Twin throttle collective lever test build

Twin throttle Bell 412 – style collective

download dev snapshot

I have assembled the twin lever today, everything fits very good. However, I should probably describe one minor “issue”. While building the lever, one MUST drill holes in the second engine throttle grip frame AND put screws into that holes STRICTLY BEFORE routing wires through the lever. Had to put everything apart 3 times because of that (well, at least this way I confirmed the possibility of disassembling the lever multiple times without breaking it). I also noticed, that in the dev snapshot the “collective_connector_adjustable.stl” file was oriented incorrectly. Consider turning it 90 degrees along the Z axis, or removing supports from inside of it will be very hard. Another very minor issue is with an idle stop “detent” mark, it will probably be placed 5 or 10 degrees higher. Otherwise, the dev build files are fine. Will correct this stuff in the release version, which I will post in a couple of days after some testing.

Now, let me share my feelings from the first flight with it!

My first impression when I have attached the head was “Jeez, this one is heavy!”. I was wondering if the tensioner will be able to hold the lever without making it too stiff. After I hooked up a couple of rubber bands, the weight of the lever was countered, it balanced somewhere around a middle position. Then I’ve been able to adjust the tensioner so it could hold the lever in the lower position and barely hold it in the upper one (I like very smooth controls travel). After that, I tried moving the lever, and it felt just like the single throttle one. Everything felt OK so I’ve spooled up the 412, checked the controls, disabled AP channels and pulled the lever up…

It felt quite nice and smooth. In fact, I didn’t really notice any major differences from the single throttle one, and it is great because the thing is quite a bit heavier! After flying around for a couple of minutes I’ve tried hovering. No issues so far… Then I turned the governor switch to “MANUAL” position. and tried flying with it for a while. For some reason, it felt easy enough to control throttles manually. Maybe it’s just the right turn angle of throttles (200 degrees, somewhat like in a real one), or absence of the wind. Next thing I decided to do was to shut down engine 1 in a hover. Suddenly, I noticed engine 2 exhaust gas temp needle jumped to the red zone:  the second engine was struggling to hold the heli in the air. Going through ETL, I was happy to see that shutting down an engine actually affects the behavior of the helicopter, not much sense in using twin throttle lever otherwise!

To sum it up: the lever feels good, and after a few days of testing (I have to confirm that its structural strength is enough) I will release a final package. Meanwhile, I will be adding software features to the master controller firmware.


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