Frequently Asked Questions

The following sections handle some common questions found in paragliding. We hope to answer these as objective as possible. Also, a good amount is spent clarifying the differences and expectations of using a smartphone as a variometer for paragliding. Needless to say, a smartphone is not designed and built with the requirements of a vario in mind firsthand. The pilot is responsible for choosing the appropriate equipment.

Contact us if you want to add or have improvements that you feel should be integrated.

When and where to use a variometer

Is this a bubble, already a steady thermal? Did I just fall out of the thermal? Did I reach an enhanced climb zone within this thermal? What is this pull, is it just me feeling this or is it also indicated by the flight instrument, the vario that I’m using?

Often you hear things like:

"... as long as you are just learning to fly, a vario is not that important..."

Well, we think this is only half the truth. What is true, in the beginning you might or better simply cannot know which variometer is best. However you should go with a vario as early as possible. As soon as you fly it is important to consciously sense the movements of your wing and harness (up / down / pull / push) together with the output of the vario.

For your first flights it is not necessary to have a big display, information about airspaces or the exact speed over ground. Even the exact climbing rate is not that important and or how fast you are flying over ground. Most important is a vario tone that reflects the rate of climbing. It should get higher and beep more often if the climbing gets bigger and vice versa.

So, to learn fast and have long flights soon we recommend two things:

  • get a vario as soon as possible (here are some of our test varios)

  • get a cockpit as soon as possible, to have in reach what is essential to you. Your phone should be in reach, your vario, small things to eat and drink, a power bank might be a good idea. Also a long, thin line is a valid item in case you ever need to get rescued. (here is cockpit with all of our varios)

In case you are just soaring along a small ridge thinking, simply following the relief closely might be more relevant than flying with a vario... Even while soaring, an instant vario can be extremely helpful to carefully select your turning points meaning the point where you turn your glider to get the most out of the local lift. Not getting that sweet spot makes you loose altitude twice.

Which variometer to choose?

In the beginning you might not know which variometer is best for your paragliding. Don’t just throw all your money into the very first vario. It will be very disappointing finding out you spend a lot of money on a flight instrument but your are actually more comfortable with another solution like a small bluetooth vario, a smartphone vario or a combination of both once you mastered your first flights.

Also, don’t invest too much money or time into (very) old variometers. These might be ok during flight but quite uncomfortable on the ground to use or connect to a computer (which will be your only way to reasonably analyze your flights). They might need special power plugs and or cables or drivers you might need to install. Using these as a backup vario or flight logger however will be fine.

So, while it is not possible to tell which flight equipment resembles the best variometer for paragliding, for different types of pilots different solutions exist.

(Note: This might be a biased opinion, but with smartphones nowadays having gyroscopes, accelerometers and barometers: Unless you are not going professional, your smartphone has a display, it logs the GPS coordinates of your flight, it already has an antenna in case live tracking is relevant, your flights are backed up with the cloud, you can analyze your flight directly on the phone and of course you carry it with you anyway.

We have never seen a pilot forget his smartphone. But we have seen many pilots that forgot their vario because they charged it and left it unintentionally at home or in the apartment or in the bus.

So in case you are going for a new smartphone you might want to consider getting a smartphone with instant vario capabilities to try this out.)

Where to attach the smartphone

Once using the smartphone as a vario the next question is where to attach it. Theoretically, once could strap it to the risers, put it into an arm wrist, attach to the leg or actually the best way and practiced by most pilots: Attach to the cockpit in front of you. This way you can also connect it to a powerbank or if relevant attach an external vario via usb or bluetooth.

Can you fly without a vario?

Of course you can and it is fun and good practice to sharpen your senses for everything around your wing and harness. But after all your human senses are limited. Being human apart from visual and acoustic information you can sense changes in gravity which is why you can feel the initial lift when entering a thermal, the drag when you’re sucked into a thermal directly ahead or to the side of you but also being pushed away from a thermal or simply sliding down on the lee side of a thermal.

However being inside a thermal with a constant climb rate it is impossible to tell how fast you are moving up without additional visual clues. Naturally the higher you get the less visual clues you have.

Better than training your senses without a vario, train your senses with a vario so that your (intuitive) judgement meets the objectivity of a flight instrument.

