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ccpmheli -> RE: E-SKY LAMA 2 THREAD (2/5/2007 9:54:04 AM)
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Hello vega2614, I have noticed the strang behavior you mentioned a couple of times., Once I was a little panicy and pulled hard back on the cyclic to avoid an obstacle, as the heli was transitioning from forward to my rearward, it just seems the whole thing quit flying, turned on it's right side and hit the ground. No damage to the blades or flybar. The second time was in my living room, flying close to the floor and I was getting kind of close to where one of the cats was sleeping, again, I pulled hard(but not crazy hard) for rearward cyclic, again the heli just quit flying and flopped over on its right side. Its almost like the rotor blades are stalling for some reason, because the heli is going along fine(motors spinning, blades turning), and then over control pushes the blades past their stall angle, they stall, it falls. I would think these low speed airfoils would be sensitive to a high angle of attack. I guess there could always be a control problem with the 4-N-1 or TX, but to me, it sounds like everything should sound. You can hear a glitch in my Esky HB. It has only happened a few times, but you could hear the motor(s) cut off and cut on when it happened(kind of like the airplanes in movies when they are having engine trouble...AnnnN.....AnNn.AnnNN), even though it only lost 6" of altitude, before recovering. From my limited experiences with coaxial rotored helis, they have very little control authority on the cyclic, considerably less than even a fixed-pitch standard heli. Though that makes them easier to manage for the beginner, it takes away the maneuverability, and significantly reduces the ability to get out of sticky situations. As far as your trim comments go, I know that the smaller area I fly it in, the quicker it becomes effected by it's own turbulence, and the more severe the effect. I don't know what is happening in your case, but I thought I would say that. You said you were breaking the center shaft, I have not broken one yet, including a crash from about 10 feet. However, I have broken 3 of the bottom blades. One rule I have, is if I know I am going to crash, I chop the throttle immediately. I realize this is harder to do when you are flying "edge of the envelope" maneuvers. I do not believe it is possible for the stabiliser bar and the upper set of blades to meet as long as they are attached, as they are turning on the same shaft. I also do not believe either of them could contact the lower blades(they would have to flex a whole bunch)I have heard people report that they think their stab bar came off in flight, that would certainly cause a loss of control, but in both of the cases I mentioned above, my stab bar was in place. Good Luck.
Just wanted to add this comment. These helis fly with a relatively low rotor speed, that coupled with the ease of the blades to swing on their mounting bolt(lead-lag), and their high drag airfoils, might be contributing to the problem. I theorize, that when a sudden increase in throttle occurs with an extreme control input, the advancining blades lag on the acceleration of the shafts/rotor heads, that coupled with the low speed, high drag airfoil casues the blade to lag even farther, leaving the blades at such an extreme angle off of center, that the blades quits supporting their side of the rotor disc, as the effective length of the advancing blades is reduced. Also A stalling of the advancing blades would be likely.
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