# Overview
The XM2 Earth **EON800** Tether System is a bolt-on power and fiber connectivity solution for the Freefly Systems **Alta X** UAS. Designed to extend endurance and enable real-time data transfer, the system embeds high-voltage conductors and eight fiber optic cores within the **Tether Fiber Cable**, providing continuous powered connectivity between ground and air.
A 240V, 30A power supply (from a [Generator](https://xm2labs.gitbook.io/eon800-user-guide/freefly-altax-tether-eon800-xm2/reference/eon800-altax-generator-specs) or equivalent source) feeds the **Tether Ground Station** (**TGS**). The **TGS** transmits power and fiber data through the Tether Spool and up the Tether Cable to the **EON800** **Air Power Unit** (**APU**) on the aircraft. From there, power is distributed to the **Alta X** and any onboard payloads.
The tether acts as both a power conduit and high-speed fiber data link, forming a secure and uninterrupted connection between ground-based systems and the airborne platform. Ground payloads can interface directly with aircraft payloads via the fiber input on the tether spool, enabling seamless data transmission to and from the airframe.
Combined with a [generator or equivalent](https://xm2labs.gitbook.io/eon800-user-guide/freefly-altax-tether-eon800-xm2/reference/eon800-altax-generator-specs) energy source, the **EON800 Tether System** delivers reliable power, low-latency communication, and dramatically extended flight times for demanding industrial, defence, communications, and data applications.
Tethered Freefly Systems ALTA X Powered by XM2's EON800 Tether System | EON800-AX
EON800 Tether Ground Station | Portable and User Friendly
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## EON800 System Components
### EON800 Air Power Unit for ALTA X | **EON800-AX APU**
FRONT: EON800 APU for Freefly Systems ALTA X
The **EON800 Air Power Unit** (**APU**) is engineered for easy and rapid installation and seamlessly integrates with the Freefly **Alta X**. Mounted directly to the aircraft, the **APU** serves as the central power and data interface between the tether system and the drone.
The **APU** is also equipped with onboard batteries that provide backup power in case of a temporary loss of power from the tether system, ensuring the uninterrupted operation of the aircraft’s critical functions. These batteries are particularly essential during situations involving high-power draw payloads (e.g., large cameras, lighting equipment) or strong winds, which may cause power spikes or fluctuations. In these cases, the batteries help smooth voltage fluctuations, preventing disruptions to the aircraft’s performance and ensuring continuous operation even under demanding conditions.
The Battery Management System (BMS) integrated into the **APU** ensures the safe and efficient operation of the onboard batteries. It continuously monitors the health of each battery cell, regulates voltage and current, balances the load, and protects against overcharging, undercharging, and overheating. The BMS communicates with the APU and its data is accessible via the Tether Ground Station (TGS) onboard display, providing real-time insights into the battery’s status, health, and power consumption.
In addition to power and data connectivity, the APU also features thermal management through cooling fans, which pull cool air through the system to regulate the temperature of power components.
The front-facing ports on the **APU** allow for easy integration of both power and fiber connections, ensuring fast setup and seamless operation in the field.
BOTTOM: EON800 APU for Freefly Systems ALTA X
*Quick-Release Mounting Pins* directly attach to the pre-existing attachment points on the *Alta X Battery Tray*.
PROFILE: EON800 APU for Freefly Systems ALTA X
The **APU** is designed to primarily mount two 6S 10,000 mAh backup batteries, each plugging into the **APU** panel-mounted connections. Smaller or larger batteries can be installed if required. *Power Output Pigtails* are installed on the **APU**, connecting to the *ALTA X standard Battery Inputs*.
TOP: EON800 APU for Freefly Systems ALTA X
The serial port connects the **APU** with the **Alta X** flight controller.
