Stumped on intermittent altitude/motor/throttle losses

I’m relatively new to the RC Community. Started building my first series of hexacopters with the APM 2.5 board. I also have attached a telemetry radio and GPS with Magnetometer from UAVObjects.

Now that I’m onto my fourth build, I’ve learned a good bit about the many pre-flight checks necessary before successfully flying. I have been very diligent to encourage the best performance of my hex, and I seem to have reached a bound of understanding.

In numerous flights recently, I have experienced strange losses of “throttle input” or “power” or “altitude” or “thrust” or whatever you want to call it. The hex will be flying along an autopilot path, make a turn or something, and then seemingly lose power and drop a few meters before the computer picks it back up.

A few days ago, I abandoned my Power Module in favor of a Turnigy 3A UBEC feeding power into the electronics. Before doing so, I was getting low board voltage readings, and auto-analysis claims voltage failure. After switching to the UBEC, board voltage now seems stable.

In a most recent flight, I was testing the gridded way-point system in Mission Planner when I experienced this same phenomenon more than a handful of times. Spikes can be seen in the Z-Accelerometer for sudden altitude changes, as well as the altitude values.

The correlation I found was linked to the graph of the “throttle input” which seems to spike negatively at the same times.

Any and all insights on how to further investigate would be greatly appreciated.

Neurax

You’re getting big barometer spikes, probably due to light getting in the baro.

I’m using the AV Dome kit from UAV Objects, the magnetometer is placed about an inch above the apm with a clear transparent dome over it. I taped a piece of foam over the baro to prevent an issue like that.

I’ll check the fixing on it, what’s the best way to ensure light leaks don’t happen?

Also, would this account for the changes on throttle input?

[quote=“neurax”]I’ll check the fixing on it, what’s the best way to ensure light leaks don’t happen?

Also, would this account for the changes on throttle input?[/quote]
An opaque case, and yes.