BeastX tuning question

[greg.lloyd]

Just interested in some opinions on whether any tuning is required on the AR7200BX?

I've built a Trex 550e PRO DFC with AR7200BX and also upgraded my 450 Sport to FBL with AR7200BX.

Everything is generally very good, but my dial settings on both units are at the default 12 o'clock position.

I've noticed in the last few flights now that I'm watching things very carefully that the 450 will drift around just a little when there is a breeze. In no particular direction really, just not absolutely rock solid stable in the hover. It's performs great but stability is not vastly better than when it was flybarred.

With the 550 the hovers are much more stable (obviously it's a bigger bird). It doesn't budge in the hover easily at all and generally seems very locked in.

What's got me thinking though is that when I hover at a height in front of me and try to do some piros, the 550 is generally super stable - but it still can tilt off at an angle fairly easily during the move if I don't really concentrate on keeping it level. The 450 seems even easier to get out of whack during a piro. Piro compensation is correct on both and I can perform good flat piros with both - but I'm always concerned that either heli 'sometimes' tilt during the move.

Do I need to change the dial settings to improve the stability during these moves or is this more a case of my dumb thumbs and simply needing to practise at doing them better?

[tsangbou]

Sounds normal to me.... 450 will drift more than the 550.
Be sure to check your servos as close to 90 deg as possbile before you follow the setup guide.
I always make sure my blades are at zero deg +/- 0.5 deg.
May be worth double checking if your links are absolutely straight too?
Generally the dials at 12oclock is about right.

[greg.lloyd]

Yes, everything you have mentioned there is set up exactly on both birds.

Both have servo arms at 90
All links are straight and correct length
Both have blue light at 6 deg.
Pitch range is -12 / +12.
Blades are exactly zero at mid stick

So what might cause the heli's to go off axis slightly at times during piros (requiring a quick recovery)?

I should mention that I'm only at the stage were I've comfortable with forward flight, can loop the 450, flip the 450 - and now trying to piro both (haven't looped or flipped the 550 yet)

[waveydavey]

No, it's more your cog than anything else, the drifting off is to be expected I'm afraid the wind hits the cano and the result is it gets pushed off. The piro sounds cog related. The dials are a matter of feel, the first one being the overall gain for the cyclics. Look for any bounce on cyclic and lift pot 1 if you see anything until it stops, just above stock seems to work for most helis. The second one is defo a feel thing as it's the feed forward part of the control loop, so essentially how much of the stick command is fed direct to the servos, too little and it will feel slow and lazy too much and it will feel disconnected. The third one is tail dynamic and basically the control on the stop of the tail.

[tsangbou]

lol oh yes waveydavey is so right about COG too

[greg.lloyd]

And would COG issue manifest intermittently? Could it be battery placement? Some piros are totally flat. Then others will see the bird go off axis during the move. More likely when doing a slow piro than fast.

p.s. Good to know about the drift. It's not a problem and I expected some just have no previous experience with just how stable you should expect.

[greg.lloyd]

So just to clarify, increasing the cyclic gain a little won't make the 450 hover any more stable in a breeze? I'm maybe not understanding the role of the dials correctly. I thought that maybe increasing the gain would cause the beastx to react faster to any tendency to drift

[tsangbou]

And would COG issue manifest intermittently? Could it be battery placement? Some piros are totally flat. Then others will see the bird go off axis during the move. More likely when doing a slow piro than fast.

p.s. Good to know about the drift. It's not a problem and I expected some just have no previous experience with just how stable you should expect.

Just be sure to balance your heli and remember to place the lipo at the same spot every flight. Don't forget a different brand or c rating also needs to be adjusted to get a good cog.

Drifting is quite normal. If you want a very stable hover, like position hold then the NAZA H with GPS is good for that but then it defeats the fun of manual flying :S

[greg.lloyd]

I enjoy manual flying

I like maintaining the hover - just like with flybarred. Just wanted to ensure that I shouldn't be seeing something different with beastx fitted.

I'll be careful with the battery placement and I'll also check the COG of both birds on the bench. I generally am aware of trying to place the packs in the same position for each flight so they are never really in different positions as such but will pay extra attention for the next test.

[greg.lloyd]

Do you ever check COG before flight with the lipo in place (before connecting to power)?

[waveydavey]

A

p.s. Good to know about the drift. It's not a problem and I expected some just have no previous experience with just how stable you should expect.

It is stable but if you think about it, the heli isn't aware of it's position so there is nothing to lock to all the unit is aware of is that there is a roll, pitch or yaw input and to match the relative input with a corresponding rate. So in translation if you've asked the heli to roll at 5 degrees/s then the unit will add roll cyclic until the heli is rolling at that rate. So in the hover with no input the unit will only react to an external influence by counteracting it. So the heli will sit flat with no input but can't stop itself being pushed by the wind.

The piro thing maybe the battery position, not sure

[greg.lloyd]

Makes sense

What about level swash? The swash on both are level - but maybe not 'perfectly' level after previous tweaking. Would that potentially have an effect? There seems to be a debate about just how level they need to be with FBL.

[waveydavey]

All depends I suppose, the unit hasn't a clue whats happening so if the swash isn't level, and more importantly isn't at the same level/parallel with the swash then it will move as there is cyclic input. However, the BeastX has no idea that the heli is moving in whatever direction the swash is not level so can't do anything to correct it, as far as it's concerned it's level and there is no input to react to.

It's very important that you trim it correctly so if in the hover it's drifting forward then go into parameter A and trim in that direction a little bit until the drifting stops. Don't trim on the Tx as it will see this as an input

[greg.lloyd]

Neither bird drifts at all unless there is a breeze. The 550 never drifts really. The 450 will with a breeze of about 8mph or more. The level swash comment above was more during piro move which is really the only time I see something unexpected happen from time to time (more so with the 450). I'm just not sure if it's my technique though. I try not to make any cyclic inputs during the move.

I'm hoping to get to the club this Saturday if the weather is kind (it's forecast to be) and hoping someone will be able to eyeball me.

[Made2Fade]

I agree with the CofG that Dave is pointing you towards. Have you also increased your cyclic gain until the point your cyclics oscillate and then back it off a tad (just like when your setting tail gain)? Tweaking that better will help also. The cyclics can over compensate and this can also show up like what you are seeing. You could also be putting a command in without knowing. Try some expo

Also...
nothing to do with your problem but the tail holds much better on the BeastX when you setup normal rate mode also.
You will get much more drift on a 450 bird than a 550. They are so light that the wind affects them much more. You need to be on your toes more with the small birds
Larger models are always easier to hover because they have more hang time so naturally feel more floaty if that makes sense. That coupled with more weight = less easier for the wind to push around. This goes for a fbl or fb model.