Propellars

Hi there,
After a crash where the turbine seemed to survived with no remarks, it now has a weird behaviour:

At power on, the Handterminal shows 2300 rpm, but the turbine is not running. This only occurs when a servo is loaded, eg. a controlsurfaces is touched or a digital servo beeps. When the 4 cell receiverbattery is fully charged, the rpm is fine, but after using 30% of the capacity, it shows again. The battery still has a fine voltage. My VoltSpy4 shows that it cannot be the voltage-drop when due to servo, as it only drops slightly, and even when I apply an almost fully discharged pack, I still need to load the servo, to see the fault.

I noticed that sometimes priming the the fuel pump also gives some rpm on the terminal.
The rpm sensor seems to work fine while the turbine runs, when I start it up without any servoes connected.
The fault is the same with other brands of servoes and receivers.

Have you tried this before??

Vampire

My Feedback: (2)

Propellars,

I have seen this when the RPM sensor wire to the ECU is located next to and parallel to the servo and or other power wiring. Check the RPM sensor wiring and connectors for damage.
If your doing this test on a work bench and you have the wiring bundled up, this can cause this condition as well.

Rotate the turbine compressor by hand next time you see this and the RPM reading should change. This would imply that the RPM board is working and your issue is outside RFI interferneces.

Propellars

Hi Vampire!
I now tried to disconnect every harness that dident influent on the issue, and moving everything as far away as possible. And now I’m just connecting the rpm harness to the Fadec, and still having the same problem. Pump, fadec-accu, starter harness are disconnected. Spinning the turbine manually up to 3000 rpm, and loading the servo gives a stable jump to 5300 rpm, hence always 2300 rpm higher than real.
As I removed the blue screen, I saw a minor fault on the brown harness, as if it had been in contact with the inlet duct. Could it by any chance have made a shortcut, and damaged the Fadec??

By holding the servo just next to the rpm-sensor, I only need to load the servo gently to see the fault, and when I move the servo away from the sensor, the rpm drops back to 0, until I load the servo harder. But even when I move the servo far away (inserting a extension harness), I still can cause the fault. Tried to put a ferit-ring on the harness, without success.

Propellars

Hi again Kerry! It crossed my mind that it could be airborne noise, so I tried to see if the servo caused the same fault, when the Fadec is operated on a separate receiver and power supply, i.e. no link to the loaded servo. Here I saw no fault at any distance, except when I held the servo very close to the sensor. But I have heard that the sensor always is sensitive to airborne magnetic noise, so I guess I can eliminate that the distance between servo and sensor has anything to say in the original setup.

Vampire

My Feedback: (2)

Hi Lars,

Do I understand that you have identified the issues and can (or have) correct it by relocating the servo cables and or servo ?

Propellars

Hi Kerry
Nope, the problem is still the same. I just wanted to tell you, that it seems like the servo location had some influence, but at any location still gives the same fault, when the servo is loaded as during normal installation.

Propellars

Hi Kerry
I’m now testing my rpm-sensor and Fadec towards my friends similar turbine, and the following weird stuff happens: The initial test on his own turbine and setup showed that his Fadec and rpm sensor is exactly just as sick as mine!! When the servo’s are not loaded, his Fadec shows nice 0 rpm, but as soon one or more servos are humming, (i.e. typical digital behavior), the rpm shows 2300 rpm.. He newer had a problem starting problem. Hmm I think I will rig the turbine up again, and test if it really gives a startup problem with the rpm-fault.
The fault still is quite worrying, as it will occur during flight also. []

Gaspar

You have a old fadec, just use a higher voltage on rx side, anything over 5V is OK. And with the turbine is running is OK too.

Gaspar

Propellars

Hi Gaspar
Thanks! I believe you are right. We just started the turbine of my friend up several times, and the rpm-fault were only seen at turbine-stop. I’ll just start flying with my turbine again [8D]

Thanks alot for your support, Kerry!