Thanks Chris, yes NO gov on 450, though we can set them up if required, where a switch can be programmed to tell the ESC in which gov mode it is in, but i’m not trying that yet.
And thanks Bill it’s clear now, can’t wait for the weekend now 
Since the throttle curve was fixed in the software (five spline points vs three linear) it works really good with electrics with no governor. The only issue you will have without using a governor is that rpm will gradually fall a bit as the battery voltage sags when they discharge. But electric does have an advantage in that power output doesn’t change from a dry cool day to a hot humid day like it does with engines.
You will never notice this change in density altitude with your car engine unless you run it on a dyno and measure it. It only requires about 17 horsepower to move the average car down the road at cruise speed. Aircraft engines, however, operate at high power output continuously. Especially helicopter engines with the aircraft in hover. It takes around 55 horsepower just to turn the rotor on an ultralight helicopter in hover at a takeoff weight of 385 lbs. So a governor becomes more necessary with engines than with electric motors in model aircraft.
In RC models, small helicopters like a 450 where the rotor runs at quite high speed, the loss in rpm as the batteries sag is not usually too noticeable. But with larger ones it is. So the ESC governor is more common in larger electric sizes. My little Trex 500 that I built a few years ago for testing stuff, and which I haven’t flown now for a couple years, does not even have a governor in the ESC. It doesn’t need one. My Trex 600 that I also haven’t flown for a couple years, does have a governor and it needs it. On 6S power the rotor speed drops pretty fast as the batteries discharge. I have never flown anything larger than 600 class on electric power as I don’t consider them to be practical above that size. The power density of piston or turbine power is much higher than electric per unit of weight once you get into 700 size. But I would imagine a 700 electric is worse than a 600 if it doesn’t have a governor.
Waw thanks for all the info, interesting how real things work. I have a 600 nitro (vision 50) flybar one, but well, i will never probably have the time to set this up on a AC FC. I mean, just the shift from electric to nitro setup was quite intense for me, to get the engine carburetor and governor setting to stop it from flaming out or bogging - i never really managed to get it right till date with the Redline engine, i can imaging adding a FC and a Firmware into this mix. 450 electric is probably as close as you can be w.r.t having control of your heli on your Tx all the time. I tried first with OpenPilot and cc3d but wasn’t all that confident. Seeing somany successfully do it with AC i though i give it a try. It still gives me shivers just the though of having to let a FC control the heli. So is ACRO mode = RATE mode on helis? all channels are on passthru including the cyclic servos and rudder servo? Guess that will be the first F-MODE switch to always have in that case.
If you are interested you can look at this YouTube video. It is taken with a TREX 600 E fully automatic last October in New Zealand. https://www.youtube.com/watch?v=jMqtycpIVgo
This video has been rendered a bit ruff not to good.
You can see in the shadow that the Heli is flying sideways. Always aiming the camera to the region of interest.
After many missions I trust my Heli with ArduCopter firmware. Of course I am ready to take over if there is a problem. I never ever had an accident in any mission I have done with a Heli or the drones I own. Arducopter works for me very reliably with all my electric air vehicles.
Awsome video fred, thanks for sharing. You have a great nursery going and a very nice stream, plenty of space for flite test, unlike where i come from (bangalore), almost impossible these days, but i’m just keeping the hobby alive. Yes i can see the heli sideways, quite a big for a shadow of 600. You seem to have set this one up quite well. Will hope you can share some of your valuable experience. And was that a fully autonomous flight??
The takeoff I do usually manual up to 10m and then switch to Auto. Coming home and landing (RTL) is always auto.
The house where the Heli is starting and finishing the mission and the Nursery is owned by my son.
I am 71 years old and fly as a hobby for some time.
Bill and Chris and others are the right people to get you going. Good luck.
Thanks Fred, they sure are.
This is correct. Acro in ArduPilot is the same as Rate mode in LibrePilot or OpenPilot.
I should clarify a bit for ArduPilot Acro. You only get RC passthru of channels if you are flying a flybar model. With FBL head the ArduPilot Acro still uses the attitude controller. But three of us did considerable work to the Acro mode for helicopters to make it better in ArduPilot so it works like a flybar model. If everything else goes bad, including the attitude controller’s solution to level the helicopter in Stabilize, you will be able to maintain control of your model in Acro with the new virtual bar Acro mode we developed for heli. It was one of the most popular new features for helicopters in ArduPilot. But it is currently only available in Copter 4.0 or newer.
