Nose pitches down during turns - Help

[arias51]

So, I received my V1 450X back from Horizon Hobby after plowing it into a tree, the only issues they indicated on the repair invoice was 'Needed to be leveled and configured setup G in Beast X'

Seriously?!!

It was painfully obvious the front servo was completely stripped (among other issues) but I won't even go there.
I'm so done with HH support.

So anyway, I stripped the head and replaced every damaged part, swapped out the servo with a new one and went through the beast X set-up. Everything is balanced and set-up correctly, but I am having only 1 issues now. The heli wants to pitch nose down badly during any sort of turn. It is especially evident during FFF. Any ideas?

Nothing else seems to be wrong with it... hovers fine, flies straight no drift. Only seems to happen coming out of a turn.

[arias51]

Anyone have an idea? I swapped my main blades out for the stock ones and made sure the swash was level at both high and low endpoints. Took it out today and still doing the same thing.

[chuk]

Maybe a cg issue?
Mine was doing that for a while until I ditched the Spektrum and went with the Bavarian Demon 3x, just had it out and it was doing very nice, adjusting the decay rate in the head gyros brought my nose right up.
Don't know how to deal with it in the AR7200 other than physically balancing the cg.

[Dawiev]

Perhaps menu N needs to be reversed from its current setting ?

[arias51]

Not sure about the CG, but the fact that it hovers OK would kind of rule that out I would think. I'm kind of invested in the AR7200 at this point. I do have another I could swap out from a V2 450X maybe i'll give that a try to at least rule out the BeastX being the issue. I did a factory reset on it as well, so everything should be set up to stock settings in case I had inadvertanly changed something. I know if I call Horizon they'd just tell me to send it in, so i'd like to avoid that possibility as the last time they had it nothing was fixed.

[Dawiev]

Hi, I have no personal experience with this going wrong, so please accept the suggestion in the spirit given.

Menu N is for " Pirouette optimization direction " and I guess it doesn't come into play during hover.

There is nothing else in the menu settings I could see to affect this and I don't know enough about parameter H (pitch boost) which is the only thing in the parameter list to affect altitude ?

[arias51]

Tested it out and it appears to be tilting at the correct angle as I rotated the heli around the main shaft.

I can't imagine i'm the only person this has happened too? I did see one post regarding the same issue, but his problem turned out to be with a loose main gear/shaft. Don't have an issue there. Adjusting the front link only makes the heli drift backwards (as it should) but doesn't effect the nose dive problem at all.

[night wolf d]

Have you replaced or checked the bell crank transmission shaft ,part (#28)to see whether there is any wear or damage , ie rounding after your mishap?
I can remember a post a long time ago that turned out to be the bell crank slipping with pressure during flight but seemed ok on the bench.
Check out the bell crank could be your problem.
Also how loose are your main blades?

[arias51]

I'll have to look at the parts list to see where that is located.
I've tried various tension on my blades. Right now they are a bit stiffer then I normally have them set. Usually I have them a notch tighter to where I shake the heli gently they will move on their own.

[night wolf d]

Sorry not #22 ,it's #28.
Edited above post.

[ManInAGarden]

Very often strange problems like that turn out as caused by vibrations. Maybe these vibrations only occur when the tail rotor has to work hard (like in a fast and tight turn). I'd check that vibrations cannot be transferred from the main chassis to the beast. You know - thick and soft glue Pad underneath the beastX, no cable ties around the beastX and curved cables near the beastX and things like that.

[Mark M]

Did you replace all the parts in the head and made sure the bearings where properly seated on the feathering shaft? I've had some erratic issues in the past which has turned out to be a very slight bend in my feathering shaft and some worn dampeners. If your mechanical setup is good and all the servos are setup well, have you reset the model in your radio?

[arias51]

I swapped out the entire head and made sure the bearings were seated correctly. I did notice one of the bearings was damaged on the old grips though.
I actually called Horizon and spoke with a tech guy who said he was stumped. He stated he flies a 450X and never had that happen to him, so he was going to ask the other guys to see what they thought and give me a call back. I asked if I should swap out my BeastX with the spare and he thought that was a good idea, so that's my next step. At least I have a V2 that is flying well so, it's not like I can't fly at all. Was using this one as my beater to try new tricks on without the fear of crashing. It helped me in that area as I began doing tricks that I would not normally do. I'm not too concerned about getting it locked it perfectly, but this nose dive issue worries me a bit. Maybe
I'll swap out the transmitter to see if that is the issue, if not i'll try some of the other suggestions.

Could be tail vibe issue as I noticed it is a bit twitchier then my V2, but I did put two layers of 3m under the transmitter. This has got me a bit stumped as well.

