Example Build¶
A complete setup of a small electric helicopter, from a fresh flight controller to the first hover. It links to the detailed pages as it goes; follow the same order for your own helicopter.
| This example | |
|---|---|
| Helicopter | OMPHobby M4, servo tail |
| Flight controller | Radiomaster Nexus |
| Receiver | ExpressLRS |
| ESC | OMPHobby 65A |
| RPM | ESC RPM wire to the Nexus RPM port |
| Radio | Any Ethos or EdgeTX radio with the Rotorflight Lua suite |
Blades off
Leave the main and tail blades off until step 12.
1. Firmware¶
Flash the latest release, choosing the Nexus board, with Full chip erase. Connect.
2. Receiver¶
The Nexus has a dedicated ELRS port (Port A).
Warning
Check the receiver lead's pin order against both ends before powering up. Some ELRS receivers use a different pin layout, and a wrong lead can damage the receiver.
- Configuration tab: set Port A to Serial Rx. Save and reboot.
- Receiver tab: TBS CRSF protocol, ELRS channel preset. Save and reboot.
- Move every stick and switch and check the bars follow -- right way round.
- Turn on Telemetry and Custom Telemetry -- see ELRS Custom Telemetry.
To update the receiver's firmware later, use the ExpressLRS Configurator's Betaflight passthrough with the Rotorflight Configurator closed.
3. Arm switch¶
Put the arm switch on channel 5 (AUX 1) and add the ARM mode on the Modes tab. See Arming & Safety.
4. Orientation and accelerometer¶
- Tilt and turn the helicopter: the 3D model on the Status tab must move the same way. If not, set the board orientation on the Configuration tab.
- Stand the helicopter level and calibrate the accelerometer.
5. Servos¶
The M4 uses CCPM 120°. Plug the servos in as the diagram on the Servos tab shows, and follow Servo Setup: rate and centre first, then directions, then centring.
6. Mixer¶
Follow Mixer & Swashplate Setup: directions, level swashplate, zero pitch, collective and cyclic calibration, limits, tail.
7. Motor and ESC¶
On the Motors tab:
| Setting | Value |
|---|---|
| Throttle Protocol | PWM |
| Telemetry Protocol | OMPHOBBY (ESC telemetry wire to a UART set to ESC Telemetry) |
| RPM Sensor | On -- the ESC's RPM wire is on the Nexus RPM port |
| Main Rotor Gear Ratio | From the M4's specifications |
| Tail Rotor Gear Ratio | From the M4's specifications |
| Main Motor Pole Count | From the motor's specifications |
See RPM Measurement and ESC Telemetry. Calibrate the ESC's throttle range if its manual asks for it.
8. Test the motor and telemetry¶
Blades off. Enable Throttle Override and raise it slowly. The motor spins, and the Motors tab shows RPM, voltage, current and temperature from the ESC. Check the rotor speed is plausible.
9. Power¶
With ESC telemetry working, set the Battery Voltage Source and Battery Current Source to ESC on the Power tab, fill in the battery profile, and turn on SmartFuel.
10. Governor and RPM filter¶
- Governor Setup: ELECTRIC mode, full headspeed in the profile.
- RPM Filters: enable on the Gyro tab, Medium strength.
11. Rates, radio and backup¶
- Set the Rates to taste.
- Install the Lua suite on your radio.
- Check the failsafe: blades off, armed and spinning, switch the radio off -- the motor must stop.
- Take a backup.
12. Pre-flight checks¶
With the blades on, before the first flight:
- Stick right → swashplate tilts right. Stick forward → tilts forward. Collective up → pitch increases. Rudder right → nose yaws right.
- Gyro direction: tilt the helicopter nose down by hand while armed (at idle, blades held) -- the swashplate must tilt back to resist. Repeat for roll and yaw.
- Throttle hold works, and the arm switch is where you expect it.
Then spool up, lift into a hover, and see Tuning.