Tail Pitch
last updated 3-18-2004

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Other gyro pages:
Gyro gain -
Gyro & Revo Mix -
Common Confusions -
Blades not straight when at center -
A common confusion about the tail pitch is that the blades should be straight when the stick is in the center. Instead they need a small angle as seen in the 'center' picture below. The reason is that the torque from the main rotor causes the body of the helicopter to rotate the opposite direction. In the case of the Raptor and all other helicopters with a clockwise rotating main blade, the body would be forced in an anti-clockwise direction (nose moves to the left). So with no tail rotor (or one set to zero degrees) the helicopter will rotate left very fast. So during hover you need some pitch in the tail blades to counteract the torque and keep the helicopter from rotating.
Left Center Right

Less blade pitch to left then the right -
After reading the paragraph above this brings up another question which is why is it that the tail pitch does not have an equal number of degrees travel to the left as it does to the right. As you can see in the 'left' and 'right' pictures shown above, the tail blades have a lot of pitch at full right stick but not much at full left stick. This all goes back to the above mentioned torque from the main blades. The helicopter is assisted by the torque when going left so it only takes a few degrees to send the helicopter spinning very fast. When rotating the helicopter to the right it takes a lot more pitch because you are going against the torque.

Direction of tail blades -
Another thing to note in the pictures above is it shows the direction the pitch slider and blades for both left and right stick commands. I often find this setup backwards by new pilots. At full right stick the tail slider will be near the tail case. At full left stick the slider will be close to the blades. Also note the direction of the tail blade. The blade pointing toward the back needs to have the thick side (leading edge) of the blade pointed down.

Center position -
The best position to start with for tail centering is to adjust the rudder link so that you have 4.5mm between the pitch slider and the tail rotor casing with the collective stick centered up/down and left/right.

NOTE: Here is a great tip that Lenny Nimmerrichter sent me. Instead of measuring the 4.5mm gap on the tail to center it, just align the tail control lever so that it is parallel with the tail shaft.

For more questions about the tail related to gyros such as 'why does the servo reach the limit before the stick is all the way to the side?', 'why does the servo not return to center?', and more. Go to these pages:
Gyro Confusion
How gyro gain/mode works
Gyros and revo-mix
Gyro setups

Steps to check for the correct directions of the tail system

Here are the steps to figure this out, please don't skip any, check each even if you know you have checked them before. I have found many times weird problems are only strange because you assumed something was right and did not check it in detail. Been-there-done-that <grin>

First check for correct assembly of the tail rotor: Stand on the right side of the helicopter looking at the tail rotor. Rotate the tail so that one blade is pointed straight toward the front. The leading edge of the front blade need to be pointed up. The blade grip arm for that blade also needs to be on the top. Rotate the tail rotor so the other blade is point to the front and check it also.

Check that the belt is the right direction:
Rotate the main gear so that the main blades spin clockwise (as viewed from the top) the tail needs to rotate counter clockwise (as viewed from the right side of the helicopter). If not, then when you installed the belt you did the 1/4 turn the wrong direction.

Check radio/gyro:
Move the rudder stick to the right, the control rod for the tail should be pulled toward the front of the helicopter. Next pick up the helicopter by the rotor head. Grab the tail boom and quickly rotate the helicopter so the nose goes to the left. Watch the control rod, it needs to move forward. If it does not then the gyro is reversed.

Check gyro mounting:
Replace the mounting tape if needed. The gyro should feel like it's on a cushion, if there is any slop then replace the tape. I use CSM tape on all my gyros.

Check rudder position:
With the rudder stick on the radio centered and the trim centered there should be 4.5mm between the pitch slider and the tail rotor casing with the collective stick centered up/down and left/right.

First crank up the helicopter and verify the engine is not turning backwards. If the engine is turning backwards, the tail will spin full time, also as you try to lift off, the main rotor will not turn (unless the clutch is broke). Get the heli light on the skids (not off the ground) and give a small right rudder command. If the nose goes to the right and it rotates at the corresponding speed then try going to left. If it does go left then you are set to go.