Heli twitching to the left violently at 40% throttle

[TWE75]

Hi guys , after my last crash , i changed the rotor head assembly to original align parts , while the rest of my heli were cloned parts ( i'm using the flasher 450 sport ) . After that i notice whenever i increase my throttle to 40% , the heli will suddenly twitched to the left violently ( resulted in another crash ) . But luckily only the main blades were damaged cos the heli is still on the ground . After that i found that the nut locking the main shaft below the swashplate was loose so i tighten it , but today when i play , it still twitched violently to the left when it reached about 40% and above throttle . Oh yah and also i found some white dust sticking to the heli frame near to the main gears . I have tried to leave the throttle at 40% to monitor the twitching and found that once the throttle is at 40% and above , it will twitch intermittently .

Does anyone encounter this before ? Hope someone can give me an idea as to whats the problem with it .

[Adrianli]

What is twitching??? Is it like glitching???

What channel is twitching??? Alerions, elevator, pitch or tail???


Have u checked the servos???


The white powder is from the main gear. Could happen when u crash, the pinion eat into the main gear.

[vintcs]

try to disconnect the motor and move the throttle stick to the 40% and check that the swash plate is level and no adnormal movement on other linkages.

[daveth26]

I agree with our brothers. Check swashplate if level on centre sticks. Do throttle hold or take out main blades to be safe. Twitching sometimes implies gyro gain too high, you can slightly lower further to see if it wobble violently. Otherwise, do check the tail part also making sure the tail hub and tail blades are not loose. Especially when the nuts holding both ends of hub are often loose.
When blades rotate at clockwise highspeed, the body will counter anti-clockwise to hold the tail part, naturally going left in right proportions.

[remotemadness]

check all your servo wire if there is any cut..

[kelvinlow]

have u check the sensitivity of the tail servo gain ?

[TWE75]

Thanks guys for your suggestions , i will try all your suggestions today cos have been working . Hope i can solve my problem fast . Can't wait to resume my hovering practice after 2 months of neglect due to personal commitment .

[TWE75]

Hi guys , i just repaired my heli and found that remotemadness was correct , one of the server wires was exposed just outside the servo but not shorting anything though , but after changing all 3 to to HS 65MG servos , now all 3 servos for the cyclic goes up instead of down when i put the throttle at 0% and when i put it to 100% , all 3 will go down . I thought of reversing the throttle channel but i really worry that it may cause the motor to turn at 100% throttle when my throttle stick is at 0% .

Can anyone enlighten me on how should i reverse the 3 cyclic servos movement but yet the throttle for the motor remain untouched ?

[balance_mind]

Go to your swash menu and adjust the PIT to a negative value if the initial value is positive

[stickman]

There should b a collective menu in your tx that allow you to switch collective aerilon and elevator direction. Usually shows as a percentage. Just switch from like 60% to -60%.

This assume u are fly are heli, if fbl, consult ur fbl electronic manual.

Cheers

[Adrianli]

If u using futaba, use the Swash AFR in the menu to change from +50% to -50%, vice versa.

[vintcs]

alway disconnect the motor wires when doing setting...safety come first.

[TWE75]

Thanks bro , i believe i've solved the twitching problem , the new servos are not twitching a single bit when i throttle up to even 100% . Except that now one of my blades have excessive negative pitch and not enough positive pitch . Always getting stuck in this kind of situation . Is it due to my swashplate not truely level ? Cos i already used a swash plate leveling tool to tune my swash plate . Will try to adjust my swash plate again to see if it solves the problem .

Btw is a digital pitch guage better then a " manual " one ? Sometimes i tend to have some inconsistent pitch reading when i use the " manual " one .

[TWE75]

Is it ok to reverse my motor polarity to just let the main gear spin without rotating the main blades for discharging the lipo battery ?

And also don't know why the motor polarity had become reversed after changing my servos and main shaft . Originally the wires was like for eg: black to black , yellow to yellow and red to red . But now it is like for eg: black to black , red to yellow and yellow to red . But the heli still works as per normal though .

[misato]

only a few ESC can "soft" reverse polarity of the motor. Castle ones aside, quite a lot of these ESC uses stick input for ESC programming and it might be by chance, it was reversed during servo testing or the setting was "reset" to the original defaults somehow.

On getting the pitch gauge, a leveled swash doesn't mean the pitch will be the same. Most fly bar designs has at least 2 other link rod connected above the swatch plate that affects blade pitch. Often due to mechanical imperfection, the left grip link rods setting are seldom the same as the right one. Thus one possible cause of your unbalanced pitch. Unbalanced Pitch will cause tracking related problem and weird oscillation as the blades are spun around due to the differences in the thrust created by each blade of a different pitch.

For those using manual pitch gauge getting another person to verify the reading would be a very good idea. Read the pitch values against a very bright background helps a lot as well. Human eyes varies with your body physical conditions (such as lack of sleep, or use too much eye power, common after rushing to complete the setup of your heli), reading will varies quite a bit. Personally, I would double check the pitch setting again on the next day after a good night rest if not in a rush else let you eye rest a bit before verifying the reading in a well lighted environment.