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Troubleshooting Guide

 

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 Troubleshooting Guide.

 

Uneven Tracking

  • One of the blade pitch rods is slightly longer than the other.

  • Possibly a bent or damaged shaft.

  • Paddles that are not level or not symmetric. Just because they're parallel does not mean they are level.

  • Damage thrust bearing in the blade grips.

Helicopter Gradually Pulls Up in Forward Flight

  • The pitch in the paddles may be slightly positive overall.

  • The helicopter may be nose heavy.

Helicopter Gradually Dives in Forward Flight

  • The pitch in the paddles may be slightly negative overall.

  • The helicopter may be tail heavy.

Helicopter is Pitchy, Rapidly Pulls Up and Down

  • Need heavier paddles.

  • Add flybar weights.

  • 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.

Vibrations

 

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 harmless 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 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 coming from the canopy, blurred stabilizer 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-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 not loctite.

  • Any loose metal to metal connections that can rattle or vibrate.

  • Bad bearings that are noisy or otherwise damaged.

  • TV channel interference from a harmonic frequency.

  • A receiver that is not sufficiently insulated from engine vibrations.

  • Antenna is too close to electronics. Try to avoid other wires, servo's, governors 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 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 horizontal surface.

  • 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 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.

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