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Old 10-05-2016, 07:48 PM   #92 (permalink)
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Join Date: Mar 2013
Location: Granite Falls, WA - USA
Default Tail problem terminology & common causes for V977 & K110

This is just a quick guide, maybe somebody else could give a more complete definition & repair guide or point to a good heli glossary of terms. Note that Tail Kick is the most common tail problem with the V977 and less of a problem on the K110. Tail Blowout, Tail Wag and Tail Hunting are rare on the V977 & K110. Brushed tail motors like on the V977 and K110 will wear out and lose power. They may need to be replaced several times a year if you fly a lot, especially if you overheat them by not letting them cool between flights.

Tail Kick: When the tail kicks out a few inches and then returns to it's original position. This is usually happens during fast collective pitch changes and is because the tail motor is under powered, tail rotor is undersized or sometimes because it is tuned incorrectly on tune-able flybarless systems. A short term solution to the problem is to reduce the total collective pitch. This does make the heli more predictable but it limits the maximum performance of the heli. It's best to mechanically improve your tail system: solid tail boom, bigger motor, correctly sized tail blade. For the V977, installing a K110 tail motor and K120 tail rotor are a big improvement. The K110 tail motor will fit in the V977 tail motor mount. For the K110, installing the K120 tail rotor blade helps.

Tail BlowOut (TBO): It's like a tail kick, except more pronounced and it does not return to it's starting point. Tall blowout can often cause the tail to be 90 to 180 degrees off from where it is supposed to be.This happens with aggressive pitch changes or aggressive 3D stunts, and often results in a crash because the heli suddenly points the wrong way. TBO is almost always because of a weak or undersized tail motor or tail blade. It can also be because of a cracked tail boom, cracked tail blade, tail blade slipping on the shaft, flaky solder joint on the tail motor wires or possibly a bad tail motor FET on the main board.

Tail Wag: While hovering or flying sideways the tail oscillates back and forth a few inches like a dog wagging it's tail. Often the result of side wind, cracked tail boom, or poorly tuned flybarless system where the tail gain is not set correctly. Tail gain is factory set and non adjustable on the V977 and K110.

Tail Hunting: I have seen this term used to describe the situation where in a hover the tail seems to just slowly keep changing positions like it's lost. Usually caused by excess vibrations or bad gyro chip.

Note: all of the above can also be caused by excessive vibrations as vibrations can cause almost any unpredictable behavior. A chipped main blade or bent feathering shaft is the most common cause of vibrations.

Edit: I incorporated some of JWeber's tips from the post directly below, make sure you read it.
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Last edited by BirdBarber; 10-06-2016 at 05:10 PM..
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