This is also the reason why good pilots can fly reasonably good without vario! All of their senses, visual, acoustic as well as regarding gravity have been aligned over time with the objectivity of a vario. On top of that, they either know the place or have been flying in comparable areas before having an implicit explanation of why the air is rising at certain spots and sinking at others. They either fly with an explicit understanding of the terrain and weather or intuitive (implicit understanding). They watch out for leaves whistling at the ridge, look for birds, dust moving into certain directions or trigger points for thermals, moving or fixed.

Using a phone as variometer

Now and then you can hear pilots talking about whether it is possible to use their phone as a standalone variometer for paragliding?

It depends! But lets break it down a little:

  • What is it that you expect from a flight instrument while paragliding.?

  • What are the key features of a vario for paragliding?

  • And how does a smartphone used as vario relates to these criteria?

Displaying Information

Obviously a smartphone display is not engineered for paragliding needs! But, you won't stare at the display all the time. You will check your altitude now and then, direction of flight, direction of wind and distances. Of course, the climb rate, you need to know that but 90 percent of the time you will listen to the vario tone in order to center the thermal.

If you are flying in areas with airspace restrictions, you should have prepared your flight before. So it is not like you are opening up your screen and look up all the information while flying. It is more about an indication whether you are close by or entering an (expected) airspace. For this, we think the visual indication is sufficient not to forget that this indication is accompanied with a warning sound or some kind of alert tone.

So, not having an optimal display, the upside is: Using your smartphone as a vario, it already comes with a screen!

Vario Tone

90 percent of your time flying you will be focusing on the audio feedback indicating an increase or decrease of the climb rate. So, whatever vario you are using it would be nice if the tone can adequately represent the (instant) changes in climb rate.

This means the frequency ot the tone, beep cycles, durations and duty times need to be able to change instantly and simultaneously to provide continuous information on your lift within a thermal. It is also worth mentioning that different flight conditions might require different sound profiles. Think of juicy spring thermals as opposed to weak flatland thermals.

Easier said: An Instant Vario should go along with an Instant Tone. For a smartphone it is easy to provide a low latency instant vario tone. The xc vario itself can be configured with different sound profiles using xctracer or leGPSBip config files and features a low latency due to optimized audio processing and synthesizing.

The Vario - Calculating Climb Rates

Ok, this one is often discussed first and with varying depths and arguments ranging from own experience up to pointing out by example why the smartphone sensors cannot be as good in providing a climb rate as some flight instrument sensor. These discussions are actually good as they show that it is a good idea to again break it down a little.

Of course a smartphone is not built with the requirements of a vario in mind. Yet, some of them come equipped with the type of sensors also found in varios and in the end it is up to the pilot to decide.

So what are the key sensors in a vario and what does it take to calculate climb rates?

Barometer: the barometer measures the pressure at certain times. Modern mid range smartphones can do this at a rate of 25ms or 40 times per seconds. Using this barometer, the vertical movement based on pressure differences at different altitudes can be calculated (how a vario works).

As for any sensor the question is how do you know how good it is. And this leads to accuracy and precision of a sensor. Let's have a look at these terms using the barometer.

Accuracy would mean that if the true pressure is 1013.25hpa, the barometer would report exactly these 1013.25hpa on average. Why on average, you might ask yourself. This is simply due to natural random errors happening when measuring continuous quantities. Unless you cannot count it exactly (like an amount of apples) you will always be a little off the accurate or true value. So you might get a

  • 1013.2475 hpa as a first,

  • 1013.2525 hpa as a second,

  • 1013.2485 hpa as a third and

1013.2515 hpa as a fourth measurement.

So, is this accurate now? Generally speaking, yes! Taking the average of these values, you land at 1013.25hpa. Considering you can take 40 readings each second, you can be quite sure to have enough readings to average out at the true value.

So what are these little deviations then? These little deviations can be seen as a standard error imposed from any measurement device (in this case this is the sensor reporting back). This standard error is also called precision. The more precise your barometer, the more close to the average each single measurement will be. Precision gives a clue as to what deviations can be expected and how likely a deviation would be.

Is accuracy important then? No, accuracy is not that important. At least not for calculating the climb rate (the vertical speed in the air) for a smartphone vario. If all pressure readings from the barometer inside your smartphone are off by a constant offset the differences between the readings will be the same still. In other words 100m - 90m = (100m + 10m) - (90m + 10m) This offset is also called bias and won't affect the calculation of the climb rate. For instance, a natural offset being introduced each day is the pressure of the airmass itself (low/high pressure).

