Blade Tracking
Last updated 2-29-2004

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What is blade tracking? If you look at the rotor disk from the side you should see a thin line. This means that both blades rotate around to the same position the other blade was in. If the blades do not align right then you will see a thick line or if bad enough you will see two lines. Some examples are shown in the picture on the right. The top image is of the blades in track. The middle is of just one side out indicating the flybar is bent, paddle not aligned, etc. The bottom is a typical out of track situation.

What do I adjust to get the blades tracked?
If you look at the picture on the left you will see the rotor head of a Raptor 50. I have colored the two links used to track the blades. These are the two long links going from the swashplate to the top of the rotor head. This will be the same for the Raptor 30/50/60/90. Technically for all helicopters the link you adjust in general will be the one that connects to the blade grip. On the Raptor this is called the double link. So why do I not adjust it instead... well actually I could. It would accomplish the same thing. I did some test a few years back thinking the geometry would become asymetrical if there was a mismatch between the long links and double links of each side. I measured the blade pitch at the top and bottom of the collective range with different configurations of the long link versus double link and it did not effect the range. So why do I prefer using the long link instead of the double link? I suppose it is just what I have become use to since these are the same links I use to do the alignment of the built-in pitch gauge. Most of the R30v1 ARF's where 5mm off to get the built-in pitch gauge correct and there was not 5mm of adjustment in the double links so you had to use the long links. Since I was always using these links for various alignments I just continue to use them to also track the blades and leave the double links at the factory 30mm setting.

So why do blades need to be tracked? Most of the time if the two blades are manufactured with close tolerances then they will not need additional alignment. However if one blade flexes more then the other or the blade has a warp in it then the purpose of tracking is to bring that blade in the same path as the other one.

First step: Before tracking the blades you need to have one side of the rotor head marked so your adjustments will be consistent. I usually scrap an 'X' on the top of one blade grip and also on top of the blade near the grip. In addition to using this so you can keep up with the link you are adjusting, you can also use this so if you take the blades off you can then get the blade back on the same grip and not have to re-track the blades.

Second step: Static tracking: this is the process of adjusting the pitch of each blade so they are the same on the bench. Almost all of the time this is the only tracking you will need to do. If it is wrong in the air then one of the blades must be flexing differently then the other and you will need to adjust the links to compensate. Start the process by sighting down the end of the blade and move the collective to a position that the tip of the leading edge and tip of the trailing edge are aligned with the flybar. Next I rotate the rotor head 180 degrees and sight down the end of the other blade. I adjust the long link attached to it so that that blade is also aligned with the flybar. This will now have both blades at the same pitch settings.
*Note: If you are working on a helicopter that has one blade way out of track then you need to figure out which one is correct. Lets say you have one blade labeled 'A' and the other 'B'. 'A' has a pitch range of -9 to 12 and 'B' has a range of -7 to 14 degrees. If you began the static tracking process with blade 'B' and you aligned 'A' to it then you would find your hover point is lower then it should be. If this happens then adjust both of the long links equally to get the pitch range back right. So in this example you would turn the link clockwise on both of the long links the same number of turns. On a Raptor I can easily figure this out by using the built-in pitch gauge and doing the alignment described on <
this> page.

Third step: Hover the helicopter and look at the edge of the rotor disk. Do not get to close to yourself. While looking at the blades it is easy to not pay attention to the helicopters position. It is a good idea to let a friend look at the tracking while you concentrate on hovering still. If the blades are out of track then land and look for the blade you marked. Adjust the link one turn, snap it back on, and check the tracking again. If it is worse then land and find the marked blade again and adjust the link two turns in the opposite direction. If one turn is not enough then go to the unmarked blade and adjust one turn the opposite direction. By rotating between one blade to the other you will keep your pitch range closer to the original range.

Troubleshooting: If you see the blades go out of track sometimes or you see one side of the disk is in track but the other side is not then you need to go to my troubleshooting page <here>.