Slight right drift on new setup

[JTAnimal]

So, like the title says. I get a right drift in the initial hover. Goblin KSE 3 blade, it has been flying with a VBar for 6 months, or so. But I put a 3SX on my Goblin 700 comp and liked it so much that I wanted it on my 3 blade KSE. So I did the test flight today after a very thorough setup, and I'm getting this drift. Trust me when I say the drift is not correct. What bothers me is that I brought it back and went through my setup again and I have this heli setup better than my 2 blade 700. With the head off, using a swash leveler, the servos are level through the full throw, neg to pos.. All 3 blades are showing the same figures, with 13 deg pitch neg and positive exactly even. I have checked them several times. I just don't see the problem. CG was slight nose heavy, but not bad, and keep in mind this heli has been flying great, the only change has been the FBL unit.. Any ideas of what to look for. Maybe some change for the 3 blade, that I may not know about?

[AndrewJHawes]

Hi JT,
Are you aware that there is an adjustment in the 3SX for offset angle in the hover to counteract tail rotor induced drift? Maybe this requires slight adjustment.
Andy

[JTAnimal]

Nope, I'm a VBar user. Just started trying the BD because I won't buy a V radio I liked it on my first setup. Where is this adjustment? What page in the software?

[DEMONjoe]

The drift is normal, when you did not fine tune the trim yet.
Use the linkages to adjust the swash against the drift, done.
There is a reason why you never noticed this with another brand's unit: most (if not all) others hold way harder than we do. That's why we need a slightly more accurate mechanical setup on the heli. And this is the point where people learn again, that swash leveling tools are the world's most useless tools ever, especially for a completely not symmetric flying object like a heli

[AndrewJHawes]

Hi Joachim,
Obviously, the 'lateral' drift in the direction of the tail rotor thrust, is normal with most helicopter tail rotor configurations, and the craft will need to roll to compensate for this drift. However, my understanding from the 'explanation of functions' on the 'Advanced' screen within the 'Horizon' window, is that the 'Neutral Roll Adjustment' function informs the BD3SX that this degree of roll is 'Normal' in hover, and not to try to fight against it. Am I wrong in this assumption, I have just assumed this was the way it worked (I know this function also potentially compensates for offset main-shaft angles).
Clearly, the swash linkage adjustment will also fix this.
I think it is certainly necessary to accept that helicopter dynamics are very complex, and that they are inherently pretty unstable to the point that we should always expect to be constantly making small corrections. The flyer who expects his helicopter to just sit in hover will be sorely disappointed!
Appreciating your insight.
Andy

[JTAnimal]

Well I'm confused..

[AndrewJHawes]

JT, if you trim your helicopter, you will compensate for this drift. This can be achieved in several different ways.
Generally, most FBL systems will try to disuade you from making further trim adjustments in the transmitter after initial set-up, as these trim adjustments in the transmitter can then, subsequently, potentially lead to complications with interactions under differing circumstances, hence the subsequent 'mechanical' swash plate trim adjustment.
This has always been a component of the model helicopter trimming process. With the advent of FBL systems, being capable to some degree of compensating for mechanical set-up defficiencies, many pilots are relying more and more upon the relative abilities of the FBL unit, and losing touch with the art of mechanical set-up.Your helicopter will always fly better if it is set as well as possible mechanically.
The reality, unfortunately, is that helicopters are dynamic beasts and this degree of trim, however perfect for a stable hover, will still not give perfect results under all conditions, and we still have to 'fly' the machines.
Trim your machine as well as possible mechanically, and then go fly it, and enjoy it.
Andy

[JTAnimal]

I guess that's what I'm having trouble with, I have it mechanically perfect and was flying it, all was well. Now I put another controller on and my setup is messed, and mechanically I need to un-level it. Ok if that what's up. I always did this in the beginning, when I first started flying with flybars. Drifting left, move the swash to the right. But I have not done that for a long time. Maybe I should have left it alone, live and learn..

