RC helicopters ยท Fix
Blade tracking and balancing
By Paul Walsh Last reviewed
Vibration ruins everything on a helicopter: the gyro gets confused (see gyros and flybarless units for why), the flight feels rough, screws work loose and parts wear out early. The commonest cause is main blades that aren't tracking or balanced. Both are easy to check.
Tracking: do both blades fly the same path?
Check tracking
- Mark one blade tip with coloured tape (and the other with a different colour).
- Spool up to a light hover or just light on the skids, at a safe distance.
- Crouch so your eye is level with the rotor disc and look from the side.
- If you see one blade path, the tracking is good. If you see two, note which colour is higher.
Adjust tracking
On a collective pitch helicopter, the blade that's riding higher has too much pitch. Shorten its pitch link by a turn (or lengthen the low blade's link) and check again. On most flybarless heads, the links between the swashplate and blade grips are the ones to adjust. Make small changes, one at a time.
On fixed pitch helicopters, tracking problems usually mean a damaged blade or grip. Replace rather than adjust.
Balancing: do both blades weigh the same?
Spanwise balance
- Bolt the two blades together through their mounting holes on a blade balancer (or a bolt across two glasses).
- The heavier blade drops.
- Add thin tape to the lighter blade, near the tip, until they hang level.
Chordwise balance (centre of gravity)
Check that each blade's centre of gravity is the same distance back from the leading edge. Good blades are made matched; if not, tape along the edge corrects it. For most pilots, spanwise balance is the one that matters.
Other causes of vibration
If the blades are tracked and balanced and the vibration remains, check:
- Bent main shaft or feathering shaft. Spin the shaft and watch the top.
- Worn bearings, especially the main shaft and tail bearings.
- Main gear or motor pinion damaged.
- Loose screws anywhere on the head or frame.
- Tail blades damaged or unbalanced.
The RC helicopter troubleshooting guide covers these, and levelling the head is in swashplate levelling.
Tools that help
A blade balancer, a pitch gauge and good ball-link pliers make this work much easier. See essential RC helicopter tools. Back to the RC helicopters hub.
Frequently asked questions
How do I know if my helicopter's blades are out of track?
Viewed from the side at rotor height, you'll see two blade paths instead of one. The helicopter may also vibrate or feel rough.
Do modern blades need balancing?
Good-quality blades often come matched, but it's still worth checking, especially after repairs or with budget blades.
How tight should blade bolts be?
Snug enough that the blades don't flop, but loose enough to swing out under their own weight when you tilt the helicopter. They self-centre once spinning.
Related guides
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RC helicopter troubleshooting
A fault-by-fault guide to RC helicopter problems: won't lift, spins, vibrates, drifts, loses power or won't bind, with the likely cause and the fix.
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Swashplate levelling
Level the swashplate, set servo arms and zero pitch correctly on a collective pitch helicopter, with or without a levelling tool.
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Essential RC helicopter tools
The tools that make RC helicopter work easier, from drivers and ball-link pliers to a pitch gauge and blade balancer, and what you can skip.