution dramatically improves inspection efficiency.Traditional suspended-basket inspections take over 5 hours for one turbine.The UAV solution completes a single blade tip measurement in under 3 minutes, improving efficiency by hundreds of times. A full wind farm can be inspected within a very short window, significantly reducing turbine downtime and improving energy output. 3.2 Enhanced Safety on All Fronts One of the greatest advantages is the elimination of high-altitude human operations.All work is performed on the ground—no lifting equipment, no personnel elevation. Additional safety features include: l The detection cable is secured through a ring-type attachment, preventing UAV propellers from contacting the cable. l The system operates in a wider range of weather conditions, expanding usable working time. 4. System Components and Functional Description 4.1 UAV Platform The system uses an industrial-grade UAV with strong wind resistance and stability.Recommended models include: l DJI M350 l DJI M400 4.2 Conductive Copper-Mesh Contact Detector The detector consists of an annular-rod structure with an internal metallic conductive mesh.The detection cable is fixed to the mesh.This design increases contact area and enhances contact reliability. 4.3 Ground Automatic Tether Winch & Measurement System The ground system includes: l Tether winch (automatic reeling), connecting to the UAV copper mesh l Micro-ohmmeter for real-time resistance measurement Together they form the complete detection loop. 5. Application Scenarios: Full-Lifecycle Wind Power Inspection Solution 5.1 Scheduled Inspection for Onshore Wind Farms Ideal for preventive maintenance before lightning seasons.The system quickly completes full-farm blade grounding measurements, reducing downtime and preventing lightning-induced blade failures. 5.2 Offshore Wind Farm Detection Traditional offshore inspections are extremely difficult and costly.The UAV system eliminates the need for vessels and aerial lifts, significantly reducing operational difficulty and risk. 5.3 Turbine Installation & Commissioning During turbine installation, the UAV system can directly verify LPS grounding resistance after the turbine is fully assembled—something conventional stage-by-stage methods cannot do. 5.4 Lightning Protection Fault Diagnosis After a lightning strike, the UAV system performs rapid diagnostics to confirm LPS integrity, locate faults, and guide repairs—minimizing turbine downtime.   6. Technical Support & Service Assurance 6.1 Professional Engineering Support We provide a dedicated team with strong wind-power and UAV application backgrounds.Services include solution design, equipment selection, and on-site technical support. 6.2 Continuous Technology Upgrades We continuously optimize system performance and expand functionalities based on evolving industry needs.Multiple related patents form a comprehensive technical protection system. Detailed Specifications Detection Tether Winch & Copper Mesh Assembly No. Item Specification Remarks 1 Model AF-JP-100 Default 100 m cable 2 Weight 2500 g ± 20 g Includes 100 m cable 3 Dimensions 210 × 190 × 170 mm L × W × H 5 Input Power 24 VDC Includes AC 220V → 24V DC converter 6 Current 2–3 A Customizable; fiber-optic pass-through optional 8 Working Mode Plug-and-play — 9 Torque Adjustable knob Max 66 N 10 Copper Mesh Model AF-TW — 11 Copper Mesh Weight 590 g ± 20 g — 12 Copper Mesh Size 320 × 320 × 53 mm Top diameter 320 mm; recessed mesh with internal damping; max retraction 70 mm 13 Connection Cable directly connected to metallic mesh surface — 14 Mounting Method Includes DJI M350 quick-release mounting plate + 4 pcs M3×10 screws Connects to DJI M350 — Note Device includes copper mesh only; no structural connectors included Users may trim column height or enlarge mesh diameter as needed  

