RC helicopters ยท Fix
After a crash: checks and repairs
By Paul Walsh Last reviewed
Every helicopter pilot crashes. The difference between a quick fix and a disappointing next flight is a methodical check afterwards, because crashes bend parts that look fine.
Immediately after the crash
- Throttle hold on, or cut the throttle.
- Unplug the battery before touching the helicopter.
- Check the battery for dents, splits or swelling, and put it somewhere safe. See LiPo battery safety.
- Collect every piece, including bits of blade.
The checklist
Work from the top down.
| Part | What to look for | Usual fix |
|---|---|---|
| Main blades | Cracks, chips, delamination, bends | Replace as a pair |
| Feathering shaft | Bend: blade grips won't turn smoothly | Replace |
| Blade grips | Cracks, play, rough bearings | Replace grips or bearings |
| Main shaft | Wobble when spun | Replace |
| Ball links | Cracked, popped off, sloppy | Replace |
| Swashplate | Wobble, cracked balls | Replace or tighten |
| Main gear | Stripped or chipped teeth | Replace |
| One-way bearing | Rotor turns both ways or slips | Replace |
| Tail boom | Bent, cracked | Replace |
| Tail belt or torque tube | Stripped teeth, stretched | Replace |
| Tail blades and grips | Cracks, bent hub | Replace |
| Servos | Stripped gears, jitter, not centring | Replace gears or servo |
| Flybarless unit | Moved on its pad | Remount flat and square |
| Landing gear and canopy | Cracks | Replace or repair |
| Motor and ESC | Smell, hot spots, damaged wires | Check before powering up |
On small direct-drive helicopters, also check the motor shafts and the tail motor mount.
Don't straighten, replace
Bent shafts and blades can look straight after "fixing", but they cause vibration that loosens screws and confuses the gyro. Shafts and blades are cheap compared with the damage vibration does.
Before the next flight
- Swashplate level and servo arms at 90 degrees: see swashplate levelling.
- Gyro directions correct: with the motor disabled, tilt and turn the helicopter by hand and watch the corrections.
- Blade tracking: after the first spool-up, check from a safe distance.
- All screws tight, with thread lock on metal-to-metal screws.
A sensible crash kit
For any helicopter you're learning on, keep:
- A set of main blades and tail blades.
- A main gear (two for small helicopters).
- Feathering shaft and main shaft.
- Landing skids or gear.
- A tail belt or tail boom, depending on the model.
- Servo gear sets for your servos.
- Spare ball links and screws.
When to get help
If the electronics are damaged, or the fault survives the checks, see RC helicopter repair. For faults that appeared after a crash, the RC helicopter troubleshooting guide helps narrow it down. Flying planes too? See repairing a crashed RC plane. Back to the RC helicopters hub.
Frequently asked questions
Can I straighten a bent helicopter shaft?
No. A straightened shaft is never truly straight and will cause vibration. Shafts are cheap; replace them.
What breaks most often in an RC helicopter crash?
Main blades, then main gears, feathering shafts, tail blades, landing skids, and servo gears. On small models, the canopy and tail boom too.
Is my LiPo safe after a crash?
Check it for dents, splits and swelling. Put it somewhere safe for half an hour before charging. If it's damaged, retire it.
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