Intermittent Full pitch suicide on IU switching

[FireDoug]

Heli is Blade 450 3x1000 FBL, stock eflite 35a ESC, stock Spektrum RX, DX8 TX, HiTech servo. Heli has about 50 flights on it with this setup.... flying like a champ.

About a month ago while testing in front yard the heli full pitched into the ground from about 15' while I was switching from normal to IU. I rebuilt and went through all the setup on heli and TX. Everything is good, test flight and does it again. So rebuild and now on the 3rd time it does it again. The bad part is it is not every time I switch IU. Sometimes it is just fine and flies a battery with no issues.

So I have been racking my brain and I am thinking maybe replace the ESC? Every once in a while the gyro won't intialize and I have to cycle the battery. The stock ESC has that funky thing were you have to program 10% in the TH to keep it from spinning up on battery insertion with TH on.

Any thoughts, I hate intermittent problems??

[Dr. M]

Did you happen to look at the swashplate right after the crash? Were the servos responding? If not, you may have a static problem.

What swash servos are you running? Are you sure they're all working properly? This could be a flaky servo... I'd look at the elevator servo very carefully, maybe put it thru some torture testing.

Also, check out the gyro wiring. Open the case and look at the solder joints where the wires connect to the board. Might be a good idea to heat those up anyway and reflow the solder.

[FireDoug]

Cyclic servos are analog, Hitech hs65mg
Each time before the Heli suicide I have run the bird thru the bench tests with an Align digital pitch gauge. Setting pitch at 12 +& - and elevator and aileron at 8 degrees

The swashplate responds perfectly to all TX inputs.

In the air it flies fine a even responds correctly to all IU changes. Then all of a sudden it will full negative into the ground faster than I can react. This only happens from normal throttle curve to IU.

I am leaning toward the ESC thinking. It might be sending some crazy signals to the RX and in turn jacking with theFBL controller.????

[Dr. M]

I've not heard of a problem that even remotely resembles what you're describing. I recommend you post about this on the RCG thread linked below. There are a lot more people over there who may have ideas and have extensive experience with the ZYX.

http://www.rcgroups.com/forums/showt...12179&page=414

[Mikej]

It does sounds very strange - have you tried taking off in Idle 1, is that OK. Something else that you could try is disconnect the motor, power up in Normal (blades not spinning as motor disconnected) watch the swash, and also have the ZYX monitor running on your Pc and see how the settings change as you flip between Normal and Idle Up - perhaps the DX8 is sending funny commands or perhaps the ZYX is beeing switched into Condition 2 ???

[AKPhill]

Had a similar problem and what I found was one of the servo wires had a nick in it and it would send erroneous signals to one servo and it would crash for no apparent reason
Don't know if this your problem but worth a look

[moejammin]

did you replace the servo or patch the nick

[moejammin]

I had the exact same thing happen on the maiden of my 500 super combo all stock parts. Hovering in normal then a few seconds after hitting the IU switch the bird slammed itself into the ground. I was using the gp790 though. Im kind of nervous to take it back up now that it is rebuilt. I thought it might be the esc so i got an 80 amp instead of the stock 70...

[moejammin]

Sorry to multi post but could a bad battery do this? I had two batteries one of them i accidentally touched the two polarities together and got a nice spark as i was soldering the connection. The other one i soldered up fine. I t flew fine with the pack i didn't f-up.Then on the next flight it committed suicide.