Version: 1.4.18.0
Frequency: Consistently
Severity: Blocker
All helicopters
Bug description: when decreasing throttle from “flight” to “idle”, there’s close to zero deceleration of rotor RPM, thus indicating, that there’s no rotor friction and/or no parasitic blade drag taken into account by CFD
Repro steps: reproducable with every helicopter in MSFS2024
The available rotor friction parameter is definitely working. I know that for sure since I was tweaking it on my project some days ago.
The problem is related to the default throttle. If you are using the default helicopter throttle it is almost impossible to achieve realistic behavior since it is likely not reducing the engine throttles enough in the idle state.
In my own project I have custom coded a throttle based on the rotor rpm I want to achieve in idle. The percentage of engine throttle that is required to achieve that idle rpm will be different for every helicopter based on the rotor inertia and friction value.
Thats why it will be impossible to achieve good results with a default throttle because every helicopter throttle is a bit different. I would recommend setting up your own code so you are in full control and can adapt to the specific needs for the project.
Try to completley shut down the engine, starting at rotor RPM/N2 at flight.
With zero throttle and zero N1/N2, you still won’t have any significant decrease of rotor RPM. If it’s not missing rotor mast friction, then it has to be missing parasitic balde drag…
Everything is working for me in that regard.
Are you using the rotor friction torque parameter? That one needs to be set up and the rotor inertia value needs to be significantly lower than a real world value.
All that might be correct. That’s just not the core of the issue, IMHO. Plus, it has been working not too long ago…
And it is reproducible with any helicopter in 24, try the default H125 for example…
I just had a look.
The h125 can not be fully shut down using just the throttle twist grip because it is only going from idle to fly. There is no off position. In the idle state the governor in the h125 aims for 70% percent rotor rpm. To shut down the h125 the fuel needs to be cut off. That lever in the overhead seems to be broken right now, I remember it working in the past. So fuel cutoff not working is the reason for the issue you are seeing.
Hello @TheDude9974
Can you elaborate on what helicopter you are working on, what rotor_friction_torque and MOI you have configured, and what deceleration you get vs what you expected?
Our core engineers reviewed your feedback and checked the Cabri and H125 but although some config adjustments are known to be needed, particularly on MOI, no fault was identified on the system itself.
We would need a bit more info to be able to consider your claim.
Regards,
Sylvain
Hi Sylvain
Thanks for contacting the core team to look into this.
Knowing that the system is correct helped us narrow the culprit down to the blade MOI.
Our initial interpretation was wrong.
With too high (even default) a blade MOI set, reasonable values of drag/friction has no noticable effect on rotor deceleration. We had a wrong conclusion. Sorry. It happens.
Thanks for looking into it.
regards
Stu