pitch control issues

[dge123]

This is my first 250 heli. All I've flown in the past have been Blade.
I have an Align TREX 250 plus. I'm have issues with pitch control.
First, when I"m in TH the pitch become inoperable. That isn't normal to
me. Non of my Blade's ever behaved that way.
Also, my full collective seems to be off. When I test flew it I needed almost full collective to maintain altitude. That felt odd to me also.
I have a pitch gauge and It shows to have 11 degrees at full pos. collective stick. But I can not achieve the same at neg. stick. It falls short of 11 degrees by about 2 degrees. I have played with the travel and came close to an even 11 degrees but when I flew it it took alot of collective to maintain a hover.
I am using the stock 3gX flight controller. I have checked and double checked all of my radio settings (DX8) and have found no errors. I need some help with this. I've yet to fly this heli yet apart from a short hover.

[Toocool4]

Are you using the same pitch curve in TH as you are using in your other flight modes?

What head speed are you running? If you are running too low a head speed, you will need more pitch to lift off and to maintain hover.

Some times it’s hard to get the positive and negative pitch to match on a 250.

You need to go through your setup again to fix all the issues you are having.

[dge123]

My pitch curve for TH is set at 50%. My head speed is set at 90%.
I suppose that's the reason my pitch is inop at TH.
What's a good way to get my pitch even?

[Toocool4]

For me my pitch curve is the same in all modes hence no surprises in whatever mode I am in.

For the uneven pitch all you can do is try and move the swash plate up or down to try and even out the up and down movement of the swash.

[myxiplx]

Your pitch is probably close enough for flying, I don't worry about getting it too close on the bench. If you really want it even its best done in flight, I just do a full pitch climb out upright, and another inverted, and adjust until they're about even.

If you're needing a lot of pitch though your headspeed may be a bit low. The 250 generally likes higher headspeeds, 4100-4200 is where I do most of my flying.

If you haven't got a tach, I can recommend picking up an app for your phone, you just set the app running and then hover over the phone for a few seconds. They're pretty accurate and easy to use.

[dge123]

I raised my head speed to 100%. Still no improvement.

[Toocool4]

When you spin the main blades by hand does it move freely?

[myxiplx]

We still don't know what headspeed you are getting, knowing that will help a lot in narrowing down what's going on.

It could be the motor, wrong pinion, the ESC may need calibrating. But if you're getting 4100rpm already we can largely rule those out.

[dge123]

I'll get me a tach and measure head speed and I'll post it when I do.
Thanks

[Toocool4]

When you spin your main blades by hand does it move as freely as the one in this vid?

[dge123]

Yes it does. Could you recommend an app for a tach?
I do appreciate your feedback. Thanks.

[nflanagin]

I have a pitch gauge and It shows to have 11 degrees at full pos. collective stick. But I can not achieve the same at neg. stick. It falls short of 11 degrees by about 2 degrees. I have played with the travel and came close to an even 11 degrees but when I flew it it took alot of collective to maintain a hover.
I am using the stock 3gX flight controller

Mine started as a plus, but due to crashes it's now more or less a DFC. One thing I had to change was I setup the neutral travel. I set my TH pitch curve to 0-25-50-75-100. Then I adjusted the servo links to get the swash to the mid point of the throws and the transmitter should read that it's at the center line. Now adjust links to get the swash level. Then with your pitch guage, adjust the DFC links to get the blades back to zero pitch.

Check your center position on the 3gx mrs using the push buttons per the manual. I'm not much help here because I sent it in for a vortex trade in.

Clamp it down, check blade tracking and adjust as necessary and you should be good to go.

[myxiplx]

Originally Posted by dge123

Yes it does. Could you recommend an app for a tach?
I do appreciate your feedback. Thanks.

I use one on Android called "RC Tachometer" by Stefan Scherrer, I just set it running and put the phone on the floor a safe distance from the heli, then takeoff and hover over the phone for a few seconds before landing.

It's always worked well for me, and correlates well with the RPM I have set on my governor when I enable it.

[dge123]

Ok, thanks. I just hope there's an iphone version.

[dge123]

I measured the head speed. It topped out at 5000 rpm. It just seems like it takes too much stick to maintain a hover. I don't really know if I'm expecting too much. I just know all my other micros really popped when you gave them full collective stick. This one not so much.

[alyon187]

5000 for a 250? Thats nuts.

[myxiplx]

At 5000rpm it should be a monster, that's more than I ever heard somebody run in a 250.

For comparison, this was my 250 earlier in the year at 4500:

Trex 250 SE @ 4500 rpm (4 min 5 sec)

Have a listen to the video, does yours sound like its running that fast, or does it sound slower?

[dge123]

It's hard to tell. But mine won't pitch pump like that one does.
I do have the throttle set at 100%. I did that to see if it offered any
improvement. I'll turn in back down to 90% as recommended.

[myxiplx]

I'm thinking it could be a couple of things. One is that maybe your tach app wasn't setup properly and you're actually seeing a fraction of 5000rpm.

But if you're sure you are getting 5000rpm then I'm thinking a servo issue, or binding in the head under load.

It could potentially be your one way bearing slipping too I guess.

If you were actually getting 11° of pitch at 5000rpm it would be a rocket, so one of those two simply isn't happening in the air.

Do you feel any notchiness in the head if you twist the grips by hand, especially when you pull on the blades?

[alyon187]

Are you sure your pitch range is set correctly?