Ok so you have your brand new
helicopter and you took it down to the park for a fly and it did not quite go as
planned and you can not figure out why. With this in mind Z created this
One of the blade pitch rods is slightly longer than
Possibly a bent or damaged shaft.
Paddles that are not level or not
because they're parallel does not mean they are level.
Damage thrust bearing in the blade grips.
Helicopter Gradually Pulls Up in
Helicopter Gradually Dives in
Helicopter is Pitchy, Rapidly Pulls
Up and Down
Uneven Tracking while Performing
High Rate Yanking and Banking
There are only a few systems that can cause a "low speed"
shake. (5 - 30Hz) Low speed shakes are the most scary
because it looks like it might explode.
Misbalanced rotor blades.
Non tracked rotor blades.
Blade grips that are not evenly spaced from the
head, or have slop in them allowing the blade
grips to shift laterally more than .5mm.
Flybar paddles are not exactly the same
distance out from the center when the paddles are
screwed in the same number of turns.
A bent flybar or spindle.
A bent main shaft. Unfortunately the only way to
tell if it's bent is to remove it and roll it on glass.
A damaged head.
Excessive slop in the mixing arms possibly.
Warn out rubber dampeners.
Training gear can amplify a otherwise
imbalance into a scary violent shake. You can usually
cure this by running a different head speed and or
changing the length of the training gear and how
securely or loosely they're fastened to the landing
There are also only a limited number of things that can
cause a "high freq shake." (100-300 Hz) High frequency
vibrations are most evident by a hum sound coming from the
canopy, blurred stabilizer fins, and or foamy fuel in the
Engine vibrations or bent crank shaft.
Damaged or unbalanced clutch or clutch bell.
Cooling fan not balanced.
Bent start shaft.
Resonating tail drive shaft.
Tail blades unbalanced or not tracking.
Tail mast or hub bent.
Damaged pinions or gears.
There are many causes of radio interference and lockout.
If you just have plain FM, radio hits will manifest
themselves as control jerks and spasms. If you have PCM your
controls will just stop responding and move to your pre-programmed
positions. Usually with a helicopter this is all servo's maintain last position
and throttle to idle.
Antenna touching something metal.
Metal to metal screws that are
Any loose metal to metal connections that can rattle
Bad bearings that are noisy or otherwise
TV channel interference from a
A receiver that is not sufficiently insulated from
Antenna is too close to electronics. Try to avoid
other wires, servo's, governors and gyros as much as
Grease any bearing that's supposed to be greased.
Usually just in the tail gear case.
Make sure if you can, that you're not flying close
to another field where people might be on the same
Loose connections inside your receiver (maybe from a
previous crash) or any other leads to servos or a loose
frequency crystal in the receiver.
Low battery power on the receiver or transmitter.
If you point your antenna directly at the helicopter
it has the weakest signal. 45 degrees in any direction
from the tip of the antenna has the strongest signal.
If you have a short whip antenna, take special care
to avoid mounting it near other electronics and that the
electrical connections are very secure.
Tail Jerks (Non radio related)
Sometimes your tail wags, jerks or spasms randomly from
time to time. Here are some things to check for....
The gyro might be too sensitive for very high rpm's
like those experienced when descending or the
"weightless parts" of aerobatics. Also, fast flight
makes the tail more sensitive so you might get tail wag
if you're going faster than usual. You'll just need to
decrease your gain 5%.
Gyro mounted poorly. Avoid mounting a gyro in a
manor that waging will be able to wobble the gyro along
the vertical axis. Don't use the side of the gyro to
mount it to a vertical section, use the base of it on a
Use the gyro tape supplied with the gyro, or material
designed for gyro's.
Bad high frequency vibrations and interfere with the
electronics of a gyro and make it work poorly.
If you have a belt drive make sure the teeth on the
belt aren't hitting inside the boom, which can happen if
your belt is too loose.
If your engine is running too lean it can sputter
which will cause sudden loss of tail power, or sudden
burst of tail power which will "kick" the tail around.
This could be a warning sign that your drive shaft
is loose, slipping or backing out.
This is also a good indication you're running low on
gas, or sucking up air bubbles from fuel intake.
Many times the tail is the most sensitive part of
the helicopter, so radio hits may be mostly noticed in
tail jerks. See the above for troubleshooting radio
Perhaps your belt, gear or pinion are missing teeth
or have damaged (rounded) teeth which are skipping.
Check the clutch area, main gear and tail gears for
rounded or missing teeth.