So your quad doesn’t fly right. It has strange oscillations, vibrations, falls out of the sky, etc. Here’s what you do:
- Check that all frame screws are tight.
- Make sure all standoffs are straight.
- Check all the screw motors. Make sure they are not touching the windings. Test continuity between screws and leads with a multimeter (there should be no continuity). If there is continuity, use shorter screws.
- Inspect the frame for cracks. Make sure it’s solid everywhere.
If you have tuned the quad, try the stock tune to rule it out as a cause of vibrations. A quad on stock tune should not vibrate unless it is a very unusual setup.
If none of the above solves it, test individual components. If you have a firmware that allows motor testing, remove the props and spin each motor independently. Hold each arm while spinning its motor and feel the vibrations. If a particular motor vibrates, either try replacing the bearings or just put in a new one.
Quad falls out of the sky
Watch this video by Joshua Bardwell. Most likely it’s a motor and / or an ESCs.