Today I flew with a new setup in a manned, fixed-wing ultralight airplane: 10m wingspan, 25 hp gas engine, 200+ kg gross weight. The Cube Orange isn’t being used as a flight controller but rather as a flight recorder.
The problem was that the altitude displayed on Mission Planner was wildly wrong, showing rapid fluctations but never getting more than 10 to 20 meters (plus and minus) from zero. Actual altitude reached was about 120 m
Looking at graphs of the logged variables, I found that the two absolute pressure readings were normal, as was the GPS altitude, so I’m assuming that low-frequency vibration affecting the IMUs is responsible for the error, possibly through some kind of aliasing effect. The two graphs below (made in Excel from the exported CSV file) tell the story - the altitude on the left looks correct, but the oscillating altitude on the right (apparently in millimeters?) is closer to what was displayed.
My question: assuming the problem indeed lies with the IMUs, is it possible to tell Arduplane to disregard IMU z-inputs entirely and rely only on the pressure for displayed altitude?
(I could post the telemetry log file if requested but don’t currently have access to the on-board files.)