MCPX Tail Blowout

[rbengines]

I have two MCPX. The first one flies great. The second one has never flown good. The tail blows out right from the start. I have the 120 tail on it now. Now the tail blows out when I idle up, but it did it with the stock tail also. It pulses in flight 90 degrees when I pump it. Odd thing is it turns clockwise. I think it's a bad board. Any ideas?

[Liduno]

Originally Posted by rbengines

I have two MCPX. The first one flies great. The second one has never flown good. The tail blows out right from the start. I have the 120 tail on it now. Now the tail blows out when I idle up, but it did it with the stock tail also. It pulses in flight 90 degrees when I pump it. Odd thing is it turns clockwise. I think it's a bad board. Any ideas?

From what I have read on this site, the 120 tail is too much for the stock motor and will actually increase tail blow out.

Try the stock tail and rotor with an extended boom and make sure you don't have too much pitch, too much pitch will bog the main motor which steals power from the tail.

The clockwise tail blow out has me a bit confused, maybe it's a vibration issue.

Check out this thread, it has alot of different causes for the 90 twitch.
https://www.helifreak.com/showthread.php?t=385069

[rbengines]

I would think that but with no input to the radio at idle up on the floor it twitches 90 degrees ever second are so. When I first idle up it holds for a second then starts.

[Liduno]

Originally Posted by rbengines

I would think that but with no input to the radio at idle up on the floor it twitches 90 degrees ever second are so. When I first idle up it holds for a second then starts.

I thought it was just when you did pumps, still check out that link I posted, there are alot of people with the 90 twitch and there are alot of different things that can cause it.

One thing that alot of people miss is a cracked main shaft, the easiest way to check with out having to take it apart is to hold the main gear and twist the head, if the shaft feels flexible then it's cracked.

[rbengines]

Thanks for the quick reply. It probably is the 120 motor.

[rbengines]

Originally Posted by Liduno

I thought it was just when you did pumps, still check out that link I posted, there are alot of people with the 90 twitch and there are alot of different things that can cause it.

One thing that alot of people miss is a cracked main shaft, the easiest way to check with out having to take it apart is to hold the main gear and twist the head, if the shaft feels flexible then it's cracked.

Have a video of it but I can't get it to post.

[Liduno]

Originally Posted by rbengines

Have a video of it but I can't get it to post.

The 90 twitch is well documented..lol

Check all the common vibration issues, then make sure you aren't having a connection problem, if the power to the main motor is being interrupted that will cause the tail motor to over compensate and send the tail clockwise.

If it's not any of those problems then you may in fact have a cracked board or some other board issue but check the easy fixes first.

Lube both motors and all the bearings, check to make sure your battery or motor leads haven't started to come loose, check to make sure the main shaft isnt cracked, make sure the main gear is properly installed and lined up with the flat spot on the main shaft, make sure the gear isnt binding, make sure you don't have a cracked blade.

I have also had a single battery that would cause the twitch, it worked fine in one heli but not in another, I suspect the plug just didnt jive with the plug on the one heli.

Those are the things I can remember off the top of my head.

[GeKu]

90 degree clockwise blow outs are classic symptoms of a bent feathering shaft. Check the feathering shaft too just to rule it out. Then try swapping a known good tail from your other heli to the problematic one and see if the problem is still there or vice versa. This way you can determine if the tail motor is an issue or not. Your results will either point you at a bad tail or a problem with the board.

[rbengines]

Originally Posted by GeKu

90 degree clockwise blow outs are classic symptoms of a bent feathering shaft. Check the feathering shaft too just to rule it out. Then try swapping a known good tail from your other heli to the problematic one and see if the problem is still there or vice versa. This way you can determine if the tail motor is an issue or not. Your results will either point you at a bad tail or a problem with the board.

Watch this video. [ame]http://www.youtube.com/watch?v=eUmPmQy-h5k[/ame]

[m3n00b]

Originally Posted by rbengines

Watch this video. http://www.youtube.com/watch?v=eUmPmQy-h5k

My buddy's does the same thing although not so often! Need to figure this out!

[GeKu]

Originally Posted by rbengines

Watch this video. http://www.youtube.com/watch?v=eUmPmQy-h5k

That's a good video. What steps have you taken so far besides swapping the original tail and motor with a 120SR tail?

[rbengines]

The thing is you are better off buying a new heli then paying the cost of a board. I've already bought two. I don't think my wife will go for three. This heli has done this since new. I guess I just got a bad one. With the tail mod I don't think HH will warranty it. Guess its a parts machine.

[rbengines]

Originally Posted by GeKu

That's a good video. What steps have you taken so far besides swapping the original tail and motor with a 120SR tail?

The video is bad because I had one hand on the camera and the other on the radio Spektrum 6i. I change the motor, the tail, check feathering shaft and main shaft. Leveled the swash, checked the positive and negative pitch. I would go back to the stock tail but due to the bad handling I have smashed three and am not going to buy another. It does the same thing in the air as on the ground. I hope someone finds the cure then maybe I'll repair it. The 120SR held great on my other heli.

[rbengines]

Almost forgot I tin the plugs with soldier to make sure of a good contact. Good luck with yours.

[GeKu]

I meant the video was good cause it showed us exactly what your heli is doing without inputs. If you swap the board to your good heli and do the same ground test then If it acts the same then you know the board is bad. Don't try flying it until you can verify that the problem isn't there during bench testing. If it ends up being the board I'm pretty sure Mega Stumbler would be able to fix it for you. How old is the heli? If it's pretty new then contact HH. They are really good with customer support but if it is a board issue and if they are willing to send you a new board, it is on BO until at least the end of the month. I've been waiting for a new board since Feb 15.

[rbengines]

I'll trade the boards out and see. They are both about a month old. I bought one and it flew great but I lost a lower bearing. The local hobby shop was out the bearings. I bought another because it flew so good and I didn't want to be out any flying time. It never flew like the first one. Didn't understand why when it went inverted it would go crazy. Now I'm down to the issue at hand. The first one still flys great. Just don't have a backup now.

[Liduno]

It's hard to tell from the video but does it sound to you that the main motor is cutting power for a millisecond when the tail twitches?

[Liduno]

Just changing the boards wont positively tell you that it's a board problem, some boards are more sensitive to a certain frequency caused by a vibration than another board would be.

A good way to tell if it's a frequency problem would be to isolate the board from the frame, just while it's sitting on the ground like in your video unscrew the board from the frame and make sure it isn't touching the frame.

[rbengines]

Originally Posted by Liduno

Just changing the boards wont positively tell you that it's a board problem, some boards are more sensitive to a certain frequency caused by a vibration than another board would be.

A good way to tell if it's a frequency problem would be to isolate the board from the frame, just while it's sitting on the ground like in your video unscrew the board from the frame and make sure it isn't touching the frame.

Not sure what you mean by isolate but here it is just hanging by wires.
http://www.youtube.com/my_videos_edi...id=_LoIpSwqcok

[rbengines]

Originally Posted by m3n00b

My buddy's does the same thing although not so often! Need to figure this out!

[ame]http://www.youtube.com/watch?v=_LoIpSwqcok[/ame]