Mcpx BL Tail Blowouts

[Hawke]

Hi, I've been having tail blowouts with my mcpx bl. It started when I cracked the frame slightly where the tail attaches making the tail loose and able to wobble and twist during flight. I assumed this was the cause of the blowouts but replacing the frame and tail hasn't resolved it, it's no where near as bad as it was prior to the repair but the blowouts are still there.

If I punch the pitch during a hover the heli will react as if I've also added left rudder but it will correct itself and straighten up again after a second. If I do a loop most of the time it will come out of the loop 45 degrees to the left of where I entered and if I do continuous loops it eventually circles its orientation back round to where it started. It definitely wasn't acting this way before, I could loop it continuously practically on the spot and it's orientation would hold but now if I try that it's orientation changes on every loop.

The swash is level and pitch is zero at midstick. I get the blowouts with a KDBB tail blade and also with the stock tail blade. New batteries haven't resolved the problem either and it happens with both the stock and nano-tech batteries. I've tried adding a MH solid main shaft as the stock shaft was causing slight vibes but still no joy. The feathering shaft is straight and main blades were balanced out of the box and needed no adjustment. The tail fin will buzz when it's in stunt mode, it's a new fin on a new tail and it's not loose, is this buzzing normal?

Also, I've noticed on a couple of occasions that after only a slight contact with the ground the heli will sometimes react as if the tail has become unplugged completely and just spin. It happened twice today, I was hovering a few feet off the ground and a bit of wind sent it down, by the time I'd added more pitch the heli bumped the ground slightly and on it's way back up the tail stopped completely causing the heli to spin. Luckily I was able to rescue it and land it both times without it tipping over so there was no damage. I could see the tail was still plugged in fully at both ends and it worked again immediately afterwards as if nothing had happened. I'm not sure if the contact with the ground was the cause or if the tail blade caught a bit of long grass but there was nothing wrapped around the tail blade or motor afterwards.

Could this all be a sign that the tail motor is on its way out?

[djandyling]

Hi, I had a similar problem with my tail on the mcpx bl, in that the tail would stop spinning and the heli would spin. It didn't happen every time but at least once a flight, also the tail was not holding as it used too. On closer inspection I noticed that one of the small wires going actually into the tail motor was loose, so I replaced the tail motor and it sorted the problem.

Worth a look.

[Hawke]

Thanks, I've taken a closer look at the tail motor but it all appears ok, there are no loose wires and I've moved the wires around while it's running in my hand to make sure and I can't replicate the tail motor cut out.

There is still a slight vibe that I can't pinpoint that occurs when it's running at low rpm (spinning up or spooling down) and the tail fin vibrates when it's at 100% throttle. If these vibes aren't normal they could be the cause of the loss of tail hold. Does anybody else get these vibes too?

[Hawke]

After replacing the tail motor it still isn't any better. I've got no idea what causing these blowouts. I've got a brand new frame, tail, tail motor, tail rotor, main gear, skids, main shaft, canopy & fin on it. It should be perfect, I just can't pin down the cause. Any suggestions on what could be causing this would be greatly appreciated.

Does anybody else get vibrations when it spins up and spools down and a buzz in the tail at 100% throttle?

[rapidgaz]

Hi. Are your main blades really loose is so tighten a wee bit. Also some if these mcpx have bent main shafts from the off.

[Hawke]

I tried tightening the blades as they were a little floppy but no joy. I've got a brand new MH solid carbon main shaft on it as the stock shaft was a little off.

While I was out testing it today there were a few occasions where it felt like the motor was bogging as I'd hit full pitch and it would sometimes take a few seconds before the heli reacted fully. Has anyone experienced a main motor failure on these? And if so did you get blowouts too?

If people could tell me if they also get vibrations when it spins up and spools down and a buzz in the tail at 100% throttle it would be a great help so I can rule these out. Thanks.

[tomatwalden]

If people could tell me if they also get vibrations when it spins up and spools down and a buzz in the tail at 100% throttle it would be a great help so I can rule these out. Thanks.

I get tail buzz at 100% - however my mate's heli doesn't. I don't get blowouts, but then I'm using the Lynx 42mm tail blades and have found them to be more effective than stock.

MCPX BL Upgrades

[Hawke]

I get tail buzz at 100% - however my mate's heli doesn't. I don't get blowouts, but then I'm using the Lynx 42mm tail blades and have found them to be more effective than stock.

Thanks. I'm using KBDD Tail Blades as they improve the 'normal' tail wag that all of these helis have but I get tail blowouts with these and the stock tail blades too. The blowouts only arose after I cracked the tail & frame making the tail loose and able to wobble but after replacing these parts the blowouts are still present. The tail hold was perfect prior to this but now it's just frustrating to fly as I can't predict the orientation it's going to be in when it comes out of a loop.

I've changed everything apart from the head, grips, blades, main motor, main shaft bearings, servos & mainboard. How long are these bl main motors supposed to last? I haven't had many flights on it as the servos don't even need cleaning yet so I doubt the main motor is the cause but I'm grasping at straws now...

Any help or advise is greatly appreciated. Thanks.

[tomatwalden]

How sturdy is the tail within the main frame? I changed mine to the solid carbon boom which was never quite a snug fit. I put some hot glue around the join and that improved things considerably. Other than that, perhaps try different throttle values, or you could try reducing the maximum pitch travel in servo setup (say from -90% to +90%).

As far as I know, tail authority issues with motor-driven tails can be caused by the main motor drawing too much power, lessening the current to the tail (hence my suggestion to use a lower throttle value). Are your LIPOs healthy ?

[Hawke]

How sturdy is the tail within the main frame? I changed mine to the solid carbon boom which was never quite a snug fit. I put some hot glue around the join and that improved things considerably. Other than that, perhaps try different throttle values, or you could try reducing the maximum pitch travel in servo setup (say from -90% to +90%).

The tail is tight into the frame and doesn't come out easily or twist. I also tried the solid tail too and found it didn't fit the frame properly so I'm using a brand new frame and regular hollow tail which fit together just as well as they did out of the box when the tail hold was perfect. I guess I could calm it down in the tx but it flew great out of the box aside from the wag and I really want to get it flying like it should. I'll give it a shot though and tame it down a bit to see what happens, thanks.

As far as I know, tail authority issues with motor-driven tails can be caused by the main motor drawing too much power, lessening the current to the tail (hence my suggestion to use a lower throttle value). Are your LIPOs healthy ?

I brought some new batteries as I thought they were probably the most likely cause when a new frame and tail didn't fix it but new batteries didn't resolve it either. Can a failing main motor draw also too much power and cause blowouts? Has anyone experienced a failing mcpx bl main motor?

[parksy]

Hey Hawke, have you checked the tail wire pins going to main board? I put a little kink in mine to give better connection in socket. Could be dodgy main motor, but bogging is prob more to do with excessive pitch, they aren't massively powerful motors as stock. If you fly in normal mode with linear pitch and throttle, motor will struggle to accelerate and push more pitch at the same time. Once off the ground, switch to idle up/stunt with a throttle curve of 80-80-80-80-80, keep pitch 0-100 if you used to it or flatten it down if you just hovering around. If the motor is at constant speed it won't need the extra draw from a throttle up, so tail 'should' hold better.