Flying for hours at a time---whether you're soaring a powered sailplane, gliding a high‑performance paraglider, or piloting an autonomous UAV---demands a deep understanding of lift and sink. The variometer, the instrument that tells you whether you're gaining or losing altitude, becomes the pilot's most trusted co‑pilot. Yet many aviators treat it as a simple "up‑or‑down" gauge, missing out on the subtleties that can make the difference between a successful cross‑country marathon and an early landing.
Below is a practical guide to extracting the maximum benefit from your variometer during long‑duration flights. It covers the science, the settings, and the techniques that let you read the sky, conserve energy, and stay in lift for as long as possible.
Understand What a Variometer Is Measuring
| Parameter | What It Represents | Why It Matters for Long Flights |
|---|---|---|
| Vertical speed (m/s or ft/min) | The rate of altitude change relative to the surrounding air mass. | Directly tells you whether you're in lift (positive) or sink (negative). |
| Total Energy (TE) or Total Energy Compensation (TEC) | Combination of altitude change and kinetic energy (airspeed). | Prevents false readings when you speed up or slow down---critical for smooth energy management. |
| Averaging time (e.g., 2 s, 5 s, 10 s) | How quickly the instrument smooths raw data. | Short averaging reacts faster but is noisy; longer averaging filters turbulence but may miss thin lift layers. |
Key takeaway : A variometer that reports total energy and offers configurable averaging gives you the most reliable picture of the atmosphere when you're trying to stay aloft for hours.
Set Up the Instrument Before Take‑off
2.1 Choose the Right Averaging Interval
| Flight Phase | Recommended Averaging | Reason |
|---|---|---|
| Launch / climb | 2 s -- 3 s | Quick response helps you locate core lift. |
| Cruise between thermals | 5 s -- 8 s | Dampens gust‑induced "flicker," letting you gauge sustained lift. |
| Final glide / approach | 1 s -- 2 s | Immediate feedback for precise altitude control. |
If your variometer allows dynamic averaging (auto‑adjusting based on vertical speed magnitude), enable it---this gives you the best of both worlds.
2.2 Calibrate the Barometric Sensor
A barometric variometer drifts with temperature and pressure changes. Perform a ground calibration at the launch site:
- Turn the unit on and let it settle for at least 2 minutes.
- Set the reference altitude to the known field elevation.
- If the device has a temperature compensation knob, align it with the ambient temperature.
Re‑calibrate every 30 minutes in a long flight if you notice a systematic bias (e.g., the needle slowly creeping upward in still air).
2.3 Enable Total Energy Compensation
For powered sailplanes and paragliders, enable TEC. In many modern units, this is a simple toggle (often labeled TE or E‑comp). If you fly a UAV with a pitot‑static system, make sure the software merges airspeed and altitude changes correctly.
Interpreting the Readout in Real Time
3.1 Distinguish Between True Lift and Speed‑Induced Variations
- True lift: A steady positive reading that persists for at least 5 seconds with a 5‑second averaging interval.
- Speed‑induced lift/sink : Short spikes that disappear when you level the throttle or adjust pitch.
If the variometer shows a rapid surge of +3 m/s followed by a quick drop, you're likely reacting to a gust rather than a thermal core.
3.2 Use the "Climb Rate Trend" to Predict Lift Duration
Many variometers display a small bar graph or trend line. A steady upward trend (e.g., 0.8 m/s → 1.2 m/s over 30 seconds) hints that you're entering a stronger part of a thermal. Conversely, a decaying trend suggests the lift is weakening, and it may be time to transition to the next source.
3.3 Monitor Energy Height in TE Mode
Energy height is the altitude you would have if you were flying at a standard reference speed (often 55 km/h for sailplanes). A rising energy height while your actual altitude stays flat signals that you're gaining speed (perhaps from a headwind) and can afford to slow down to convert kinetic energy into altitude later.
Practical Techniques for Prolonged Soaring
4.1 Adopt a "Lift‑Centric" Flight Path
- Scan the sky : Use the variometer's visual and auditory cues. A faint, continuous tone indicates light lift; a strong, steady beep signals core lift.
- Circle on the lift : Keep the turn radius tight enough to stay in the lift column but wide enough to avoid stall. Adjust bank angle based on glide ratio---most pilots use 30°--45°.
- Leave early enough : When the climb rate drops below a pre‑set threshold (e.g., 0.5 m/s for a sailplane, 1 m/s for a paraglider), start the transition to the next lift. Hysteresis prevents premature exits due to temporary dip.
4.2 Energy Management During Cruise
- Slow‑flight cruise : Reduce airspeed to the glide polar's minimum sink speed (often 70--80 km/h for sailplanes). This maximizes the distance you can travel per unit of altitude lost.
- Speed‑to‑fly in headwinds : Increase speed slightly above the minimum sink to offset wind component; the variometer's TE reading will show a positive energy trend if you're correct.
- Use "speed rings" : Some variometers let you set a target vertical speed (e.g., +0.5 m/s). The instrument will advise you to adjust speed to maintain that target---an excellent way to stay in weak lift without over‑circling.
4.3 "Thermal Hopping" vs. "Long‑Duration Soaring"
- Thermal hopping (common in short‑duration cross‑country) involves frequent climbs and short glides.
- Long‑duration soaring favours steady, gentle climbs and long glides with minimal energy waste.
Adjust your variometer settings accordingly: for hopping, you want a short averaging period to react quickly; for marathon flights, lengthen averaging to keep the needle stable and avoid jitter‑driven steering corrections.
Auditory Cues -- The Unsung Hero
Even when you're focused on navigation or spotting terrain, your ears can help you stay in lift:
| Audio Mode | Description | When to Use |
|---|---|---|
| Continuous tone | Pitch proportional to climb rate (higher pitch = stronger lift). | Cruise between thermals; low‑volume headphones keep the tone audible without masking external sounds. |
| Beep‑burst | Short beeps for sink, longer beeps for lift. | During busy maneuvers where visual focus is elsewhere. |
| Silence | No tone indicates near‑zero vertical speed. | Use as a "baseline" to gauge the effectiveness of any adjustments. |
Calibrate the audio sensitivity to avoid false alarms from turbulence; most units let you set a dead‑zone (e.g., ±0.2 m/s) below which no tone is generated.
Common Pitfalls & How to Avoid Them
Checklist for a Long‑Duration Flight
| Item | Action |
|---|---|
| Variometer Settings | Averaging: 5 s (cruise); TEC: ON; Audio: Continuous pitch mode. |
| Barometric Calibration | Set reference altitude on the ground; note ambient temperature. |
| Pre‑flight Brief | Identify expected lift sources (thermal hotspots, ridge line, sea‑breeze front). |
| During Flight | • Scan variometer continuously. • Adjust bank and speed based on TE trend. • Exit lift when climb < threshold for >10 s. |
| Mid‑flight Re‑calibration | If altitude reference drifts >30 m, pause (or dip) and reset. |
| Post‑flight Review | Export variometer log, overlay with GPS track, note any "false lifts" that misled you. |
Final Thoughts
A variometer is more than a needle; it's a dynamic map of the invisible air currents that sustain your flight. By mastering its settings, interpreting its signals correctly, and integrating auditory cues into your situational awareness, you turn a simple instrument into a strategic ally.
For long‑duration flights, the goal isn't just to "stay up" but to stay efficient ---to extract every ounce of lift while minimizing the energy you waste in turns, speed changes, and false alarms. Keep the variometer tuned, listen to its voice, and let the sky's subtle gradients guide you to the next horizon. Happy soaring!