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Remote Control Helicopter Troubleshooting Chart

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 we created the Remote Control Helicopter troubleshooting guide. We hope you like it. As usual if you have some tips that do not appear here then please add you trouble chart tips and comments. We hope this helps.

Uneven tracking you should check the following:

  • One of the blade pitch rods is slightly longer than the other
  • Possibly a bent or damaged feathing shaft
  • Paddles that are not level or not symetric. Just because they're parallel does not mean they are level.
  • Damange thrust bearing in the blade grips

Helicopter gradually pulls up in forward flight check the following:

  • The pitch in the paddles may be slightly positive overall.
  • The helicopter may be nose heavy, yes - nose heavy.

Helicopter gradually dives in forward flight check the following:

  • The pitch in the paddles may be slightly negative overall.
  • The helicopter may be tail heavy, yes - tail heavy.

Helicopter is pitchy, rapidly pulls up and down check the following:

  • You may need heavier paddles
  • You may want to add flybar weights
  • If it's optional, move to the mounting hole closer to the leading edge of the paddle.

Uneven tracking while performing high rate yanking and banking:

  • Check that the center of gravity of each blade is the exact same distance out and that the blades are the exact same weight.
  • Check for excessive slop in the control linkages


There are only a few systems that can cause a "low speed" shake. (5 - 30Hz) Low speed shakes are the most scarey kind because the thing looks like it might explode or resembles a paint shaker.

  • Nonbalanced rotorblades
  • Nontracked rotorblades
  • Blade grips that are not exactly spaced from the head the same, or have slop in them alowing the blade grips to shift laterally more than .5mm.
  • A flybar who's 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.
  • Excesive slop in the mixing arms possibly.
  • A set of blades that don't have matched CGs (debatable) Matching the CG is different than just balancing.
  • Warn out rubber dampeners.
  • Training gear can amplify a otherwise harmles imbalance into a scarey 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 struts.

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 comming from the canopy, blurred stabelizer fins, and or foamy fuel in the main tank.

  • 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.

Radio Problems

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-programed positions. Usually with a helicopter this is all servo's maintain last position and throttle to idle. I'll list as many causes as I can think of.

  • Antenna touching something metal.
  • Metal to metal screws that are not loc-tited.
  • Any loose metal to metal connections that can rattle or vibrate.
  • Bad bearings that are notchy, noisy or otherwise damaged.
  • TV channel interference from a harmonic frequency. Channel 20 is bad around my area and channel 40 gets interference from the audio band of TV channel 4. Check your hobby stores for info.
  • A reciever that is not sufficiently insulated from eingine vibrations.
  • Antenna is too close to electronics. Try to avoid other wires, servo's, governers and gyros as much as possible.
  • 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 channel
  • 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 reciever 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...

  • Gyro too sensitive, although if you have to make it so unsensitive the tail is "slippery" this isn't the problem.
  • 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 verticle axis. Don't use the side of the gyro to mount it to a vertical section, use the base of it on a horizontal surface.
  • Use the gyro tape suplied 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 bubles 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 interference.
  • 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.

If you have more to add on this subject or want to read what the other pilots have to say the please click here to read more about RC Helicopter Trouble Chart.


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