OK to use swtich for Throttle trim?

[flymustangs]

I'm still on a quest for the perfect radio. The DX8 is no more. I've been using a Futaba 8FG lately and may even give the Aurora 9 a try ). Like the DX8, the 8FG has a digitial trim for throttle instead of an analog trim like the JR radios.

The 8FG does let me use a switch instead of the trim lever. The idea being use one of the three position switches for trim low, mid and high. It's seems like this would be a good solution for a radio with a digital trim for starting a Wren turbine.

Am I missing anything here?

[cbergen]

Using a switch HAS been done and it is or at least WAS in the Wren 54 manual, I prefer the trim so I can move it as slow or fast as I like.

For instance, when coming DOWN from Flight idle, I usually bring it down slowly. Flipping a switch is instantaneous...

In the Futaba radios, I change the throttle trim step so that it doesn't take 20 beeps to get to mid trim...

[flymustangs]

Didn't like the Aurora, but I came up with a solution for the digital trim on the 8FG (the Aurora has a digital throttle trim as well).

The 8FG has two knobs on the top front of the radio. They each beep at center position. I'm going to use one of these as my throttle trim for turbine start. I haven't tested it yet because it's been either raining or snowing here for the past couple of weeks.

I've also set up one of the sliders on the side of the radio to act as a full range throttle trim to adjust head speed for atmospheric changes. I've lowered the range of this trim so it can't make a large difference in the throttle curves. I just need a good way to check the head speed. That's why I was interested in the DX8 and the Aurora 9 because of their telemetry. I guess I can have a buddy tach it every time, but there has got to be a better solution.

I did just pick up a used EagleTree telemetry system from a fellow turbine guy to give that a try. There is a rumor that Futaba is coming out with telemetry next year. They are coming out with an upgrade to the 8FG that will add 4 channels.

[flymustangs]

Got some sun today and temps above freezing so I got to try out the new radio setup. It works great. The slider on the side I have set up for adjusting head speed is hard to move, but I think that's probably a good thing. The knob for turbine/start shutdown works great.

We did notice one thing while checking the head speed. I was getting a slight tail wag. I've noticed this on prior flights. Adjustments to the vbar helped a lot. The wag is not consitent in it's frequency or amount of movement. I figured I just needed more adjustments on the vbar. However, my buddy running the tach also noticed a change in the head speed consistent with the wag. A quick change in head speed could certainly cause a wag like this.

The question is what's causing the head speed change. With a turbine I don't think the turbine speed could change that quickly. My first thought is main shaft bearings. I'm not sure how many flights these bearings have on them without looking at the log. It's probably about 50. Should they last longer than that? I don't mind replacing the bearings if that's a likely cause. I would much rather be safe than sorry with the main shaft bearings based on experience.

[cbergen]

Check the bearings by hand, which means pulling the main shaft. Spin themm with your finger, feeling for notchiness.

Also check your clutch liner for oil or grease contamination, resulting in possible clutch slippage.

[flymustangs]

Thanks! Will do.