No reason for losing control

[Thedogsbollox]

I recently rebuilt my Blade 400 and for piece of mind, i gave it over to my model shop for them to check over.
Their guy flew it and apart from a little trim adjustment, it was fine.
I flew it myself in my local park and was hovering nicely for about 2 minutes then the heli suddenly lurched to the left(cyclicly, not rudder like) and i managed to correct it and power up to avoid the ground. Got it levelled off but now 20ft in the air. It gave another lurch to the left and kept going, i couldn't correct it. Ground did the rest. I couldn't think what caused this. Transmitter batteries were fine, heli battery was fully charged and had only been flying for about 2 minutes. No waggling from the tail. Haven't stripped it down yet but a crash usually results in the servo gears being stripped, so i won't be able to tell if that caused the instability.
Any suggestions?
Tony

[Thedogsbollox]

Before anybody states the bleedin obvious, No, It wasn't a gust

[pgkevet]

you're probably right in assuming servo gears/arm/wiring being at fault

[shades]

sounds like the servo gears were stripped to me

[johnsandywhite]

sounds like the servo gears were stripped to me

Yes. I had this with my Twister 3D Storm that I failed to notice after a rebuild. New servo fixed it.

[Sesame]

could be gears, also check the wiring very closely. I just had a lucky escape with my 600 one of the wires on my elevator servo had broken at the plug end I didnt notice because the sleaving was still attached, so I ended up with this intermitant fault, luckily I had only just taken off and managed to get it safely down(really really lucky), and way back to the point, I checked it at the field and couldnt see anything obvious, it was only when I got home and checked thoroughly that I found the problem, so take a real close look.

think ill be checking all my wiring very closely on all my models just in case. good luck

[cjcj1949]

You could have a dodgy connection inside the servo. Although as its a CCPM head no servo does roll on its own. A single servo either side of the heli would give roll and up or roll and down depending on if its right or left. I had one on my Twister that was fine below hover speed then just above hover speed it went full rotation with no control and smacked the blades into the boom. I found it by taking the blades off and spooling up on the ground. Fitting better servos is a popular move. Either Hitec HS65HBs or MGs or the TowerPro MGs for about £6. Tiddler is a fan of them and I have one to check out. I would definitely run a few batteries through without the blades on. Keep the revs down though to normal levels.

The dodgy connection tends to be where the wires connect to the little pcb. There's a point where the flexible wire meets the inflexible solder and unless the flexible wire is glued to the pcb it can vibrate and break.

[Thedogsbollox]

Thanks guys, will get her stripped down and investigate thoroughly. Is it possible to get metal gears for the stock servos?

[cjcj1949]

Yes. They come in a black box.

Modelaccessories.co.uk TowerPro MG90

[Thedogsbollox]

Very good. May go that route ok. Been told the stock gyro aint up to much either, what would be a good alternative. Not top of the range but with better control.

[scoobystig]

Very good. May go that route ok. Been told the stock gyro aint up to much either, what would be a good alternative. Not top of the range but with better control.

plenty of second hand Futaba 401's or Align GP750 about for £40.00 or so, also the CSM420 would be fine on the heli
if you want to spend a bit more, look out for a Spartan quark £60-£70ish

[cjcj1949]

There are new gyros from phoenixtech that people think a lot of GT9's and 90s. The stock gyro is ok in rate mode so long as it doesn't get too cold. Look for SMM or MEMS in the info. It means it should be temperature stable. If you don't have problems with the gyro then don't change it. It will make your flying more difficult, but you'll know how to control the tail and react to the unexpected. It tends to happen quite a lot. If you power up in heading hold then switch to rate mode you'll stop any gyro from building up errors. Then switch into hold as the heli is spooling up. The tail tends to drift when the heli is on the ground and not able to respond. If you do nothing about it you can get full left or right rudder at takeoff. I tend to fly the heli on the ground to correct for the slope on the takeoff area and to make sure that everything works ok. This is not a good idea for flybarless though.

[johnsandywhite]

This is not a good idea for flybarless though.

Definitely NOT. FBL likes a nice smooth and level surface for take off and landing. Which our site is NOT.

[tiddler]

Yes. They come in a black box.

Modelaccessories.co.uk TowerPro MG90

Or these..... Towerpro MG90s 14g 2.2kg Torque Ball Raced Micro Servo

Got these on my 450 pro, and their brilliant

[bikerflier]

Excellent gyro here.
http://www.rcheliaddict.co.uk/sale/63617-futaba-gy520-heading-hold-gyro.html

I've got a ready to fly 400 and a large box of spares if you are interested.
PM me for details.