[AndrewJHawes]

JT, I wouldn't worry, it will fly fine, in fact I am sure it will fly superbly, but it sounds like you don't do too much - 'just hovering' with your experience, either anyway. Have you really flown it? I have to admit that after I have got the swash as level as possible, I rarely make any further adjustments, and go fly, and enjoy. I rarely get a perfect hands off hover - either I have drift with wind, turbulence, a little tail thrust, but I just fly the 'hover', and compensate as always.
I am sure Joachim will contribute further, he is the expert in this area with the BD3SX, however, I doubt that will happen until after Easter. Maybe, he will even get a chance to go out and have a fly himself!
Regards,
Andy

[AndrewJHawes]

JT, what I really meant to say is, that firstly, I probably wouldn't call your set-up 'all messed up' (obviously I haven't seen what you have got), and secondly, my own preference is to try to level the swash as well as I can, and then leave it, and not make any further adjustments, other than for zero pitch, etc.
I do, however, think you need to make DYNAMIC adjustments in the wizard, as necessary. My own experience comparing BD3SX and Vbar, and others, is that Bavarian Demon flies superbly well!
Regards,
Andy

[JTAnimal]

I don't just hover a 700 class heli. I throw it around. But not until I know it will fly good. Once I am confidant in the setup, I fly as hard as I can. Thanks..

[F1 Rocket]

Pretty simple adjustment. No need to pull your hair out Start with a perfectly level swash when setup on the trim page of the BD software. Fly the machine. If the machine has a lateral drift in hover adjust the left/right swash links to cancel this. You can also use the servo trim on the Trim page but I find it easier to just crank the links. Longitudinal drift should be adjusted by changing the longitudinal CG on the machine.

[JTAnimal]

It's cool I get what your saying. Mechanically. I just have not done it that way on other systems, so I'm not use to it. Also my first unit with a BD did not need this. I was surprised, I figured it would be a adjustment in the setup software. Too windy today to try, maybe tomorrow. Thanks again, I'm out..

[AndrewJHawes]

JT, I am sorry. I re-read one of my earlier posts, and it sounded like I was suggesting that you just 'hovered'. My intention was not that at all, but to suggest that I suspected just the opposite! Sorry for the confusion, no insult intended!
I find that for most of my craft I need to make minimal, if any, swash trim correction, but some correction would certainly have the desired effect.
Andy

[JTAnimal]

No worries mate I love Ausie, had a great time in Perth. Good people in your area of the world. I just wanted to be clear, ya I'm new with BD but not helis. Some of the post you see, you kinda wonder if they should be flying a 700..

Still too windy to be sure, I did one full up turn on the righ aileron, but that seemed to put me back on the tail. I lowered that back and did half turn down on the left and it seemed better. But again, with 10 mph winds I don't think I'm going to get it perfect until I can try with no winds.

[AndrewJHawes]

Good to hear mate, I hope the wind improves for you soon.
The unit really does fly well, especially the tail is superb.
You will find that the 'explanations' of the functions are quite useful if you hover your mouse over the adjustment area of the set-up wizard.
Like every good system, though, requires a little tuning, eventhough, for many starting out it does give a good approximation out of the box on default settings as recommended. Good luck.
Andy

[JTAnimal]

I agree, my 700 has been flying good. Except today rescue wouldn't work. I remounted the RX and I plugged aux2 in backwards. I don't use any self leveling, so I didn't know until I tried to test rescue, then I didn't work. I found my mistake. But that's on my 2 blade 700.

The one I'm still trying to get correct is a 3 blade 700 and I'm still trying to get the gain right. Need a calm day. I think it's close.

[AndrewJHawes]

JTAnimal, I will be in the same position by the end of next week, as I will be receiving my Compass 3-blade head, hopefully. I am, expecting the head gain should be not too far from the 2-blade, even though it is a far more rigid head (3-blade). I don't use the variable damping 2-blade head at the moment, but the 7HVU 2-blade with swash driver.
Andy

[JTAnimal]

So to finish this thread. The problem was the mounting of the 3SX. This was in a Goblin KSE 3 blade full carbon canopy. I had a Spektrum carbon RX that I used, just to make sure I had good reception. I mounted the the 3SX on top of the Goblin RX mount, RX on the underside, was the cleanest setup. But the wires on the BD 3SX go straight up. The wires were getting blown around causing the strange drift. Removed the Goblin RX tray and remounted the BD down lower and receiver on the side and now it flies great.

So my lesson, don't let the wires go up too high. They can get blown around, causing strange problems..

Thanks for the help.

[AndrewJHawes]

Yes this sometimes can be a challenge. One needs gentle sympathetic curved connections, rather than sharp bends, but then, maybe, bundle the cables and secure to an adjacent panel to avoid connector movement at the 3SX end.
I find that a heli build generally takes between one and two days, but that the wiring takes about four days, twice as long as the build. Two days to think about it, and two days to try to get it right. Then, I'm generally not happy about it for a long time, before ultimately giving up and accepting the compromise! I hate wiring, and I'm not committed enough to change default wire lengths yet, not confident in my connector changing.
Andy