If you fly with a variometer — and most paraglider pilots do — you've probably wondered why it can tell you exactly how fast you're climbing or sinking, but gives you zero warning before a wing collapse. The reason comes down to what a vario actually measures, and what it doesn't.
What Your Vario Measures
A variometer measures barometric pressure changes over time. As you climb, the ambient air pressure decreases; as you sink, it increases. The vario converts this pressure change into a vertical speed reading and translates it into audio tones — the familiar beeping that tells you when you've found a thermal.
Modern varios are remarkably precise. Using complementary filters that fuse barometric altitude with accelerometer data, they can detect climb rates with a resolution of around 0.1 m/s and a response time under half a second. For thermal flying and cross-country navigation, this is exactly what you need.
But here's the fundamental limitation: your vario measures the air around your instrument. It tells you about the airmass you're flying through. It tells you nothing about what's happening inside your wing.
The Physics Gap
Wing collapses are caused by a localised loss of internal canopy pressure. This happens when the angle of attack on part of the wing drops below a critical threshold — usually because of wind shear, rotor turbulence, or an abrupt thermal boundary. The air stops entering the leading edge on the affected side, the cells deflate, and the fabric folds.
The important point is that this is a local, asymmetric event. It happens on one side of the wing before (and sometimes without) affecting the other side. Your vario, sitting in the instrument pod at your chest, measures the bulk atmospheric pressure at a single point. It cannot distinguish between "the whole airmass is sinking" and "the left side of my wing is about to fold."
Can GPS or Accelerometers Fill the Gap?
Modern flight instruments combine GPS position, barometric altitude, and inertial measurement (accelerometer + gyroscope). Together, these sensors can detect the consequences of a collapse — the sudden altitude loss, the asymmetric loading, the rotation. But by the time these sensors register the event, the collapse has already happened. They detect the result, not the cause.
There's a second problem: normal flying produces similar sensor signatures. A sharp thermal entry, an aggressive weight-shift turn, or moderate turbulence can all produce acceleration spikes and altitude changes that overlap with the signature of a collapse. Without knowing what the wing itself is doing, any prediction system based purely on external sensors will produce too many false alarms to be useful.
Measuring What Matters: Internal Wing Pressure
This is the insight that led to ParaBaro. If collapses are caused by internal pressure loss, the most direct way to predict them is to measure internal pressure directly.
ParaBaro uses differential pressure sensors positioned inside the canopy — measuring the pressure difference between the interior of the wing cells and the ambient air. By placing sensors on both the left and right sides, we can detect the asymmetric pressure signature that precedes a collapse.
The physics is straightforward. When a thermal boundary crosses the wing, the side that enters the thermal first experiences an increase in angle of attack and internal pressure, while the other side may see a decrease. This creates a pressure differential — a measurable gradient across the wingspan. Our sensor data shows this gradient appearing 0.5 to 1.5 seconds before any visible deformation of the wing.
Two-Stage Detection
ParaBaro uses a two-stage approach that combines the strengths of both technologies:
Stage 1 — Spatial pressure forecast: The differential pressure sensors and IMU detect asymmetric pressure changes and rotational acceleration in real time. This is the fast predictor — it fires within 200 milliseconds and provides the early warning.
Stage 2 — Bulk confirmation: The barometric altimeter and GPS confirm whether the detected event is developing into a genuine collapse or was a transient fluctuation. This fires 1–3 seconds later and reduces false positives.
The result is a system that can alert a pilot to a developing collapse before it becomes visible, while keeping false alarm rates low enough to be trusted in real flying conditions.
What This Means in Practice
We're not suggesting you replace your vario. It remains the essential tool for thermal flying and navigation. What we're building is a complementary instrument — one that fills the gap your vario can't cover.
Think of it this way: your vario tells you where you are in the air. ParaBaro tells you what your wing is doing in that air. Together, they give you a more complete picture of your flight than any single instrument can provide.
The technology is currently in beta testing with 50 pilots. Every hour of flight data they upload helps train the machine learning models that make collapse prediction more accurate. If you're interested in being part of this, visit the beta programme page.