Tail servo bad?

[scgeek12]

Hey everyone I just joined HF (have been getting info off of it for a while now tho lol so thank you! ) I am flying a Trex 450 RTF (first CP heli)

Anyway I think I have a bad tail servo and was trying to get some advise before I replace it... I was out flying the Trex 450 today and just hovering in idle up mode about 5 feet off the ground practicing some nose in hover and the heli just went crazy, the nose pitched straight up into the air and it turned onto its side and just fell out of the sky... the only mechanic thing I have noticed different is the tail servo is WAY stiffer then it was before in both directions (I disconnected it from the tail pitch assy and it was the same...)

Also, now that this has happened I can not for the life of me get the heli bound to the transmitter again when I plug the heli in the Ch1 servo goes straight up in the air, the CH2 goes straigh down towards the gear, and CH6 goes to about the middle... if I let is sit for a few seconds it will bind and the swash "jumps" 3 times and it levels out but then after about another 2-5 seconds it looses signal again and the servos go in opposite directions again, I have tried holding the button on the flybarless controller like the manual says to get it to bind and nothing happens....


Any help would be greatly appreciated!!! if I missed any important info sorry Ill add it as needed (really new to helis ... well RC in general lol)

[HeliMadMarcus]

Hi scgeek, depending on your rx, you'll need to use the bind plug in the correct port, once your rx is flashing then you hit that bind button on your or whatever instructions your manual gives...with my mcpx it was bind button and right rudder.. The problem you're having with the servos moving after initializing could be down to your fbl unit or (gyro) being set up incorrectly..
For instance the system being mounted incorrectly to the information that it has been set up with, go through the gyro setup again to make sure, and if it's still not working download the event log and see what it says.
Another thing to add is my heli did the same thing as yours, uncontrolled crash in the air, basically my system re-booted because my esc wasn't up to the task and cut out, so the rx also cut out...i now have a ubec bec which is a much more efficient way to power the rx.

As for the servo it may be damaged servo try giving this a read. Could be many things you can try before buying a new servo.

http://www.rcgroups.com/forums/showthread.php?t=815782

[Dan MacKay]

Hi scgeek,

Conducting post mortums are always some what difficult as you have to try and sort out what caused the crash and what was just damaged as a result of the crash. In this case from what you described just prior to the crash I would think that the tail was not an issue as tail problems would be indicated as a shake or uncontrolled piro's.

I am always suspicious of blaming electronics first as it has been my experience that machanical failure is far more likely which will in turn make it appear like an electronic problem. For example a mechanical failure in the head such as a cyclic link popping off will cause the gyro to go nuts trying to compensate for something it cannot...a nose up roll over to the right is quite likely as that is the gyroscopic progression direction of the main rotor.

As for trying to figure out what is wrong, start with the basics and work your way up. Unplug everything from the RX, plug in the bind plug and bind it to your TX using a separate power supply. If that works, make sure you remove all links, move onto one servo at a time to make sure they work and have full travel with no hitches. If the servos work plug the gyro and make sure the indicator lights indicate appropriately. If it does then your electronics are **probably** ok.
Now what you need to do is go through everything top to bottom to make sure you are mechanically correct replace what you need to paying special attention to the feathering shaft, main bearings and tail rotor shaft.
Attach servos, do final setup, remove the blades, secure to the bench and spool up to make sure all is vunderbar. Then you should be good to go.
One thing you did mention was that this was an RTF heli. Did you by any chance do a complete tear down and reassembly using loctite 43 where required. It is very rare that an RTF that comes completely assembled is actually assembled properly. As you said that this is your first CP heli I cannot stress how important attention to detail during maintenance is. There is a very big difference between planes and heli's. A plane wants to fly while a heli does not and is just looking for an excuse to shake itself apart.
Good luck with your troubleshooting.

Dan