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250 Class Electric Helicopters 250 Class Electric Helicopters manufactured by Align, Tarot, SYMA, Airhog, Chaos, HK and similar. |
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11-09-2014, 04:57 PM | #1 (permalink) |
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Join Date: Feb 2014
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tilt on take off
Hey guys, I have a trex 250 dfc that is tilting to the left on take off, I correct it with a little cyclic input and once I get it in the air it is fine, what could be causing this ? The only thing I was wondering is if the balance is off ? Cause the left side of the Heli has 2 servo's and it has the beastx, could that be causing the issue , maybe I should move it to the right side ?
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11-09-2014, 05:52 PM | #2 (permalink) |
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Join Date: Nov 2014
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This is a normal tendency for compensating for the thrust produced by the anti-torque tail rotor. Assuming no cross wind and the 250 is set up properly.
Opposing (in this case left) cyclic input compensates for the tail rotor thrust and puts the helo in a left-wing down potion. |
11-09-2014, 06:50 PM | #3 (permalink) |
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I find that my flybarless heli doesn't like to lift off the ground slowly..... Seems to do all types of strange things.... Once it off the ground its fine .. that's say 2 or 3 foot off the ground. It could be the FBL controller if your slowly lifting off.
Just a thought. You may want to check your swash level at mid stick...... could be that your FBL controller is having to compensate for the out of wack swash... Just a thought.
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11-09-2014, 09:11 PM | #4 (permalink) |
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My thought is that it could be a bent main and/or feathering shaft and/or head block, imbalanced blades, incorrect blade tracking, your blades aren't straight until they sling out completely or the blade bolts are too tight, or you could have an unseen vibration issue.
Any number of these could be the cause, so you'd have to systematically check each one to ensure trueness, but the weight being on one side won't cause it to pull like that unless it's grossly out of balance (although not a bad guess).
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Tim KBDD TEAM PILOT --Si vis pacem, para bellum-- |
11-10-2014, 12:41 AM | #5 (permalink) |
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Could be the weight if you have a lot on that side, could also be the swash not level.
Have you done a CoG check? I just checked mine, I've got a servo mounted on the boom and ended up swapping that to the other side. Just that small change has it behaving better, so its definitely worth checking the balance.
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Helis: Oxy 4 Max (day + night), Gaui X3 380, Oxy2 FE 215, Oxy2 Sport 190 Radio & FBL: Spartan Vortex, MSH Brain, Jeti DS-14, Spektrum DX8G2 Sims: RealFlight & AccuRC |
11-10-2014, 02:56 AM | #6 (permalink) |
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Location: Aberdeen, UK
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As per the first reply... Thrust from the tail rotor will tend to make a heli tip to the left when on the ground and just before lifting off (assuming conventional clockwise rotation main rotor). The tendancy will always be there but i guess you could make sure the heli isnt weighted on the left side as that would serve to compound the effect.
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11-10-2014, 05:43 AM | #7 (permalink) |
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I am not 100% here but I feel like if I were not to aply the cyclic to correct the lean to the left on takeoff that it may tip all the way over, I am not sure but don't really want to find out either and thats what makes it so difficult, I am pretty sure everything in the setup is good as I went through all the beastx setup menus twice and put a swash leveler on it in menu G to make sure the swash was good and level, maybe if theres enough wiring I will just try putting the beastx on the opposite side to make sure its not the weight issue and at least try to eliminate that as a problem or not, I have not done a cog check, how do you guys do a cog check? what is the most accurate way of doing it ?
Thanks so far for your suggestions, if you have any more keep em coming |
11-10-2014, 06:05 AM | #8 (permalink) |
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Location: Aberdeen, UK
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CG check is really only normally done for fore/aft balance, not side to side. Side to side normally looks after itself.
You just huld the heli by the main rotors with the blades vertical, the main shaft horizontal and the heli fuselage horizontal, and see if the heli want to tip nose or tail down.
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11-10-2014, 06:14 AM | #9 (permalink) |
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The best way to COG check IMO is to loop a string or wire under the head block or the gap between the grips and the head block, put the blades inline with the machine and pick it up like a puppet. It will tilt one way or the other if your COG is off. You can do the same for your fore/aft COG by putting the blades out to the sides and checking the same way.
You can do an even quicker, but much less accurate test by picking it up with your fingers using the same pickup point, but it may skew the results if you're trying to get it spot-on (but it's a good rough idea of where the COG sits). You could also use some sticks or other means of getting under the head block that will fulcrum under the weight and show any imbalance. I also like to remove the blades when doing a COG check because if they're not perfectly straight out they can throw off the readings. I ended up placing my AR7200 inside the frames. It's a bit of a tight squeeze, but it doesn't effect it at all in flight. Matter of fact, it tracks better than my 450 through big loops, so I know it's perfectly straight in the frames. Another thought occured to me as well. How tight are yoru ball links? Some of the effect you're seeing on your bird could be the result of tight links and rosonance through the frame as the machine sits on the ground. If you pop it up quickly, does it fly really smoothly, or does it still jerk around a lot or not respond to fine control?
