Zoom 400 problem - Ran out of ideas, need help!

[Skeeter Pilot]

I've had a Protech Zoom 400 for over a year and it has had the same problem all the time. Virtually every flight it will suddenly drop the collective (not the throttle) very rapidly which results in the model descending about 12 to 24 inches. I still fly it a lot and just put up with it whilst continuing to try and find out the cause. It normally does it 2 to 5 times in one pack.

It is fitted with the Protech (blue) brushless motor, Jetti MPD 7 ch. r/x, Align RCE-BL35G e.s.c., Align Head Lock giro and Flight Power EVO 20 1800 mAh LiPo.

I have changed the motor, receiver, collective servo, speed controller, transmitter. I have not changed the LiPo's, but I have two packs and it does it on both, Giro - can't be this...can it?
I've fitted ferrite rings like they are going out of fashion and have re routed the antenna twice and still no change.

There is some side play in the Main Rotor Shaft, must be in the bearing themselves, could it be metal-to-metal?

Any clues please!!

[futura]

I've solved this problem by replacing the small rectangular piece that slide in slot in the shaft. The one the pitch rod screws into. Mine was getting worn and was binding at speed in flight.....was not noticable at all when checking on the ground.

If your still using Z bend connection rod from the collective servo to the pitch lever, you may consider using ball links or something with less possibility of also binding under stress.

Just a couple ideas....hope you find it. Like you've suspected, I think its a glitch most likely. Does it always loose altitude or does it gain altitude in the same manor.

[Skeeter Pilot]

It only effects the collective servo and always a 'snap' drop down.

[futura]

Here's an easy way to tell if its glitching from static buildup. Take a drier sheet from the laundry...one that eliminates static....or some spray antistatic for working on computers or making panty hose unstick from the back of your shirt. apply to the frame, boom, LG etc...carefully avoiding getting any on ball links and such. This will not eliminate the gliching for ever, put if static is your problem, you will eliminate the static for a flight or two. At least you will know its static causing the glitch.

[Skeeter Pilot]

Great advise, many thanks I'll give it a go.

All the best,
SP

[futura]

Guys with belt drive and CF booms use this as a standard preflight process to eliminate static buildup from the belt and boom. Best of luck!