I recently purchased a new Spirit GT Flybarless unit with GeoLink v2. I'm searching for answers as I have recently had a second, nearly identical, crash while using the the new Spirit hardware with essentially no changes to my previous setup.

While flying my Align 760x, the machine rolled extremely fast backward and slammed HARD into the ground. Both crashes occurred at about 5 feet above the ground during a hover. Unfortunately the second crash occurred over asphalt and the machine is essentially destroyed.

I was able to get about 5 or 6 flights between the first and second crash. During the flight before the second crash I noticed a strange and very subtle change in the throttle, It was as if someone quickly lowered the stick 15% and raised it back (I cant recall at this point if it felt like a drop in the pitch, throttle, or both). Maybe 30 seconds later I noticed a twitch in the tail, similar scenario. I immediately landed and inspected the entire helicopter. I honestly cant be certain these weren't normal events due to wind or something else. I should note that I am experienced as I've been flying helicopters for about 25 years.

I've gone through absolutely everything. I've come to the conclusion that the only possible culprit at this time is the flybarless unit. I even went as far as replacing the rear swash servo (DS820M) just to be safe after the first crash only to have the exact same crash again.

As you can imagine this is extremely frustrating. Any help would be appreciated.

Hi,

What would be the sequence of events prior to experiencing this behaviour? I assume you run the geolink cable close along the tail tube right? sounds like some static discharge to me which could have been absorbed by the goelink cable which then affected the rudder servo "twitch" and then continued to other electronics on the subsequent static discharges.

Are you able to download and share the vibration logs of the last flight? also the logs from the ESC to check is the RPM change was a commanded signal or not, so to check if the rpm change aligns with the THR output value.

Hello,

please share a wiring photos and your settings file (4ds).

For example if your receiver is Futaba please make sure to use SBUS1 port, not SBUS2. This could cause a random twitching and unexpected behavior.
At the moment I have no more details to help you, so anything to your wiring and setup would be very helpful.

I fear it has something to do with receiver connection/data processing, RPM sensor or some other wiring.

_________________
Spirit System developer

SBUS2 causes unexpected behavior when it's supposed to be fully supported and the manual has instruction to use it?
https://manual.spirit-system.com/index. ... _Telemetry
What is this even supposed to mean? Is it supported or not???

It is fully supported, but according Futaba the wiring must be correct. For example powering servos (for example for throttle) from receiver that is connected only at the SBUS2 port can cause loss of control. This is basically described in the receiver manual.
SBUS1 port seems to be fine for powering.

_________________
Spirit System developer

There is nothing wrong with powering servos from the SBus2 port on a Futaba. The + and - power pins are on a common bus across every port on the receiver. I have multiple airplanes that use SBus2 servos running on the SBus2 port and have never had a single issue.

The only issue with connecting servos to the SBus2 port is that they MUST be Futaba SBus2 compatible servos (like the HPS series), anything else wont be able to read the data signal.... But in your case the servos would be connected to the gyro and the gyro is handling the communication with the SBus 2 port so it shouldn't be an issue.

you had the similar problem to my friend's helicopter.
Spirit is not the problem, but the problem is the receiver.
For many years used futaba radio and receiver without problems.
A day without a reason had similar problems to yours.
Changing the receiver I solved everything.

Thank you all for your feedback and suggestions. I wanted to provide additional details about my setup and address some of the questions raised so far:


Receiver: Radiomaster RP3-H

Transmitter: Radiomaster Boxer running EdgeTX with CRSF protocol

Other Helicopters: This transmitter/receiver combo works seamlessly on several other models, including the Sab Kraken 700, T-rex 700N DFC, T-rex 600N DFC, T-rex 650x, and T-rex 450L. I haven’t encountered any issues with this combination until now.

RPM Sensor: I use a Spirit RPM sensor with a magnet on the main gear (I opted for this over ESC-based RPM telemetry).

ESC: Scorpion Tribunus II 300A ESC


Responses to Questions Raised:
Static Discharge: @senaka, I appreciate your suggestion about potential static discharge affecting the system. While I’ll examine the routing of the GeoLink cable and consider rerouting or adding shielding, I have to admit I’m a bit skeptical. Given that these systems are designed for demanding environments, one would expect static-related vulnerabilities to have been addressed during engineering and testing. However, I’ll still inspect the wiring thoroughly and share any findings.

I understand the concern about proper port usage for servo power. In my case, the servos are powered through the Spirit unit, not the receiver, so this should not be a factor.


Logs: @ZeXx86 and @senaka, I’m working on retrieving the vibration logs, ESC logs, and Spirit settings file as I disassemble the helicopter. I’ll upload them shortly for review.

Before the crash I had been hovering and flying slow. I had just put a new pair of blades on and I was eyeing the blade tracking.


Next Steps:
I’m currently disassembling everything from the crash and will share detailed logs and photos soon. I appreciate the thoughtful responses from everyone and hope the additional data will help pinpoint the root cause. If there are any specific tests or setups you recommend, please let me know.


Thank you again for your input!