Flybar - checks and
last updated 4-29-2006

Back to Main Page

  
Symptoms: blades track on one side only, tracking changes in flight, tracking changes with cyclic input, helicopter pitchy in forward flight
If you have any of these symptoms then throughly check your entire flybar system. Start with step 1 and complete them all.
Step 1: check bearings This is often overlooked but is important. If the bearings are bad they can cause the blades to go out of track in flight. Take off the two oval links then rotate the flybar. If you feel any notchiness then replace the two bearings in the see saw hub. If it feels ok then simulate a load by picking upward at the control arms on each side of the see saw hub then rotate the flybar. Again, if it is not smooth then replace the bearings. Note: when using the technique above be aware that if the bearing is locked up then you will only feel the flybar slipping on the inside race. I remove the flybar then poke a straight automotive transmission pick where the flybar was. I can easily rotate the inside race and feel if the bearing is bad with this. If the bearings are bad then it is most likely because the bearing holes in the ends of the see saw hub are too small. This causes a high pre-load on the bearings and can pit the races. If the holes are too small then you will find it very difficult to remove the bearings. The best way to remove them is to take everything off the see saw hub and place the hub in the oven. Pre-heat to 350F then cook for 10 minutes. Remove the hub then use a flat blade screw driver through the opposite side to knock the bearing out. Be careful, the hub will be very hot so only hold it with an oven mit.
Step 2: loose control arms I have found this more then a few times. If you can rotate the control arms (the L shaped arms beside the see saw hub) then this will cause the tracking to change in flight. Usually what I find is that the set screw in the control arm is stripped out. This is an easy fix since the metal hub in the control arm can be slid out, rotated 180 degrees and slid back in. This will let you use the threaded hole on the other side.
Step 3: flat sides This is another common thing I find wrong. The flybar has two flat spots located a couple of inches from the center. These flat spots are for the two set screws that hold the flybar control arms on. I often find many did not know this was there or just forgot while installing the flybar. If you do not get the set screws on the flat spots you could have it slip and loose the alignment you had.
Step 4: equal length The flybar needs to be centered in the see saw hub. You can use a straight edge ruler to measure from the see saw hub to the end of the flybar. Note that the hub has a stepped section on the end. If you place the ruler against the stepped section, do the same for the measurement on the other side.
Step 5: straighten The flybar can easily bend during transport. Place a straight edge ruler flat on the see saw hub and confirm the flybar is parallel. In the top picture you see that I placed the ruler on the tops of the set screw holes in the flybar control arms. While this should put the ruler parallel with the see saw hub do not assume it will. I look for an equal gap between the ruler and the hub first. Tip: One time I found that after bending the flybar up/down to get it straight I found the paddle was not straight. The flybar was bent just as it entered the paddle. So check that not only the flybar is parallel with the ruler, but also that the paddle is parallel.
In the picture on the right, you see the ruler placed parallel to the side of the see saw hub. This is to check for any side to side bends. Just like above, don't forget to make sure the paddle is also straight.
Step 6: equal distance to paddles If you are just now installing the paddles then use a ruler to make sure the paddles are an equal distance from the hub.
Step 7: Align both paddles with the ridge on the flybar control arm.
 It is important to understand the paddles not only have to be aligned with each other but they have to be aligned with the control arms. One time I had someone tell me their paddles were not the problem because they were perfectly aligned using the special purpose alignment tool they bought. I had to show them the tool they used did align the paddles to each other but neither were aligned to the control arms.

Note: the paddles have set screws that keep the paddles from turning. Make sure you loosen them before trying to adjust the paddles. If you do not then you will damage the threads on the end of the flybar.
The first step is to adjust both flybar paddles so that they are parallel with the flybar control arm. As you can see in the picture on the left imagine a line drawn from the leading to trailing tips of the paddle and that line should be parallel with the control arm.
Step 8: Refine the alignment



 To further refine the alignment you can sight down the flybar to confirm they are aligned. In the pictures on the left you can see the angle I look at. This position allows you to see the tips of both flybar paddles. Move yourself (not the helicopter) up or down until your line of sight is such that the tip of the paddle furtherest away from you is in the center of the flybar. You can move until you see the tip of the paddle opposite of you above the flybar then move until you see it below, now center yourself so the tip is in the middle of the flybar. Now that you have found the center do not move while you glance at the tip of the paddle on your side. It should be in the center of the flybar. If not then one (or both) of the paddles are not aligned to the control arms. If you followed the steps before this one then the flybar is straight and the control arms are parallel with each other. So you need to look again at the paddles and figure out which one is not aligned with the ridge of the flybar control arm. The paddles are often very tight on the threads and difficult to rotate small angles. Just keep trying, you will get it.
Step 9: Set screws After you get the alignment right, don't forget to tighten the set screws in the paddles to keep them from turning in flight.