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greekpilot · 08-14-2015, 09:48 AM

Dear friends,
among other helis i have a 550 gaui stretched, on 520mm blades.
I have recently rebuilt it with carbon frame , fbl head.
i am still a newbie slowly progressing to some mild 3d, and the problem i have with this chopper, and not with any other that i own is the following.

When i seem to stress the cyclic a little bit (flips, rolls, rainbows), the motor seems to cut off for a split sec, then spools up back to speed gradually, like from a soft start. I have control on cyclic and tail the whole time, and it doesnt sound like bogging. The same thing happens no matter what headspeed, lipo, gearing, esc setings, so i am convinced that this is not a matter of motor (sk3 1300kv 1500w) or soldering, since at high motor loads (sharp climbs) the motor is up to the challenge, no sweat.
Now i am sure the esc and bec i am using are not up to the task (turnigy 85amp with 5a sbec) but i cannot determine if this is a voltage drop related rx or kbar reset, brown out, loss of signal failsafe or what.
Unfortunately i am away from home and will be for the next month or so so i cannot remember exactly the servos that i have (futaba all around, but analog 7-8kg on cyclic, and futaba digital on tail.)
I run the heli on a 6s setup, 35c 3300mah, and mini yellow kbar.

Now i dont want to go out all the way and change everything on the heli, since i am not flying it at all and i am on the process of a new g700, i just want to figure out what is wrong and address it so that i can sport fly it with some very mild 3d in the mix.
So my question is, does this situation sound really familiar to any of you guys and what would be a possible and cheap solution for this.

Thanks and have a nice day.

jhamel · 08-15-2015, 10:29 AM

My guess is that the BEC is not able to keep up with the current needed and it leads to a low voltage brownout situation. When the receiver browns out, there is no throttle signal, so the motor would stop running. The brownout may just cause a quick reset of the FBL unit, so you may not notice much issues with the servos, but the ESC may soft start the motor.

You may just need a more robust BEC or a battery.

greekpilot · 08-15-2015, 10:38 AM

Wouldn't the loss of signal occur on all channels though? Would it just be for the esc? The thing is that I certainly do not notice any twitching or loss of control on cyclic, at least no more than a motor cutting out would justify... That is what really puzzles me..

jhamel · 08-15-2015, 10:49 AM

If the reset happens within a fraction of a second, you may not notice any glitching of the servos, but the ESC will have noticed the loss of signal and would just go into soft start once it receives signal again.

greekpilot · 08-15-2015, 10:53 AM

Yes that sounds very reasonable. So in my case that I will not be stressing the heli much, you think an rx capacitor could patch things up a bit?

jhamel · 08-15-2015, 10:55 AM

The capacitor may improve things, but it may also be a band-aid covering the real problem.

greekpilot · 08-15-2015, 11:05 AM

Oh yes I totally agree, it just that this is going to be my -one a month flight- bird until I eventually sell it, so I don't want to go into more trouble than that since I don't have a spare bec or rx pack laying around now. Thank you very much for your opinion curmudgeon, I appreciate it.

08-14-2015, 09:48 AM	#1 (permalink)
greekpilot Registered Users Join Date: Apr 2014	Brownout, rx reset or what?? Help Dear friends, among other helis i have a 550 gaui stretched, on 520mm blades. I have recently rebuilt it with carbon frame , fbl head. i am still a newbie slowly progressing to some mild 3d, and the problem i have with this chopper, and not with any other that i own is the following. When i seem to stress the cyclic a little bit (flips, rolls, rainbows), the motor seems to cut off for a split sec, then spools up back to speed gradually, like from a soft start. I have control on cyclic and tail the whole time, and it doesnt sound like bogging. The same thing happens no matter what headspeed, lipo, gearing, esc setings, so i am convinced that this is not a matter of motor (sk3 1300kv 1500w) or soldering, since at high motor loads (sharp climbs) the motor is up to the challenge, no sweat. Now i am sure the esc and bec i am using are not up to the task (turnigy 85amp with 5a sbec) but i cannot determine if this is a voltage drop related rx or kbar reset, brown out, loss of signal failsafe or what. Unfortunately i am away from home and will be for the next month or so so i cannot remember exactly the servos that i have (futaba all around, but analog 7-8kg on cyclic, and futaba digital on tail.) I run the heli on a 6s setup, 35c 3300mah, and mini yellow kbar. Now i dont want to go out all the way and change everything on the heli, since i am not flying it at all and i am on the process of a new g700, i just want to figure out what is wrong and address it so that i can sport fly it with some very mild 3d in the mix. So my question is, does this situation sound really familiar to any of you guys and what would be a possible and cheap solution for this. Thanks and have a nice day.