Is precision important then? Yes, precision is important. Together with the rate at what the pressure measurements from the barometer are reported it will define the possible resolution of your smartphone vario.

Wait, wait resolution? Is that the magic 0.1 meter per second climb rate some pilots argue can only be reported with professional vario. Yes. And No, it can be done with smartphone barometer too. It is just that depending on the rate of readings it will take longer or shorter to detect such a pressure difference correctly.

Now, if accuracy is not that important. How do you know at which altitude you are flying? Sad but true, a vario will never know this accurate by barometric pressure readings alone unless it is calibrated on that very date and time on a location with know altitude. The altitude with respect to mean sea level is pulled from GPS - NMEA sentence information such as the $GPGGA sentence.

Finally: Professional devices do have professional barometer inside. These are very precise and can provide an extremely high rate of barometric measurements which in turn can be used to boost precision even further. Will these ever happen to be within a smartphone? Probably not

So. how much precision is needed? We think, this question is most interesting.

Inertial Measurement Unit: The IMU contains further sensors such as accelerometer and gyroscope in one chip and enables a smartphone to perform real time motion detection. These can be used to enhance the classical vario and calculation of climb rates based on barometric readings alone to provide an instant vario. Check theses details on how an instant vario works.

Current Location, Bearing And Speed Over Ground

Current Location, bearing, speed over ground and mean sea level altitude. All of this information relevant for paragliding is stripped from Global Positioning System (GPS) or nowadays more correctly speaking of Global Navigation Satellite Systems (GNSS) information. Even the wind direction will be calculated with the help of GPS.

Fears are that GPS/GNSS in a smartphone is not precise or accurate enough. Good thing, a smartphone can tell you how big the expected variation is at your current position. Another good thing, GPS itself is not alone nowadays. There is more than NAVSTAR GPS (USA). We also have GLONASS (Russia) , Galileo (European Union) and BeiDou/COMPASS (China) satellites to get the required information from.

How many different satellites your smartphone is using to determine the relevant information, simply depends on the GNSS chip itself. You can check this with GPSTest app if you are interested. For instance on a Pixel 4a we have around 30 satellites being reported from the 4 different GNSS.

Check this nice article on Mean Sea Level, GPS and the Geoid if you want to dig deeper.

Current Heading

Your heading will be different to your bearing. While the bearing is the direction your are flying to calculated from the GPS locations, your heading is the direction your are looking to. The heading can be calculated from the magnetometer. The geomagnetic field declination has to be taken into account for this.

Battery Run Time

Standalone variometers are designed specifically for paragliding. So the battery should last more than a full paragliding day. This is seldom the case with smartphones. Being realistic you can expect up to 5 hours depending on how intensively the display is being used. Battery Packs do exist :-).

Charging and charging time is also a criteria. Using flight instruments you might need to carry extra cables and plugs to keep it operational. Although this is less relevant with new standalone variometers it might be worth mentioning when using legacy variometers.

Live Tracking

So what about live tracking when paragliding? Here we have to differentiate between two purposes.

One purpose is to stay safe while flying and exploring especially new routes and terrain that is beyond the boundaries of mobile service or cell phone coverage. This is the domain of GPS satellite messengers or tracking devices.

Another purpose is to update your position to websites where other pilots can explore your history fo flights and current flights. For this to happen, you must have a mobile connection.

Setting Altitude with QNH / QFE

We made it easier to fetch Metar information for a specific ICAO code. You can now fetch and set QNH pressure from weather stations on the main flight screen as shown in the screenshots below.

Upon starting the vario, markers for the ICAO stations will appear on the map. Click onto a marker to have the Metar fetched with QNH inside. In this case Q1018 meaning 1018hpa being more than reference mean sea level of 1013.25hpa.

QNH of 1018hpa at EDVE

The QNH altitude is currently at 54 meters. Touch and hold QNH altitude field and a QNH pressure selection will appear. Setting to 1018 the QNH altitude changes to 95 meters.

Setting a QNH pressure of 1018hpa

Setting to 1018hpa the QNH altitude changes to 95 meters.

You can check with the mean sea level altitude fetched from GNSS and see that it is only slightly off. Pressure sensor of the Pixel 6 used here seems to be well calibrated and GNSS mean sea level altitude quite precisely. This of course depends on the number of satellites found and thus how well the region is covered.

Comparing QNH altitude to mean sea level from GNSS NMEA sentences