EON800 Air Power Unit for ALTA X UAS
### EON800 Tether Ground Station
The EON800 **Tether Ground Station** (**TGS**) provides power to the tether cable and up into the **ALTA X** via the **APU**. \
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The **TGS** is designed to fit around a 4U enclosure for rack mounting. The system's front panel includes an *LCD* user interface, allowing operators to monitor the **ALTA X** tethered performance.
An ethernet port on the front of the **TGS** provides a UDP MAVLink feed to the ALTA X flight controller.
'*ALTA QGroundcontrol*' is enabled through the tether cable, similar to conventional usage over USB or Wi-Fi.
## System Performance
### Power Draw and Performance Details
The power draw of the **ALTA X** depends on the weight the aircraft is carrying, as well as other factors like wind speed and altitude. In ideal conditions at sea level, the graph below shows the current draw of the **ALTA X** when powered by the EON800 system. The EON800 for Alta X **Air Power Unit** provides 46-50V DC power to the Drone and Payload. The output voltage of the Air Unit varies with load. The graph below shows how output voltage varies with current draw.
EON800 and Tethered ALTA X Performance Graph
### How Much Weight Can The System Carry?
The maximum capacity payload for the EON800 powering the **Alta X** depends on many factors. The graph below shows the maximum possible payload for any given altitude, at various payload power draw levels. These figures are calculated for a drone using *6s 10,000mAh batteries*, using XM2 **SLG-20 Retractable Landing Gear**. These maximum payload weights reflect the limitation on gross weight discussed below.
Tethered Alta X Maximum Payload Capacity
### Function of the Backup Batteries
The backup batteries operate in parallel with the power system. The voltage of the backup batteries will float at the output voltage of the tether system, depending on the load. This means that as load increases (takeoff), the backup batteries will discharge, and as load decreases (landing), the backup batteries will be charged. The voltage of the backup batteries will also fluctuate as the batteries handle burst current to react to wind gusts, etc.
The backup batteries are designed to supply burst current and reserve capacity, acting as a backup in case of a power system failure, like when the generator runs out of fuel. This backup ensures the capability for emergency landings. The appropriate size of this backup battery depends on the aircraft and payload. For example, a suitable size for the 25-30kg **Alta X** would be two 6s 10Ah batteries in series.
The **EON800** may cause a reduction in voltage output under heavy loads, impacting the backup batteries' ability to maintain full capacity. When choosing the right battery size, consider this aspect for optimal performance.
### Fiber Communications
The Tether Fiber Cable consists of four single-mode fibers. One of these fibers is specifically allocated for controlling the ALTA X, while the remaining three fibers are available for the users payloads.
Typically, two out of the three payload fibers establish a full-duplex connection with the payload device, while the third fiber serves as a backup or secondary link. This third fiber ensures continued functionality in case of any damage to the primary fibers and can also support simplex or half-duplex modes for an extra device. We've designed this versatility to enables multiple payload setups, such as operating an LTE radio and a camera simultaneously, each with its independent fiber connection.
The EON800-AX Air Power Unit has a serial port to connect to the ALTA X flight controller. The *Ethernet Port* on the **Tether Ground Station** provides access to this MAVLink feed via UDP.
## Notes on Power limit, Payload, and Gross weight
### **Gross Weight vs. Maximum Takeoff Weight (MTOW) for Tethered Operations**
When flying the ALTA X tethered, understanding the difference between Gross Weight and Maximum Takeoff Weight (MTOW) is essential.
* **Gross Weight** – The total weight of the aircraft, including the attached flying Tether Fiber Cable.
* **MTOW** – The maximum allowable weight for safe aircraft operation, set at **34.8 kg (76.8 lbs)** by Freefly Systems.
To ensure safe and efficient performance, keep the aircraft’s Gross Weight at or below the MTOW limit.
For higher-altitude tethered flights, reduce the takeoff weight to as low as **30.4 kg (67 lbs)**. This adjustment compensates for the additional weight of the tether cable as altitude increases. As the aircraft ascends, more of the tether cable is lifted, contributing to the Gross Weight.
