General Question Regarding Inputs - RC Groups
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Nov 05, 2017, 01:55 PM
Registered User
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General Question Regarding Inputs


I am new to CP flying, got a Nano CP S from the wife, she didn't know how difficult it would be. I do have some fixed pitch experience.

I am mind boggled at just how out of control this thing is and thinking I have an issue. As soon as I get it of the ground it takes off like crazy (maybe 2 out of 15 flights it actually levels out and can hover). I have found many threads that seem similar, but no fix or absolute answer.

Question: As a general rule, does swash plate movement follow stick movement? What I mean is this, if I move the stick to +100% forward, then back to +50%, should the plate move with the stick back to +50%? Or do I have to apply negative stick (ie -50%) to get the plate to move in a reverse direction?

Essentially, I am finding that the plate does not want to return to level when the right stick is in it's center position. Is this correct? Could it be a setting on my DX6e? It does appear to find level when I initiate it on a level surface.

Thanks in advance, sorry for the noob question.
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Nov 06, 2017, 01:03 AM
Grumpy old git.. Who me?
JetPlaneFlyer's Avatar
No, the swash movement on a flybarless heli like the CP S does not directly follow stick movement. How you describe the movement of yours sounds perfectly normal.

When spooling and while the heli is on the ground try to minimise any stick input. Lift off quickly as soon as the rotors are up to speed.
Nov 10, 2017, 04:19 PM
Registered User
Thanks JPF.

To me it is odd (because it is new) to have to apply a negative input to move a positive input back to center. Just for my understanding, can someone help me understand why they don't return to center with the stick?
Nov 11, 2017, 10:47 AM
Grumpy old git.. Who me?
JetPlaneFlyer's Avatar
With a flybarless system you arent directly controlling the servos. When you move the stick you are sending an instruction to the FBL controller to yaw, roll or pitch according to whatever stick input you make.

So lets say you move the aileron stick to the right. The FBL sees that as a commend to roll to the right at a rate (in degrees per second) that's proportional to how far you moved the stick. How far the heli rolls is equal to how far you move the stick and how long you keep the stick over.

Lets say you moved the stick enough to give a 90 degrees per second roll rate. The FBL will now move the servos by an amount sufficient to achieve a 90 degrees per second roll (the FBL detects the roll rate using it's roll gyro). How far the heli rolls is controlled by how far you move the stick and how long you hold it over, so if you moved the stick for a 90 deg per second roll and you held it for 2 seconds before cantering, the heli would roll 180 degrees (to inverted).

So that's how it works when the heli is flying and that's all good. When the heli is on the ground there is a problem because the heli cant roll (or pitch) because it's sat firmly on the ground. When you command that same 180 degree roll on the ground the FBL will move the servos over and will keep them over waiting for the gyro to detect a roll. Only if you give it an opposite commend to roll back 180 degrees in the opposite direction (back to upright) will the FBL think it's done it's job and put the servos back to neutral.

This is why in the early days of FBL helis had a habit of rolling over on the ground (the Align 3GX was well know for it). More modern units have lessened the effect but it's still best to minimise input when the heli is on the ground.
Last edited by JetPlaneFlyer; Nov 13, 2017 at 01:48 PM.
Nov 12, 2017, 05:50 PM
Registered User
Very informative JPF, thank you!
Nov 13, 2017, 07:19 AM
Rotor Controller
CaptJac's Avatar
A micro CP helicopter is a handful for any beginner and it takes hundreds of hours and dedicated practice to develop the "muscle memory" that allows us to move the sticks without having to "think" about them. We don't have enough time to sort it all out and by the time we do it is is too late and our helicopter is flying us instead of we flying them. If your wife is serious about learning to fly then GOOD for her and a BIG atta-girl !! From the training of 100's of students in the Phoenix Simulator Flight School comes the recommendation for learning orientation a different flying platform like a miro quad is 100 times more stable than a CP micro heli. Good luck and have a great flight!

captJac
Nov 18, 2017, 03:27 PM
the great Gassif´er
Quote:
Originally Posted by rolsen99
Thanks JPF.

To me it is odd (because it is new) to have to apply a negative input to move a positive input back to center. Just for my understanding, can someone help me understand why they don't return to center with the stick?
Just for some additional "visualisation" (JPF's explanation was perfect, but not all people can visualize things like rollrate), think of it as driving a car and changing lanes: you turn the wheel a bit to the left, then come to neutral, and your car is slanted and will cross over to the next lane (parallel: the helicopter will be tilted and start to move in that direction).
Unless you want to end up in the barrier, you need to give it a bit right steer to get the car lined up again with the direction of the road you're on.

It is not a 100% analogy, but when I am instructing, I find this analogy helps beginners understand why they need to do this "double & reversed imput".
These two stickmovements are, especially when you are learning to fly, basically always mirror images of each other: you give a short imput to the left and a short time later you'll find that you need to give the same imput for the same duration, in the opposite direction.
Nov 18, 2017, 05:21 PM
Grumpy old git.. Who me?
JetPlaneFlyer's Avatar
Brutus, that's a really good analogy!


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