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Throttle and Pitch Curves for Trex 500 help

#1
I've been trying, with little success, to confidently hover my 500 around my yard. I took my DX6i and my 500 to the guy at my local hobby shop and he made some adjustments to the Throttle and Pitch Curves and then he disappeared. Can you believe that???

I took my 500 home and fired it up. It seems very "lazy." I would like to be able to hover in one place without bobbing up and down dramatically. I'd like to share with you my Throttle and Pitch Curves. Would you please help me by making suggestions?

Throttle
Normal - 0,30,60,75,85
Stunt - 85,85,85,85,85

Pitch
Normal - 45,47.5,50,75,100
Stunt - 0,25,50,75,100

I would like to be able to flip the idle up switch, but when I did that last time, the 500 jumped into a vicious rampage of rpm's and spun wildly followed quickly by a restful nap in the dirt.

I have no intention of any 3D of any sort right now. I just want to be able to fly this thing.

Can you help???

Thanks!
 

Ak Flyer

Fly the wings off
Mentor
#2
HI,
I apologize if I'm telling you stuff you already know but here goes.
I would forget about the idle up for a while. When you idle up your head speed goes way up and that makes everything respond way faster. With higher head speed you are getting more effect out of your pitch changes so it feels twitchy. Sounds like your tail isn't holding when you hit idle up. You usually want to be in the air and be somewhat close to your max head speed when you switch to avoid the rapid change. One thing you definitely don't want to do is decrease your head speed to the point that you can't recover if it's dropping. Without knowing too much about your helicopter or your flying or setup skills, I would suggest a few things first. Make sure that your swashplate is level. Check it at mid stick, then at low and high positions. It should remain level throughout the pitch range unless you input a cyclic command. Then, with your throttle stick at mid point, you should have zero pitch on your blades. This is pretty important as all your settings in your radio are in reference to this point. In fact, when you are doing these checks, go into your radio and see what the reading is. I have a DX8 and it's a bit different but you should have a menu in there that shows the position of all the servos. Mine calls it monitor. Anyway, find zero in your radio and mid travel in your servos and that's where you zero the blades.

Now for throttle, I would use a linear throttle curve, I leave mine up to 100 on normal. This will give you a little more headspeed at mid stick and will improve the crispness of the feel but that's up to you. If you feel you have enough speed or are uncomfortable with it go ahead and dial it down but again don't go so far that you don't have enough and you end up using too much pitch.

For stunt, you can put in a v curve, I wouldn't go linear. Try 90, 80, 70, 80, 90 or something like that. That way you have a constant high throttle but it's won't have that hard hit. It will be a minimum 70, and as you increase the pitch and load it will throttle up to as high as 90. As you get better you can always dial it up.

For pitch, I would probably go lower on your low end, around 30, 40, 50, 70, 90. Then on stunt, I would do it the same. Don't add any full negative pitch until you are more comfortable with your heli. The reason being that when you first start using stunt or idle up, you tend to bounce them off the ground and break the landing gear. Until you get used to the faster reaction from the higher head speed, keep the negative pitch a bit softer. From my reading it seems most pro pilots still have a softer rate for taking off and power on landings (not autorotations). Once you have become comfortable with the higher head speed, go to a linear pitch curve 0-100 on your stunt pitch. Then you can tailor it from there.

I recommend starting a journal of all your settings. Keep a dated timeline of your mechanical and radio settings every time you change them so that you can track what's working for you and you can always go back to a good setting if you end up with a bad combo.

The first thing though, triple quad and quintuple check your mechanical setup. Make sure all your servos are at 90 degrees to the swash plate with everything at mid stick, take out all trim and sub trim, level your swash throughout the range, and check all your radio settings mechanically to check for binding and things like that. Unplug your motor when you do this for your own safety.

Once you get it spinning, make sure you track your blades. This is very important because it can rob power and lower your headspeed by inducing vibration which will ruin helis and it throws off gyros really bad.

Also balance your blades. I finally invested in a blade balancer when I stepped up to a 550 nitro but I also balance my 450 blades now and it makes a huge difference. Everything works better now.

There's a few other heli guys on here that I expect will have some more ideas for you. Welcome aboard and please post some pictures of your heli. We love pictures. Advice is free but pictures get you more of it. Good luck.

Ak Flyer
 
#3
Ahhh, very cool! Thanks Ak Flyer! I'm going to print out your response for reference. I'll be sure to check the mechanix, but I believe they are all in working order. I appreciate your help and I'll see about getting some pictures together.
 

stevec

Junior Member
#5
Another thing is the Trex 500 loves headspeed.

Mine used to nod in the hover at anything less than about 85% throttle.
Depending on the head/tail ratio then running a lower headspeed may stop your tail working as it should.

Agreed about the pitch and throttle curves, there are many ways to skin that cat. I tend to set my throttle in normal mode 0-60-75-85-100 so I don't loose headspeed on final approach. but you will find what "flavour" you like the most as your confidence increases and you play with the settings.

personally if you are a total beginner I'd leave the negative at a max of minus 3 until you get out of the habit of slamming the throttle closed when things go pear shaped. you shouldn't go through too many tailbooms then ;)

/Steve
 

Ak Flyer

Fly the wings off
Mentor
#6
personally if you are a total beginner I'd leave the negative at a max of minus 3 until you get out of the habit of slamming the throttle closed when things go pear shaped.
/Steve
Absolutely. I meant to bring that up. It's very easy to slam your heli into the ground whenever you get nervous or try to shut down quickly if you have lots of negative pitch. Every time you try to power down you add negative pitch unless you hit the throttle hold. When you start using the idle up mode a lot, you really need to get used to hitting the throttle hold as it will save you tons of money. That needs to be your first move when things go wrong but it's something you have to program yourself to go for instead of chopping the throttle.
 

Dark_fox

Junior Member
#7
Another Trex 500 pilot here, I fly mine on 100% throttle at all times. The Trex 500 requires REALLY high head speeds to keep stable, it can sound like its going to explode but never really does.