SK540 RPM Sensor Question - Nitro

[ticedoff8]

I have the Futaba GV-1 sensor attached to the SK540. I have 2 heli setup the same way with the GV-1 & SK540 and they have been working great - until last Monday.

As I was flying my #2 heli, the engine seemed go into a "flat" throttle curve - about a normal rotor RPM (sounded about right) but definitely not responding to loads on the head like normal.

I flew around for a short time, did a couple of pitch pumps and flips - just enough to confirm (to my ear) that the engine wasn't tracking the load.

Landed and power cycled everything, refueled and flew again - and right away noticed the engine wasn't tracking.

I figured the gov sensor had shifted and was not seeing the magnets or the lead was loose on the SK540 and packed everything up and went back to work (I hate it when that happens).

On the bench, using the Skookum setup program, I checked the gov sensor and see that it toggles as the magnets pass the sensor. The sensor is solidly mounted and has about 1mm gap (exactly as I installed it originally).

Is there a "gov sensor signal loss mode" that the SK540 uses if the gov sensor signal is lost (limp home)?
Or, should it "pass through" the throttle channel if the gov sensor signal is lost?

My throttle curves on the DX7 TX are shallow V-shapes for Stunt-1 & Stunt-2.
The goal is to use the 3 different RPM settings, so each V stays within the SK540 hi/low set points for each RPM.
I confirmed (long ago) that Stunt-1 (or Stunt-2) will stay within the 2nd (or 3rd) RPM range from as the collective moves from -100%-0-+100%.

I read another thread about the SK720 & ESC gov mode that seemed to imply the SK720 would go to 70% throttle if the gov sensor signal is lost.

Any thoughts?

[georgi UK]

=] yes, you will get a 70% throttle to get you home for a sensor fail, this will also trigger for a low voltage alarm too.

using V curves within the RPM flight modes will have no effect on the actual headspeeds, these remain fixed.

[ticedoff8]

Did not know that.
So a gov sensor failure mid flight will default the engine to "70% throttle" (limp home) and stay as long as the gov is above the engagement point.

If the sensor "comes alive" again at some point before the end of the flight, will the SK540 gov start tracking again? Or, do you have to power cycle / reset the SK540 before it will start using the sensor input again?

Also:
What if the sensor is dead at power up of the SK540?
Will the throttle servo track the TX V-curve or just go straight to the 70% point when the throttle reaches the gov engagement point?

Thanks

[georgi UK]

=] in-flight fail is 70% throttle, gov misfire ( unlikely?) no idea, non sensor start, limited throttle I guess?

there is no V curve, zero to 40% or 60% or 100% all flat-lined after the initial ramp.

[ticedoff8]

Originally Posted by gmcallister

=] in-flight fail is 70% throttle, gov misfire ( unlikely?) no idea, non sensor start, limited throttle I guess?

there is no V curve, zero to 40% or 60% or 100% all flat-lined after the initial ramp.

But, what happens if the gov sensor is bad at startup?
Does the gov still try to engage?

[georgi UK]

Originally Posted by ticedoff8

But, what happens if the gov sensor is bad at startup?
Does the gov still try to engage?

=] it can't, got nothing to work with, grounded.

[ticedoff8]

Thanks for the answers.
I apologize for not making myself clearer.

If the gov sensor is disconnected / dead at power up, will the SK540 gov still engage at the 30% throttle point? Because, if the gov engages as normal and the is no sensor input, it would likely go directly to the "Limp Home" 70% point.

Or, is the SK540 monitoring the sensor input + the throttle position? If that's the case, then no sensor input would disable the SK540 gov and it would... do what?
Pass through the throttle channel directly to the servo?
Disable throttle completely and go to idle?

[thefrog]

Originally Posted by ticedoff8

If the gov sensor is disconnected / dead at power up, will the SK540 gov still engage at the 30% throttle point? Because, if the gov engages as normal and the is no sensor input, it would likely go directly to the "Limp Home" 70% point.

Yes, this is what happens - the gov engages but as no signal is received from the sensor it defaults to 70% throttle. You will notice - the heli will bog a little during climbouts and headspeed won't change when switchig flight modes. This is for both nitro and electric.