RC helicopters ยท Fix
RC helicopter troubleshooting
By Paul Walsh Last reviewed
When a helicopter misbehaves, it's tempting to start changing settings. Don't. Almost every fault has a simple physical cause, and working through them in order saves a lot of time and money.
Start with the basics
- Battery. Freshly charged, warm, and not old or swollen. A tired pack causes more "faults" than anything else. See LiPo battery safety.
- Blades. No cracks, chips or bends; bolts snug, not over-tight.
- Screws. Check every screw on the head, tail and frame.
- Linkages. Every ball link should move freely with no binding and no slop.
Fault finder
| Symptom | Likely causes | Where to look |
|---|---|---|
| Won't lift off | Weak battery, damaged blades, slipping main gear, wrong pitch or throttle curve | Battery, blades, gear mesh, transmitter curves |
| Lifts but sluggish | Old battery, worn motor (brushed), dirty or worn gears | Battery, motor |
| Spins on take-off | Tail problem: gyro direction, tail motor, belt, linkage | Tail spinning and tail wag |
| Tail wags | Tail gyro gain too high | Tail gain |
| Vibrates or shakes | Blades out of track or balance, bent shaft, worn bearing | Blade tracking and balancing |
| Drifts in one direction | Trims, swashplate not level, flybarless unit not level | Swashplate levelling |
| Slow wobble in hover | Cyclic gain too high, loose unit mounting | Gyro gains, mounting pad |
| Circles round in the hover | Vibration, unit mounting, uneven blades | Mounting, blades |
| Tips over on take-off | Pushing the stick while taking off, wrong gyro direction | Technique, gyro directions |
| Loses power mid-flight | Low battery cut-off, overheating ESC or motor, slipping one-way bearing | Battery, temperatures, bearing |
| Won't bind | Wrong protocol, wrong bind procedure, throttle not at zero | Transmitter settings, manual |
| Twitches with no input | Radio interference, failing servo, low battery | Servos, receiver aerials |
Electronics checks
- Gyro directions. With the motor disarmed, tilt and turn the helicopter by hand. The swashplate and tail should correct the opposite way. A reversed direction makes the helicopter flip or spin instantly. See gyros and flybarless units.
- Mounting. The flybarless unit must be firmly attached on its pad, flat and square.
- Servos. Each should move smoothly without jitter. See RC servos explained.
- Failsafe. Switch the transmitter off with the blades removed: the motor should stop.
When it started after a crash
If the fault appeared after a crash, assume something is bent or broken even if it looks fine. Work through after a crash: checks and repairs.
Still stuck?
If you've worked through the basics and the fault remains, it may be time for a specialist; see RC helicopter repair. All the fix guides are on the RC helicopters hub.
Frequently asked questions
Why won't my RC helicopter take off?
Most often a weak or cold battery, damaged blades, a slipping main gear, or (on collective pitch) a throttle or pitch curve problem. Try a freshly charged battery first.
Why does my RC helicopter vibrate?
Usually blades out of track or balance, a bent shaft, or a worn bearing. Check the blades first, then spin the main shaft to look for a bend.
Why won't my helicopter bind?
Check the transmitter is set to the right protocol and model, bring it close, follow the bind sequence exactly, and make sure the throttle is at zero.
Related guides
RC helicopters
Tail spinning and tail wag
Why an RC helicopter spins on take-off or its tail wags in the hover, and how to fix gyro gain, tail linkage, tail motor and belt problems.
RC helicopters
After a crash: checks and repairs
The parts that usually break in a crash, the checks to make before flying again, and a sensible crash kit to keep on the shelf.
RC helicopters
Blade tracking and balancing
How to check and adjust main blade tracking, balance blades properly, and cure the vibration that out-of-track rotors cause.