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Tim KBDD TEAM PILOT --Si vis pacem, para bellum-- |
11-10-2014, 09:06 AM | #10 (permalink) |
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I have only been hovering it yet, but once its in the air it does not try to lean to the left
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11-10-2014, 09:15 AM | #11 (permalink) |
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All fbl units act up on the ground .. vibration from skids on the ground and ground effects ... smaller the bird bigger the effect . Get it in the air fast ... with a pop ... dont play around one the ground .... its a bird not a car :-D it will be happiest flying
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11-10-2014, 04:02 PM | #12 (permalink) |
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The problem with the 250 is that it is so small that trying to take off a grassy surface is really hard. I don't know if that is what you have or not. But as VD2021 says when you begin to lift off the heading hold of the tail will start to try and hold the nose heading. If there is anything to snag on the skids, the tail thrust pushing the hell to the left may cause the hell to tip. Of course the fbl system will try to prevent that. Usually the best advice is to fly off as level and flat a surface as possible, and with the 250 at least, don't dawdle on the ground too long. It is meant to fly like a bird, no hop like a grasshopper
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11-10-2014, 04:16 PM | #13 (permalink) |
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To a large extent that behaviour depends on the FBL. My Spartan will sit happily on concrete or grass and can take off as slowly as I like. I can even pull the skids out of tangled grass without fear of tip over.
I'm curious to see how the OP fares after adjusting the CoG. I'm also wondering where the FBL is mounted to be on a side like that. OP, mind sharing a picture of your setup? Also, does the heli hover ok hands off while in the air?
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11-10-2014, 06:07 PM | #14 (permalink) | |
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Quote:
I am taking off from concrete, I have never had any problems with my bigger birds being able to take off slow and they all have the ar7200 beastx as well, no it will not hover hands off, none of my heli's will just hover hands off, maybe I don't have any of them setup correctly ? I am still a newbie, I have been dabling in heli's since about april or may of this spring, I always use the swashplate leveler and go through my beastx setup but I have never really had anyone that's been doing it for awhile go through and do it with me. |
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11-11-2014, 01:13 AM | #15 (permalink) |
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Hmm, the FBL will be adding a lot of weight to that side, and the stock setup is left side heavy anyway.
You really should be able to hover hands off for 5-10s with a good mechanical setup. Mine starts to drift right after 3-4 seconds, but even in my back garden I can fly it hands off for nearly 10s. My setup isn't finished yet, so its drifting quite fast by the end, but that's what you want to aim for. If its tipping to one side constantly during flight I think you can use subtrim to tilt the swash a little the other way.
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Helis: Oxy 4 Max (day + night), Gaui X3 380, Oxy2 FE 215, Oxy2 Sport 190 Radio & FBL: Spartan Vortex, MSH Brain, Jeti DS-14, Spektrum DX8G2 Sims: RealFlight & AccuRC |
11-11-2014, 02:22 AM | #16 (permalink) |
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Take it up hover it ... let go of ciclic stick ... if you have a drift go one turn on each aposing alerion pitch link to counter side to side drift .... then see if that also helps with the tipping issue
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11-11-2014, 06:26 AM | #17 (permalink) |
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That could be making the problem worse. If it has a mechanical or COG error then tilting the swash to counter it is putting a band-aid on it. When you go inverted it will cause the heli to drift because of the differential in the mechanical setups is still asymmetrical. It was a logical guess, so I hope it doesn't come across that I was slam-dunking your idea. But I wanted to point out the results if he was to try it (in other words, I've already tried the same thing and hoping to save other people from unnecessary mistakes).
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Tim KBDD TEAM PILOT --Si vis pacem, para bellum-- |
11-11-2014, 10:07 PM | #18 (permalink) |
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I know of two fbl many factors that say this is the correct method ... swash square to main shaft to start then adj accordingly to compensate to left right cg ... equally amounts on each side ...
From the helicomand crew ... |
11-11-2014, 10:12 PM | #19 (permalink) |
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Edit ... that doesn't mean u can strap a brick to the side and have the swash at a 45 degree angel to compensate ..
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11-11-2014, 11:24 PM | #20 (permalink) |
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Well, unless I did some studying to understand what they're implying by that I can only tell you from personal experience that if your bird is drifting in any direction then something is most likely off on the mechanics. The reason I say that is by and large, the heaviest components you put on almost any machine aren't heavy enough to throw it off by much. Batteries if course are another animal, but this is the port/starboard COG in question and the FBL unit only weighs, what? 20-30g? I'm not sure that would be enough to throw it off.
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