Hello,

I built a Whiplash-G II model and I installed a new Spirit GT unit. I have been in the process of breaking in the engine and tuning the response of the Spirit unit for about 2 weeks with no unusual issues.

The other day after letting the engine idle for about 1 minute, I tilted the model forward and adjusted the mixture screws on the engine then set it back level, stepped back and started to spool up.

Right about the moment the model was almost ready to lift off I lost all control. It appears the Sprit froze up. My transmitter did not report loss of telemetry. I could not stop the engine, so I had to find a long pole to reach under the spinning rotors and press the engine kill switch. Scary.

About 10 seconds after killing the engine the swashplate jumped up and tilted forward, then leveled, then control was restored. I power cycled the unit just in case it was in corrupted state, then again tried the spool up and all seemed OK.

Notes:

The Sprit GT unit is running the latest v3.4.1 firmware.

Stabi / recovery features are not enabled.

The RX is an FRSky RX8R and is connected by SBUS wire.

The unit is mounted using the supplied 3M tape on the mounting plate directly in front of the main shaft. The configuration is with the connectors forward.

I have run multiple BEC tests which pass OK.

This model uses a torque tube, not a belt to drive the tail -- there are no belts in the model. (so I would assume ESD is a little less likely).

I checked the log and found no errors or unusual warnings.

This makes me extremely nervous about using the Spirit. A total loss of control during flight could kill someone.

Can you help me figure out what happened and how to prevent this?

Regards, Devin

Hello,

that is very sad. You are right, it is very dangerous and must be resolved before you will try to fly.

There are couple of reasons what could cause this.

What is the most probable is some kind of telemetry or wrong connection that should be not in that way.
So if you can tell how your model is connected and what components are used it would be very helpful.

Can you verify how failsafe is configured?
Will motor shutdown when signal is loss?

Are you using a RPM sensor? If so, how is it connected?

What is your motor? Gasser or nitro?

_________________
Spirit System developer

Hello,

Thank you for your fast reply. Here are the answers to your questions:

1. RX is an FRSky RX8R which is connected to the Spirit GT via SBUS. The connection is between the SBUS out of the RX8R and the "RUD" port of the Spirit. The RX is mounted on soft DuBro foam to reduce chance of failure due to vibration. All servos are Torq BLS servos and are connected directly to the Spirit GT to corresponding ports. The BEC is a HENGE 8A UBEC and has passed the Spirit's BEC test multiple times before and after the incident.

All controllability of the model has been verified it is had been flying well for about 2 weeks prior to the incident.

2. I have failsafe set in Spirit to simply be full down collective stick, normal mode, and, engine idle. This was set using the Spirit control software. I verified that if I pull the SBUS connection to the Spirit the model will go to failsafe settings. I also have failsafe set in the transmitter to handle signal loss. But as I reported no signal loss was reported by my transmitter. I was only about 25 feet from the model anyway.

3. If signal is lost, as currently set, the engine will drop to idle.

4. No RPM sensor or governor is configured. Using only throttle curve in this current setup.

5. Engine is a 23cc TRM VX310SE gasoline engine.

The receiver is mounted in the nose (farthest from the engine as possible). The Spirit is mounted forward of the main shaft using provided 3M tape.

Hope this helps!

Regards, Devin

Hello,

the issue is caused almost certainly by a high voltage coming from spark plug.
This could unfortunately happen and is common source of the problems with any FBL unit and most of the electronics when running gasser engine.
It is very, very important to feed all wires related to spark plug/high voltage as far as possible from the rest of electronics.

The issue will very likely happen once higher motor speed is achieved. For this reason it was not happening often at the bench.

It is also needed to properly ground the motor together with BEC.

High voltage coming to the electronics could even damage it, for this reason behavior could be like this unfortunately. It is like instead of 6 volts it will receive for example 5 000 volts.

After these changes all should be fine.

_________________
Spirit System developer

Thanks again for the prompt response!

The wiring is already about as far as possible from the engine spark wiring -- however I will look to see if this can be improved.

Your suggestion to ground the engine to the rest of the electrical system ground is an excellent idea and will do this immediately.

I will make the adjustments and then test first without blades for a while to see if any problems occur before returning to flight. I will report results here.

Thanks again.

Regards, Devin

"2. I have failsafe set in Spirit to simply be full down collective stick, normal mode, and, engine idle. This was set using the Spirit control software. I verified that if I pull the SBUS connection to the Spirit the model will go to failsafe settings. I also have failsafe set in the transmitter to handle signal loss. But as I reported no signal loss was reported by my transmitter. I was only about 25 feet from the model anyway."

Hi!
It's not good to set failsafe with full down collective stick (if you use same amount of negative pitch as positive pitch, [for example -/+ 12°]), because when the model will lost signal, it will try to push it somewhere... (the worst case when the model will push itself to the ground very fast)
So the best way to set failsafe, is the collective stick in the middle (if you have 0° collective pitch in the middle), and engine idle.

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Jeti DS12, Align T-Rex 470L with Spirit GTR, Soxos Strike 7 with Spirit GTR

Hello,

Thank you for the tip. Yes this makes perfect sense. I reset my failsafe with the sick in the middle (0 degrees) and throttle at idle.

Thanks again!

Regards, Devin