Gasser Heli First Flight - Error Compass Var

Hello all,

I have assembled a gasser 700 size and made setup based on new Wiki and I flew fine but I saw EKF errors popping up .

Flight was all Stabilize as you can see in the logs. Also Param file is attached too. I did damper on the autopilot and compass to ease off vibration coming from the frame. I am little confused if EKF error caused by vibration or magnetic interferance.

Param file
gasserparam.param (14.6 KB)

Flight Log

Any help is appreciated as I dont want to crash in loiter because of this.

I do not actually see any EKF errors in that log file?

One thing, not related to EKF at all, but I noticed in your setup; you have a piston engine but your throttle curve appears to max out at 45%?


How can this work? It will certainly work in stable hover, or very light load changes. But I would think severely limits power in any sort of high climb rate or high speed flight. Are you sure that is right?

Back to the EKF, I get all sorts of annoying EKF announcements coming from the ground station with 3.6. It is like a finicky thing that just complains about everything. If I pick up the helicopter and move it it complains about compass variance (or whatever). I have become convinced it will complain about a bug crawling across the windscreen. I have actually gone to turning off the audio feedback from the GCS because I get tired of hearing about all its problems and it is distracting. So it could be what you’re experiencing is normal.

Hello Chris,

For the throttle curve, i am trying find the optimum levels to get best out of the gasser engine. I do have a zenoah g320rc on it so it is powerful that will give enough power to hover yet you are right i still need to increase throttle.

I was being conservative to be honest. Still need work on tuning on hover throttle as i am planning to put a camera gimbal on it later on.

Thanks for the valuable input.


Yeah, I think you will want to increase your throttle to 100% power at full pitch. Even with the most powerful engines the 5-point spline curve can be adjusted to perfection to fit the engine’s torque curve. That will be important if you use an external governor, or ArduPilot’s new internal governor.

The 320’s are notorious for vibration, since it is a bored G290. So you’ll have to find the “sweet spot” where it likes to run at least vibration, and that will be the speed you’ll fly at. I fly both stock stroke and stroker Zenoah’s. The 310 2mm strokers are smoother than the stock engines because the stroker crank has bigger counterweights. The 310 stroker likes to run around 11,500 rpm. The stock stroke 290’s like to run around 10,800.

Zenoah started out with the G230, which is the smoothest running of the 28mm stroke engines. Then they keep putting on a bigger jug and piston to increase the displacement, without changing the crank. This obviously started generating vibration problems. The engine builders like Al at TRM Power fix this by balancing the recip assembly with the rotating assembly in the big-bore engines. Or put stroker cranks in to balance it. The difference is pretty significant between a helicopter-specific balanced engine and a stock one.

Your 320 has a bigger crank pin and bigger rollers on the big end of the rod. Al at TRM Power told me they have problems with those at high rpm because the rollers tend to skid on the crank pin instead of rolling, and it galls the crank pin. He doesn’t recommend running the 320 over 10,800 rpm.