Hi all:

I asked this question on HF and emailed Tomas but haven't heard anything yet so I joined to post here as well.

Question: I'd like to hear from folks that are using Spirit GT on gasoline (petrol) 700 class. How is it working?
- Is rescue functioning reliably?
- Does the ground mode logic work correctly to prevent tipovers?
--- i.e. when on ground with blades stopped and engine running, does swash self return to neutral when the sticks are released
--- Does this work correctly both on initial startup and after autorotation landings?


Years ago I tried the original Spirit on one of my 700 gas but gave up as it would rescue sideways sometime and acted very tippy on the ground. Recently I have a couple of electric machines setup with Spirit GT and really like them and am considering giving the GT another go on my gas.


Not concerned with the governor as I am sticking with GV1.

Hello,

I can only answer according our findings. From Spirit 1 there are no general issues with Gassers and many pilots are running them for almost 15 years with the very first Spirits.
Each Spirit generation had improved sensors handling vibrations even better. Current GTs have the best sensors in the class so there is again less chance for any issues. But that is actually worse for pilots that wish to keep their models in a good condition, because it could fly well until a bearings will be flying in the motor or bolts will dismount because of resonant vibrations.

Since Rescue was introduced there were many improvements over the years to it and also directly for combustion models where you can enable Extended signal processing. At the moment we can say Spirit has the most tolerant Rescue for vibrations from any other unit at the market.

Regarding gassers itself, it actually does not matter if it is Gasser, Nitro or Electric for rescue. It only matter in which condition the model is. Pilots of combustion models are not used for doing vibration analysis to find if their bearings are starting to fail, so it is more common to fly with model in a bad shape - because you simply can't hear odd sounds from rest of the mechanics. For example your model can produce extreme vibrations at the tail mechanics, but you will not find it without checking by Spectrum Analysis tool. This mean it does not matter if the same tail is powered by electric motor or not, because it will cause trouble for each model with such problem.

_________________
Spirit System developer

Tomas,

With respect I am going to disagree with you on this point. I absolutely CAN tell when things are going bad on my gas machine. The vibrations and resonance from bad bearings or bent shafts is at a much lower frequency (i.e. a multiple of the 1800rpm head speed rather than a multiple of the 13,000rpm engine speed). You can often SEE it visibly. I had a cracked engine mount last summer (after 10 years of run time on the original) and it manifested as a very visible cyclic wobble at low headspeeds. Took lots of hunting to find the hairline crack but the symptom was unmistakable. Same thing with something like a bent tail shaft from a bad landing... a very visible tail shake/hunting results.

Please don't just write gas machines off as "vibration monsters that cant be helped". The gas community would appreciate our concerns being taken seriously.


The second part of my question you didn't answer - is ground mode working properly? I quote what you said on Helifreak 3 years ago when somebody else asked:

" It is very important to verify that swasplate is level when lifting off. If motor is running or model is not restless, unit will still try to maintain desired position given by sticks (even few moments ago).
So when landing and then lifting off make sure to take extra care.
With nitro if motor is running, swashplate will never level itself after landing."

https://www.helifreak.com/showthread.ph ... ost8405433

This is basically saying that the vibration of a running nitro/gas engine will defeat the logic that detects the heli is on the ground vs. in the air. If so it makes this system effectively unusable for a gas machine as I cant shoot autorotations without killing and restarting the engine each time.

I am asking if this bug in the logic is fixed. If it is, great, I may buy two more Spirit GTs. I know that this behavior can be made to work as BD had it working 15 years ago with much older sensors and more primitive processors than you have now.

If not Ill have to stick with my aging BD3sx's.


Thanks,
jeremy

Hello,

thank you for your explanation. I dont meant vibrations of motor itself, but vibration of Tail Mechanics. This is usually more problematic than motor itself because resonant frequencies are developing there in almost all cases. Resonant frequencies are killing each motion sensor, they are well audiable but if combustion motor is running there is only very limited pssibility to find this.

Regarding "bug" you mentioned - no, this is the way how Spirit is working for 15 years. It is same for Electric motors as well - as soon as motor is running Swashplate will not return to center position.
It is not problem for combustion models too, because you should touch the sticks during lift off, not at the bench when motor is running. Because until you will touch the sticks, unit will remain in the "Ground mode" preventing Heli from accidental tip over.
This mean it will work as other FBL unit in that mode until you will move with Aileron, Elevator or Rudder stick + running motor.

The behavior is more or less similar to a Heading Lock Gyro mode where it is recommended to not touch the sticks until lift off or at least try to set it more or less at the center.

_________________
Spirit System developer

Hi, I run a Spirit GT in my T-Rex 700 gasser with no issues. I have the basic rescue mode enabled and that works fine if that's any help. I also use the governor function

I think we are misunderstanding each other. I went out and checked my 700 gas machine with BD3sx again.

On the ground, power on, engine not started - Move cyclic stick and release, swash moves and then returns to center on it own.
On the ground, power on, engine running, blades stopped - Move cyclic stick and release, swash moves and then returns to center on it own.
On the ground, power on, engine running, blades turning - Move cyclic stick and release, swash moves and holds position.

So there is defiantely another way to do it that works better on gas and can figure out that its on the ground without having to kill the engine. Any chance you can look at how Bavarian does it? This works a LOT better for gas machines for stable landings and no tip over after autorotations.

Tomas - Any idea about the behavior difference I suspect I see in Spirit vs. BD3sx?

Behavior difference you can see is correct.
As I explained previously this is one of the difference that makes flight performance for Spirit unique.
It is quite easy to change the behavior but you will loose big benefits. We could add parameter to enable this behavior but we do not recommend it.

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Spirit System developer

listen me why It's been since 2010 that I mount helicopters.
If you activate logs what value of vibration you have during the flight in the air?

It has no relation to vibration level. He is describing normal behavior of the Spirit, but he dont like how it behave on the ground.

_________________
Spirit System developer