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n3 + s900 + e1200 uncontrollable bouncing on take off, crash
761 3 2018-2-3
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sftmthd
lvl.3
United States
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i made the first test flight of a new setup today. previously i was running s900+e1200+wkm. flew fairly smoothly, some vibrations and gps not rock solid but very predictable and controllable. i wasn't happy with the FPV setup, so i upgraded to n3 + lb2 and pretty much set it all up from scratch. motor tests look good, control sticks show full range, center of gravity is dead center front/back and left/right, about 115mm “down” from the N3, which is mounted dead center, on the lower deck. GNSS stalk also mounted dead center on the top deck.

this AM i took it out, fully charged pack, calibrated compass, but with the gimbal (gremsy t3) and camera (nikon d850 + 20mm f/1.8) removed.

it seems like GO 4 wants you to take off in GPS mode, which i have never done before, but i did. motors start in sequence, spin smoothly. i give it a little throttle and it lifts and then immediately bounces back down, hard enough to literally bounce off the ground. it goes up, bounces down. i tried full down throttle to “land” but it just keeps bouncing up. it hopped about 15 feet as i’m trying to kill it and then i just shut down the radio, which shut it off.

so, i’ve obviously made a n00b mistake. i really doubt it’s ground effect with an aircraft this large, and i never experienced that before with the s900. i could reliably fly around a foot if not inches from level ground on ATTI. should i have not taken off in GPS? could the gains be so far out that in GPS it couldn’t maintain altitude and was going down and up, but right at ground level, thus impacting? i couldn’t find any reference to recommended gains with this setup, so i started low, about 2/3 default values for the basic gains.

the only thing unusual about the setup is that the IMU is facing backwards, but it’s set that way in the mounting setup (i quadruple checked..... and it’s not like it went “backwards,” it went violently up and down. in retrospect maybe i should have given it more positive throttle to get high enough to see if it was oscillating up and down, but i really didn’t have control and didn’t want to risk a flyaway or something.

could really use some help here, after two years of flying without a crash or loss of control, now i’m spooked! thankfully i took the gimbal and camera off

2018-2-3
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sftmthd
lvl.3
United States
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for reference, the setup without the camera and gimbal weighs 5.5kg. with the camera and gimbal, 8kg.

it might be too light for the e1200 without the payload?
2018-2-3
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dsenechal
lvl.2
United States
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I don't think it's a case of being too light. I converted my S1000+ to E1200 motors, and never had any such issues, even without a gimbal. Have you checked the gain value settings? They're quite a bit different for the E1200, and maybe they got re-set to default. I actually much preferred the old Wookong controller with a Futaba transmitter. Rock solid. The Go app is really finicky.
2018-4-30
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AgentEddie
lvl.2
Flight distance : 25200 ft

Saint Vincent and the Grenadines
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Hope you get it sorted, sounds like a terrible experience
2018-4-30
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