Loss of GPS fix on throttle

Hi everyone,

two weeks ago I assembled my first APM quadcopter build. I’m using an APM 2.6 with power module, GPS, telemetry and OSD. All works very well and hovering is satisfying. Today I picked up my quad and laptop to do some more interesting stuff like RTL and GPS navigation. Right before launch all pre-arm checks are fulfilled and I have a GPS fix (11-12 satellites; HDOP 1.4-2).

Once I rise throttle to hover the quad GPS lock is lost and never get back until I plug the flight battery out and in again. In APM Planner Lat/Long are still valid (changing) values but satellites, HDOP and Fix are empty. After some time hovering Lat/Lng get 0 or 0.00000343. But it get even more mysterious: If flight battery is full or nearly full this does not happen. Only after some flying this behavior can be observed.

Whats wrong with my GPS/Setup?

Im using an APM Kit, Turnigy 9X as radio, APM Copter 3.2.1 and 4s lips.

Edit: First attempt to resolve this issue was to install an extra 5V/3A BEC for powering GPS, Telemetry and OSD. Maybe it gets a bit better, but not at all. Problem still exist. After this modification Vcc of the APM is 4,85-4,9.

Sorry for double posting, but i can’t edit my first post :frowning: Maybe someone can bring together this two posts.

Additional notes for my first attempt to fix this issue: While investigating this problem I observed some huge Vcc drops (seen in APM Planner Graphs) Sometimes below 4.5V. So O decided to install an extra BEC for GPS, Telemetry and OSD. After this modification my Vcc is almost constant at 4.85V.

You need to post logs, as it’s very hard to analyze otherwise. Either the dataflash log (onboard log) or the telemetry log (blog) by APM Planner 2.0 (both would be better)


Sorry for forgetting logs. This one is from hovering around a bit to test GPS.

Short question: What means “No MAG data, unable to test mag_field interference” ? Compass works as it should and is calibrated.

Something is odd, as your time is inconsistent. jumps in time mean something is happening that is bad. Time should be a linear ramp up. The GPS time, resets to zero at these points. Note you have huge drop in alt at these points. Vcc seems constant. But something is not right.

Not sure what the issue is yet, Faulty GPS (could be wiring)? Maybe the regulator for the 3.3V on the GPS is failing?


Thank you.

It was a faulty GPS. After replacing everything works as expected.

Great, Happy Flying :slight_smile: