Spline Waypoint Issues

I have a TREX 700 flying extremely well, and I’ve flown about 20 missions so far ranging from 50 to 200 acres per flight. The only issue I have left to solve, is seemingly at random, when doing a 180 degree turn at a Spline waypoint, the heli will either fly the next flightline backwards, or sometimes sideways. At first I thought maybe I wasn’t using enough overshoot, so increased that from 20 meters to 30 meters, but no change. I also thought this problem could be due to cross winds, but it also happens just as often on calm days. I’ve also tried varying speeds, from 15 to 18m/s, and again no difference, it still flies some flightlines backwards or sideways. I’m also wondering if I don’t have the horizontal acceleration set aggressive enough, maybe that could cause this problem?

Is this a known issue or is anyone else experiencing this?

Other than this, everything else is working extremely well with the new firmware, I’ve built two TREX 700s and I can tell you there is no going back, I will not be flying multirotors at all anymore going forward (probably not fixed wings either), Trad Helis once setup correctly absolutely slaughter the best of them!!!

Check the RC4 deadzone on your rudder. If the deadzone is too tight they will do that. Might have to open it up to 40 pwm or so.

Pretty much. A fixed-wing will fly longer but they get tossed around in the wind like a leaf. The helicopter has a steeper learning curve than multirotors and takes a pilot with a little more experience. But once you get over that hump they just love to get out in the wide open spaces and go. If you’re doing a lot of hovering and circling shots, flying where there’s a of people around etc., a multirotor is probably better. But for survey work where you want to eat miles, don’t have to worry about what the wind is doing, and need an aircraft that can take off and land from a 6 foot circle, the helicopter is where it’s at. I believe the world of full-size carries over in that regard. Unfortunately most of the development work in RC is on multirotors now because they’re cheap and easy. But performance, reliability, and efficiency don’t fit in the same sentence with multirotor.

I’ve been getting the same issue with multirotor code. It’s a good tip to look at the RC deadzone. I’ll take a look at that.

It’s set to 15 by default in heli. If the radio gimbal is really tight and uses hall effect sensors instead of pots and accurate on centering it’s not an issue. But not all radios are the same.

Ok, I know I’m running the default RC4 deadzone, I’ll increase it and see if that resolves it. I replaced both my gimbals with hall effect sensors being I had gimbals with pots that went bad eventually.

How does the RC4 dead zone influence this being we’re only talking about flying spline waypoints in Auto mode?

Yes, agreed! I have 3 large fixed wings, from 63 - 70", and yes they can fly much longer, around 45min or so, but for me, the Trad Heli covers essentially the same acreage in less time being I only need 20 meters and 3 seconds for 180 degree turns vs 200 meters and about 30 seconds on each end with a fixed wing, that’s why the survey coverage is about the same, and for me a huge advantage! Multirotors also have to pitch more than double for the same forward speed.

Yaw is the only one of the first four channels that responds in Auto mode. If the deadzone is too tight it can prevent the autopilot from having full yaw control.

Ok, wasn’t aware of that, this makes sense now, thanks again Chris!

Yep. It has been a problem from time to time in multi’s too. I don’t know what the default is in multirotor builds. But I know there was discussion at one time between the dev team about setting the default a little wider.

Hi 223Wylde, would you mind sharing your Trex 700 setup? I do surveys with fixed wing platform and I’m starting to test helicopters for the same purposes. I will be very satisfied if I get 200 acres per flight out of it.

My test rig is an old Xcell 99SE converted to electric but will be ordering something around 700 class when I get the Xcell flying right.

I just used Chris’s new tuning method which works excellent even on 700s. Just start with that and tune your head speed for payload and speed you want to fly at, then tune the spline waypoints last, use the horizontal acceleration parameter. If you search for it, you’ll find a post where Chris replied back to me on how to tune the spline waypoints, I think I was referring to a torque turn.

I went to a system where I use three waypoints per pass. One at the start of the pass, one in the middle, and one at the end. Then use a turn waypoint to control the over-run on the end of the passes. The turn waypoint also helps prevent the helicopter from starting the next pass on an arc, since it takes three waypoints to calculate a spline.

If you take any three waypoints on a spline the heading of the helicopter at the middle waypoint will be the mean of the gps path going thru the other two waypoints on each side of it.

I went back to piston power this year as I got tired of dealing with batteries. But on a typical Section flight flown at 30 mph and 146’ pass spacing it takes 4.1 minutes per round, plus a couple minutes from takoff to fly to the start of the first pass, and a couple minutes to fly back after the last pass. A little over 40 minutes to do a Section.

My gasser can fly for 1.5 hours with 15 min reserve fuel but I can rarely use the full flight time because my operating certificate won’t let me fly over public roads. So a lot of times what could be done in one flight ends up getting broken up into two or three flights. The only time I’m able to get two Sections in one flight is when I’m flying pivots where the only roads are the service roads to the pivots. And those are long and boring flights - takes a couple bottles of Gatorade and a whole bag of Cheetos to fly one of those.

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Helicopter engines for smoke oil engines have obvious voyage advantages.

For curve waypoints, in the taskplanner’s task editing, the calculation of each adjacent point curve is similar to the “Bezier curve” method, that is, it will refer to the position within 3 points, so edit the ideal curve Point, or need to properly configure those key waypoints.

One more question, the copter and helicopter firmware has reached 3.6rc8. When will the steadfast version of 3.6 or the official version of 3.6 firmware be available?

Chris, is that a 700 class gasser? If so, do you have any issues with vibrations? I’ve thought about testing a 700 Nitro.

It’s a 800 class. Rotor diameter is 1,830mm. No issues with vibration. The engine is a TRM VX310SX 2mm stroker, based on a Zenoah G290RC. Burns 26cc/min in cruise.

I flew a smoker for one year. Other than the fuel cost at $30/gallon and burns twice as much as gas since nitro is alcohol based, it worked pretty good. But for a survey helicopter I’d go with gas power with a rope start. It gets old fiddling with electric starters, glow plugs and constantly tuning needles on a nitro. And put a generator on it so you don’t have to fiddle with batteries. Just dump in gas, pull the rope and fly. When it runs out, land, dump in more gas, and do it again.