4.1.2       Onboard smartphone connected via Direct Link


This system topology has an onboard smartphone, that directly connects with the Cockpit-app via cellular networks.

The Direct Link is realized using a commercial realtime messaging platform (Ably). The in-built hand-shaking mechanism allows to establish the connection simply by entering a six-digit token in the cockpit app, which is generated and displayed on the companion app.


System topology using Direct Link:

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 Companion-app

Windows 10 Mobile handset to run the FlightZoomer Companion-app

Version 1607 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 Direct Link offers the following advantages:

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.

Multi Cockpit-app setup is possible.

Highly reduced hardware footprint and complexity compared with the legacy setup using the relay server (see next section).

Slightly lower latency of the communication bus.


The following restrictions apply:

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)

The cellular endpoints need mobile phone contracts (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.

As a commercial provider is used for the realtime messaging, a small time-based fee needs to be paid. The DirectLink fees are $0.99 for 10minutes.

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