Newly built 500 3g... control problems.

[WonderedUnder]

Just finished building my T-rex 500 3g (V2 unit). Was my first heli build. Got it all done, went through 3g setup as instructed in the manual and went to try hovering it. Slowly increased the throttle and when i got to right above midstick (prolly 80% throttle, 2-3 pitch) the heli started leaning forward so i cut back throttle. I rebooted and tried again, same thing. Also, when i apply right aileron, the rotor disc leans sorta forward and right.

I haven't experimented too much with it to get this figured out yet, just wondered if anyone knew what i did wrong or if there was a quick fix for it. I can't wait to get this thing tuned in and in a hover!

Thanks!

[Vinger]

Vibrations on the ground will cause weird behaviour, the ground resonance causes the gyros to give inputs that's not really required. Some of it can be elimanated by hard mounting the gyro unit and getting rid of vibrations on your heli as much as possible. Also at slow HS the resonances are worst, so let the heli spool up to normal HS before you give any input, take off is normal afterwards, just make sure you have the setup done correctly and that the gyro does react correctly.

[jamesb72]

If you have swash levelled at mid stick, and have confirmed and double checked all directions/3G settings are correct (including tail/gyro) you need to spool up and then pop the heli straight into hover - the FBL heli's do not like sitting on the ground revved up.

Same with landing, as soon as the skids touch the ground, you need to centre cyclic and pull pitch down smoothly but quickly to get heli 'down' firmly.

Of course, this means you have to be 100% sure setup is correct before you test fly, which is not like a flybarred heli where you can take it steady and wobble around on the ground to check your happy.

If your not confident to do this, then get someone who is familiar with 3G/FBL to test fly the heli for you, they can check it over first to make sure everything is setup as it should be.

[WonderedUnder]

I am skurred!

I think i've set it up alright - i just don't have any heli buddies that i can get to look it over for me. I'm working a 30h shift today, but when i get home i'll post a video of the heli's behavior and maybe someone can tell me if this is typical of ground effect on a 3g unit.

Thanks again for all your help!

[jamesb72]

Its a bit of a leap of faith flying the 3G for first time, I am lucky in that I put the 3G on an existing heli, so knew the setup was roughly right, also I was rushing so literally bolted it on, ran through the setup instructions and threw it into the air.

Main thing is to double check your swash/tail movements are correct from radio, and the 3G/gyro corrections are correct - if these are correct the heli should be flyable.

Also, a bit of expo on first flight is worth putting on, I run about 30% on DX6i, on Futaba you may need even more - once you've got a couple of flights you can can dial it down as you wish, but it helps avoid it being too 'twitchy' on first flight.

[mikmerl]

I recently flew mine and I am very happy with it see https://www.helifreak.com/showthread.php?t=213932
Check to see if the swash is correcting in the right direction when you tilt the helicopter left and right and also nose down and nose up. (get into the habit of doing this before each flight after you see the three “twitch” initialization) If it is not compensating in the right direction and it gets in the air it will crash.
The previous posters are right a flybarless helicopter definitely does not like to have the skids on the ground when spooled up. Don’t give it any cyclic inputs as you are spooling up until it is free from the ground. As soon as there is air under the skids it settles down.
Be ready for a pleasant surprise when you get it in the air it responds fantastically.

[WonderedUnder]

I am gonna try just popping it up into the air when i get home... my only concern was how hard the chopper nose tipped forward when i got the throttle up past mid-stick. The rear of the skids lifted off the ground and i feel that if i didn't cut back the throttle that it would've smacked the blades straight into the ground.

The gyro corrects when i tilt it left/right, forward/back, the swash is leveled at midstick, and responds correctly to all inputs when it's not spooled up, and the tail responds appropriately.

I added 30% expo to all channels. Do you think i should just pop it up?

[jamesb72]

None of my heli's nose down noticably at lift off - you need to check this before trying to fly.

I'd check swash is definitely level both at midstick and full stick in DIR mode (with a swash level tool, or allen key velcro strap to main shaft, not just by eye) - I know the 3G instructions say not to worry about levelling swash at full stick, but I've ignored this on all 3 of my 3G heli's and levelled swash midstick then top and bottom with ATV (only tiny tweaks needed at top or bottom none of mine needed more than one servo adjusting more than 5%), and they climb perfectly both upright and inverted.

Also, I'd suggest turning elevator gain down slightly to 10:30 or so for first flight, once you have it flying you can turn it up/down to try out, but I ended with mine on ail 12:-- elev 10:30 - I don't think this has anything to do with nose down on lift off though.

Is your CofG OK ? I wonder if heli is nose heavy (very unlikely with 500) maybe thats why it would nose down - I'd be surprised as the 500ESP is mostly tail heavy due to torque tube/metal tail, so I run my lipos forward (top of lipo lined up with the rubber canopy supports) this is 2650 or 3000 Turnigy packs.

As long as your ready to pull back on cyclic - and have plenty of space in front of you, if all that checks out I think you have to pop it up or you will never know, if all the checks are OK which they are it should be fine !

Also I have trimmed my heli's to hover, they only took a few clicks but trim seems to work fine, a lot of people say not to use it, but its OK for me on my heli's, and they hover OK inverted (one of the reasons not to use trim), CofGs aren't perfect on mine though, so maybe if you could get CofG perfect (both front/back and sideways) trim wouldn't be needed.

[edsel.labao]

Mine was leaning too when I first tried the system. Then I redid the setup following all the instructions to a tee. Now I can spool up and sit there with no tilting.

How is your sensor mounted? also, are you initializing the system on a hard stable surface? My table was moving when I first had this problem, I think the system does not initialize properly.

[WonderedUnder]

Thanks for all your help.

I have my sensor mounted on the bottom plate with the stock align 3g tape (one piece) and strapped down hard with the hook/loop tape. I'm also initializing on a hardwood floor, and am getting the three up and down movements of the swash.

The only thing i can think of is something weird happening when i set my endpoints in 3g setup? the gyro directions are certainly right, i'm confident the swash is level (used a tool), and the servos all move in the right direction.

I'll likely go through the whole flybarless 3g procedure again when i get home and see what happens.

[jamesb72]

Thats exactly how I have my sensor mounted, and it seems to work brilliantly.

I think if you double check setup, and all OK the only way to check is to pop it into a hover, which I know is a scary thought, but fingers crossed it will be OK.

I am a big fan of the 3G, and of my 3 heli's (250/450/500) the 500 is the best with 3G, it flew absolutely perfectly from the first flight, so I am sure once you've got over this hurdle you will be delighted with it !

[Lzfalcon]

I would not pop it in the air. I just finished a flybarless 500 and it did the same thing yours is doing. I mistakenly had the swash tilting the wrong direction. Remember that the direction you are looking for is the motion Of the swash while tilting the heli forward or side to side. As you are tilting the heli forward the swash is tilting back. Another piece that I did not see in the instruction was the radius arms need to be aligned properly. While the main blades are side to side on the heli, the radius arm that is facing the rear need to be aligned with the rear of the swash. To soften my movement on the swash. I went into my swash mixing on my dx7 and brought down aileron and elevator to 45%. The second hover was flawless. First flybarless set up. By the way , I have the sensor on top with the arow facing toward the main shaft. Hope this helps

[WonderedUnder]

So i went through the whole flybarless setup procedure again and rechecked everything.

Finally had the guts to just try it. As soon as i lifted it off the ground, the nose dipped forward and i was able to pull back on the elevator and level it and set it back down. a couple back clicks on elevator trim and problem is gone.

Should i go back and mechanically fix this by changing the swashplate leveling?

[jamesb72]

Great that it flies OK - if the trim is not bothering you I'd just fly with it for now - is your CofG OK, as if your swash is perfectly level at midstick in DIR mode, then heli shouldn't need trim other than to correct for CofG - the fact it tilts forward makes me think it probably isn't CofG as that would be backwards normally with a 500 unless you have very big lipo.

[WonderedUnder]

So i went back and re-did the entire head. I must have leveled my swash OUTSIDE of dir mode and so the subtrims were off. Went back saw that at zero stick the swash was definitely NOT level and leaning forward. Re-did everything and it flies MUCH better now.... very stable on the ground spooled up.

Only thing now is a touch of tail wag that increasing or decreasing the gain doesn't seem to effect too much. On my dx6i just hovering, have the gain set to 68% and it's still wagging around. I've seen lots of threads on this so i'll do my homework and see if i can't get 'er right.

THIS HELICOPTER FLIES AWESOME!

[WonderedUnder]

I unstrapped the 3g sensor and the tail seems much more behaved without being strapped down. Have gain up to 70% (on dx6i) while hovering and it only has the faintest occasional wag to it. When i do a pitch pump, the nose of the heli does yaw to the left... you think adding some headspeed would help with this? My normal throttle curve is 0 40 75 85 90... haven't tried idle up yet, but i have it set to flat 90.

Haven't yet begun to play with the gain settings... just started with ele at 12 and ail at 11 and it seems to fly fine. I have adjusted the battery forward (using turnigy 3000mAH 20C - thanks for the rec james!) and the CofG is about perfect front to back.

THANK YOU ALL SO MUCH for your help. I have already flown through 4 batteries and it is like a dream! I can't believe how stable and responsive it is. Pictures and videos to follow.

[jamesb72]

Glad its flying good - interesting that undoing sensor strap helped tail wag - my tail is fine on the 500, but the 250 tail also seems to fidget regardless of gain, so might try loosening the sensor strap on that one to see if it helps.

Re headspeed, I'd push point 3 up a bit so throttle curve something like 0-60-75-85-100 (this is what we have setup on the 5003G with Align ESC, and it flies great, my 5003G has ICE75 governing headspeed).

I'd always have 100 as top of TC otherwise you have the wrong pinion, if you want 'flat' 90 on idleup/stunt I'd still use 100-90-90-90-100, a lot of people fly the 500 with 100% flat TC so you can go higher without any worries so I'd experiment with different headspeed to see what suits you and your style of flying.

There seems to be an issue with the Align ESCs that they have a power 'glitch' somewhere around 80-90, and above this you are full throttle anyway, so a lot of people set their TC to avoid this 'glitch' point - I found on the 250 when I was still using the Align ESC that anything above 83 was full throttle anyway, so my carefully setup TC of 100-90-85-90-100 was exactly the same as flat 100 anyway I've since put a CC25 in that so am running all my heli's with CC governor high now.

[modelfun2]

I am having troubles with my 3G system on my 500. All the controls function properly (left=left, rht= rht, pit=correct pit direct, etc).

The issue is that when checking the 3g system reaction to movement, it all works except the elevator motion/direction. When I move the nose down the swash moves in the same direction which would increase the nose down attitude and result in a crash. It is in the final assembly just FYI. I reverse the 3g and it does the same motion, no change. What is the matter? I double checked the connections.

[HiroboFreak]

When you say you reverse the 3G, do you mean via the 3G setup mode?
If the status light is changing colour when you reverse via the 3G setup mode, then it should be OK.

I assume you have tried going through the entire setup procedure again?
You may have a faulty unit.

[modelfun2]

Thanks for the reply. Yes I did the reverse on the 3g and tried it both ways (red and greeen led) the movement doesn't change. I have gone throug it several times and pounding my head.