Programming pitch curve.

[Stuey]

Hi everyone. I will be setting up the pitch settings on my Trex 450 plus dfc soon with my digital pitch gauge. This might be a daft question so bear with me! I am going to program it with a curve of -2, 0, 3, 5, 8 degrees. I take it I set it up with the 5 point pitch curve in the tx? Thanks :-)

[Grumpy]

Yeah, you would need a 5 point curve to do it exactly as you suggest. Alternatively you could use a simple 3 point curve -2, 3, 8 degrees which would give you virtually the same shape curve (within half a degree).

Obviously that will give you a very mild setup suitable for gentle upright flight only, but i guess that's what you are looking for.

[Mike Sanders]

This is great. We used to get this sort of question a lot on the forum and there were always plenty of experienced people keen to help. I hope that this will continue.

I am not really good enough to give you an accurate answer. I take it you are a beginner? I presume you will only have the one pitch curve for the time being?

If so, I would think the answer is yes but there are far more knowledgeable people on here who will give you better advice than I.

[Stuey]

Thanks for the replies. I have flown fixed wing for many years, and race rc cars too. I have the phoenix SIM, and a blade 120 but yes I am basically a beginner. I have no interest in flying 3d at the moment, so that's a curve I have read is a good collective starting point. I am thinking I can add a bit more as I get better. I might set the idle up to the same curve but a flat throttle curve to get used to using the switch.

[Mike Sanders]

Yes, that seems a good starting point. As your ability improves you will become able to decide for yourself how you wish to modify it.

[coolice]

Hey buddy.

What transmitter do you have? This will give us an idea how to help you add points if possible.

Also, I'd ask where you eventually want to go with the helis with reference to either 3D or more sport/scale flying in the future?
My reasoning behind this is that if you were to say 3D, then I would suggest setting up the model with zero degrees pitch at mid stick, so as to get you used to this way from the start than have to adjust your collective management later on. So you would then be looking at say -2, 0 (mid stick) and +8/10 at top stick.
A disadvantage to this is that it makes the collective a little sharper, squeezing 8/10 degrees of collective pitch range within half a stick movement, but we can soften this with the use of the 2nd and 4th pitch curve points perhaps if your Tx allows us to utilise them.

This is where my question comes from really, as having been there in many years gone by now and having to adjust to a 3D type curve which is symmetrical either side of centre, I now have all my students learn their collective management that matches where they eventually want to be.

Also while you're doing it (if looking to aspire to 3D eventually or other even), setup the model for the full pitch range of say -10 / 0 / +10 (without binding at the extremes) and we'll use your transmitters pitch curves to limit what pitch you get in each flight mode.
Then as you progress you won't have to necessarily revisit the setup as such, but just dial in more pitch range from the transmitter.

Ian Contessa

[cjm180]

Hi

I am sure this may get a debate going, but I would advise against doing that and going with what Ian says.

I started with a similar curve, and I can tell you it took me a very long time to re-train myself to have zero at mid stick and hover at approx. 3/4 stick.

even if you have little interest in 3d, a curve like that will not really allow you to do rolls or loops, especially if you get into a little trouble.

Its best off, as a beginner to set up at 12 degrees top and bottom with a linear pitch curve. Then you can simply tail off the lower half of the pitch curve to -2, but leave the upper part of the curve zero at mid stick to +12.

It will be difficult at first, but it will stand you in a good place going forward.

Kr
Craig

[waveydavey]

Agree with Ian and Craig

[Stuey]

Thanks for the advice. I have a DX6i I am using for my 450, so it has a 5 point curve. To be honest as very skillful as 3d flying is, it does not do much for me and I would say at the moment scale/sport flying is where I am aiming at. I think the mechanical setup at the moment is swash plate in the middle of the shaft for 0 degree pitch, so it should have the full plus and minus range available. I understand what you are saying regarding the position of the stick for a stable hover, my plan was to add a degree at a time when I feel ready to increase the range of pitch travel and not radically swap from one setup to another.

[DaveJones]

Also in agreement with Ian's suggestion, personally I like my pitch curve to be a 45 degree line so I get a consistent response as I move the stick, you could limit the curve so you don't get -12 degrees but a consistent line will help. I can pretty much guarantee you will want to loop and stall turn (which is sport flying) and you will need some negative pitch for these (try a stall turn on a windy day, the negative pitch prevents the heli being blown with the wind)

Whilst on the subject also consider what your throttle curve looks like. Lift is a combination of head speed and pitch, changing head speed changes the lift even if the pitch stays constant. Head speeds takes a little longer to change which is why on fixed pitch helis it can be tough to control height. I would suggest you set up a flat throttle curve, some people like zero stick to be zero throttle, but from 25% stick upwards a flat throttle curve will give you consistency. Personally I have a flat throttle curve all the way across and configured two throttle hold switches on my radio to prevent accidental spool ups (plus alarms on the radio to force me to activate throttle hold when switching on the radio)

[coolice]

Thanks for the advice. I have a DX6i I am using for my 450, so it has a 5 point curve. To be honest as very skillful as 3d flying is, it does not do much for me and I would say at the moment scale/sport flying is where I am aiming at. I think the mechanical setup at the moment is swash plate in the middle of the shaft for 0 degree pitch, so it should have the full plus and minus range available. I understand what you are saying regarding the position of the stick for a stable hover, my plan was to add a degree at a time when I feel ready to increase the range of pitch travel and not radically swap from one setup to another.