08-15-2015, 10:29 AM	#2 (permalink)
jhamel Registered Users Join Date: Mar 2011 Location: West Seattle, WA, USA	My guess is that the BEC is not able to keep up with the current needed and it leads to a low voltage brownout situation. When the receiver browns out, there is no throttle signal, so the motor would stop running. The brownout may just cause a quick reset of the FBL unit, so you may not notice much issues with the servos, but the ESC may soft start the motor. You may just need a more robust BEC or a battery. __________________ 14S Specter 700 V2 NME/Tron 7/Kraken; 8S Tron Dnamic; 7S Kraken 580; 6S Buddy 380 KSE VBCE/Neo/EVO, Jeti/Spirit, YGE "T" ESCs; LiFePO4 field charging batteries Sims on Mac: Heli-X, neXt, AccuRC, Phoenix, AeroFly RC7 Ultimate Amain Team Pilot

08-15-2015, 10:49 AM	#4 (permalink)
jhamel Registered Users Join Date: Mar 2011 Location: West Seattle, WA, USA	If the reset happens within a fraction of a second, you may not notice any glitching of the servos, but the ESC will have noticed the loss of signal and would just go into soft start once it receives signal again. __________________ 14S Specter 700 V2 NME/Tron 7/Kraken; 8S Tron Dnamic; 7S Kraken 580; 6S Buddy 380 KSE VBCE/Neo/EVO, Jeti/Spirit, YGE "T" ESCs; LiFePO4 field charging batteries Sims on Mac: Heli-X, neXt, AccuRC, Phoenix, AeroFly RC7 Ultimate Amain Team Pilot

08-15-2015, 10:55 AM	#6 (permalink)
jhamel Registered Users Join Date: Mar 2011 Location: West Seattle, WA, USA	The capacitor may improve things, but it may also be a band-aid covering the real problem. __________________ 14S Specter 700 V2 NME/Tron 7/Kraken; 8S Tron Dnamic; 7S Kraken 580; 6S Buddy 380 KSE VBCE/Neo/EVO, Jeti/Spirit, YGE "T" ESCs; LiFePO4 field charging batteries Sims on Mac: Heli-X, neXt, AccuRC, Phoenix, AeroFly RC7 Ultimate Amain Team Pilot

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08-15-2015, 10:38 AM	#3 (permalink)
greekpilot Registered Users Thread Starter Join Date: Apr 2014	Wouldn't the loss of signal occur on all channels though? Would it just be for the esc? The thing is that I certainly do not notice any twitching or loss of control on cyclic, at least no more than a motor cutting out would justify... That is what really puzzles me..

08-15-2015, 10:53 AM	#5 (permalink)
greekpilot Registered Users Thread Starter Join Date: Apr 2014	Yes that sounds very reasonable. So in my case that I will not be stressing the heli much, you think an rx capacitor could patch things up a bit?

08-15-2015, 11:05 AM	#7 (permalink)
greekpilot Registered Users Thread Starter Join Date: Apr 2014	Oh yes I totally agree, it just that this is going to be my -one a month flight- bird until I eventually sell it, so I don't want to go into more trouble than that since I don't have a spare bec or rx pack laying around now. Thank you very much for your opinion curmudgeon, I appreciate it.

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