The Acro mode must be tuned for the simulated flybar decay response you prefer, and it can be tuned individually in both pitch and roll axes. I personally like a very rapid decay on roll so it is more “stick to swash” response. A little less on pitch axis. Tuning it is like changing the weights or paddles on a flybar, except for being able to tuned separately pitch/roll. It is very nice.
Bill will be able to assist you in tuning this, but the attitude controller must be tuned first and Acro is not a good mode to tune the attitude controller for what the autpilot wants. Stabilize and all the other modes are autopilot modes. Acro is the pilot’s mode. With acro you can even switch in custom collective and expo curves in your RC radio and have these curves automatically switch out with the flight mode switch when you go to another autopilot mode. I love being able to do this as setting RC curves and expo is very easy and with the flip of a switch I can have a helicopter that is as “hot” handling as I want, or make it as gentle handling as a AS332 with custom setup in the RC radio.
Nitro engines are quite finicky due to two reasons. They have a very simple but poorly designed carburetor. And the air/fuel ratio with the methanol/nitromethane mix is around 5:1. So when air density changes the resultant required change in fuel rate is also quite large. They require constant tuning.
Most UAV piston helicopters will use gasoline engines. Ideal A/F ratio with gasoline is 14:7:1, but in aircraft will run around 12:1 for peak power. We have mixture control servos on our piston helicopters so if the engine doesn’t clean out during runup we lean the mixture slightly to get it to clean out before pulling pitch.
Electric is pretty much “push-button” and can do auto takeoff’s and this sort of thing. Piston engines aren’t and require an experienced pilot to fly. Even in flight if the engine is running is too hot we richen the mixture a bit to keep it within it’s proper operating temperatures. The autopilot is not able to fly piston helicopters totally “autonomous”. You can try it, but you will experience an eventual engine failure. RC helicopters with piston (or turbine) power are pretty much like the big ones you ride in. You don’t just push a button and “go”.
I will definitely try flashing the latest firmware and as suggested try the Qground control. So is it ok to start tuning straightaway in STAB mode, or you suggest ARCO first? (We normally do RATE mode first in traditional helis, so as to get the mechanical setup correct first mainly the yaw, and then switch to tuning Heading-Hold HH mode. Ofcourse with flybar, the cyclic is always in RATE/ACRO mode if not using a FBL system) - sorry i ask this, i will ofcourse follow the tuning guide as it should be, but its nice to hear directly from you.
Yes, i have experience the effect of air density. Initial days with nitro engines, would normally start tuning during the day and would go late into evening. Just that change and i have noticed how it responded differently. I could never get the tuning of transition from low end to high end, so gave up as it needs to be done in flight with punch outs and be ready for anything. I have tuned nitro car engines (as it’s doable on bench) and nitro airplane engines (to most part just running them just a little rich would do), but heli engines was a real challenge due to the varying loading. I realized it was air density that always played the trick. I almost would get it right by late evening, but next day, it’s all gone. They say O.S. nitro engines are far easier than Redline ones when it comes to tuning, i guess they’re right.
Thanks for all the insight.
I think Bill can help you decide this, but I always tune the attitude and rate controller in Stabilize. That tuning is more for the autopilot than for the pilot.
I couldn’t say that’s true. I flew a O.S. 105HZ nitro engine in a Trex 700 for two years doing survey work with it. It always required adjusting the carb no matter what. The bearings, piston and cylinder sleeve life is quite short. There was no real decent gas piston engine conversions available back then. But since we have gone to gas pistons they are just about trouble-free. I have over 500 flight hours on one of them. We put a fresh engine in it after 500 hours, but on tear-down of the original engine it could’ve run another 500 hours without issues. I was lucky to get 50 hours out of the 105HZ before it scored the piston and sleeve and the engine locked up. And then on teardown the bearings were always badly corroded from the nitromethane with severe pitting on the balls and races. It cost about $350 every 50 hours to overhaul it, and it burned $30/gallon fuel like it was an endless supply.
The gas engines only burn 22cc/min in a 800-class machine. And if you take care of the engine and don’t abuse it you can’t hurt one. And since the gas engine has a fairly heavy flywheel they are just about vibration-free at full rpm on the governor. Engine replacement cost was about $1,000 at 500 hours. But using what we found on teardown of the first one, we will simply pull the cylinder at 500 hours and inspect it instead of replacing the engine. In the bottom end we found no evidence of main bearing wear, no evidence of the rod big-end bearings skidding on the crankpin. It still looked like new in the bottom end. On the top end just some light scuffing in the bore near the exhaust port. But simply honing the cylinder and replacing the rings would’ve gotten at least another 250 hours out of it.