I. Background and Industry Demand With rapid urbanization, the cleaning and maintenance of high-rise façades, power plant cooling towers, and chemical facility exteriors have become urgent industrial needs.Traditional “spider-man” manual rope access cleaning faces three major challenges: · High safety risks: Personnel suspended at height, frequent accidents. · Low cleaning efficiency: Limited coverage per operation, time-consuming process. · Inconsistent cleaning quality: Manual operations make it difficult to maintain even pressure and full coverage. The market urgently needs an innovative solution that enables mechanized high-altitude operation, standardized cleaning processes, and integrated workflow management.The Kitefly Tethered Water-Supply Drone System was developed precisely to meet these needs. II. Core Advantages and Technological Innovations 1. Dual-Tether Technology Leading the Industry · In 2023, Kitefly pioneered the concept of “dual-tether cleaning,” achieving simultaneous power and water supply through the tether. · Enables long-duration hovering operation, breaking through the limitations of battery endurance. 2. High-Pressure Precision Cleaning · The cleaning gun supports pressures up to 25 MPa, effectively removing stubborn stains. · Multiple nozzle options available for foam coating, fine mist spraying, and directional jet washing, ensuring adaptable and efficient cleaning modes. 3. Intelligent Compatibility Platform · Three dedicated cleaning gun models compatible with DJI M400, FC100, and third-party assembled drones. · Modular quick-release design allows fast installation and dismantling, significantly improving equipment utilization. 4. Enhanced Safety and Reliability · Completely eliminates the risks of manual high-altitude work. · The tethered system ensures stable hovering and strong wind resistance during operation. III. System Composition and Functional Description 1. Power Water Pump System · Proprietary AF-B7 / AF-B11 pumps: power rating 7.5–11 kW, adjustable pressure 0–25 MPa. · Kärcher pump series available: lightweight and mobile for flexible operations. · Built-in filtration unit effectively reduces water streak residues and improves cleaning quality. 2. Specialized Cleaning Spray Guns - AF-Q1:Extend to 1.9m,Suitable for third-party assembled drones - AF-Q2:Extend to 3.7m,Optimized for DJI FC100 - M400-Q3:Compact design, compatible with DJI M400 platform 3. Water Delivery System · Nylon Hard Hose: Pressure-resistant up to 8 MPa, suitable for high-intensity operations. · Braided Flexible Hose: Highly flexible, easy to route and store. · Standard Quick-Connect Fittings: Convenient and reliable connections. 4. Auxiliary Equipment · Manual Hose Reel: Enables rapid water hose retrieval. · Reinforced Support Rod: Enhances stability when operating long spray bars. · Specialized Cleaning Agents: Optimized formulations for different surface materials.  VI. Application Scenarios 1. Urban High-Rise Buildings · Routine glass curtain wall cleaning · Aluminum panel façade maintenance · Marble exterior surface cleaning 2. Energy and Power Facilities · Power plant cooling tower cleaning · Photovoltaic panel dust removal · Wind turbine tower maintenance 3. Industrial and Chemical Facilities · Reactor tower surface cleaning · Storage tank exterior maintenance · High-altitude pipeline rust and stain removal 4. Specialized Scenarios · Bridge pier cleaning · Stadium roof maintenance · Heritage building protective cleaning VII. Technical and Service Support 1. Professional Technical Assistance · Integrated system design · On-site installation and commissioning · Operator training and certification 2. Comprehensive After-Sales Service · Manufacturer-backed service for in-house developed equipment · Official Kärcher after-sales support · Fast-response maintenance 3. Continuous Product Upgrades · Customizable water pressure configurations · Continuous R&D of spray gun accessories · OTA software updates 4. Industry Ecosystem Development · Cleaning Alliance membership system · Partner technology sharing · Joint industry standard formulation VIII. Conclusion Through technological innovation and system integration, the Kitefly Tethered Drone Water-Supply Cleaning Solution achieves safer, more efficient, and standardized aerial cleaning operations, offering a new technological path for building maintenance and industrial cleaning.Looking forward, Kitefly will continue to advance tether technology, expand its application scope, and work with partners to promote the intelligent transformation of high-altitude operations. Safer, More Efficient, More Intelligent — Kitefly Tethered, Redefining the Future of Aerial Cleaning.