Hey Buddy.

Ah cool, with the DX6i you can use the pitch curve points to your advantage and limit the amount of available pitch and also soften the response slightly in the top half of the stick as well.
I used to fly a tick style pitch curve, with my zero being somewhere between 1/4 and 1/2 stick position and I was always asked how I flew 3D with the zero point away from the mid-stick position. My reply was I'm used to it, as I flew F3C competitions hovering was a big part of the rounds so my machines hovered at mid-stick and the collective range was expanded to aid smoother hovering.
Of course as I got more into the 3D for fun, I sampled the benefits the zero centre stick setup gave me and have now stuck with it.

Having said this, I've had students visit me that want their machine to hover a little closer to centre (mainly the older fliers who want to aspire to scale later on), so in this case it's very easy to add even 5% to the mid stick point, which lowers the sticks position for hovering very slightly compared to a true zero centre setup.
But as above if you aspire to sport flying, which encompasses loops & rolls in most cases, I would get used to flying with zero centre now rather than having to re-adjust your flying style/brain training later on.

With regards to the top stick pitch setting, don't fear flying with +10/11 degree's available, just becasue it's there doesn't mean you have to use it and you might find it more comfortable. My reasoning for this is that, in my case for example, I don't like to feel my fingers too close to the top of the Tx casing, thus I run +13 at the top, which lowers my throttle sticks position hovering point. The knock on effect is I have a livlier collective response, however I calm this down with the use of the 3/4 pitch curve point and the EXPO switch which is available in the DX6i's pitch curve I think? Been a while since I've looked as a DX6i.
What I do is lightly "S" curve my collective pitch line from the mid-stick to full stick position, this essenstially adds exponential to my pitch curve. This has the effect of softening the response when I am in this shallowed band while hovering around and making small collective changes, but still allows me full collective range if I push the stick higher up.
It's difficult to explain, but I will grab a photo of my pitch curve which will help explain it better.

In any case you will soon find a setup which works for you and this is what it's all about, taking other peoples knowledge and using it to your advantage.

Ian Contessa

[Grumpy]

Stuey,

I'll add my voice to the choir.. I started helis with a similar curve to the one you proposed but I pretty quickly found that the symmetrical straight line '3D' curve worked better for me, even for sport flying. With a very mild 'flat' curve I found that I couldn't respond quickly enough, the 3D curve does make collective more sensitive but it also means that you can 'catch' the heli quicker if it balloons or sinks suddenly.

Only caveat is that a 3D type symmetrical curve doesn't play well with a 'normal mode' throttle curve (because it means that you would be spooling up with full negative pitch). My fix for this is simply not to use normal mode, just 'idle up' for all flight modes and start and stop with the throttle hold switch.

But each to their own, if you want to try your proposed setup first that's fine, just be open to adjusting your curves according to how the heli feels in flight.

[coolice]

Here is an example from my 550X, in this case the Normal and Idle Up pitch curve.

It's difficult to see, but notice point 2 is slightly lower so instead of a straight line from mid to full stick, there is a shallow bow in the pitch curve which has the effect of desensatising the pitch curve a little.
When I am describing this, I liken it to a progressive suspension spring on a race car, the more it compress the harder it get's. In our case the further you move the collective the more pitch you get and the faster it comes in.
This same logic applies to using exponential on the cyclic's and tail rotor channels as well, you can either soften the response between two points or heighten it.

Ian

P.s. Just to add, I take off (and sometimes land if not auto'ing) always in normal mode, it's there to be used and works well. In my case my machines are setup to be softer in normal mode, so I can use this to pop the model off the deck and make sure everything feels ok before hitting the loud pedal (idle Up) and sending it off into a manouver.
In the attachments you'll notice I have reduced the low stick collective pitch to no more than -3 degree's, problem solved with removing unnecassary negative pitch when it is not needed.

[Stuey]

Thanks again for the advice, food for thought. I see Ian has used the shape of the pitch curve to build in expo around the centre point, I use expo on my fixed wing models and also cars to adjust throttle and steering response. The curve is currently programmed as per the manual, so I will check what settings that gives first. Getting it off the ground into a stable hover is job number one!

[coolice]

Thanks again for the advice, food for thought. I see Ian has used the shape of the pitch curve to build in expo around the centre point, I use expo on my fixed wing models and also cars to adjust throttle and steering response. The curve is currently programmed as per the manual, so I will check what settings that gives first. Getting it off the ground into a stable hover is job number one!

Hey Buddy.

You're welcome. As you say it's all good points and will help steer you right.

That's it, spot on with the exponential. In my radio I can assign where I want pitch points to go, hence my point 2 being slightly higher up than the 3/4 stick position. But you can achieve the same effect on the DX6i you have by lowering the 3/4 point by 5 points.
Without EXPO being activated on the pitch curve the line will look like a dot to dot drawing, with it activated the radio smooths out the lines between the 5 points. I'm sure it's there in the pitch (and throttle) curves of the DX6i and it will be a toggle switch to either be on or off. With it turned on you will see the change to the graph.

Keep us posted and any questions fire away.

Ian