Schlagwort-Archive: Vario

Variometer 101

Author: Adam Woolley

If you’ve ever watched a glider gracefully manoeuvre through the sky, or you’ve just started your life’s soaring adventure you might wonder how they or we manage to stay aloft for so long without an engine. One of the key tools that we use to help us as glider pilots achieve this beautiful feat, is called a variometer. In this article, I want to describe in simple terms how this clever device works.

Sensitive Rate of Climb Instrument
First off, what exactly is a variometer? Simply put, it’s a special instrument that measures the rate of climb or descent of the glider. Think of it as a helpful assistant for the pilot, indicating whether they are going up, down, or maintaining altitude. Uniquely, the Americans have designed a very clever digital variometer called the ClearNav!

Pressure Sensor
Now, let’s delve into the inner workings of a variometer. At its core, a variometer contains a sensitive pressure sensor. This sensor is designed to detect even the slightest changes in air pressure. As the glider ascends or descends, the surrounding air pressure changes and the variometer picks up on these fluctuations. But how does it translate these pressure changes into useful information for the pilot? Well, the variometer is connected to a display unit in the cockpit. This display typically features a dial or digital readout, that shows the rate of climb or descent in feet per minute (fpm) and typically shows on the instrument as a number 1-10.

When the glider is climbing, the variometer needle or digital display will indicate a positive rate of climb. Conversely, when the glider is descending, the display will show a negative rate of descent. If the glider is maintaining a steady altitude, the display will remain close to zero. A slow rate of climb is 100fpm (indicated as 1), and a strong one is 1000fpm (indicated as 10) – a true elevator in the sky, and super exhilarating when you catch one! Now, you might be wondering how the variometer distinguishes between rising and sinking air currents, which are crucial for us glider pilots seeking to maximise our time in the sky. This is where some clever engineering comes into play.

Audio Variometer
In addition to measuring the overall rate of climb or descent, variometers are often equipped with a feature called an „audio vario,“ which is imperative to both our senses and our safety in the sky. This feature emits a distinctive sound that changes in pitch or frequency depending on the glider’s vertical speed, allowing us to realise whether we are in a lift or sink just by tuning our ears into this distinctive sound.

For example, when the glider is climbing in rising air, the tone will become higher in pitch (a happy tone), alerting the pilot to the presence of lift. Conversely, when the glider encounters sinking air, the tone will become lower in pitch (a depressing tone), signalling the need to adjust course to find a better lift or just less sinking air. By listening to these auditory cues while also monitoring the visual display, glider pilots can effectively navigate through thermals and other atmospheric phenomena to maintain or gain altitude. Overall, the variometer is a vital tool for glider pilots, helping us to gauge their rate of climb or descent and fly through the ever-changing & invisible air currents of the sky. With its simple yet ingenious design, the variometer plays a crucial role in keeping gliders soaring gracefully through the air for hours on end. Source: ‚Adam Woolley on Wings and Wheels‚.

Finding Good Thermals

One thing that is said time & time again is that the greatest improvement in our achieved cross-country speed will come from increasing our average rate of climb, but how can we work towards this? Practice makes perfect, of course. In all reality, once a thermal has been found and centred, most pilots will climb at around the same rate, and most gliders are reasonably similar in performance. So are others doing to improve their speeds or enjoyment of the skies that you might not be? What are they looking for, and what techniques are they using to help find these stronger thermals?

Feel & Hear the Airflow
Using the „feel“ of your glider is probably the greatest factor in successfully finding good climbs. Being familiar with your glider is vital, as is a basic understanding of thermal structure. Fortunately, this understanding does not need to be too technical, put in 20% effort on this & you’ll get an 80% reward – so it is useful to know what a typical airflow pattern around a thermal is likely to be. What does this airflow feel and sound like inside your cockpit? Let this last sentence sink in for a bit, and reread it.

The transition from Sink to Lift
Dead & heavy, that’s the feeling of the sink surrounding a lift area. As you progress closer to the lift, you will pass through the turbulent zone where some strong shear occurs between the sink and the lift. This area will feel bubbly, transitioning from a down indication to what we are looking for, the up part! Shortly after this turbulence, you will feel a strong, smooth surge (quite often, you’ll sense the glider accelerating, and the ASI will show that you are) as you enter the main laminar flow of the thermal core. The cockpit should sound quieter. When you’re in the core, too, you’ll notice that the controls will feel like they are ‚biting‘ the air & working better than usual. This is because the airflow over them is smooth and organised.

These indications will only occur as described if you manage to fly directly into the centre of the thermal! But often, this doesn’t happen, so what is important is to recognise quickly where you are in relation to the good bit by feeling the characteristics of the air you are in. Turn towards the rising wing, but not always. This is so obvious. Hold the stick lightly & keep the vario noise low; it is impossible to hear the airflow around the cockpit when it’s too loud; finally, look up and outside. Look, listen and feeeeeel. This is not easy and takes time and dedication to master, but any effort you put in here will be rewarded.

Moving from Bubbly to Smooth Lift
For example, if the day provides regular six-knot climbs and has flown under a promising fresh cumulus, you are rewarded with an erratic four that feels rather bubbly. The well-in-tune pilot will realise that there is a good climb quite close but that they are currently positioned in the shear layer on the edge of the thermal core. First of all, they will recognise this by carefully paying attention to the feel of the different parcels of air as they circle up, building the picture as to which direction they must move to find the best lift. This may be just a moment of smooth air to centre towards or a section of the turn that is more turbulent to move away from. This is certainly not easy; it takes a very subtle feel and intense concentration. The good news, we can all learn to do it. Other gliders nearby are good measures, don’t be too proud to go over to them if they are going up faster. Use the time to lock in the lesson as to the feelings & sounds you get along the way to – free training. Always look for that smooth, laminar core that gives a big push from below. Happy climbing! Source: ‚Wings & Wheels‚.

Wissen, woher der Wind weht

Vario und momentane Windmessung mittels Sensor-Fusion und digitaler Signal-Verarbeitung. Für den Segelflieger ist es essenziell, zu wissen, wie sich die Luftmasse in seiner Umgebung bewegt. Wie kommen wir zu einer Windinformation im Flugzeug und warum haben wir nicht schon lange eine genaue Echtzeitanzeige des Windes? Genauso wichtig wie die vertikale Bewegung der Luftmasse ist die horizontale Komponente, die wir landläufig als Wind bezeichnen. Insbesondere im Gebirgsflug, beim Hang- und Wellenfliegen, wissen die Piloten die sekundengenaue Windinformation zu schätzen. Aber auch für die Flachlandpiloten ist Windinformation sehr wichtig, um die Thermik zielgerichtet zu finden und zu zentrieren: In Bodennähe weht der Wind zum Aufwind hin, in Wolkennähe vom Aufwind weg (…) Quellen und gesamter Artikel: ‚LXNav / Segelfliegen-Magazin‚.