Smashed Heli

[agh321]

Just recently set up another Trex 700 nitro ar8000rx with spirit pro brand new 3000 mah life
and after a 7min flight in ide2 I came in to do some nose in hovering and after 20seconds the Heli reved up and slammed into the ground
when I went over to the Heli it was at tick over and all the servos were working fine I’ve checked the switch and power supply and can find no fault

so what should I do next

change receiver

change flybarless unit

change the life battery

I don’t want to fly again with the current set up until I know what went wrong

[waveydavey]

It would be unlikely that a power failure would cause it to slam into the deck, IE add negative pitch whilst you were upright. You've got to be looking at radio and fbl unit I would think, you were upright?

[Ade_Law]

could be any number of things, bad switch, intermittent connection in the battery (spot weld tab loose) or a RF failure of some sort.

a little more description on exactly what happened will be useful and help narrow it down.

time scales from when it reved up to when you lost control to when it crashed,
how it crashed, did it suddenly shove itself into the ground or did it fall over sideways sliding into the ground,

Do you have telemetry? Do you have the battery voltage and RSSI logged?

What happens if you bring the collective up to middle and switch off the transmitter? Does the throttle go to idle?

Ade

[agh321]

I had a 7 min flight in ide up 2 and came in land to check how much fuel was left in the tank
After taking off again I was in normal throttle 40% upright and had just done a nose in
figure of eight And while facing me it seemed to go into ide 2 and neg pitch and slammed into the ground
up

[agh321]

Just rebuilt the Heli with the same electronics and everything is working as it should
I just can’t find the fault

[Ade_Law]

ok I have seen something like this before....

switch the model on, not in throttle hold, raise stick to the top. check that you have full collective and full throttle,

switch transmitter off,

what does the throttle and collective do?

Ade

[terhoutd]

And while facing me it seemed to go into ide 2 and neg pitch and slammed into the ground
up

This really looks like a failsafe to me... Check on the bench whether failsafe triggers idle up 2 and full neg pitch. And if its the case, then it must be indeed the failsafe. Meaning you lost RF signal for some reason.

[atomiccomp]

Where have you got your radio Ariels positioned? It's possible that when nose in your model was in a radio dead spot and went into failsafe.
I had the same issue with my 700n and I discovered that aswell as cutting the engine failsafe also triggered max negative pitch. In my case it happened tail in right in front of me and was repeatable and turned out to be
a faulty receiver.

Thankfully I got away with just a broken undercarriage.

[hedge]

...aswell as cutting the engine failsafe also triggered max negative pitch...

Very normal operation for Spectrum failsafe as the position the sticks are in during bind tends to be where the failsafe is set. So I add +1 to all the above and call it a failsafe issue.

[atomiccomp]

Very normal operation for Spectrum failsafe as the position the sticks are in during bind tends to be where the failsafe is set. So I add +1 to all the above and call it a failsafe issue.

Cheers, Although the setup I use is a Frsky taranis. I neglected to put the pitch at zero degree when I set the failsafe. Oops.

[Grumpy]

Probably I’m stating the blindingly obvious but to test the failsafe simply turn off the Tx and see where the servos go.
With electric this should be done with the blades off just in case failsafe goes to open throttle.

[barryorbik]

Good idea to take off the tail blades too, or if possible move the motor pinion well out of mesh, as if it does go to full throttle you will have a whirling dervish on your hands. How do I know? Well a chap at our club recently ended up in A&E whilst testing the (incorrectly set up Taranis) fail-safe on his new heli and they took a series of chunks out of his arm and fingers before he got free of it - not a pretty sight.

Barry

[agh321]

Thanks for all your help on this
I will have a look tomorrow