<p>Beta flight has helicopter modes (&quot;Heli 120&quot;, &quot;Heli 90&quot;, etc. depending on your swashplate layout), as does pretty much every other programmable flight controller software.</p>
<p>The outputs from the flight controller are the inputs for the ESCs, which have the same signal protocol as servos. The exception are the flight controllers with integrated ESCs, where the outputs actually drive the motors directly.</p>
<p>This also allows most flight controllers to be used in a fixed wing, where most of the outputs drive servos.</p>

CC BY-SA 4.0
2020-08-10T15:24:44.243Z
Indeed.  And even built-in ESCs are easily turned into servo signal outputs with suitable software and either tapping out the gate signal or adding a pull-up resistor and making the software invert the signal... plenty of people have done this to drive brushless ESC's from boards with an integral brushed ESC.
Chris Stratton
CC BY-SA 4.0
2020-08-10T07:57:24.910Z
2020-08-10T07:57:24.910Z
Robin Bennett
<p>So I've been searching around for a 3-axis flight controller for my 450-size helicopter. It seems that nearly every flight controller which is sold today is configured for solely the control of quad/hex/octo-copters, and have little options for helicopters.</p>
<p>Why don't helicopters have much options for flight controllers?</p>

CC BY-SA 4.0
2020-08-09T03:51:58.717Z
Hi tuskiomi, welcome to Drones.SE! What helicopter-specific features do you not see available on multirotor focused flight controllers? AFAIK nothing in hardware is stopping you from using a multirotor flight controller for a helicopter, and the Betaflight firmware supports helicopter configuration.
ifconfig
CC BY-SA 4.0
2020-08-09T04:25:46.643Z
@ifconfig It's just a generic TREX 450+ clone. AFAIK, multi-rotor PWM outputs will vary highly from heli swash plate outputs, no?
tuskiomi
CC BY-SA 4.0
2020-08-09T04:36:35.140Z
@ifconfig oh sorry, I read that wrong. I'm not seeing helicopter modes in most controllers
tuskiomi
CC BY-SA 4.0
2020-08-09T04:53:00.297Z
*"multi-rotor PWM outputs will vary highly from heli swash plate outputs, no?"* — I don't understand... *" I'm not seeing helicopter modes in most controllers"* — Betaflight has configurations like "Heli 120" and "Heli 90" among others that I believe should be adequate to describe most common swashplate configurations.
ifconfig
CC BY-SA 4.0
2020-08-09T06:47:56.077Z
@ifconfig what does the 90 and 120 refer to in this case?
tuskiomi
CC BY-SA 4.0
2020-08-09T06:50:28.857Z
The angle between locations where servos move the swashplate. I'd recommend looking at this Ardupilot wiki page for more info: https://ardupilot.org/copter/docs/traditional-helicopter-swashplate-setup.html The names on that page aren't identical, but they're close.
ifconfig
CC BY-SA 4.0
2020-08-09T06:51:00.157Z
@ifconfig Ah, I see. This is interesting info
tuskiomi
CC BY-SA 4.0
2020-08-09T15:26:44.257Z
The root issue here seems to be confusion between the hardware and the software.  A conventional helicopter doesn't need any sensor a quadrotor FC doesn't have, and it doesn't really need any more outputs, either.  It *does* need a somewhat different set of rules for generating control output however, but that comes down to the software.  A fixed-function preflashed quad board won't work, one with suitable open-source software will.
Chris Stratton
CC BY-SA 4.0
2021-08-03T19:28:18.773Z
@ifconfig He is referring to the (usually) dshot protocol used to talk between the FC and the motor controllers. It's a protocol that servos don't support (it would be useless, they can't respond quickly enough anyways). However, the [x]flight/inav family of flight control differentiates between "servos" (standard PWM) and "motors" (chosen PWM protocol)
Brydon Gibson
<quadcopters><flight-controller><helicopters>
Why don't solutions exist for a 3-axis helicopter flight controller?
tuskiomi
# Why don't solutions exist for a 3-axis helicopter flight controller?

(Asked by: username_0 on 2020-08-09)

So I've been searching around for a 3-axis flight controller for my 450-size helicopter. It seems that nearly every flight controller which is sold today is configured for solely the control of quad/hex/octo-copters, and have little options for helicopters.

Why don't helicopters have much options for flight controllers?

**Tags:** quadcopters, flight-controller, helicopters

> **Comments:**
> **username_1**: Hi username_0, welcome to Drones.SE! What helicopter-specific features do you not see available on multirotor focused flight controllers? AFAIK nothing in hardware is stopping you from using a multirotor flight controller for a helicopter, and the Betaflight firmware supports helicopter configuration.  
> **username_0**: @username_1 It's just a generic TREX 450+ clone. AFAIK, multi-rotor PWM outputs will vary highly from heli swash plate outputs, no?  
> **username_0**: @username_1 oh sorry, I read that wrong. I'm not seeing helicopter modes in most controllers  
> **username_1**: *"multi-rotor PWM outputs will vary highly from heli swash plate outputs, no?"* — I don't understand... *" I'm not seeing helicopter modes in most controllers"* — Betaflight has configurations like "Heli 120" and "Heli 90" among others that I believe should be adequate to describe most common swashplate configurations.  
> **username_0**: @username_1 what does the 90 and 120 refer to in this case?  
> **username_1**: The angle between locations where servos move the swashplate. I'd recommend looking at this Ardupilot wiki page for more info: https://ardupilot.org/copter/docs/traditional-helicopter-swashplate-setup.html The names on that page aren't identical, but they're close.  
> **username_0**: @username_1 Ah, I see. This is interesting info  
> **username_2**: The root issue here seems to be confusion between the hardware and the software.  A conventional helicopter doesn't need any sensor a quadrotor FC doesn't have, and it doesn't really need any more outputs, either.  It *does* need a somewhat different set of rules for generating control output however, but that comes down to the software.  A fixed-function preflashed quad board won't work, one with suitable open-source software will.  
> **username_3**: @username_1 He is referring to the (usually) dshot protocol used to talk between the FC and the motor controllers. It's a protocol that servos don't support (it would be useless, they can't respond quickly enough anyways). However, the [x]flight/inav family of flight control differentiates between "servos" (standard PWM) and "motors" (chosen PWM protocol)  

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## 1 answers

### Answer by username_4 on 2020-08-10. Score: 5 | Accepted answer

Beta flight has helicopter modes ("Heli 120", "Heli 90", etc. depending on your swashplate layout), as does pretty much every other programmable flight controller software.

The outputs from the flight controller are the inputs for the ESCs, which have the same signal protocol as servos. The exception are the flight controllers with integrated ESCs, where the outputs actually drive the motors directly.

This also allows most flight controllers to be used in a fixed wing, where most of the outputs drive servos.

> **Comments:**
> **username_2**: Indeed.  And even built-in ESCs are easily turned into servo signal outputs with suitable software and either tapping out the gate signal or adding a pull-up resistor and making the software invert the signal... plenty of people have done this to drive brushless ESC's from boards with an integral brushed ESC.  

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