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Old Nov 06, 2014, 02:21 AM
wow so fly
United States, CA, Palo Alto
Joined Dec 2013
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Question
Trex 250 DFC

I have a question regarding the swash movement on the 250 DFC Plus, I got this heli new RTF but have yet to fly out of paranoia. One of the thing's I've noticed is that when I tilt the heli to the left, the swash briefly responds by tilting to the right for perhaps a millisecond and then appears to level itself. The same behavior occurs vice versa. I'm not too sure if this is a characteristic of DFC/flybarless systems but I just wanted to make sure before I maiden her.
More generally speaking, what are the characteristics of a flybarless heli? as in when I tilt the heli to the right (no stick inputs), should the swashplate tilt to the left and hold left until the heli is level again to keep the heli stable?
Thanks guys!
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Old Nov 06, 2014, 02:33 PM
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United States, OR, Canby
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The flybarless system will tip the swash to counter un-commanded movement. If you tip heli right swash should move left. How quickly it returns to level depends on how you are moving or not moving the heli. It sounds like yours is correct.
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Old Nov 07, 2014, 12:43 AM
wow so fly
United States, CA, Palo Alto
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so when i tilt it and hold it still at an angle, it should level the swash parallel to the body?
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Old Nov 07, 2014, 12:56 AM
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Well off the top of my head I would say if you tip the heli the swash will move opposite and stay there until you return the heli to level. It's not something I really paid attention to but as a preflight you just make sure the swash moves in the correct direction when you move the sticks and when you tip it the swash corrects for the movement. If it does these two things don't over think it just fly it.
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Old Nov 07, 2014, 10:37 AM
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What you're describing is the behavior of FBL systems, like 600bob said. Any direction that you tilt the heli, it should counter in the opposite direction. The swash should remain level with the ground (more or less) when you tilt the heli.
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Old Nov 07, 2014, 11:46 AM
wow so fly
United States, CA, Palo Alto
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What I'm observing is that when I tilt it with no stick inputs, the swash initially angles itself opposite of the direction of tilt but right afterward when I'm still holding the heli at an angle, the swash returns to parallel to the body. Should it still be countering this tilt?
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Old Nov 07, 2014, 12:57 PM
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It depends on how the programmers want it to respond, if that is what it is doing then it is probably normal for that design. The correction to tilt you describe is correct, I would go fly it.
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Old Nov 08, 2014, 02:14 PM
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Quote:
Originally Posted by mrpotatohead2234 View Post
I......when I tilt the heli to the left, the swash briefly responds by tilting to the right for perhaps a millisecond and then appears to level itself.
maybe it has very little stabilization(gain?) dialed in? my heli when i tilt it, the swash tilts the other way and slowly returns to center. maybe yours is set up for aggressive maneuvers..?

zyx-s and 3x1000 both return slowly back to center on mine.
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Old Nov 08, 2014, 02:20 PM
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As a thought a real flybar would probably also return the blade pitch back to the "level position" after a few moments too. A stabilization controller like Fly Mentor would try to keep the swash level with the ground plane.
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Old Nov 09, 2014, 12:28 AM
wow so fly
United States, CA, Palo Alto
Joined Dec 2013
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So how does a flybar system work in contrast to FBL? My flybar heli swashplate does nothing when I tilt the heli (as expected?) is the work done instead by the paddles?
I have the 3g MRS on the plus, wondering if it's anything with that.
Flying Pitcher, when you tilt your heli and observe that behaviour, are you holding the heli at that tilted angle or un-tilting the heli back parallel to the ground? Mine is re-leveling the swash
really fast, not sure if i should be worried about that. When I input stick movements though (on the ground) and center the sticks, it re-levels rather slowly compared to the behaviour mentioned previously(where I tilt the heli). Is this a standard setup?

Thanks guys!
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Old Nov 09, 2014, 01:18 AM
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In a flybar unit you control the swash which in turn controls the flybar, the flybar controls the blade pitch. In a flybarless unit you control the FBL unit, it controls the swash which is connected directly to the blades. The FBL does what the flybar does only electronically with more precision and user adjustability.
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Old Nov 09, 2014, 04:15 PM
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when i tilt my heli and hold it tilted that way, the swashplate countertilts and then slowly crawls back to centered position, even though i keep holding the heli sideways but it does take a few seconds. my FBL is set up to beginner mode too, so it's "softer ride"
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Old Nov 11, 2014, 03:46 AM
wow so fly
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awesome, looks like my heli behaves somewhat the way you guys describe so I guess I'll fly her soon, with training gear though. Thanks guys!
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Old Nov 11, 2014, 08:10 AM
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good luck, man. take it easy as she's a little girl, but with lots of energy
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Old Nov 11, 2014, 12:20 PM
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Tucson, Az
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How much experience do you have flying c/p helis ? Not trying to be prying. Being real nervous keeps you on toes but could also make you do wrong thing at bad time. This is a nice heli and sounds like its ready to go. Is the flyer ? Like its been said take it slow. My friend has one and been a very good bird for him. good luck
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