[Nelsonisms]

I wouldn't take that "gee I've never heard of that happening" line from Horizon too seriously. They use that one all the time. They said the same thing to me when I called to report a motor that failed in my 300X after about a dozen flights. A quick search of the forums showed that it was a fairly common occurrence, but of course their reaction was "hmmm, that's odd. I've never heard of that happening before."

But I'm not going to guess as to what's going on here. I'm sure I could figure it out if I had it in front of me, but it's way too difficult to get all the details here. I'd suspect the servos, but that's just a gut feeling.

[TomC]

A couple of things come to mind. Firstly, re-check your tail boom/tail case alignment. If it's twisted it will effect fff and turns.

Secondly, raise the ar7200bx head gain a little (pot# 1) by turning it clockwise from its stock 9 o'clock (horiz) position to ~ 10:30 o'clock. This should make the head feel a bit more solid and may help reduce pitching up/down. Pots #2 and #3 should be fine in their stock 9 0'clock positions.

If no improvement, then I would suspect one of your cyclic servo's may be faulty/weak. Try moving them a little after you initiate your ar7200bx and see if any move easily. Just a wild guess, but I would suspect it's your front elev servo.

Cheers,
TomC

[arias51]

Thanks Tom. Haven't had a chance to test anything yet as the weather has been dreadful.
I'll check the tail and see if I notice any alignment issues. I think i'll swap one of the rear servo's and move it to the front to see if there is any difference. They were brand new out of the box, but it's worth a shot anyway.

[TomC]

Originally Posted by arias51

Thanks Tom. Haven't had a chance to test anything yet as the weather has been dreadful.
I'll check the tail and see if I notice any alignment issues. I think i'll swap one of the rear servo's and move it to the front to see if there is any difference. They were brand new out of the box, but it's worth a shot anyway.

Also check that your servo arms are screwed on firmly. Sometimes these get a little loose and you end up getting a bit of free-play on the spline.

Cheers,
TomC

[arias51]

So I was able to get the heli out today for some testing.

1. I started by swapping out the BeastX, nothing changed. Heli still responded exactly the same.

2. I went through the head again and made sure the feathering and main shafts were not bent and switched the swash plate with a new one. No difference.

3. Made sure tail belt was correct tension and nothing was bent.

Ok, here's where I start to question if I am balancing my swash/blades correctly...

I use the blade swash tool in Parameter 'G' after I center all of the servo horns.
Then I use my digital pitch gauge and place the blade over each of the servo to swash links to make sure they are all at '0' pitch. I have done this many times with my other hell's and they usually balance out fine and allow me to center the swash percicely.

This time I just used the blade swash tool and left out the step where I try and get all of the links exactly the same. When I was done I put the heli at mid stick and used the pitch gauge to see what the readings would be at 4 different points on the heli (front, back, left, right).

The gauge was reading '-1.7' degrees at the back, positive 1.5 at the front, -1.0 left and 0.5 to the right. I took the heli out and with some minor tweaks to the links was able to get it to fly straight with only a slight tilt down from the nose.

I'm kind of at a loss here. I have leveled the swash on my V2 making sure it was 0 degrees at all 4 points and it flies just fine. Why is this one so far from 0 pitch but flying better?

Am I leveling the swash correctly? When I made sure the swash was perfectly leveled it did the nose dive. This is also similar to how I got the heli back from Horizon. When I put the pitch gauge on and went to mid stick none of the axis were perfectly leveled. They stated they had to level the swash which also confused me.

So what am I doing wrong?

[TomC]

One thing to remember in parameter G, you need to leave it with one set of lights on and move to the next parameter to actually save it. Otherwise it goes back to the default reference setting.

I use G to (in order); Get all arms at ~90 deg, level the swash (eyeball method, never used a swash levelling device over the past +10 years), and adjust pitch on both blades to zero degrees (using a pitch gauge). Then I save these settings by moving onto the rest of the setup making sure one of the a.e.r lights are still on.

After this, the only adjustments I make are at the field. After checking/adjusting the blade tracking, if the heli drifts a little in a hover and/or fast climb-out, I just mechanically adjust the swash accordingly. I sometimes also need to check/adjust my mid-stick to make sure it's still at zero degrees pitch.

I cannot say for sure but I think you may be over-thinking all this. Just get your heli flying well (and vib-free btw) and don't get too hung up on too many numbers imho.

If you get stuck, try to get some good local heli advice/help.

Cheers,
TomC

[arias51]

Tom, I do like you said but my anal retentiveness makes me want to have the swash perfectly level.

I use the swash leveler to get a general position then use the digital pitch gauge to get it perfect, but for some reason it just doesn't want to work using this method.

I just went to the field and made mechanical adjustments to the links and that seems to work. Just confuses me why the pitch is so off from front/back and Left/right, but it is flying ok now.

I guess that's good enough... I don't really need to get this one perfect as i'm just using it as a beater.

Anyway, not going to rack my brain on this one. Thanks everyone for the help.