Live Calibration

The Calibration page (https://rotorlab.app/calibrate, also Calibrate from live test in the app menu) closes the loop between the theoretical model and the real aircraft. It connects to a flight controller with the same link stack as Live Telemetry, captures a steady hover and an optional wide-open-throttle burst, and inverts the model to measure two figures every build otherwise guesses at: the figure of merit and the maximum thrust per motor. Applying the result converts the estimated thrust and thrust-to-weight figures into measured values.

Data is transmitted only to your own RotorLab account, and only when you compute or save.

Prerequisites#

• A saved build to calibrate (see Build library). You can also calibrate against the active defaults.
• The all-up weight at test time. Put the craft on a scale; do not trust the build's paper weight, because the model inverts around the real thrust the rotors are making.
• A telemetry link: USB (Web Serial), a LAN WebSocket bridge, or the cloud relay. Calibration works on the bench or in the field.

The page opens in Quick mode: a single hover, optionally a WOT burst. An Advanced bench wizard mode is also available for multi-point bench runs; this page covers Quick mode.

Step 1: Build and test weight#

Pick the Build from the dropdown and enter All-up weight at test [g] from your scale. The page shows the model's predicted figures for that build (press Refresh to reload them after a change).

Step 2: Connect#

Choose the Firmware (ArduPilot (MAVLink) or Betaflight / INAV (MSP)) and the Connection (USB (Web Serial), Network (WebSocket), or RotorLab Cloud relay), then press Connect. Live tiles show the incoming armed state, throttle, voltage, current, and climb rate so you can confirm the stream before capturing. A hover guide shows your throttle against the predicted hover target and a vertical-rate bar centered on level.

Step 3: Capture#

Set the averaging Window [s] (3 to 30 seconds, default 8), then capture:

Hover capture#

Hold a steady, level hover at the test weight and press Capture hover. The page averages throttle, voltage, and current over the window and checks that the hover was steady. A capture is flagged weak (still usable, but noisier) if the throttle varied by more than 3 percent, the average vertical rate exceeded 0.4 m/s, or the craft was not armed. A steadier hover gives a better calibration.

The physics: in hover the rotors must make thrust equal to weight, so the ideal induced power is fixed by geometry and air density. The real power drawn is voltage times current minus the avionics share on the motor bus, and the ratio of ideal to real is the measured figure of merit. Separately, the hover throttle the autopilot needed tells you how much thrust headroom is left, which yields the max thrust per motor (the page derives both a linear and a square-law bound from it).

WOT capture (optional, bench only)#

Press Capture WOT and hold full throttle for the window. The hover-to-WOT power ratio gives an assumption-free max thrust per motor: induced power scales as thrust to the 3/2 power, so the power ratio fixes the hover thrust fraction without any throttle-linearity assumption. When present, this value is preferred over the throttle-based estimates. The sag from hover voltage to loaded WOT voltage also yields a pack internal-resistance estimate.

Manual entry#

If you measured elsewhere, expand Enter values manually instead, type the hover throttle, voltage, and current (and optionally WOT voltage and current), and press Use these values.

Step 4: Calibrate#

Press Compute calibration. The page shows a table of measured versus predicted figures with percentage deltas: figure of merit, hover throttle, hover prop power, hover current, WOT current when captured, and max thrust per motor. Below it, a preview states exactly what applying would set and shows the model re-run with the corrections: the new thrust-to-weight ratio and hover throttle, with the thrust figure flipping from estimated to measured.

When more than one max-thrust estimate exists, the Max thrust from dropdown lets you choose between the power ratio (hover versus WOT), the square law (hover throttle), and the linear estimate.

Then either:

• Apply to build writes the calibrated figure_of_merit and max_thrust_per_motor_g back to the saved build.
• Save as new build keeps the original and saves the calibrated copy under a new name.
• Download report produces a report of the calibration session.

If no correction could be derived, the page says so: capture a steady hover (and ideally a WOT burst) and recompute. If the derived figure of merit is unusually high, a note asks you to recheck the measured weight and that the current reading covers the flight pack only.

Related#

• Live Telemetry
• Cloud relay and the agent
• Build library
• Physics reference