Bluetooth Vario

In case your phone isn't equipped with a barometer, you can connect theFlightVario to external sensors or paragliding variometers via:

  • Bluetooth Low Energy (Bluetooth LE)

  • Bluetooth Classic (Bluetooth)

theFlightVario app is continuously tested against:

and FlyNet varios using Bluetooth classic.

Details about supported protocols can be found at the end of the page.



different bluetooth and usb variometer
some bluetooth and usb variometer

Bluetooth LE - tested against xctracer vario

This is the preferred way of theFlightVario to connect via bluetooth. It features low energy consumption and minimum delay in transmitting data. To connect via Bluetooth LE:

  • turn on the external bluetooth vario,

  • tap the Bluetooth menu to scan for devices,

  • select your bluetooth vario from the list

and it should immediately connect.

If the phone's bluetooth is not turned on or the vario has not been connected before, a short dialog will appear, asking for permissions. The name of the connected device will be visible in small letters right above the climb rate field.

Once connected wait a little since some Bluetooth LE varios don't start sending data right away but wait for a GPS fix or other initialization routines. Often they make some special beep to indicate they are ready.

The picture carousel shows the steps for connecting an xctracer vario.

opening the bluetooth menu in theFlightVario smartphone vario to connect bluetooth varioselecting a bluetooth vario from a listblueFlyVario connected to theFlightVario via bluetoothxctracer connected to the flightVario via bluetooth

Bluetooth - tested against blueFlyVario

This is the way to connect if classic bluetooth or dual mode bluetooth is available. Higher energy consumption and slightly more delay than Bluetooth LE but still more than sufficient. Connecting via bluetooth classic works the same as before :

  • turn on your external bluetooth vario,

  • scan for your bluetooth vario by selecting the Bluetooth menu,

  • select your vario from the list

and the connection will be established immediately.

Wait a little since some bluetooth varios don't start sending data right away.

The name of the connected device will be visible in small letters right above the climb rate field. Also, the phone will ask for bluetooth permissions if the vario has not been connected before.

For the blueFlyVario we recommend to put the outputMode to BOM 1 (see manual)


USB - tested against SkyBean2 / xctracer / blueFlyVario

A connection via USB is the way to go if bluetooth is not available:

  • turn on external usb vario,

  • turn on theFlightVario,

  • connect both

and it should immediately ask for permission to connect. Once connected, again wait a little for another dialogue asking you to use the device. As with bluetooth, the name of the connected device will be shown right above the climb rate indicator.

Frequently Asked Questions

Which protocol should I choose for my external vario?

Most of the external variometer talk LK8EX1 and this is fine. If your vario can talk LXWPW to include wind information (e. g. xctracer) go with LXWPW. _PRS should be the last option since this is transmitting raw pressure values and introduces unnecessary complexity. In case you fly with a blueFlyVario you can easily change the standard _PRS setting to LK8EX1 using the blueFly configuration tool when setting the outputMode to BOM 1 (see manual). In case you need to stick to _PRS, you can try calibrating in order to enhance these readings.


How do I check which protocol my bluetooth vario is using?

theFlightVario won't show this information. If you want to find out what protocol is used by your vario, check out the Serial Bluetooth Terminal app.


How do I find out which protocol my usb vario is using?

theFlightVario won't show this information. If you want to find out what protocol is used by your vario, check out the Serial USB Terminal app.


How do I know whether my vario uses bluetooth classic, dual or low energy?

theFlightVario won't show this information. However, connection attempts will be in order from Bluetooth BLE to DUAL to Classic. theFlightVario will take the fastest option possible. You can use the Serial Bluetooth Terminal app if you want to find out what is sent by your bluetooth vario. This way you can also check at what rate your external device is sending (usually around 100ms).


What happens if bluetooth is disconnected during flight?

theFlightVario does not drop the connection and will try to reconnect. If this is not working, the internal barometer (if any) of your smartphone will be used. We never experienced issues. Please get in touch with us if you're experiencing problems.


Are you flying bluetooth or usb?

Unless you need the power source, there is no advantage of using usb over bluetooth. We really like the blueFlyVario and the xctracer vario which is why we explicitly test against them. Yet we fly with smartphones, currently Google Pixel 3a and Pixel 4a. These are awesome phones equipped with a BMP380 barometer and an IMU that supports the instant vario feature of our smartphone vario.


Can theFlightVario act as an external bluetooth vario for my tablet?

We have this on our (somewhat longer) list of future features. If this is relevant for you, get in touch with us.


Supported protocols and message strings

theFlightVario paragliding variometer supports the known protocols to read, process and display data from external bluetooth varios and usb varios. These protocols are:


  • LK8EX1 (blueFlyVario and others)

  • LXWP0 (xctracer)

  • LXWPW (xctracer)

  • _PRS (FlyNet Varios)


$LK8EX1 Message String

the $lk8ex1 string looks like this:


  • $LK8EX1, pressure, altitude, vario, temperature, battery, *checksum


theFlightVario will take the vario readings provided to display a climb rate and use the pressure readings to calculate the current altitude.

For further information on $lk8ex1 see here.


$LXWP0 Message String

the $lxwp0 string will always be preferred over an $lk8ex1 string and looks like this:


  • $LXWP0, kmh, baroaltitude, vario in m/s, , , , , , heading, windcourse, *checksum


theFlighVario will take the altitude, vario in m/s and the windcourse


$LXWPW Message String

the $lxwpw string will always be preferred over an $lk8ex1 string and encodes the windspeed in the last field of the $lxwp0 string:


  • $LXWP0, kmh, baroaltitude, vario in m/s, , , , , , heading, windcourse, windspeed*checksum


theFlighVario will take the altitude, the climb rate, windcourse and windspeed.


$PFLAU Message String

the $pflau string, as part of the flight and alarm system FLARM contains information to alert pilots of potential collisions, looks like this:


  • $PFLAU, Rx, Tx, Gps, Power, Alarm Level, Relative Bearing, Alarm Type , Relative Vertical, Relative Distance, Id


$PFLAA Message String

the $pflaa string, as part of the flight and alarm system FLARM contains data on other proximate aircrafts and looks like this:


$PFLAA, Alarm Level, Relative North, Relative East, Relative Vertical, IDType, Track, TurnRate, GroundSpeed, ClimbRate, AcftType


For further information on $pflau or FLARM see here or at flarm.com.


Audio Using External Varios

Whether you connect via bluetooth or USB, audio will be generated continuously from theFlightVario's audio engine using the vario in m/s or pressure information from the above mentioned message strings.