As per my previous posts, the Spirit GT does not provide throttle servo output telemetry which makes it hard to analyse governor performance. However, I have created a custom solution using a microcontroller to measure the servo PWM and provide this via telemetry to Jeti TX. It has been stated Spirit will provide this telemetry itself in future but that is not the point of this post.

See attached screenshot of one of my test flights on a OS 55 HZ engine on a NiTRON model.

In general the governor seems to perform reasonably well however there are many overspeed events and in looking at the data I noticed that the throttle output is NEVER below 50% which would surely help reduce overspeed.

Can anyone explain what is going on here? Why won't it output less than 50%?

In the 2nd image, you can see the highlighted area where we have an overspeed condition (RPM > 1900) but throttle output is 50%, a lower throttle here would assist in reducing the overspeed condition quicker...

Ok, found this post viewtopic.php?p=31185#p31185

Clarifies the min throttle value = 2/3 of requested value. Seems to agree with what I'm seeing in the data (I use 80% / 2400 = 1900 RPM). I will drop this to a lower value to get a lower min throttle.

The other issue in the graphs attached I think I can solve using the 'holding limit' % - I have it dialed up to 85% (I should've gone lower). Will play around a bit more.

Ok, I was wrong. The min throttle is NOT 2/3 of requested throttle. It appears to be the value of the throttle output that achieves the desired headspeed when the governor has reached the target headspeed (some kind of calibration process).

Throughout the entire flight the throttle will NOT drop below this value. In my most recent test this is around 60% and note I would try to lift off (positive pitch) before reaching full headspeed to avoid model tip over on the ground so this throttle % would be affected by the positive pitch when the target headspeed is reached.

The governor ALWAYS overspeeds on rotor unloading and is almost ALWAYS due to the throttle not being set below this minimum value.

Can you please explain why this is so and if I/we can expect a fix, because as it stands the governor is fundamentally flawed.

Logs from today's testing. Once again overspeed cannot be controlled due to clamped throttle output.

Hello,
I am using an Evolution 10 engine on a Hirobo Shuttle helicopter.
I noticed the same overspeed problem when the engine is lightly loaded, for example on the ground or during rollovers.
My tests have shown me that the regulation only acts on 50% of the servo travel, either in the upper part if the motor is loaded when the governor has just been engaged (calibration procedure) or in the lower part if the engine is lightly loaded at this time.
In this case, the carburetor never opens fully even when the speed is too low.
I tried to modify the minimum and maximum servo travel values (900 to 2100 µs) to obtain more extensive regulation, but that does not improve the problem but causes the servo to stop mechanically.

I understand that the carburetor should not be closed completely but the current limit of 2/3 is too high. The possibility of adjusting this limit would be welcome.

We will allow changing the limit in next version.
It will be available shortly.

Thank you very much for the reports!

_________________
Spirit System developer

Hello,
Thank you for taking our comments into consideration.
I look forward to the next version.
Thanks again, best regards.
Serge Duboc

Hello Thomas,

After installing the 3.4.1 update, I noticed that the regulation works perfectly even when the incidence of the rotor is low. I couldn't find any information about this in the update listing, but thank you very much for considering our request.

Best regards.

S. DUBOC