Refer to the performance graphs in this guide for detailed insights on how weight adjustments impact flight performance.
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### Optimizing Power Management and Delivery Capacity
The EON800 is rated for up to 95A continuous power delivery. If the current exceeds **95 Amps**, the system will trigger an LCD warning message and an audible alert to notify the operator. The system is capable of outputting slightly more current than the continuous rating for short bursts.
Aircraft power consumption varies based on several factors, including:
* **Takeoff weight**
* **Tether weight**
* **Wind drag**
* **Altitude above sea level**
* **Payload power requirements**
Keep in mind that while certain payloads may be manageable in calm, low-altitude conditions, the same payload may be impractical at higher altitudes or in stronger winds due to increased power demands.
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### Managing Power Limits and Battery Backup During Flight
When the aircraft exceeds the power systems capacity, it safeguards itself by limiting the power. This extra power then comes from the backup batteries, causing them to slowly lose power. The system alerts you, allowing you to either fly lower to use less power or land the drone and lighten the payload.\
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If the aircraft draws more power than the power system can provide, the current will be limited to protect the power system from damage. Excess power will be drawn from the backup batteries, which will cause them to slowly discharge. The system will alert the operator, and the operator can reduce altitude to reduce the power consumption, or land the drone and lighten the payload.
### Heavy-lift Drone Integration
This guide has highlighted how the EON800 tether system works specifically with the Freefly Systems ALTA X. It's worth noting that the EON800 tether system can potentially integrate with other UAVs using a 12-cell lithium battery setup, as long as their power draw aligns with the limits of the EON800 System.
If you're considering integrating the EON800 with different aircraft, please reach out to us for more information. Our team is ready to discuss your unique application and requirements.
Technical Integration Contact:
## EON800 Tether System Specifications
### Tether Ground Station (TGS)
| Dimensions (Including covers) | 560W 400D 250H (mm) |
| ----------------------------- | --------------------------------------------------------------------------------------------------------------- |
| Weight | 16.7kg |
| Input | 200-250VAC, 47-63Hz, 30A Max |
| Output | 800V DC 7.5A Max |
| Power Connector (AC Input) | powerCON NAC3MP-HC |
| Connectivity |
Ethernet Port for Mavlink networking
SD Card Slot for Logging
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| User Interface |
Colour Display with three button interface
Large Red Missile Style Switch for High Voltage Control
|
| Display | 2.8” IPS TFT LCD, 350cd/m2 |
### Air Power Unit (APU) for Alta X
| Dimensions (In Travel Case) | 560W 430D 210H (mm) |
| ------------------------------------ | ------------------------------------------------------------------------------------------------------------------------------- |
| Dimensions (Installed on the Alta X) | 450W 300D 135H (mm) |
| Weight (Installed on the Alta X) | 2.85kg |
| Weight (Including Travel Case) | 8.25kg |
| Input | 800V DC |
| Output | 46-50V DC 95A Continuous |
| Power Connector (DC Output) | 3x Amass XT90 (recessed) – Patch Cables supplied to reach Aircraft |
| Power Connector (Battery Input) | 2x Amass XT90 Panel Mounted, 2x JST-XH 6s balance ports |
| Fiber connector (External) | LC Simplex Fiber Connector |
| Connectivity |
Fiber Optic for communication to TGS
Serial to flight controller via JST-GH 6 Pin
CAN-BUS for Integrated BMS
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| Mounting | Quick Release Push Pins to Alta X Battery Tray |
### Tether Fiber Cable
| Dimensions | 400W 500H 300D (mm) |
| --------------------- | ---------------------------------- |
| Standard Cable Length | Up to 150m (For flight up to 120m) |
| Weight (Cable, per m) | 36 g per meter (±3 grams) |
| Conductors | 18AWG – Rated for 1000V DC |
| Fibers | 8x Singlemode LC Simplex |
| Fiber Speed | Up to 100 Gbps per core |
