The XC Variometer
The XC-Vario is a fully-fledged standalone variometer with a modern display that is readable in sunlight, has a built-in speaker, and also transmits the data from all sensors (altitude, vario, speed, temperature, and position) and, if applicable, FLARM via Bluetooth, Wi-Fi, or serial connection in various formats to the XCSoar cross-country flight software. A dedicated driver, “XCVario,” was developed, supplied to the XCSoar project, and has been available since 2021. The XCVario-23 series has two serial interfaces, e.g. for a serial connection to an OpenVario, increased audio amplifier power with 2 watts, a CAN bus for the second device and the CAN magnetic sensor, as well as an internal direction and attitude sensor (AHRS). The delivery of data for the display of the attitude sensor as an artificial horizon in the navigation system and in the XCVARIO itself is offered as an additional software option. Even without the software option, the attitude sensor supplements the load factor in the calculation model for precise target flight, for more accurate net vario or for stall warning under accelerated conditions, and also supplies the data to XCSoar for the horizon display. The XCVario thus always displays the ‘real’ climb, regardless of the slip angle, mosquitoes, or flap position, and optimally supports the pilot in finding the best flap position, bank angle, etc. for optimal climb. No adjustment is therefore necessary. The variometer function is thus also insensitive to accidental or intentional interference with GPS signals, as has unfortunately been observed in recent days.
In terms of sensor technology, particular care was taken to filter the data. A predictive Kalman filter optimally stabilizes the vario display without the usual delay of a few seconds that conventional low-pass filters entail. Furthermore, in addition to the ballast, the load factor is also taken into account when calculating the polar sink rate.
 
 The display of information on the XCVario can be configured. In addition to the previous “Airliner” style, the current software also allows for a “Retro” style, as shown on the start page. The new style implements a conventional and easy-to-read pointer display, which most pilots are familiar with and accustomed to from mechanical round instruments. Here, too, the display area is configurable, as are the units for vario, altitude, and speed according to international standards such as knots, feet, flight level, and more.
What makes it special is that no additional special OpenVario hardware is required; XC-Soar runs on almost any Android device. Most Android devices already have an internal GPS, but alternatively, the GPS data for XCSoar can also be obtained via FLARM, and this combination gives you a full-fledged ‘OpenVario’ with a moving map, a full-fledged route and final approach calculator, a functioning wind calculation, as well as target speed and many other features and functions that would not be possible without this data. Data exchange of settings for the Mac Cready value, bugs, and ballast from XCSoar to the vario or from the vario to XCSoar (including QNH) is also possible with the proprietary driver.
In conjunction with FLARM, XC-Soar provides valuable traffic information such as distance, altitude difference, and climb rates of other aircraft. Of course, touchscreen devices can be used for easy operation of XC-Soar. This eliminates the need for cumbersome and complicated joystick remote controls.
The software for this was developed over several years on the open source platform github (https://github.com/iltis42/XCVario/blob/master/README.md) and now has many features and a high level of stability. The same applies to XCSoar, which has matured over many years with thousands of installations on a wide variety of hardware and runs very stably even after many hours of use. For technical details on the software and hardware and their evolution, see the link to GitHub above.
The device comes in an elegant silk matt black anodized aluminum housing. When selecting the electronic components, the focus was consistently on good quality with a long life expectancy. You won't find short-lived electrolytic capacitors, batteries, or LiPo batteries with a limited life expectancy in the harsh temperature range of a cockpit here. The electronics are manufactured in one of the largest factories in the world, fully automated in series of three-digit quantities. The development, integration, and quality testing of the Vario's takes place in Germany, including tests in the air on extended flights of over 850 km. The new hardware can be installed in almost any instrument panel like a standard 57 mm instrument and is offered at an affordable price. For two-seaters, the same affordable hardware can be used in two-seater mode, connected wirelessly via WiFi to the second seat. This eliminates the need for wiring or tubing in the second seat. This means that all functions are available on the second Vario without restriction, just as in the front seat.
The hardware comes with the software pre-programmed, and a growing library of almost 100 polars is already available and can be selected in the setup. An important feature is the software update (OTA = Over The Air) via the device's WiFi interface, which allows the software to be easily updated when installed and paves the way for access to new features, polars, or new requests from users.
Starting with the 2021 series, the additional S2 interface allows for extensions such as a flap sensor, a magnetic sensor, and another serial device (OpenVario). Starting with the 2022 series, a CAN bus will also be supported for extensions such as the CAN magnetic sensor (RS232 thus remains free) or a wired second device in the two-seater.
In addition to crosswind calculation, the magnetic sensor can now also be used to perform a quick live wind calculation during straight flight. The process reacts very quickly, and zigzag flight is not necessary. The deviation of the magnetic sensor is continuously optimized during the process.

ATTENTION XCVARIO Version 23 offers the following improvements:
200 nits brighter screen with anti-glare and anti-fingerprint coating for even better readability in almost all lighting conditions.
Improved, heated INU platform for more accurate acceleration and position values across the entire temperature range.
New, broadband, more powerful integrated speaker.
Translated with DeepL.com (free version)