4.1.3       Onboard smartphone connected via relay server


This system topology has an onboard smartphone, that connects with the cockpit app via a special stationary relay server, which runs the FlightZoomer Relay Server desktop application.

This solution was the default approach up to version 3. As it is more complex to be installed and operated, Direct Link (see section before) is the recommended topology to operate FlightZoomer 3.

System topology using a relay server:

What is needed?




Airborne Vehicle with ArduPilot flight controller + RC system

For multicopter: Configured and (auto"‘) tuned to properly fly in Loiter mode

ArduCopter 3.3 or higher


For planes: Configured and (auto-) tuned to properly fly in Cruise mode. Altitudes should stay within +/- 3...5m

Arduplane 3.7 or higher


Bluetooth transceiver

Bluetooth to serial transceiver,
e.g. HC-06



Device to run
the Sensorics-app

Windows Phone handset to run the FlightZoomer Sensorics-app

Windows Phone 8.1 or higher (including all Windows 10 Mobile)


Computer to run
the Relay Server-application

Stationary Windows PC with Internet access.

Windows 7 or higher


Tethering hotspot

Any mobile handset, that can provide internet access via a WiFi hotspot.



Computer to run
the Cockpit-app

The Cockpit-app is a Windows Store app, that runs on any Windows 10 Tablet, Notebook or Desktop computer. Mid- to upper-class performance is preferred.

Mobile is not supported (as the screen would
be too small)


HD Camera

The companion app can control an HD onboard camera from Sony.

Sony Camera
Remote API


FPV camera + receiver + UVC video capture

Any FPV camera and FPV radio transmission product, that can feed its output via a Video-S-to-UVC capture device into the cockpit device



Microsoft Surface Dial

The FlightZoomer autopilot optionally can be controlled with the Microsoft Surface radial controller




Using the relay server offers the following advantages:

No cloud dependency, the user has the responsibility (and authority) over the communication bus from end to end.

Unlimited range due to cellular network connectivity between the cockpit app and the companion app.

Onboard computing capabilities, that offer enhanced safety (FlightZoomer autopilot modes are continued even if air-to-ground connectivity is impaired).

The possibility to use the camera of the onboard smartphone to shoot photo series or video footage.


The following restrictions apply:

Larger hardware footprint compared with the Direct Link approach (see section before).

Increased installation and operation complexity as the relay server needs to be maintained by the user. Router configurations are required for port forwarding.

Cellular network coverage is needed at the location where the aircraft is flying, and an internet connection is needed where the Cockpit-app runs (which in a typical setup on the field requires a tethering hotspot which means cellular coverage as well)

For the cellular network endpoints mobile phone contracts are needed (typically 2 are required).

The nature of cellular networks means, that short time communication disruptions can happen at any time and that fail-safe considerations are crucial.

Somewhat restrictive hardware requirements. The companion app runs only on Windows 10 mobile. You can get suitable smartphones for much less than the usual radio telemetry products, but the user needs to consider this.