Tracking RC helicopter blades: a step-by-step guide

"Tracking" is the term for the blades of a helicopter rotor following each other through the same plane. When they track perfectly, the rotor disc is a single flat circle. When they do not, one blade flies slightly higher than the other and the rotor disc looks like a saucer with the top wobbling. Off-tracking blades cost you altitude, eat battery, vibrate the airframe and — if bad enough — make the helicopter genuinely unsafe to fly. Twenty minutes with three strips of coloured tape will fix it forever.

What causes off-tracking

Three things, in order of how often they happen:

• The pitch link rod ends are not the same length — even by one turn of the rod
• The blade-grip bearings have play that lets one blade ride slightly higher than the other
• The blades themselves are different weights — manufacturing tolerance or one blade absorbed water/oil

For 95% of cases it is the first one, and that is what we are going to fix.

What you need

• The helicopter, fully assembled and ready to fly
• A roll of bright contrasting electrical tape (red and blue is the classic choice; yellow and white works too)
• A safe outdoor or indoor space where you can spool up the rotor at idle headspeed
• A 5mm flat-blade screwdriver or similar (for pitch-link adjustment)

If you fly outdoors and there is wind, do the tracking check indoors or wait for a calm day. Wind will tilt the rotor disc and make the difference between blades hard to read.

Step 1: mark the blades

Cut two short strips of tape, one of each colour. Wrap one strip around the tip of one main blade, and the other strip around the tip of the other main blade. Use the very tip of the blade — within the last 2–3mm — so the tape is visible against the rotor disc when spinning.

For three-bladed heads, use three different colours. For a four-bladed head you can pair colours (red+blue versus yellow+green).

Step 2: spool up at hover-low headspeed

Place the helicopter on a flat surface in the centre of an open area. Stand back ten metres or so — far enough to see the rotor disc edge-on, close enough to read the colours clearly.

Power up and bring the throttle to about 40%. This will not lift the helicopter but will spin the rotor at about three-quarters of hover headspeed. The reduced speed is important — easier to see, lower risk, more time to correct.

If the helicopter starts to wobble unstably at this throttle, stop immediately. The issue is probably more than tracking and needs investigation before going further.

Step 3: observe the disc

Look at the rotor disc edge-on, at eye level. You will see two coloured stripes spinning in the disc. There are three possible outcomes:

• One stripe — both colours overlap perfectly in the same plane. The blades are tracking correctly. You are done. Tape off, fly.
• Two stripes, clearly separated — one blade is flying noticeably above the other. Tracking is off. Continue to step 4.
• One stripe but appearing thicker than expected — slight tracking error. Acceptable for casual flying; fix it if you want optimal flight.

Step 4: identify which blade is high

Looking edge-on you will see the colours in vertical sequence. The blade that appears higher in the disc is the high blade. Note its colour.

If you cannot tell which is higher because they are too close, repeat at slightly higher throttle. The faster the rotor spins, the more exaggerated the tracking difference becomes.

Step 5: adjust the pitch link

Power down. Wait for the rotor to stop completely.

The pitch link is the thin metal rod connecting the swashplate to the blade grip. It has a threaded end with a ball-link socket. Adjusting the length of the rod (by turning the rod ends) changes the pitch of the corresponding blade.

For the high blade, you want to shorten the pitch link by exactly one full turn. This reduces the pitch on that blade and brings it down into the same plane as the other.

The mechanics of doing this:

• Unscrew one ball-link socket from its ball (use a ball-link plier or just lever it off)
• Turn the rod end by one full revolution (clockwise to shorten on most threads, counter-clockwise to lengthen)
• Click the ball-link back onto the ball

Some helicopters have left-hand and right-hand threads on the same rod (turnbuckle style) — check the manual if turning seems to do nothing.

Step 6: re-test

Power up to the same throttle as before. Observe the disc again.

If the high blade is now low, you overshot. Lengthen the pitch link by half a turn. If the high blade is still high, shorten by another half turn. Iterate by half-turns until the two stripes overlap into a single disc.

Most adjustments need one to two iterations after the initial full-turn change. The whole process from first observation to final perfect tracking is usually 15–25 minutes.

After the fix

Once tracking is correct, the helicopter should:

• Hover with markedly less vibration through the airframe
• Use slightly less throttle to maintain altitude at hover
• Sound smoother — less of a "buzz" in the rotor noise

Vibration is the biggest functional improvement. A properly-tracked helicopter is significantly less stressful on every other component: servos, head bearings, flybarless gyros, even the receiver antenna.

When tracking is not the issue

If you have followed the steps and the blades still cannot be brought into the same plane, the underlying cause is mechanical, not tracking adjustment. Possibilities:

• Bent main shaft — common after a hard landing. The shaft itself is no longer straight. Replace it
• Damaged blade-grip bearing — play in the bearing lets the blade flex up and down independently of pitch input. Replace the bearing
• Damaged blade — one blade is bent, cracked, or has absorbed water. Replace both blades as a pair (always pairs, never one)
• Worn ball-link sockets — the pitch link rattles in its socket and changes effective length under load. Replace the ball-link

Any of these requires actual repair rather than just adjustment. Address the mechanical issue first, then re-track.

How often to check

After every hard landing or crash, even if the helicopter "looks fine". After any work on the head — blade replacement, swashplate adjustment, servo replacement. Once a season as routine maintenance. After a long storage period (a winter in the loft can warp blades).

Twenty minutes of routine tracking maintenance saves hours of trying to diagnose unstable hover or wondering why a battery only lasts four minutes when it used to last six.