So basically, I don’t consider nitro to be any more practical than electric for helicopters that fly one-hour (or more) long survey flights all their life.
Hi and I hope you’re all safe and healthy.
After a long gap, I just had a chance to think of RC once again to take mind off the pandemec, so i thought i update the progress. Before i left last time, i had fbl 450 heli + mateksys f405 wing and ardu heli mechanically set, wired up and firmware setup completed upto the pitch-curve, and something didn’t seem to get right so had left it there. So what i remember was that I had got the swash leveled, the throttle-curve set and was able to even ARM and spool-up (thanks to all of your assistance), no issues there. Then when i went into setting collective pitch range, I followed the instructions and went into manual mode to set the MID, MAX and MIN COL set for 0, +10, -10. That seemed ok. But when i moved out of manual mode, what i noticed is the col pitch was not as i had set. At mid throttle i was getting +ve pitch and not zero pitch as i had set. Which also meant that the settings for min and max were off. Tried again several times, but it all seems ok when setting the collective pitch range in manual mode, but once out of it, they’re off.
So i feel i’m missing something here and hope someone can help me.
Thanks
Satish
What flight mode were you in? Stabilize flight mode can have a collective pitch curve set separately from Acro. Acro should give you pretty close to the values you set using the H_SV_MAN. The stabilize mode collective pitch curve is set up based on the IM_STAB_COL parameters and could be different from acro mode.
Thanks Bill, I will check it this weekend and get back. I didn’t touch the flight modes so far, i was assuming they are defaulting to acro on all switch positions, but will cross check it. I now see you did mention that in your previous post, i missed it.
Thanks
Satish
Hi Bill, you were right, it was falling back to stab mode after exiting the setup. Now i have set the col pitch for both acro and stab mode. My next concern is the tail-servo setup. Are the defaults good enough?
We normally set things up mechanically in rate/acro mode (sometimes ending up with a few deg of tail pitch until we can fly tail-in) and then add the tail-gyro and switch to heading-hold. How is it for AP? .
Thanks to all of you so far.
-Satish
They will get you flying. With AP, there is no way to turn heading hold off. The yaw axis is designed as rate command with heading hold. So try the defaults and then you can fine tune from there.
Hi Bill,
Just noticed something (luckily on bench with props off) - while i was doing one final check before my first flight, i was checking the throttle was responding ok. I started in ACRO mode, ARMED no issues and throttled up, the response seems fine i.e. linear. But when i switched to STAB mode, the throttle just jumped all the way, probably 50%, and i could only see it respond if i moved the th stick above 50%, below that throttle just stayed there, i switch back to ACRO it’s ok. So i guess something once again i’m missing. The only things i changed last time were the Curve settings for STAB mode, i.e. Stab1, Stab2, Stab3 and Stab4 in order to get my desired col pitch in stab mode.
Thanks,
Satish
Satish,
I’m not sure what you mean when you say the throttle jumps 50%? I thought this is an electric heli. Are you using a throttle curve?
The collective and throttle responses all depend on how you have the stabilize collective curve set up. Remember that the code has to transition from the acro curve to the stab curve. If you are at a collective stick position where the acro and stab curves are not aligned then you will see what appears as a jump in the collective as well as a jump in throttle since the two are tied together base on the throttle curve. It is just the code trying to transition from curve to another and the throttle follows the collective pitch based on the throttle curve.
Post a video of the behavior and a log that is associated with the video.
Yes bill, it was indeed the acro-stab transition. I later set the curves so they dont have to transition a lot to get there, and that resolved the issue. I could go for a test with blades confidently after that. I tested in STAB mode, but for some reason i didn’t get any lift even with full throttle - probably bad COL pitch to head-speed ratio above the mid-stick? or it was too heavy, i have to figure it out.
I have increased the COL pitch range from MID to MAX to go from about 0 to +8. This is on a 11.1v 25c LiPo, H2217 4000KV brushless + 13T pinion. The motor was very hot at the end of the test.
At MID stick i can feel there is enough head-speed - what is your recommendation of the pitch range? Any other suggestions?
Thanks
Satish