Learning how to autorotate a helicopter, and becoming proficient at it, is mandatory training for both RC and full size helicopter pilots. The problem is, how do you practice it with ArduPilot without shutting down your engine and not being able to do an in-air restart to bail out until you become proficient? We have the ramp and runup times to worry about, etc…
Well, it’s quite easy by setting ArdPilot to the very popular Mode 1 throttle control. The rest of the setup is in your radio and ESC just like it is with any other FBL unit. Except instead of the traditional Throttle Hold we’ll incorporate a modified version of it using mixes with an idleup switch to bypass ArduPilot’s ramp/runup timers, and the soft start function in your EC.
you are explaining a important way of an in-air restart of the Helicopter without delay.
I remember when I started with a APM 2.5 in a Heli and my Spektrum DX8 years ago I did not had a delay at a restart in mid-air.
I do see this is possible first time to bypass the ramp/run-up timers with a TX ( now Taranis ). Using Castle-ESC’s only I know exactly what you are talking
In my opinion it should be in the Wiki mentioned for the not so knowledgeable like me. I would have fiddled with my TX a lot earlier than now to get that working. Thanks again Chris for your comprehensive information’s!!!
I wanted to show it, Fred, to demonstrate that it’s much like setting up any other FBL unit. ArduPilot is unique in that the Channel 8 throttle control is not normally tied to the collective like a regular setup with a Throttle Hold in a FBL unit. But it can still be done with ArduPilot by using some mixes in your radio so you can practice autorotations without having to completely turn off the governor signal on Channel 8, which will reset all your soft-start timers.
The setup in different radios will be different. But once you see the general idea of how to do it, you should be able to fiddle with your radio to find the proper combination of mixes to make it possible.
I suspect this is one reason why the Mode 1 throttle control in ArduPilot is by far the most popular mode. The microprocessor controlled radios we have now are much more advanced in being able to set up custom throttle curves or profiles than the code could ever hope to be using Mode 2 or Mode 3.
No problems to get the mix into my TX.
I hope others will take your advise and do the Auto-rotation with their Heli’s. I have practiced my Auto’s with the Phoenix Flight-simulator first which was a great help.
The simulator also works to practice the procedure. It’s also easy to practice with a real one. Start out by hovering maybe 2-3 meters, shut down power and learn how to manage the collective to get a nice soft landing using the stored energy in the head. Every helicopter has a “dead man’s curve”, which is a zone where you cannot use energy stored in the head like you can at 2-3 meters, nor are you able to build or maintain headspeed from a hover to make a soft landing. Any helicopter can be landed in autororation in forward flight at any alttiude. But not from hover in the “dead man’s curve”.
So the next step after you master collective management at 2-3 meters is to start flying the helicopter around and learn how to use the flare to build headspeed and stop the helicopter prior to touchdown. This can be practiced at much higher alitude and use the “bail out” feature until you get proficient at it.
You will very quickly learn to land into the wind like a fixed-wing does. And will quickly learn that if you get a rotor stop it is impossible to get it going it again (use the bail out).
For autorotations in a real emergency the ArduPilot system will try to maintain altitude if you get a power failure in flight. So the autopilot will simply stop the rotor in any of the altitude controlled flight modes. And then you have a problem. Fortunately, there’s usually some sort of indication that a power failure is imminent. I’ve had to do two of them on commercial flights, once when I blew the clutch in my piston heli. Another time when I had a bearing go out of the motor in my electric. It was the audio feed on my FPV that alerted me to both before the headspeed alarm went off on my radio. In a real emergency you got a lot of stuff you’re watching, not expecting a loss of power situation. So you have only seconds to get the heli out of auto or loiter and into Stabilize to save it. I’ve gone to setting up my Stabilize collective pitch curve (the IM_STAB_COL settings) so the stick at bottom is -2 to -3 degrees of collective pitch. That way it only takes flipping one switch to get back into Stabilize and bottom the collective immediately and it’s automatically at the right pitch to save the headspeed. Then, once you get a forward glide established you can feather the main rotor and get a better glide ratio. If you auto straight down she’s not going to float very well and she’ll build a lot more descent rate than if you get the heli into a forward glide. So setting the Stabilize pitch curve eliminates the “guess work” when you only have seconds to react.
In a real emergency in hover from anywhere to about 4-5 meters to about 12-15 meters you’re in the “dead man’s curve” with a heavily loaded UAV heli. Altitude is always your friend if you’re going to split the needles in flight with a helicopter, either intentially or unintentionally.
Chris, thanks a lot for another great explanation of the Auto-rotation.