Unstable after prop increase - need assist

ArduCopter Copter 4.4
1

Greetings,

First time builder/pilot here. I have recently built an S500 frame drone with a Pixchawk1 FC and flyable but undersized drive system (it was before I heard about E-Calc). I’ve learned alot but am still running into things that are beyond my knowledge, so help is very much appreciated.

I am in the process of updating the motors and battery in the search for more suitable flight times, so in the meantime increased the (slowfly) prop size from 9" to 12". (It flew nicely on the 9" but flight times on a 3A 3S batt were 6 mins (or less) minutes at hover).

This is what E-calc says about the current set up:

S500 w-12 inch props old motors
S500 w-12 inch props old motors1264×925 205 KB

I balanced and installed the 12" props and re-entered the appropriate information in ‘Initial Tune Parameters’ and saved them. First flight was a little twitchy. Following the directions in the Initial Tuning Flight in the wiki I reduced the ATC_RAT_PIT & RLL settings but…it’s still very unstable (I should point out I reduced them by 25%, not 50%, BUT today it seemed even less stable than before the reduction). Today’s flights (in a very slight breeze - barely enough to move leaves, but not branches) it was all over the place, almost unflyable in ‘Stable’ mode. I switched to AltHold to see if that would help and it went right to the ground from about 6 feet. (AltHold always worked fine with the 9" props).

It will be a long moment before I can read the logs but I offer them up if anyone has any suggestions…? Thanks in advance!

These are the .bin files of the last two flights:

Curtis

2

without going over the data too much, I’d guess that you want a 4S battery, 5Ahr or so, and the master airscrew 12 inch MR props.
Is that an all-plastic frame with flexibility? Or is it very stiff with carbon fibre tube arms?

3

Hey Shawn,

Yes, it’s the rigid frame with carbon rods. Of course, it’s a heavy frame, too… Current motors are limited to 3S, but those, as well as the battery, are getting upgraded

According to E-calc trying different props had little or no effect…? Seems the point of reduced return (even with the upgrades) is around 4500mAh 4S on the battery, then time aloft starts getting on the back side of the curve.

But what’s bothering me now is the instability. I use 50C batteries and they should be able to deliver whatever the motors demand and I’m not doing anything more demanding that hovering so far.

Props are the same make & model, just longer. They’ve been balanced, have at least an inch tip clearance and clearance from frame plates. Donno…

This is a trainer and teaching first drone, but I would at least like to get it to a point that I can do an Auto tune regimen on it and fly some figure-8s.

Thanks for taking the time to respond.

Curtis